Just a few days ago, HE.NET Tunnelbroker's French server experienced an outage. When I configured my Kimsufi server, I assigned the native IPv6 addresses to ESXi for exclusive use (as described in this article ), leaving pfSense with only native IPv4 and obtaining IPv6 addresses through Tunnelbroker. Consequently, all virtual machines on the server lost IPv6 connectivity. More critically, since I had set up a NAT64 service on the server following this article , and configured pfSense's DNS resolution to prioritize Google DNS's NAT64 servers (2001:4860:4860::64 and 2001:4860:4860::6464) with IPv4 as fallback, DNS resolution almost completely failed due to the IPv6 outage combined with pfSense's long DNS timeout settings. To prevent such cascading failures from recurring,...