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Chapter 2

Routing Principles

We will discuss RIP and IGRP in detail in the following sections.

RIP

Routing Information Protocol (RIP) is a true distance-vector protocol. It
sends the complete routing table out to all active interfaces every 30 seconds.
RIP uses only hop count to determine the best way to a remote network, but
it has a maximum allowable hop count of 15, meaning that 16 is deemed
unreachable. RIP works well in small networks, but it is inefficient on large
networks with slow WAN links or on networks with a large number of rout-
ers installed.

RIP version 1 uses only classful routing, which means that all devices in

the network must use the same subnet mask. This is because RIP version 1
does not send updates with subnet mask information in tow. RIP version 2
provides what is called prefix routing and does send subnet mask informa-
tion with the route updates. RIPv2 uses classless routing.

To keep a network stable, RIP uses timers.

RIP Timers

RIP uses three different kinds of timers to regulate its performance:

Route update timer Sets the interval (typically 30 seconds) between
periodic routing updates in which the router sends a complete copy of its
routing table out to all neighbors.

Load balancing
with unequal
paths

VLSM support

Metric

Hops

Composite

Hop count limit

255 (100 by
default)

Support for size of
network

Medium

Large

T A B L E 2 . 2

Distance-Vector Comparisons (continued)

Characteristic

RIPv1

RIPv2

IGRP

EIGRP

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