Dual-homing edge router

[jcarr]

I have a collapsed-core LAN with a pair of 6509's and a bunch of dual-homed 4506 access switches. The MSFC handles the routing between the various VLANs. I currently have a 3845 router connected to one of the 6509's and my WAN uplink to the rest of the world. I would like to dual-home the 3845 to both 6509's so that it would be resilient to a failure of either (like our dual-homed switches and servers).

What is the best way to do this? I've considered:

1) bridging the LAN interfaces on the 3845 and letting STP sort it out at layer 2.

2) running separate VLAN/subnets and letting EIGRP (our IGP) sort it out at layer 3.

3) using HSRP on both 3845 interfaces and the corresponding interfaces on the 6509s.

Any suggestions?

[Roberto Salazar]

1) bridging the LAN interfaces on the 3845 and letting STP sort it out at layer 2.

>> Is doable by bridging the lan interfaces and creating a BVI but your idea in step 2 would be the preferred way. for one thing, you will keep the STP simple, since the router will not participate in the STP.

2) running separate VLAN/subnets and letting EIGRP (our IGP) sort it out at layer 3.

>> Yes, this is preferred. Let the routing protocol sort out the load balancing and the redundancy.

3) using HSRP on both 3845 interfaces and the corresponding interfaces on the 6509s.

>> If you are referring to a single 3845 with multiple ethernet interfaces, you can't run HSRP on those interfaces since both interfaces will need to be in the same subnet. router will not allow you to configure two different interfaces in to be in the same subnet, overlapping ip.

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