Routing Information Protocol (RIP)

Routing Information Protocol (RIP)

The Routing Information Protocol (RIP) is a simple, effective routing protocol for small- to medium-sized networks.

By using a routing protocol, routers automatically share route information, reducing the amount of administration required for maintaining routes between networks

Metric used by rip protocol was HOP count.

RIP is implemented on top of the User Datagram Protocol as its transport protocol. It is assigned the reserved port number 520.

Maximum hop counts for this protocol is 15 and maximum routers are 16.

Administrative distance of rip protocol is 120

Updates are broadcasted via 255.255.255.255

Each  update contains maximum of 25 routers

RIP Timers

RIP uses four 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 elapse (180 seconds) 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.

Holddown timer

This sets the amount of time during which routing information is suppressed. Routes will enter into the holddown state when an update packet is received that indicated the route is unreachable. This continues either until an update packet is received with a better metric or until the holddown timer expires. The default is 180 seconds.

Route flush timer

Sets the time between a route becoming invalid and its removal from the routing table (240 seconds). Before it's removed from the table, the router notifies its neighbors of that route's impending failure. The value of the route invalid timer must be less than that of the route flush timer. This gives the router enough time to tell its neighbors about the invalid route before the local routing table is updated.

Versions

IP RIP (Routing Information Protocol) comes in two different versions: 1 and 2. Version 1 is a distance vector protocol (RFC 1058) and Version 2 is a hybrid protocol (RFCs 1721 and 1722).

Routing Information Protocol Version 1 (RIPv1)

RIPv1 uses local broadcasts to share routing information. These updates are periodic in nature, occurring, by default, every 30 seconds. To prevent packets from circling around a loop forever, both versions of RIP solve counting to infinity by placing a hop count limit of 15 hops on packets. Any packet that reaches the sixteenth hop will be dropped. RIPv1 is a classful protocol. RIP supports up to six equal-cost paths to a single destination. Equal-cost path are the paths where the metric is same (Hop count).

Routing Information Protocol (RIPv2)

RIPv2 is a distance vector protocol with routing enhancements built into it, and it is based on RIPV1. Therefore, it is commonly called a hybrid protocol.

RIPv2 uses multicasts instead of broadcasts. RIPv2 supports triggered updates. when a change occurs, a RIPv2 router will immediately propagate its routing information to its connected neighbours. RIPv2 is a classless protocol and it supports variable-length subnet masking (VLSM).

Both RIPv1 and RIPv2 uses hop count as the metric.

Differences between RIPv1 and RIPv2

RIPv1

•Supports only classful routing (Does not support VLSM).

•No authentication.

•RIPv1 uses Broadcast.

RIPv2

•Supports classless routing (Supports VLSM). RIPv2 incorporates the addition of the network mask in the update to allow classless routing advertisements.

•Authentication is available.

•RIPv2 uses multi-cast instead of broadcast. multicast communication reduces the burden on the network devices that do not need to listen to RIP updates.

Useful command for RIP

Router(config)#router rip    Enables RIP as a routing protocol

Router(config-router)#network IP address

IP is the network number of the directly connected network you want to advertise.

Router(config)#no router rip  Turns off the RIP routing process

Router(config-router)#no network Ipaddress

Removes network IP from the RIP routing process.

Router(config-router)#version 2 RIP will now send and receive RIPv2 packets globally.

Router(config-router)#version 1 RIP will now send and receive RIPv1 packets only

Router(config-router)#no auto-summary  RIPv2 summarizes networks at the classful boundary. This command turns autosummarization off.

Router(config-router)#passive-interface s0/0/0  RIP updates will not be sent out this interface.

Router(config-router)#no ip split-horizon  Turns off split horizon (on by default).

Router(config-router)#ip split-horizon   Re-enables split horizon

Router(config-router)#timers basic 30 90 180 270 360

Changes timers in RIP: 30 = Update timer (in seconds) 90 = Invalid timer (in seconds) 180 = Hold-down timer (in seconds) 270 = Flush timer (in seconds) 360 = Sleep time (in milliseconds)

Router#debug ip rip  Displays all RIP activity in real time

Router#show ip rip database  Displays contents of the RIP database

Configuration

To configure any routing protocol, use the following three steps:

1. Enable IP routing if it is not already enabled (use the ip routing command). By default, IP

routing is already enabled, so this step is rarely required.

2. Switch to router configuration mode (use the router command, followed by the routing

protocol you want to configure).

3. Identify the networks that will participate in dynamic routing (use the network command,

followed by the address of a network to which the router is directly connected). This

identifies the interfaces that will share and process received routing updates.

4. Configure any additional parameters based on the routing protocol.

Routing Information Protocol (RIP) can be configured in a router using the following IOS commands. The "version 2" IOS command specifies that we are using RIPv2.

Router>enable

Router#configure terminal

Router(config)# router rip

Router(config-router)# version 2

Router(config-router)# network network_id