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Multihome and BGP

Here's my scenario:

My company is running EBGP peering with ISP1 and ISP2. We have a /24 subnet from ISP1. ISP1 link is 15MB, ISP2 link is 6MB. My goals are:

  1. Try to load balance incoming traffic as much as possible but preferrably most should go through ISP1. I know ISP2 will advertise the more specific /24 route and ISP1 will advertise an aggregate route. How do I still achieve my goal?

  1. My number 2 goal is to load balance outgoing traffic but only receive default route from both ISP. Is this possible?

Reply to
navcole
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You have GOT to have ISP1 advertise the /24. If not all inbound traffic will go through ISP2 because the route is more specific. Secondly, if you're limited on resources and want minimal load balancing, get a default from ISP1 and partial routes from ISP2 and prepend the advertisement to ISP2 by 1 hop.

Hope this helps, Steve

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Reply to
www.networking-forum.com

BGP is *very* bad at load balancing. This has been discussed hundreds of times in this group, do a google search for "bgp load balancing".

To have any chance, you need ISP1 to advertise the /24 route as well. Otherwise, everything except traffic from ISP1's customers will arrive through ISP2.

Then you need to adjust your padding on the route to ISP2 until the traffic loads get close to what you want.

You definitely cannot balance your outgoing traffic if you only get default routes from both ISPs. You need both ISPs to send you specific routes, and then you need to adjust your settings to use more of the ISP1 routes than ISP2 routes.

Reply to
Barry Margolin

What type of topology do I run between the 2 edge router and the firewall? Can I have the firewall send a default route to an HSRP default gateway to one of the router and let an IGP take care of the rest?

Reply to
navcole

Run IBGP between the two edge routers, and have the firewall point to the HSRP virtual address as its default gateway.

Reply to
Barry Margolin

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