cdp and 3750 swicth stacks

diannesealey · ‎07-01-2009

I prefer to disable cdp when not explicitly required. However I am currently building a 3750 switch stack. The manual states "cdp discovers the switch stack... The switch stack sends CDP messages to neighboring network devices when there are changes to the switch stack membership, such as stack members being added or removed"

I have seen on several non-Ciscp forums that people seem to disable cdp on such switch stacks and do not mention any issues, but given the above I am sceptical.

My current thoughts are to leave cdp globally enabled but disable on the individual switch interfaces to minimise exposure.

What are others thoughts on this?

wandering_997 · ‎07-01-2009

Do you mean cdp is the requirement of 3750 stack it must meet?

dario.didio · ‎07-02-2009

Hi,

"CDP discovers the switch stack"

This means that (if CDP is enabled) the stack is discovered by neighbouring devices, not the individual switches.

When using a stack, the switches represent one single virtual switch, and it is this that is being discovered by others.

"The switch stack sends CDP messages to neighbouring network devices when there are changes to the switch stack membership, such as stack members being added or removed"

If I'm not mistaken, you can see info about the stack via sh CDP neig detail, and I assume that when members are added or removed, changes will be performed here.

If you don't use CDP, no CDP messages will be send. CDP isn't mandatory for the switch to work, so you can turn it off without a problem.

Please rate if helpful!

BR,

Dario

hobbe · ‎07-03-2009

I agree completely with Dario

I would however like to add that some commands do not work when you disable cdp since they use cdp as a carrier to talk to other stacks.

one example that is quite handy to use that requires cdp if it is over several stacks is the traceroute mac ip ipaddress1 ipaddress2 command.

This command traces the path between two ip addresses and tells you where they are connected.

quite a handy and nice function when problems arise.

so think twice about the pros and cons in your own environment as to why disable it.