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UDLD Questions 2

November 25th, 2018 in SWITCH 300-115 Go to comments

Question 1

Question 2

Question 3

  1. MrK
    December 14th, 2018

    Not sure about the answer to Question 2 (Even without an exhibit):

    Question 2

    A question about UDLD port disable.

    A. When a link is repaired, the administrator must enter udld reset command to recover disabled interfaces.
    B. When a link is repaired, the administrator must enter err-disable recovery cause udld command to recover disabled interfaces.
    C. UDLD puts the port in STP inconsistent port mode.
    D. ?

    Answer: C

    In normal mode, if the link state of the port was determined to be bi-directional and the UDLD information times out, no action is taken by UDLD. The port state for UDLD is marked as undetermined. The port behaves according to its STP state.

    In aggressive mode, if the link state of the port is determined to be bi-directional and the UDLD information times out while the link on the port is still up, UDLD tries to re-establish the state of the port. If not successful, the port is put into the errdisable state.

    Source: https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10591-77.html

  2. Dave
    January 8th, 2019

    Indeed, good answer is A, even if B could eventually be valid too. Please correct this.

  3. Anonymous
    January 30th, 2019

    Is there’s any body know what is Q2 and the correct answ

  4. oK
    April 13th, 2019


    I believe A is correct. If the link is repaired you can recover it with UDLD reset.
    B is partially correct. If you wanted to use err-disable recovery cause udld, you would do it from the start and the port would already be recovered.
    C. UDLD only puts the port in errdisable in aggressive mode. In normal mode, no actions are taken.

    I believe
    A is correct

    B is usable
    C is not correct

    udld reset = Reset all ports disabled by UDLD.

    The errdisable recovery cause udld global configuration command = enables the timer to automatically recover from the UDLD error-disabled state, and the errdisable recovery interval interval global configuration command specifies the time to recover from the UDLD error-disabled state.


  5. Anonymous
    May 26th, 2019


    I agree with everyone here. I think the problem is the missing information and the likely half-answers available. For that one just understand how the port recovers with udld.

    With the “udld reset”, an admin can manually recover the interface after a repair.
    With the “err-disable recovery cause udld” the interface would come back up after the default 5 min timer expires.

    As for STP inconsistent mode, correct me if I am wrong, but isn’t that when Loop Guard is enabled and the port is not receiving BPDUs, causing the port to go into a blocking state (meaning it has nothing to do with UDLD)?

  6. Henry
    May 26th, 2019

    Regarding Q2
    C is referring to loop guard

  7. Z-A-M
    June 7th, 2019

    Regarding Q2.

    Agree with the fact that answer C have no link with the UDLD protocol…

    A a B is not good for me because of the “must” word.

    So maybe the answer is D : ?

  8. Efiko
    September 21st, 2019

    Looking at the Cisco link shared by some of the previous guys that commented, you can clearly see that besides the “udld reset” command, there are 4 other methods that can be used to recover the disabled interface.

    If the word “must” was taken out, I would have confidently said the answer is “A” because the command in “B” should be “errdisable recovery cause udld” and not “err-disable recovery cause udld”.

  9. Dmytro
    November 11th, 2019

    Q2 answer C is wrong because UDLD can put port to error disable but NOT to STP inconsistent.
    Read more about it:

    So I think that right answer is A.

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