Comment 2 for bug 793559

/etc/ipsec.d/l2tp-psk.conf:

conn L2TP-PSK-NAT
        also=L2TP-PSK-noNAT

conn L2TP-PSK-noNAT
        authby=secret
        pfs=no
        auto=add
        keyingtries=3
        rekey=no
        ikelifetime=8h
        keylife=1h
        type=transport
        left=192.168.0.108
        leftnexthop=%defaultroute
        leftprotoport=17/1701
        right=%any
        rightprotoport=17/%any
        forceencaps=yes
        dpddelay=30
        dpdtimeout=120
        dpdaction=clear

conn passthrough-for-non-l2tp
        type=passthrough
        left=192.168.0.108
        leftnexthop=%defaultroute
        right=0.0.0.0
        rightsubnet=0.0.0.0/0
        auto=route