10 Useful Cisco IOS Commands – Part 1

This is not a complete list of all the commands found in the Cisco IOS, instead I intend this page to be a simple reference of the commands I frequently come across when working with Cisco products.

Although, I tried to write a description for most of the commands found below some of them are self explanatory.

Schedule Router to Reload in X amount of minutes:

You can schedule a Cisco device to reload at a predetermined amount of time. The example below will reload a router in 25 minutes.

Router# reload in 25

System configuration has been modified. Save? [yes/no]: yes
Building configuration...
Reload scheduled in 25 minutes by console
Reload reason: Reload Command
Proceed with reload? [confirm]

To cancel the reload just issue:

Router# reload cancel



Display CPU load:

Router# show proc cpu

CPU utilization for five seconds: 0%/0%; one minute: 0%; five minutes: 0%
 PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process
   1           0         2          0  0.00%  0.00%  0.00%   0 Chunk Manager
   2           4       192         20  0.00%  0.00%  0.00%   0 Load Meter
   3           0         1          0  0.00%  0.00%  0.00%   0 chkpt message ha
   4           0         1          0  0.00%  0.00%  0.00%   0 EDDRI_MAIN

Display available memory:

Router# show proc mem

Processor Pool Total:  162187652 Used:   20502480 Free:  141685172
      I/O Pool Total:   16777216 Used:    2831648 Free:   13945568
Transient Pool Total:   16777216 Used:      16584 Free:   16760632

 PID TTY  Allocated      Freed    Holding    Getbufs    Retbufs Process
   0   0   28163076    6754612   19372876        351         84 *Init*
   0   0      12052      79384      12052          0          0 *Sched*

Clear interface configuration:

Clear a specific interface of all configuration and return to a default state.

Router(config)# default interface fastEthernet 0/0

Building configuration...

Interface FastEthernet0/0 set to default configuration

Change hostname:

Router(config)# hostname R12BNY

Disable host to IP translation:

While harmless frequent “Translating…. domain server (” messages can result in waste of valuable time. The logical solution is to disable Host to IP Address Translation. After disabling the message will no longer appear.

Router(config)# no ip domain-lookup

Test network throughput with TTCP:

TTCP is hidden IOS command designed to measure network throughput. In order to use TTCP you need to configure a sender and a receiver. Keep in mind this will result in increased Router load.

R2# ttcp transmit

ttcp-t: buflen=8192, nbuf=2048, align=16384/0, port=5001  tcp  ->
ttcp-t: connect (mss 1460, sndwnd 4128, rcvwnd 4128)
ttcp-t: 16777216 bytes in 75696 ms (75.696 real seconds) (~215 kB/s) +++
ttcp-t: 2048 I/O calls
ttcp-t: 0 sleeps (0 ms total) (0 ms average)
R1# ttcp receive

ttcp-r: buflen=8192, align=16384/0, port=5001
rcvwndsize=0, delayedack=yes  tcp
ttcp-r: accept from (mss 1460, sndwnd 4128, rcvwnd 2668)
ttcp-r: 16777216 bytes in 75696 ms (75.696 real seconds) (~215 kB/s) +++
ttcp-r: 8330 I/O calls
ttcp-r: 0 sleeps (0 ms total) (0 ms average)

Banner MOTD:

Change the message with which users will be greeted when logging in.

Router(config)# banner motd #

Enter TEXT message.  End with the character '#'.
You are entering the vicinity of an area adjacent to a location. The kind of place where there might be a monster,
or some kind of weird mirror. These are just examples; it could also be something much better.
Prepare to enter: The Scary Door.

Display IOS version:

Router# show version

Cisco IOS Software, 7200 Software (C7200-JK9S-M), Version 12.4(13b), RELEASE SOFTWARE (fc3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Wed 25-Apr-07 03:18 by prod_rel_team

ROM: ROMMON Emulation Microcode
BOOTLDR: 7200 Software (C7200-JK9S-M), Version 12.4(13b), RELEASE SOFTWARE (fc3)

Disable Cisco Discovery Protocol (CDP):

CDP allows a Cisco device to see an adjacent Cisco device along with the protocols and IP addresses it uses. While useful CDP is considered by some to be a risk because it provides information to potential attackers.

Router(config)# no cdp run