There are a lot of commands in the Cisco IOS that you can use for troubleshooting. It depends on what the symptoms are and what networking technology you are using (eg ATM, ethernet, frame relay).
The more common of course are your sh ip int brie, sh run, sh ver, sh controllers etc but there is one that encompasses all of the afore mentioned and more. And even better, it will help you if you need to get help from a colleague or the TAC to solve your problem.
From ‘enable’mode, type in ‘show tech‘ and you will see that quite a long output will be provided (hint: you may want to set ‘term length’ to 0 for this so you cont have to hit the spacebar after each screenful of info. Also log your session so you can save the output).
If you have a look at the output, there is a lot of info there that doesnt make any sense to me, but what you will also see are the result of the more common commands that you would normally use (ie sh run, sh ver etc).
As I said, if you need to reder your problem to someone else, this will be a handy output to provide. Often the TAC will ask for it so it will save time by providing this upfront to them.