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Beginner

Traceroute MAC not working consistently

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?

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Beginner

Re: Traceroute MAC not working consistently

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!

3 REPLIES 3
Advocate

Re: Traceroute MAC not working consistently

Hi @robschn ,

 

Check this link, maybe can give some help:

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

 

Regards

Beginner

Re: Traceroute MAC not working consistently

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

Re: Traceroute MAC not working consistently

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!

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