Common Cisco IOS Commands

Here’s a list of IOS commands that I use all the time that aren’t a part of the basics. I obviously use more than just these, and you do, too, but I hope there’s at least one eye-opener in there.

show env all: Shows the environment status, including fan, power supplies, etc. Good for making sure the environment is alright.
show history: Shows your command history since you logged onto the device. Good for remembering what command you put into get those stats the boss needs. Configuration changes don’t show up here.
show inventory: Shows a nice list of what the device has hardware-wise. It’s good for a router with a bunch of modules or a switch with a bunch of cards.
show interface trunk: Shows all the trunks on a switch along with pruning information. Good for making sure all VLANs are propagating around the network.
show interface capabilities: Shows what the interface is capable of doing — not just what’s its configured to do.
show interface counters: Shows byte and packet information for every interface. Good for quickly showing statistics without having to look at all the show interface garbage.
show mac-address-table: Shows the CAM table on a switch. Good for tracking down where a host is plugged into.
show tcp brief: Shows all TCP connections associated with the device like SSH sessions or BGP.
show users: Shows who’s logged onto the device. Good for finding a line to clear to kick everyone off the box.