On my network, tcpdump suggests this happened in response to the router sending an IPv6 router advertisement every few minutes, and was stopped after:
ip6tables -A INPUT -p icmpv6 --icmpv6-type router-advertisement -j DROP
On my network, tcpdump suggests this happened in response to the router sending an IPv6 router advertisement every few minutes, and was stopped after:
ip6tables -A INPUT -p icmpv6 --icmpv6-type router- advertisement -j DROP