I am using PPPoE and DHCPv6 client to get an /56 (dynamic) from my ISP. The client creates a dynamic pool with prefix length /64.
I have configured an IPv6 address as “::/64”, which is automatically filled when I receive a prefix.
I don’t use DHCPv6 server, just ND/Interfaces so my devices get an IPv6 address via SLAAC.
I have noticed that if the prefix changes for a reason (uplink disconnection) or if the prefix lifetime is over, my clients don’t “forget” their already owned IPv6 addresses. So after some days, I see the following:
This happens to all my devices. I am sure I’m missing something on my IPv6 configuratuion on Routerboard.
This is a normal behavior and is designed to protect your privacy online. It’s a function of Windows (and other operating systems) and is not due to a setting on the MIkroTik.
The temporary addresses will eventually expire and are called “privacy extensions”
I wonder if there’s a way, when my router loses a dynamic prefix before expiration (e.g due to PPP disconnection), to inform all clients to stop using any addresses on that prefix.
The mechanizm is that devices receive new prefix (after a few tens of seconds, depending on RA periodicity) and start using new addresses for new connections. Existing connections in theory keep using old addresses but in practice break even before getting new address because routers on the way discard packets (or mis-route them). So at the end devices start using new prefix pretty quickly even without explicit prefix depreciation notification.
You can shorten lifetime, setting it to fraction of observed prefix validity as delivered by ISP (one quarter or one third should be fine, don’t nake it shorter than a few minutes not to cause IPv6 address outages).
But I don’t think it will help much. I don’t have first hand experience, all “my” sites either have static prefix or ISPs don’t bother changing it if site GW router is alive, but I guess IPv6 downtime will be in order of a minute (give or take) if prefix changes in any case.
