Routing Information protocol
Routing Information Protocol (RIP) is a true distance-vector routing protocol. It sends the complete routing table out to all active interfaces every 30 seconds.RIP only uses hop count to determine the best way to remote network, but it has a maximum allowable hop count of 15,meaning that 16 is deemed unreachable.RIP works well in small networks, but it is inefficient on large networks with slow WAN links or on networks with a large number of routers installed.RIP version I uses only classful routing, which means that all devices in the network must use the same subnet mask.
RIP uses three different kinds of timers to regulate its performance:
Route update timer Sets the interval (typically 30 seconds) between periodic routing updates,in which the router sends a complete copy of its routing table out to all neighbors.
Route invalid timer Determines the length of time that must expire (90seconds)before a router determines that a route has become invalid. It will come to this conclusion if it hasn’t heard any updates about a particular route for that period. When that happens, the router will send out updates to all its neighbors letting them know that the route is invalid.
Route flush timer Sets the time between a route becoming invslid timer and its removal from the routing table (240 seconds).Before it is removed from the table, the router notifies its neighbors of that route’s impending doom. The value of the route invalid timer must be less than that of the route flush timer. This is to provide the router with enough time to tell its neighbors aout the invalid route before the routing table is updated.
Configuring RIP Routing
To configure RIP routing, ust turn on the protocol with the router rip command and tell the RIP routing protocol which networks to advertise. That’s it.As an example, let’s configure our four-router internetwork with RIP routing.
Configuring from terminal, memory, or network [terminal]?
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#interface fastEthernet 0/0
R1(config-if)#ip address 172.16.20.1 255.255.0.0
R1(config)#interface fastEthernet 0/1
R1(config-if)#ip address 172.17.20.1 255.255.0.0
%SYS-5-CONFIG_I: Configured from console by console
We have make this kind of configure in every router where we want to use RIP as a routing.(15 router max.)
Verifying the RIP Routing Tables
Each routing table should now have the routers directly connected routers as well as RIP-injected routers received from neighbor routers.
The router output below shows the contents of the 2621 A routing table.
R1#sh ip route
Codes: C – connected, S – static, I – IGRP, R – RIP, M – mobile, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area
N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2
E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP
i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area
* – candidate default, U – per-user static route, o – ODR
P – periodic downloaded static route
Gateway of last resort is not set
C 172.16.0.0/16 is directly connected, FastEthernet0/0
C 172.17.0.0/16 is directly connected, FastEthernet0/1
R 172.18.0.0/16 [120/1] via 172.17.20.2, 00:00:06, FastEthernet0/1
R 172.19.0.0/16 [120/2] via 172.17.20.2, 00:00:06, FastEthernet0/1
R means that the networks were added dynamically using the RIP routing protocol. The [120/3]is the administrative distance of the route (120)along with the number of hops to that remote networks(3).
—————- Thanks everyone