Solved: High reliablity and load sharing

michel_douglas · ‎04-01-2007

Hi All,

i have three routers A,B and C. router B and C are connected to router A,Router A is connected to my LAN. Router B and Router C both have links terminating on them.

can anybody help me with a solution where in i can have load balancing and auto failover configured on them?

Regard's

MIchel

Jon Marshall · ‎04-01-2007

Hi

It depends on whether the links that terminate on B & C are to the same destinations. If they are then Narayan's suggestion is the way to go.

If not you will need a connection between B & C to achieve any sort of load-balancing/redundancy. Assuming you connect B & C together and that you run EIGRP between your routers you could achieve limted failover and load balancing eg.

One of your destination subnets is 192.168.10.0/24 and this can be reached via router B. Router A will receive two paths to 192.168.10.0/24. But the preferred path will be A -> B, as opposed to A -> C -> B.

As long as the A -> C -> B path is seen as a feasible successor you can still load balance using the variance command in EIGRP which allows unequal cost load balancing across links.

As for failover, if router B dies, or router B's WAN interface dies then you have lost that subnet no matter what you do. But if router B's interface to router A dies you will still be able to reach the remote networks from A via C then B.

HTH

Jon

View solution in original post

royalblues · ‎04-01-2007

Michel,

Configure a routing protocol like EIGRP between router A, B & C.

If the links speeds are same, router A would have two routes for each destination learned from B & C and the traffic would be loadbalanced.

If you want one router to act as primary and other as purely backup, you can tune the metrics.

HTH, rate if it does

Narayan

Jon Marshall · ‎04-01-2007

Hi

It depends on whether the links that terminate on B & C are to the same destinations. If they are then Narayan's suggestion is the way to go.

If not you will need a connection between B & C to achieve any sort of load-balancing/redundancy. Assuming you connect B & C together and that you run EIGRP between your routers you could achieve limted failover and load balancing eg.

One of your destination subnets is 192.168.10.0/24 and this can be reached via router B. Router A will receive two paths to 192.168.10.0/24. But the preferred path will be A -> B, as opposed to A -> C -> B.

As long as the A -> C -> B path is seen as a feasible successor you can still load balance using the variance command in EIGRP which allows unequal cost load balancing across links.

As for failover, if router B dies, or router B's WAN interface dies then you have lost that subnet no matter what you do. But if router B's interface to router A dies you will still be able to reach the remote networks from A via C then B.

HTH

Jon

michel_douglas · ‎04-01-2007

Hey Guys,

Thanks for the prompt reply but one more query as per the client requirement we have to use two different routers for both the link the connectivity being A->B and the link terminating on B Router and D -> C and c and the link terminating on C. and the destination for both links is the same.

(NOte - connectivity between A-> B and D-> C is an Ethernet connectivity)

will the soultions be the same in this scenario?

ciscobuddy · ‎04-01-2007

hi michel,

can you please explain more about your network and your requirment.

Thanks