What is the purpose of the "poison reverse" update feature in routing protocols?

The "poison reverse" update feature in routing protocols is specifically designed to prevent routing loops. When a router receives an update about a route that it previously advertised, it will send an update back to the router that provided the information, indicating that the route is no longer valid by setting its metric to an infinite value. This effectively "poisons" the route and informs all other routers that the previously advertised route should not be used, thus breaking the potential for a loop to occur.

In situations where a route becomes invalid, such as when a link goes down, without poison reverse, there is a risk that routers might continue to route traffic using the outdated and incorrect information, which can lead to routing loops. By implementing poison reverse, routing protocols can ensure that routers are quickly informed about the invalid paths, thus maintaining a stable and loop-free routing environment.

The other options do not align with the primary purpose of poison reverse. Increasing bandwidth usage is not a goal of this feature; rather, it functions to enhance stability in the routing table. Sharing metrics among routers is a common function in routing but does not directly relate to the concept of preventing routing loops. Establishing static routes is a manual configuration process that does not involve the dynamic updates handled by poison