In its typical configuration, using FreeBSD as a SLIP server works as
follows: a SLIP user dials up your FreeBSD SLIP Server system and logs
in with a special SLIP login ID that uses /usr/sbin/sliplogin
as the special user's shell. The sliplogin program browses the
file /etc/sliphome/slip.hosts to find a matching line for
the special user, and if it finds a match, connects the serial line to
an available SLIP interface and then runs the shell script
/etc/sliphome/slip.login to configure the SLIP interface.
For example, if a SLIP user ID were Shelmerg, Shelmerg's
entry in /etc/master.passwd would look something like this
(except it would be all on one line):
Shelmerg:password:1964:89::0:0:Guy Helmer - SLIP:
/usr/users/Shelmerg:/usr/sbin/sliplogin
and, when Shelmerg logs in, sliplogin will search
/etc/sliphome/slip.hosts for a line that had a matching user
ID; for example, there may be a line in
/etc/sliphome/slip.hosts that reads:
Shelmerg dc-slip sl-helmer 0xfffffc00 autocomp
sliplogin will find that matching line, hook the serial line into
the next available SLIP interface, and then execute
/etc/sliphome/slip.login like this:
/etc/sliphome/slip.login 0 19200 Shelmerg dc-slip sl-helmer 0xfffffc00 autocomp
If all goes well, /etc/sliphome/slip.login will issue an
ifconfig for the SLIP interface to which sliplogin
attached itself (slip interface 0, in the above example, which was the
first parameter in the list given to slip.login) to set the
local IP address (dc-slip), remote IP address
(sl-helmer), network mask for the SLIP interface
(0xfffffc00), and any additional flags (autocomp).
If something goes wrong, sliplogin usually logs good
informational messages via the daemon syslog facility, which usually
goes into /var/log/messages (see the manual pages for
syslogd(8) and syslog.conf(5), and perhaps check
/etc/syslog.conf to see to which files syslogd is
logging).
OK, enough of the examples -- let us dive into setting up the system.