DNS/DHCP Server Crossover High Availability (xHA) provides disaster recovery through the use of redundant appliances: xHA makes two DNS/DHCP Server appliances function as a single appliance.
If one of the appliances fails for any reason, the other takes its place and continues providing services. The pair appears as a single server for DNS queries because both servers share an IP address. Each server in the pair has its own IP addresses for management through Address Manager. For details about xHA, please refer to Address Manager Administration Guide.