SUMMARY: Chat script for null-modem PPP?

From: Homan, Charles (NE) <Charles.Homan_at_GDC4S.Com>
Date: Wed Mar 12 2003 - 16:32:14 EST
First, my thanks to the respondees: Darren Dunham, Lars Hecking, Alan Pae,
and Bill Voight.  I was pointed to both (which I was
already using :-) and

This was far easier than I was attempting to make it.  (Ah, the bad old days
of aspppd!)  However, a couple points are worth mentioning.  (And - in a
mini-rant - what is the point of a SUMMARY if no one can follow it without
knowing your system intimately?  Mini-rant #2: PLEASE summarize your
questions and their answers!!!  I feel better now. ;-)

In "Celeste's Tutorial on Solaris 2.x Modems and Terminals"
(, I noticed a
phrase I missed on the first reading: "NEVER use software flow control with
UUCP/PPP or the protocol will go nuts from the unexpected XON and XOFF
characters".  (It appears that there is an option in PPP 4.0 which accepts
software flow control, but I didn't wind up using it.)  Second, the
null-modem cable I was originally given was wired wrong.  The guy who wired
it swore it would work, but he was testing it on a PC.  His pinouts were:


The proper wiring, as I eventually convinced him, is:


See  Once
the cable was wired properly I could tip with hardware flow control turned

Since my configuration is on a private network I could use "noauth", which
effectively does away with the chat script.  I removed the port monitor on
ttya since it wasn't needed:
# pmadm -r -p zsmon -s ttya
(I'm not positive this is necessary, though.)

Also, since these machines will only ever connect to each other I could just
use the /etc/ppp/options file for all of my connection info.  To wit, on

# cat /etc/ppp/options
machine1-serial:machine2-serial     (reversed on machine2)
logfile /var/adm/ppplog
debug                               (just for debugging... ;-)

I used the file /etc/ppp/ifconfig to start pppd in preference to changing
the default init script (/etc/init.d/pppd):
# cat /etc/ppp/ifconfig

For use in the options file (and for my convenience later) I defined names
for the serial ports in /etc/hosts:
# cat /etc/hosts machine1              (replaced with machine2's IP/name on
machine2) machine1-serial machine2-serial

I used the file /etc/ppp/ip-up to initiate my routes:
# cat /etc/ppp/ip-up
/usr/sbin/ndd -set /dev/ip ip_forwarding 1
/usr/sbin/route add   (/27 masked network,
route through machine2-serial; different route and gateway on machine2, but
the same principle)

(Note that I did *not* want defaultroute on my ppp line, as each machine is
connected to networks that the other shouldn't necessarily know about.)

With all of that in place, I can boot the machines in either order.  The
first machine to come up attempts to initiate a connection.  If (when) it
fails, it simply waits passively for the other machine.  When the second
machine comes up, it attempts to initiate a connection which is accepted by
the first machine, they both turn on IP forwarding and set up their routing
tables, and everything works.


> -----Original Message-----
> From: Homan, Charles (NE) 
> Sent: Monday, March 10, 2003 2:55 PM
> To: ''
> Subject: PARTIAL SUMMARY: Chat script for null-modem PPP?
> OK, I think the chat piece is good to go now, but I don't have a good
> connection yet.  Thanks to Lars Hecking and Darren Dunham for their
> responses.  Lars suggested the following:
> >  Only ever used ppp for dialing in over a phone line, but 
> you probably get
> >  by with
> > TIMEOUT (some number)
> > CONNECT ''
> > 'ogin:' (user id)
> > 'word:' (passwd)
> > 'prompt' ppp
> > 
> >  where prompt is replaced with the actual prompt you get. 
> Above is what is
> >  left over after taking out abort and modem commands from 
> my laptop dialin
> >  chat script.
> I have done this, and it seems to work as far as logging in 
> goes.  However,
> I get gobbledegook (stuff that looks like line noise) when 
> the connection is
> made, and it then times out.  (I connect by running pppd at 
> the prompt.)
> Also, when I use tip to connect from the "client" machine, I 
> can log in as a
> normal user and it acts like tip should.  When I log in as 
> ppp_user, though,
> I get the same gobbledegook as when I run pppd, and then get 
> dropped back to
> a login: prompt.
> I used admintool to configure the serial ports.  I'm using a 
> 19200 baud
> connection with software flow control, with "Service enable" 
> turned on on
> the server and off on the client.  I didn't change much else.
> Any ideas what could be wrong?
> Thanks,
> Charles
> > -----Original Message-----
> > From: Homan, Charles (NE) 
> > Sent: Thursday, March 06, 2003 5:01 PM
> > To: ''
> > Subject: Chat script for null-modem PPP?
> > 
> > 
> > All:
> > 
> > I am currently struggling with getting two machines (Sunblade 
> > 100s running
> > Solaris 8) to talk to each other via pppd over a null-modem serial
> > connection.  I am unclear what my chat script should look 
> > like.  Do I just
> > want them to look for "ogin:" and "word:" and issue the 
> > proper responses, or
> > is there more to it?  (Actually, if there isn't more to it, 
> > I'm not sure
> > what I'm doing wrong.)  Any help would be most appreciated!
> > 
> > Thanks,
> > Charles
> > _______________________________________________
> > sunmanagers mailing list
> >
> >
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> sunmanagers mailing list
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Received on Wed Mar 12 16:37:45 2003

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