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4.1 | ![]() |
RIP v2 Overview | |
4.1.5 | ![]() |
Classless route lookups |
Module 2, Advanced IP Addressing
Management, explains classful route lookups, in which a destination address is first
matched to its major network address in the routing table and is then
matched to a subnet of the major network. If no match is found at
either of these steps, the packet is dropped.
This default behavior can be changed, even
for classful routing protocols such as RIP v1 and Interior Gateway
Routing Protocol (IGRP). Change the default behavior by entering the
ip classless
global command.
When a router performs classless route lookups, it does not pay
attention to the class of the destination address. Instead, it
performs a bit-by-bit best match between the destination address and
all its known routes. This capability can be very useful when working
with default routes, as demonstrated in Module 3, Routing Overview.
Classless route lookups can be very powerful when coupled with the
other features of classless routing protocols.
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