DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
122 Switch Management and Operating Concepts
RIP can also be slow to converge (to remove inconsistent,
unreachable or looped routes from the routing table) because
RIP messages propagate relatively slowly through a network.
Slow convergence can be solved by using split horizon update,
where a router does not propagate information about a route
back to the interface on which it was received. This reduces
the probability of forming transient routing loops.
Hold down can be used to force a router to ignore new route
updates for a period of time (usually 60 seconds) after a new
route update has been received. This allows all routers on the
network to receive the message.
A router can ‘poison reverse’ a route by adding an infinite (16)
hop count to a route’s advertisement. This is usually used in
conjunction with triggered updates, which force a router to
send an immediate broadcast when an update of an
unreachable network is received.
RIP Version 1 Message Format
There are two types of RIP messages: routing information
messages and information requests. The same format is used
by both types.
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