Using PPP networking under Linux

Bill Unruh | 1 Dec 2002 03:41

Re[2]: specific interface

On Sun, 1 Dec 2002, Nerijus Baliunas wrote:

> I entered it in options file, but with ppp-2.3.11 I get

Well, I guess the answer then is to upgrade to pppd 2.4.1
in which that option does exist.
Since it is an undocumented option, it could also disappear in the
future.

Or follow my previous suggestion that any setup be done with the ip-up
and ip-down scripts.
(What operating system are you using?)

>
> # pppd call omn
> pppd: In file /etc/ppp/peers/omn: unrecognized option 'unit'
>
>
> > There is an undocumented option for pppd called unit
> > You can specify a unit number on the line with that
> > eg
> > pppd unit 0 ...............
> > to request unit 0
> >
> >
> > It will try to use that number but if it is unavailable for any reason,
> > it will go on to ask for the next available one.
> >
> > It is more robust to use ip-up to do whatever setup you want for
> > whatever unit number was assigned, instead of assuming your call was on

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Nerijus Baliunas | 3 Dec 2002 15:06

Re[3]: specific interface

On Sat, 30 Nov 2002 18:41:46 -0800 (PST) Bill Unruh <unruh <at> physics.ubc.ca> wrote:

> > I entered it in options file, but with ppp-2.3.11 I get
> # pppd call omn
> pppd: In file /etc/ppp/peers/omn: unrecognized option 'unit'
> 
> Well, I guess the answer then is to upgrade to pppd 2.4.1
> in which that option does exist.

Upgraded. But, I have unit 3 in options file (tried at the
command line also), but still:

pppd[10697]: Using interface ppp1

Regards,
Nerijus

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James Cameron | 1 Dec 2002 23:35

Re: Re[2]: specific interface

On Sun, 2002-12-01 at 13:41, Bill Unruh wrote:
> Since it is an undocumented option, it could also disappear in the
> future.

"unit" was recently documented in pppd/pppd.8 in CVS.  Saw it in a "cvs
update" last week.

I don't see why documenting it would keep it existing in future.  If it
has to go, it will be removed.

I do agree that relying on an interface unit number is risky, and ip-up
scripting is safer.  It's why I'd like to be able to change the name of
the interface as well.  

(Horror story: I've had a firewall with an eth0 and eth1 interface, and
my scripts assumed that eth0 was always the external interface.  It
always was in my tests.  Then one day the order in which the cards were
detected changed, and suddenly my firewall was in circuit backwards.  On
the next boot, it went back to the usual way, but occasionally it would
boot backwards.  I did solve it in the end; change one of the cards.)

Nerijus: use ppp8 and ppp9, so that any later ppp interfaces you create
as ppp0 won't overload the meaning, or pre-empt the ones that you intend
should exist.

--

-- 
James Cameron                                     (james.cameron <at> hp.com)

http://quozl.linux.org.au/         (or)         http://quozl.netrek.org/

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Bill Unruh | 2 Dec 2002 03:21

Re: Re[2]: specific interface

On 2 Dec 2002, James Cameron wrote:

> On Sun, 2002-12-01 at 13:41, Bill Unruh wrote:
> > Since it is an undocumented option, it could also disappear in the
> > future.
>
> "unit" was recently documented in pppd/pppd.8 in CVS.  Saw it in a "cvs
> update" last week.
>
> I don't see why documenting it would keep it existing in future.  If it
> has to go, it will be removed.

Documented options are assumed to be used by a large number of people,
and the maintainers will get rid of it only for very good reasons.
Undocumented options can be assumed to not be used except by
"experimentalists" and can disappear for no good reason, or if they
become inconvenient.

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