RIP - Routing Information Protocol

The Routing Information Protocol (RIP) is one of the oldest distance-vector routing protocols which employ the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from source to destination. It is characterized as an interior gateway protocol, and is typically used in small to medium-sized networks. Max hop count is 15. AD value of RIP is 120.

RIP has a 2 Version,

RIP Version 1 RIP Version 2
Classfull routing protocol By default Classfull but supports classless also
Broadcasts Update on 255.255.255.255 Multicasts update on 224.0.0.9
Doesnot support authentication Supports authentication

RIP - Timer

  • 1. Update : The update timer controls the interval between two gratuitous Response Messages. Default timer is 30 sec. The response message is broadcast to all its RIP enabled interface.
  • 2. Holddown : The hold-down timer is started per route entry, when the hop count is changing from lower value to higher value. This allows the route to get stabilized. During this time no update can be done to that routing entry.The default value of this timer is 180 seconds.
  • 3. Invalid : The invalid timer specifies how long a routing entry can be in the routing table without being updated. This is also called as expiration Timer. By default, the value is 180 seconds. After the timer expires the hop count of the routing entry will be set to 16, marking the destination as unreachable
  • 4. Flush : The flush timer controls the time between the route is invalidated or marked as unreachable and removal of entry from the routing table. By default the value is 240 seconds. This is 60 seconds longer than Invalid timer. So for 60 seconds the router will be advertising about this unreachable route to all its neighbours. This timer must be set to a higher value than the invalid time.

Split Horizon

It is the method of preventing routing loops in Distence Vector routing protocol by restricting the router to advertise back onto a interface from which it was received.
RIP Split Horizon

NOTE: Hopcount indicates that how far any advertised information can travel or multicasts within network or the life time of Packets. As sender sends packet with max hopcount value and within each hop it decreases everytime by 1.

Route Poision

If router does not have info about particular network ans it is sending metrix value of 16, then that process is called Route Poisioning i.e Router send update with metrix value 16.
RIP Split Horizon