CISCO IOS in a Nutshell

Interface show Commands

The router keeps track of lots of information about its interfaces: the number of packets sent, the number of errors, addresses, etc. You can get most of this information by using one of the show commands.

Clearing the show Command Counters

Much of the information the router tracks is numeric: for example, running counts of the number of packets that went out the interface and related items. These counters aren’t particularly meaningful unless you know when the counter started counting. To clear the counters that are displayed in the show interface commands, use the clear counters command. This command does not clear the values that are retrieved from SNMP commands, but only the values reported by the show commands discussed in this section. Here are some typical clear counters commands:

Router#clear counters ethernet0
Router#clear counters serial0
Router#clear counters

The first two commands clear the counters for a specific interface; the last command clears the counters for all the interfaces.

Tip

All counters are unsigned long integers, which means they can go up to about 4 billion before they roll over to 0 (2^32 - 1).

Listing All Interfaces

If you don’t know what physical interfaces are available on your router, use the show version command. You’ll find a list of interfaces at the end of its output. Here’s what happens on a Cisco 2524:

Router>show version ... cisco 2524 (68030) processor (revision J) with 6144K/2048K bytes of memory. Processor board ...