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 .