If someone were to look at your router’s configuration, could they understand what the real purpose of the network connections were, who they connect to, and what to do if the interface is down? If you answered no, then you need to look at using router interface descriptions.
What is a router interface description?
Router interface descriptions are description commands that network administrators configure on each interface of a router. With these commands, the administrator can enter whatever pertinent information he wants to, about that interface. This can be very useful for the original administrator that configured the interface. Or this can be valuable to any other administrator that has to try to troubleshoot or reconfigure the interface later. For example, you could put the following command on your router’s interface:
description T1 circuit to Internet – Sprint Circuit ID QVX.123.098.765.DAX – Tech Support 800-555-1234
By using this command, I have described what the circuit’s purpose was, the Circuit ID, the provider, and the tech support phone number.
By doing this, the next time I look at the router, I have all the important troubleshooting information I need, right at my fingertips.
Uses of a router interface description
The recommended uses for the router interface description command are:
Identifying the interface
Noting who to call if the interface is down
Documenting the circuit information for that connection
In general, using the description for a “notes” field
I have even used the description field to notate what the current IP address was on an interface before I changed the IP address. That way, I have documentation, on the router’s interface, what the previous configuration was.
Keep in mind that while we are calling this field a “router” interface description, the description command works on Cisco IOS switches and PIX firewalls as well.
Sample configuration of a router interface configuration
To apply a description on your router’s interface, use the following steps:
Move to global configuration mode, like this:
router# config t router(config)#
Move to interface configuration mode. In our example, let’s assign an a description to the Serial 0/0 interface:
router(config)# interface serial 0/0 router(config-if)#
Use the description command with the description you define for this interface. Here is an example:
router(config-if)# description T1 circuit to Internet – Sprint Circuit ID QVX.123.098.765.DAX – Tech Support 800-555-1234
To view the interface’s description, press Ctrl-Z to exit back to privileged mode then type:
router# show run interface serial 0/0 interface Serial 0/0 description T1 circuit to Internet – Sprint Circuit ID QVX.123.098.765.DAX – Tech Support 800-555-1234 ip address 18.104.22.168 255.255.255.0
In the graphic below, you can actually see how it is done:
What you need to take home from this article is that the Cisco IOS description command can be used on Cisco Routers, Switches, and PIX Firewalls to create custom descriptions for every interface on those devices. These custom descriptions can be used to better document and more quickly troubleshoot your network.