Daniels networking blog

Was chatting with Darren at Darren’s CCIE mission yesterday. We started to discuss some of the commands we frequently used to check IP addresses etc. He thought I should do a post on it and here it is.

This first one I stumbled upon when I was going to type show ip prot but accidentally typed show ip port which turned out to be a good thing. This command show port mappings for different protocols used by IOS. If we get a task on lab to do filtering and can’t remember the port this can be really useful.

As you can see we can do an include to match on a port number or a protocol name.

The next command is one of the commands I use the most, show ip int brief | ex una. This will list all interfaces that have an IP address configured.

This is good but it will not tell us the netmask. If we have a troubleshooting task it is nice to check what IP’s are configured and if the correct netmask is used. Wit the next command we can check the netmask. Show ip int | i Internet.

If I want to verify reachability quickly I need to list all IP address configured on the devices. I use the show ip aliases command to do this. I paste the command in including a line feed on all devices and then hold alt down while I mark all the adresses.

I then put these addresses in a simple TCP script like below:

tclsh
foreach ip {
1.1.1.1
2.2.2.2
3.3.3.3
} { ping $ip}

This post should give you some tips on how to quickly discover IP addresses configured.