cdp on cisco switches

[carl.townshend]

Hi All

With CDP,  do switches only show directly attached devices ? i.e the cdp neighbour info does not get passed to the next switch ?

[Georg Pauwen]

Hello,

correct. Indeed CDP only collects information from directly connected neighbors.

I think there is a CDPv2 now that can discover stuff like native Vlan mismatches and port speed/duplex mismatches as well. However, still only on directly connected devices.

[Kasun Bandara]

Hi,

CDP works with directedly connected and CDP enabled ports. immediate devices will share details such as, Device model, capabilities, native VLAN, IP address, etc in V2. these details will not pass to next device and using only for neighbor details discovering. you can easily use CDP to identify/discover network connectivity without physical visit to the devices if CDP enabled.

rate this and mark as answer if this resolved your concern

[balaji.bandi]

adding to other comments, CDP never show any information, which do not have any visibility of directly connected device.

what is the use case ?

[Joseph W. Doherty]

At noted by others, CDP will not transit through Cisco CDP capable switches, however, it might transit though "dumb" and/or non-Cisco switches.  It can also, if so configured, transverse some Cisco tunnels.

The forgoing would be examples of where devices are not physically directly connected.

[Giuseppe Larosa · Accepted solution]

Hello @carl.townshend ,

just to add to other comments:

if you put a non Cisco switch that does not support or run CDP on the path you can see multiple CDP neighbors on a single Cisco switch port ( if all of them connect to this device)

CDP is actually a proprietary protocol that uses a multicast destination MAC address as a result of this there is the special corner case that I have described above.

Edit:

I hadn't read @Joseph W. Doherty  post but we are saying almost the same thing

Hope to help

Giuseppe