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 ":". The network_mask is the number of high-order bits in the network_address that the search string must match. 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