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GLBP Questions 2

November 15th, 2018 in SWITCH 300-115 Go to comments

Question 1

Explanation

With GLBP, up to four gateways can be used simultaneously -> A is correct.

The GLBP group weighting can be automatically adjusted by tracking the state of an interface within the router. If a tracked interface goes down, the GLBP group weighting is reduced by a specified value. Different interfaces can be tracked to decrement the GLBP weighting by varying amounts -> E is correct.

Question 2

Question 3

Question 4

Explanation

When the routers are configured to a GLBP group, they first elect one gateway to be the Active Virtual Gateway (AVG) for that group. The election is based on the priority of each gateway (highest priority wins). If all of them have the same priority then the gateway with the highest real IP address becomes the AVG. The AVG, in turn, assigns a virtual MAC address to each member of the GLBP group. Each gateway which is assigned a virtual MAC address is called Active Virtual Forwarder (AVF). A GLBP group only has a maximum of four AVFs. If there are more than 4 gateways in a GLBP group then the rest will become Standby Virtual Forwarder (SVF) which will take the place of a AVF in case of failure.

Comments
  1. MrK
    December 14th, 2018

    Don’t think F is the answer to Question 3:

    Question 3

    A question related to FHRP defaults.
    A. Preemption is enabled
    B. Only GLBP use load-balancing for multiple router
    C. Only GLBP use MAC address router BIA (Burned In Address)
    D. Only if the AVG fail, standby become the new active router
    E. If standby router has higher priority it becomes the new active router
    F. If standby AVG has higher priority it becomes the new active router
    G. Something on or about VRRP

    By default, the GLBP gateway preemptive scheme is disabled. A backup virtual gateway can become the AVG only if the current AVG fails, regardless of the priorities assigned to the virtual gateways.

    Best Answer is: D. Only if the AVG fail, standby become the new active router

    Source:
    https://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ft_glbp.html#wp1039649

  2. trueteller
    December 29th, 2018

    @MrK
    In GNS3 I have tested scenario where I had connected 4 L3 switches with one GLBP group. All of them had the same priority. Switch that had highest IP address (SW4) on the interface became AVG. Remember that preeption is disabled by default. I have added SW5 with highest IP address and connected it to rest of them. Then this switch instantly became AVG.
    This might be a glitch in GNS3 however this shouldnt happen as far as I know.

    This actually proves that F could be correct but I cannot believe it 100% sure. That would be nice if somebody could check this with real equipment.

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  4. pepito grillo
    January 13th, 2019

    indeed, question 3 is for sure D, as preemption is not enabled BY DEFAULT on glbp avg election.

  5. @youssouf
    February 2nd, 2019

    In EVE I have tested scenario where I had connected 4 ROUTER with one GLBP group. All of them had the same priority(100). Switch that had highest IP address ROUTER-4 on the interface became AVG. I have added ROUTER-5 with highest IP address and configured priority 150 (has higher priority) connected it to rest of them. Then this switch instantly became standby.
    Best Answer is: D. Only if the AVG fail, standby become the new active router

  6. Michael
    February 26th, 2019

    I too think D is the right answer for Q3.

  7. MrTadge
    April 9th, 2019

    Preemption is ON by Default with GLBP with regards to the AVG, so a stanby with a higher priority will become Acitve.

    F is the correct answer.

  8. Name
    May 18th, 2019

    Q3 – “Like with HSRP, but unlike with VRRP, GLBP has preemption disabled by default. So, by default, another router cannot take over an active role until the current active router fails. You need to explicitly enable this feature”.
    CCNP Switch 300-115 Foundation Learning Guide, pg 287

    @MrTadge, Preemption is OFF by Default with GLBP

    D is the correct answer.

  9. Abreham
    July 9th, 2019

    Q3 – preemption is disabled for AVG by default. It is enabled by default only for AVF

    I think the answer is D

  10. edd
    July 18th, 2019

    “By default, the GLBP gateway preemptive scheme is disabled. A backup virtual gateway can become the AVG only if the current AVG fails, regardless of the priorities assigned to the virtual gateways. You can enable the GLBP preemptive scheme using the glbp preempt command. Preemption allows a backup virtual gateway to become the AVG, if the backup virtual gateway is assigned a higher priority than the current AVG.”

    https://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ft_glbp.html

    D is right answer.

  11. Nickname
    August 16th, 2019

    Q3

    A backup virtual gateway can become the AVG only if the current AVG fails, regardless of the priorities assigned to the virtual gateways.

    Based on this statement i think D is the best answer.

    Is this correct?

  12. CP
    August 19th, 2019

    Q3
    Premption is enabled by default for AVFs and not for AVG. For AVG, premption is disabled by default. Hence D is the correct answer

  13. SMK
    September 18th, 2019

    Can anyone tell the correct answer for this question? D or F

  14. Tony Montana
    September 19th, 2019

    From https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipapp_fhrp/configuration/xe-3s/fhp-xe-3s-book/fhp-glbp.html

    By default, the GLBP virtual gateway preemptive scheme is disabled. A backup virtual gateway can become the AVG only if the current AVG fails, regardless of the priorities assigned to the virtual gateways. You can enable the GLBP virtual gateway preemptive scheme using the glbp preempt command. Preemption allows a backup virtual gateway to become the AVG, if the backup virtual gateway is assigned a higher priority than the current AVG.

  15. abdullah
    October 3rd, 2019

    q3
    B and D are correct.

  16. xela
    October 12th, 2019

    @certprepare can you clarify question 3

    thanks

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