Once you've got your CCNA, you're ready to move on to the next level, the Professional certifications. For years, Cisco had one Professional certification, the Cisco Certified Network Professional (CCNP) certification. Over time, Cisco has expanded this level of certifications to include the Cisco Certified Security Professional (CCSP) and Cisco Certified Voice Professional (CCVP).
With security and voice being the two most rapidly expanding areas of today's networks, some new CCNAs consider going after the CCSP or CCVP without first adding the CCNP to their resume.
While it's temping to hurry up and get a Cisco security or voice certification, the best thing you can do for your networking career is achieve your CCNP certification first, then decide on the CCVP or CCSP.
Why? Because the CCNA is just the tip of a very large iceberg when it comes to routing and switching. It's a very important accomplishment, and the CCNA is indeed the foundation of your networking career, but you need to add on to that level of understanding routing and switching before moving on to more specialized areas.
Two examples are OSPF and BGP. You learn about the theory of OSPF and some basic and intermediate configurations of that protocol in your CCNA studies, but the knowledge you acquire of OSPF in your CCNP studies is invaluable. As for BGP, there is no BGP in the CCNA curriculum, but it is a great idea to have some BGP knowledge in today's networks. It's also good for your career.
I know it is a huge temptation to go after the security and voice certifications while not paying attention to the CCNP. Do yourself a huge favor and add the tremendous amount of routing and switching knowledge needed for the CCNP to your knowledgebase, and you can then move on to the CCSP or CCVP. Even better, you'll be better prepared to climb the biggest certification mountain around - the CCIE!
Showing posts with label icnd. Show all posts
Showing posts with label icnd. Show all posts
Saturday, December 27, 2008
Tips On Buying A Cisco CCNA / CCNP Home Lab Kit
Buying a CCNA / CCNP home lab is the best way to be totally prepared for your Cisco exams. Most home labs are put together one router or switch at a time, but many CCNA / CCNP candidates prefer to buy kits where you get multiple routers and switches, along with all the cables and other connection devices you'll need.
While this is a good idea, keep a few things in mind when purchasing Cisco home lab kits.
Don't buy anything you don't need. The problem is that when you're first starting out with your Cisco home lab, you don't know everything that you need. (I sure didn't!) Keep in mind that you only need one transceiver per AUI port on a Cisco router, so if you're getting routers with two AUI ports in all, you don't need five transceivers in the kit. It doesn't hurt to have one spare, but three is a little too much.
More importantly, don't buy kits with old CCNA or CCNP study guides included. I've seen kits with books that were three years old and were of no use to the candidate. If you see a kit that looks good but includes books or manuals you just don't want, ask the vendor for a price that doesn't include the books. It never hurts to ask.
Watch the IOS version. Unless you've got access to IOS upgrades, you'll be working with the IOS version that's on the routers and switches when you buy the kit for a while. You don't necessarily need the latest and greatest IOS version for CCNA study, but don't buy routers with IOS versions beginning with "10" unless you have an IOS to upgrade them with. (And make sure the routers have enough memory to handle the IOS you plan on putting on them.)
Purchasing a Cisco CCNA / CCNP Home Lab is one of the best investments in your career that you will ever make. Exercise just a bit of caution when purchasing your kit, and you'll be on your way to true Cisco success, in the exam room and on your network!
While this is a good idea, keep a few things in mind when purchasing Cisco home lab kits.
Don't buy anything you don't need. The problem is that when you're first starting out with your Cisco home lab, you don't know everything that you need. (I sure didn't!) Keep in mind that you only need one transceiver per AUI port on a Cisco router, so if you're getting routers with two AUI ports in all, you don't need five transceivers in the kit. It doesn't hurt to have one spare, but three is a little too much.
More importantly, don't buy kits with old CCNA or CCNP study guides included. I've seen kits with books that were three years old and were of no use to the candidate. If you see a kit that looks good but includes books or manuals you just don't want, ask the vendor for a price that doesn't include the books. It never hurts to ask.
Watch the IOS version. Unless you've got access to IOS upgrades, you'll be working with the IOS version that's on the routers and switches when you buy the kit for a while. You don't necessarily need the latest and greatest IOS version for CCNA study, but don't buy routers with IOS versions beginning with "10" unless you have an IOS to upgrade them with. (And make sure the routers have enough memory to handle the IOS you plan on putting on them.)
Purchasing a Cisco CCNA / CCNP Home Lab is one of the best investments in your career that you will ever make. Exercise just a bit of caution when purchasing your kit, and you'll be on your way to true Cisco success, in the exam room and on your network!
Passing Your CCNA and CCNP: Configuring And Troubleshooting Router-On-A-Stick
For CCNA and CCNP candidates, it's hard not to laugh the first time you hear the phrase "router on a stick". Let's face it, that's a pretty silly term. But as those who have passed the CCNA and CCNP exams know, this is a vital exam topic that you must know how to configure and troubleshoot.
Basic Cisco theory states that for hosts in different VLANs to communicate, a Layer 3 device must be involved to handle the routing between the VLANs. That device is a router, and there are special considerations that must be taken into account for both the physical router itself and the configuration you'll be writing.
The router will be connected to a switch via a FastEthernet port (or higher). The router port cannot be a regular Ethernet port, since the router port will need the ability to send and receive data at the same time.
The configuration of the interface is where things get interesting. Let's say we have two VLANs that will be using router-on-a-stick to communicate.
Here is the VLAN information:
VLAN 20: 20.20.20.0 /24
VLAN 40: 40.40.40.0 /24
The port on the switch that will be connected to the router's FastEthernet port must be in trunking mode, and you must know the trunking protocol in use. We'll go with the Cisco-proprietary ISL here.
The physical FE port on the router will not have an IP address. The use of router-on-a-stick mandates the use of logical subinterfaces. While we don't have to use the VLAN numbers for the subinterface numbers, I've found this helps you keep the interfaces straight. One subinterface must be given an IP address in VLAN 20, and the other will have an IP address in VLAN 40.
After creating subinterfaces fast 0.20 and fast 0.40, the config looks like this:
interface fastethernet0
no ip address
interface FastEthernet 0.20
ip address 20.20.20.1 255.255.255.0
interface FastEthernet 0.40
ip address 40.40.40.1 255.255.255.0
Believe it or not, you're almost done! Now we need the encapsulation statement under each subinterface. The subinterface statement must reflect both the VLAN number and the encapsulation type being used. When we're finished, the config would look like this:
interface fastethernet0
no ip address
interface FastEthernet 0.20
ip address 20.20.20.1 255.255.255.0
encapsulation isl 20
interface FastEthernet 0.40
ip address 40.40.40.1 255.255.255.0
encapsulation isl 40
And that's it! Your hosts in VLAN 20 should now be able to communicate with hosts in VLAN 40, and vice versa.
A couple of final troubleshooting points - the most common error with router-on-a-stick is to put the wrong vlan number in the encapsulation statement. Also, make sure you have configured the router's IP address in VLAN 20 as the default gateway for hosts in VLAN 20, and do the same for VLAN 40.
I hope you've enjoyed this look at router-on-a-stick. While the name may get a chuckle out of you, it's still used in quite a few networks out there, and knowing how to configure and troubleshoot it will get you that much closer to earning your CCNA and CCNP.
Basic Cisco theory states that for hosts in different VLANs to communicate, a Layer 3 device must be involved to handle the routing between the VLANs. That device is a router, and there are special considerations that must be taken into account for both the physical router itself and the configuration you'll be writing.
The router will be connected to a switch via a FastEthernet port (or higher). The router port cannot be a regular Ethernet port, since the router port will need the ability to send and receive data at the same time.
The configuration of the interface is where things get interesting. Let's say we have two VLANs that will be using router-on-a-stick to communicate.
Here is the VLAN information:
VLAN 20: 20.20.20.0 /24
VLAN 40: 40.40.40.0 /24
The port on the switch that will be connected to the router's FastEthernet port must be in trunking mode, and you must know the trunking protocol in use. We'll go with the Cisco-proprietary ISL here.
The physical FE port on the router will not have an IP address. The use of router-on-a-stick mandates the use of logical subinterfaces. While we don't have to use the VLAN numbers for the subinterface numbers, I've found this helps you keep the interfaces straight. One subinterface must be given an IP address in VLAN 20, and the other will have an IP address in VLAN 40.
After creating subinterfaces fast 0.20 and fast 0.40, the config looks like this:
interface fastethernet0
no ip address
interface FastEthernet 0.20
ip address 20.20.20.1 255.255.255.0
interface FastEthernet 0.40
ip address 40.40.40.1 255.255.255.0
Believe it or not, you're almost done! Now we need the encapsulation statement under each subinterface. The subinterface statement must reflect both the VLAN number and the encapsulation type being used. When we're finished, the config would look like this:
interface fastethernet0
no ip address
interface FastEthernet 0.20
ip address 20.20.20.1 255.255.255.0
encapsulation isl 20
interface FastEthernet 0.40
ip address 40.40.40.1 255.255.255.0
encapsulation isl 40
And that's it! Your hosts in VLAN 20 should now be able to communicate with hosts in VLAN 40, and vice versa.
A couple of final troubleshooting points - the most common error with router-on-a-stick is to put the wrong vlan number in the encapsulation statement. Also, make sure you have configured the router's IP address in VLAN 20 as the default gateway for hosts in VLAN 20, and do the same for VLAN 40.
I hope you've enjoyed this look at router-on-a-stick. While the name may get a chuckle out of you, it's still used in quite a few networks out there, and knowing how to configure and troubleshoot it will get you that much closer to earning your CCNA and CCNP.
Passing The Cisco CCNA Exam: An Illustrated Guide To Router Modes
When you're getting started on your CCNA studies, learning the different router modes is key to passing your Intro and ICND exams. But keeping those modes straight can be very difficult. (At least it was for me!) Let's take a look at the various router modes you'll need to know about to pass your CCNA, and use IOS Help to illustrate the different uses of each mode.
The first mode you'll see on a router (if the person before you logged off as they should have) is user exec mode. This is also the default mode a user is placed into when using Telnet to connect to a router. The prompt will look like this:
R1>
You can't write or add to a configuration in this mode, but you can run quite a few show commands. This is a good mode to have users in who need to see the configuration, but shouldn't be allowed to change it.
To get to the next level, type enable at the user exec prompt:
R1>enable
R1#
Notice that the prompt changed. This mode has two names, the official one being privileged exec mode. It's more commonly referred to as enable mode, since "enable" is what you type to get into this mode.
This mode gives you more options for show and other commands, but you still can't configure anything. To configure global commands, use "configure terminal", or "conf t", to enter global configuration mode.
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#
The prompt has changed again, and now global configuration commands such as hostname and no ip domain-lookup can be entered.
From here, you've got a lot of options, but we'll look at three you need to know for your CCNA exams. To apply configuration commands to an interface, enter interface configuration mode, as shown here:
R1(config)#interface serial0
R1(config-if)#
You must be in global config mode to get into interface config mode you cannot go from enable mode straight to interface configuration mode.
R1#interface serial0
^
% Invalid input detected at '^' marker.
Interface configuration mode allows you to apply an IP address to the interface, as well as many other commands related to frame relay, ISDN, and dynamic routing protocols.
For the CCNA, you need to know about two other configuration modes. To configure console commands (such as password protection), enter line configuration mode as shown here:
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#line console 0
R1(config-line)#password cisco
R1(config-line)#login
The prompt "(config-line)" indicates that you're in line configuration mode. Your console line is not the only line you'll be configuring for the CCNA, though your vty lines are used for incoming telnet connections and must be configured in a similar fashion.
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#line console 0
R1(config-line)#password cisco
R1(config-line)#login
R1(config-line)#line vty 0 4
R1(config-line)#password cisco
R1(config-line)#login
Notice that you do not have to exit one interface mode to go to another one. Let's say that you've configured your vty lines and now want to put an IP address on your Ethernet interface. You don't have to go out with ctrl-z and then start again you can go straight to interface config mode from line config mode. Just make sure you see the prompt change!
R1(config-line)#line vty 0 4
R1(config-line)#password cisco
R1(config-line)#login
R1(config-line)#interface ethernet0
R1(config-if)#ip address 15.1.1.1 255.255.255.0
When you're preparing for CCNA exam success, there's a lot to absorb. Just take it one piece at a time, get some hands-on experience to go with your theory, and before you know it you're moving around in the different Cisco router configuration modes without giving it a second thought. Keep studying and your CCNA exam success is assured!
The first mode you'll see on a router (if the person before you logged off as they should have) is user exec mode. This is also the default mode a user is placed into when using Telnet to connect to a router. The prompt will look like this:
R1>
You can't write or add to a configuration in this mode, but you can run quite a few show commands. This is a good mode to have users in who need to see the configuration, but shouldn't be allowed to change it.
To get to the next level, type enable at the user exec prompt:
R1>enable
R1#
Notice that the prompt changed. This mode has two names, the official one being privileged exec mode. It's more commonly referred to as enable mode, since "enable" is what you type to get into this mode.
This mode gives you more options for show and other commands, but you still can't configure anything. To configure global commands, use "configure terminal", or "conf t", to enter global configuration mode.
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#
The prompt has changed again, and now global configuration commands such as hostname and no ip domain-lookup can be entered.
From here, you've got a lot of options, but we'll look at three you need to know for your CCNA exams. To apply configuration commands to an interface, enter interface configuration mode, as shown here:
R1(config)#interface serial0
R1(config-if)#
You must be in global config mode to get into interface config mode you cannot go from enable mode straight to interface configuration mode.
R1#interface serial0
^
% Invalid input detected at '^' marker.
Interface configuration mode allows you to apply an IP address to the interface, as well as many other commands related to frame relay, ISDN, and dynamic routing protocols.
For the CCNA, you need to know about two other configuration modes. To configure console commands (such as password protection), enter line configuration mode as shown here:
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#line console 0
R1(config-line)#password cisco
R1(config-line)#login
The prompt "(config-line)" indicates that you're in line configuration mode. Your console line is not the only line you'll be configuring for the CCNA, though your vty lines are used for incoming telnet connections and must be configured in a similar fashion.
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#line console 0
R1(config-line)#password cisco
R1(config-line)#login
R1(config-line)#line vty 0 4
R1(config-line)#password cisco
R1(config-line)#login
Notice that you do not have to exit one interface mode to go to another one. Let's say that you've configured your vty lines and now want to put an IP address on your Ethernet interface. You don't have to go out with ctrl-z and then start again you can go straight to interface config mode from line config mode. Just make sure you see the prompt change!
R1(config-line)#line vty 0 4
R1(config-line)#password cisco
R1(config-line)#login
R1(config-line)#interface ethernet0
R1(config-if)#ip address 15.1.1.1 255.255.255.0
When you're preparing for CCNA exam success, there's a lot to absorb. Just take it one piece at a time, get some hands-on experience to go with your theory, and before you know it you're moving around in the different Cisco router configuration modes without giving it a second thought. Keep studying and your CCNA exam success is assured!
Passing The CCNA and CCNP Exams: Setup Mode
CCNA and CCNP candidates need to know all about Setup Mode, why a router goes into that mode, and as you'll see, how to get out of that mode. Practicing Setup Mode at work is a good way to get fired, though, so you need to practice this on your CCNA / CCNP home lab or rack rental. In this article, we'll take a look at a Cisco 2500 router going into setup mode and a few tips that will help you pass the exams and excel at your job.
First, why does a router go into Setup Mode in the first place? When a Cisco router boots up, the router looks into Non-Volatile RAM (NVRAM) for the startup configuration file. If such a file is not found, and the router has not been programmed to look to a TFTP server for this file, the router enters setup mode.
The most common reason for a router not to have a startup configuration file is that the file's been erased. We will now erase this file on our 2500 router. As you'll see, the Cisco router warns us about erasing NVRAM and makes us confirm this choice, which it acknowledges with the OK message.
R1#write erase
Erasing the nvram filesystem will remove all files! Continue? [confirm]
[OK]
Erase of nvram: complete
R1#
The router will now be reloaded. There is a slightly misleading message displayed during reboot:
R1#reload
Proceed with reload? [confirm]
00:15:21: %SYS-5-RELOAD: Reload requested
System Bootstrap, Version 11.0(10c)XB1, PLATFORM SPECIFIC RELEASE SOFTWARE (fc1)
Copyright (c) 1986-1997 by cisco Systems
2500 processor with 14336 Kbytes of main memory
Notice: NVRAM invalid, possibly due to write erase.
That notice doesn't mean the NVRAM is corrupt or unusable; this message means the NVRAM doesn't have a startup configuration file.
The router will continue to boot and finally present you with this prompt:
--- System Configuration Dialog ---
Would you like to enter the initial configuration dialog? [yes/no]:
Almost every WAN engineer I know answers "no" to this question, because Setup Mode is a long, clumsy way to set up a router (in my humble opinion). We will answer "yes" in order to see this mode in action.
--- System Configuration Dialog ---
Would you like to enter the initial configuration dialog? [yes/no]: y
At any point you may enter a question mark '?' for help.
Use ctrl-c to abort configuration dialog at any prompt.
Default settings are in square brackets '[]'.
Basic management setup configures only enough connectivity
for management of the system, extended setup will ask you
to configure each interface on the system
Would you like to enter basic management setup? [yes/no]: y
Configuring global parameters:
Enter host name [Router]: R1
The enable secret is a password used to protect access to
privileged EXEC and configuration modes. This password, after
entered, becomes encrypted in the configuration.
Enter enable secret:
% No defaulting allowed
Enter enable secret:
Already, there's something about Setup Mode that you might not like. This mode forces you to set an enable password and an enable secret password. As you continue in this mode, you'll see this mode ask you questions about every single interface on the router, even if you're not planning to use that interface. Using Setup Mode really does get quite old after a while, again in my opinion.
One of the most important things about Setup Mode is knowing how to get out of it without saving the configuration. One way is at the very end of this mode, where you can answer "no" to "Do you want to save this configuration?" I personally never make it that far! Instead of waiting until the end of Setup Mode, we can use the CTRL-C key combination to abort this mode and ignore the changes.
Configuration aborted, no changes made.
Press RETURN to get started!
Setup Mode is not a mode that CCNA and CCNP candidates get a great deal of practice with, but you will be tested on your knowledge about it both in the exam room and on the job. And once you start configuring a router with this mode, you'll be glad you know how to get out of it!
First, why does a router go into Setup Mode in the first place? When a Cisco router boots up, the router looks into Non-Volatile RAM (NVRAM) for the startup configuration file. If such a file is not found, and the router has not been programmed to look to a TFTP server for this file, the router enters setup mode.
The most common reason for a router not to have a startup configuration file is that the file's been erased. We will now erase this file on our 2500 router. As you'll see, the Cisco router warns us about erasing NVRAM and makes us confirm this choice, which it acknowledges with the OK message.
R1#write erase
Erasing the nvram filesystem will remove all files! Continue? [confirm]
[OK]
Erase of nvram: complete
R1#
The router will now be reloaded. There is a slightly misleading message displayed during reboot:
R1#reload
Proceed with reload? [confirm]
00:15:21: %SYS-5-RELOAD: Reload requested
System Bootstrap, Version 11.0(10c)XB1, PLATFORM SPECIFIC RELEASE SOFTWARE (fc1)
Copyright (c) 1986-1997 by cisco Systems
2500 processor with 14336 Kbytes of main memory
Notice: NVRAM invalid, possibly due to write erase.
That notice doesn't mean the NVRAM is corrupt or unusable; this message means the NVRAM doesn't have a startup configuration file.
The router will continue to boot and finally present you with this prompt:
--- System Configuration Dialog ---
Would you like to enter the initial configuration dialog? [yes/no]:
Almost every WAN engineer I know answers "no" to this question, because Setup Mode is a long, clumsy way to set up a router (in my humble opinion). We will answer "yes" in order to see this mode in action.
--- System Configuration Dialog ---
Would you like to enter the initial configuration dialog? [yes/no]: y
At any point you may enter a question mark '?' for help.
Use ctrl-c to abort configuration dialog at any prompt.
Default settings are in square brackets '[]'.
Basic management setup configures only enough connectivity
for management of the system, extended setup will ask you
to configure each interface on the system
Would you like to enter basic management setup? [yes/no]: y
Configuring global parameters:
Enter host name [Router]: R1
The enable secret is a password used to protect access to
privileged EXEC and configuration modes. This password, after
entered, becomes encrypted in the configuration.
Enter enable secret:
% No defaulting allowed
Enter enable secret:
Already, there's something about Setup Mode that you might not like. This mode forces you to set an enable password and an enable secret password. As you continue in this mode, you'll see this mode ask you questions about every single interface on the router, even if you're not planning to use that interface. Using Setup Mode really does get quite old after a while, again in my opinion.
One of the most important things about Setup Mode is knowing how to get out of it without saving the configuration. One way is at the very end of this mode, where you can answer "no" to "Do you want to save this configuration?" I personally never make it that far! Instead of waiting until the end of Setup Mode, we can use the CTRL-C key combination to abort this mode and ignore the changes.
Configuration aborted, no changes made.
Press RETURN to get started!
Setup Mode is not a mode that CCNA and CCNP candidates get a great deal of practice with, but you will be tested on your knowledge about it both in the exam room and on the job. And once you start configuring a router with this mode, you'll be glad you know how to get out of it!
Friday, December 26, 2008
Passing The CCNA And CCNP: Cisco Home Lab FAQ
There is a real revolution today among CCNA and CCNP candidates. More and more of you are turning your back on "router simulators" and putting your own CCNA and/or CCNP Home Lab together, which is the best way to totally prepare to pass these tough Cisco exams.
I get hundreds of emails every month from CCNA and CCNP candidate who are putting together their first lab or adding to their existing one. I'm always glad to help with suggestions, and I thought I'd list five common questions regarding home labs here.
Do I have to spend thousands of dollars?
No! There are vendors all over the web, as well as on ebay, who sell used Cisco routers and switches to Cisco exam candidates like you every single day. They sell kits that consist of multiple routers and switches, as well as single routers and switches. You can add one piece at a time, or make a larger investment. You can spend just a few hundred dollars and put together a very nice lab.
What's an "access server"?
It's not what it sounds like. When I first heard the term, I thought of a typical server like we see in LANs every single day. An access server is actually a Cisco router that allows you to connect to multiple other routers and switches without continually moving the rolled cable around.
You don't have to have an access server right away, but once you add a few more routers and switches to your lab, you'll get tired of moving the rollover cable from console port to console port. (The console port is used to directly connect your PC to the router.) You'll find an access server is easy to set up and configure, and will save you quite a bit of time.
What's a "frame relay switch"?
Again, it's not quite what it sounds like. A frame relay switch is not a switch; it's a Cisco router that has been configured to serve as a frame relay provider in your home lab.
This is very close to being a "must" for your home lab. You don't need it right away if your budget allows for only one or two routers to get started. To truly practice frame relay map statements and see the effect of different frame relay statements, you'll need a Cisco router to serve as a frame switch. Again, the configuration is easy, and having a frame relay switch in your home lab will give you practice that will be invaluable on exam day.
Do I need a switch? What switch should I buy?
I recommend you get at least one switch in your lab; two if your budget allows. Make sure that at least one of your switches has an IOS; 1900 switches do not have an IOS and while they're better than not having a switch, they're not going to give you the practice you need to pass the CCNA and CCNP. Look to the 2500 family of switches.
I want to build my CCNP lab and then use it for the CCIE. What should I buy?
It's impossible to tell what technologies and devices will be on the CCIE lab, even if you zip through the CCNP and then take the IE within six months. Cisco refreshing the CCIE lab blueprint every six months, and different technologies can be taken off the lab. While Cisco gives plenty of notice that these changes are going to take effect, it can be a big pain in your wallet if Cisco takes something off of the exam after you spend a bundle to add it to your lab.
As an example, Cisco is in the process of removing ISDN and ATM from the CCIE Routing & Switching lab. If you bought an ATM switch for your lab, you've got an expensive paperweight right now. While you may be able to practice your core protocols on a CCIE home lab, it's going to be difficult and expensive to keep your home lab totally current with the Cisco lab blueprint.
The decision to put together your own CCNA or CCNP home lab is the best decision you can ever make - and I speak from experience. With home labs becoming less expensive every day, it's becoming more affordable as well. Start looking into used Cisco router vendors today (ebay is a great place to find some vendors, as is Google), and you can be practicing on REAL Cisco routers and switches soon - and be totally prepared for CCNA and CCNP exam success.
I get hundreds of emails every month from CCNA and CCNP candidate who are putting together their first lab or adding to their existing one. I'm always glad to help with suggestions, and I thought I'd list five common questions regarding home labs here.
Do I have to spend thousands of dollars?
No! There are vendors all over the web, as well as on ebay, who sell used Cisco routers and switches to Cisco exam candidates like you every single day. They sell kits that consist of multiple routers and switches, as well as single routers and switches. You can add one piece at a time, or make a larger investment. You can spend just a few hundred dollars and put together a very nice lab.
What's an "access server"?
It's not what it sounds like. When I first heard the term, I thought of a typical server like we see in LANs every single day. An access server is actually a Cisco router that allows you to connect to multiple other routers and switches without continually moving the rolled cable around.
You don't have to have an access server right away, but once you add a few more routers and switches to your lab, you'll get tired of moving the rollover cable from console port to console port. (The console port is used to directly connect your PC to the router.) You'll find an access server is easy to set up and configure, and will save you quite a bit of time.
What's a "frame relay switch"?
Again, it's not quite what it sounds like. A frame relay switch is not a switch; it's a Cisco router that has been configured to serve as a frame relay provider in your home lab.
This is very close to being a "must" for your home lab. You don't need it right away if your budget allows for only one or two routers to get started. To truly practice frame relay map statements and see the effect of different frame relay statements, you'll need a Cisco router to serve as a frame switch. Again, the configuration is easy, and having a frame relay switch in your home lab will give you practice that will be invaluable on exam day.
Do I need a switch? What switch should I buy?
I recommend you get at least one switch in your lab; two if your budget allows. Make sure that at least one of your switches has an IOS; 1900 switches do not have an IOS and while they're better than not having a switch, they're not going to give you the practice you need to pass the CCNA and CCNP. Look to the 2500 family of switches.
I want to build my CCNP lab and then use it for the CCIE. What should I buy?
It's impossible to tell what technologies and devices will be on the CCIE lab, even if you zip through the CCNP and then take the IE within six months. Cisco refreshing the CCIE lab blueprint every six months, and different technologies can be taken off the lab. While Cisco gives plenty of notice that these changes are going to take effect, it can be a big pain in your wallet if Cisco takes something off of the exam after you spend a bundle to add it to your lab.
As an example, Cisco is in the process of removing ISDN and ATM from the CCIE Routing & Switching lab. If you bought an ATM switch for your lab, you've got an expensive paperweight right now. While you may be able to practice your core protocols on a CCIE home lab, it's going to be difficult and expensive to keep your home lab totally current with the Cisco lab blueprint.
The decision to put together your own CCNA or CCNP home lab is the best decision you can ever make - and I speak from experience. With home labs becoming less expensive every day, it's becoming more affordable as well. Start looking into used Cisco router vendors today (ebay is a great place to find some vendors, as is Google), and you can be practicing on REAL Cisco routers and switches soon - and be totally prepared for CCNA and CCNP exam success.
Passing Cisco’s CCNA and CCNP Exams: Traceroute
In preparation for your CCNA and CCNP exam success, you've got to learn to troubleshoot Cisco routers. And while ping is a great basic IP connectivity tool, it doesn't give you all the information you need to diagnose network connectivity issues.
Let's say you have six routers between CityA and CityB. You send a ping from A to B, and get this return:
R1#ping 172.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.1.1.1, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
The five periods indicate that there is no IP connectivity to CityB. Problem is, that's about all ping tells you. You can have 5 or 50 routers between the two points, so how can you tell which downstream router has the problem?
That's where traceroute comes in. Traceroute sends three datagrams with a Time To Live (TTL) of 1. Those datagrams will timeout once they hit the first router in the path, and that router will respond with an ICMP Time Exceeded message.
In response, the sending router sends three more datagrams, but these have a TTL of 2. This means that the next router in line will send back ICMP Time Exceeded messages. This process continues until the final destination (CItyB) is reached the output of the command shows us the path the data took:
Router1#traceroute 271.1.1.1
Type escape sequence to abort.
Tracing the route to 271.1.1.1
1 20.1.1.1 4 msec 4 msec 4 msec
2 30.1.1.1 20 msec 16 msec 16 msec
3 271.1.1.1 16 msec * 16 msec
How does this help troubleshoot a problem? Let's say that the second router in this path, 30.1.1.1, doesn't know how to get to 271.1.1.1. The output would look like this:
Router1#traceroute 271.1.1.1
Type escape sequence to abort.
Tracing the route to 271.1.1.1
1 20.1.1.1 4 msec 4 msec 4 msec
2 30.1.1.1 20 msec 16 msec 16 msec
3 * * *
This indicates that the router at 30.1.1.1 doesn't know how to get to the final destination. Now you have a better idea of which router has an issue!
Now here's the bad part: you're going to get 30 lines of three asterisks, and until you abort this traceroute, you're going to just watch those asterisks go across the screen. There's an abort sequence that the router mentions in the first line of the console output, but the router doesn't tell you what it is! So I will - this top-secret sequence is TWICE, one right after the other.
That keystroke takes a little getting used to, but a CCNA or CCNP can do it! Add this command to your Cisco skill set, and it will serve you well both on the CCNA and CCNP exams and your real-world networks. And you'll impress your friends by knowing how to stop a traceroute!
Let's say you have six routers between CityA and CityB. You send a ping from A to B, and get this return:
R1#ping 172.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.1.1.1, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
The five periods indicate that there is no IP connectivity to CityB. Problem is, that's about all ping tells you. You can have 5 or 50 routers between the two points, so how can you tell which downstream router has the problem?
That's where traceroute comes in. Traceroute sends three datagrams with a Time To Live (TTL) of 1. Those datagrams will timeout once they hit the first router in the path, and that router will respond with an ICMP Time Exceeded message.
In response, the sending router sends three more datagrams, but these have a TTL of 2. This means that the next router in line will send back ICMP Time Exceeded messages. This process continues until the final destination (CItyB) is reached the output of the command shows us the path the data took:
Router1#traceroute 271.1.1.1
Type escape sequence to abort.
Tracing the route to 271.1.1.1
1 20.1.1.1 4 msec 4 msec 4 msec
2 30.1.1.1 20 msec 16 msec 16 msec
3 271.1.1.1 16 msec * 16 msec
How does this help troubleshoot a problem? Let's say that the second router in this path, 30.1.1.1, doesn't know how to get to 271.1.1.1. The output would look like this:
Router1#traceroute 271.1.1.1
Type escape sequence to abort.
Tracing the route to 271.1.1.1
1 20.1.1.1 4 msec 4 msec 4 msec
2 30.1.1.1 20 msec 16 msec 16 msec
3 * * *
This indicates that the router at 30.1.1.1 doesn't know how to get to the final destination. Now you have a better idea of which router has an issue!
Now here's the bad part: you're going to get 30 lines of three asterisks, and until you abort this traceroute, you're going to just watch those asterisks go across the screen. There's an abort sequence that the router mentions in the first line of the console output, but the router doesn't tell you what it is! So I will - this top-secret sequence is TWICE, one right after the other.
That keystroke takes a little getting used to, but a CCNA or CCNP can do it! Add this command to your Cisco skill set, and it will serve you well both on the CCNA and CCNP exams and your real-world networks. And you'll impress your friends by knowing how to stop a traceroute!
Passing Cisco's CCNA and CCNP Exams: Five Tips For Exam Day Success
As you get ready to pass the CCNA or CCNP exams, you can feel quite a bit of stress as you enter your last week of study. Let's take a look at a few ways to reduce that stress.
1. Do not stay up late cramming. The CCNA and CCNP are not exams you're going to pass by cramming. "Cramming" is a study technique best left behind in junior high school. The CCNA can't be passed by memorization - you've got to know how Cisco technologies work. That leads us to the second point...
2. Get lots of rest. By far, this is the most overlooked factor on exam day. The CCNA and CCNP exams are going to demand your best. You're going to be performing subnetting, binary and hex conversions, analyzing network diagrams for troubleshooting, and much more. You've got to be mentally sharp. You can add 100 points to your exam score just by showing up well-rested. And let's be realistic - if you don't know something at 11 PM the night before your exam, you're not going to learn it overnight. Get some sleep!
3. Get everything together the night before the exam. You don't want to be running around the house the morning of the exam looking for your keys. Make sure you have your keys and your ID the night before the exam.
4. Know where the testing center is. If you've never been to the center you'll be passing the CCNA in before, go there before the morning of the exam. Do not rely on Mapquest or a friend's directions. You don't want to be late for your exam.
5. Allow for traffic. Many CCNA and CCNP candidates prefer to take their exams in the morning. Again, if you haven't been to the exam center before, you should drive there during morning rush hour traffic before your exam date to make sure you have enough time to get there. You don't want to be sitting in traffic when you should be sitting in the exam room!
1. Do not stay up late cramming. The CCNA and CCNP are not exams you're going to pass by cramming. "Cramming" is a study technique best left behind in junior high school. The CCNA can't be passed by memorization - you've got to know how Cisco technologies work. That leads us to the second point...
2. Get lots of rest. By far, this is the most overlooked factor on exam day. The CCNA and CCNP exams are going to demand your best. You're going to be performing subnetting, binary and hex conversions, analyzing network diagrams for troubleshooting, and much more. You've got to be mentally sharp. You can add 100 points to your exam score just by showing up well-rested. And let's be realistic - if you don't know something at 11 PM the night before your exam, you're not going to learn it overnight. Get some sleep!
3. Get everything together the night before the exam. You don't want to be running around the house the morning of the exam looking for your keys. Make sure you have your keys and your ID the night before the exam.
4. Know where the testing center is. If you've never been to the center you'll be passing the CCNA in before, go there before the morning of the exam. Do not rely on Mapquest or a friend's directions. You don't want to be late for your exam.
5. Allow for traffic. Many CCNA and CCNP candidates prefer to take their exams in the morning. Again, if you haven't been to the exam center before, you should drive there during morning rush hour traffic before your exam date to make sure you have enough time to get there. You don't want to be sitting in traffic when you should be sitting in the exam room!
Passing Cisco CCNA And CCNP Exams: Ping And Extended Ping
I often tell CCNA and CCNP candidates that you do your best learning when you screw something up. I often get a funny look right after I say that, but the only way to develop your Cisco troubleshooting skills - the skills you'll need to pass your Intro, ICND, and CCNP exams - is by actually fixing configurations. Since your employer will take a dim view of you practicing these skills on his or her network, you better do so on your home lab!
Three essential tools for networking and CCNA/CCNP exam success are ping, extended ping, and traceroute. Today we're going to take a look at the ping that we're used to using for LAN issues, and the extended ping.
We're all familiar with "basic" ping, where you use the ping command followed by the IP address you want to confirm IP connectivity with. When you've got connectivity, you will see five exclamation points, as seen here:
R1#ping 172.12.123.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.12.123.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 68/68/72 ms
The default source IP address for ping is the IP address closest to the destination IP address. Other defaults - five ICMP packets will be sent (that's why you see five exclamation points), and they're sent two seconds apart.
That's fine for many basic situations, but as you progress through your networking career and most advanced scenarios in your CCNA / CCNP studies, you will want to change some of these defaults. What could you do if you wanted to send 10,000 pings? What if you needed your router's loopback address to be the source IP address for the pings? What if you wanted to send them five seconds apart, instead of two?
That's where extended ping comes in. To use extended ping, just type "ping" and hit enter. (Note that you cannot use extended ping in user exec mode - you must be in enable mode to do so.)
R1>ping
% Incomplete command.
"incomplete command" indicates that the router is waiting for an IP address; you can't use extended ping in user exec mode.
R1>enable
R1#ping
Protocol [ip]:
Target IP address: 172.16.123.1
Repeat count [5]: 1000
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface: loopback0
Type of service [0]:
Set DF bit in IP header? [no]:
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 1000, 100-byte ICMP Echos to 172.16.123.1, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1
.......................................
In this example, I sent 1000 ICMP packets to an address that doesn't exist, so I am getting periods instead of exclamation points. This illustration shows you the many options you have with extended ping.
Now that I've sent those 1000 pings, let's say that I want to stop that process. At the beginning of the basic ping output, you see this phrase:
Type escape sequence to abort.
This escape sequence works for ping, extended ping, and traceroute. Funny thing, though - Cisco doesn't tell you what the escape sequence is! One day, this will really come in handy. The escape sequence is, TWICE in rapid succession.
After I used it in this example, the pings stopped and I got this message:
Success rate is 0 percent (0/192)
The ping stopped after 192 ICMP packets were sent.
This keystroke takes a little practice, so practice it in your home lab. Knowing how to use extended ping will really come in handy on your CCNA and CCNP exams as well as your real-life networking job, and knowing how to stop an extended ping will as well!
Three essential tools for networking and CCNA/CCNP exam success are ping, extended ping, and traceroute. Today we're going to take a look at the ping that we're used to using for LAN issues, and the extended ping.
We're all familiar with "basic" ping, where you use the ping command followed by the IP address you want to confirm IP connectivity with. When you've got connectivity, you will see five exclamation points, as seen here:
R1#ping 172.12.123.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.12.123.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 68/68/72 ms
The default source IP address for ping is the IP address closest to the destination IP address. Other defaults - five ICMP packets will be sent (that's why you see five exclamation points), and they're sent two seconds apart.
That's fine for many basic situations, but as you progress through your networking career and most advanced scenarios in your CCNA / CCNP studies, you will want to change some of these defaults. What could you do if you wanted to send 10,000 pings? What if you needed your router's loopback address to be the source IP address for the pings? What if you wanted to send them five seconds apart, instead of two?
That's where extended ping comes in. To use extended ping, just type "ping" and hit enter. (Note that you cannot use extended ping in user exec mode - you must be in enable mode to do so.)
R1>ping
% Incomplete command.
"incomplete command" indicates that the router is waiting for an IP address; you can't use extended ping in user exec mode.
R1>enable
R1#ping
Protocol [ip]:
Target IP address: 172.16.123.1
Repeat count [5]: 1000
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface: loopback0
Type of service [0]:
Set DF bit in IP header? [no]:
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 1000, 100-byte ICMP Echos to 172.16.123.1, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1
.......................................
In this example, I sent 1000 ICMP packets to an address that doesn't exist, so I am getting periods instead of exclamation points. This illustration shows you the many options you have with extended ping.
Now that I've sent those 1000 pings, let's say that I want to stop that process. At the beginning of the basic ping output, you see this phrase:
Type escape sequence to abort.
This escape sequence works for ping, extended ping, and traceroute. Funny thing, though - Cisco doesn't tell you what the escape sequence is! One day, this will really come in handy. The escape sequence is
After I used it in this example, the pings stopped and I got this message:
Success rate is 0 percent (0/192)
The ping stopped after 192 ICMP packets were sent.
This keystroke takes a little practice, so practice it in your home lab. Knowing how to use extended ping will really come in handy on your CCNA and CCNP exams as well as your real-life networking job, and knowing how to stop an extended ping will as well!
Four Important Commands For Your CCNA / CCNP Home Lab
More CCNA and CCNP candidates than ever before are putting together their own home practice labs. It's more affordable than it ever has been, and I receive emails daily from new CCNAs and CCNPs who say it's the best thing they could have done to improve their studies.
There are some commands you can configure on your lab routers that won't necessarily be on your CCNA or CCNP exams, but they will make life a lot easier for you. Let's take a look at just a few of these.
The command "no exec" is short, yet powerful. Occasionally you'll have what is referred to as a "rogue EXEC" process tie up a line, and you end up having to continually clear lines, which disrupts your practice. If you have an access server, I highly recommend you configure this command on your lines, as shown here:
ACCESS_SERVER(con)#line 1 8
ACCESS_SERVER(con)#no exec
From your CCNA studies, you know that the command "no ip domain-lookup" prevents a Cisco router from sending a broadcast to find a DNS server anytime you enter something that is not an IOS command - and that includes mistyped commands, which happens to all of us sooner or later. Make sure to run that command in global configuration mode on all your practice routers.
There are two commands I like to configure on the console line on all my practice routers and switches. The first is "exec-timeout 0 0", which prevents you from being kicked out of enable mode and back into user exec after a few minutes of inactivity. (This doesn't sound like much, but you'll get pretty tired of typing "enable" after a while.) The first zero refers to minutes, the second zero to seconds. Setting them both to zero disables the exec-timeout function.
The second command prevents the router from interrupting the command you're typing with a console message. If you've ever been in the middle of typing a router command and suddenly you're interrupted with a logging message, you know that can be pretty annoying. We don't want the router to not display the message, but we do want the router to wait until we're done entering data. The command to perform this is "logging synchronous".
R1(config)#line console 0
R1(config-line)#exec-timeout 0 0
R1(config-line)#logging synchronous
You won't see many of these commands on your exams, but after you configure them on your home lab devices, you'll wonder how you did without them!
There are some commands you can configure on your lab routers that won't necessarily be on your CCNA or CCNP exams, but they will make life a lot easier for you. Let's take a look at just a few of these.
The command "no exec" is short, yet powerful. Occasionally you'll have what is referred to as a "rogue EXEC" process tie up a line, and you end up having to continually clear lines, which disrupts your practice. If you have an access server, I highly recommend you configure this command on your lines, as shown here:
ACCESS_SERVER(con)#line 1 8
ACCESS_SERVER(con)#no exec
From your CCNA studies, you know that the command "no ip domain-lookup" prevents a Cisco router from sending a broadcast to find a DNS server anytime you enter something that is not an IOS command - and that includes mistyped commands, which happens to all of us sooner or later. Make sure to run that command in global configuration mode on all your practice routers.
There are two commands I like to configure on the console line on all my practice routers and switches. The first is "exec-timeout 0 0", which prevents you from being kicked out of enable mode and back into user exec after a few minutes of inactivity. (This doesn't sound like much, but you'll get pretty tired of typing "enable" after a while.) The first zero refers to minutes, the second zero to seconds. Setting them both to zero disables the exec-timeout function.
The second command prevents the router from interrupting the command you're typing with a console message. If you've ever been in the middle of typing a router command and suddenly you're interrupted with a logging message, you know that can be pretty annoying. We don't want the router to not display the message, but we do want the router to wait until we're done entering data. The command to perform this is "logging synchronous".
R1(config)#line console 0
R1(config-line)#exec-timeout 0 0
R1(config-line)#logging synchronous
You won't see many of these commands on your exams, but after you configure them on your home lab devices, you'll wonder how you did without them!
Computer Certification: Become A Utility Player
In baseball, a "utility player" is one who plays more than one position. These players are usually backups, but they have a job in the major leagues because of their value to the team; since they can play more than one position, they have that much more value to their employer.
Too often in IT, workers become either LAN or WAN engineers, knowing little if anything about the other side. Many LAN administrators I worked with knew little about routing and switching, while many WAN engineers I knew not only didn't know much about the LAN side of their network, but they didn't want to know anything about the servers!
In today's IT world, it's a bad idea to specialize in only one thing and not know how to do anything else. Not only does it limit your future career prospects, but it limits your current prospects as well. Employers don't want to hire someone and have them get up to speed on the job - they want someone who can walk right in and do the job. The more you know, the better your chance of getting a better job - or quickly being able to get another job if you were laid off tomorrow.
A term often heard on Wall Street is "diversification", meaning that investors should not invest heavily or totally in only one stock; if that stock plummets, they're in big trouble. Your career is the most important stock you will ever own, and you're 100% in charge of it. Diversify. If you're working primarily with servers, learn some routing and switching. If you know the routing protocols your company uses on its WAN, learn something about that protocol. (If you don't know the protocol, ask!)
While you’re adding these skills, get certified while you’re at it! Adding a CCNA, MCSE, or other computer certification looks great on your resume while signaling to employers that you’re constantly adding to your skills.
Adding more skills and knowledge to your IT skill set is always a good idea. Don't limit yourself to the technologies you work with every day. Make an investment in yourself and become a well-rounded network engineer. This will help you keep the job you have - and open doors in the future that might otherwise have remained closed.
Too often in IT, workers become either LAN or WAN engineers, knowing little if anything about the other side. Many LAN administrators I worked with knew little about routing and switching, while many WAN engineers I knew not only didn't know much about the LAN side of their network, but they didn't want to know anything about the servers!
In today's IT world, it's a bad idea to specialize in only one thing and not know how to do anything else. Not only does it limit your future career prospects, but it limits your current prospects as well. Employers don't want to hire someone and have them get up to speed on the job - they want someone who can walk right in and do the job. The more you know, the better your chance of getting a better job - or quickly being able to get another job if you were laid off tomorrow.
A term often heard on Wall Street is "diversification", meaning that investors should not invest heavily or totally in only one stock; if that stock plummets, they're in big trouble. Your career is the most important stock you will ever own, and you're 100% in charge of it. Diversify. If you're working primarily with servers, learn some routing and switching. If you know the routing protocols your company uses on its WAN, learn something about that protocol. (If you don't know the protocol, ask!)
While you’re adding these skills, get certified while you’re at it! Adding a CCNA, MCSE, or other computer certification looks great on your resume while signaling to employers that you’re constantly adding to your skills.
Adding more skills and knowledge to your IT skill set is always a good idea. Don't limit yourself to the technologies you work with every day. Make an investment in yourself and become a well-rounded network engineer. This will help you keep the job you have - and open doors in the future that might otherwise have remained closed.
Cisco Certification: The "Secret" Key To Getting Your CCNA And CCNP
Whether you're working on your CCNA or CCNP, Cisco certification exams are the most demanding computer certification exams in the IT field. Cisco exams are not a test of memorization, they're a test of your analytical skills. You'll need to look at configurations and console output and analyze them to identify problems and answer detailed questions. To pass these demanding exams, you've got to truly understand how Cisco routers and switches operate - and the key to doing so is right in front of you.
The debug command.
Of course, there is no single "debug" command. Using IOS Help, you can quickly see that there are hundreds of these debugs, and I want to mention immediately that you should never practice these commands on a production router. This is one major reason you need to get some hands-on experience with Cisco products in a home lab or rack rental. No software program or "simulator" is going to give you the debug practice you need.
Now, why am I so insistent that you use debugs? Because that's how you actually see what's going on. It's not enough to type a frame relay LMI command, you have to be able to see the LMIs being exchanged with "debug frame lmi". You don't want to just type a few network numbers in after enabling RIP, you want to see the routes being advertised along with their metrics with "debug ip rip". The list goes on and on.
By using debugs as part of your CCNA and CCNP studies, you're going beyond just memorizing commands and thinking you understand everything that's happening when you enter a command or two. You move to a higher level of understanding how routers, switches, and protocols work -- and that is the true goal of earning your CCNA and CCNP.
The debug command.
Of course, there is no single "debug" command. Using IOS Help, you can quickly see that there are hundreds of these debugs, and I want to mention immediately that you should never practice these commands on a production router. This is one major reason you need to get some hands-on experience with Cisco products in a home lab or rack rental. No software program or "simulator" is going to give you the debug practice you need.
Now, why am I so insistent that you use debugs? Because that's how you actually see what's going on. It's not enough to type a frame relay LMI command, you have to be able to see the LMIs being exchanged with "debug frame lmi". You don't want to just type a few network numbers in after enabling RIP, you want to see the routes being advertised along with their metrics with "debug ip rip". The list goes on and on.
By using debugs as part of your CCNA and CCNP studies, you're going beyond just memorizing commands and thinking you understand everything that's happening when you enter a command or two. You move to a higher level of understanding how routers, switches, and protocols work -- and that is the true goal of earning your CCNA and CCNP.
Cisco Certification: Recertifying Your CCNA and CCNP
Once you get your CCNA and CCNP, you can't just rest on your accomplishment. You've got to continue to study and add to your skill set - and then prove to Cisco you've been doing just that by recertifying.
Recertification sounds like a pain, but it's actually one of the best things to ever happen to computer certification, and it helps your career as well. One trap many LAN and WAN personnel fall into is that they fail to keep up with changes in technology, and if they happen to be laid off or want to change jobs, they're unable to because they didn't keep their skill set up.
Cisco's recertification policies ensure that if you want to keep your CCNA, CCNP, or one of the other valuable Cisco certifications, you've got to take a recertification exam.
As of November 2005, to recertify as a CCNA, you need to pass either the current CCNA exam, ICND exam, or any 642 professional level or Cisco Qualified Specialist exam. (This does not include Sales Specialist exams.) Passing a CCIE written qualification exam also recertifies you as a CCNA. CCNAs are valid for three years.
For the CCNP, you need to pass the 642-891 Composite exam, a CCIE written qualification exam, or BOTH the BSCI and BCMSN exams (642-801 and 642-811, respectively.) CCNP certifications are valid for three years.
As you can see, you've got quite a few options either way. The one classic mistake you must not make is waiting too long to begin preparing for the exams, and give yourself a little leeway just in case you don't recertify the first time around. Once the deadline passes, your certification is gone, and in the case of the CCNP that means taking all the exams again.
As a professional, it's your responsibility to keep up with changes in the Cisco certification world, and this includes changes in the recertification program. Make a point of visiting the "Learning And Events" section of Cisco's website regularly to look for changes in the certification program. And while you're there, you just might see another cert that catches your eye!
Recertification sounds like a pain, but it's actually one of the best things to ever happen to computer certification, and it helps your career as well. One trap many LAN and WAN personnel fall into is that they fail to keep up with changes in technology, and if they happen to be laid off or want to change jobs, they're unable to because they didn't keep their skill set up.
Cisco's recertification policies ensure that if you want to keep your CCNA, CCNP, or one of the other valuable Cisco certifications, you've got to take a recertification exam.
As of November 2005, to recertify as a CCNA, you need to pass either the current CCNA exam, ICND exam, or any 642 professional level or Cisco Qualified Specialist exam. (This does not include Sales Specialist exams.) Passing a CCIE written qualification exam also recertifies you as a CCNA. CCNAs are valid for three years.
For the CCNP, you need to pass the 642-891 Composite exam, a CCIE written qualification exam, or BOTH the BSCI and BCMSN exams (642-801 and 642-811, respectively.) CCNP certifications are valid for three years.
As you can see, you've got quite a few options either way. The one classic mistake you must not make is waiting too long to begin preparing for the exams, and give yourself a little leeway just in case you don't recertify the first time around. Once the deadline passes, your certification is gone, and in the case of the CCNP that means taking all the exams again.
As a professional, it's your responsibility to keep up with changes in the Cisco certification world, and this includes changes in the recertification program. Make a point of visiting the "Learning And Events" section of Cisco's website regularly to look for changes in the certification program. And while you're there, you just might see another cert that catches your eye!
Thursday, December 25, 2008
Cisco CCNP Certification: Using The BGP Command “Update-Source”
When you start preparing for your CCNP exam, particularly the BSCI exam, you're introduced to Border Gateway Protocol (BGP) configurations. BGP is unlike any protocol you learned during your CCNA studies, and even the similarities are a little bit different!
BGP forms neighbor relationships, much like EIGRP and OSPF do. The interesting thing with BGP is that potential neighbors, or "peers", do not need to be directly connected and can use their loopback interfaces to form the peer relationships.
It may well be to your advantage to use loopbacks to form peer relationships rather than the actual interface facing the potential neighbor. This can be done because BGP uses static neighbor statements rather than any kind of dynamic neighbor discovery process.
Consider a router that has two paths to a BGP speaker. The interfaces are numbered like this:
Router1: Serial0, 172.1.1.1 /24, Serial2, 179.1.1.1 /24, loopback0, 1.1.1.1 /32.
Router2: Serial0, 172.1.1.2/24, Serial2 179.1.1.2/24, loopback0, 2.2.2.2 /32.
We could configure Router1 like this:
router bgp 200
neighbor 172.1.1.2 remote-as 200
In this case, BGP would automatically use 172.1.1.1 as the source for the TCP connection that has to be set up with the neighbor before updates can be exchanged; this address is known as the best local address. However, if the remote peer's serial0 interface is shut down or goes down for another reason, the peer relationship would be lost even though Router2 is still available.
Instead of using one of the physical interfaces, we can use the loopbacks on each router to establish the TCP-based peer connection. The configurations would look like this:
Router1:
router bgp 200
neighbor 2.2.2.2 remote-as 200
neighbor 2.2.2.2 update-source loopback0
Router2:
router bgp 200
neighbor 1.1.1.1 remote-as 200
neighbor 1.1.1.1 update-source loopback0
In this case, losing one of the physical connections does not necessarily mean the BGP peering is lost; as long as the routers have a valid path to each other's loopback addresses, the BGP peer relationship will stay in place. And better yet, we avoid the dreaded “single point of failure
BGP forms neighbor relationships, much like EIGRP and OSPF do. The interesting thing with BGP is that potential neighbors, or "peers", do not need to be directly connected and can use their loopback interfaces to form the peer relationships.
It may well be to your advantage to use loopbacks to form peer relationships rather than the actual interface facing the potential neighbor. This can be done because BGP uses static neighbor statements rather than any kind of dynamic neighbor discovery process.
Consider a router that has two paths to a BGP speaker. The interfaces are numbered like this:
Router1: Serial0, 172.1.1.1 /24, Serial2, 179.1.1.1 /24, loopback0, 1.1.1.1 /32.
Router2: Serial0, 172.1.1.2/24, Serial2 179.1.1.2/24, loopback0, 2.2.2.2 /32.
We could configure Router1 like this:
router bgp 200
neighbor 172.1.1.2 remote-as 200
In this case, BGP would automatically use 172.1.1.1 as the source for the TCP connection that has to be set up with the neighbor before updates can be exchanged; this address is known as the best local address. However, if the remote peer's serial0 interface is shut down or goes down for another reason, the peer relationship would be lost even though Router2 is still available.
Instead of using one of the physical interfaces, we can use the loopbacks on each router to establish the TCP-based peer connection. The configurations would look like this:
Router1:
router bgp 200
neighbor 2.2.2.2 remote-as 200
neighbor 2.2.2.2 update-source loopback0
Router2:
router bgp 200
neighbor 1.1.1.1 remote-as 200
neighbor 1.1.1.1 update-source loopback0
In this case, losing one of the physical connections does not necessarily mean the BGP peering is lost; as long as the routers have a valid path to each other's loopback addresses, the BGP peer relationship will stay in place. And better yet, we avoid the dreaded “single point of failure
Cisco CCNP / BSCI Exam Tutorial: OSPF Router Types
When you're preparing to pass the BSCI exam on the way to the coveted Cisco CCNP certification, you can be quickly overwhelmed by the sheer amount of BGP and OSPF knowledge you must demonstrate a mastery of. One set of details that some BSCI and CCNP candidates underestimate are the differences between the OSPF router types.
An OSPF Internal router has one rule - it must have all its interfaces in a single area. It does not mean that area has to be Area 0.
An OSPF Backbone router is a router with at least a single area in the OSPF backbone area, Area 0. A router can be both an Internal and Backbone router if all its interfaces are in Area 0.
An Area Border Router has at least one interface in Area 0 and another interface in a non-backbone area. ABRs are also one of two router types that can perform OSPF route summarization. (To advertise a summary route from one OSPF area to another, use the area range command on the ABR.)
Finally, an ASBR is an OSPF router that is performing route redistribution by injecting routes from another source into the OSPF domain. This is the other OSPF router type that can perform route summarization; to summarize routes being redistributed into OSPF, use the summary-address command on the ASBR.
There are several commands you can use to determine the router types in a given OSPF area. The command "show ip ospf" will display quite a bit of information regarding the local router, and this includes whether that router is acting as an ABR or ASBR. To see the routes to the ABRs and ASBRs from the local router, run "show ip ospf border-routers".
An OSPF Internal router has one rule - it must have all its interfaces in a single area. It does not mean that area has to be Area 0.
An OSPF Backbone router is a router with at least a single area in the OSPF backbone area, Area 0. A router can be both an Internal and Backbone router if all its interfaces are in Area 0.
An Area Border Router has at least one interface in Area 0 and another interface in a non-backbone area. ABRs are also one of two router types that can perform OSPF route summarization. (To advertise a summary route from one OSPF area to another, use the area range command on the ABR.)
Finally, an ASBR is an OSPF router that is performing route redistribution by injecting routes from another source into the OSPF domain. This is the other OSPF router type that can perform route summarization; to summarize routes being redistributed into OSPF, use the summary-address command on the ASBR.
There are several commands you can use to determine the router types in a given OSPF area. The command "show ip ospf" will display quite a bit of information regarding the local router, and this includes whether that router is acting as an ABR or ASBR. To see the routes to the ABRs and ASBRs from the local router, run "show ip ospf border-routers".
Cisco CCNA Exam Tutorial: Using Trivial File Transfer Protocol (TFTP)
One of the first things you do when you start studying for the CCNA exam is memorizing a list of port numbers and the protocols that run on those ports. If you're an experienced networker, you know most of the protocols that are mentioned - DNS, DHCP, FTP, SMTP, and so on. But there's one protocol that you might not have experience with, but is actually vital for CCNA exam success and success in working with Cisco routers and switches, and that's TFTP - Trivial File Transfer Protocol.
TFTP is basically FTP's non-secure relative. There are no passwords, no authentication scheme, no nothing! As someone once told me, "If I'm transferring my files, there's nothing 'trivial' about it."
Great. So you’re thinking, “What the heck do we use TFTP for, anyway?”
TFTP is used in the Cisco world to perform IOS upgrades and to save configs to a TFTP Server. Cisco routers can themselves serve as TFTP servers, or you can use a workstation to fill that role.
If you needed to copy an IOS image to a router, for example, you could do so easily by connecting your PC to the router’s console port (via a rollover cable, right?). Your PC would need to run TFTP server software. There are quite a few free TFTP server software programs that work quite well – just enter “free tftp server” into Google or your favorite search engine and you’ll see what I mean.
Using TFTP in this fashion is a great way to have backup copies of IOS images or router configs right on your laptop. And take it from me, when the day comes that you need those backups, you’ll be glad you did!
Remember that when using the copy command, you first indicate where you’re copying from, then where you’re copying to:
R1#copy flash tftp
Source filename []? Example
Address or name of remote host []?
When performing such a copy, you’ll need to name the file you’re copying, as well as the IP address of the device you’re copying to.
Using TFTP to perform IOS upgrades takes a little getting used to, especially the syntax of the copy command. But knowing that syntax and how to use TFTP will indeed get you one step closer to the CCNA!
TFTP is basically FTP's non-secure relative. There are no passwords, no authentication scheme, no nothing! As someone once told me, "If I'm transferring my files, there's nothing 'trivial' about it."
Great. So you’re thinking, “What the heck do we use TFTP for, anyway?”
TFTP is used in the Cisco world to perform IOS upgrades and to save configs to a TFTP Server. Cisco routers can themselves serve as TFTP servers, or you can use a workstation to fill that role.
If you needed to copy an IOS image to a router, for example, you could do so easily by connecting your PC to the router’s console port (via a rollover cable, right?). Your PC would need to run TFTP server software. There are quite a few free TFTP server software programs that work quite well – just enter “free tftp server” into Google or your favorite search engine and you’ll see what I mean.
Using TFTP in this fashion is a great way to have backup copies of IOS images or router configs right on your laptop. And take it from me, when the day comes that you need those backups, you’ll be glad you did!
Remember that when using the copy command, you first indicate where you’re copying from, then where you’re copying to:
R1#copy flash tftp
Source filename []? Example
Address or name of remote host []?
When performing such a copy, you’ll need to name the file you’re copying, as well as the IP address of the device you’re copying to.
Using TFTP to perform IOS upgrades takes a little getting used to, especially the syntax of the copy command. But knowing that syntax and how to use TFTP will indeed get you one step closer to the CCNA!
Cisco CCNA Exam Tutorial: How To Spend Your Study Time
To pass the CCNA exam, you've got to create a study plan. Part of that plan is scheduling your study time, and making that study time count.
You’ve scheduled your exam you’ve created a document to track your study time you’ve planned exactly when you’re going to study. Now the plan must be carried out, without exception.
What exceptions do I mean? Cell phones. Televisions. IPods. Significant others. The list can go on and on.
It’s one thing to have a plan, and an important thing now you’ve got to make sure you carry it out to its fullest potential. That’s easy to say until you’re studying and a friend calls, or you remember that TV show you wanted to watch is on tonight, or you start surfing the Web for Cisco information and end up playing a game.
You MUST make these small sacrifices in order to achieve your main goal, the CCNA. Any worthwhile accomplishment requires some small sacrifice.
TV will be there when you’re done studying. Your significant other will be there when you’re done studying. And believe it or not, people once existed without cell phones! Turn the phone off. Turn your instant messenger service off. Turn your text pager off. Despite what we think, the world can do without communicating with us for 90 minutes. Remember, it’s better to have 90 minutes of great study than 180 minutes of constantly interrupted study. Studies show that while a single phone call causes an 11-minute interruption on average, it takes well over 20 minutes to get back to what you were doing with the proper mental focus. This is true at the office and at your home!
How To Spend Your Study Time CCNA candidates generally spend their time split between book study, practice exams, and lab time on real Cisco equipment. The best study is done by a combination of these, not by overly relying on one. Let’s take a look at each method.
Book study – I’ve never understood why some people (usually the trolls we were talking about earlier) talk about book study like it’s a bad thing. "You can’t learn about technology from books." What a load of manure. You have to learn the theory before you can understand how a router or switch operates. The best way to learn the theory is to read a good book.
At the CCNA level, you doubtless know that you have dozens of choices when it comes to books. Some of the better-known books really do gloss over some important topics, such as binary math and subnetting. Make sure to pick a book or books that go beyond just explaining the theory and that give you a lot of explanation of router configs and real-world examples as well.
Practice Exams: Practice exams are good in moderation, but don’t use them as your main focus of study. Occasionally, I’m asked for study tips by candidates who have taken the exam a few times and not passed yet. I ask them what they’re doing to prepare, and they give a list of companies they bought practice exams from. (You see a lot of this on Internet forums as well.)
Don’t fall into this trap. Practice exams are fine if used as a readiness check, but some candidates just take them over and over again, which renders them basically useless.
On top of that, some of them cost hundreds of dollars. That’s money you’d be much better off spending on Cisco equipment to practice on.
Again, I’m not against practice exams as a supplement to your studies. Just don’t make them the main focus of your study. Taking practice exams over and over and hoping the exam will be just like the practice exam is a recipe for disaster. As I tell my students, when you’re in front of a rack of routers and switches during a job interview (or at 2AM when you’ve been called in to fix a problem), the correct answer is not "D". You’ve got to know what to do.
And how do you learn these skills? Funny you should ask.... Lab Time On Real Cisco Equipment. Again, speaking from experience: This is the most important part of getting your CCNA, succeeding on the job, and going on to get your CCNP.
Getting hands-on experience is critical to developing your networking skills, especially your troubleshooting skills. Although simulators are better than they used to be, they’re still not Cisco routers, and they never will be.
You do your best learning not only when you’re configuring your routers, but when you screw something up.
That’s so important, I want to repeat it – loudly: You do your best learning when you screw something up. Why? Because then you have to fix it that’s how you develop your troubleshooting skills. You can read about all the debug and show commands in the world, but you don’t really understand how they work until you’re figuring out why your Frame Relay connection isn’t working, or your RIP configuration isn’t working.
This is true at every level of the Cisco Learning Pyramid. I can show you the show ip protocols output or what you get when you run debug ip rip, and you might remember it for a little while. But when you use it to troubleshoot a lab configuration, you WILL remember it.
Putting your own practice lab together will also help get you over what I call "simulator question anxiety". If you spend any time on CCNA Internet forums, you’ll see discussion after discussion about these exam questions. To a certain point, this discussion is justified. The simulator questions carry more weight on your exam than any other question while you can earn partial credit on them, you’ve got to get them right or you will most likely fail the exam.
There’s no reason to be anxious about them if you’re prepared. You don’t want to be the person who walks into the testing room that’s scared to have to create a VLAN or an access list you want to be the person who walks into the testing room confident of their ability to perform any CCNA task. The best way to be that confident is to know you’ve done it – on real Cisco equipment.
There are several vendors that sell routers and switches on ebay most of them sell CCNA and CCNP kits that include all the cables and transceivers that you’ll need as well. (And how is a simulator going to help you learn about cables and transceivers?) Keep in mind that you can always sell the equipment after you’re done with the CCNA, or you can add a little equipment to it to go after your CCNP.
Whichever of these methods you use (and I hope you’ll use all of them), make sure to keep them in balance with each other. Don’t depend too much on just one.
On the topic of learning how to troubleshoot… as you run labs on your Cisco equipment, you’ll run into questions or problems that you don’t know the answer to yet. Get used to using Google (or your favorite search engine) to find the answer to these problems - but try to figure it our yourself first!
There’s nothing wrong with asking questions of someone else if you’re not able to find the answer yourself. Trying to find the answer yourself is another important troubleshooting skill you need to start developing today. Don’t be one of these people who posts a simple question on a forum without trying to find the answer on your own. Besides, you get more satisfaction and build more confidence when you determine the answer yourself.
You’ve scheduled your exam you’ve created a document to track your study time you’ve planned exactly when you’re going to study. Now the plan must be carried out, without exception.
What exceptions do I mean? Cell phones. Televisions. IPods. Significant others. The list can go on and on.
It’s one thing to have a plan, and an important thing now you’ve got to make sure you carry it out to its fullest potential. That’s easy to say until you’re studying and a friend calls, or you remember that TV show you wanted to watch is on tonight, or you start surfing the Web for Cisco information and end up playing a game.
You MUST make these small sacrifices in order to achieve your main goal, the CCNA. Any worthwhile accomplishment requires some small sacrifice.
TV will be there when you’re done studying. Your significant other will be there when you’re done studying. And believe it or not, people once existed without cell phones! Turn the phone off. Turn your instant messenger service off. Turn your text pager off. Despite what we think, the world can do without communicating with us for 90 minutes. Remember, it’s better to have 90 minutes of great study than 180 minutes of constantly interrupted study. Studies show that while a single phone call causes an 11-minute interruption on average, it takes well over 20 minutes to get back to what you were doing with the proper mental focus. This is true at the office and at your home!
How To Spend Your Study Time CCNA candidates generally spend their time split between book study, practice exams, and lab time on real Cisco equipment. The best study is done by a combination of these, not by overly relying on one. Let’s take a look at each method.
Book study – I’ve never understood why some people (usually the trolls we were talking about earlier) talk about book study like it’s a bad thing. "You can’t learn about technology from books." What a load of manure. You have to learn the theory before you can understand how a router or switch operates. The best way to learn the theory is to read a good book.
At the CCNA level, you doubtless know that you have dozens of choices when it comes to books. Some of the better-known books really do gloss over some important topics, such as binary math and subnetting. Make sure to pick a book or books that go beyond just explaining the theory and that give you a lot of explanation of router configs and real-world examples as well.
Practice Exams: Practice exams are good in moderation, but don’t use them as your main focus of study. Occasionally, I’m asked for study tips by candidates who have taken the exam a few times and not passed yet. I ask them what they’re doing to prepare, and they give a list of companies they bought practice exams from. (You see a lot of this on Internet forums as well.)
Don’t fall into this trap. Practice exams are fine if used as a readiness check, but some candidates just take them over and over again, which renders them basically useless.
On top of that, some of them cost hundreds of dollars. That’s money you’d be much better off spending on Cisco equipment to practice on.
Again, I’m not against practice exams as a supplement to your studies. Just don’t make them the main focus of your study. Taking practice exams over and over and hoping the exam will be just like the practice exam is a recipe for disaster. As I tell my students, when you’re in front of a rack of routers and switches during a job interview (or at 2AM when you’ve been called in to fix a problem), the correct answer is not "D". You’ve got to know what to do.
And how do you learn these skills? Funny you should ask.... Lab Time On Real Cisco Equipment. Again, speaking from experience: This is the most important part of getting your CCNA, succeeding on the job, and going on to get your CCNP.
Getting hands-on experience is critical to developing your networking skills, especially your troubleshooting skills. Although simulators are better than they used to be, they’re still not Cisco routers, and they never will be.
You do your best learning not only when you’re configuring your routers, but when you screw something up.
That’s so important, I want to repeat it – loudly: You do your best learning when you screw something up. Why? Because then you have to fix it that’s how you develop your troubleshooting skills. You can read about all the debug and show commands in the world, but you don’t really understand how they work until you’re figuring out why your Frame Relay connection isn’t working, or your RIP configuration isn’t working.
This is true at every level of the Cisco Learning Pyramid. I can show you the show ip protocols output or what you get when you run debug ip rip, and you might remember it for a little while. But when you use it to troubleshoot a lab configuration, you WILL remember it.
Putting your own practice lab together will also help get you over what I call "simulator question anxiety". If you spend any time on CCNA Internet forums, you’ll see discussion after discussion about these exam questions. To a certain point, this discussion is justified. The simulator questions carry more weight on your exam than any other question while you can earn partial credit on them, you’ve got to get them right or you will most likely fail the exam.
There’s no reason to be anxious about them if you’re prepared. You don’t want to be the person who walks into the testing room that’s scared to have to create a VLAN or an access list you want to be the person who walks into the testing room confident of their ability to perform any CCNA task. The best way to be that confident is to know you’ve done it – on real Cisco equipment.
There are several vendors that sell routers and switches on ebay most of them sell CCNA and CCNP kits that include all the cables and transceivers that you’ll need as well. (And how is a simulator going to help you learn about cables and transceivers?) Keep in mind that you can always sell the equipment after you’re done with the CCNA, or you can add a little equipment to it to go after your CCNP.
Whichever of these methods you use (and I hope you’ll use all of them), make sure to keep them in balance with each other. Don’t depend too much on just one.
On the topic of learning how to troubleshoot… as you run labs on your Cisco equipment, you’ll run into questions or problems that you don’t know the answer to yet. Get used to using Google (or your favorite search engine) to find the answer to these problems - but try to figure it our yourself first!
There’s nothing wrong with asking questions of someone else if you’re not able to find the answer yourself. Trying to find the answer yourself is another important troubleshooting skill you need to start developing today. Don’t be one of these people who posts a simple question on a forum without trying to find the answer on your own. Besides, you get more satisfaction and build more confidence when you determine the answer yourself.
Wednesday, December 24, 2008
Cisco CCNA Certification Exam Tutorial: The OSI Model’s Physical Layer
To pass your CCNA exam and earn this coveted certification, you've got to master the seven layers of the OSI model and what each layer does. For those of you taking the two-exam path, you can expect quite a few OSI model questions on the Intro exam. In this seven-part series, we'll spend some time taking a look at each of the OSI model layers, starting with the Physical layer.
Often, CCNA candidates ask if the OSI model has any practical uses for network administrators. I used to wonder the same thing, and I can now tell you that the answer is definitely yes!
The OSI model isn't something you want to memorize and then forget about, as using the OSI model gives you a structured approach for troubleshooting. Whenever a network device isn't working properly, I always say to "start at the physical layer". The Physical layer is Layer One of the OSI model, and this is where troubleshooting should always start. Is the device on? Is it properly connected? If everything is fine at Layer One, you just move up to Layer Two, and continue in this structured fashion until the problem is identified.
The Physical layer is the layer at which bits are transmitted over the physical media. There is no routing or switching going on at this layer. The data has been broken down into more manageable pieces until the data takes the form of ones and zeroes at the Physical layer.
Even though there's no routing or switching at the Physical layer, CCNA candidates should be familiar with a couple of network devices that work at Layer One. A repeater is a device that regenerates an electrical signal, allowing the signal to travel longer distances without fading. (The process of an electrical signal gradually fading in strength over distance is "attenuation".) A hub is basically a multiport repeater, and both of these devices are considered Physical layer devices. Ethernet and Token Ring both operate at the Physical layer as well.
Learning the OSI model's Physical layer isn't just important in your CCNA exam studies, it's the first step in any network troubleshooting. After all, your network's end users are going to have a tough time sending print jobs to a printer that's turned off!
Often, CCNA candidates ask if the OSI model has any practical uses for network administrators. I used to wonder the same thing, and I can now tell you that the answer is definitely yes!
The OSI model isn't something you want to memorize and then forget about, as using the OSI model gives you a structured approach for troubleshooting. Whenever a network device isn't working properly, I always say to "start at the physical layer". The Physical layer is Layer One of the OSI model, and this is where troubleshooting should always start. Is the device on? Is it properly connected? If everything is fine at Layer One, you just move up to Layer Two, and continue in this structured fashion until the problem is identified.
The Physical layer is the layer at which bits are transmitted over the physical media. There is no routing or switching going on at this layer. The data has been broken down into more manageable pieces until the data takes the form of ones and zeroes at the Physical layer.
Even though there's no routing or switching at the Physical layer, CCNA candidates should be familiar with a couple of network devices that work at Layer One. A repeater is a device that regenerates an electrical signal, allowing the signal to travel longer distances without fading. (The process of an electrical signal gradually fading in strength over distance is "attenuation".) A hub is basically a multiport repeater, and both of these devices are considered Physical layer devices. Ethernet and Token Ring both operate at the Physical layer as well.
Learning the OSI model's Physical layer isn't just important in your CCNA exam studies, it's the first step in any network troubleshooting. After all, your network's end users are going to have a tough time sending print jobs to a printer that's turned off!
Cisco CCNA Certification Exam Tutorial: Prefix Notation
When you're preparing to pass the CCNA exam and earn this coveted Cisco certification, you've got to be totally prepared for the many kinds of binary and subnetting questions Cisco may throw at you. You also have to be familiar with the different manners in which a subnet mask can be expressed, as in the following:
255.255.255.0
/24
Believe it or not, those two values are exactly the same. The first mask is written out in the more familiar dotted decimal format, and you know by looking at those first three octets that every bit is set to "1", since the maximum value of such an octet is 255.
The second value represents the exact same mask, only this value is expressed in prefix notation. This particular value would be pronounced "slash twenty-four", and the 24 represents the number of consecutive ones that are set in the subnet mask.
Those of us who hate to type numbers are particularly appreciative of this, since it means you'll have to type a lot less numbers to represent a subnet mask. In addition, it's a lot easier to discuss masks in prefix notation than dotted decimal. ("I thought about using a two-fifty-five two-fifty-five two-fifty-five zero mask ,but then decided to use a two-fifty-five two-fifty-five two-fifty-five one-twenty-eight mask...")
Be sure you're comfortable with prefix notation before taking your CCNA exam. As with Cisco documentation, you'll most likely see masks expressed in both dotted decimal and prefix notation, and you've got to be ready to use the both as well!
255.255.255.0
/24
Believe it or not, those two values are exactly the same. The first mask is written out in the more familiar dotted decimal format, and you know by looking at those first three octets that every bit is set to "1", since the maximum value of such an octet is 255.
The second value represents the exact same mask, only this value is expressed in prefix notation. This particular value would be pronounced "slash twenty-four", and the 24 represents the number of consecutive ones that are set in the subnet mask.
Those of us who hate to type numbers are particularly appreciative of this, since it means you'll have to type a lot less numbers to represent a subnet mask. In addition, it's a lot easier to discuss masks in prefix notation than dotted decimal. ("I thought about using a two-fifty-five two-fifty-five two-fifty-five zero mask ,but then decided to use a two-fifty-five two-fifty-five two-fifty-five one-twenty-eight mask...")
Be sure you're comfortable with prefix notation before taking your CCNA exam. As with Cisco documentation, you'll most likely see masks expressed in both dotted decimal and prefix notation, and you've got to be ready to use the both as well!
Cisco CCNA Certification Exam Tutorial: OSPF Hub-And-Spoke
CCNA certification demands that you master the basics of OSPF, and for many studying for the CCNA exam, their first exposure to OSPF is a hub-and-spoke configuration. That's a tough way to get started, because a hub-and-spoke configuration built over an NBMA technology such as Frame Relay requires quite a bit of attention to detail. Let's take a quick look at several common OSPF configuration errors and how to avoid them on your CCNA test.
Make sure the hub is the designated router and that there are no backup designated routers. This is done by setting the OSPF interface priority to zero on the spoke routers. This not only ensures that the hub wins the DR election with its default OSPF interface priority of 1, but it prevents the spokes from ever having a chance to become the DR or BDR.
Configure neighbor statements on the hub. Since we're dealing with an NBMA network, the hub cannot dynamically discover its neighbors. Neighbor statements are not needed on the spokes. (They don't hurt anything, but they don't do anything, either.)
Finally, if your OSPF adjacencies do not form as expected, make sure to use your OSI model knowledge to approach the problem. The issue may actually be at Layer Two, with your Frame Relay configuration. If you don't use the "broadcast" option on your frame relay statements, OSPF hellos will not be transmitted successfully between potential neighbors. OSPF hellos are multicast, but the "broadcast" option for Frame Relay includes multicasts.
By paying special attention to these details, you're that much close to CCNA exam day success and earning your certification. I recommend that you get some experience with configuring OSPF hub-and-spoke before taking the CCNA exam, because it’s by actually performing tasks such as this that makes you supremely confident on CCNA test day.
Make sure the hub is the designated router and that there are no backup designated routers. This is done by setting the OSPF interface priority to zero on the spoke routers. This not only ensures that the hub wins the DR election with its default OSPF interface priority of 1, but it prevents the spokes from ever having a chance to become the DR or BDR.
Configure neighbor statements on the hub. Since we're dealing with an NBMA network, the hub cannot dynamically discover its neighbors. Neighbor statements are not needed on the spokes. (They don't hurt anything, but they don't do anything, either.)
Finally, if your OSPF adjacencies do not form as expected, make sure to use your OSI model knowledge to approach the problem. The issue may actually be at Layer Two, with your Frame Relay configuration. If you don't use the "broadcast" option on your frame relay statements, OSPF hellos will not be transmitted successfully between potential neighbors. OSPF hellos are multicast, but the "broadcast" option for Frame Relay includes multicasts.
By paying special attention to these details, you're that much close to CCNA exam day success and earning your certification. I recommend that you get some experience with configuring OSPF hub-and-spoke before taking the CCNA exam, because it’s by actually performing tasks such as this that makes you supremely confident on CCNA test day.
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