Load balancing DNS is not so much different from any regular service, and might also be needed to configure in case of setting up GSLB using NetScaler as a DNS Proxy.
There are, however, some settings that we need to be aware of. First, when we are setting up our services and need to bind a monitor to our backend DNS servers, we should create a custom monitor for DNS and enter a custom query to check if the DNS servers respond with the correct address. A custom monitor for DNS may look like the one in the following screenshot, where NetScaler will query the backend DNS server for an address; the IP addresses that return should match the values as shown in this screenshot:
Second, when we set up the virtual load balancing server, we have some different options available for DNS under the basic settings of the vServer, which are as follows:
- DNS64: DNS64 needs to be enabled if you are having IPv6 clients that need to communicate with backend servers running IPv4. Also, this feature must be used in conjunction with NAT64.
- Recursion Available: This option is enabled when the backend servers that NetScaler is load balancing are set as recursive, which allows them to act as end resolvers for a DNS query.
- Bypass AAAA requests: If this option and DNS64 are enabled, NetScaler will not forward AAAA requests to the backend servers.