Errdisable

[sivam siva]

Hello 

can anyone answer the below question?

A network engineer has just configured a fiber connection between two switches. The connection has been set up as an EtherChannel. Shortly after
powering the device on, the fiber port err-disables. What is the most likely cause?

A. UDLD standard mode has been set up on the interface.
B. Spanning tree has disabled the port.
C. UDLD aggressive mode has been set up on the port.
D. The EtherChannel configuration is incorrect.

I believe Answer D
but many people says Answer: C

Why D is correct:

Assume if UDLD aggressive mode is enabled. when device boot they don’t have any captured information about neighbor initially until another end device sends UDLD echo back. so it’s not possible to errdisable while booting.

The question says Etherchannel has just configured, so there could be a misconfiguration,
Note: “spanningtree etherchannel guard misconfig ” is enabled by default on cisco switches,
so answer D could be correct

I have not tested this in Lab because I don't have enough Fiber module

Any suggestion, please …

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Thanks 

siva

[Reza Sharifi]

Hi,

See table 29-1.  Fiber is layer-1 and UDLD usually deals with fiber issues.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_52_se/configuration/guide/3750scg/swudld.html

HTH

[Giuseppe Larosa]

Hello Siva,

I agree with Reza.

I had a case where after a blackout one C6800 chassis member of a VSS was powered off for many hours.

The VSS had a four tengiga bundle versus another C6800 VSS, when the chassis came back up some ports have gone in error disable for UDLD ( If I remember correctly).

we enabled automatic recovery on the VSS that was affected by the blackout ( it was enabled on the other VSS).

Hope to help

Giuseppe

[Leo Laohoo]

It cannot be A or C because UDLD is not enabled (by default) and nowhere in the question was UDLD mentioned.
It cannot be B because, hey, Etherchannel.
The only one left "standing" is D.

[sivam siva]

Thank you very much for all 

I have tested this in but couldn't get the expected result for UDLD.

If anyone tells how to do this, it will be very helpful (I have a good understanding of UDLD).

Still many questions on debate :-(