In
IKEv2 only mode
, if the peer does not
support IKEv2, the firewall aborts the connection. In
IKEv2
preferred mode
, if the peer does not support IKEv2, the
firewall falls back to IKEv1. However, the VPN must negotiate IKEv2 to use
the post-quantum VPN features, so if the firewall falls back to IKEv1, those
features are not available.