Configuration File for Multipoint Dial-in Server

The asppp.cf configuration file for a multipoint dial-in server contains the same basic sections as that for a point-to-point link: an ifconfig section, at least one path section, and, if desired, a defaults section.

Example 9-2 shows a configuration file for the dial-in server nubian introduced in Figure 9-1.

Example 9-2 Configuration File for a Multipoint Dial-in Server

ifconfig ipd0 plumb nubian-ppp up

path
   interface ipd0
   peer_system_name tamerlane  # The user name this remote
                               # machine logs in with when it
                               # dials this server
   	peer_ip_address nomada
                               # nomada is a remote machine that
                               # dials in to this server

# nomadb is another remote machine that dials in to nubian

path
   interface ipd0
   peer_system_name lawrence
   peer_ip_address nomadb

# nomadc is another remote machine that dials in to nubian

path
   interface ipd0
   peer_system_name azziz
   peer_ip_address nomadc

ifconfig Section for Multipoint Dial-in Server

The ifconfig section for a multipoint dial-in server has a slightly different syntax than that for a point-to-point link. This syntax is:

ifconfig ipdn plumb server-name up

The major difference is that no destination end points are listed as arguments to ifconfig. Instead, the link manager picks up this information from the path section of the asppp.cf file.

In Example 9-2, the link manager first runs the ifconfig command on the dial-in server to configure multipoint interface ipd0. The zero in ipd0 gives the device number of the interface. The option plumb performs various activities necessary for IP to recognize the ipd0 interface. The ifconfig option up marks interface ipd0 as up.

You may have to supply a netmask + parameter on the ifconfig line if you use subnetting.

path Section for Multipoint Dial-in Server

The path section of the asppp.cf file tells the link manager the name of the remote endpoint and the name of the interface linking the endpoint machines. However, on a multipoint dial-in server, you can include more than one path section. Additionally, some of the arguments to the keywords are used differently with multipoint links.

path
    interface interface-number
    peer_system_name endpoint-username
    peer_ip_address endpoint-hostname

You need to define a path section for each nomadic endpoint with which the dial-in server can establish connections.

interface Keyword

For a multipoint dial-in server, the interface keyword defines the PPP interface ipdn. You must specify the same PPP interface in the path section for every endpoint that communicates with the server through this interface.

peer_system_name Keyword

The peer_system_name keyword takes a slightly different argument for a dial-in machine than a dial-out machine. For a dial-in server, this argument is the login name used by the remote host when it tries to establish communications with the server. This user name must already be present in the server's /etc/passwd file. When the login service reads this name, it verifies the user name in the /etc/passwd and /etc/shadow files enabling communications.

In this excerpt from Example 9-2:

path
    interface ipd0
    peer_system_name scarlett
    peer_ip_address nomadc

the argument to peer_system_name is scarlett, indicating that when nomadc logs in to nubian-ppp, it uses the login name scarlett.

peer_ip_address Keyword

The peer_ip_address keyword is required for multipoint links. It takes the host name or IP address of the remote endpoint as its argument. The example above uses the host name nomads as the argument to keyword peer_ip_address.

Additional Keywords

You can supply other keywords in the asppp.cf file to define how endpoint machines should communicate. Refer to Chapter 11, Tailoring Your PPP Link, for a complete list of keywords.