OSPF and Traceroute

[James Hoggard]

Hi,

Please find attached topology in packet tracer.

I have OSPF configured between all routers in area 0 all is working and i can ping from end to end.

However when a run a tracert from pc5 ( 192.168.20.10 ) it takes a different route each time i run the tracert is this some kind of load balancing it is doing?

Also when it goes via 10.3.3.2 router after that i would expect the next hop to be 10.4.4.2 not 10.2.2.2? can anyone explain why it is doing this?

[Bilal Nawaz]

Hello

The router is load balancing between two equal cost paths. I believe its on a per session basis.

[aacole]

OSPF will load balance in a situation like this, called equal cost multipath routing ECMP. Basically the paths have to have the same cost, dervied from the link speeds.

Probably what is occurring here is that the ICMP packet from PC5 gets to 10.4.4.2 via 10.3.3.2, but the router with the 10.4.4.2 interface simply sends the reply across the alternate path, as its an equal cost.

[Joseph W. Doherty]

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BTW, also keep in mind, Packet Tracer, isn't always faithful to real networks.