Cisco 1003 - 1003 Router Manual de usuario descargar pdf (Pagina 10)

11-10 Internetwork Design Guide

Dial-on-Demand Routing

Conﬁguring IP DDR over ISDN

In Figure 11-3, Router A dials Router B and Router B dials Router A over ISDN by means of IP

DDR.

Figure 11-3 Sample IP ISDN Topology

IP Addressing

Use the ip address command to assign an IP address to the ISDN interface. The ISDN interface of

both routers must be on the subnet. Alternatively, you can use the ip unnumbered interface

command instead of the ip address command. The ip unnumbered interface command allows the

ISDN interface to the IP address of a LAN interface as its own.

IP Routing

IP routing between sites can be handled by static routes or a routing protocol such as Routing

Information Protocol (RIP), Interior Gateway Routing Protocol (IGRP), Enhanced IGRP, or Open

Shortest Path First (OSPF). Because they send regular update packets, routing protocols are usually

ill-suited for ISDN networks because they initiate costly connections solely for the purpose of

sending update packets. If you are using RIP or IGRP, you can control update packets by using

snapshot routing. (For a discussion of snapshot routing, see the “Snapshot Routing” section later in

this chapter.

To conﬁgure static routes, use the ip route global conﬁguration command. The ip route command

maps IP hosts and networks to an intermediate address. The conﬁguration for the remote router

(Router B) maps all destinations available at the central site to the central site BRI port’s address (the

intermediate address).

Note If the central site is running a routing protocol, the central site router must use the

redistribute router conﬁguration command with the static keyword to redistribute the static routes

for the remote site.

Router A Router B

171.68.158.18

255.255.255.248

171.68.158.49

255.255.255.248

171.68.158.26

255.255.255.248

171.68.158.25

255.255.255.248

E0 E0

ISDN

S4440

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Cisco 1003 - 1003 Router Manual de usuario Pagina 10