CDP not showing a connected swtich.

[Sean Graham]

We have a 6509 and a 3750 that do no see each other through CDP. The 6509 has other switches connected to is and it sees them just fine. CDP is enabled on both.

How do I get them to see each other through CDP and could this cause a problem if they don't know the connection is a switch? The link is trunked.

Thanks in advance.

[Richard Burts]

Sean

If CDP is enabled on both ports and if both switches do not see the other as a CDP neighbor then I believev that it may indicate that there is some layer 2 issue in the connection of these ports. If there is a layer 2 issue then not seeing each other as neighbors would probably mean that there was a problem and other kinds of data might not be able to be forwarded over this connection.

As a starting point could you post the output of show port of both switches. It might also be helpful if you would post the configuration of both ports.

HTH

Rick

[p.calcaterra]

Hi,

I had some similar problem with CDP on 650x and trunk links. Mainly the problem is related to CDP that communicates only using VLAN 1, so if the VLAN 1 is removed form the trunk the CDP works oddly.

I didn't have any experience between 650x and 3750, but between 6506 and 7200 router, the CDP neighbor command show a correct result, except the 6506 IP address that is 127.0.0.12, the SPV internal loopback address.

The only workaround is to enable VLAN 1 on trunk.

If you cannot do it due to spanning tree issues, you must substitute the use of VLAN 1 with another VLAN, but is a hard job.

HTH

Paolo.

[Sean Graham]

Well, after looking at the config further, it would help if CDP was actually enable on the ports on card 9 on the 6509. It is now working.

Thanks for the help...

[Richard Burts]

Sean

Thanks for posting back to the forum indicating that the problem was fixed and what the solution was. It makes the forum more useful when we can read about a problem and see what solved the problem.

I also believe that your posting contains a useful lesson for us about troubleshooting: always go back and check assumptions about whether things are really correctly configured or not.

HTH

Rick