Specific IPs not pingable via IPv6

[computeralex92]

Hello,

after the upgrade to 20.7 I have a very special problem:
I normally use the IPv4 and IPv6 addresses of my external DNS resolvers as Health Endpoints for the Gateway monitoring.
After the upgrade, the IPv6 address of my resolver is not pingable anymore from the firewall.
The strange thing is: The IP is still accessable via ICMP from my client or any other computer, only the firewall is not able to reach the DNS server via IPv6.
DNS requests are no problem; only ICMP is affected.

Do anyone have a idea for this issue?

Thanks,

Alex