AXFR

DNS zone transfer, also sometimes known by its (most common) opcode mnemonic AXFR, is a type of DNS transaction, which usually happens to transfer the DNS zone from the master DNS server to the slave DNS server. It is one of the many mechanisms available for administrators to employ for replicating the databases (usually on of the DNS zones) containing the DNS data across a set of DNS servers. Zone transfer comes in two flavors: full (opcode AXFR) and incremental (IXFR). Nearly universal at one time, it is now getting less popular, in favor of the use of other database replication mechanisms that modern DNS server packages provide.