If the `soa' table contains a column named `xfer' and DNS-based zone transfers are enabled (see section 4.4 Zone transfers), the `xfer' column will be examined whenever a DNS-based zone transfer request is received.
The `xfer' column should contain one or more IP addresses separated by commas. These IP addresses will be allowed to transfer the zone.
If the `xfer' column is empty, no DNS-based zone transfers will be allowed for that zone.
The IP addresses in `xfer' may contain standard wildcard characters. Thus, if you want to grant zone transfer access for a particular zone to any IP address, you would set `xfer' to `*'.
Addresses may also be specified in CIDR notation (i.e.
or in network/netmask notation (i.e.
The `xfer' column may be any size you want, and whatever size you think will be adequate for the IP address lists you intend to use.
To create an `xfer' column on your `soa' table, for example, you might issue SQL statements like this:
mysql> ALTER TABLE mydns.soa ADD COLUMN xfer CHAR(255) NOT NULL;
mydns=# ALTER TABLE soa ADD COLUMN xfer VARCHAR(255); mydns=# UPDATE soa SET xfer=''; mydns=# ALTER TABLE soa ALTER COLUMN xfer SET NOT NULL; mydns=# ALTER TABLE soa ALTER COLUMN xfer SET DEFAULT '';