show cdp neighbors doesn't show all routers

[ianbla]

When I run the command 'show cdp neighbors' on my gateway router (3640) I only get a couple of routers listed, I currently have 4 connected and up/running. Is there a reason why they would not be listed?

thanks
Ian.

 

[SF18C]

Are you connected to any devices by means of a switch? CDP packets are not passed through a switch, you can only see devices that are directly attached to the device you are 'sh cdp nei' on. On a router connected to a switch you will not see other devices connected to the switch.

Hope that helps

Steve

 

[ianbla]

No,

All routers are directly connected to the 3640. any ideas?

cheers
Ian.

 

[Guest_imported]

Check to see it CDP is enabled on your directly connected neighbors interface. You can enable CDP on the interface by entering the enterface config and entering "CDP enable".