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Alteon OS Application Guide
156
Chapter 9: Routing Information Protocol 42C4911, January 2007
Routing Updates
RIP sends routing-update messages at regular intervals and when the network topology
changes. Each router “advertises” routing information by sending a routing information update
every 30 seconds. If a router doesn’t receive an update from another router for 180 seconds,
those routes provided by that router are declared invalid. After another 120 seconds without
receiving an update for those routes, the routes are removed from the routing table and respec-
tive regular updates.
When a router receives a routing update that includes changes to an entry, it updates its routing
table to reflect the new route. The metric value for the path is increased by 1, and the sender is
indicated as the next hop. RIP routers maintain only the best route (the route with the lowest
metric value) to a destination.
For more information see The Configuration Menu, Routing Information Protocol Configura-
tion (/cfg/l3/rip) in the Alteon OS Command Reference.
RIPv1
RIP version 1 use broadcast User Datagram Protocol (UDP) data packets for the regular rout-
ing updates. The main disadvantage is that the routing updates do not carry subnet mask infor-
mation. Hence, the router cannot determine whether the route is a subnet route or a host route.
It is of limited usage after the introduction of RIPv2. For more information about
RIPv1 and RIPv2, refer to RFC 1058 and RFC 2453.
RIPv2
RIPv2 is the most popular and preferred configuration for most networks. RIPv2 expands the
amount of useful information carried in RIP messages and provides a measure of security. For
a detailed explanation of RIPv2, refer to RFC 1723 and RFC 2453.
RIPv2 improves efficiency by using multicast UDP (address 224.0.0.9) data packets for regu-
lar routing updates. Subnet mask information is provided in the routing updates. A security
option is added for authenticating routing updates, by using a shared password. Alteon OS sup-
ports using clear password for RIPv2.