Routers using Split Horizon

triplebenctriplebenc Member Posts: 28 ■□□□□□□□□□
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.



  • kplabkplab Member Posts: 101
    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:
    KPLAB - Free CCNA, CCNP, and Network+ Study Guides
  • EdTheLadEdTheLad Member Posts: 2,111 ■■■■□□□□□□
    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 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.
    Networking, sometimes i love it, mostly i hate it.Its all about the $$$$
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