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rbacct123
Beginner

Question about GLBP

I am just reading up on glbp and was wondering the following: How does it determine which router to route to? Does it check throughput, cpu, memory? Is it that sophisticated? Thanks for any input!

Thanks!

-J

1 REPLY 1
Steve Fuller
Engager

By default GLBP load balances on a round-robin basis i.e., each virtual forwarder in turn is included in the address resolution. There are other options (host-dependent and weighted), but nothing as sophisitcated as you've mentioned.

Whilst protocols can route based on load, this behaviour is typically not used as the traffic will tend to flip-flop between the active devices.

For instance, when the load on R1 goes up, the traffic moves to R2. As the load on R2 is now higher than R1, the traffic moves back to R1. The traffic on R1 goes up so moves to R2.... and so on.

The GLBP document at http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1839/products_feature_guide09186a00801541c8.html#80337 goes into some detail about the operation.

Regards