RIP 225
■Cost—The cost for the router to reach the destination, which should be an integer
in the range of 0 to 16.
■Timer—The length of time from the last time that the routing entry was modified
until now. The timer is reset to 0 whenever a routing entry is modified.
■Route tag—The indication whether the route is generated by an interior routing
protocol or by an exterior routing protocol.
The process of RIP startup and operation is as follows:
1If RIP is enabled on a router for the first time, the router broadcasts or multicasts a
request packet to the adjacent routers. When they receive the request packet,
adjacent routers (on which RIP is also enabled) respond to the request by returning
response packets containing information about their local routing tables.
2After receiving the response packets, the router that sent the request modifies its own
routing table.
3RIP broadcasts its routing table to the adjacent routers every 30 seconds. The adjacent
routers maintain their own routing table after receiving the packets and elect an
optimal route. They then advertise the modification information to their adjacent
network to make the updated route globally available. RIP uses the timeout
mechanism to handle timed out routes to ensure the timeliness and validity of the
routes. With these mechanisms, RIP, an interior routing protocol, enables the router to
learn the routing information of the entire network.
RIP has become one of the most popular standards of transmitting router and host
routes. It can be used in most campus networks and regional networks that are
simple yet extensive. RIP is not recommended for larger and more complicated
networks.
RIP configuration is described in the following sections:
■Configuring RIP
■Troubleshooting RIP
Configuring RIP Only after RIP is enabled can other functional features be configured. But the
configuration of the interface-related functional features is not dependent on
whether RIP has been enabled.
After RIP is disabled, the interface-related features also become invalid.
The RIP configuration tasks are described in the following sections:
■Enabling RIP and Entering the RIP View
■Enabling RIP on a Specified Network
■Configuring Unicast RIP Messages
■Specifying the RIP Version
■Configuring RIP Timers
■Configuring RIP-1 Zero Field Check of the Interface Packet
■Specifying the Operating State of the Interface
■Disabling Host Route
■Enabling RIP-2 Route Aggregation
■Setting RIP-2 Packet Authentication
■Configuring Split Horizon