Install an L2TP client in Ubuntu

install_l2tp.sh

#!/bin/sh

#usage: 
#		install_l2tp.sh <L2TP_SERVER> <SHARED_SECRET> <USERNAME> <PASSWORD>
set -e

L2TP_SERVER=${1}
SHARED_SECRET=${2}
USERNAME=${3}
PASSWORD=${4}

apt-get install openswan xl2tpd

echo "net.ipv4.ip_forward = 1" >>/etc/sysctl.conf
echo "net.ipv4.conf.all.accept_redirects = 0" >>/etc/sysctl.conf
echo "net.ipv4.conf.all.send_redirects = 0" >>/etc/sysctl.conf
echo "net.ipv4.conf.default.rp_filter = 0" >>/etc/sysctl.conf
echo "net.ipv4.conf.default.accept_source_route = 0" >>/etc/sysctl.conf
echo "net.ipv4.conf.default.send_redirects = 0" >>/etc/sysctl.conf
echo "net.ipv4.icmp_ignore_bogus_error_responses = 1" >>/etc/sysctl.conf

for vpn in /proc/sys/net/ipv4/conf/*; do echo 0 > $vpn/accept_redirects; echo 0 > $vpn/send_redirects; done
sysctl -p

cat > /etc/ipsec.conf << EOF
config setup
     virtual_private=%v4:10.0.0.0/8,%v4:192.168.0.0/16,%v4:172.16.0.0/12
     nat_traversal=yes
     protostack=netkey
     oe=off
     plutoopts="--interface=eth0"
conn L2TP-PSK
     authby=secret
     pfs=no
     auto=add
     keyingtries=3
     dpddelay=30
     dpdtimeout=120
     dpdaction=clear
     rekey=yes
     ikelifetime=8h
     keylife=1h
     type=transport
     left=%defaultroute
     leftnexthop=%defaultroute
     leftprotoport=17/1701
     right=${L2TP_SERVER}
     rightid=10.0.1.11
EOF

echo "0.0.0.0 ${L2TP_SERVER}: PSK \"${SHARED_SECRET}\"" >/var/lib/openswan/ipsec.secrets.inc

cat >/etc/xl2tpd/xl2tpd.conf << EOF
[lac vpn-connection]
lns = ${L2TP_SERVER}
pppoptfile = /etc/ppp/options.l2tpd.client
length bit = yes
EOF

cat >/etc/ppp/options.l2tpd.client << EOF
ipcp-accept-local
ipcp-accept-remote
refuse-eap
require-mschap-v2
noccp
noauth
idle 1800
mtu 1410
mru 1410
defaultroute
connect-delay 5000
name ${USERNAME} 
password ${PASSWORD}
EOF

mkdir -p /var/run/xl2tpd
touch /var/run/xl2tpd/l2tp-control

cat >> /etc/ppp/ip-up <<EOF
route add -net 10.0.1.0/24 dev \${PPP_IFACE}
route add -net 10.0.2.0/24 dev \${PPP_IFACE}
route add -net 10.0.3.0/24 dev \${PPP_IFACE}
route add -net 10.0.4.0/24 dev \${PPP_IFACE}
EOF

cat >/etc/rc.vpn.start << EOF
#!/bin/sh
service ipsec restart
service xl2tpd restart
ipsec auto --up L2TP-PSK
echo "c vpn-connection" > /var/run/xl2tpd/l2tp-control
EOF

cat >/etc/rc.vpn.stop << EOF
#!/bin/sh
service ipsec stop
service xl2tpd stop
EOF

chmod +x /etc/rc.vpn.start
chmod +x /etc/rc.vpn.stop

/etc/rc.vpn.start