* Renumbering. Service providers may change the delegated prefixes given to a subscriber during the lifetime of the home router. There are several options for renumbering a home router. One option is to use DHCPv6 Reconfigure/Reply. Another is to use DHCPv6 Renew/Reply with lifetimes that timeout the old prefix, while simultaneously supplying a new prefix. When these methods are used to renumber a home router, the LAN interface transmits a Router Advertisement setting the preferred and valid lifetimes of the old prefix to zero and lifetimes of the new prefix to non-zero. IPv6 devices connected to the LAN interface update their addresses to continuously communicate to the global Internet.
IPv6 devices on a LAN that have ongoing connections through the home router may try to continue using the old address that is deprecated to complete the communication. The behavior observed at the test event was that in these scenarios, ongoing connections were dropped with no notification to the host. According to 6204bis, a home router must transmit an ICMPv6 Destination Unreachable with a code 5 (Source address failed ingress/egress policy) to the host in question. If an IPv6 device receives this error message it has the ability to terminate the ongoing connection immediately and retry using the new prefix, thus improving the overall home user experience.
* No Default Route. When a route is no longer available on the home router's WAN interface, the router must transmit a Router Advertisement with a router lifetime of zero to the LAN interface. This advertises the inability for IPv6 devices to use the home router as a valid route to the global Internet. During initialization, 20% of the home routers were unable to transmit Router Advertisements until they received a Router Advertisement on the WAN interface with a valid router lifetime. Thus, if a router lifetime was set to a large value on the home router's LAN interface, and the router was rebooted, the IPv6 devices on the LAN interface would not realize the default route was no longer valid until the devices received a new Router Advertisement. Adversely, the home router would transmit a new Router Advertisement with a default lifetime of zero only when the router lifetime expired.
Two implementations at the test event demonstrated a new side effect of transmitting a DHCPv6 Release message for all IA_NAs and IA_PDs when a Router Advertisement with a router lifetime of zero was received on the WAN interface. This caused the loss of all global addresses for LAN IPv6 devices. The home routers would wait to restart the DHCPv6 discovery process until a Router Advertisement with a valid default router lifetime was received on the WAN interface. IETF 6204bis requires that a home router initiate DHCPv6 prefix delegation regardless of the content of the Router Advertisement, M or O flag state. During the event, both of the participants adjusted their implementations to continue DHCPv6 when a Router Advertisement was received with a router lifetime of zero on the WAN interface.
* Forwarding before Address Acquisition. During the test event a problem was encountered with IPv6 devices on separate LANs communicating after a home router is rebooted. After a reboot, there is a time period when a home router receives a Router Advertisement containing a valid router lifetime but the router has not yet received a delegated prefix through the DHCPv6 protocol. During this period it was observed that home routers were transmitting packets that were previously routed between the LAN to the WAN. This caused the edge router (ISP router) to forward the packet back to the home router causing a loop of packets in the network.