[Openswan Users] L2TP/IPSEC & DSL ppp interface assignment

Jacco de Leeuw jacco2 at dds.nl
Fri Mar 11 16:48:33 CET 2005

Lewis Shobbrook schreef:

> while the connection is down we get an L2TP/IPSEC VPN connection coming
> in which then occupies the ppp0, when the DSL service comes back online
> it takes the next available ppp interface such as ppp1.
> Is there anyway to assign or reserve the ppp interface to prevent this
> from happening?

Yes, you can add 'unit 1' to /etc/ppp/options.l2tpd. Then pppd will look
for a free ppp unit number starting from ppp1. 'unit 2' means it will start
from ppp2 etc. etc. This will allow you to reserve ppp0 for the DSL link.

You do need ppp-2.4.2 or higher for this option. The pppd man page says that
it only works for outbound connections but it works for incoming connections
too (undocumented feature in pppd?). See also this discussion over at the
l2tpd mailinglist:


Jacco de Leeuw                         mailto:jacco2 at dds.nl
Zaandam, The Netherlands           http://www.jacco2.dds.nl

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