Cisco 1003 - 1003 Router Bedienungsanleitung PDF herunterladen (Seite 22)

11-22 Internetwork Design Guide

Tariff Management

Routing

Routing protocols can generate trafﬁc that causes connections to be made unnecessarily. The

following techniques can be used to control routing protocol trafﬁc:

• Static Routes

• Snapshot Routing

Static Routes

With static routes, all routes are entered manually, eliminating the need for a routing protocol to

broadcast routing updates. Static routes can be effective in small networks that do not change often.

However, static routes in large networks that change often can become an administrative burden. Be

sure to use access lists to control other packets that the protocol might generate.

Snapshot Routing

With snapshot routing, the router is conﬁgured for dynamic routing; snapshot routing controls the

update interval of the routing protocols. Snapshot routing works with the following distance vector

protocols:

• Routing Information Protocol (RIP) for IP

• Interior Gateway Routing Protocol (IGRP) for IP

• Routing Information Protocol (RIP) and Service Advertisement Protocol (SAP) for Novell

Internet Packet Exchange (IPX)

• Routing Table Maintenance Protocol (RTMP) for AppleTalk

• Routing Table Protocol (RTP) for Banyan VINES

Under normal circumstances, these routing protocols broadcast updates every 10 to 60 seconds, so

an ISDN link would be made every 10 to 60 seconds simply to exchange routing information. From

a cost perspective, this frequency is prohibitive. Snapshot routing solves this problem.

Note Snapshot routing is available in Cisco IOS Software Release 10.2 or later.

Snapshot Model

Snapshot routing uses the client-server design model. When snapshot routing is conﬁgured, one

router is designated the snapshot server, and one or more routers are designated as snapshot clients.

The server and clients exchange routing information during an active period. At the beginning of the

active period, the client router dials the server router to exchange routing information. At the end of

the active period, each router takes a snapshot of the entries in its routing table. These entries remain

frozen during a quiet period. At the end of the quiet period, another active period begins, and the

client router dials the server router to obtain the latest routing information. The client router

determines the frequency at which it calls the server router. The quiet period can be as long as

100,000 minutes (approximately 69 days).

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Cisco 1003 - 1003 Router Bedienungsanleitung Seite 22