etcnet-0.9.5-alt1 при такой конфигурации (по ext избыточна и наверняка сводится
к ONBOOT, BOOTPROTO, USE_IFPLUGD и LINKDETECT) слишком рано запускает pppd, даже
если попытки подъёма обоих интерфейсов укладываются в одну и ту же секунду в логе:

=== /etc/net/ifaces/ext/options 
DISABLED=no
BOOTPROTO=dhcp
ONBOOT=yes
USE_PCMCIA=no
USE_HOTPLUG=no
USE_IFPLUGD=auto
LINKDETECT=yes
CONFIG_IPV4=yes
TYPE=eth
MODULE=8139too
#MODULE=skge
===

=== /etc/net/ifaces/ppp0/options
ONBOOT=no
PPPTYPE=pptp
PPTP_SERVER=vpn.gw.ip.addr
REQUIRES=ext
===

=== /var/log/messages
Jan 15 13:40:38 home ifplugd(ext)[3410]: ifplugd 0.28 initializing.
Jan 15 13:40:38 home kernel: ext: link up, 100Mbps, full-duplex, lpa 0x41E1
Jan 15 13:40:38 home ifplugd(ext)[3410]: Using interface ext/00:02:44:6B:77:0E
with driver <8139too> (version: 0.9.27)
Jan 15 13:40:38 home ifplugd(ext)[3410]: Using detection mode: SIOCETHTOOL
Jan 15 13:40:38 home ifplugd(ext)[3410]: Initialization complete, link beat
detected.
Jan 15 13:40:38 home pppd[3428]: pppd 2.4.4 started by root, uid 0
Jan 15 13:40:38 home pppd[3428]: Using interface ppp0
Jan 15 13:40:38 home pppd[3428]: Connect: ppp0 <--> /dev/pts/6
Jan 15 13:40:38 home pptp[3429]: anon log[main:pptp.c:267]: The synchronous pptp
option is NOT activated
Jan 15 13:40:38 home pptp[3429]: anon warn[pptp_gre_bind:pptp_gre.c:95]:
connect: Network is unreachable
Jan 15 13:40:38 home pptp[3429]: anon fatal[main:pptp.c:275]: Cannot bind GRE
socket, aborting.
Jan 15 13:40:38 home pppd[3428]: Script /usr/sbin/pptp --nolaunchpppd
VPN.GW.IP.ADDR  finished (pid 3429), status = 0x1
Jan 15 13:40:38 home pppd[3428]: Modem hangup
Jan 15 13:40:38 home pppd[3428]: Connection terminated.
Jan 15 13:40:38 home pppd[3428]: Exit.
Jan 15 13:40:38 home ifplugd(ext)[3410]: Executing
'/etc/net/scripts/ifplugd.action ext up'.
Jan 15 13:40:38 home dhcpcd[3525]: dhcpConfig: fopen: Permission denied
Jan 15 13:40:38 home dhcpcd.exe: interface ext has been configured with new
IP=MY.ETH.IP.ADDR
Jan 15 13:40:38 home ifplugd(ext)[3410]: Program executed successfully.
===

Пока в alterator-net-pptp 0.5.1 (сегодня надеюсь пушнуть в git.alt) сделано так:

=== alterator-net-pptp/backend3/net-pptp
################### interface helpers

# sleep order is on purpose: dhcp runs in background
start_iface()
{
        [ -n "$1" ] || return
        debug -n "start_iface[$1]: "
        for i in `seq 1 $retries`; do
                ifcheckup "$1" && break
                ifup "$1"
                sleep 1
        debug -n "$i "
        done
}

# if it's up, ensure it's down first, then back up
stop_iface()
{
        [ -n "$1" ] || return
        debug -n "stop_iface[$1]: "
        for i in `seq 1 $retries`; do
        debug -n "$i "
                ifcheckup "$1" || break
                ifdown "$1"
                sleep 1
        done
}

# do our best so that $1 is working
# FIXME: this should become redundant when etcnet
# gets fixed
bring_up()
{
        [ -n "$1" ] || return
        debug "bring_up[$1]"

        # ensure underlying iface is up
        start_iface "$in_iface"

        # workaround: etcnet might try to bring up ppp too early
        # when underlying eth is configured via dhcp and is down
        sleep 1

        # try to wait until ppp0 might go down (otherwise 
        # additional static route might not appear)
        stop_iface "$1"
        start_iface "$1"
}
===

Последнюю функцию надеюсь со временем упразднить :)

=== /usr/lib/alterator-net-common/ifcheckup
#!/bin/sh

[ -n "$(/sbin/ip link show up dev "$1")" ]
===