the routing information protocol (RIP) is the first protocol used in the internal gateway protocol IGP. RIP is a distributed routing protocol based on distance vector, and it is the standard protocol of the Internet. Its biggest advantage is its simple implementation and low overhead.

RIP(Routing Information Protocol) is a routing protocol based on distance vector algorithm, which uses hop count as the measurement standard.

working principle

(1) Route establishment

After running RIP, the router will first send a route update request, and the router that receives the request will send its own RIP route in response; After the network is stable, the router will send routing update information periodically.

(2) Calculation of distance vector

The unit of RIP metric is the number of hops, and its unit is 1, which means that the cost of each link is 1, regardless of the actual bandwidth, delay and other factors of the link, and RIP allows 15 hops at most.

RIP uses metrics to indicate the distance between it and all known destinations.

when a RIP update message arrives, the receiver router compares each item with its own RIP routing table, and corrects its own RIP routing table according to the distance vector routing algorithm.

(3) Timer

Periodic update timer: used to stimulate the update of RIP router routing table. Each RIP node has only one update timer, which is set to 3s. Every 3s, the router will broadcast its routing table information to its neighbors. The timer of each RIP router is independent of other routers in the network, so it is unlikely that they will broadcast at the same time.

timeout timer: used to determine whether a route is available. Each route has a timeout timer set to 18s s. When a route is activated or updated, the timer is initialized, and if no update about that route is received within 18s, the route is set as invalid.

Clear timer: used to determine whether to clear a route. Each route has a clearing timer set to 12s. When the router realizes that a route is invalid, it initializes a clearing timer, and if the update of this route is not received within 12s, it will be deleted from the routing table.

delay timer: a random delay timer, with a delay time of 1 ~ 5s, to avoid the broadcast storm caused by the trigger update.

(4) Loop

When the network fails, RIP network may generate a routing loop. The loop can be avoided by horizontal segmentation, toxicity inversion, trigger update, suppression time and other technologies.