Routing Information Protocol
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This article is chiefly about the Routing Information Protocol for IPv4 and IPv6.
The Routing Information Protocol (RIP) is one of the most commonly used Interior Gateway Protocol (IGP) routing protocols on internal networks (and to a lesser extent, the Internet), which helps routers dynamically adapt to changes of network connections by communicating information about which networks each router can reach and how far away those networks are. Although RIP is still actively used, it is generally considered to have been obsoleted by routing protocols such as OSPF and EIGRP.
RIP was first developed in 1969 as part of ARPANET, and used the Bellman-Ford algorithm. RIP is a distance-vector routing protocol which employs hop count as a routing metric. The maximum number of hops allowed with RIP is 15. Each RIP router transmits full updates every 30 seconds by default, generating large amounts of network traffic in lower bandwidth networks. It runs above the network layer of the Internet protocol suite, using UDP port 520 to carry its data. A mechanism called split horizon with limited poison reverse is used to avoid routing loops. Routers of some brands also use a holddown mechanism known as heuristics, whose usefulness is arguable and is not a part of the standard protocol.
In many current networking environments RIP would not be the first choice of Routing as its convergence times and scalability are poor compared to OSPF or IS-IS, and the hop limit severely limits the size of network it can be used in. On the other hand, it is easier to configure.
Versions
There are three versions of RIP, RIPv1, RIPv2, and RIPng.
RIPv1, defined in RFC 1058, uses classful routing. The routing updates do not carry subnet information, lacking support for variable length subnet masks. This limitation makes it impossible to have different-sized subnets inside of the same network class. In other words, all subnets in a network class must be the same size. There is also no support for router authentication, making RIPv1 slightly vulnerable to various attacks.
Due to the above deficiencies of RIPv1, RIPv2 was developed in 1994 and included the ability to carry subnet information, thus supporting Classless Inter-Domain Routing. However to maintain backwards compatibility the 15 hop count limit remained. Rudimentary plain text authentication was added to secure routing updates, later MD5 authentication was defined in RFC 2082.
RIPv2 is specified in RFC 2453 or STD 56.
RIPng, defined in RFC 2080, is an extention of the original protocols supporting IPv6
See also
fr:Routing information protocol nl:Routing Information Protocol (IP). pl:Routing Information Protocol