Solutions for Internet Traffic Load Balancing?

by David Davis on October 3, 2007

Today in the Forum, we had a great question from robshaw about solutions for Internet Traffic Load Balancing. I shared my thoughts on this topic with Rob and have posted them below. I am wondering if anyone else has this same issue and can offer your experiences and the best solution for it? If so, please post in your response in the Forum.

Here is the original post entitled: Load Balancing over MPLS
Hi Guys,
our ISP are putting in redundant routers and links for us to make our network more resilient. To do this we will be receiving an extra router and they will failover using HSRP. I was wondering if we could use both routers and links though and load balance. We will have a 4mb leased line and a 2mb sdsl for backup. I want to use both when they are both working giving us 6mb, and failover if one fails. However My ISP told me the only way to do this is to split the network into 2 subnets, otherwise we will get Asymmetric routing problems? I guess this is true because they would need to totally re model there core?
Any ideas or feedback, it just seems a waste not to utilize these links!

My Response-
Great question. In fact, I was having this discussion with one of my admins yesterday.  I think this topic should really be called “Internet Traffic Load Balancing” because  regardless of what protocol you are using, we all have the same issue….

At my company, we have a 6MB multilink PPP Internet and a 4MB wireless. We had them configured using BGP best path full routing. It worked well but one of the providers was always the best route so it was primarily used. Still, there was traffic on both. Despite our attempts at using BGP metrics to influence the traffic and allow it to be more evenly distributed, still, one provider always got most of the traffic. Later, I put in an ACL to force outbound path selection to be even. That tendedency to force asymmetric routing which periodically caused some issues. Recently, we changed the backup wireless to only provide a default route instead of full BGP routing. Now we are only using it as a backup route. I don’t like this too much because, like you are concerned about, it seems like a waste of bandwidth.

There are a couple of options here-
1) if both links are from the same provider (mine are not) then, if the provider offers it, you should be able to run a routing protocol like EIGRP on both links
and use its built-in load balancing options

2) I am looking into Cisco’s optimized edge routing (OER) to see if it could solve this for us
3) I saw an ad for a device that advertises this at – and I will look into that some more.
4) If you have some traffic that you could force over that link, then you might be able to use it, like say, you had a data sync stream to your DR site, you
could create a rule or router it over that directly.

Still, I am searching for the ideal solution. Anyone else have this issue or might have the ideal solution for us? If so, please respond to this post at: Forum: Load balancing over MPLS

{ 1 comment… read it below or add one }

Jonathan Villiard 04.10.10 at 2:15 pm

Great post Mr. Davis, thanks!

Elfiq Networks ( provides great Link Load Balancer products.
The product line enables organizations manage multiple concurrent Internet Service Providers and private WAN links to balance the traffic load to meet their bandwidth needs.

Please note that I am a member of the Elfiq Team.

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