IPsec/IKEv2/EAP-TLS VPN - IPv6 traffic not flowing
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I have configured an IPsec/IKEv2/EAP-TLS VPN following the 'recipe' in the pfSense documentation. I obviously made some minor changes such as using my own IPv4 subnet for client addresses. In addition I also configured the VPN tunnel as dual stack and configured a suitable client IPv6 subnet from which to assign addresses, configured IPv6 DNS servers etc.
My client is a macOS system (Big Sur 11.5.2).
The VPN connection works very well for IPv4; no issues at all apart from some additional DNS resolver setup needed on the macOS side.
The same unfortunately is not true for IPv6. The client gets assigned a valid IPv6 address from the designated subnet, so that part is working, but no IPv6 traffic flows at all. I cannot even ping IPv6 addresses in the remote LAN (works fine for IPv4). I have checked the firewall rules and nothing should be impeding the traffic flow, it just isn't working.
Does anyone know for sure if the macOS IPsec/IKE client fully supports IPv6? Or any suggestions on any setup things I could check or additional tests I could run? I can live with IPv4 connectivity but since the target network and its hosts is fully dual stack it would be nice to have IPv6 running over the VPN as well.