How does RIP routing protocol work ?

Nowadays in WAN technologies, we use different types of routing protocols to find out the best route to the destination network like EIGRP, OSPF, BGP, IS-IS, and RIP. Every protocol has it’s own unique functionality and usability as well as advantages and disadvantages. For example, Most of ISPs use BGP routing protocol to maintain their large network. But to maintain very small network, it will be very difficult to configure and use BGP routing protocol. Generally people use RIP routing protocol to maintain small network which has limited nodes in WAN.

Lets discuss about the RIP routing protocol, why RIP is being used only for small network and not for large network ? How does it work ? How to configure RIP ? etc.

RIP Routing protocol :-

RIP stands for Routing Information Protocol. RIP is a dynamic-distance vector routing protocol based around the Berkely BDS application routed and was developed for smaller IP based networks. Rip is very slow protocol because of it’s slow convergence.

* How does it work and why It is use for small network ?

FIND BEST ROUTE :-

RIP uses UDP port no 250. RIP metric is hop count for find best route. RIP calculate the best route base on hop count. Means how many router I have jumped to reach my destination network. Rip cannot handle more than 15 hops. More than 15 hops away is considered unreachable by RIP. This is used by to prevent routing loops. Rip use bellman ford algorithm for find best route to reached destination network.

SEND UPDATE FOR OTHER NETWORK :-

Rip is a classful routing protocol. Rip do not include the subnet mask with route advertisement. Rip update it’s routing table every 30 seconds. It’s call a periodic update. Means in rip every 30 second every router send own routing table to it’s neighbor.

LOOP AVOIDANCE IN RIP :-

SPLIT HORIZON:-
A router never sends information about a route back in same direction which is
original information came. Means when any one router A is send update to router B about any failure network that time router B does not send any update for same network to router A in same direction.

ROUTE POISONING :-
Router consider route advertised with an infinitive metric to have failed ( metric=16)

POISON REVERSE :-
Poison reverse overwrite split horizon.

HOLD DOWN TIMERS :-
After hearing a poison route start a hold down time for that route until the timer expires. Do not believe any other routing information about the failed route. When originally advertise working routes which is advertise before filed route it can be believed before hold down time expire.
Hold down time = 180 second.

TRIGGERED UPDATE :-
When any route failed in network ,do not wait for the next periodic update instead send an immediate update listing the poison route.

COUNTING TO INFINITY
Maximum count 15 hope after it will not reachable.

INVALID TIMER :-
If router does not get any right information about failed route it is wait till invalid timer. After router advertise that network goes down.
Invalid timer = 180 second
Router flush timer = 240 second

How to configure RIP ?

Basic RIP configuration on CISCO router

Router> enable
Router# configure terminal
Router(config-if )# interface Ethernet 0
Router(config-if )# ip add 192.168.1.1 255.255.255.0
Router(config-if )# no shutdown
Router(config-if )# interface serial 0/1
Router(config-if )# ip add 110.10.1.1 255.255.255.252
Router(config-if )# no shutdown
Router(config-if )# router rip
Router(config-router )# network 192.168.1.0
Router(config-router )# network 110.10.1.0
Router(config-router )# exit
Router(config )# exit
Router#
Router#show running-config
Router#show ip route
Router#show ip protocols