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   Hello Tim,   
      
   On Thursday March 10 2022 23:01, you wrote to me:   
      
    TS>>> While this would be the easiest to do (essentially delete a few   
    TS>>> lines of code),   
      
    MvdV>> So what is stopping you?   
      
    TS> Did it for testing.   
      
   And?   
      
    TS>>>  I would like to know where that is supposed to be defined.   
      
    MvdV>> It is in line with the general principle of "do not reinvent   
    MvdV>> the wheel". If the OS can take care of it, let the OS do it.   
      
    TS> Well, as long as I have no indication that the result order of the OS   
    TS> returned has any semantics at all (rather than beeing random) relying   
    TS> on itmay worse than making an enducated guess. If you know some place   
    TS> that defines that the order is actually a suggestion on priorities   
    TS> that would be fine.   
      
   Oh, there is logic behind the choices made by the WIndows OS. It certainly   
   isn't random. Wilfred already gave you some links. Let me add this one:   
      
   https://techjourney.net/how-to-change-ip-address-prefix-policies   
   precedence-to-use-ipv4-o ver-ipv6-address/   
      
   It tells you how to play around with the netsh command to alter the default   
   IPv6 prefernces. Try something like this:   
      
   D:\FIDO>netsh int ipv6 show prefixpolicy   
   Der aktive Status wird abgefragt...   
      
   Vorg„nger   Label  Pr„fix   
   ----------  -----  --------------------------------   
            5      5  2001::/32   
           10      4  ::ffff:0:0/96   
           20      3  ::/96   
           30      2  2002::/16   
           40      1  ::/0   
           50      0  ::1/128   
      
   It shows the order for choosing when more than one choice can be made. The   
   highest value in the first colum comes first. ::ffff:0:0/96 is the IPv4 mapped   
   space. Note that 2001::/16 (6to4 tunnel adresses have a lower priority than   
   IPv4. So by default Windows selects IPv4 if the IPv6 address is a 6to4 tunnel   
   address.   
      
   You can play around with the values with:   
      
   netsh int ipv6 set prefixpolicy address preference label   
      
   For the complete syntax:   
      
   netsh int ipv6 set prefixpolicy ?   
      
   Hope this helps.   
      
   Cheers, Michiel   
      
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