L2TP VPN client on Linux Debian

l2tpclient.sh

# Requirements
# debian/ubuntu

apt-get -y update && apt-get -y upgrade
apt-get -y install strongswan xl2tpd libstrongswan-standard-plugins libstrongswan-extra-plugins

VPN_SERVER_IP=''
VPN_IPSEC_PSK='y'
VPN_USER=''
VPN_PASSWORD=''

cat > /etc/ipsec.conf <<EOF
config setup
conn %default
  ikelifetime=60m
  keylife=20m
  rekeymargin=3m
  keyingtries=1
  keyexchange=ikev1
  authby=secret

conn VPN1
  keyexchange=ikev1
  left=%defaultroute
  auto=add
  authby=secret
  type=transport
  leftprotoport=17/1701
  rightprotoport=17/1701
  right=$VPN_SERVER_IP
EOF

cat > /etc/ipsec.secrets <<EOF
: PSK "$VPN_IPSEC_PSK"
EOF

chmod 600 /etc/ipsec.secrets

cat > /etc/xl2tpd/xl2tpd.conf <<EOF
[lac VPN1]
lns = $VPN_SERVER_IP
ppp debug = yes
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-chap
noccp
noauth
mtu 1280
mru 1280
noipdefault
defaultroute
usepeerdns
connect-delay 5000
name $VPN_USER
password $VPN_PASSWORD
EOF

chmod 600 /etc/ppp/options.l2tpd.client

service strongswan restart
service xl2tpd restart

cat > /usr/local/bin/start-vpn <<EOF
#!/bin/bash

(service strongswan start ;
sleep 2 ;
service xl2tpd start) && (

ipsec up VPN1
echo "c VPN1" > /var/run/xl2tpd/l2tp-control
sleep 5
#ip route add 10.0.0.0/24 dev ppp0
)
EOF
chmod +x /usr/local/bin/start-vpn

cat > /usr/local/bin/stop-vpn <<EOF
#!/bin/bash

(echo "d myvpn" > /var/run/xl2tpd/l2tp-control
ipsec down myvpn) && (
service xl2tpd stop ;
service strongswan stop)
EOF
chmod +x /usr/local/bin/stop-vpn

echo "To start VPN type: start-vpn"
echo "To stop VPN type: stop-vpn"

Thanks for the script!

After adding the fixes for Mikrotik suggested by agenovez and updated the start and stop script to use systemctl it works great!

New start script:

#!/bin/bash
(
  systemctl start strongswan-starter.service
  sleep 2
  systemctl start xl2tpd.service
) && (
  ipsec up VPN1
  echo "c VPN1" > /var/run/xl2tpd/l2tp-control
  sleep 5
  #ip route add 10.0.0.0/24 dev ppp0
)

New stop script:

#!/bin/bash
(
  echo "d VPN1" > /var/run/xl2tpd/l2tp-control
  ipsec down VPN1
) && (
  systemctl stop xl2tpd.service
  systemctl stop strongswan-starter.service
)

Thank you a ton for this gist.

I had to tweak it a bit to get it to work with my setup (Ubuntu client & Ubiquiti UDM server)
I've posted the gist here:
https://gist.github.com/btc100k/8a075e2855298aa359d14b1688aa2f04

The big diffs (IIRC) were in the pppoptfile, and in creating/removing the route when starting/stopping vpn.