RIP – Routing Information Protocol Syeda Momina Tabish MIT - 7

Outline Introduction History Version RIP v1 RIP v2 RIPng Functioning

RIP – Introduction One of Interior gateway protocol (IGP) routing protocols on internal networks. 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. Its made obsolete by OSPF and IS-IS. Also sometimes called Rest in Pieces.

RIP – Introduction A simple intradomain protocol Straightforward implementation of Distance Vector Routing Each router advertises its distance vector every 30 seconds (or whenever its routing table changes) to all of its neighbors RIP always uses 1 as link metric Maximum hop count is 15, with “16” equal to “  ” Routes are timeout (set to 16) after 3 minutes if they are not updated

RIP – History Late 1960s : Distance Vector protocols were used in the ARPANET Mid-1970s: XNS (Xerox Network system) routing protocol is the precursor of RIP in IP (and Novell’s IPX RIP and Apple’s routing protocol) 1982Release of routed for BSD Unix 1988RIPv1 (RFC 1058) - classful routing 1993RIPv2 (RFC 1388) - adds subnet masks with each route entry - allows classless routing 1998Current version of RIPv2 (RFC 2453)

RIP – Message Format Two Message Types Request (sent by devices after initialization to request a unicast copy of a neighbor’s routing table Response (sent by RIP speaking devices by broadcasting every 30 seconds to IP ) Send via UDP/520 up to 25 routes per packet that include IP network, metric, but no subnet mask

RIP – Normal Operation For every active RIP interface Announce known RIP routes out RIP enabled interfaces every 30s Process received RIP annoucements by placing routes in routing table if better than existing route and add 1 to the hop count Do not announce things learned on an interface out the same interface (split horizon) Only announce if reachable with hop count <- 15

RIP Timers Router rip timers basic update invalid hold down flush Update 30s (when to broadcast response) Invalid 180s (when haven’t heard annoucements for 180s, do not use) Holddown 180s (when neighbor increases metric for a network, do not accept immediately Flush 240s (after invalid timer expires, mark as unreachable metric 16 until time to flush)

RIP v1 RIPv1, defined in RFC 1058 Uses classful routing Routing updates do not carry subnet information Lacking support for variable length subnet masks No Support for Router Authentication

RIPv1 Packet Format One RIP message can have up to 25 route entries 1: request 2: response 2: for IP 0…0: request full rou- ting table Address of destination Cost (measured in hops) 1: RIPv1

RIP v2 Developed in 1994 Included the ability to carry subnet information, thus supporting Classless Inter-Domain Routing (CIDR) 15 hop count limit remained. Rudimentary plain text authentication was added to secure routing updates; later, MD5 authentication was defined in RFC RIPv2 is specified in RFC 2453

RIPv2 Packet Format One RIP message can have up to 25 route entries 1: request 2: response 2: for IP 0…0: request full rou- ting table Address of destination Cost (measured in hops) 2: RIPv2

RIP Security Issue: Sending bogus routing updates to a router RIPv1: No protection RIPv2: Simple authentication scheme 2: plaintext password

RIP Problems RIP takes a long time to stabilize Even for a small network, it takes several minutes until the routing tables have settled after a change RIP has all the problems of distance vector algorithms, e.g., count-to-Infinity  RIP uses split horizon to avoid count-to-infinity The maximum path in RIP is 15 hops

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