IOS Console Customization
By stretch | Monday, May 10, 2010 at 3:07 a.m. UTC
This article offers a few tips to customize the behavior of a Cisco IOS router's VTY and console lines.
Set a Custom Escape Character
The default IOS escape sequence is ctrl-^x, or "control-shift-6, x", as we can see from the output of
Router# show terminal Line 6, Location: "", Type: "xterm" Length: 25 lines, Width: 120 columns Baud rate (TX/RX) is 9600/9600 Status: PSI Enabled, Ready, Active, No Exit Banner, Automore On Notify Process Capabilities: none Modem state: Ready Special Chars: Escape Hold Stop Start Disconnect Activation ^^x none - - none Timeouts: Idle EXEC Idle Session Modem Answer Session Dispatch never never none not set ...
This obscure sequence probably has some historical significance, but it is most commonly used on IOS today to interrupt a ping or traceroute command. We can set a custom escape character to something more convenient, such as ctrl-c (which is the ASCII character 3):
Router(config)# line vty 0 15 Router(config-line)# escape-character ? BREAK Cause escape on BREAK CHAR or Escape character or its ASCII decimal equivalent DEFAULT Use default escape character NONE Disable escape entirely soft Set the soft escape character for this line Router(config-line)# escape-character 3
We can now simply use ctrl-c in place of ctrl-shift-6. The "x" generally isn't necessary.
Alternatively, a temporary custom escape character can be defined for the current session only using the
terminal escape-character EXEC command.
Increase the History Size
By default, the terminal history (which records recently used commands and is invoked with the up arrow) is limited to the last 20 commands. We can increase the history size under line configuration or via the
Router(config)# line vty 0 15 Router(config-line)# history size ? Size of history buffer Router(config-line)# history size 100
show history can be used to inspect the contents of the history buffer.
Infinite Terminal Length
Often you'll need to copy a good amount of text from the console (e.g. the output of
show run or
show tech-support). Depending on the terminal emulator in use, you may notice the copied or saved text has been polluted with lines reading "--More--" followed by unprintable characters (^H), which were inserted by the IOS CLI pager. A handy solution for this is to temporarily set the terminal length to zero, which effectively sets an infinite terminal length and disables terminal paging.
Router# terminal length ? Number of lines on screen (0 for no pausing) Router# terminal length 0
To return the terminal length, use
terminal length appended with the desired number of lines (typically 24). If you want to permanently alter the terminal length, use the
length command under line configuration.
Include Timestamps on Show Commands
IOS includes an option to automatically timestamp the output of
show commands. This can be handy when producing records for documentation or archival purposes.
Router(config)# line vty 0 15 Router(config-line)# exec prompt timestamp Router(config-line)# ^Z Router# show ip interface brief Load for five secs: 0%/0%; one minute: 0%; five minutes: 1% Time source is hardware calendar, *03:14:21.123 EDT Wed Apr 14 2010 Interface IP-Address OK? Method Status Protocol FastEthernet0 126.96.36.199 YES DHCP up up FastEthernet1 unassigned YES NVRAM up down ...
Lock the Terminal
A little-known feature that might come in handy: IOS allows you to temporarily lock your console session. First, locking must be enabled under line configuration:
Router#(config)# line console 0 Router#(config-line)# lockable
Simply issue the
lock command, and provide and confirm a password of your choosing (it need not be your username's password) to lock the terminal. Provide the password again to unlock the terminal.
Router# lock Password: Again: Locked Password: Router#
For more tips like these (but not necessarily related to the console itself) check out the IOS Tips wiki page!
About the Author
Jeremy Stretch is a network engineer living in the Raleigh-Durham, North Carolina area. He is known for his blog and cheat sheets here at Packet Life. You can reach him by email or follow him on Twitter.
Posted in Tips and Tricks
May 10, 2010 at 9:31 a.m. UTC
regards Shivlu Jain http://www.mplsvpn.info
May 10, 2010 at 12:59 p.m. UTC
Great post usefull stuff, as always.
May 10, 2010 at 1:00 p.m. UTC
Changing the escape character is sweet, didn't know you could do that.
May 10, 2010 at 2:48 p.m. UTC
Nice writeup. I've seen those commands before, but haven't used them myself.
May 10, 2010 at 7:18 p.m. UTC
thanks I always hate ctrl shift 6 x
May 11, 2010 at 12:58 a.m. UTC
I've recently started using the exec-timeout parameter since the default is annoyingly short. Thanks for the tips.
May 16, 2010 at 10:48 a.m. UTC
I like also "logging synchronous " on both vty and console.
April 18, 2012 at 8:18 a.m. UTC
Thankks Jeremy nice very useful.