TZUTC: 1100   
   MSGID: 1643.fido-ipv6@3:633/410 24504bce   
   PID: Synchronet 3.17c-Linux  Nov  3 2019 GCC 4.6.3   
   TID: SBBSecho 3.10-Linux r3.146 Nov  3 2019 GCC 4.6.3   
   CHRS: ASCII 1   
   Had an interesting issue in recent weeks, which affected IPv6 connectivity on   
   my BBSs.  For almost 10 years, the connection has been trouble free, except for   
   some issues when moving house in 2013.  In 2017, upgrading to the NBN (runs   
   VDSL here) led to a vast improvement in service.  Most importantly, since 2013,   
   when we moved to this address, my LAN IPv6 prefix hadn't change.  The LAN used   
   the first /64 from my /56, with the WAN interface getting an address from   
   another /54.   
      
   Sometime in the near past, ,y LAN prefix changed to the second /64 in my range,   
   which baffled ne.  Rebooting the router sometimes got me back to the first /64,   
   but at the time I didn't know what was going on.  All I knew is everything   
   worked again.  When IPv6 failed within 12 hours of a reboot, I took a closer   
   look and discovered that my prefix had changed to the second /64 in my range.    
   So I reconfigured the BBSs and other hosts that require static addresses, as   
   well as their corresponding DNS entries, and all was well.  Next morning, the   
   LAN prefix had reverted to the first /64!   
      
   At this point, I considered phoning the ISP, but it was getting a bit late, so   
   I tinkered.  Went into the router and found there were 3 (relevant to me)   
   options for obtaining an IPv6 address.  The first (and the option I was   
   originally set to) looks for router adverisements first, then tries DHCPv6, and   
   finally assigns an address from the first subnet if all else fails.  I figured   
   there's something going on between router advertisements and DHCPv6.   
      
   The second option tries only DHCPv6.  I didn't try this one.   
      
   The third option uses only router advertisements, or assigning an address from   
   the first /64 if that fails.  I switched to this option.   
      
   Since making the switch, my LAN prefix seems stable (touch wood) on the second   
   /64 of my range.  Time will tell, but hopefully I've stabilised things on the   
   new address range.  Looks like my router started using DHCPv6 only   
   intermittently, and DHCPv6 assigns a different WAN address.  I'm only guessing,   
   as I can't see what's happening on the ISP side.  Maybe they're tweaking things   
   too.     
      
   99.9% of customers wouldn't notice this issue (and it never affected web   
   browsing and other client only activities on machines using SLAAC).  I only   
   noticed and have issues, because I have a lot of things listening on fixed IPs.   
      
      
   ... Hangnail: Coat hook.   
   === MultiMail/Win v0.51   
   --- SBBSecho 3.10-Linux   
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