Summary of Interior Routing Protocols

Before finishing your study for the ICND or CCNA exam, you will learn a lot more about RIP-1, IGRP, EIGRP, and OSPF. This chapter has introduced you to some of the key terms and points of comparison for these routing protocols, as well as a few others. Table 14-6 summarizes the most important points of comparison between the interior routing protocols, and Table 14-7 lists some of the key terminology.

Table 14-6 Interior IP Routing Protocols Compared: Summary

Routing Protocol

Metric

Convergence Speed

Supports VLSM and Is a Classless Routing Protocol

Default Period for Full Routing Updates

RIP-1

Hop count

Slow

No

30 seconds

RIP-2

Hop count

Slow

Yes

30 seconds

IGRP

Calculated based on constraining bandwidth and cumulative delay

Slow

No

90 seconds

EIGRP

Same as IGRP, except multiplied by 256

Very fast

Yes

N/A

OSPF

Cost, as derived from bandwidth by default

Fast

Yes

N/A

Integrated IS-IS

Metric

Fast

Yes

N/A

Table 14-7 Routing Protocol Terminology

Term

Definition

Routing protocol

A protocol whose purpose is to learn the available routes, place the best routes into the routing table, and remove routes when they are no longer valid.

Exterior routing protocol

A routing protocol designed for use between two different organizations. These typically are used between ISPs or between a company and an ISP. For example, a company would run BGP, an exterior routing protocol, between one of its routers and a router inside an ISP.

Interior routing protocol

A routing protocol designed for use within a single organization. For example, an entire company might choose the IGRP routing protocol, which is an interior routing protocol.

Distance vector

The logic behind the behavior of some interior routing protocols, such as RIP and IGRP.

Link state

The logic behind the behavior of some interior routing protocols, such as OSPF.

Balanced hybrid

The logic behind the behavior of EIGRP, which is more like distance vector than link state but is different from these other two types of routing protocols.

Dijkstra Shortest Path First (SPF) algorithm

Magic math used by link-state protocols, such as OSPF, when the routing table is calculated.

Diffusing Update Algorithm (DUAL)

The process by which EIGRP routers collectively calculate the routes to place into the routing tables.

Convergence

The time required for routers to react to changes in the network, removing bad routes and adding new, better routes so that the current best routes are in all the routers' routing tables.

Metric

The numeric value that describes how good a particular route is. The lower the value is, the better the route is.

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