RIP (Routing Information Protocol) is a distant vector routing protocol. RIP algorithm has been in use since the early days of ARPAnet. Currently, there are 2 versions of RIP, which are known as Routing Information Protocol version 1 (RIPv1) and Routing Information Protocol version 2 (RIPv2). More information about RIPv1 can be found on (RFC1058) and more information about RIPv2 can be found on (RFC 1723). RIPv1 supports only classful routing and RIPv2 uses classless routing. This means RIPv2 support Variable length Subnet Mask (VLSM).
RIP is a UDP based protocol that uses port 520 for all communication. RIP was designed for small to medium sized networks. RIP uses hop count as a metric. RIP supports maximum 15 hops. The maximum size of RIPv1 or RIP2 packet is 512 octets. RIP has the administrative distance of 120.
Route update timer
Every 30 seconds, a Cisco router will send a RIP update out every interface that has a RIP network attached to it. Each update contains the entire routing table of the sending router. When another router on the network receives the update, it adds any new routes to its routing table or will replace a route if the update has a lower hop count for that route.
Route Invalid Timer
Route invalid timer is 180 seconds. If router doesn’t receive any update about a particular router for that period, then router will find out that this route has become invalid.
Route Flush Timer
Sets the time between a route becoming invalid and its removal from the routing table (240 seconds).
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