Today we are going to review some of the different types of Cisco modules you might find in your Cisco Certified Entry Networking Technician (CCENT) 100-101 or Cisco Certified Network Administrator (CCNA) 200-120 lab. What are all these different types of serial modules and how do we connect them together properly is a common question from many perspective students. In today’s CCNA blog post, we are going to focus on the various serial modules you might encounter and some of the caveats in using them.
So the first thing Cisco certification students sometimes ask is why do I need to worry about or use outdated serial modules? Aren’t they really old and slow? Well, yes and no. Most of the modules you will see in your CCENT or CCNA lab are older and slow, but the concept of WAN protocols and encapsulation being different from LAN encapsulation is what Cisco really wants you to understand. As there are a whole host of WAN protocols and encapsulation methods such as PPP, HDLC, Cisco, Frame-Relay, X.25 and ATM as being main ones for the point of our discussion today (there are some others such as PPPoE, PPPoA, Ethernet that are out of scope for our discussion in your CCNA studies). So with your normal PPP leased line WAN link between two offices such as your Headquarters and Branch office you will want to create a private link that is only available to your company’s users. What you will generally do is put a serial module into the HQ and Branch office router and select the speed you want from your service provider. A common leased line is a T1 link which I am sure you have heard of before.
WIC-1T, WIC-2A/S and WIC-1DSU-T1 Serial Modules
So that gives you the theory behind what we are trying to accomplish and what Cisco is hoping for you to learn as you do your PPP, Frame-Relay and other labs that will utilize a WAN connection between routers. For the context of this discussion, we will talk about modules that will work in 1800, 2600 and 2800 series routers.
So the first serial module we will cover is the WIC-1T serial module. These are an older style serial module that the DB60 connector dates back to the old 2501 routers from 1997 and were the primary serial modules used in CCNA labs until about 2 years ago. The driving reason they were most popular was due to cost and if you were connecting one of your modular 1800, 2600 or 2800 series routers to a 2500 series router, it was just easier to have the same style interface so you did not have to buy different cables if you decided to change the configuration. These are fine to use and work ok for our lab purposes and work in pretty much any router up to the ISR G1 series. The only drawback is that it is a single interface module and today you can get one of the dual interface modules for about the same price.
The next module that you might want to use in your CCNA lab is an NM-4A/S 4 port serial module. Again, these are fine if you are sticking with all DB60 interfaces. But since most people are moving to the smart serial interfaces which we will talk about next, I would assume these will become less popular.
Next is the WIC-2A/S or WIC-2T 2 port smart serial modules. These are probably the most popular now due to cost and they have two interfaces. In the old days is you had let’s say a 1760 and you wanted that to be your headquarters router and you wanted to branch routers hanging off of it, you had to buy two WIC-1T modules. Now for the same amount of money you can get a WIC-2A/S or WIC-2T module for the same price so it saves you money. Again, with these you will use a smart serial cable.
Our last serial module we will talk about has been also slowly fading in popularity. The WIC-1DSU-T1 one port serial modules used to be the second most popular modules as they were the cheapest. But then many people had trouble finding the special WIC-1DSU-T1 crossover cable or they would confuse them with a standard crossover cable or even a patch cable. Add to the complexity that there are two versions of the WIC-1DSU-T1 module and it made it even a little more confusing to someone trying to learn. As the version 1 of this module worked in the 1700 and 2600 series whereas the version 2 of this module worked in the 1800 and 2800 series routers. So kind of going back to the limitation of the WIC-1T serial module, if you needed two interfaces in one router, you needed two of these cards which doubled the expense which is why the WIC-2A/S and WIC-2T modules have seem to become the most popular serial modules for your CCENT or CCNA labs at this time.
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