What port does AXFR use?
TCP port 53
The life cycle of an AXFR connection An AXFR connection may appear, at first glance, to be a typical TCP client-server connection: the AXFR client connects to an AXFR server on TCP port 53, sends an AXFR request, receives an AXFR response with the requested zone data, and closes the connection.
What is AXFR protocol?
AXFR is a protocol for “zone transfers” for replication of DNS data across multiple DNS servers. Unlike normal DNS queries that require the user to know some DNS information ahead of time, AXFR queries reveal resource records including subdomain names [1] .
What is difference between AXFR and Ixfr?
The current full zone transfer mechanism (AXFR) is not an efficient means to propagate changes to a small part of a zone, as it transfers the entire zone file. Incremental transfer (IXFR) as proposed is a more efficient mechanism, as it transfers only the changed portion(s) of a zone.
Why is port 53 blocked?
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.
How do you do a zone transfer?
Suggested Actions
- In the DNS Manager, right-click the name of the DNS zone and click Properties.
- On the Zone Transfers tab, click Allow zone transfer.
- Select Only to the following servers.
- Click Edit, then in the IP addresses of the secondary servers list, enter the IP addresses of the servers you wish to specify.
What is the purpose of forcing a zone transfer?
DNS zone transfers using the AXFR protocol are the simplest mechanism to replicate DNS records across DNS servers. To avoid the need to edit information on multiple DNS servers, you can edit information on one server and use AXFR to copy information to other servers.
What are the three types of zone transfers?
There are three types of zone transfer to consider:
- Full zone transfer.
- Incremental zone transfer.
- AD replication.
What are the three types of Zone Transfers?
How does zone transfer work?
Zone transfer is the process of copying the contents of the zone file on a primary DNS server to a secondary DNS server. Using zone transfer provides fault tolerance by synchronizing the zone file in a primary DNS server with the zone file in a secondary DNS server.
How is port 53 used in the AXFR protocol?
TCP port 53 is simultaneously used by normal (non-AXFR) DNS clients requesting data that did not fit through UDP. A non-AXFR DNS client tries all queries through UDP first; however, if a UDP DNS server sets the “TC” bit in its response, the DNS client tries the query again through TCP.
Are there any flaws in the AXFR protocol?
One of the flaws in the AXFR protocol is that it’s actually impossible for servers to follow this rule under all circumstances. AXFR clients will sometimes fail to pick up changes in a zone. For example, suppose a BIND 9 AXFR client receives a zone through AXFR, and then checks for changes later.
How does the AXFR protocol work for replicating DNS data?
What AXFR does. AXFR is a mechanism for replicating DNS data across DNS servers. If, for example, the yale.edu administrator has two DNS servers, a.ns.yale.edu and b.ns.yale.edu, he can edit the yale.edu data on a.ns.yale.edu, and rely on AXFR to pull the same data to b.ns.yale.edu.
How does a TCP-SOA AXFR client work?
A TCP-SOA AXFR client, such as named-xfer or axfr-get or dig axfr, actually works as follows. It connects to an AXFR server on TCP port 53. It may then send an SOA request and receive a response. It may then send an AXFR request and receive an AXFR response. It then closes the connection.
