CDP quick question

[Federico Coto Fajardo]

Hi quick question, 

Scenario looks like this: 

ASR1k --- ASR9k -- ASR9k --- ASR1k 

The connection between ASR1ks are l2transport on the ASR9k side. Therefore we see the ASR1k as a CDP neighbor from the other ASR1k. This is fine, but my question is why we also see the ASR9k as a CDP neighbor from the ASR1k via the same port. I thought CDP should either be tunnelled or not. 

So, CDP on the ASR1ks show both the other ASR1k (which is fine), but it also show the directly connected ASR9k via the same interface. Is this normal? 

Thanks, 

Federico.

[Adam Born]

Disable CDP on the ASR 9k for that interface.

config t

cdp
  interface x/x/x
    no cdp

[Federico Coto Fajardo]

Adam, thank you. That should remove us from seeing the 9k from the 1k I believe. 

But I forgot to mention that the behaviour changed since IOS XR 4.2 (that's what I was told and we're running now 4.3). 

So, I'm looking if there's a DDTS or for some reason the behaviour of CDP changed between codes?

[Adam Born · Accepted solution]

This document might help explain the differences in 4.2 and 4.3

https://supportforums.cisco.com/document/60506/asr9000xr-how-cdp-handled-l2-and-l3-scenarios

[xthuijs]

Adam, thanks for taking care of this and you are correct.

We made a change, based on popular demand to peel out certain control traffic out of the untagged EFP in the existence of MST/CDP configuration.

If the service is not configured locally on the l2tranporting interface then those packets are subject to the EFP transport.

cheers!

xander