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Sidewinder G2 6.1.1 Administration Guide - Glossary of Technical ...

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A<br />

A PPENDIX C<br />

Configuring Dynamic<br />

Routing with OSPF<br />

About this appendix This appendix describes how to set up routing capability on the<br />

<strong>Sidewinder</strong> <strong>G2</strong> using the Open Shortest Path First (OSPF) protocol.<br />

Tip: You should read this appendix only if you have identified that your routing topology<br />

is too complicated to use only static routing or the Routing Information Protocol (RIP).<br />

OSPF is a complex IP routing protocol and deploying OSPF should involve discussions<br />

between routing subject matter experts and security subject matter experts.<br />

This appendix addresses the following topics:<br />

“Overview” on page C-1<br />

“OSPF processing on a <strong>Sidewinder</strong> <strong>G2</strong>” on page C-4<br />

“Setting up OSPF routing on the <strong>Sidewinder</strong> <strong>G2</strong>” on page C-6<br />

“Configuring "passive" OSPF” on page C-13<br />

“Other implementation details” on page C-13<br />

Overview OSPF is a routing protocol in that it provides information used to<br />

figure out routes in a portion <strong>of</strong> a network. Unfortunately, it is not a<br />

routing protocol in that it does not actually pass routes, but<br />

information about links each router has. Based upon this link<br />

information, each router runs the same algorithm and comes up with<br />

the same "picture" <strong>of</strong> the network.<br />

Note: OSPF runs as its own protocol (protocol 89) on top <strong>of</strong> IP.<br />

OSPF uses a fair amount <strong>of</strong> multicasting. When a host detects a<br />

change to a routing table or a change in the network topology, it<br />

immediately multicasts the information to all other hosts in the<br />

network. Unlike the RIP in which the entire routing table is sent, the<br />

host using OSPF sends only the part that has changed. With RIP, the<br />

routing table is sent to neighboring hosts every 30 seconds. OSPF<br />

multicasts updated information only when a change occurs.<br />

C<br />

Configuring Dynamic Routing with OSPF C-1

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