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Forum Replies

  1. Hi Rene,
    Very nice lesson. You are the BOSS as always!!

    So can we deploy LFA-FRR for Inter-Area/External Prefix ?? Thx


  2. Hello Zaman

    LFA-FFR for OSPF is defined in RFC 5286. According to this RFC there are several situations where LFA-FRR should not be used for Inter-area and external routes. For example, on Page 7 of the RFC it states the situations where inter-area routes and external routes should not use LFAs.

    I hope this has been helpful!


  3. Hi Laz ,
    Thanks for your valuable reply .
    I cant understand the tie breakers . It will check one by one like BGP attribute do ??

    R1#show running-config all | incl break
     fast-reroute per-prefix tie-break primary-path index 10
     fast-reroute per-prefix tie-break interface-disjoint index 20
     fast-reroute per-prefix tie-break lowest-metric index 30
     fast-reroute per-prefix tie-break linecard-disjoint index 40
     fast-reroute per-prefix tie-break broadcast-interface-disjoint index 50 

    Could you please help me to understand clearly ?


  4. Hello Zaman

    The tie breakers will be checked based on the number found after the index keyword. That number is essentially a priority index. The lower the number, the more important the attribute. So the order the attributes will be checked will be in ascending order of the index number.

    Each tie breaker will eliminate paths with specific attributes. The attributes indicated in your example eliminate the following paths:

    Primary-path—Eliminates candidates that are not ECMPs
    Interface-disjoint—Eliminates candidates sharing the same interface with the protected path
    Lowest-metric — Eliminates the path with the lowest metric
    Linecard-disjoint—Eliminates candidates sharing the same linecard with the protected path
    Broadcast-interface-disjoint — Eliminates candidates sharing the same interface and the broadcast network connected to it

    You can find more info at this Cisco documentation.

    I hope this has been helpful!


  5. Hello Rene,

    Great lesson as always and very helpful to understand. Please let me know what router and IOS version I can use to test in GNS3.


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