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Forum Replies

  1. Quick question Rene on this topic. The lab works fine as I followed along with my own topology. But I am just wondering why R2 should send the community only to R3? For example, you mentioned: “R2 sets the community so make sure that it advertises it to R3”… why should it not send the community to R4 as well. I know R4 is in another AS, but R4 would have filtered it out as well, wouldn’t it?

  2. Hi,

    I am confused about BGP selecting path.Here topology

    http://i65.tinypic.com/2r7n9t3.jpg

    R5 is in sub-AS 45.And advertise prefix 9.9.9.9/32.

    R5#sh ip bgp             
    BGP table version is 14, local router ID is 5.5.5.5
    Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
                  r RIB-failure, S Stale
    Origin codes: i - IGP, e - EGP, ? - incomplete
    
       Network          Next Hop            Metric LocPrf Weight Path
    *> 9.9.9.9/32       0.0.0.0                  0         32768 i
    *> 192.168.12.0     2.2.2.2              
    ... Continue reading in our forum

  3. Hi Ler Sak,

    BGP doesn’t differentiate between confed-internal or confed-external. When the two paths are the same, it’s up to the router ID to decide which one will be selected.

    Here’s an example from the topology I used in this lesson:

    R4#show ip bgp 55.55.55.55/32
    BGP routing table entry for 55.55.55.55/32, version 5
    Paths: (2 available, best #1, table default)
    Flag: 0x800
      Not advertised to any peer
      Refresh Epoch 1
      (35)
        5.5.5.5 (metric 2) from 2.2.2.2 (2.2.2.2)
          Origin IGP, metric 0, localpref 100, valid, confed-internal, best
          rx pathid: 
    ... Continue reading in our forum

  4. Hello,

    Just a few remarks/questions for this lesson.

    I believe R2 should advertise the 192.168.12.0/24 network (network 192.168.12.0 mask 255.255.255.0), otherwise the other routers will not know about 192.168.12.1 as next-hop for 1.1.1.1 (I checked the confederations lesson).
    Also on R3 the neighbor command for R6 should be .2 instead of .6.

    One question is how will R5 select the path towards 1.1.1.1? In your previous post I saw that Router ID is selected, but shouldn’t be attribute 7 (eBGP path over iBGP path)?. I believe that confed-external behaves like eBG

    ... Continue reading in our forum

  5. Hello Stefanita,

    I just made some changes to this lesson:

    I fixed this in the topology picture.

    ... Continue reading in our forum

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