An AnyCast address is a special address that more than one host may have assigned to it, packets are routed to the closest host. Should that host be down, then it'll go to some other host etc. Great for services like DNS.
Anyone got any links for people doing AnyCast?
18.104.22.168 is the anycast address for a v6tov4 gateway (well, actually the reverse, the v4tov6 side of it...) See RFC:3068