3.3.m Split horizon…

Split Horizon

loop prevention

rule: a routing interface cannot send routing information out the same interface upon which

it was received

Route Summarization

Routing information can be condensed (summarized) from a longer prefix into a shorter prefix; the routing table is more efficient, reduced, and routing updates are fewer.

ex.

10.1.1.0/24

10.1.2.0/24

10.1.3.0/24

00001010.00000001.00000001.00000000

00001010.00000001.00000011.00000000

10.1.1.0/22

Classful routing protocols do not include vlsm in their updates. they are delineated by classful masking.

ex. 10.0.0.0/8 172.16.0.0/16 192.168.1.0/24 (rfc 1918)

255.0.0.0 class A 255.255.0.0 class B 255.255.255.0 class C

IP Classless

The ip classless command was introduced into default behavior for ios 12.0. Classful routing protocols, ie. Rip and IGRP discard traffic bound for any unknown subnet of a major network, even with a default route configured. IP classless allows for the use of a default route in this case.