Routers using Split Horizon

triplebenc

Hey, I was curious if somebody could better explain "split horizon" I understand how router poisoning works, but cant seem to grasp how split horizon works, for example:

Router A - Ethernet fails
Router B - Sends an routing update

How split horizon solves this issue when Router A and B happen at the exact same time.

Thanks

kplab

Split horizon is a method to prevent routing loops. It states:

Never advertise a route out of the interface through which you learned it.

You can refer to this webpage for details:

http://en.wikipedia.org/wiki/Split_horizon

EdTheLad

Since i cant understand your example i'll create my own!

Split horizon is used so a router doesnt send an update on a link which originally learned the route.


RouterA

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RouterB

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RouterC

RouterA learns about RouterCs networks from RouterB,therefore it will not send RouterCs networks as updates towards RouterB.When Split Horizon poison reverse is enablbed ,RouterA will advertise RouterCs networks to RouterB with the route poisoned. .i.e in the case of Rip the hop count would equal 16 unreachable.