/ 
NetAddr-IP-4.080_02
/ NetAddr::IP::Constants

NAME

NetAddr::IP::Constants - Magic number constants for NetAddr::IP

VERSION

version 4.080_02

SYNOPSIS

use NetAddr::IP::Constants qw($IPV6_BITS $IPV4_BITS $IPV4_OFFSET);

DESCRIPTION

Provides named constants for magic numbers used throughout the NetAddr::IP family of modules. Importing by name avoids polluting the caller namespace with abbreviations and ensures that each constant resolves at compile time.

All constants are our variables and may be overridden by the caller if needed, but doing so is unsupported.

NAME

NetAddr::IP::Constants - Magic number constants for NetAddr::IP

CONSTANTS

DEFAULT_NETLIMIT_EXP
Power-of-two exponent for the default netlimit.  The default is
C<2**16 = 65536> networks.  Value: C<16>.
IPV4_BITS
IPv4 address width in bits.  Value: C<32>.
RFC 791 s2.1.
IPV4_OFFSET
Offset of the IPv4-in-IPv6 mapped address in the 128-bit
representation.  Value: C<96> (i.e. C<IPV6_BITS - IPV4_BITS>).
RFC 4291 s2.5.5 (dual-stack, V4-mapped, V4-compatible).
IPV6_BITS
IPv6 address width in bits.  Value: C<128>.
RFC 4291 s2.1.
MAX_BCD_DIGITS
Maximum number of BCD digits that can represent a 128-bit value.
Value: C<40> (i.e. C<ceil(128 * log10(2))>).
MAX_NETLIMIT_EXP
Power-of-two exponent for the maximum netlimit.  The maximum is
C<2**24 = 16777216> networks.  Value: C<24>.
MAX_OCTET
Maximum value of a single IPv4 octet.  Value: C<255> (C<0xff>).
RFC 791 s2.1.
MAX_SHIFTLEFT
Maximum number of bits that can be shifted by C<shiftleft()>.
Value: C<128> (i.e. C<IPV6_BITS>).
OCTET_BITS
Number of bits in a single IPv4 octet.  Value: C<8>.
RFC 791 s2.1.
OCTET_COUNT
Number of octets in an IPv4 address.  Value: C<4>.
RFC 791 s2.1.
PACKED_BCD_BYTES
Size of a packed BCD string holding B<MAX_BCD_DIGITS> digits.
Value: C<20> (C<40/2>, two digits per byte).
RFC3021_THRESHOLD
Point-to-point network boundary.  Networks of length /127 or /31
are treated as having exactly two usable addresses per RFC 3021.
Value: C<127> (i.e. C<IPV6_BITS - 1>).
V4_PACKED_BYTES
Size of a packed IPv4 address in bytes.  Value: C<4> (C<32/8>).
RFC 791 s2.1.
V6_PACKED_BYTES
Size of a packed IPv6 address in bytes.  Value: C<16> (C<128/8>).
RFC 4291 s2.1.

EXPORTS

Nothing is exported by default. Use explicit import tags:

use NetAddr::IP::Constants qw(:all);

or import individual constants:

use NetAddr::IP::Constants qw($IPV6_BITS $IPV4_BITS);

AUTHORS

  • Dean Hamstead <dean@fragfest.com.au>

  • Luis E. Muñoz <luismunoz@cpan.org>

  • Michael Robinton <miker@cpan.org>

COPYRIGHT AND LICENSE

This software is Copyright (c) 2026 by Dean Hamstead.

This is free software, licensed under:

The GNU General Public License, Version 2, June 1991