User guide

Internetworking Primer A-37

Modems

Modems are used with access servers to allow remote nodes and remote LANs to connect

to internetworks across Public Switched Telephone Networks (PSTNs). (See Figure A-14.)

This section contains the following sections:

• EIA/TIA-232 Standard and Cabling

• Conﬁguring the Asynchronous Port

• Communicating with the Modem

• Conﬁguring the Modem

• Testing the Dial-In Connection

Dialup access to an internetwork is achieved via modems connected to the asynchronous

port of the access server. Before services such as remote node, remote LAN, and terminal

services can be utilized by a remote device, the modem and access server must be

conﬁgured to provide a reliable point-to-point WAN link. This section provides the

background information the is required to resolve modem conﬁguration issues, and step

you through a modem setup.

Figure A-14 Connection Between an Access Server and a Modem

EIA/TIA-232 Standard and Cabling

This section discusses the EIA/TIA-232 implementation in detail as it applies to connecting

the access server with the modem. On an EIA/TIA-232 connection between an access

server and a modem, the access server is deﬁned as data terminal equipment (DTE) and the

modem is deﬁned as data circuit-terminating equipment (DCE).

Router A

H3075

Public Switched

Telephone

Network

Access

server

Modem