http://gpp6nwvsps43b3mfacsh433uroo6uyjvvpr6tgj4jh4n5ngxt7rqbvid.onion/posts/l2tp-ipsec-psk-libreswan.html
Configure Libreswan Create a new file for L2TP/IPsec connections with a preshared key: vi /etc/ipsec.d/l2tp-ipsec-psk.conf Insert lines specifying a configuration like this: conn ikev1
authby=secret
pfs=no
auto=add
rekey=no
left=%defaultroute
right=%any
ikev2=never
ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1,aes256-sha2;modp1024
esp=aes256-sha2_512,aes128-sha2_512,aes256-sha1,aes128-sha1;modp1024
type=transport
leftprotoport=17/1701
...