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Added by Mark Jacob September 14, 2015

If you have read my previous postings regarding GNS3 as a practice platform, then you have probably gotten the gist that I am a big supporter. It can even do most of the things that are required, with just a few exceptions. This is typically done by configuring a router with an EtherSwitch module and then typing switch-related commands on that router. However, even in this age of virtualization inroads, occasionally you still have to use a real router with a real EtherSwitch module. In this blog I will show how it is done.

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I will be using a 2811 router with a 16-port module (NME-16ES-1G-P). Both are completely erased as if I just bought them on Ebay. First I will connect my console cable to the console port and tap the ‘Enter’ key to wake it up. Then I will issue the ‘enable’ command to get to privileged exec mode. Now let’s see some of the nitty gritty details. Let’s check to see on which port the router can ‘see’ the switch module:

Figure 1

This shows me that my router can see the switch module on local interface G1/0. The command to access the EtherSwitch module is shown in Figure 2:

Figure 2

Clearly, in order to be able to access the module, I need to note the error I received when I typed the command a little early. I need to configure a valid IP address in G1/0 before I will be able to reach the switch. I will assign an IP address of 172.20.1.1 with a 24 bit mask on that interface and bring it up. See figure 3:

Figure 3

Now that the interface on the router is properly configured, let’s try again to reach the switch:

Figure 4

Technically I am still consoled into my router, but I can get to my switch, as shown in figure 4. I can get to privileged exec mode and type ‘show run’ as well as configure or anything else a network admin would like to do on this switch. To get back to my originating device (my 2811), I use the three-finger keystroke combination of Ctrl-Shift-6 all at the same time, then I release and quickly hit ‘x’ to get back. Let’s try that:

Figure 5

To verify the session is still active, I use ‘show sessions’ or ‘where.’ Note the result in figure 6:

Figure 6

If I wish to resume that active session, I can type resume {#} where the number in brackets is the connection number, which, as seen in figure 6, is my only connection, and its number is 1. Let’s see what that looks like:

Figure 7

There it is. A bit more involved than an EtherSwitch nodule in GNS3, but who said real life would be easy?!

I hope you found this to be useful information, and if you have comments or suggestions for future blogs, don’t be shy at all.

Mark Jacob
Cisco and CompTIA Network + Instructor – Interface Technical Training
Phoenix, AZ