RIP( Routing Information Protocol)

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RIP is a standardized Distance Vector protocol, designed for use on smaller networks. RIP was one of the first true Distance Vector routing protocols, and is supported on a wide variety of systems.

RIP uses the Bellman-Ford Distance Vector algorithm to determine the best “path” to a particular destination.

RIP routes have an administrative distance of 120.

RIP sends out periodic routing updates (every 30 seconds)

RIP has a maximum hopcount of 15 hops.

RIP sends out the full routing table every periodic update.

RIP uses a form of distance as its metric (in this case, hopcount)

RIP has a maximum hopcount of 15 hops.Any network that is 16 hops away or more is considered unreachable to RIP, thus the maximum diameter of the network is 15 hops. A metric of 16 hops
in RIP is considered a poison route or infinity metric.

RIP Versions
RIP has two versions, Version 1 (RIPv1) and Version 2 (RIPv2).

RIPv1 (RFC 1058) is classful, and thus does not include the subnet mask with its routing table updates. Because of this, RIPv1 does not support Variable Length Subnet Masks (VLSMs). When using RIPv1, networks must be contiguous, and subnets of a major network must be configured with identical subnet masks. Otherwise, route table inconsistencies (or worse) will occur.

RIPv1 sends updates as broadcasts to address 255.255.255.255.

RIPv2 (RFC 2543) is classless, and thus does include the subnet mask with its routing table updates. RIPv2 fully supports VLSMs, allowing discontiguous networks and varying subnet masks to exist.

  • Routing updates are sent via multicast, using address 224.0.0.9.
  •  Encrypted authentication can be configured between RIPv2 routers
  •  Route tagging is supported

RIPv2 can interoperate with RIPv1. By default:

• RIPv1 routers will sent only Version 1 packets
• RIPv1 routers will receive both Version 1 and 2 updates
• RIPv2 routers will both send and receive only Version 2 updates

We can control the version of RIP a particular interface will “send” or “receive.” Unless RIPv2 is manually specified, a Cisco will default to RIPv1 when configuring RIP.

rip

Routing protocol configuration occurs in Global Configuration mode. On Router A, to configure RIP, we would type:

Router(config)# router rip
Router(config-router)# network 192.168.1.0
Router(config-router)# network 192.168.2.0

The  command, router rip, enables the RIP process.The network statements tell RIP which networks you wish to advertise to other RIP routers. We simply list the networks that are directly connected to our router. Notice that we specify the networks at their classful boundaries, and we do not specify a subnet mask.

To configure Router B:
Router(config)# router rip
Router(config-router)# network 192.168.2.0
Router(config-router)# network 192.168.3.0

The routing table on Router A will look like:

Router#show 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    192.168.1.0/24 is directly connected, FastEthernet0/0
C    192.168.2.0/24 is directly connected, Serial0/0/0
R    192.168.3.0/24 [120/1] via 192.168.2.2, 00:00:16, Serial0/0/0
Router#

The routing table on Router B will look like:

Router#show 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

R    192.168.1.0/24 [120/1] via 192.168.2.1, 00:00:03, Serial0/0/0
C    192.168.2.0/24 is directly connected, Serial0/0/0
C    192.168.3.0/24 is directly connected, FastEthernet0/0
Router#

 

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