Cisco Quick Tips

Quick tips for performing common tasks with Cisco networking equipment.

Restarting or Rebooting
Restart immediately

Restart or reboot a Cisco immediately, in enable mode type:

Router#reload

Restart or Reload in N Minutes
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.

Cisco Routing
Add a Static Route on your Cisco routers

For example, in configuration mode:

Router(config)#ip route 192.168.1.0 255.255.255.240 192.168.1.254 1

Show routing table of Cisco router
In enable mode:

Router#show ip route

Cisco ARP
Clear ARP Table of your Cisco router or switch

To clear the ARP table, in enable mode:

Router#clear arp

Show ARP table of a Cisco router or switch
To display the ARP table of a Cisco router, in enable mode:

Router#show arp

Cisco Load
Show Proccessor Load of your Cisco router or switch

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%

Cisco Memory
Show Used and Available Memory of your Cisco router or switch

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

Cisco Committed Access Rate (CAR)
An example that limits an IP to 512K, with a nice, fat burst.

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.