Passing the CCNA, Intro, and ICND exam is all about knowing and noticing the details. (Which makes perfect sense, since becoming a master networking administrator or engineer is also about noticing the details!) One such detail knows the difference between error detection and error recovery. While the terms are sometimes used interchangeably, they are not the same thing.

Error detection is just that – error detection only. Two common error detection methods are found at the Data Link layer of the OSI model, the FCS (Frame Check Sequence) and CRC (Cyclical Redundancy Check). A mathematical equation is run against the data in the frame, and the result is sent along with the data. The receiver runs the equation again, but this time. If the result is the same, the frame is considered valid; if the result is different, the frame is considered corrupt and is discarded.
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Part of your CCNA / CCNP education is deciding what network topology to use when you’re putting together your home lab. Some of you are starting with one or two routers or switches, while others are starting with more. A customer recently sent me a list of his Cisco routers and switches that he has available for a home lab and asked for my help in coming up with the best way to use them.

There is no “right” or “wrong” answer to this question; again, part of the learning process is configuring and reconfiguring the physical topology of your lab. Let’s look at the routers and switches he has available, including the interfaces on each, and come up with one possible CCNA / CCNP home lab setup.

The equipment list:

Two 3620 routers. Each has 1 serial port and 2 ethernet ports.

One 3640 router. This has two ethernet cards, each with two ports, and two AUI ports.

Three 2503s, my personal favorite for home labs! These have 1 AUI port, 2 serial interfaces, and one BRI interface apiece.

One 2524 router. This has one serial port, 1 ethernet port, and one BRI interface.

One 4500 router. This has eight BRI ports, 2 ethernet ports, and more importantly, four serial ports.

He also has a 5200 access server, an ISDN simulator, one 2924 switch, and one 1924 switch.

Now, if you don’t have this much equipment to work with, don’t panic! Most CCNA / CCNP candidates don’t; this is more of an exercise in looking at what you do have and using it to the utmost.

As I’ve mentioned in many of my CCNA / CCNP home lab articles, an access server is a great thing to have. All he needs is an octal cable to connect his AS to the other devices we choose to use, and he’s all set. (If you need an access server sample configuration, there is one on my website in the Home Lab section.)
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CCNA / CCNP candidates are going to be drilled by Cisco when it comes to troubleshooting questions. You’re going to have to be able to analyze configurations to see what the problem is (and if there is a problem in the first place), determine the meaning of different debug outputs, and show the ability not just to configure a router or switch, but troubleshoot one.

That’s just as it should be, because CCNAs and CCNPs will find themselves doing a lot of troubleshooting in their careers. Troubleshooting isn’t something that can just be learned from a book; you’ve got to have some experience working with routers and switches. The only real way to learn how to troubleshoot is to develop that ability while working on live equipment.
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I know from experience that part of the excitement and anxiety of putting together your own CCNA / CCNP home lab is deciding what to buy! While you can make a workable home lab out of almost any combination of Cisco routers and switches, some routers are better suited for home lab work than others because they can fill multiple roles.

My personal favorite is the Cisco 2520. This router has four serial interfaces, making it an ideal frame relay switch. Don’t forget that just because you’re using a router as a frame switch, you can still use its routing capabilities. One setup I use is to use three of the four serial interfaces for frame switching and the fourth interface as a point-to-point network with another router. All you need is some DTE/DCE cables and you’re all set.
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When you’re preparing for CCNA and CCNP exam success, the best investment you can make is to put together your own home lab. There is no better way to learn Cisco technologies and prepare for the CCNA, BSCI, BCMSN, CIT, and other exams than by working with the many protocols and services you’ll need to master in order to pass the exams.

One of the most popular articles I’ve written over the few years dealt with buying and configuring a Cisco router as a frame relay switch. That article is still available on many websites (including my own), but I want to remind you that just because you configure a router as a frame relay switch, that doesn’t mean you can’t use it as a home lab router, too!
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A Cisco home lab is an invaluable study tool when you’re preparing for CCNA and CCNP exam success. Once you’ve gotten a couple of routers and switches, you’ll quickly get tired of moving that blue console cable every time you want to configure a different device. The solution to this problem is purchasing and configuring an access server (AS).

For those of you new to access servers, note that these are not white boxes running Microsoft operating systems. These are Cisco routers that allow you to connect to all the routers and switches in your home lab without moving a cable. You can physically or logically connect to the access server and work with all your devices from there.

When you’re pricing access servers, please remember that you do NOT need an expensive AS. Right now on ebay there are access servers costing up to $5000 – this is NOT what you want to buy. What you’re looking for is something like a 2509 or 2511, which is going to run you anywhere from $100 – $200. It’s money well spent, because once you get an AS, you’ll really wonder how you ever did without it.

The only additional hardware you need is the cable that will physically connect your AS to the other routers and switches in your home lab. The cable you need is called an octal cable, so named because one end of this cable is actually eight ends, all terminated with a numbered RJ-45 connector.

The large end of the cable is going to be connected to the AS itself. The cable will connect to a port on the AS that will have “async 1-8″ directly above the physical port. It is this port that makes an AS different from other Cisco routers.

Once you’ve got your AS and this cable, you’re ready to configure your AS. Connect the cable to the AS as described above, and then you will connect one of the RJ-45 connectors to the console port of each one of your routers and switches. Make sure to note the number that’s on the cable itself right below the connector, because that’s very important. In the next part of this home lab tutorial, I’ll tell you exactly how to configure your access server for best results, along with a few troubleshooting tips.