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Notable Replies

  1. Rene,

    Great lesson however, I do have a question about prepending AS in ISP-1 because we don't want other ISPs to learn about is that correct?

    64984:0 is a number we get from ISP? It varies from ISP to ISP?
    If we need to add another loopback or network we can use the same community on the customer side which is 64984:0 or do we need something else?

    Please clarify.

  2. Hi Mauro,

    I used send community on the customer router so that ISP1 will see the community that was added to the prefix and could act upon it.

    In this scenario there's no need for ISP2 or ISP3 to see the community value since only ISP1 is doing something with it...if you want ISP2 or ISP3 to see the community value then yes we should add the send community command on ISP1.


  3. mark1 says:


    Is the prefix list defined on the Customer router in the example correct? I had to change it to to get it to work in my testing.



  4. Hi Mark,

    It depends on your loopback interface. In my case, I had a /32 on the loopback which was advertised in BGP:

    Customer#show running-config | section bgp
    router bgp 10
     no synchronization
     bgp log-neighbor-changes
     network mask
  5. Hi Rene,

    very nice introduction to BGP communities. However, I've a little improvement: A hint that communities were only forwarded from second router to a third one if send-community is activated on that neighborhood were be helpful.


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