Help Regarding CDP Adv. from 2950?

[imran_mcse]

I have a lab setup, I am using Cisco 2610XM and Cisco 2522. Both are connected via ethernet ports to the Cisco 2950 Switch.

When i run the show Cdp neighbours command on Cisco 2522 it shows the Cisco 2610XM and 2950 Switch in its neighbours list, Also when i run this same command on Cat2950 it shows the 2522 and 2610XM in its nieghbours list,

But problem is this that when i show the same command on 2610XM it only shows the 2522 as nieghbour, it did't show Cat 2950 in its nieghbours list.

Why is this. Please Help?

[glen.grant]

If you have single connections from the 2610 and 2522 down to the 2950 you should see single cdp neighbors of the switch in their table and on the 2950 you should see both the 2610 and the 2522 . Don't know how you would see the 2610 from the 2522 . You shouldn't see the 2522 from the 2610 unless you have these set up in a triangle type config .

[imran_mcse]

i have connected both routers with Back to Back Serial cable so thats why both are being shown in their neighbours.

but why 2610XM is not showing 2950 however he has direct fastethernet connection to 2950?

[Kevin Dorrell]

CDP works at link level only. It will see only the router or switch it is directly connected to. Routers cannot see each other through a switch. Each router sees the switch only, the switch sees the connected routers only.

CDP is reciprocal. If A sees B, then B must see A, otherwise something is very very wrong.

So, your routers are connected with a back-to-back serial cable as well, so they should see each other on that back-to-back cable.

Perhaps you cold post the outputs from the show cdp neighbor or even show cdp neighbor detail commands on all three boxes.

Kevin Dorrell

Luxembourg

[glen.grant]

I have seen this once and when I did a "clear interface x/x and this seemed to fix it . You may be seeing a bug .