IPv4 Fallback for IPv6 with Proxy in Standard Mode (Happy Eyeballs)
If a webserver is resolvable in DNS with both IPv4 and IPv6 addresses (A and AAAA Records) the UTM Proxy will prioritize IPv6, which is ok.
If the server is not reachable on IPv6 no fallback to IPv4 happens if the proxy is running in Standard mode.
The provided workarounds are:
1 -disable IPv6 on the ASG
=> Seriously, disable IPv6 in 2019 ?
2 -add a DNS static entry for every affected site with only an IPv4 record
=> Definitely not starting to statically add internet hosts...
3 -use HTTP proxy transparent mode instead
=> well yeah, but want if you don't want to...
Here is what I suggest: Implemented Happy Eyeballs into the proxy!
Like squid did in Aug 2012.