Qtech QSW-3900-24-SFP-AC [85/245] Rip configuration

QTECH Software Configuration Manual

7-84

Chapter 7 RIP Configuration

7.1 Brief introduction of RIP

RIP is short for Routing Information Protocol. It is a protocol based on D-V（Distance-Vector）algorithm

which is widely used in real application. It submits routie information through UDP（User Datagram Protocol）and

sends upgrade packet every 30 seconds. If local router hasn’t received the upgrade packet from opposite end router

after 180 seconds, local router will mark all routing information from the opposite end to be unreachable; if some

route information hasn’t received upgrade packet from the opposite end in 120 seconds after marking to be

unreachable, local router will delete it from the route table.

The distance to the destination measured by Hop Count is Routing Metric. In RIP, the hop between router

and the straightly connected network is 0, and the hop will be 1 if passing through a network which router can reach,

and the rest may be deduced by analogy. To restrict convergfence time, RIP prescribe Metric is the intergeral number

between 0 to 15. The hop larger or equal to 16 is defined to be infinite, that is, the destination host or network is

unreachable.

There are such 2 versions as RIP-1 and RIP-2（RIP-2 supports plain text authentication）.

To improve capability and prevent routing ring, RIP supports Split Horizon and Poison Reverse.

Each router run RIP manages a routing database which contains all route item to all reachable desination.

These route information includes :

Destination address : IP address of host or network.

Next hop address : the next router address passed when going to the destination.

Output interface : the interface transferring packet.

Metric value : the cost to the destination which is an intergeral number from 0 to 16.

Timer : the time is from the last time the router is modified. Every time when the router is modified, the

timer is configured to be 0.

The process of RIP enabling and running is as following :

(1) Enabling RIP, router will send requery packet in the form of broadcast to neighbor routers. After

receiving it, neighbor routers (must enable RIP) will send response packet which contains local route table

information back.

(2) The router who has sent requery packet modifies local route table after receiving response packet.

(3) At the same time, RIP broadcasts or multicasts local route table every 30 seconds to neighbor routers to

maintain local route and choose a best route, and then, broadcast and multicast modify informationto neighbor

network to make global efficient of upgrading route. At the same time, RIP adopts overtime system to handle

overtime route to guarantee real time of route, As internal route protocol, RIP makes router know the route

information of the whole network through this system.

RIP has been one of the standard of delivering router and host route. The theory of switch with layer 3

switching IP packet is the same as that of router, so RIP is also adopted by layer 3 switch manufacturer. It can be used

in simple structured, strong continuitydistrict network, such as : residential community network. For complicated

large network, it is suggested not using RIP.

7.2 RIP Overview

RIP is a simple Interior Gateway Protocol (IGP), mainly used in small-sized networks, such as academic networks

and simple structured LANs. RIP is not applicable to complex networks.

RIP is still widely used in practical networking due to easier implementation, configuration and maintenance than

OSPF and IS-IS.