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Ross Chandler
In my experience the problems are overwhelmingly CPE and to a lesser extent client host related. IPv6 in the core network part was straightforward as dual-stack was integrated into BAU and it works very well: IXPs/PNIs/Transit links, links to content caches, DNS resolvers, L2 access nodes, and BNGs. Issues I've seen with CPE and the client OSes connected to them include: IPv6 firewall with memory leak that blocks all IPv6 traffic forwarding Router Advertisement on CPE LAN of IPv6 /64 from the ISP DHCPv6-PD without creation of default IPv6 route out WAN link. Router Advertisement of old /64 no longer delegated by ISP. IPv6 DNS proxy responding to MS Windows host clients but not other clients (due to a difference in NDP NA message ICMPv6 options). Router Advertisements on WiFi being missed by clients. Battery powered wifi clients disabling their own IPv6 access, e.g. due to sleeping or "smart" network switching. When the CPE is good it works great.