Basic CDP question

[tinu_karki]

Currently i have CDP enabled on a router and a few switches connected to the router. Doing a "Show CDP neighbor" command on the router brings up nothing. Doing a "show cdp traffic" on the router shows that cdp traffic is being sent but no recieved. On the switches doing a "show cdp neighbor" brings up details of other switches but not of the router. CDP is def enabled on all devices. All devices are cisco. Wots going on? can anyone help?

[arvindchari · Accepted solution]

Might be a version mismatch. CDP has 2 versions.

Use the command show cdp on the router and the switches to confirm if the versions match.

The default mode (if supported) is version 2.

Also make sure there are no access lists blocking cdp going in / out of the router interface connected to the LAN segment

HTH

Please rate posts that help.

Regards

Arvind

[mahmoodmkl]

HI

In addition to arvind post try clearing the interface counters of the particular interdace and verify that weather CDP is enabled for that interface.becoz CDP can be enabled globally as well as at interface level.

Hope this helps

Mahmood

[balajitvk]

Hi Tnu,

I think u haven't enabled cdp at the interface level in the router. Pls. check cdp status at the ports in the router connected to the switches as well as in switches connecting to the router.

Rgs,

[tinu_karki]

Sorry silly question but i thought enabling CDP globally meant enabling for all interfaces? Why would i have to do enable it to individual interfaces if its done globally already if the above statement is true.

[pkhatri · Accepted solution]

Hi,

YOu are correct that when CDP is enabled globally, it enables it on all interfaces. However, you can choose to not run it on specific interfaces. That is what the previous poster is getting at - check that it has not been disabled on the interfaces where you are seeing the issue.

Hope that helps - pls rate the post if it does.

Paresh

[tinu_karki]

Hi Guys,

Thanks for your input. In the end all interfaces on the router were enabled on the router, this was show when running "show cdp traffic" command there was cdp output but no input. The problem was that the port on the switch the router was connected had CDP disabled.