Question in regards to discovering what ports have a connection

boxerboy1168

Hello all,

Building myself a pretty big lab and trying to do this off the top of my head without looking up commands.

So I have a bunch of switches with ip phones and hosts connected to them and I'm connecting them to ports based on which vlan they are in. The phone are in ports 10-15 and so on and so forth. So I logged into my lab to continue messing with the configuration and I had totally forgotten which ports needed configuration in order to continue with port security and all that.

So what I'm trying to figure out is what is the best show commands to figure out what ports are connected and what they are connected to?

clarson

1) look at your networking diagram.
2) there is a "description" field for each port
3) label your wires
there is a reason that network documentation is required
4) there is the mac address table. but, your host device needs to be on and sending packets
5) use cdp or lldp. but not all equipment support these
6) start tracing back your wires.
7) start over and document your network this time

mine isn't documented either. You might remember it this week, maybe next month, but no way next year. I'm just guessing at it.

you can see which ports show activity when pinging.
see which port light come on/off when you plug the cable in/out.

MitM

clarson is spot on. Network documentation is important. I always add a description to the ports.


My go to commands are

show ip arp
show mac address table address <mac address>
show cdp neighbor (when using cisco IP Phones)

boxerboy1168

those commands are good if I have traffic on the network but if I'm setting up my network and handling original configurations technically there shouldn't be any access or traffic over the network

if network documentation is the best way to go then I don't need to worry about it I can reference my diagram on packet tracer rather than try to problem solve through the CLI

thanks

cshkuru

Maybe I am misunderstanding your question, but why wouldn't you start with the basic show commands? show run and show ip int br are the two most useful commands I can think of.

Hondabuff

1) "show interfaces status" Shows you what ports are up and on
2) "show arp" Gives you connected IP addresses and MAC's
3) Ping the IP address in the arp table to verify it is working
4) "show mac address-table address xxx.xxxx.xxxx" from the arp table, Shows you what port the mac address is on
5) "show interfaces trunk" verify your trunk ports

chubby2002

I typically use:
sh vlan
sh ip int bri
sh int x/x/x

If it involves IP phones then this could also be another:
sh cdp neighbor

To check what ports need configuring you can also use:
sh run int gi x/x/x

boxerboy1168

ahhh ok, the last 2 post really helped