Backend Health shows unhealthy even with a single backend.

Hi,

Analysis:

• If a single FQDN BackendTarget in a single BackendPool resolves to “n” IPs, Then the total number of hosts in metrics becomes “n” i.e., Unhealthy hosts + Healthy hosts = n
• This “n” also includes the IPV6 addresses, even though App gateway is incapable of probing this IPV6 address (at the moment)
• Furthermore, BackendHealth section considers a backendTarget healthy only if all of these “n” IPs are reachable and working.
• So, if there were a IPV6 in that “n” addresses, the BackendHealth would simply show as Unhealthy only

Lab:

I have only one backend "www.example.com "

But we can see there are two hosts, one healthy and another unhealthy.

In my case,

• The Healthy one is the one which resolved to IPv4
• The Unhealthy one is the one which resolved to IPv6Analysis:
  • If a single FQDN BackendTarget in a single BackendPool resolves to “n” IPs, Then the total number of hosts in metrics becomes “n”
    i.e., Unhealthy hosts + Healthy hosts = n
  • This “n” also includes the IPV6 addresses, even though App gateway is incapable of probing this IPV6 address (at the moment)
  • Furthermore, BackendHealth section considers a backendTarget healthy only if all of these “n” IPs are reachable and working.
  • So, if there were a IPV6 in that “n” addresses, the BackendHealth would simply show as Unhealthy only