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Forum Replies

  1. Hi Hamood,

    GNS3 makes this really simple. You can right-click on any interface and select “capture”. It will automatically start Wireshark and show you the traffic that flows through the link.

    Rene

  2. Hi Dhanu,

    The second update message is empty and is used to indicate that all routes have been sent. You can read more about it in RFC4724:

    An UPDATE message with no reachable Network Layer Reachability Information (NLRI) and empty withdrawn NLRI is specified as the End-of-RIB marker that can be used by a BGP speaker to indicate to its peer the completion of the initial routing update after the session is established.

    Rene

  3. Hello Rene,
    I have couple of questions regarding the timers used in BGP. Correct me if I am wrong. Bgp uses keepalive of 60 seconds and hold down timer of 180 seconds by default. So here the keepalive works like hello messages like in ospf and hold down timer works like dead timer in ospf. Am I correct? Let’s say Router A is peering with Router B by EBGP and router A is using keepalive of 60 seconds and hold down timer of 180 seconds whereas Router B is using keepalive of 100 seconds and hold down timer of 300 seconds. In this case, what would be the negotiated

    ... Continue reading in our forum

  4. The default keepalive and holddown timer are 60 and 180 seconds (3x the keepalive):

    R1#show ip bgp neighbors | include keepalive
      Last read 00:00:20, last write 00:00:50, hold time is 180, keepalive interval is 60 seconds
    

    So what happens when you change these? For example, R1 uses a lower keepalive and holddown timer while 192.168.12.2 (R2) uses the default:

    R1(config)#router bgp 1
    R1(config-router)#neighbor 192.168.12.2 timers 10 30 
    

    The end result will be:

    R1#show ip bgp neighbors | include keepalive
      Last read 00:00:08, last write 00:00:08, hold time is 
    ... Continue reading in our forum

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