Getting PPP set up under solaris isn't so difficult.
If you really want details, keep reading. However, if you just want to get
it working in a hurry, you probably just want to run
http://www.bolthole.com/solaris/configppp.sh

The problem is that you have to deal with THREE files:

1. your /etc/hosts file
2. your /etc/asppp.cf file
3. your /etc/uucp/Systems file.

(Oh. you also have to make sure you have the "Basic Networking" package 
 installed, when you install solaris. Otherwise, run pkgadd for 
 SUNWbnur & SUNWbnuu, from the Packages dir on the cdrom )

In /etc/hosts, put, with appropriate substitutions,

  1.2.3.4 my-dialup
  2.3.4.5 my-isp

Even if you have a dynamic address, just put SOMETHING as the address
of "my-dialup".

In /etc/asppp.cf, put

  ifconfig ipdptp0 plumb my-dialup my-isp up

  path
    interface ipdptp0
    peer_system_name my-isp
    #if you need dynamic addressing, uncomment the following
    negotiate_address on
    # you probably do NOT want "default_route" in here.
    # It does not work quite how you'd expect.
    #
    # for gruesome amounts of info, "man aspppd"

Fairly simple, isn't it?
The somewhat tricky part comes putting together the Systems file.
You should be able to get away with something like

my-isp Any ACU 38400 3101234567 "" P_ZERO gin: mylogic word: mypasswd

Or, worst case, something like

my-isp Any ACU 38400 3101234567 "" P_ZERO gin: mylogic word: mypasswd nex: ppp

the "nex: ppp" bit is for "Annex" boxes, that give you an "Annex:" prompt. At
which point, you have to tell it "ppp", to "start up ppp"

the "38400" is serial port speed. After you have things working at 38400,
feel free to try cranking it up to 57600m 76800, or even 115200

After doing all the above, and rebooting, all you would have to do is
"/usr/sbin/ping my-isp" and your connection should come up after about 40
seconds. [there are other ways than rebooting, but that's the simplest]

remember, the manpage on aspppd has lots of info. For example, you can crank up
the debuggint level, and look at /etc/log/asppp.log to find out if something
is going horribly wrong.

And for lots more modem tricks, check out www.stokely.com


------------------------------------------------------------

Oh. one more rather important thing. If the above works for you, then you'll
want to move on to higher speeds. But to do so, you'll want to add


STTY=crtscts

to the end of the "hayes" line in /etc/uucp/Dialers. (Right after "CONNECT ")

[sorry, typo: previously I had said "STTY=rtscts" or something]

This should allow you to use 115200 port speed, assuming your serial port
hardware isn't seriously broken.

Unfortunately, if you're reading this on a sparc box, and it isn't one of the
newer ultras, then "your serial port hardware is seriously broken"


For making a dial-IN server, using PAP authentication, see also
http://www.bolthole.com/solaris/ppp-PAP.txt