Ubuntu

sudo apt-get install strongswan xl2tpd ppp

/etc/ipsec.conf

conn L2TP-PSK

type=transport

authby=psk

keyexchange=ikev1

keyingtries=3

rekey=no

left=192.168.5.105 use local ip

right=%any

auto=add

/etc/ipsec.secrets

: PSK "12345678"

/etc/xl2tpd/xl2tpd.conf

[lns default] ; Our fallthrough LNS definition

ip range = 192.168.2.2-192.168.2.20 ; * Allocate from this IP range

local ip = 192.168.2.1 ; * Our local IP to use