How does ospf equal-cost load balancing work

[martin_lx1980]

   Router that runs ospf protocol have 3 equal-cost paths in my network. There is a special application that brings out large traffic from host A to host B every night. I find this traffic was always passed through the special path during 3 equal-cost paths. So I am confused that how Ospf equal-cost load balancing work.

   If 4 equal cost paths exist, When the ospf network is sync for the first time which path does router select for the first packet? Which factors will affect this seletion?

Thanks a lot

Martin

[Marwan ALshawi]

Hi Martin

The routing equal cost loadbalancing has two stages

First the RIB table which built from the routing table which is where you can see the routi g protocol install multiple exit interfaces for the same destination network

Once these interfaces installed the FIB tab,e will be built using CEF ad RIB cef will distribute the traffic or load balance  it in a per session "source - destination "  and that's why you see the traffic using only one exit interface

This can be change to be per packet load sharing but it has several disadvantages such as tcp out of sequence and high CPU utilization

You can do some more research and testing on this if you like to try it

Hope this help

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