The RIP is one of the oldest distance-vector routing protocol which employs the hop counts as a routing metric. This protocol prevents routing loops by implementing a limit on a certain amounts of hops allowed in the path from source to destination.
Each (RIP) router maintains a routing table, which is a lost of all the destinations it knows how to reach along with the distance to that destination. Rip router sends its entire routing table to its closest neighbours every 30 seconds. (The neighbours are the other routers to which this router is connected directly).
RIPv1
The RIPv1 was the original specification of (RIP) that was then define in RFC 1058. It was then published in 1938 and uses classful routing. The periodic routing updates do not carry subnet information. This makes it impossible to have different sized subnets of the same networks class, all subnets must have the same size. There is no support for router authentication this making it vulnerable to any attacks.
RIPv2
Rip version 2 was developed in 1993 and last standardised in 1998, it was able to carry subnet information, supporting Classless Inter-Domain Routing (CIDR) to maintain backward compatibility, 15 is also the ho count limit for RIPv2. It is able to fully interoperate with the earlier specification if all must be zero protocol fields if RIPv1 messages are properly specified,it has a compatibility switch feature it allows fine-grained interoperability adjustments. To avoid any unnecessary load on host that do not participate in routing, Rip version 2 will multicasts the entire routing table to the adjacent roters at the address of 224.0.0.9. Authentication for (RIP)v2 was introduce in 1997.
RIPing
RIPing meaning RIP next generation it is an extention for RIPv2 for supporting IPv6. The main difference between RIpv2 and RIPing are IPv6 supports IPv6 networking and RIPv2 supports RIPv1 updates authentication while RIPing does not.
RIPv1 Operation
Rip defines two types of messages:
1. Requst message
2. Response message
Every time a RIP router comes online it sends a broadcast request message on all of its (RIP enabled interface, all who receives the request message responds back with a respond message containing there router table. The respond message is also sent when the update timer expires.
On receiving the Routing table, the router processes each entry of the routing table as per the following rules:
1. If there are no route entries matching the one received then the route entry is added to the routing table automatically, along with the information about the router from which it received the routing table.
2. If there are matching entries but the hop count metric is lower than the one already in its routing table, then the routing table is updated with the new route.
3. If there are matching entries but the hop count metric is higher than the one already in its routing table, then the routing entry is updated with hop count of 16 (infinite hop). The packets are still forwarded to the old route. A Holddown timer is started and all the updates for that from other routers are ignored. If after the Holddown timer expires and still the router is advertising with the same higher hop count then the value is updated into its routing table. Only after the timer expires, the updates from other routers are accepted for that route.
Timers
The routing information protocol uses timers as part of its operation
• Update timer
• Invalid timer
• Flush timer
• Holddown timer
• Update timer
Update timer
The Update timer controls the interval between two gratuitous Response message. By default the value is 30 seconds. The response message is then broadcast to all RIP enabled interface
The Update timer controls the interval between two gratuitous Response message. By default the value is 30 seconds. The response message is then broadcast to all RIP enabled interface
Invalid timer
The invalid timer tells you how long a routing entry can be in the routing table without being updated. It is also called expiration timer the value is 180 seconds by default. When the timer expires the hop counts will be set to 16 which will be signed the destination as unreachable
The invalid timer tells you how long a routing entry can be in the routing table without being updated. It is also called expiration timer the value is 180 seconds by default. When the timer expires the hop counts will be set to 16 which will be signed the destination as unreachable
Flush timer
The flush timer comtrols the time between the route is invalidated or unreachable and removal of entry in the routing table , the value is 240 seconds by default, it is 60 seconds longer the invalid timer. The timer must be set to a higher value than invalid timer.
Hold-down timer
The Hold-down timer is started per route entry, when the hop counts changes from lower to higher value this will allow the route to get stabilized when this happens no update will be done to the routing entry. The default timer is 180 seconds.
The Hold-down timer is started per route entry, when the hop counts changes from lower to higher value this will allow the route to get stabilized when this happens no update will be done to the routing entry. The default timer is 180 seconds.
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