Installing and Administering Internet Services

Chapter 3 115
Configuring and Administering the BIND Name Service
Troubleshooting the BIND Name Server
SOA queries are queries for the start of authority records. These
queries are most often made by secondary servers over a stream
connection to check if their domain data is current.
PTR queries are queries for the domain name for a host address. The
gethostbyaddr library routine generates these queries.
MX queries are mail exchanger queries made by sendmail during the
delivery of electronic mail.
AXFR queries is the number of zone transfers done by secondary
servers. A secondary server first makes an SOA query and will follow that
with an AXFR query if new domain data should be transferred.
ANY queries are queries for any data associated with the domain
name. Some versions of sendmail make queries for ANY data during
name canonicalization from $[ $] tokens in
/var/adm/sendmail/sendmail.cf.