CIDR_TABLE(5)

NAME
cidr_table - format of Postfix CIDR tables

SYNOPSIS
postmap -q "string" cidr:/etc/postfix/filename
postmap -q - cidr:/etc/postfix/filename <inputfile

DESCRIPTION
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.

TABLE FORMAT
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 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.

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.

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
/etc/postfix/main.cf:
    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.
    192.168.1.1             OK
    192.168.0.0/16          REJECT

SEE ALSO
postmap(1), Postfix lookup table manager
regexp_table(5), format of regular expression tables
pcre_table(5), format of PCRE tables

README FILES
Use "postconf readme_directory" or "postconf html_directory" to locate this information.
DATABASE_README, Postfix lookup table overview

HISTORY
CIDR table support was introduced with Postfix version 2.1.

AUTHOR(S)
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