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New Member

sh cdp neigh | Shows physical int

Hi Experts

i have connected two switches together using a trunk underlying Port-channel to maximize the bandwidth , when i use sh cdp neigh i saw the physical interfaces ? pls clarify




sh cdp neigh | Shows physical int

  Thats normal  ,   why would you think it's not ?   You are not going to know where it is connected if it didnt show the ports on the far end  which is part of the purpose of cdp.


sh cdp neigh | Shows physical int

I think the question is why does CDP display physical information if it's a Layer-2 Protocol?

New Member

sh cdp neigh | Shows physical int

Hi Guys

yes,why the physical interfaces not the end to end port-channel on the cdo neigh???

sh cdp neigh | Shows physical int

The main purpose of CDP is to tell you about the physical connection to the neighbour. In fact it is very useful like that because it can tell you if your cabling is correct. As for being layer-2, I suppose you could say it is a link-layer protocol.

Consider what happens if you have cabled wrongly, and your two links actually go to different switches. Actually, that might even be correct if you are using VSS on 6500 or vPC on Nexus. But which of the two neighbours would you say was the neighbour on the port-channel?

If you are using LACP or PAgP, there are other ways of finding out who is at the other end of the port-channel.

Kevin Dorrell


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