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Notable Replies

  1. Hi Rene,

    In this statement here - "What if I wanted to send 80% of the outgoing traffic on the primary link and 20% down the backup link? That’s not going to happen here but with BGP it’s possible."

    How would you configure an 80/20 split for example using BGP (or any ratio..just as an example)?


  2. Hi Rob,

    Good question, there's not a really short answer to it :slight_smile: With routing protocols like RIP, OSPF or EIGRP we use default routes for outbound traffic so we really don't know anything about the destination. When we use BGP, it's possible that we learn about all possible destinations (entire Internet routing table) or a partial routing table.

    BGP uses a lot of different attributes (weight, local preference, metric, etc) that we can use to decide which path we use for certain destinations. You can use these for traffic engineering to send an X amount of traffic to one BGP neighbor and the rest to another neighbor.

    Another option is something called "bgp dmzlink-bw". This allows you to do load balancing based on the bandwidth.


  3. My company have two ISP connections but we only use 1 for all our traffic and the other was is for backup situation. We were planning to buy a netgear router (http://www.netgear.com.au/business/products/security/FVS336G.aspx#tab-features). There are two WAN port and it has load sharing capability. Are you saying that in the configuration we will not be able to set 80% to ISP 1 and 20% to ISP2 and it will be 50/50 distribution only? and if we do want to send 80% trafic through 1 ISP and 20% through another we don't have an other option but to buy beefy routers to run BGP. Moreover, I heard that bgp is more about controlling incoming traffic flow from multiple ISPs to your network (you may be running multiple webserver in your network)rather than outgoing traffic from your network?

  4. Hi Kulwant,

    It depends on the router, maybe it's possible. You will have two default routers so most routers will just do "per packet" or "per destination" load balancing and you will have about 50/50 load balancing. Some routers might check the current load of the interfaces and then select the outgoing interface...

    BGP is typically used to advertise your public IP space. You can also use it for outbound load balancing if you receive more than just the default route from your ISPs. Also, by using AS path prepending and/or MED we can influence how traffic enters our network.


  5. Hi Rene! You write excellent articles about networking!

    I have just started learn BGP, and there is question that bother me. I attached screenshot from some site, and as you can this is wireshark capture. Router sends bgp packets "OPEN Message, KEEPALIVE Message" and "KEEPALIVE Message, KEEPALIVE Message". Meaning there are two messages in one packets. Why BGP process do that? I test that and in very beginning of bgp session initiation routers send "update message, update message" (meaning there are two update messages in one packet) to each other.

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