Anycast is a routing scheme that provides faster response times by routing requests to the nearest server in a group.
It's especially useful for large distributed DNS applications that handle a high volume of requests. For example, DNS root servers use Anycast to distribute their service throughout the world. Although most root servers are nominally located in the United States and share a U.S. IP address, most of the physical machines are located elsewhere.
Anycast assigns one IP address to multiple servers that provide the same service. A client asking for that specific IP address is directed to the geographically closest server using Border Gateway Protocol (BGP), Open Shorter Path First (OSPF), or Routing Information Protocol (RIP). BlueCat DNS/DHCP Servers use Quagga to participate in Anycast routing for DNS using one of the aforementioned protocols. For more information about Quagga, refer to Quagga documentation at http://www.quagga.net/docs.php.
You can enable/disable Anycast service and configure BGP, OSPF, or RIP on DNS/DHCP Server appliances from the Address Manager user interface.