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New Member

load balancing

topology

city1.......city2........city3

7200------3600-------7204

..|. . ... .... . . . . . . .|

7200-----------------7204

city1......................city3

Three campus network connect through T1s. Advice on loadbalancing traffic between city1 and city3. Routers are cisco 7200s and a 3600. Static routes are currently in place.

4 REPLIES

Re: load balancing

Hi,

Its unable to get the clear picture of your topology. Please paste the topology in a Word DOC or a small PPT using some icons so that it can get clear to us.

regards

-amit singh

New Member

Re: load balancing

Thanks for your reply.

Hall of Fame Super Silver

Re: load balancing

If I understand your description correctly what you have is a classic triangle connected by T1 point to point (equal cost paths). The classic solution if to route each city to its neighbor directly and perhaps to use the indirect path as a failover mechanism in case of failure of the direct connection.

What you indicate you want is to load share between city 1 and city 3 between the direct connection and the indirect connection. You do not indicate whether you need the same capability for city 2.

I assume that you currently have a static route at city 1 identifying the network(s) at city 3 with the route pointed at the T1 direct connection. An easy implementation would be to add a static route for the city 3 network(s) pointing to the city 2 link as a path. The router would then have 2 eaual cost paths and would load balance. This is simple and it would work, but one of the downsides of this implementation is that if there were a failure of the link between city 2 and city 3 the route at city 1 would continue to send some traffic for city 3 to city 2 but city 2 would not be able to forward it.

The solution to the problem mentioned above would be to run a dynamic routing protocol. The primary advantage of the dynamic routing protocol is that it becomes aware of changes in the remote parts of the network and makes appropriate adjustments. If you want to load balance this with a dynamic routing protocol using EIGRP would be the optimum solution because EIGRP is the only dynamic routing protocol that supports load balancing over unequal cost paths.

One other solution to consider might be the use of Policy Based Routing to achieve your purpose by directing certain types of traffic over the link through city 2. You would continnue to use the static routes that currently work for you which send traffic over the direct connection. You would identify certain types of traffic to send over the alternate path (you might choose certain protocols like FTP, or telnet, or anything else that makes sense in your environment, or you might choose certain source addresses or destination addresses) and configure PBR to send that traffic over the indirect link.

HTH

Rick

New Member

Re: load balancing

you are assuming correctly the load balancing between Cities 1 and 3 is the goal. I thought EIGRP would be solution, but GLBP was suggested. I don't know much about GLBP, so I posted here to get other people's ideals.

What is an application that GLBP would be suited for?

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