Count To Infinity Problem

Why
The count to infinity problem is important because it has the potential to make our networks really slow and cause us to lose packets

What


The count to infinity problem occurs when we are using the distance vector algorithm and routers are passing outdated information to each other.

If node z advertises to y that it can reach x with a cost of 5 and then the link cost from x to y changes to 60, y will try to route towards x through z and advertise the cost of 6 to z. Because of this, we bounce back and forth 44 times until finally z realizes that its path of cost 50 is the best one

Poisoned Reverse
Poisoning the reverse path solves this particular instance of the count to infinity problem as shown above

When we are advertising our distance vector to our neighbors, we must make sure that if we are routing to a destination x through a neighbor y, then we advertise to the neighbor y that our distance to x is infinity so that the neighbor will never try to route through us to get to the destination.

However, this tactic does not solve the general count to infinity problem. If we have three nodes in an infinite loop, poisoning the reverse will not work.