Hello Michiel!   
      
   Oct 03 10:15 2015, Michiel van der Vlist wrote to Paul Hayton:   
      
    MvdV> It may be the privacy extensions. Windows has it enabled by    
    MvdV> default. It means an interface gets at least two public IPv6    
    MvdV> addresses. The one is assigned by SLAAC or DHCP6 and it is the one    
    MvdV> that should be used for incoming connection. The other has its    
    MvdV> suffix assigned random and it is renewed every 24 hours. That is    
    MvdV> the one used for outgoing connections.   
      
   On linux you can change the lifetime and the time the address remains usable   
   after a new one is created, i.e. the time until it's discarded completely.   
      
   For en/disabling PE and changing the timers you have to simply write the   
   values to:   
   /proc/sys/net/ipv6/conf/eth0/use_tempaddr  (0: off / 1: assign / 2: prefer)    
   /proc/sys/net/ipv6/conf/eth0/temp_valid_lft (time in seconds)   
   /proc/sys/net/ipv6/conf/eth0/temp_prefered_lft (time in seconds)   
      
    MvdV> Privacy extensions do not make much sense on a fixed connection    
    MvdV> since the prfix does not change and it makes even less sense if the    
    MvdV> host accepts incoming connections and advertises it by en entry in    
    MvdV> the DNS.   
      
   I agree, that PE is nonsense for a server. Also SLAAC/DHCPv6 aren't helpful    
   in this case. But it's not generally a bad idea to enable PE for PCs with a   
   static prefix. SLAAC assigned addresses are based on the NIC's MAC address. If   
   you want to make life a little bit harder for all those trackers, PE comes in   
   handy. And DNS is no real issue since most are used to DynDNS for quite a   
   while. With SLAAC you would have to manage DNS dynamically anyway, because a   
   new NIC (replacement for a broken one, new mainboard) will cause a new IPv6   
   address. You don't want this to happen for a server.     
      
   My IPv6 prefix is valid for up to 6 months, if the DSL connection stays up and   
   running all the time. But it doesn't due to the telco's maintenance windows   
   and maybe some power outage and what have you. So I had to set up DynDNS   
   anyway. It doesn't matter for me if the address changes every 24h or every few   
   weeks/months, it's monitored and DNS will be updated if necessary.   
      
   Regards,   
   Markus   
      
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