zerotier

ZeroTier’s software is open source and free to use for most purposes including personal useinternal use within a business or academic institution, and evaluation for uses that require commercial licensing.

https://www.zerotier.com/pricing/

ON-PREMISES SITE 2 SITE VPN WITH AZURE USING TOMATO SHIBBY MOD (ENTWARE-NG AND STRONGSWAN SETUP) – PART 1

On-Premises Site 2 Site VPN with Azure using Tomato Shibby Mod (Entware-ng and Strongswan setup) – part 1

 

On-Premises Site 2 Site VPN with Azure using Tomato Shibby Mod (Entware-ng and Strongswan setup) – part 2

Step-By-Step: Configuring a site-to-site VPN Gateway between Azure and On-Premise

https://blogs.technet.microsoft.com/canitpro/2017/06/28/step-by-step-configuring-a-site-to-site-vpn-gateway-between-azure-and-on-premise/