ISP Redundancy does not work on TMG servers. How to diagnose and fix.

If you are using on the server TMG several networks (in array config) that have Internet access may be through My_Net1 or My_Net2. Balancing configuration does not work. There are no errors, but traffic is using a Windows routing table and pays no attention to balancing settings. To diagnose the cause, you can run the following commands in Powershell:

$a1 = New-Object -comObject FPC.root
$a2 = $a1.arrays | where {$_.Name -eq "MyArray1"}
$a2.NetworkConfiguration.Networks | select Name,ISPRedundancyConfig

Name                                                        ISPRedundancyConfig
----                                                        -------------------
My_Net1
External                                                    System.__ComObject
Internal
Local Host
My_Net2
Quarantined VPN Clients
VPN Clients

If you attempt to apply the settings on the network balancing My_Net1 and My_Net2 not lead to success.

Thus, balancing is only possible on the network of "External".  If you want ISP Redundancy you need to remove the My_Net1 and My_Net2 of the array configuration.