Traceroute MAC not working consistently

[robschn]

Hi All,

Is there a reason that a traceroute mac would work from some MACs and not others? It seems VERY inconsistent for me. Sometimes the same MAC will work then randomly not work.

Here's what I get:

CiscoL3Device#traceroute  mac 309c.0000.b1b0 309c.0000.b1b0
Unable to send a l2trace request to 172.16.0.1. Timed out
Layer2 trace aborted.

CDP is enabled on every switch and I can perform a traceroute mac on other MACs from the same switch.

Any ideas?

[luis_cordova]

Hi @robschn ,

Check this link, maybe can give some help:

https://www.ciscozine.com/how-to-trace-mac-address/

Regards

[robschn]

Thanks for the article, lots of good information. I'll do some digging and see if I'm missing anything

[robschn · Accepted solution]

I figured it out!

L2 traceroutes can only work if all the switches are in the same network. If you have a VoIP phone or another switch-like thing in between the device and access switch, it will fail.

The clue for me was the "Unable to send a l2trace request to 172.16.0.1." 172.16.0.0 is my voice VLAN, so it's a different network from the management VLAN that my switches use.

Hope this helps someone in the future!