A system that determines if a DNS server suffers from a particular known functional limitation. During operation, the system sends an exploratory query to the DNS server, wherein the exploratory query is specially constructed so as to detect the existence of a functional limitation in the DNS server without causing the DNS server to fail. Next, the system receives an answer to the exploratory query from the DNS server. If the DNS server gives an incorrect response, the system can take actions as may be desired for the implementation. For example, the system may display a message identifying the functional limitation, or the system may establish a mode of operation where it avoids performing those types of DNS queries known to present a risk of crashing the particular Internet gateway.