Zone Transfer Ports Required

If you see TCP port 53 in use it could tell you that someone is doing a zone transfer.

Zone transfer ports required. You have the ability to select one of three options. Well something that I recently learned was that DNS servers also use TCP port 53 to do zone transfers axfrs. An interesting fact about DNS zone transfers is that they usually rely on TCP port 53 instead of UDP port 53.

Zone transfers take place over TCP port 53 and in order to prevent our DNS servers from divulging critical information to attackers TCP port 53 is typically blocked. This is required to raise a firewall request in our environment. 5252017 You can specify a source port number for notify messages to ensure the firewall allows the zone transfer request from the secondary server to the primary server.

Zone transfers synchronize primary and secondary DNS server zones. To dump all available records assuming zone transfers are enabled issue the following commands. If dns1 is not authoritative for the domain.

Of a zone and secondary DNS servers keep copies of the zone for redundancy. DNS zones must remain updated on primary and secondary servers. When changes are made to zone data on the primary DNS server these changes must be distributed to the secondary DNS servers for the zone.

Dig ging DNS with a Zone Transfer. A master DNS server is the source of the zone information during a transfer. This is needed for redundancy.

To actually complete a zone transfer on a vulnerable DNS server you could issue these commands. Sign in to download full-size image. Usually a zone transfer is a normal operation between primary and secondary DNS servers in order to synchronise the records for a domain.