Can you ID and endpoint from a Cisco Switch

mac_cnc

mac_cnc

2[H]4U
Joined
Oct 14, 2000
Messages
2,560
So super short cliffs version:

We have a switch in our IT office, Cisco 2960G. It plugs into the wall and goes to the server room and connects somewhere. This weekend we redid almost the whole server room and now this switch can connect to the rest of the network. The uplink has a link light but can get anything.

I have rebooted the switch, used scanning on our other switches to try and find the MAC of the switch but for the life of me I cant see it. Is there a command I can run from the command line of the switch to see where its pointing?
 
Well there could be several different issues going on, the simplest way to help us figure out what is going on, would be to post a sanitized config of the switch.

Reason being is that you could be running trunk's, the port could be set to the incorrect vlan, or one of a million different things.

Do you know what VLAN's may be defined on this switch, and if so are any trunks used?
 
"show cdp neighbors detail"?

"show mac address-table" will give you the mac addresses of all the devices on the switch, including the internal mac addresses.

"show interface XXX" will also give the the mac address of the port

Unplug the cable and see which port in the server room goes down.
 
I am not sure of the VLAN on this switch. We actually have it configed for a bunch of VLANs so I think the uplink is a trunk.

djflow I will try some of those commands.
 
Bobacus said:
Reason being is that you could be running trunk's, the port could be set to the incorrect vlan, or one of a million different things.
Click to expand...

The switch should be flooding the console log with mismatch vlan errors, assuming CDP is running.

If you are getting a link light but no traffic, check the cable pairs. I've seen cables with a bad pair that show a link light but not come up.

When you say redid, do you mean just physical relocation, IOS reconfiguration or both?
 
We moved a ton of equipment and switches. To the best of our knowledge everything went back to where it was supposed to.
 
First console into the switch. From there check the status of the interfaces, make sure they are up/up and not up/down or down/down. From there trying pinging from the console to a server or other switch. Maybe you plugged the other end of the switch into an access port instead of the original trunk port.

Really, it could be a million things. You need to console in to the switch though. I can remote in if you would like.
 
Hello all. We actually attached the console cable and right on the main screen it gave us the VLAN mismatch info. It allowed us to find the port on the data center switch and correct the issue.

All is well now. Thanks for all the help everyone. You put me in the right direction.
 
RocketTech said:
Tone the cable, you should find it in a heartbeat.
Click to expand...

Dude, don't you read the thread? I've seen this happening a lot lately, where someone reads the first post and then replies without checking any of the other replies. He said the issue was resolved.

Besides, toning the cable wouldn't work. It is plugged in to another device, which grounds the signal. While not impossible, it makes it very difficult to read a tone.
 
'Dude', calm down- I read the thread, it is called post lag. Also, when someone searches for the same issue, a perfectly valid response will be available.
And yes, you can tone a connected cable with a decent toner- I tone connected cables with my Fluke qualifier all the time to avoid wasting my time on this exact issue. A decent qualifier can also flash port lights in a specific pattern, making it easy to pick-out the port on a switch.
Just FYI, Fluke's line of digital toners will trace connected or disconnected cables easily, pick the specific cable out of a bundle, and find the cable in a dense patch/switch panel. It will not trace a cable with dial tone on it :(
 
Fluke's are great equipment - the downside is that they often costs more than the switches/routers themselfs :p
 
You must log in or register to reply here.
Back
Top