question about CDP vs C6506 CatOS switch

[xine xine]

Hi !

I'm looking to enabling CDP in the environnement, sometimes in the neighboring switch or router it's neighbor is not appearing when is connected to a c6506 switch.....  Some equipement who have c6506 switch show there neighbor but it's not an absolute rule !  But each time on the C6506 switch I see always neighbors switch or router.

CatOS is running is 6.4(11).

Someone could explain to me ?

Thanks !

[glen.grant]

  If its enabled on the interfaces on both sides  you should see it .   I have seen instances where someone has not setup a trunk link correctly where cdp won't work right .

[Alvaro Garcia]

As mentioned above, a trunk/VLAN misconfiguration could be prevent the devices to see each other with CDP.

CDP packets are always forwarded on trunks with a VLAN 1 tag. This is the case even if VLAN 1 has been cleared from the trunks and is not the native VLAN. Clearing VLAN 1 for user data has no impact on control plane traffic that is still sent using VLAN 1.

I would suggest to check that both sides of the link are properly configured.

In addition, not all Cisco devices have CDP enabled by default so you may like to check that as well.

[xine xine]

Hi !

I have one problem with our explanation.....  

I have some access link ((both side are not setup as an trunk and are on different VLAN than VLAN1) are working well between 1 router and the 6506 switch.

But some other with same configuration do not !  (access-link between router and C6506 on different VLAN than VLAN1)

But, If I remember correctly all trunk link are working good about this issue ! I sure we having 2 access-link with this problem, and I'm sure CDP is activated on both side of the link (on the router and on the switch)

Thanks !