I have made a single certificate for VPN access with ikev2. In 2 days I got the id. From event 20209, although I did not try to connect. The certificate is still with me and no one else has access to it. But the event viewer claims that
A connection between the VPN server and the VPN client 22.214.171.124 has been established, but the VPN connection cannot be completed. The most common cause for this is that a firewall or router between the VPN server and the VPN client is not configured to allow Generic Routing Encapsulation (GRE) packets (protocol 47).
This IP has been dialed for BruteForce VPN attempts on many sites.
I just want to know how they managed to connect without a certificate.