Ipv6 Anycast Addresses
A new address type made specifically for IPҢ is called the Anycast Address. These IPҢ addresses are global addresses, these addresses can be assigned to more than one interface unlike a IpҢ unicast address. Anycast is designed to send a packet to the nearest interface that is apart of that anycast group.
The sender creates a packet and forwards the packet to the anycast address as the destination address which goes to the nearest router. The nearest router or interface is found by using the metric of a routing protocol currently running on the network. However in a LAN setting the nearest interface is found depending on the order the neighbors were learned. The anycast packet in a LAN setting forwards the packet to the neighbor it learned about first. Anycast was first proposed in 1993 but even to this data there isn′t much usage as of yet. There are actually only a few anycast addresses currently assigned!
The source sending the anycast packet can use the address to control the paths that traffic flows. For example, when a customer has multiple connections to multiple IP’s using BGP. The customer can create a different anycast address for each ISP, and then configure the same address on the closest router to that specific ISP. Therefore the routers along the source’s path to the ISP can determine the shortest route based on the IPҢ anycast address. Which then forwards the packet based on the routers closest anycast address link. Another example would be on a LAN link. All the routers on the same LAN can have the same IPҢ address so that distant devices only need to identify the anycast address.
