IPv6 Re-connections

[Ardua]

Checking my router log which I do about once a week, I noticed that my connection has been solid since 4 Jan (when I upgraded the router firmware) but that the log is showing a 2 minute 'internet lost' yesterday afternoon. As there was no loss of DSL or re-training, I assume that this was something external to the router. I also noticed that the router log shows that my IPv6/48 prefix is updating every 2 to 4 days. The IPv6/ef connection is not affected nor is the IPv4. I would be interested to know why this is the case?