Unequal cost load balancing.

[ErrolDC]

Hi folks. Need some help with figuring out a solution to a routing issue. My company has a T-1 between another office 2 blocks away. We just recently setup some home-brew dsl to the same office using 4 dry pairs we got from the LEC; 9.2 Mb/s for $100 MRC.
I'm trying to determine what is the best way to balance traffic accross our T1 and our muxed dry pairs. Currently, we have an ISA server that provides firewall services for Site-A. It is also the default gw for the same site. At Site-B, the default gateway is a 1760. The same 1760 is directly connected to a 1760 at Site-A via T1 I mentioned above. Both sites are additionally connected via the 9.2Mb path I mentioned above via a pair of hard-to-find-and-get SDSL routers that support IP routing. Very soon, we will be reconfiguring our network to make the 1760 the default gateway because we are putting a PIX in the place of our ISA Server and the PIX is unable to be a router on a stick (there is already a PIX at Site-B). When I do this, I will need to balance the traffic between sites A and B over both paths. However, since one path is directly connected and the other is not, I'm not sure how to accomplish this in an intelligent way. The addiitonal complication of course is that the paths do not have the same bandwidth and delay. Thoughts any one?

Errol

 

[lgarner]

You could set up a GRE tunnel between the 1760's over the not-directly-connected path, then use EIGRP which supports unequal cost balancing.

 

[ErrolDC]

Thank you lgraner.
How would this work when the 1760 routers do not have any knowledge of an alternate path between the two sites?

 

[lgarner]

Once the tunnel is established, the routers appear as "connected" to one another. They can then share routing updates. Part of setting up the tunnel is to specify the address of the remote peer, so they will know about the path to each other.

Tunnel interfaces by default have a high delay factor. You'll want to adjust that to get them to prefer the tunnel over the slower direct line.