Rip Version 1 Message Format - D-Link DGS-3324SR User Manual

D-Link DGS-3324SR Layer 3 Stackable Gigabit Ethernet Switch
RIP does not have an explicit method to detect routing loops. Many RIP implementations include an
authorization mechanism (a password) to prevent a router from learning erroneous routes from unauthorized
routers.
To maximize stability, the hop count RIP uses to measure distance must have a low maximum value. Infinity
(that is, the network is unreachable) is defined as 16 hops. In other words, if a network is more than 16 routers
from the source, the local router will consider the network unreachable.
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. Both types use
the same format.
The COMMAND field specifies an operation according the following table:
95