Linux Network Administrator's Guide, Second Edition

Running in Server Mode

Setting up your SLIP client was the hard part. Configuring your host to act as a SLIP server is much easier.

There are two ways of configuring a SLIP server. Both ways require that you set up one login account per SLIP client. Assume you provide SLIP service to Arthur Dent at dent.beta.com. You might create an account named dent by adding the following line to your passwd file:

dent:*:501:60:Arthur Dent's SLIP account:/tmp:/usr/sbin/diplogin

Afterwards, you would set dent’s password using the passwd utility.

The dip command can be used in server mode by invoking it as diplogin. Usually diplogin is a link to dip. Its main configuration file is /etc/diphosts, which is where you specify what IP address a SLIP user will be assigned when he or she dials in. Alternatively, you can also use the sliplogin command, a BSD-derived tool featuring a more flexible configuration scheme that lets you execute shell scripts whenever a host connects and disconnects.

When our SLIP user dent logs in, dip starts up as a server. To find out if he is indeed permitted to use SLIP, it looks up the username in /etc/diphosts. This file details the access rights and connection parameter for each SLIP user. The general format for an /etc/diphosts entry looks like:

# /etc/diphosts
user:password:rem-addr:loc-addr:netmask:comments:protocol,MTU
#

Each of the fields is described in Table 7.2.

Table 7-2. /etc/diphosts Field Description

Field	Description
user	The username of the user invoking ...