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 terminated.

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 SYNOPSIS above.


The general form of a Postfix CIDR table is:
network_address/network_mask result When a search string matches the specified network block, use the corresponding result value. Specify 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.

network_address result 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 ‘#’.
multi-line text A logical line starts with non-whitespace text. A line that starts with whitespace continues a logical line.


Patterns are applied in the order as specified in the table, until a pattern is found that matches the search string.


/etc/postfix/ smtpd_client_restrictions = ... cidr:/etc/postfix/client.cidr ...

/etc/postfix/client.cidr: # Rule order matters. Put more specific whitelist entries # before more general blacklist entries. OK REJECT


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 this information. 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: Jozsef Kadlecsik KFKI Research Institute for Particle and Nuclear Physics POB. 49 1525 Budapest, Hungary

Adopted and adapted by: Wietse Venema IBM T.J. Watson Research P.O. Box 704 Yorktown Heights, NY 10598, USA

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