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Forum Replies

  1. Hei Rene,
    Thanks for the lesson, in my working experience, i am stuck in a situation for 2 sites. i have the ebgp peering up, but i am receiving 0 prefix from my isp. The isp said when they show ip bgp nei adverticed route that are hundreds of routes advertised, they can receive our route. Any good debug command to troule should this? We have plain bgp config, the same config (different peering ip though) is working with other sites.

    One interesting thing is that when i ping the isp with mtu 1500 it does not work, but it works with 1496. After reading cisco doc

    ... Continue reading in our forum

  2. Hi Jie,

    It’s possible that the MTU is causing your issue. Your ISP might be sending BGP updates of 1500 bytes which are dropped on your end. Here’s the default TCP segment size that is used for BGP:

    R1#show ip bgp neighbors | include segment
    Maximum output segment queue size: 50
    Datagrams (max data segment is 1460 bytes):

    The segment size is 1460 bytes, add a TCP header (20 bytes) and IP header (20 bytes) and you have a 1500 byte packet. In other words, you should be able to send/receive up to 1500 bytes which is not possible at the moment.


    ... Continue reading in our forum

  3. Sravanthi,
    The neighbor relationship defines whether the neighbor is considered external or internal. If you form a neighbor relationship with a BGP router that has the same ASN as you, then it is internal. Since a neighbor relationship must be established before NLRI is exchanged, there is no conflict, since an iBGP neighbor is not subjected to the eBGP loop avoidance techniques you mention.

  4. OMG RENE! your FSM Diagram is so easy to understand.

    I bought this book called Routing TCP/IP, Volume II: CCIE Professional Development 2
    Great book but they have very complex descriptions on some things let me show you their chart lol… your chart below nocked it out of the ball park. don’t get me wrong that’s a great book but its hard as hex to understand and works better when paired with something like your website which can break it down in simple terms. I just had to laugh over the two diagrams though as yours was so easy to understand lol…


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  5. Hello Pinki

    It is possible to apply load balancing in BGP. BGP will not perform Equal Cost Multi-Path (ECMP) routing by default but it can be configured to do so. Specifically, you can use BGP multipath load sharing. You can see how to configure eBGP and iBGP to use more than one path in the following lesson:


    Additionally, it is possible for BGP to advertise multiple paths for the same prefix allowing traffic to take various paths to the destination. This is called BGP Additional Paths

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