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Forum Replies

  1. Rene,
    Great lesson however, I have questions if we have two ISPs and we would like to route traffic out through ISP-1. It means we need to set up a higher weight on the ISP-1 peering with us and setup a lower weight on the second ISP-2?
    How can we make sure traffic goes out ISP-1 and comes back in using ISP-2?


  2. Hi Hamood,

    That’s right, you can use weight to select the path but this is only for the local router. If you want to influence your entire AS then you’ll have to use local preference:

    To influence how traffic enters our AS we have a couple of methods, the first one is MED:

    This is only useful when you are multihomed to a single ISP. These two methods will help if you are multihomed to different ISPs:

    Hope this helps!


  3. Hi Rene,

    Off topic, I don’t see topic conditional advertisement. Will you be adding this in future?

    thanks in advance.


  4. Hello Lee

    Looking a little deeper into the issue, looking at the router configurations, the router IDs of both R2 and R3 are indeed the same as both Lo interfaces are set to So according to BGP route selection process, if the router IDs are the same, then the router will prefer the route with the lowest neighbour IP address. So between R2 and R3, the lowest neighbour IP address is indeed, so R2 will be chosen as the path.

    So the following statement in the lesson has to be revised:


    …because the Router ID is actually that of the loopback interface, but since those are the same, the neighbour IP address is used. The result is the same, but the lesson should clarify this. I will let @ReneMolenaar know about it…

    Thanks for your help!


  5. lee says:

    Thanks Laz for clarifying that for me and the prompt response.

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