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Forum Replies

  1. Great lesson, Rene!

    I studied this from the Cisco documentation but they never explained in clear terms what was going on, but you managed it!

    Small typo (should be via interface GigabitEthernet0/1

    Also could you provide the configs for PIC edge, at the end?


    Just came across this quote from Cisco:

    PIC core ensures fast convergence for BGP routes when there is a link or node failure in the core that causes a change in the IGP reachability to a remote BGP next-hop address.

    PIC edge ensures fast convergence to a

    ... Continue reading in our forum

  2. Hello Chris

    Thanks for pointing that out, I’ll let Rene know…

    I’ll also let him know about the request for the configurations for PIC edge.

    The Cisco comment is indeed correct. Even though iBGP is run between PE

    ... Continue reading in our forum

  3. hi Rene and staff,

    i read BGP PIC Core, thanks for this great explanation
    Using hierarchical FIB, CEF (and BGP) are ready to go a very short time after IGP reconverge in the core (ospf in this case)
    You have to configure the simple command “cef table output-chain …”
    Perhaps it is a basic question, but
    in the lesson, it seems that this command has to be configured only on PE routers (PE1, PE2, PE3, PE4) and not on P routers
    Could you explained why ?
    Does the type of FIB on P2 and P1 (flat versus hierarchical) involve the performance of the core too ?

  4. Hello Dominique

    The specific example was within the BGP PIC Core section, which means that we are attempting to decrease convergence time in the event that a core router (P router) fails. Because the PE routers are those that are on the edge of the BGP AS, and they contain the routes to the prefixes at each customer, it is these routers that require the hierarchical FIB enabled. The P routers simply interconnect the PE routers and do not need to know about the multiple prefixes that exist at the customers. So in the event of a core failure, the remaining fun

    ... Continue reading in our forum

  5. Hi Dominique,

    The BGP entries in P2 won’t change since from P2’s perspective, nothing changes:

    P2#show ip bgp
         Network          Next Hop            Metric LocPrf Weight Path
     * ia                  
    ... Continue reading in our forum

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