User`s manual

becomes invalid if 180 seconds pass without that route being advertised again.
RIP has certain features that provide stability in rapidly changing network conditions.
Split horizon
When RIP enabled interfaces are initialized, they build a routing table based on their directly connected
interfaces. During the time it takes for this information to converge and the best route to be determined and
stabilized, routing loops can occur. These loops are created when one routing interface receives information that
includes itself as an intermediate hop to another destination.
For example,
Router Interface 2 has a route to Router A, broadcasts that to Router Interface 1, which broadcasts
back to Router Interface 2 a route to A, with Router Interface 2 as an intermediate hop.
Split horizon helps reduce bandwidth consumption and speeds up information distribution by advertising to an
interface only the routing information obtained from other interfaces. Router Interface 1 does not advertise the
routes it learned from Router Interface 2 back to Router Interface 2.
Poison reverse updates
Poison reverse updates prevent larger loops in a network by setting the metric (cost) of neighboring routers to
infinity, and therefore, unreachable.
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