routing loops problem

Unanswered Question
Feb 12th, 2009

hi all,I want to know how the routing loops occur in the distance-vector routing protocols? please help me ,thank you

I have this problem too.
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Giuseppe Larosa Fri, 02/13/2009 - 03:34

Hello Wang,

actually distance vector routing protocols implement several features to try to avoid routing loops.

A routing loop for network A happens when two routers (or more) think each other to be the next hop to reach the destination.

counter measures include:

split horizon

count to infinity

poison reverse

triggered updates

Imagine three routers connected in a triangle each advertising their connected lan subnet.

If netA on RA fails in absence of safety measures a routing loop will form.

RA will simply stop to advertise netA.

RC will think that RB is the next-hop for netA with metric 2 hop counts

Hope to help



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