Specifying DNS Servers

AsyncOS can use the Internet root DNS servers, your own DNS servers, or the Internet root DNS servers and authoritative DNS servers that you specify. When using the Internet root servers, you may specify alternate servers to use for specific domains. Because an alternate DNS server applies to a single domain, it must be authoritative (provide definitive DNS records) for that domain.

AsyncOS supports “splitting” DNS servers when not using the Internet’s DNS servers. If you are using your own internal server, you can also specify exception domains and associated DNS servers.

When setting up “split DNS,” you should set up the in-addr.arpa (PTR) entries as well. For example, if you want to redirect “.eng” queries to the nameserver 1.2.3.4 and all the .eng entries are in the 172.16 network, then you should specify “eng,16.172.in-addr.arpa” as the domains in the split DNS configuration.