The format and difficulty of computer certification exams is constantly changing. When I took my first certification exam (Novell NetWare 3.1x CNA, January 1997), there was no such thing as a simulator question, and my practical skills really were not tested. The exams then were much heavier on memorization.
One factor that helped make up for that was that the Novell exams were adaptive. If you missed a question on a particular topic, you would continue to be asked questions about that topic until you got it right. You couldn't afford to be weak in any topic, because the exam would most likely find that out and keep hitting you with questions on that topic until you failed.
Adding to the stress, after a certain number of questions your exam could end at any time. You had no idea how many questions you would get, just that you would get at least 15. Every time you hit the "next" button after question 15, you didn't know if you'd get another question or if the exam would suddenly end and give you a pass or fail response.
Times have changed. Cisco has led the way in introducing simulator questions to their exams, where the candidate is presented with a simulation of a router or network and asked to perform tasks that someone who is ready to earn that certification should be able to perform. This is a much better test of competency than the exams were eight years ago.
What will be the next "big jump" in computer certification exams? To earn the world's most difficult technical certification, the CCIE, the candidate must first pass a rigorous 100-question qualification exam, and must then pass a practical lab exam. The candidate is presented with an exacting set of network requirements and must build that network on a pod of Cisco routers and switches in less than eight hours.
This is just personal opinion and not "insider information", but I believe the day will come when the CCNA, CCNP, and other Cisco certifications will require some kind of hands-on practical lab to earn the certification. What better way to test competency than to have to perform tasks on real Cisco equipment? There would be more overhead for Cisco with this kind of testing, since lab equipment and lab proctors would be needed, but the already-prized CCNA and CCNP would become that much more valuable in the workplace if employers knew that to earn that certification, the job candidate had to pass a hands-on exam.
This would benefit the candidates as well, since it would do an even better job in protecting their investment in time and money. This could also be the next step in ferretting out candidates who try to get past the CCNA and CCNP exams via braindumps. As I always tell my students and customers, when you're standing in front of that router or switch, there is no multiple choice ... you either know it or you don't!
Chris Bryant
CCIE #12933
Showing posts with label nat. Show all posts
Showing posts with label nat. Show all posts
Saturday, December 27, 2008
Taking A Look At Cisco's CCVP Certification
I hardly have to tell you how important voice technologies are in today's networks; what we all need to keep in mind to maximize our career potential is how important knowing voice is going to be tomorrow.
We've always got to look forward in IT, both in our work and out studies. Cisco, always the pioneer in technical certifications, now offers a Cisco Certified Voice Professional certification that is gaining a lot of attention from IT professionals looking to add to their skills and their resume.
Cisco's CCVP track is a rigorous five-exam track that requires you to earn your CCNA (Cisco Certified Network Associate) certification before getting started. The five exams cover a myriad of topics - they're not giving this one away! Here are the exam numbers and codes you'll need to know to register for the exams:
642-642 Quality Of Service (QOS)
642-432 Cisco Voice Over IP (CVOICE)
642-425 IP Telephony Troubleshooting (IPTT)
642-444 Cisco IP Telephony (CIPT)
642-452 Cisco Voice Gateways (GWGK)
Many newly-minted CCNAs wonder if they should pursue this or the Security Professional certification immediately after getting their CCNA. I recommend that a new CCNA pursue and achieve the CCNP before going after these more-specialized certifications. While it is not required by Cisco, the routing and switching knowledge your will acquire on your way to the CCNP will be invaluable to your career as well as being helpful with your CCVP pursuits.
Besides, these certifications won't be going anywhere soon. Think of how valuable you will be with a CCNP, CCVP, and CCSP!
To your success,
Chris Bryant
CCIE #12933
We've always got to look forward in IT, both in our work and out studies. Cisco, always the pioneer in technical certifications, now offers a Cisco Certified Voice Professional certification that is gaining a lot of attention from IT professionals looking to add to their skills and their resume.
Cisco's CCVP track is a rigorous five-exam track that requires you to earn your CCNA (Cisco Certified Network Associate) certification before getting started. The five exams cover a myriad of topics - they're not giving this one away! Here are the exam numbers and codes you'll need to know to register for the exams:
642-642 Quality Of Service (QOS)
642-432 Cisco Voice Over IP (CVOICE)
642-425 IP Telephony Troubleshooting (IPTT)
642-444 Cisco IP Telephony (CIPT)
642-452 Cisco Voice Gateways (GWGK)
Many newly-minted CCNAs wonder if they should pursue this or the Security Professional certification immediately after getting their CCNA. I recommend that a new CCNA pursue and achieve the CCNP before going after these more-specialized certifications. While it is not required by Cisco, the routing and switching knowledge your will acquire on your way to the CCNP will be invaluable to your career as well as being helpful with your CCVP pursuits.
Besides, these certifications won't be going anywhere soon. Think of how valuable you will be with a CCNP, CCVP, and CCSP!
To your success,
Chris Bryant
CCIE #12933
Passing The CCNA and CCNP: Three Myths About Cisco Exams
One of the drawbacks to the Internet is that it allows myths and "friend of a friend" stories to spread quickly, and usually the story becomes more exaggerated as it's passed along. Cisco exams are no exception. Here are three often-repeated myths and exaggerations regarding the CCNA and CCNP exams.
1. The survey you fill out before the exam determines the questions you'll get. Before you actually start your exam, Cisco presents you with a survey asking how you prepared and how comfortable you feel with certain technologies. It's a little awkward to rate yourself on Frame Relay, ISDN, etc., especially since the exam you're about to take covers those subjects. It's human nature to think that these questions impact your exam, but they do not.
I've seen posts on the Net saying that if you rank yourself as "great" in a subject, your exam will have harder questions on that topic, and if you rank yourself lower in that same subject, your exam will be filled with questions on this topic. Cisco has debunked this myth, so get it out of your mind. Don't think too much when you're filling out the survey.
2. If you miss a question, the exam keeps asking you about that topic until you get one right. This is known as "adaptive testing", and Cisco does not use this kind of testing in its exams. Your questions are drawn from a large question pool before you start the test. Those of us who remember adaptive testing from Novell exams years ago don't particularly miss this kind of testing! (For those who haven't taken an adaptive exam, you never knew how many questions you were going to get, only that there was a minimum around 15 questions. Your exam could end at any time after that. Nerve-wracking!)
3. If you use an extra command in the simulator questions, it'll be marked wrong. The Cisco simulator engine in the CCNA and CCNP exams acts just as a router or switch would. You are not going to be penalized for using an extra command. If the engine doesn't accept a command, you'll be told that when you use it. Just configure it as you would a router or switch.
When you walk into the exam room totally prepared with a combination of theoretical knowledge, hands-on experience, and configuration troubleshooting skills, you are ready to pass. Don't let Internet gossip distract you from the task at hand -- passing!
1. The survey you fill out before the exam determines the questions you'll get. Before you actually start your exam, Cisco presents you with a survey asking how you prepared and how comfortable you feel with certain technologies. It's a little awkward to rate yourself on Frame Relay, ISDN, etc., especially since the exam you're about to take covers those subjects. It's human nature to think that these questions impact your exam, but they do not.
I've seen posts on the Net saying that if you rank yourself as "great" in a subject, your exam will have harder questions on that topic, and if you rank yourself lower in that same subject, your exam will be filled with questions on this topic. Cisco has debunked this myth, so get it out of your mind. Don't think too much when you're filling out the survey.
2. If you miss a question, the exam keeps asking you about that topic until you get one right. This is known as "adaptive testing", and Cisco does not use this kind of testing in its exams. Your questions are drawn from a large question pool before you start the test. Those of us who remember adaptive testing from Novell exams years ago don't particularly miss this kind of testing! (For those who haven't taken an adaptive exam, you never knew how many questions you were going to get, only that there was a minimum around 15 questions. Your exam could end at any time after that. Nerve-wracking!)
3. If you use an extra command in the simulator questions, it'll be marked wrong. The Cisco simulator engine in the CCNA and CCNP exams acts just as a router or switch would. You are not going to be penalized for using an extra command. If the engine doesn't accept a command, you'll be told that when you use it. Just configure it as you would a router or switch.
When you walk into the exam room totally prepared with a combination of theoretical knowledge, hands-on experience, and configuration troubleshooting skills, you are ready to pass. Don't let Internet gossip distract you from the task at hand -- passing!
Friday, December 26, 2008
Passing The CCNA and CCNP: Home Lab Shopping On Ebay
Whether you're just getting ideas for your Cisco home lab or adding to your existing lab, ebay is a great place to get ideas for your lab as well as pick up some great bargains.
Of course, the internet being what it is, there are always going to be a few people looking to take your money while shipping you inferior merchandise, or worse, no merchandise at all. While these "dealers" are in the minority, you still need to be careful when purchasing Cisco equipment on ebay. In this article, I'll give you several tips on browsing ebay ads for home lab ideas, and a few things to look out for when purchasing equipment on ebay.
For those of you just starting your Cisco certification pursuit, the idea of purchasing a home lab kit -- a set of routers, switches, and perhaps some cables and study guides -- seems like a good idea. Instead of putting your lab together one piece at a time, these kits allow you to get a head start on your studies.
One thing to watch out for in these kits is outdated equipment, or the inclusion of outdated study guides. Often, vendors will use these kits as a way to get rid of unwanted inventory.
The Cisco 1900 family of switches falls into this category. A recent search on ebay for "ccna lab" showed seven different CCNA lab kits that contained 1900 switches. The problem here is that the current CCNA exams do not test on the 1900 switches, which are menu-driven and do not have an IOS. You'll need to be well-versed with switches that do have an IOS, such as the 2950s.
The plus side here is that you will probably save money by using 1900 switches. If you're on a tight budget, having a 1900 switch is better than no switch at all. If at all possible, though, get a Cisco switch with an IOS.
The cables and transceivers included with these kits are generally exactly what you need to set up that particular kit, and this can be very helpful to those CCNA candidates who are new to the various cables needed to physically configure a home lab. Just make sure you're not buying a kit with 10 transceivers (used on AUI ports) when you've only got two routers with Ethernet ports.
Watch out for kits that include outdated study guides. I've seen four-year-old CCNA books included with some kits. If you already have your study guides, feel free to ask the vendor how much the kit costs without the books.
That leads me to the most important point. Get to know the vendor before buying anything. Visit their website and check their ebay feedback. If buying from an individual as opposed to a reseller, find out what conditions the router or switch has been kept in, and make sure to define the terms under which they will accept returns.
There's nothing wrong with buying equipment from someone who's selling their CCNA/CCNP/CCIE home lab, but just make sure you ask the right questions first. Professional resellers generally have their return policy right in their ebay ad; if they don't, ask for a copy.
Building your own CCNA and/or CCNP home lab is a little intimidating at first, but speaking as someone who has climbed the Cisco certification ladder from the CCNA to the CCIE, I can tell you that it is the best investment you can make in your career. Use a little caution, ask the right question, and soon you'll be leaving the world of "router simulators" behind - and you'll be developing your skills as a true professional should: On real Cisco routers and switches!
Of course, the internet being what it is, there are always going to be a few people looking to take your money while shipping you inferior merchandise, or worse, no merchandise at all. While these "dealers" are in the minority, you still need to be careful when purchasing Cisco equipment on ebay. In this article, I'll give you several tips on browsing ebay ads for home lab ideas, and a few things to look out for when purchasing equipment on ebay.
For those of you just starting your Cisco certification pursuit, the idea of purchasing a home lab kit -- a set of routers, switches, and perhaps some cables and study guides -- seems like a good idea. Instead of putting your lab together one piece at a time, these kits allow you to get a head start on your studies.
One thing to watch out for in these kits is outdated equipment, or the inclusion of outdated study guides. Often, vendors will use these kits as a way to get rid of unwanted inventory.
The Cisco 1900 family of switches falls into this category. A recent search on ebay for "ccna lab" showed seven different CCNA lab kits that contained 1900 switches. The problem here is that the current CCNA exams do not test on the 1900 switches, which are menu-driven and do not have an IOS. You'll need to be well-versed with switches that do have an IOS, such as the 2950s.
The plus side here is that you will probably save money by using 1900 switches. If you're on a tight budget, having a 1900 switch is better than no switch at all. If at all possible, though, get a Cisco switch with an IOS.
The cables and transceivers included with these kits are generally exactly what you need to set up that particular kit, and this can be very helpful to those CCNA candidates who are new to the various cables needed to physically configure a home lab. Just make sure you're not buying a kit with 10 transceivers (used on AUI ports) when you've only got two routers with Ethernet ports.
Watch out for kits that include outdated study guides. I've seen four-year-old CCNA books included with some kits. If you already have your study guides, feel free to ask the vendor how much the kit costs without the books.
That leads me to the most important point. Get to know the vendor before buying anything. Visit their website and check their ebay feedback. If buying from an individual as opposed to a reseller, find out what conditions the router or switch has been kept in, and make sure to define the terms under which they will accept returns.
There's nothing wrong with buying equipment from someone who's selling their CCNA/CCNP/CCIE home lab, but just make sure you ask the right questions first. Professional resellers generally have their return policy right in their ebay ad; if they don't, ask for a copy.
Building your own CCNA and/or CCNP home lab is a little intimidating at first, but speaking as someone who has climbed the Cisco certification ladder from the CCNA to the CCIE, I can tell you that it is the best investment you can make in your career. Use a little caution, ask the right question, and soon you'll be leaving the world of "router simulators" behind - and you'll be developing your skills as a true professional should: On real Cisco routers and switches!
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: 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!
Cisco Routing For The CCNA And CCNP: Administrative Distance
The textbook definition of "administrative distance" is simple enough: "the measurement of a protocol's believability". It's not enough to know the definition, however you've got to know when AD comes into the picture and when it does not.
When a packet needs to be routed, the router looks in its routing table for the next-hop IP address the packet should take to get to the destination. There may be more than one matching path, in which case the router will look for the "longest match". The route that has the longest match - the route with the most bits in the mask set to "1" - will be the route that is used.
Consider the following three routes from a fictional Cisco router:
I 172.17.0.0 /24 via 172.1.1.1
O 172.17.0.0 /25 via 173.1.1.1
R 172.17.0.0 /26 via 174.1.1.1
This router has three possible next-hop IP addresses that it can send packets destined for the network 172.17.0.0. The masks are of different lengths, meaning that the route with the longest match (again, the route with the most bits set to "1") will be used. In this example, the RIP route will be used, since it has the longest match with a mask of /26. The administrative distances do not matter.
AD does matter when the masks are the same length, as shown here:
I 172.17.0.0 /24 via 172.1.1.1
O 172.17.0.0 /24 via 173.1.1.1
R 172.17.0.0 /24 via 174.1.1.1
The longest match rule always precedes the use of AD, but here there is a three-way tie regarding the masks. They're all /24 (or 255.255.255.0 in dotted decimal). AD will be used to break this tie.
As mentioned, AD is a measurement of a protocol's believability. It is important to keep in mind that the lowest AD will be preferred. And while the routing table will show you the ADs of the respective protocols, it's a very good idea to know these ADs before taking the CCNA or CCNP:
Connected route: 0
Static Route: 1
EIGRP Summary: 5
External BGP: 20
EIGRP (Internal): 90
IGRP: 100
OSPF: 110
ISIS : 115
RIP: 120
EIGRP (External) : 170
Unknown: 255 (A router will not believe a source with an AD of 255, and such routes will not be placed into the routing table.)
The three protocols we looked at in the comparison were RIP, IGRP, and OSPF. While your first instinct may be that the OSPF route would be the most believable, IGRP actually has a lower AD than the other two and would be the route installed in the routing table.
Since IGRP does not support variable-length subnet masking and OSPF does, you may never see this scenario outside of an exam question. But if you do see it in the exam room or in a production network, you'll understand how an IGRP route could be preferred over an OSPF route.
When a packet needs to be routed, the router looks in its routing table for the next-hop IP address the packet should take to get to the destination. There may be more than one matching path, in which case the router will look for the "longest match". The route that has the longest match - the route with the most bits in the mask set to "1" - will be the route that is used.
Consider the following three routes from a fictional Cisco router:
I 172.17.0.0 /24 via 172.1.1.1
O 172.17.0.0 /25 via 173.1.1.1
R 172.17.0.0 /26 via 174.1.1.1
This router has three possible next-hop IP addresses that it can send packets destined for the network 172.17.0.0. The masks are of different lengths, meaning that the route with the longest match (again, the route with the most bits set to "1") will be used. In this example, the RIP route will be used, since it has the longest match with a mask of /26. The administrative distances do not matter.
AD does matter when the masks are the same length, as shown here:
I 172.17.0.0 /24 via 172.1.1.1
O 172.17.0.0 /24 via 173.1.1.1
R 172.17.0.0 /24 via 174.1.1.1
The longest match rule always precedes the use of AD, but here there is a three-way tie regarding the masks. They're all /24 (or 255.255.255.0 in dotted decimal). AD will be used to break this tie.
As mentioned, AD is a measurement of a protocol's believability. It is important to keep in mind that the lowest AD will be preferred. And while the routing table will show you the ADs of the respective protocols, it's a very good idea to know these ADs before taking the CCNA or CCNP:
Connected route: 0
Static Route: 1
EIGRP Summary: 5
External BGP: 20
EIGRP (Internal): 90
IGRP: 100
OSPF: 110
ISIS : 115
RIP: 120
EIGRP (External) : 170
Unknown: 255 (A router will not believe a source with an AD of 255, and such routes will not be placed into the routing table.)
The three protocols we looked at in the comparison were RIP, IGRP, and OSPF. While your first instinct may be that the OSPF route would be the most believable, IGRP actually has a lower AD than the other two and would be the route installed in the routing table.
Since IGRP does not support variable-length subnet masking and OSPF does, you may never see this scenario outside of an exam question. But if you do see it in the exam room or in a production network, you'll understand how an IGRP route could be preferred over an OSPF route.
Cisco Certification: Introduction To ISDN
From the CCNA to the CCIE, ISDN is one of the most important technolgies you'll work with. It's also very common in the field ISDN is frequently used as a backup connection in case an organization's Frame Relay connections go down. Therefore, it's important to know ISDN basics not only for your particular exam, but for job success.
ISDN is used between two Cisco routers that have BRI or PRI interfaces. Basically, with ISDN one of the routers places a phone call to the other router. It is vital to understand not only what causes one router to dial another, but what makes the link go down.
Why? Since ISDN is basically a phone call from one router to another, you're getting billed for that phone call -- by the minute. If one of your routers dials another, and never hangs up, the connection can theoretically last for days or weeks. The network manager then receives an astronomical phone bill, which leads to bad things for everyone involved!
Cisco routers use the concept of interesting traffic to decide when one router should call another. By default, there is no interesting traffic, so if you don't define any, the routers will never call each other.
Interesting traffic is defined with the dialer-list command. This command offers many options, so you can tie interesting traffic down not only to what protocols can bring the link up, but what the source, destination, or even port number must be for the line to come up.
One common misconception occurs once that link is up. Interesting traffic is required to bring the link up, but by default, any traffic can then cross the ISDN link.
What makes the link come down? Again, the concept of interesting traffic is used. Cisco routers have an idle-timeout setting for their dialup interfaces. If interesting traffic does not cross the link for the amount of time specified by the idle-timeout, the link comes down.
To summarize: Interesting traffic brings the link up by default, any traffic can cross the link once it's up a lack of interesting traffic is what brings the link down.
Just as important is knowing what keeps the link up once it is dialed. Why? Because ISDN acts as a phone call between two routers, and it’s billed that way to your client. The two routers that are connected by this phone call may be located in different area codes, so now we’re talking about a long distance phone call.
If your ISDN link does not have a reason to disconnect, the connection could theoretically last for days or weeks before someone realizes what’s going on. This is particularly true when the ISDN link is used as a backup for another connection type, as is commonly the case with Frame Relay. When the Frame Relay goes down, the backup ISDN link comes up when the Frame Relay link comes back not billed for all that time.
To understand why an ISDN link stays up when it’s not needed, we have to understand why it stays up period. Cisco’s ISDN interfaces use the idle-timeout to determine when an ISDN link should be torn down. By default, this value is two minutes, and it also uses the concept of interesting traffic.
Once interesting traffic brings the link up, by default all traffic can cross the link. However, only interesting traffic resets the idle-timeout. If no interesting traffic crosses the link for two minutes, the idle-timer hits zero and the link comes down.
If the protocol running over the ISDN link is RIP version 2 or EIGRP, the most efficient way to prevent the routing updates from keeping the line up is expressly prohibiting their multicast routing update address in the access-list that is defining interesting traffic. Do not prevent them from crossing the link entirely, or the protocol obviously won’t work correctly.
With OSPF, Cisco offers the ip ospf demand-circuit interface-level command. The OSPF adjacency will form over the ISDN link, but once formed, the Hello packets will be suppressed. However, the adjacency will not be lost. A check of the adjacency table with show ip ospf adjacency will show the adjacency remains at Full, even though Hellos are no longer being sent across the link. The ISDN link can drop without the adjacency being lost. When the link is needed, the adjacency is still in place and data can be sent without waiting for OSPF to go through the usual steps of forming an adjacency.
This OSPF command is vital for Cisco certification candidates at every level, but is particularly important for CCNA candidates. Learn this command now, get used to the fact that the adjacency stays up even though Hellos are suppressed, and add this valuable command to your Cisco toolkit.
One myth about ISDN is that Cisco Discovery Packets keep an ISDN link up. CDP is a Cisco-proprietary protocol that runs between directly connected Cisco devices. There is a school of thought that CDP packets have to be disabled on a BRI interface in order to prevent the link from staying up or dialing when it's not really needed. I've worked with ISDN for years in the field and in the lab, and I've never seen CDP bring up an ISDN link. Try it yourself the next time you're working on a practice rack!
Chris Bryant
CCIE #12933
ISDN is used between two Cisco routers that have BRI or PRI interfaces. Basically, with ISDN one of the routers places a phone call to the other router. It is vital to understand not only what causes one router to dial another, but what makes the link go down.
Why? Since ISDN is basically a phone call from one router to another, you're getting billed for that phone call -- by the minute. If one of your routers dials another, and never hangs up, the connection can theoretically last for days or weeks. The network manager then receives an astronomical phone bill, which leads to bad things for everyone involved!
Cisco routers use the concept of interesting traffic to decide when one router should call another. By default, there is no interesting traffic, so if you don't define any, the routers will never call each other.
Interesting traffic is defined with the dialer-list command. This command offers many options, so you can tie interesting traffic down not only to what protocols can bring the link up, but what the source, destination, or even port number must be for the line to come up.
One common misconception occurs once that link is up. Interesting traffic is required to bring the link up, but by default, any traffic can then cross the ISDN link.
What makes the link come down? Again, the concept of interesting traffic is used. Cisco routers have an idle-timeout setting for their dialup interfaces. If interesting traffic does not cross the link for the amount of time specified by the idle-timeout, the link comes down.
To summarize: Interesting traffic brings the link up by default, any traffic can cross the link once it's up a lack of interesting traffic is what brings the link down.
Just as important is knowing what keeps the link up once it is dialed. Why? Because ISDN acts as a phone call between two routers, and it’s billed that way to your client. The two routers that are connected by this phone call may be located in different area codes, so now we’re talking about a long distance phone call.
If your ISDN link does not have a reason to disconnect, the connection could theoretically last for days or weeks before someone realizes what’s going on. This is particularly true when the ISDN link is used as a backup for another connection type, as is commonly the case with Frame Relay. When the Frame Relay goes down, the backup ISDN link comes up when the Frame Relay link comes back not billed for all that time.
To understand why an ISDN link stays up when it’s not needed, we have to understand why it stays up period. Cisco’s ISDN interfaces use the idle-timeout to determine when an ISDN link should be torn down. By default, this value is two minutes, and it also uses the concept of interesting traffic.
Once interesting traffic brings the link up, by default all traffic can cross the link. However, only interesting traffic resets the idle-timeout. If no interesting traffic crosses the link for two minutes, the idle-timer hits zero and the link comes down.
If the protocol running over the ISDN link is RIP version 2 or EIGRP, the most efficient way to prevent the routing updates from keeping the line up is expressly prohibiting their multicast routing update address in the access-list that is defining interesting traffic. Do not prevent them from crossing the link entirely, or the protocol obviously won’t work correctly.
With OSPF, Cisco offers the ip ospf demand-circuit interface-level command. The OSPF adjacency will form over the ISDN link, but once formed, the Hello packets will be suppressed. However, the adjacency will not be lost. A check of the adjacency table with show ip ospf adjacency will show the adjacency remains at Full, even though Hellos are no longer being sent across the link. The ISDN link can drop without the adjacency being lost. When the link is needed, the adjacency is still in place and data can be sent without waiting for OSPF to go through the usual steps of forming an adjacency.
This OSPF command is vital for Cisco certification candidates at every level, but is particularly important for CCNA candidates. Learn this command now, get used to the fact that the adjacency stays up even though Hellos are suppressed, and add this valuable command to your Cisco toolkit.
One myth about ISDN is that Cisco Discovery Packets keep an ISDN link up. CDP is a Cisco-proprietary protocol that runs between directly connected Cisco devices. There is a school of thought that CDP packets have to be disabled on a BRI interface in order to prevent the link from staying up or dialing when it's not really needed. I've worked with ISDN for years in the field and in the lab, and I've never seen CDP bring up an ISDN link. Try it yourself the next time you're working on a practice rack!
Chris Bryant
CCIE #12933
Wednesday, December 24, 2008
Cisco CCNA / CCNP Home Lab Tutorial: Buying And Configuring An Access Server
A Cisco access server is generally the last item a CCNA or CCNP candidate has on their mind when they're putting together a home lab. The thinking tends to be that since this router isn't really doing anything in the production part of your practice lab, it's not really important.
Once you have more than two devices in your home lab, though, you'll realize that constantly moving the console cable around from one router to another gets very tiresome. That's what an access server does for a home lab - it allows you to connect your PC to a single device when working in your home lab, with no need to constantly disconnect and reconnect the console cable. The console cable will be connected directly to the access server, and the access server is connected to all the other devices in your home lab. Once you start working with one, you'll wonder how you got along without it!
The term "access server" is a little misleading. This is not a server in the traditional sense, it's a Cisco router with asynchronous serial ports. It is these ports that you'll use to connect to the other devices in your home lab. Two affordable models of access servers are Cisco 2509s and Cisco 2511s. They can be found on ebay as well as other vendors on the Net.
You will also need an octal cable. On one end, the cable has a large connector that will connect to the access server. The other end is actually eight separate cables, each with RJ-45 connectors. These connectors are numbered 1 - 8 and will be connected to the console port on each router and switch. It is important to note the number on each connector you're connecting to the other lab devices.
Now that you've got the physical equipment, let's take a look at a typical configuration of an access server:
no service password-encryption
no service udp-small-servers
no service tcp-small-servers
! hostname BRYANT_ADVANTAGE_AS4
no ip domain-lookup
ip host r1 2001 10.4.4.4
ip host r2 2002 10.4.4.4
ip host r3 2003 10.4.4.4
ip host sw1 2004 10.4.4.4
ip host sw2 2005 10.4.4.4
ip host FrameSwitch 2006 10.4.4.4
interface Loopback555
ip address 10.4.4.4 255.255.255.0
line con 0
exec-timeout 0 0
logging synchronous\
line 1 16
no exec
transport input all
You can assign any loopback address and number here the important thing to note is that the IP HOST table you will build constantly refers back to the loopback address on the access server.
In this configuration, I have the octal cable's connector 1 in R1, 2 in R2, 3 in R3, 4 in SW1, 5 in SW2, and 6 in my frame relay switch. The number "2001" in the first line of the IP HOST table refers to that connector. That's why it is important to note the number on a given connector you place in the console port of a router or switch.
The asynchonous lines are identified by "line 1 16". This access server has 16 possible connections many will just have 8, which is usually plenty. Regardless of how many lines you have, you'll need the commands transport input all and no exec to allow reverse telnet to work effectively.
There's one more thing to watch out for. When you first connect to the AS for a practice session, you will need to open the line to each device by using the full hostname of the device as shown in the IP HOST table. Here, you would begin by entering R1, R2, R3, SW1, SW2, and FrameSwitch to open the line to each device. After that, you need to enter the line number - 1, 2, 3, 4, 5, and 6. It sounds a little confusing at first, but after just a few minutes of practice you'll be doing it without even thinking about it.
When you are working in your home lab, you will not go from one device to another that is, when you are done on R1 and want to configure R2, you must go back to the access server and then to R2. The keystroke to do this is . Again, it may sound complicated, but after a little practice you will again do this without thinking about it.
Adding an access server to your CCNA or CCNP home lab may not be on your mind now, but once you add a few more routers or switches to the lab, you'll want to spend more time configuring and practicing and less time moving a cable around. And once you get one, you'll wonder how you did without it!
Once you have more than two devices in your home lab, though, you'll realize that constantly moving the console cable around from one router to another gets very tiresome. That's what an access server does for a home lab - it allows you to connect your PC to a single device when working in your home lab, with no need to constantly disconnect and reconnect the console cable. The console cable will be connected directly to the access server, and the access server is connected to all the other devices in your home lab. Once you start working with one, you'll wonder how you got along without it!
The term "access server" is a little misleading. This is not a server in the traditional sense, it's a Cisco router with asynchronous serial ports. It is these ports that you'll use to connect to the other devices in your home lab. Two affordable models of access servers are Cisco 2509s and Cisco 2511s. They can be found on ebay as well as other vendors on the Net.
You will also need an octal cable. On one end, the cable has a large connector that will connect to the access server. The other end is actually eight separate cables, each with RJ-45 connectors. These connectors are numbered 1 - 8 and will be connected to the console port on each router and switch. It is important to note the number on each connector you're connecting to the other lab devices.
Now that you've got the physical equipment, let's take a look at a typical configuration of an access server:
no service password-encryption
no service udp-small-servers
no service tcp-small-servers
! hostname BRYANT_ADVANTAGE_AS4
no ip domain-lookup
ip host r1 2001 10.4.4.4
ip host r2 2002 10.4.4.4
ip host r3 2003 10.4.4.4
ip host sw1 2004 10.4.4.4
ip host sw2 2005 10.4.4.4
ip host FrameSwitch 2006 10.4.4.4
interface Loopback555
ip address 10.4.4.4 255.255.255.0
line con 0
exec-timeout 0 0
logging synchronous\
line 1 16
no exec
transport input all
You can assign any loopback address and number here the important thing to note is that the IP HOST table you will build constantly refers back to the loopback address on the access server.
In this configuration, I have the octal cable's connector 1 in R1, 2 in R2, 3 in R3, 4 in SW1, 5 in SW2, and 6 in my frame relay switch. The number "2001" in the first line of the IP HOST table refers to that connector. That's why it is important to note the number on a given connector you place in the console port of a router or switch.
The asynchonous lines are identified by "line 1 16". This access server has 16 possible connections many will just have 8, which is usually plenty. Regardless of how many lines you have, you'll need the commands transport input all and no exec to allow reverse telnet to work effectively.
There's one more thing to watch out for. When you first connect to the AS for a practice session, you will need to open the line to each device by using the full hostname of the device as shown in the IP HOST table. Here, you would begin by entering R1, R2, R3, SW1, SW2, and FrameSwitch to open the line to each device. After that, you need to enter the line number - 1, 2, 3, 4, 5, and 6. It sounds a little confusing at first, but after just a few minutes of practice you'll be doing it without even thinking about it.
When you are working in your home lab, you will not go from one device to another that is, when you are done on R1 and want to configure R2, you must go back to the access server and then to R2. The keystroke to do this is . Again, it may sound complicated, but after a little practice you will again do this without thinking about it.
Adding an access server to your CCNA or CCNP home lab may not be on your mind now, but once you add a few more routers or switches to the lab, you'll want to spend more time configuring and practicing and less time moving a cable around. And once you get one, you'll wonder how you did without it!
Cisco CCNA / CCNP Home Lab: Why You Need An ISDN Simulator
ISDN is a vital topic for today's CCNA and CCNP candidates, especially for the ICND and Intro exams - you've got to know ISDN inside and out to pass those exams. Naturally you want to include it in your home lab. What many candidates don't realize is that you can't connect two Cisco routers directly via their Basic Rate Interface (BRI) interfaces you've got to have another device between them called an ISDN simulator.
An ISDN simulator is not one of those software programs pretending to be routers ("router simulators") this is a piece of hardware that acts as the telephone company in your home lab. Older simulators come with preprogrammed phone numbers and SPIDs, where newer ones let you program the phone numbers you want to use. Either way, an ISDN simulator is great for your CCNA/CCNP home lab, because you can practice dial scenarios that actually work. And you get to troubleshoot the ones that don't, which is also important to learn! )
You don't need any special cables or connectors you just connect both of your routers' BRI interfaces to the ISDN simulator with a straight-through cable and you're ready to go.
In years past, this was a major problem for 640-801, 811, and 821 studies, because the simulators used to be so expensive. New ones can still be pricey ($600 and up), but with the sudden influx of used ISDN simulators on ebay and Cisco resellers, you can get a used one that will do the job for you.
Why are there suddenly so many ISDN simulators on the market? Cisco recently removed ISDN from the CCIE R&S exam, so a lot of CCIE rack resellers as well as private individuals are selling their simulators. There's never been a better time to add ISDN to your home lab. If taken care of (kept out of extreme heat), they can last for quite a few years. The one I purchased for my IE home lab is still working well.
If you choose to purchase a new simulator, you can run a Google search to find vendors. I've made two purchases from www.vconsole.com over the last few years and both of those simulators have worked beautifully.
As I said earlier, there's never been a better time to add ISDN to your home lab. Don't just settle for trying to memorize theory - get your hands on the real deal, practice and fix your configurations, and you'll be amazed at what you learn and how well you do on your CCNA and CCNP exams!
An ISDN simulator is not one of those software programs pretending to be routers ("router simulators") this is a piece of hardware that acts as the telephone company in your home lab. Older simulators come with preprogrammed phone numbers and SPIDs, where newer ones let you program the phone numbers you want to use. Either way, an ISDN simulator is great for your CCNA/CCNP home lab, because you can practice dial scenarios that actually work. And you get to troubleshoot the ones that don't, which is also important to learn! )
You don't need any special cables or connectors you just connect both of your routers' BRI interfaces to the ISDN simulator with a straight-through cable and you're ready to go.
In years past, this was a major problem for 640-801, 811, and 821 studies, because the simulators used to be so expensive. New ones can still be pricey ($600 and up), but with the sudden influx of used ISDN simulators on ebay and Cisco resellers, you can get a used one that will do the job for you.
Why are there suddenly so many ISDN simulators on the market? Cisco recently removed ISDN from the CCIE R&S exam, so a lot of CCIE rack resellers as well as private individuals are selling their simulators. There's never been a better time to add ISDN to your home lab. If taken care of (kept out of extreme heat), they can last for quite a few years. The one I purchased for my IE home lab is still working well.
If you choose to purchase a new simulator, you can run a Google search to find vendors. I've made two purchases from www.vconsole.com over the last few years and both of those simulators have worked beautifully.
As I said earlier, there's never been a better time to add ISDN to your home lab. Don't just settle for trying to memorize theory - get your hands on the real deal, practice and fix your configurations, and you'll be amazed at what you learn and how well you do on your CCNA and CCNP exams!
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