GTM: SERVFAIL when looking up Internet hostnames

That's an interesting approach. Never see this recommended by F5 but something I'll consider. DNS express should offer better performance vs. the standard BIND backend.

Anyway, I was able to figure out the problem - I needed to have an "allow-recursion" statement in the configuration. This can be done in the options of the named.conf file, or within the applicable view, i.e.

options {
    recursion yes;
}
acl "rfc_1918" {
    10.0.0.0/8;
    172.16.0.0/12;
    192.168.0.0/16;
};
view "internal" {
    allow-recursion {
        "rfc_1918";
    };
};