We help IT Professionals succeed at work.

Determining Connected Devices on a Cisco Switch

Neptune IT
Neptune IT asked
I've got a Cisco3560 POE Switch that we have been migrating users off of to other switches in our facility.  What we have been doing to perform this migration is to perform the "sh mac-address table" command, log the MAC addresses, and then look these up on our DHCP server to determine the connected device.  I have four devices remaining on this switch, 4 ports are still showing active and flashing green lights, but the above command never shows a MAC address for these ports.  I've ran the command at numerous times during the day and it never shows a connected MAC address.  Before I take off through our large manufacturing facility and start following physical cable runs, I wanted to know if anyone had an other ideas of how I can determine some more information about these connected devices?
Watch Question

The problem would seem to be that the 4 connected devices are not sending traffic.....  Until they attempt to pass traffic through the switch it will not learn their mac addresses...

You might try to do a ping sweep through your ip address range.  Assuming the devices will answer a ping the switch should learn their mac addresses when they respond.

you can try to shutdown and 'no shutdown' port.
this also could help


I tried the PING sweep on our entire Class B network but that didn't cause any additional MAC addresses to show up.  I've also tried disconnecting and reconnecting the ethernet cables from the switch and have also tried the "shut" and "no shut" on the ports.  Still no luck.  Looks like I'm gonna be left with get the scissor lift and tracing cables unless someone's got more ideas.

hi there!
have you found what kind of devices are attached to your switch?


Nope.  I guess I'm down to having to trace the cables unless you have any additional ideas?

hm, maybe you can shut the ports down and wait until someone calls upon you?
one more thing:
it is possible, that you have just powered devices there, so it's not ethernet, but just POE device.

Explore More ContentExplore courses, solutions, and other research materials related to this topic.