HSRP CEF Load Balance Help please

pharvey · ‎09-25-2002

Any one give me some pointers please, HSRP Load Balance etc.

I have 2x 7206 with I/O FE and PA-FE TX, 2x back-to-back 7609 R-S-I Switches (OSPF)

2x 5505 Layer 2 Switches.

Take the 2x 5505's connect them FE back-to-back, and FE uplink both 5505's to the

7206's. Create a flat network with one default route out from the 5505's.

Take the 7206's and FE uplink them to the seperate 2x 7609 switches and a FE

back-to-back link, run a single group HSRP on the 7206's tracking the FE uplinks to

the 7609's.

Run OSPF and CEF on the 7206's.

Will the following work;

Traffic sent to the active router (7206), then be load shared by CEF (outbound

interface of 7206) across the FE uplink to the 7609, and across the back-to-back

between the 2x 7206's and onwards via the other FE uplink to the 7609.

Return traffic via the 7609's Load shared by CEF again???? (configured on the 7609)

steve.barlow · ‎09-25-2002

Look into using MHSRP on the 7206s (one 7206 active from group 1 and the other 7206 active for group 2) so that traffic can be split going to the 7206s from the 5505s. This assumes that the 5505 that connects to the 7206 will be STP root for the vlan that is HSRP active for that 7206, for optimal traffic flow. Then load balancing via CEF isn't required and there are fewer hops for the traffic to take. Eg traffic on 5505-a hits the 7206a, who then forwards it to 7609-a - or 5505b then 7206b then 7609b. Really it depends on your layer 2/STP design to know if it optimizes traffic flow (worst case traffic crosses both switches, but not both routers). Without MHSRP the traffic flow for every other packet or destination, depending on how cef is set up to load balance, is 5505 (possibly both switches are used as it crosses the link between switches), 7206, then the other 7206 and then 7609. More hops to cross.

If the above option doesn't appeal to you - Use the maximum-paths command under OSPF to allow more than one path to the routing table. OSPF allows only equal cost load balancing. Therefore you will have to play with metrics to get the 7206s to load balance.

Hope it helps.

Steve