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TCP/IP and Data Communications Administration Guide

Parts of Basic Configuration File

The basic asppp.cf configuration file must contain at least two main sections: an ifconfig line and at least one path section. It can also contain a defaults section, which you use when you want to set the default values for an endpoint. (Refer to Chapter 11, Tailoring Your PPP Link, for a description of keywords used in the defaults section.)

Example 9-1 shows a basic configuration file such as you would create for a remote host to establish a point-to-point link with a dial-in server.

Example 9-1 Basic Configuration File


ifconfig ipdptp0 plumb nomada nubian-ppp up
   path
      interface ipdptp0
      peer_system_name nubian-ppp      # The name in the /etc/uucp/Systems file
      inactivity_timeout 300           # Allow five minutes before timing out

ifconfig Section of the asppp.cf File

The asppp.cf file must contain an ifconfig section with this syntax:

ifconfig interface-number plumb local-machine remote-machine up

Here is a description of the fields:

The link manager first runs the ifconfig command on the local machine to configure the ipdptp0 point-to-point interface. The zero in ipdptp0 gives the device number of the interface. The plumb option performs various activities necessary for IP to recognize the ipdptp0 interface. nomada is the name of the local host. nubian-ppp is the name of the dial-in server to which nomada connects through the point-to-point link. The ifconfig option up marks the ipdptp0 interface as up.

Note -

For more information about ifconfig, see Chapter 10, Troubleshooting PPP, and the ifconfig(1M) man page.

path Section of the asppp.cf File

The path section of the configuration file tells the link manager the name of the remote endpoint and the name of the interface linking the endpoint machines. At a minimum the path section should contain the following lines: 


path
   interface interface-number
   peer_system_name endpoint-name

interface Keyword

This keyword defines the PPP interface (either ipdptpn or ipdn). In Example 9-1, the following information appears in the path section: 


interface ipdptp0	  
peer_system_name nubian-ppp

The interface keyword identifies ipdptp0 as the point-to-point interface that local endpoint nomada uses to communicate with the remote endpoint in the manner described in this path section. It associates the peer_system_name with the interface.

peer_system_name Keyword

On a dial-out machine such as a remote host, the peer_system_name keyword takes the host name of the remote endpoint as its argument. This is the name of the remote endpoint given in /etc/uucp/Systems. The name need not be the same as the host name on the corresponding ifconfig line.

Note -

The argument to the peer_system_name keyword for a dial-in server has a different value. See "Configuration File for Multipoint Dial-in Server" for details.

In Example 9-1, peer_system_name identifies dial-in server nubian-ppp as the remote endpoint at the other end of this link. When the link manager reads the asppp.cf file, it then looks for the entry for nubian-ppp in the /etc/uucp/Systems file. (Recall that the Systems file contains information about how to set up communications with the remote endpoint, including that machine's telephone number. Refer to "Updating /etc/uucp/Systems for PPP".)

inactivity_timeout Keyword

The inactivity_timeout keyword is optional. It tells the link manager that the link can remain inactive for the interval designated. When that interval is passed, the link manager knows to automatically disconnect the link. The default interval is two minutes; you do not have to use inactivity_timeout unless you require a different inactivity interval.

Additional Keywords

You can supply other keywords in the asppp.cf file to define how endpoint machines should communicate. Chapter 11, Tailoring Your PPP Link, has complete information about these keywords.