What is Routing Protocols RIP.

In global configuration mode enter router ? to see the available routing protocols.

Routing Protocol

   Router3>en
   Router3#conf t
   Enter configuration commands, one per line.  End with CNTL/Z.
   Router3(config)#router ?

     bgp -      Border Gateway Protocol (BGP)
     egp -      Exterior Gateway Protocol (EGP)
     eigrp -    Enhanced Interior Gateway Routing Protocol (EIGRP)
     igrp -     Interior Gateway Routing Protocol (IGRP)
     isis  -    ISO IS-IS
     iso-igrp - IGRP for OSI networks
     mobile -    Mobile routes
     odr   -    On Demand stub Routes
     ospf  -    Open Shortest Path First (OSPF)
     rip   -    Routing Information Protocol (RIP)
     static -   Static routes
 
Routing Information Protocol (RIP) 

The Routing Information Protocol (RIP) is a distance-vector protocol that uses hop count as its metric. RIP is widely used for routing traffic in the global Internet and is an interior gateway protocol (IGP), which means that it performs routing within a single autonomous system.  RIP only uses hop count to determine the best route to a remote network,  RIP has a maximum hop count of 15, 16 is deemed unreachable.  RIP works well in small inter-networks, but is inefficient for large networks.  RIP is susceptible to all the problems normally associated with distance vector routing protocols.  It is slow to converge and forces routers to learn network information only from neighbors.  RIP version 1 uses classfull routing (all devices in the network must use the same subnet mask because RIP version 1 doesn't send updates with subnet information).  RIP version 2 uses classless routing and does send subnet mask information with route updates.  RIP networks need the same hop count to load balance multiple links.

Routing Updates  

RIP sends its complete routing table out to all active interfaces at regular intervals (every 30 seconds) and when the network topology changes.  When a router receives a routing update that includes changes to an entry, it updates its routing table to reflect the new route.  The metric value for the path is increased by one, and the sender is indicated as the next hop.  RIP routers maintain only the best route (the route with the lowest metric value) to a destination.  After updating its routing table, the router immediately begins transmitting routing updates to inform other network routers of the change.  These updates are sent independently of the regularly scheduled updates that RIP routers send.

RIP Routing Metric 

RIP uses a single routing metric (hop count) to measure the distance between the source and a destination network.  Each hop in a path from source to destination is assigned a hop-count value, which is typically 1.  When a router receives a routing update that contains a new or changed destination-network entry, the router adds one to the metric value indicated in the update and enters the network in the routing table.  The IP address of the sender is used as the next hop.

RIP prevents routing loops from continuing indefinitely by implementing a limit on the number of hops allowed in a path from the source to a destination (15 hops).  If a router receives a routing update that contains a new or changed entry, and if increasing the metric value by one causes the metric to be infinity (that is, 16), the network destination is considered unreachable.

Stability Features  

To adjust for rapid network-topology changes, RIP specifies a number of stability features that are common to many routing protocols. RIP, for example, implements the split-horizon and hold-down mechanisms to prevent incorrect routing information from being propagated.  In addition, the RIP hop-count limit prevents routing loops from continuing indefinitely.

RIP Timers Route Update Timer - The routing-update timer clocks the interval between periodic routing updates.  It is usually set to 30 seconds.

Route Invalid Timer - The Route Invalid Timer determines the length of time (90 seconds) before a route is considered invalid.  If it doesn't receive an update for the route it sets the route as invalid and notifies its neighbors.

Route Flush Timer - The Route Flush Timer sets the time between when a route becomes invalid and its removal from the routing table (240 seconds).  Time must be longer than invalid timer so it can tell its neighbors about the route.

 

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Thanks a lot for reading
Neel Kamal