Interface macro command on a Cisco switch

From the beginning let me tell you that I don’t see very useful this command, as I prefer to use “interface range…” syntax, but since I saw it as a requirement in one of the task for CCIE RS lab exam, and maybe somebody will find it usable in real environment, I said I should put it here in a tutorial.

As many of you already know, you can control a range of interfaces by typing the command “interface range Fa0/1 – 6” (for example), but there is another way to do this by using the interface macro style. For those how are beginners, this interface range or macro syntax spare you from typing 6 commands under 6 interfaces (stick to the example above), but issue only one command under interface range or macro.

Please see the tutorial below:

Limit traffic on a Cisco switch L2 port with minimal configuration

Let’s say that somebody (or some task in a test) ask you to limit the inbound traffic on a switch Layer 2 port by using minimal configuration possible. I must say that in the first steps I failed this task miserable, but actually is very simple to do it.

I will use a plain layer 2 Cisco 2950 switch for this task. I observed that I could not implement this on a Cisco 3500XL. I don’t know if the IOS image was wrong, but I didn’t investigate too much in that area as I cannot stand 3500XL switches and they are actually pretty old piece of hardware.

No topology is needed for this as I will only show how to do it and not testing it with real traffic. I will do testing later when I’ll have some more time, or you can do it on your own.

See the tutorial below:

Cisco hidden tool: test crash

This is pretty old trick, so maybe  you already know it, but for the rest of you, it can be interresting.

You just had a crash on you Cisco hardware and you have the logs, but don’t know exactly what caused this crash. You tried to have the device crash again, to compare the logs maybe you’ll find the cause, but your device won’t crash (of course, it will crash only when don’t want that to happen).

There is a hidden Cisco command: “test crash”. This can help you if you are lucky enough to have the real crash exactly like one of those you can test with “test crash” command.

Note: As you can see in the previous posts I do my tutorials based mostly on Dynamips, when it is possible. This is not the case. So, please do not use Dynamips for this test, as it will go into errors since the device is simulated and not a real one.

Please see the tutorial below:

Frame-Relay: PVC test with ping to own interface

Let’s say that you have a link configured with Frame-Relay and from time to time you observe that the link is having some strange problems. Since you cannot be sure that the link is provided 100% error free you want to do your own tests. You want to see if the Frame-Relay between R0 and R1 is correctly configured. In order to verify this you want to set up the R0 to test the PVC to R1, by sending traffic to its own IP address.

Please download the topology here. The Frame-Relay between R0 and R1 is already configured.

See the tutorial below:

Cisco hidden tools: Testing TCP connection

Sometimes you have a connection between 2 routers that you want to test with something more than a ping. Cisco devices have a hidden command which is actually a very powerful testing tool for your TCP connection.

The command is “ttcp” and you will not find it in the the default list of commands of a Cisco device. So, even if you use help ( “?” mark at the router prompt) this command will not be showed to you.

For our testing we will use the same topology as in the previous posts. If you do not have it please download it here. Since this is a point-to-point TCP connection testing we will not use any fancy routing protocol or other networking protocols.

See the tutorial below: