AXFR (Authoritative Zone Transfer) is a type of DNS (Domain Name System) transaction used to replicate the DNS records from a primary DNS server to a secondary DNS server. It ensures that the secondary server has an up-to-date copy of the DNS records, which is crucial for redundancy and load balancing.

Here are the key points about AXFR:

  1. Purpose: AXFR is used for full zone transfers, where the entire zone file is copied from the primary server to the secondary server.
  2. Mechanism: When a secondary server needs to update its copy of the DNS records, it sends an AXFR request to the primary server. The primary server then sends back the entire zone file.
  3. Primary and Secondary Servers: The primary DNS server holds the original copy of the DNS zone data, while secondary servers hold replicas. AXFR helps keep these replicas synchronized.
  4. Security: AXFR transactions can be sensitive since they involve transferring potentially large amounts of DNS data. To secure AXFR, DNS administrators can use methods such as IP address whitelisting, TSIG (Transaction SIGnatures) for authenticating the servers, and access control lists (ACLs).
  5. Efficiency: While AXFR transfers the entire zone file, there’s also IXFR (Incremental Zone Transfer), which transfers only the changes made to the zone since the last transfer. IXFR is more efficient for zones that change frequently.
  6. Use Case: AXFR is typically used in environments where DNS zones do not change very often or in initial setups when the secondary server needs a complete copy of the zone data.
  7. Configuration: DNS software like BIND, Microsoft DNS, and others allow configuration of AXFR. Administrators can specify which secondary servers are authorized to request AXFRs from the primary server.

Understanding AXFR is crucial for DNS administrators managing distributed DNS infrastructures, ensuring high availability, and maintaining consistent DNS records across multiple servers.

The other alternative to manage records in both Primary and Secondary DNS is MySQL replication. Here you can find step by step guide to replication MySQL server.

What is AXFR in DNS?

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