This section describes how to add multiple IP service addresses or loopback addresses to the Service interface (by default, eth0) of your managed DNS/DHCP Server or xHA pair for load balancing of DNS services.
Additional DNS service addresses provide flexibility and centralized control when consolidating old DNS servers into one single server without disrupting any configurations that might be using the old IP addresses.
- You can add a maximum of 400 combined IPv4 and IPv6 addresses
- Additional IP addresses can be configured on any service interface, this includes the physical eth0 interface, including VLAN interfaces and bonding interfaces (bond0). For information on managing VLAN and bond interfaces, refer to VLAN tagging.
- Ensure that IP addresses are unique and don't conflict with IPs configured on other interfaces of the server or in your network.
- If you reset services when replacing a DNS/DHCP Server, the Interfaces/Additional IP Address service type will be disabled but won't remove IP addresses from the list.
There are a number of reasons that you might want to assign more than one service address to an interface on a DNS server:
- Migrating between DNS servers—As data is migrated from one DNS server to another, it might be necessary for a period of time to allow clients to contact the IP address of the old DNS server.
- Retiring a DNS server—Similarly, as you move to retire a DNS server for consolidation or other reasons, it might be difficult to know which clients are configured with the IP address of the old server. Adding the IP address of the old DNS server to the active DNS servers allows clients to continue to use the configured IP address without disruption on the network.
- Listening on Multiple Networks—By default, a BlueCat DNS server listens for
incoming DNS traffic on eth0 (or bond0 if eth0 and eth3 have been bonded together).
Typically, DNS clients located on different subnets make use of a routed network to
connect to a DNS server. In some environments however, networks may be segmented for
security or other reasons, and some subnets may not have a routable path to the DNS
server. In such cases, adding one or more service IP addresses to the BlueCat DNS server
allows it to listen on all necessary networks.Note: Customers running DHCP with multiple IP service addresses are advised that certain scenarios can impact DHCP service. For details, refer to DHCP with multiple IP service addresses.
In some environments, DNS servers are placed behind a load balancer group so that client requests will be sent to the closest DNS server. In order for a load balancer to be able to properly communicate with a DNS server, the IP address of the Load Balancer must be added as a loopback address on the DNS server.