Intel 480T, User Manual

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C H A P T E R 1 1 RIP and OSPF
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• Support for load balancing to multiple routers based on the actual
cost of the link
• Support for hierarchical topologies where the network is divided
into areas
The details of RIP and OSPF are explained later in this chapter.
Overview of RIP
RIP is an Interior Gateway Protocol (IGP) first used in computer
routing in the Advanced Research Projects Agency Network
(ARPAnet) as early as 1969. It is primarily intended for use in
homogeneous networks of moderate size.
To determine the best path to a distant network, a router using RIP
always selects the path that has the least number of hops. Each
router that data must traverse is considered to be one hop.
Routing Table
The routing table in a router using RIP contains an entry for every
known destination network. Each routing table entry contains the
following information:
• IP address of the destination network
• Metric (hop count) to the destination network
• IP address of the next router
• Timer that tracks the amount of time since the entry was last
updated
The router exchanges an update message with each neighbor every
30 seconds (default value), or if there is a change to the overall
routed topology (also called
triggered updates ). If a router does not
receive an update message from its neighbor within the route
timeout period (180 seconds by default), the router assumes the
connection between it and its neighbor is no longer available.