CIDR_TABLE(5) File Formats Manual CIDR_TABLE(5)
cidr_table - format of Postfix CIDR tables
postmap -q "string" cidr:/etc/postfix/filename
postmap -q - cidr:/etc/postfix/filename <inputfile
The Postfix mail system uses optional lookup tables. These tables are
usually in dbm or db format. Alternatively, lookup tables can be
specified in CIDR (Classless Inter-Domain Routing) form. In this case,
each input is compared against a list of patterns. When a match is
found, the corresponding result is returned and the search is
To find out what types of lookup tables your Postfix system supports
use the "postconf -m" command.
To test lookup tables, use the "postmap -q" command as described in the
The general form of a Postfix CIDR table is:
When a search string matches the specified network block, use
the corresponding result value. Specify 0.0.0.0/0 to match every
IPv4 address, and ::/0 to match every IPv6 address.
An IPv4 network address is a sequence of four decimal octets
separated by ".", and an IPv6 network address is a sequence of
three to eight hexadecimal octet pairs separated by ":".
Before comparisons are made, lookup keys and table entries are
converted from string to binary. Therefore table entries will be
matched regardless of redundant zero characters.
Note: address information may be enclosed inside "" but this
form is not required.
IPv6 support is available in Postfix 2.2 and later.
When a search string matches the specified network address, use
the corresponding result value.
blank lines and comments
Empty lines and whitespace-only lines are ignored, as are lines
whose first non-whitespace character is a `#'.
A logical line starts with non-whitespace text. A line that
starts with whitespace continues a logical line.
TABLE SEARCH ORDER
Patterns are applied in the order as specified in the table, until a
pattern is found that matches the search string.
EXAMPLE SMTPD ACCESS MAP
smtpd_client_restrictions = ... cidr:/etc/postfix/client.cidr ...
# Rule order matters. Put more specific whitelist entries
# before more general blacklist entries.
postmap(1), Postfix lookup table manager
regexp_table(5), format of regular expression tables
pcre_table(5), format of PCRE tables
Use "postconf readme_directory" or "postconf html_directory" to locate
DATABASE_README, Postfix lookup table overview
CIDR table support was introduced with Postfix version 2.1.
The CIDR table lookup code was originally written by:
KFKI Research Institute for Particle and Nuclear Physics
1525 Budapest, Hungary
Adopted and adapted by:
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA