IKEv2 vs OpenVPN - Explain the difference.

IKEv2 vs OpenVPN IPSEC needs more time to negotiate the tunnel; OpenVPN uses strong ciphers and TLS ; (at the present moment it is considered to be the strongest encryption); Single and configurable port for OpenVPN and option to choose between UDP or TCP.

Multiple ports/protocols for IPSEC; IPSEC can not handle NAT. (needs public IP address on both sides Otherwise), L2TP required. OpenVPN can easily act over NAT;  OpenVPN can have multiple instances and IPSEC can be established only for a single ip addresses pair.

OpenVPN can be used both as an L2 and L3 class.

I am using both IPSEC and OpenVPN infrastructure connections, but OpenVPN shows much better stability and flexibility. IKE itself is just a key exchange protocol, providing secure session key negotiation. It works together with encryption and authentication modules. So, IKE itself just provides sessions with secure keys. Moreover, it was developed in 2005. It is oftenly being used together with ESP and AH protocols.

OpenVPN is an open source project that is growing fast and being developed also by the community. Mobile devices have native SSL/TLS support and OpenVPN implementation is preferable for Mobile usage for following reasons:

Mobile internet does not provide fixed IP addresses that is a problem for IPSEC, having IKEv2 - need to use dDNS or buy a public IP address. L2TP that provides transport level for IPSEC uses fixed port and can be blocked by some firewalls; OpenVPN is easy to configure and flexible in its usage - modern versions (higher than 2.2) use TLSv1.X. It is possible to use multi-level authentication with client certificates, passwords and secure keys if needed. Server can be easily set up to listen any port; Mobile Applications for OpenVPN exist for Android and iOS - it has limitations only with Windows based systems.

OpenVPN is considered to be slower than IPSEC. However, OpenVPN is not sensitive to hosts time sync, public IP existence needs only one free to choose port.