1.4 Selecting Cisco Remote Access Solutions
1.4.2 Determining the appropriate interfaces - fixed interfaces
The router that you select for your WAN connection must offer the interfaces that will support your WAN connection.

Typical interfaces that are found on a router and the typical WAN connections supported are as follows:

  • Asynchronous serial -- Used with a modem, it supports asynchronous dialup connections.
  • Synchronous serial -- It supports connections such as leased lines, Frame Relay, and X.25.
  • BRI -- It supports ISDN BRI connections.
  • Channelized T1 or E1 -- It supports connections such as leased lines, dialup, ISDN PRI, and Frame Relay.

Routers can have fixed configurations. Fixed-configuration routers are available with predetermined fixed LAN and WAN interface options. Fixed-configuration routers do not require additional WAN interface cards or network modules. However, once purchased, the interfaces available are limited only to those that are factory installed.

The Figure shows a router with a fixed configuration.