R&Sv5 Workbook IGMP Timers Question


Hello,



maybe I have an understanding-issue:



The question was:

  • Configure the designated IGMP querier on VLAN 146 so that failed multicast traffic receivers are detected and removed within 20 seconds.
  • Every active receiver should respond to general IGMP queries within 4 seconds.



my solution was

  • ip igmp query-max-response-time 4
  • ip igmp query-interval 16



valid solution was

  • ip igmp query-interval 20 ...
  • ip igmp query-max-response-time 4



But when they ask to detect failed receivers wihtin 20 seconds, I should count the query-max-response-time additional to that or I am wrong?

Should I ask the proctor such questions in the real exam?



Thanks

Steven

Comments

  • Hi dq2812 and All,

    Haven't labbed up for a while.  Good question.  Here is my understanding, please check and correct:

    "ip igmp query-max-response-time"

    This command controls the period during which the responder can respond to an IGMP query message before the router deletes the group. CISCO

    Example:

    |--|--|--|--|--|--|--|--|--|--|--|--|--|--|--...  

    0  d 10  d 20  d 30  d 40  d 50  d 60  d  0          

    Query interval is 10; Query fires at 0, 10, 20, 30 40 etc

    "d", max-response time, set to 5; expires at 5 for query 0, 15 for query 10, 25 for query 20, etc; 

    "d" is when the group dies if clients are not responding to server's query; "d" happens to equal max-response time.

    As you can see, "d" has same interval as Query interval.  If you vary "d" between 0 and 10, once set, will have an interval equal to Query interval.

    Point being, "d" interval is totally dependent (?) on Query interval.  INE's answer is to set Query interval to 20, which we know will also set dead interval to 20.  Within 20 seconds detect a dead group.  To track individual members of a group, and not just the total absense of group members,  would require further configuration.?

    Cheers // RandyB

     

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