Networking Concepts Review - CCIE Routing and Switching Exam Certification Guide - page 49

Classless and Classful Routing Protocols Table 2-12

Type Routing Protocols

Classful RIPv1, IGRP

Classless OSPF, EIGRP, IS-IS, RIPv2, BGP

Routing Metrics

Table 2-13

Metric Description

Hop count Counts the number of routers that the packet must cross to reach a destination.

Bandwidth Uses the default or configured interface bandwidth.

Cost Derived from the bandwidth of the interface. The formula to calculate cost is as follows:

10 8 / BW, where BW is the default or configured bandwidth of the interface.

Delay Length in time to move a packet to the destination.

Reliability Dependability of a network link. Measured with the expected keepalives.

Load Refers to the degree to which the interface link is busy.

Loop Prevention Techniques

Table 2-14

Technique Description

Simple split horizon Routes that are learned from a neighboring router are not sent back to that

neighboring router, thus suppressing the route.

Split horizon with
poison reverse

Routes that are learned from a neighboring router are announced back to that
router with an infinite metric.

Triggered updates Update message sent immediately for a route for which the metric has changed,

sent before the periodic update timer expires.

Counting to infinity Keeps track of router hops as the packet travels through the network. If the

maximum limit is reached, the packet is discarded.