.TH CIDR_TABLE 5 
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.SH NAME
cidr_table
\-
format of Postfix CIDR tables
.SH "SYNOPSIS"
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\fBpostmap \-q "\fIstring\fB" cidr:/etc/postfix/\fIfilename\fR

\fBpostmap \-q \- cidr:/etc/postfix/\fIfilename\fB <\fIinputfile\fR
.SH DESCRIPTION
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The Postfix mail system uses optional lookup tables.
These tables are usually in \fBdbm\fR or \fBdb\fR 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 "\fBpostconf \-m\fR" command.

To test lookup tables, use the "\fBpostmap \-q\fR" command as
described in the SYNOPSIS above.
.SH "TABLE FORMAT"
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The general form of a Postfix CIDR table is:
.IP "\fInetwork_address\fB/\fInetwork_mask     result\fR"
When a search string matches the specified network block,
use the corresponding \fIresult\fR 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 \fInetwork_mask\fR is the number of high\-order bits in
the \fInetwork_address\fR 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.
.IP "\fInetwork_address     result\fR"
When a search string matches the specified network address,
use the corresponding \fIresult\fR value.
.IP "blank lines and comments"
Empty lines and whitespace\-only lines are ignored, as
are lines whose first non\-whitespace character is a `#'.
.IP "multi\-line text"
A logical line starts with non\-whitespace text. A line that
starts with whitespace continues a logical line.
.SH "TABLE SEARCH ORDER"
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Patterns are applied in the order as specified in the table, until a
pattern is found that matches the search string.
.SH "EXAMPLE SMTPD ACCESS MAP"
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/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
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.SH "SEE ALSO"
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postmap(1), Postfix lookup table manager
regexp_table(5), format of regular expression tables
pcre_table(5), format of PCRE tables
.SH "README FILES"
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Use "\fBpostconf readme_directory\fR" or
"\fBpostconf html_directory\fR" to locate this information.
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DATABASE_README, Postfix lookup table overview
.SH HISTORY
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CIDR table support was introduced with Postfix version 2.1.
.SH "AUTHOR(S)"
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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

Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA