[Openswan Users] Re: help for multihome route

Jacco de Leeuw jacco2 at dds.nl
Sun Jul 10 01:58:35 CEST 2005

>>> problem for interface line.  I have not know device for adsl, can be
>>> ppp0 ppp1 ppp8, any ppp.  This because l2tpd assign anywhere ppp and
>>> can take away ppp0 - ppp3 I using for ADSL modem.  All need to happen
>>> is for one adsl go down, then sometime ipsec->l2tp happen, now ADSL is
>>> ppp12.
>> I believe Jacco had an answer for the moving ppp+ devices when L2TP is
>> used. I have CC:ed him on this message.
> The 'unit' parameter in ppp-2.4.2+ can make sure that L2TP/IPsec will
> use interface names with higher unit numbers so that the lower ones
> are free for the ADSL link. See also:
> http://lists.openswan.org/pipermail/users/2005-March/004164.html

As pointed out to me by Bob Benstro, this actually won't work if there
is more than 1 client. Pppd assigns the correct ppp unit number to the
first client but then it will try to assign the same unit number to the
second client. This fails with "Couldn't allocate PPP unit xxx as it is
already in use". The Linux PPP kernel code will not pick the next free
unit number but it picks ppp0 (which was supposed to be reserved for
the DSL link).

Probably a better solution is to assign high PPP unit numbers to the
DSL link(s) using the 'unit' parameter. Then the lower unit numbers
(ppp0, ppp1 etc.) are free for L2TP/IPsec clients. The 'unit' parameter
does not have to be used in /etc/ppp/options.l2tpd. This should work
as long as you assign a PPP unit number to the DSL link that is higher
than the total number of clients.

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

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