Objectives After completing this chapter you will be able to: Describe the Routing Information Protocol (RIP version 1 and RIP version 2) Describe Routing Loops, Split Horizons and Poison Reverse Outline the advantages and disadvantages of RIP

Characteristics of RIP RIP is a very simple protocol of the distance vector family. RIP was documented in RFC-1058 in June RIP messages can be broadly classified into two types: Routing information messages and messages used to request information. RIP uses a very simple metric - the hop count. RIP packets are carried over User Data Protocol (UDP) and IP. The RIP processes uses UDP port number 520. RIP updates are normally sent every 30 seconds by default. Every entry has a timer (180 seconds by default) associated with it and on expiry the distance for that entry is set to infinity.

Routing Table From Ericsson Colorado Router

RIP Version 1 Message Format Command(1) Version (1) Must be zero (2) Address family identifier (2) IP address (4) Must be zero (4) Metric (4) request 2 - Response 3 - Traceon 4 - Traceoff 5 - Reserved Address family identifier = 2 (IP) IP headerUDP Port=520

The RIP Protocol RIP Request ………………… …………………. RIP Response (Max 25 entries) Valid Class A, B or C? Net number =/ 127 or 0 Host number =/ broadcast Metric >/ 16 Metric = Metric+1 Update Routing table

RIP Neighbours RIP behaves promiscuously Ethernet RIP neighbours are defined Broadcast NetworksNBMA Networks ATM

RIP Version 2 Message Format Command(1) Version (1) Routing domain (2) Route tag (2) Address family identifier (2) IP address (4) Subnet mask (4) Next hop (4) Metric (4)

Slow Convergence AB CD NetworkHops A B C D NetworkHops A B C D Network Hops A B C D

Routing Loops AB D E C

Split Horizons AB D E C

Advantages of RIP RIP automatically creates and maintains a network of routes. Since RIP uses a single metric it is very easy to configure.

Disadvantages of RIP The diameter of the internetwork is limited to 15 router hops. Network administrators cannot take into account such factors as bandwidth or delay when configuring their routing systems using RIP. Each routing entry is updated every 30 seconds or so, regardless whether there has been a change in the network topology or not.