Thursday, November 20, 2008

This is not my work . The entire credit goes to Mr.Darby Weaver . you can reach him at

Cisco IOS Tips and Tricks..

You probably know these by now but jus in case you don't:

- Auto-completing commands
- Disabling DNS server lookup
- Limiting EXEC interruptions
- Setting console speed
- Deprecated commands
- Time-stamping messages
- Setting the clock and time zone
- Displaying the interface of a config
- Filtering the output of commands
- Erasing an interface config
- Setting the Terminal Length of a Router, Switch, or Firewall
- The DO command
- Alias Commands
- Privilege levels
- Changing the TCP timeout
- Stopping "The Runaway Debug"
- Editing access-lists
- No service config

Auto-Completion of commands

It's only necessary to type enough letters of any given command to make the command unique at the current configuration mode.

Then use the key to autocomplete.

I normally use this method daily and accompany it with the character to help me remember options or to learn whatever options are available to me just beyond the prompt.

Note: The ? is very helpful since you are probably like me and work with a wide array of devices and IOS versions.

Disable DNS Server Lookups

When you type something at the prompt that is not a command the IOS tries to telnet to it. It's a smart tool like that and I really appreciate it on my Access Server, example R1, R2, R3, etc.

I do not like what it does to my day to day typos and if you read my posts I make a lot of typos.

"no ip domain lookup" in global configuration mode and this little pesky time-consuming issue is resolved.

Limit EXEC Interruptions

This is a great little tool for me. I love it and use it everywhere. Basically it ensures that no matter how many messages I receive at the prompt while I'm typing I never lose my place. So I do not get "interrupted". Put it in your toolbag. It's very helpful.

conf t
line vty 0 15
no logging synchronous

Setting the Console Speed

This is great just to get access to a Cisco device. But did you ever consider using it as a security tool? I mean if you have junior admins and who doesn't or "helpful peeps" from other departments...

This is priceless. BTW - It has saved me on some otherwise priceless pieces of gear bought on ebay. Note: I always look for the sh ver on "junk" that is sold to be non-working... Some folks never heard of a config register before.


Anyway here you go:

line console 0
speed 115200

This also saved me in a pinch when I needed to transfer IOS over the Serial line... It's happened to me and could happen to you. 115200 may not be speeding in some countries, but it beats 9600 bps.

Deprecated Commands

Some very helpful commands are no longer supported by Cisco, but I love em anyway.

OLD Command New Command
wr (write) copy run start
wr er (write erase) erase start
who show users
whe (where) show users

Oh yes... who = "w" for those who don't like to type much.

show alias will show you others...

"p" = ping

How about that for a time saver.

Timestamping Messages

I once worked with a hot-shot Security guy... who... started configuring his Mars and other Logging devices and did not seem to recognize the importance of setting and synchonizing his time servers first...

I even took the time to draw it out in Visio. But since it was his job to make me look like the village idiot... it fell of deaf ears...

True story by the way...

So I did not both finishing my tail about Timestamping with our super-star.

For the rest of the world...

Ever get timestamps with the wrong date or time?
How about debugs too?

Yep... I hate non-timestamped logs...

I love time-stamped logs and debugs.
I love time-stampted loge and debugs with sequence numbers even better.

service timestamps (log|debug) datetime localtime
service sequence-numbers

Use them to your heart's content.

Look like a hero to your boss and coworkers.

My best advice is use them everywhere. Then you can track things when they happen even across an entire enterprise.

Cool huh?

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