How to test UDLD ?

[kycheong]

Is there any way to test UDLD ? as it's operate at Layer 2, by disconnecting one core of fiber wouldn't be able to test that as in this case Layer 1 is down.

Thanks

Kok Yong

[milan.kulik]

Hi,

AFAIK, UDLD was design to detect wrong cabling, e.g.

So it requires the port to be L1 up.

You can test it with following scenario:

Connect two switches to a central one via fiber optics GBICs.

On the central switch: swap Rx SC connector between the GBICs. Each fiber will be connected to one GBIC with one SC connector and to the other GBIC with the second SC connector, i.e. the edge switch will sent data to port Gi0/1 but receive data from Gi 0/2, e.g.

You will get cable mismatch this way with L1 up on all connectors (and STP not detecting any problem, I hope).

UDLD should detect this cabling mistake and disable the ports.

Regards,

Milan

[baozhang]

Easier solution:

What you would need is just 2 pairs of fiber cable (SC/LC or whatever) and 2 back to back switches with 2 ports available on each switch under test. Here's the test topology:

(Excuse the ugly graph)

********************************************

and output will be something like this:

RP/0/RSP0/CPU0:R1#sh ethernet u i
Fri Jun 30 21:06:48.283 GMT
Device ID: 08:96:ad:6a:0c:e7
Device name: R1

Interface TenGigE0/0/1/2
Port state: Error-Disabled (Unidirectional connection)
Main FSM state: UDLD inactive
Detection FSM state: Unidirectional
Message interval: 7 seconds
Timeout interval: 5 seconds
Destination MAC: 01:00:0c:cc:cc:cc

Neighbor 1
Device ID: 08:96:ad:69:57:c7
Device name: R2
Port ID: Te0/0/1/2
Message interval: 7 seconds
Timeout interval: 5 seconds

RP/0/RSP0/CPU0:R1#
RP/0/RSP0/CPU0:R1#sh int te0/0/1/2
Fri Jun 30 21:07:10.806 GMT
TenGigE0/0/1/2 is error disabled, line protocol is administratively down
... ...