3.1 PPP Architecture
3.1.5
Configuring dedicated or interactive PPP sessions

You can configure one or more asynchronous interfaces on your access server to be in dedicated network interface mode. In dedicated mode, an interface is automatically configured for PPP connections. There is no user prompt or EXEC level, and no end-user commands are required to initiate remote-node connections.

To ensure that the dial-in user must run PPP on the specified line, use the async mode dedicated command:

Router(config-if)# async mode dedicated

Dedicated Mode

When the interface is configured for dedicated mode, the end user cannot change the encapsulation method, address, or other parameters.

In interactive mode, a line can be used to make any type of connection, depending on the EXEC command entered by the user. For example, depending on its configuration, the line can be used for Telnet connections, or for PPP encapsulation. The user is prompted for an EXEC command before a connection is initiated.

To allow the dial-in user to run PPP or EXEC on the specified line, configure the async mode interactive command:

Router(config-if)# async mode interactive

By default, no async mode is configured. In this state, the line is not available for inbound networking because the  PPP connections are disabled.

Commands Input Sequence

If you try to configure the line with autoselect ppp prior to configuring the async mode interactive command, you see the following error message:

%Autoselect w/o the interface command 'Async mode interactive' is useless