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Simulating UniDirectional Link Failure

d.hodgson
Level 1
Level 1

Hi folks,

I may be losing the plot but can I simulate unidrectional link failures using fibre to help my CCNP studies? I thought it would be a simple matter of pulling out just the rx on one of my switches but that brings the int down. Is this how it's supposed to work?

I want to do this to look further into udld.

thanks

Dave

4 Replies 4

Nagendra Kumar Nainar
Cisco Employee
Cisco Employee

You can use PACL to simulate unidirectional link failure. UDLD uses 0100.0ccc.cccc as destination MAC address.

So configure a PACL denying this mac address and apply the same to the interface on which you need to simulate the link failure.

HTH,

Nagendra

Thanks Nagendra,

I'll look up PACL.

Now what about the fibre failure I simulated, is expecting that to be a unidirectional link failure a wrong assumption?

ta

Dave

h.parsons
Level 3
Level 3

It is my understanding that your assumption is right. One thing to note is that both switches will have to establish a bidirectional state once before UDLD will shutdown an interface. Try connecting them and do a "show udld neighbors"

shaktik
Cisco Employee
Cisco Employee

I know its quite late for the answer, but just for other people visiting here.. I was just thinking that attaching the Rx to a higher voltage source should work out since it should complete the loop

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