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Notable Replies

  1. Rene,

    That was a very detailed explanation. very straight forward. Thanks :slight_smile:



  2. clear. thx

  3. Hi Rene, i am confused to understanding this concept. please help.

    So what I could figure-out so far is :-

    "In a transit AS scenario, Enabling BGP sync made sense. because otherwise our ASBR router will advertise EBGP routes (learned from EBGP neighbor) to other internal routers as well and ultimately may become a transit AS for both EBGP neighbors which we don't want.

    So the rule said if we learn a route from IGP then only we should advertise it to other EBGP neighbor. that means we are only advertising network that we own.
    But now this rule is not needed in today's scenario. .....why ?(please help me in understanding)

  4. Hi Abhishek,

    BGP synchronization is an old rule in a time where not all routers within the AS were running IBGP. The problem here is not that we don't want to become a transit AS, but that R5 is learning a route that it can't reach (because R3 will drop the traffic).

    By enabling synchronization, we will not advertise this network to R5 anymore which might be a better idea compared to advertising something that is unreachable. Only once the route is known in the IGP, we know that R3 will be able to forward the traffic and only then we will advertise the route to R5.

    We don't use this anymore since nowadays, we run IBGP on all our routers if we have a transit AS, or even better...we use MPLS VPN where we only require BGP between the PE routers.

    Hope this helps!


  5. Awesome work Rene!!!

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