Josh Gentry, jgentry@swcp.com
v.1.2, May 15, 2006
Quick tips for performing common tasks with Cisco networking equipment, brought to you by the author of the widely used, Cisco Router Configuration Tutorial.
To restart or reboot a Cisco immediately, in enable mode:
Router#reload
To restart or reboot a Cisco in a certain number of minutes, in enable mode:
Router#reload in 5
Extra Tip: This is useful when you are afraid that the configuration changes you are about to make might break something or lock you out of the router. You tell the router to reload in a certain number of minutes, then make your changes. If it turns out your changes are catastrophic and you can't log back into the router to fix them, the router will reload in a few minutes and go back to its previous configuration.
For example, in configuration mode:
Router(config)#ip route 192.168.1.0 255.255.255.240 192.168.1.254 1
In enable mode:
Router#show ip route
To clear the ARP table, in enable mode:
Router#clear arp
To display the ARP table of a Cisco router, in enable mode:
Router#show arp
Like any computer, a Cisco router can be limited by its processing power. To show the processor utilization, in enable mode:
Router#show proc cpu
At the beginning of the output, look for a line like this:
CPU utilization for five seconds: 37%/31%; one minute: 39%; five minutes: 40%
Like any computer, a Cisco router can be limited by its available memory. To show the used and available memory, in enable mode:
Router#show proc mem
At the beginning of the output, look for a line like this:
Total: 200234528, Used: 70508188, Free: 129726340
First create the access lists.
access-list 100 permit ip any host 192.168.100.100
access-list 100 permit ip host 192.168.100.100 any
Then apply rate limiting rules to the appropriate interface:
rate-limit input access-group 100 512000 1024000 2048000 conform-action transmit exceed-action drop
rate-limit output access-group 100 512000 1024000 2048000 conform-action transmit exceed-action drop
Extra Tip: If, in a rate-limit rule, you reference an access list that does not exist, the rule will match all traffic. Usually not good.
A good introduction to Cisco router configuration: