Servfail queries for named remote authoritative nameservers?

[Viktor Dukhovni via Unbound-users]

Is it possible to quickly SERVFAIL queries for data handled by a
particular set of remote nameservers?

I tried a combination of:

        local-data: "some-ns.example. IN A 127.0.0.1"
        do-not-query-address: 127.0.0.0/8

but I still see queries going to the underlying remote IPs, the
"local-data" setting does not appear to affect the infra-IP resolution
for the zones served by the server in question.

-- 
        Viktor.