 As the Router Advertisement is a key ICMPv6 message for configuring hosts, it is also an attractive tool to use for attacking hosts - or confusing hosts due to accidental configuration errors on hosts or routers [65]. An unwanted Router Advertisement on a Deploying IPv6 in 3GPP Networks link is referred to as a Rogue Router Advertisement. For example, a misconfigured host performing 'tethering' could be sending Rogue Router Advertisements advertising auto- matically generated Connection of IPv6 domains via IPv4 clouds (6to4) prefixes (6to4 is an IPv6 transition mechanism used for automated tunneling, see RFC 3056 [66]) to a network link that may or may not have any 'legitimate' IPv6 routers. In either case, hosts will receive the Rogue Router Advertisement from this misconfigured host, and statelessly configure IPv6 addresses based on the received prefix and other information. The misconfigured IPv6 address can cause hosts to initiate data sessions and transport data through the misconfigured host, thus causing various issues such as lack of connec- tivity altogether, low bandwidth, and longer than necessary latencies. An attacker sending Rogue Router Advertisements can initiate man-in-the-middle or denial-of-service attacks. The IETF has designed Secure Neighbor Discovery (SEND) to protect against such threats (see Section 3.4.9). However, unfortunately SEND is currently not deployed. For unmanaged nodes receiving Rogue Router Advertisements, there is very little they can do until SEND is perhaps supported one day. The nodes need to be able to hastily switch to use alternative routers and addresses (including IPv4 addresses) if addresses or routers first configured do not yield properly working connectivity (see also the Happy Eyeballs feature described in Section 3.9.4). Managed nodes could be provisioned with, for example, firewall rules allowing Router Advertisements only from whitelisted sources. For routers, IETF has defined tools in RFC 6105 that can be used to protect hosts. Effectively, managed layer 2 