Define Split Horizon?

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The Router will not resend the same routing information from which interface it learnt that information is called Split-Horizon. The use of this concept is to avoid the routing loops in Network.

Explanation with Example:

LOOK AT SECOND IMAGE

Here in RA router the 30.0.0.0 information was received via RIP protocol on s0 interface but it wasn’t resend on same interface, it sending only 10.0.0.0 information. Here Split-horizon was enabled.

Lets see what happens when disabled

LOOK AT THIRD IMAGE

Now RA Router is resending the 30.0.0.0 information via s0 interface. It creates routing loops.

This is Split-horizon concept.