Hello, and welcome.
OpenVPN is one of the wide variety of SSL-based VPN implementations. OpenVPN differs from most of the other SSL-based VPNs in three key ways:
- It is free and open source.
- It is portable, and is available for many OSes.
- It can be deployed through many different network configurations, as it tunnels within UDP or TCP.
OpenVPN is available on OpenBSD, as a third party port/package.
Unfortunately I have not used OpenVPN in about 20 years, so I am unable to assist with your implementation problem.
You're asking about
isakmpd.conf(5). That is a configuration file for
isakmpd(8), which is used with IPSec, an entirely different VPN technology than OpenVPN. IPSec has its own protocols, and an introduction can be found in
ipsec(4).