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UDLD Questions

July 8th, 2017 in SWITCH 300-115 Go to comments

Question 1

Explanation

UDLD is a Layer 2 protocol that enables devices connected through fiber-optic or twisted-pair Ethernet cables to monitor the physical configuration of the cables and detect when a unidirectional link exists. All connected devices must support UDLD for the protocol to successfully identify and disable unidirectional links. When UDLD detects a unidirectional link, it administratively shuts down the affected port and alerts you. Unidirectional links can cause a variety of problems, including spanning-tree topology loops.

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3550/software/release/12-1_19_ea1/configuration/guide/3550scg/swudld.html#wp1019932

Question 2

Explanation

A unidirectional link occurs whenever traffic sent by a local device is received by its neighbor but traffic from the neighbor is not received by the local device.

UDLD supports two modes of operation: normal (the default) and aggressive. In normal mode, UDLD can detect unidirectional links due to misconnected interfaces on fiber-optic connections. In aggressive mode, UDLD can also detect unidirectional links due to one-way traffic on fiber-optic and twisted-pair links and to misconnected interfaces on fiber-optic links.

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3550/software/release/12-1_19_ea1/configuration/guide/3550scg/swudld.html

Question 3

Explanation

When unidirectional link occurs, UDLD can put that port into errdisable state (same as shutdown). The administrator must manually shut/no shut to bring that interface up. If we want the interface to automatically recover then configure the “errdisable autorecovery”. For example:

errdisable recovery cause udld
errdisable recovery interval 30

By doing so, the port will be place back in up state (no err-disabled state) after 30 seconds, if the port still has violation it will be placed again in “err-disabled” state, otherwise it will remain in up state.

Question 4

Explanation

UDLD aggressive mode is disabled by default. Configure UDLD aggressive mode only on point-to-point links between network devices that support UDLD aggressive mode. With UDLD aggressive mode enabled, when a port on a bidirectional link that has a UDLD neighbor relationship established stops receiving UDLD packets, UDLD tries to reestablish the connection with the neighbor. After eight failed retries, the port is disabled.

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/15-0SY/configuration/guide/15_0_sy_swcg/udld.html#wp1027627

Question 5

Question 6

Question 7

Question 8

Question 9

Explanation

The Cisco-proprietary UDLD protocol monitors the physical configuration of the links between devices and ports that support UDLD. UDLD detects the existence of unidirectional links. When a unidirectional link is detected, UDLD puts the affected port into the errdisabled state and alerts the user. UDLD can operate in either normal or aggressive mode.

UDLD is a Layer 2 protocol that works with the Layer 1 protocols to determine the physical status of a link. At Layer 1, autonegotiation takes care of physical signaling and fault detection. UDLD performs tasks that autonegotiation cannot perform, such as detecting the identities of neighbors and shutting down misconnected LAN ports. When you enable both autonegotiation and UDLD, Layer 1 and Layer 2 detections work together to prevent physical and logical unidirectional connections and the malfunctioning of other protocols.

UDLD aggressive mode is disabled by default. Configure UDLD aggressive mode only on point-to-point links between network devices that support UDLD aggressive mode. With UDLD aggressive mode enabled, when a port on a bidirectional link that has a UDLD neighbor relationship established stops receiving UDLD packets, UDLD tries to reestablish the connection with the neighbor. After eight failed retries, the port is disabled -> D is correct.

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/configuration/guide/book/udld.html

Comments
  1. yusuf cameroon
    April 26th, 2015

    i need to write exam 300-115 next week . are this questions enough to pass the exam ?

  2. CCAr Certified
    May 15th, 2015

    QUestion 5 should be E

  3. Bacho
    July 2nd, 2015

    CCAr Certified could you explain why q5 should be E?

  4. Papi
    July 4th, 2015

    But we dont have E as an option

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    July 18th, 2015

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  6. Anony
    August 13th, 2015

    Where are the questions??
    I can’t see any of questions..
    only the explanatios are avaialabel

  7. Chia’tAtA
    August 24th, 2015

    Just from taking the switch exams. Scored 950 thanks to certprep.
    only one new question on VTP.

  8. $!L@
    October 8th, 2015

    Chia’tAtA congratz man…

  9. A
    October 21st, 2015

    @certprepare

    Your explanation to Q3 says ‘The administrator must manually shut/no shut to bring that interface up.’

    I’m not sure that’s entirely correct for UDLD. Should be ‘udld reset’. Refer to the cisco links in explanation of Q1 & Q2

  10. Sundar
    November 26th, 2015

    Hi,

    Where are questions?

  11. Ali
    February 15th, 2016

    Hi,

    I’m wondering about the questions as well. I only see answers. Can someone help me out! Thanks in advance!

  12. CLE
    March 10th, 2016

    Hi all,

    Can someone send me the latest switch dump to “dooeebear” at hotmail dot com.

  13. Jane
    March 22nd, 2016

    could somebody send me the dumps 191q please. It will be a big help. I do request. Thanks in advance. my email address

    jane_woken52 @ yahoo.com

  14. FustratedCCNPLoser
    March 26th, 2016

    My exam was taken on 3/25/2016 as I ended up with a humiliating 643/1000. All my study material was from the CiscoPress eBook (300-115), CBT Nuggets, VCE dumps (191q) and Certprep (SWITCH_JULY_2015). I put in 6-7 study hours a day for nearly a month to pass 300-115 with extreme confidence, but I was shot down when I was roasted by the exam. The latest dumps from this site only covered about 25% of the questions given, but all the Lab Sim simulation were correct as I had LACP with STP / HRSP / AAA. I was easily able to finish the lab sims on the exam with success but fell way short when it came the questions with educated guesses. I would like to know if anyone can help me out to receive the latest dumps soon. Thanks. c_brotha @ yahoo.com

  15. sd
    March 27th, 2016

    Hi all,
    can anyone plz confirm if dumps are still valid?
    i have 191q and SWITCH_Feb_2016

  16. master
    December 20th, 2016

    how many question for the simulation exams? and what are those?

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  19. scaryg
    August 2nd, 2017

    does anyone have the questions to these answers? thanks

  20. vivian
    August 2nd, 2017
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