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!
Showing posts with label how. Show all posts
Showing posts with label how. Show all posts
Friday, December 26, 2008
Thursday, December 25, 2008
Cisco CCNA Exam Tutorial: Loopback Interfaces
As a CCNA candidate, you most likely have some background in PC hardware and workstation support. If so, you're already familiar with loopback interfaces, particularly 127.0.0.1, the loopback address assigned to a PC.
When you're learning all about the different physical interfaces for your CCNA exam - serial, ethernet, and BRI, among others - there's one logical interface you need to know about, and that is - you guessed it! - the loopback interface.
What isn't as immediately apparent is why we use loopback interfaces on routers and switches to begin with. Many of the Cisco router features that can use loopbacks are intermediate and advanced features that you'll learn about in your CCNP and CCIE studies, but these features all come back to one basic concept: If the loopback interface on a router is down, that means the router is unavailable as a whole.
In contrast, a physical interface being down does not mean the router itself is out of commission. A router's ethernet port can go down, but the other physical interfaces on that router are still operational. Since a loopback interface is logical, there's nothing physical that can go wrong with it.
As I mentioned, you'll learn different Cisco router and switch features that utilize loopback interfaces as you climb the Cisco certification ladder. There's one misconception about Cisco loopback interfaces that you want to get clear on now, though. You’re probably familiar with loopback interfaces on a PC, and may even know that the address range 127.0.0.0 is reserved for loopback addressing.
Note that this reserved address range does not apply to loopbacks on Cisco devices, however. If you attempt to assign an address from this range to a Cisco loopback interface, you get this result:
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#interface loopback0
R1(config-if)#ip address 127.0.0.2 255.255.255.0
Not a valid host address - 127.0.0.2
R1(config-if)#ip address 127.1.1.1 255.255.255.0
Not a valid host address - 127.1.1.1
The range 127.0.0.0 is reserved for host loopbacks (such as PCs), not routers or switches. The most commonly used address from this range is 127.0.0.1 – if you can’t ping that on a workstation, that means you can’t ping yourself, which means there’s a problem with the TCP/IP install itself.
Keep these details in mind on the exam and in the workplace, and you’re on your way to CCNA exam success!
When you're learning all about the different physical interfaces for your CCNA exam - serial, ethernet, and BRI, among others - there's one logical interface you need to know about, and that is - you guessed it! - the loopback interface.
What isn't as immediately apparent is why we use loopback interfaces on routers and switches to begin with. Many of the Cisco router features that can use loopbacks are intermediate and advanced features that you'll learn about in your CCNP and CCIE studies, but these features all come back to one basic concept: If the loopback interface on a router is down, that means the router is unavailable as a whole.
In contrast, a physical interface being down does not mean the router itself is out of commission. A router's ethernet port can go down, but the other physical interfaces on that router are still operational. Since a loopback interface is logical, there's nothing physical that can go wrong with it.
As I mentioned, you'll learn different Cisco router and switch features that utilize loopback interfaces as you climb the Cisco certification ladder. There's one misconception about Cisco loopback interfaces that you want to get clear on now, though. You’re probably familiar with loopback interfaces on a PC, and may even know that the address range 127.0.0.0 is reserved for loopback addressing.
Note that this reserved address range does not apply to loopbacks on Cisco devices, however. If you attempt to assign an address from this range to a Cisco loopback interface, you get this result:
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#interface loopback0
R1(config-if)#ip address 127.0.0.2 255.255.255.0
Not a valid host address - 127.0.0.2
R1(config-if)#ip address 127.1.1.1 255.255.255.0
Not a valid host address - 127.1.1.1
The range 127.0.0.0 is reserved for host loopbacks (such as PCs), not routers or switches. The most commonly used address from this range is 127.0.0.1 – if you can’t ping that on a workstation, that means you can’t ping yourself, which means there’s a problem with the TCP/IP install itself.
Keep these details in mind on the exam and in the workplace, and you’re on your way to CCNA exam success!
Wednesday, December 24, 2008
Cisco CCNA Exam Tutorial: CCNA Recertification Requirements
Passing the CCNA exam and earning this coveted Cisco certification is an important step in your career, but it's not the end of your responsibilities as a CCNA! When you work with computer networks, you've got to be continually learning and staying up on the latest technologies and changes in the field. Part of this responsibility is keeping your CCNA current by meeting Cisco's recertification requirements.
Cisco requires CCNAs to recertify once every three years. While most CCNAs will move on to the CCNP in that time, if you choose not to you must meet certain requirements in order to keep your CCNA valid. Cisco does this to ensure that CCNAs keep their networking knowledge current, which in turn helps the CCNA certification valuable. And that's exactly what you want, since you worked so hard to earn your certification in the first place!
As of March 2006, there are five different options for recertifying as a CCNA. You can take and pass any of the following exams to renew your CCNA - the CCNA exam itself, the ICND exam, any 642 series exam, any Cisco Qualiied Specialist exam (except the Sales Specialist exams - those don't count!), or any CCIE Written Qualification exam.
With all these options, there's an option that's just right for you. Whether you just want to renew your CCNA or pursue a Specialist, CCNP, or CCIE certification, you can easily renew your CCNA along the way. Just don't forget that keeping up with Cisco's latest recertification requirements is your responsibility, and that's easy to do - just visit Cisco's "Learning And Events" section on their website. Cisco will tell you what you need to do to keep your certification, but it's up to you to keep up with certification program changes! Once your certification expires, it’s gone, so get in the habit of visiting Cisco’s website to make sure you’re up to date on important recertification requirements.
Cisco requires CCNAs to recertify once every three years. While most CCNAs will move on to the CCNP in that time, if you choose not to you must meet certain requirements in order to keep your CCNA valid. Cisco does this to ensure that CCNAs keep their networking knowledge current, which in turn helps the CCNA certification valuable. And that's exactly what you want, since you worked so hard to earn your certification in the first place!
As of March 2006, there are five different options for recertifying as a CCNA. You can take and pass any of the following exams to renew your CCNA - the CCNA exam itself, the ICND exam, any 642 series exam, any Cisco Qualiied Specialist exam (except the Sales Specialist exams - those don't count!), or any CCIE Written Qualification exam.
With all these options, there's an option that's just right for you. Whether you just want to renew your CCNA or pursue a Specialist, CCNP, or CCIE certification, you can easily renew your CCNA along the way. Just don't forget that keeping up with Cisco's latest recertification requirements is your responsibility, and that's easy to do - just visit Cisco's "Learning And Events" section on their website. Cisco will tell you what you need to do to keep your certification, but it's up to you to keep up with certification program changes! Once your certification expires, it’s gone, so get in the habit of visiting Cisco’s website to make sure you’re up to date on important recertification requirements.
Cisco CCNA Certification Exam: Five Frame Relay Details You Must Know
When you're studying for your CCNA exam on the way to earning this coveted Cisco certification, the details can seem overwhelming! In this article, I'll point out five Frame Relay details that you must keep in mind when you're on your way to the CCNA exam!
Inverse ARP starts working as soon as you open the serial interface. This protocol performs dynamic Frame Relay mapping, but you don't have to enable it - it's already enabled as soon as you enter the command "encapsulation frame-relay".
When you're configuring Frame Relay map statements manually, remember that you're mapping the local DLCI to the remote IP address.
When you run "show frame map", the word "dynamic" indicates mappings created by Inverse ARP, and "static" indicates it was manually created.
To spot possible LMI type mismatches, run "show frame lmi". A large number of Status Timeouts indicates that there may be an LMI problem between your router and the frame relay switch.
This last one is for the many of you building CCNA home labs. A frame relay switch is a great addition to your lab! While you're busy putting the configuration together, don't forget the global command "frame-relay switching" - it's this command that allows a Cisco router to act as a frame relay switch!
Inverse ARP starts working as soon as you open the serial interface. This protocol performs dynamic Frame Relay mapping, but you don't have to enable it - it's already enabled as soon as you enter the command "encapsulation frame-relay".
When you're configuring Frame Relay map statements manually, remember that you're mapping the local DLCI to the remote IP address.
When you run "show frame map", the word "dynamic" indicates mappings created by Inverse ARP, and "static" indicates it was manually created.
To spot possible LMI type mismatches, run "show frame lmi". A large number of Status Timeouts indicates that there may be an LMI problem between your router and the frame relay switch.
This last one is for the many of you building CCNA home labs. A frame relay switch is a great addition to your lab! While you're busy putting the configuration together, don't forget the global command "frame-relay switching" - it's this command that allows a Cisco router to act as a frame relay switch!
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