Site To Site VPN

1. pfSense
2. RouterOS
3. Linux Strongswan

Tunnels

1. NetworkManager L2TP
2. xl2tpd
3. Connman
4. Systemd-networkd
5. Iproute2 GRE

Links

• https://www.strongswan.org/

• https://openswan.org/

• https://libreswan.org/

• https://www.freeswan.org/

• https://github.com/nm-l2tp/NetworkManager-l2tp

• https://manpages.debian.org/unstable/connman/connman-vpn-provider.config.5.en.html

• https://github.com/xelerance/xl2tpd

• https://github.com/systemd/systemd/pull/11908

• https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/securing_networks/configuring-a-vpn-with-ipsec_securing-networks

• https://www.kernel.org/doc/html/latest/networking/l2tp.html

• https://tldp.org/HOWTO/Leased-Line/pppd.html

• https://www.cisco.com/c/en/us/support/docs/ip/internet-key-exchange-ike/117258-config-l2l.html