Hi, [This message is quite long.]
I am trying to accomplish a routing configuration with equal cost load balancing that is breaking my mind. The topology can be viewed here: http://i9.tinypic.com/6c4m1aw.jpg Some facts: - The routing protocol is EIGRP - The two WAN links are both 64Mbps - "wan1" and "wan2" have the same view of the WAN routes - No weird and/or wonderful routing protocol knobs have been turned - The Etherchannel between "core1" and "core2" is layer 2 (dot1q) trunk - All other links shown are layer 3 ("no switchport") - All switches depicted are Cat6500s. WAN head-end routers are 7200-G1s and the branch office WAN routers are 2800s. At each distribution switch ("dist1" and "dist2"), I need to be able to load balance traffic out to the WAN. At this stage I'm only concerned with outbound (LAN to WAN) load balancing. This is the only key requirement - effective use of both (expensive) WAN links is my goal. There is no requirement to do traffic load balancing in other areas of the network. Irrespective of the source of the traffic destined for the WAN, it should be load balanced between the two WAN routers. This means traffic could be sourced from "MAN office A" or "B" or "C" or the "servers" cloud or from any of a number of other sites in the MAN. This means I may need to send traffic arriving at the distribution switches back out the interface it came in on. I suppose this means I need to do something with VLANs, or tunneling, or some other feature I'm not familiar with. In other words, I need to form routing adjacencies over interfaces other than the physical interfaces. My first attempt at a design was to change the links between the core and distribution from L3 to L2 trunks and then: 1. Create 4 "dedicated", "point to point" VLANs (core1/dist1, core1/dist2, core2/dist1 and core2/dist2) and then form EIGRP adjacencies over SVIs. Permit each VLAN to traverse the 4 respective dot1q trunks. 2. Create a new VLAN and allow it to exist in the core and distribution layers. Configure L3 SVIs for this VLAN on the two distribution switches and place the WAN router LAN-side interfaces in this VLAN as access ports. This allows "dist1" and "dist2" and "wan1" and "wan2" to be L2 adjacent. Routing adjacencies can be formed and each distribution switch will see two equal cost paths to WAN destinations (via the two WAN routers). The problem is that "dist1" and "dist2" will also learn these routes via their adjacencies with the core switches. At this point dead flies and sawdust exploded from my head and I figured there must be a better way. I want to end up with something manageable and I want to avoid having to muck around too much with EIGRP metrics, variance etc. This is an existing, production network and while I can make changes as required, re-designing the whole thing is not really viable. I've probably missed some key points, but that's my braindump for now. Chances are I'll look at this again tomorrow and it'll become obvious but in the meantime (and in case it doesn't), thanks for any insights! cheers, Dale _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
