Russel,
the problem has been solved now! The final thing missing was just a check in a checkbox.
Below a comprehensive explanation that may help others.
We basically did what you proposed:
We sent a ping from one of the DA-Clients to the TS-Farm members. Since we got replies, we knew that IPv6 communication generally is okay. The answer received was an IPv6. In this scenario we had not yet given any IPv6 to the farm-members! Thus we knew it must
be comming from the DA DNS-Proxy. There are a number of DA-GPOs and one of them is dictating the net portion of the IPv6 to be used in DA-communication, appended by a hex-translation of the target computers IPv4. Therefore the DA DNS-Proxy is taking the GPO-set
IPv6-value, adds the IPv4 in hex and sends it back as an ICMP echo.
With this in place and working correctly one can ping any domain host from any DA-Client. This is configured when initially setting up DA and is handled by the wizzard. Once DA is installed this should all be in place without extra user interaction.
We then took those IPv6 answeres and turned them into fixed IPv6es of the farm-members (each member its own IPv6). So far so good, but this is where it still did not work. Evaluation of the Connection Broker log showed that the redirect reply still included
only the IPv4 of the target farm-member. With that (after a short while) we realized that one has to set a
check in the Connection Brokers Settings, so that the IPv6 LAN-Connection will be used for redirects as well and not only the IPv4 LAN-connection..... How stupid is that? :-)
But as we all know - in dealing with server configuration - you should always "know before you go". But even though you may think you do, when finally arriving you know you didn't.... And that's what we call experinece.
Thanks to Russel for your interest and help.
Brgds Ralf