D-Link DES-3326SR, User Manual

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DES-3326SR Layer 3 Fast Ethernet Switch User’s Guide
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Routing Protocols
Routing Information Protocol (RIP)
The Routing Information Protocol is a distance-vector routing
protocol. There are two types of network devices running RIP –
active and passive. Active devices advertise their routes to
others through RIP messages, while passive devices listen to
these messages. Both active and passive routers update their
routing tables based upon RIP messages that active routers
exchange. Only routers can run RIP in the active mode.
Every 30 seconds, a router running RIP broadcasts a routing
update containing a set of pairs of network addresses and a
distance (represented by the number of hops or routers
between the advertising router and the remote network). So,
the vector is the network address and the distance is measured
by the number of routers between the local router and the
remote network.
RIP measures distance by an integer count of the number of
hops from one network to another. A router is one hop from a
directly connected network, two hops from a network that can
be reached through a router, etc. The more routers between a
source and a destination, the greater the RIP distance (or hop
count).
There are a few rules to the routing table update process that
help to improve performance and stability. A router will not
replace a route with a newly learned one if the new route has
the same hop count (sometimes referred to as ‘cost’). So
learned routes are retained until a new route with a lower hop
count is learned.
When learned routes are entered into the routing table, a timer
is started. This timer is restarted every time this route is