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IP subnet calculator

Type an address with its prefix or mask to see the network, its usable range and masks. Split it into smaller subnets, or look up any prefix in the reference tables.

Prefix/113
Addresses32,768
/64 networksPart of one
Network
2001:db8::/113
First address
2001:db8::
Last address
2001:db8::7fff
Addresses
32,768
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
2001:0db8:0000:0000:0000:0000:0000:0000
Type
Documentation 2001:db8::/32
For examples; never used on a network
Reverse DNS zones
0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
3.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
4.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
6.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
7.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
/113 is not on a 4-bit boundary, so it takes 8 /116 zones.
Split into smaller subnets/120
/114 (2)/115 (4)/116 (8)/117 (16)/120 (128)/124 (2,048)/127 (16,384)/128 (32,768)

2001:db8::/113 makes 128 subnets of /120.

Subnets
#SubnetLast address
12001:db8::/1202001:db8::ff
22001:db8::100/1202001:db8::1ff
32001:db8::200/1202001:db8::2ff
42001:db8::300/1202001:db8::3ff
52001:db8::400/1202001:db8::4ff
62001:db8::500/1202001:db8::5ff
72001:db8::600/1202001:db8::6ff
82001:db8::700/1202001:db8::7ff
92001:db8::800/1202001:db8::8ff
102001:db8::900/1202001:db8::9ff
112001:db8::a00/1202001:db8::aff
122001:db8::b00/1202001:db8::bff
132001:db8::c00/1202001:db8::cff
142001:db8::d00/1202001:db8::dff
152001:db8::e00/1202001:db8::eff
162001:db8::f00/1202001:db8::fff
172001:db8::1000/1202001:db8::10ff
182001:db8::1100/1202001:db8::11ff
192001:db8::1200/1202001:db8::12ff
202001:db8::1300/1202001:db8::13ff
212001:db8::1400/1202001:db8::14ff
222001:db8::1500/1202001:db8::15ff
232001:db8::1600/1202001:db8::16ff
242001:db8::1700/1202001:db8::17ff
252001:db8::1800/1202001:db8::18ff
262001:db8::1900/1202001:db8::19ff
272001:db8::1a00/1202001:db8::1aff
282001:db8::1b00/1202001:db8::1bff
292001:db8::1c00/1202001:db8::1cff
302001:db8::1d00/1202001:db8::1dff
312001:db8::1e00/1202001:db8::1eff
322001:db8::1f00/1202001:db8::1fff
332001:db8::2000/1202001:db8::20ff
342001:db8::2100/1202001:db8::21ff
352001:db8::2200/1202001:db8::22ff
362001:db8::2300/1202001:db8::23ff
372001:db8::2400/1202001:db8::24ff
382001:db8::2500/1202001:db8::25ff
392001:db8::2600/1202001:db8::26ff
402001:db8::2700/1202001:db8::27ff
412001:db8::2800/1202001:db8::28ff
422001:db8::2900/1202001:db8::29ff
432001:db8::2a00/1202001:db8::2aff
442001:db8::2b00/1202001:db8::2bff
452001:db8::2c00/1202001:db8::2cff
462001:db8::2d00/1202001:db8::2dff
472001:db8::2e00/1202001:db8::2eff
482001:db8::2f00/1202001:db8::2fff
492001:db8::3000/1202001:db8::30ff
502001:db8::3100/1202001:db8::31ff
512001:db8::3200/1202001:db8::32ff
522001:db8::3300/1202001:db8::33ff
532001:db8::3400/1202001:db8::34ff
542001:db8::3500/1202001:db8::35ff
552001:db8::3600/1202001:db8::36ff
562001:db8::3700/1202001:db8::37ff
572001:db8::3800/1202001:db8::38ff
582001:db8::3900/1202001:db8::39ff
592001:db8::3a00/1202001:db8::3aff
602001:db8::3b00/1202001:db8::3bff
612001:db8::3c00/1202001:db8::3cff
622001:db8::3d00/1202001:db8::3dff
632001:db8::3e00/1202001:db8::3eff
642001:db8::3f00/1202001:db8::3fff
652001:db8::4000/1202001:db8::40ff
662001:db8::4100/1202001:db8::41ff
672001:db8::4200/1202001:db8::42ff
682001:db8::4300/1202001:db8::43ff
692001:db8::4400/1202001:db8::44ff
702001:db8::4500/1202001:db8::45ff
712001:db8::4600/1202001:db8::46ff
722001:db8::4700/1202001:db8::47ff
732001:db8::4800/1202001:db8::48ff
742001:db8::4900/1202001:db8::49ff
752001:db8::4a00/1202001:db8::4aff
762001:db8::4b00/1202001:db8::4bff
772001:db8::4c00/1202001:db8::4cff
782001:db8::4d00/1202001:db8::4dff
792001:db8::4e00/1202001:db8::4eff
802001:db8::4f00/1202001:db8::4fff
812001:db8::5000/1202001:db8::50ff
822001:db8::5100/1202001:db8::51ff
832001:db8::5200/1202001:db8::52ff
842001:db8::5300/1202001:db8::53ff
852001:db8::5400/1202001:db8::54ff
862001:db8::5500/1202001:db8::55ff
872001:db8::5600/1202001:db8::56ff
882001:db8::5700/1202001:db8::57ff
892001:db8::5800/1202001:db8::58ff
902001:db8::5900/1202001:db8::59ff
912001:db8::5a00/1202001:db8::5aff
922001:db8::5b00/1202001:db8::5bff
932001:db8::5c00/1202001:db8::5cff
942001:db8::5d00/1202001:db8::5dff
952001:db8::5e00/1202001:db8::5eff
962001:db8::5f00/1202001:db8::5fff
972001:db8::6000/1202001:db8::60ff
982001:db8::6100/1202001:db8::61ff
992001:db8::6200/1202001:db8::62ff
1002001:db8::6300/1202001:db8::63ff
1012001:db8::6400/1202001:db8::64ff
1022001:db8::6500/1202001:db8::65ff
1032001:db8::6600/1202001:db8::66ff
1042001:db8::6700/1202001:db8::67ff
1052001:db8::6800/1202001:db8::68ff
1062001:db8::6900/1202001:db8::69ff
1072001:db8::6a00/1202001:db8::6aff
1082001:db8::6b00/1202001:db8::6bff
1092001:db8::6c00/1202001:db8::6cff
1102001:db8::6d00/1202001:db8::6dff
1112001:db8::6e00/1202001:db8::6eff
1122001:db8::6f00/1202001:db8::6fff
1132001:db8::7000/1202001:db8::70ff
1142001:db8::7100/1202001:db8::71ff
1152001:db8::7200/1202001:db8::72ff
1162001:db8::7300/1202001:db8::73ff
1172001:db8::7400/1202001:db8::74ff
1182001:db8::7500/1202001:db8::75ff
1192001:db8::7600/1202001:db8::76ff
1202001:db8::7700/1202001:db8::77ff
1212001:db8::7800/1202001:db8::78ff
1222001:db8::7900/1202001:db8::79ff
1232001:db8::7a00/1202001:db8::7aff
1242001:db8::7b00/1202001:db8::7bff
1252001:db8::7c00/1202001:db8::7cff
1262001:db8::7d00/1202001:db8::7dff
1272001:db8::7e00/1202001:db8::7eff
1282001:db8::7f00/1202001:db8::7fff

IPv4 CIDR reference (/0 to /32)

IPv4 prefix lengths
PrefixSubnet maskWildcardAddressesUsable hostsSizeTypical use
/00.0.0.0255.255.255.2554,294,967,2964,294,967,29416,777,216 × /24
/1128.0.0.0127.255.255.2552,147,483,6482,147,483,6468,388,608 × /24
/2192.0.0.063.255.255.2551,073,741,8241,073,741,8224,194,304 × /24
/3224.0.0.031.255.255.255536,870,912536,870,9102,097,152 × /24
/4240.0.0.015.255.255.255268,435,456268,435,4541,048,576 × /24
/5248.0.0.07.255.255.255134,217,728134,217,726524,288 × /24
/6252.0.0.03.255.255.25567,108,86467,108,862262,144 × /24
/7254.0.0.01.255.255.25533,554,43233,554,430131,072 × /24
/8255.0.0.00.255.255.25516,777,21616,777,21465,536 × /24Old class A; 10.0.0.0/8
/9255.128.0.00.127.255.2558,388,6088,388,60632,768 × /24
/10255.192.0.00.63.255.2554,194,3044,194,30216,384 × /24
/11255.224.0.00.31.255.2552,097,1522,097,1508,192 × /24
/12255.240.0.00.15.255.2551,048,5761,048,5744,096 × /24172.16.0.0/12
/13255.248.0.00.7.255.255524,288524,2862,048 × /24
/14255.252.0.00.3.255.255262,144262,1421,024 × /24
/15255.254.0.00.1.255.255131,072131,070512 × /24
/16255.255.0.00.0.255.25565,53665,534256 × /24Old class B; 192.168.0.0/16
/17255.255.128.00.0.127.25532,76832,766128 × /24
/18255.255.192.00.0.63.25516,38416,38264 × /24
/19255.255.224.00.0.31.2558,1928,19032 × /24
/20255.255.240.00.0.15.2554,0964,09416 × /24
/21255.255.248.00.0.7.2552,0482,0468 × /24
/22255.255.252.00.0.3.2551,0241,0224 × /24Large office or guest Wi-Fi (1,022 hosts)
/23255.255.254.00.0.1.2555125102 × /24Larger office LAN (510 hosts)
/24255.255.255.00.0.0.2552562541 × /24Typical office LAN (old class C)
/25255.255.255.1280.0.0.1271281261/2 of a /24Smaller LAN or VLAN
/26255.255.255.1920.0.0.6364621/4 of a /24Smaller LAN or VLAN
/27255.255.255.2240.0.0.3132301/8 of a /24Small VLAN, phones, cameras
/28255.255.255.2400.0.0.1516141/16 of a /24Small VLAN, phones, cameras
/29255.255.255.2480.0.0.7861/32 of a /24Small fixed public block (5 usable)
/30255.255.255.2520.0.0.3421/64 of a /24Point-to-point (old style)
/31255.255.255.2540.0.0.1221/128 of a /24Point-to-point link (RFC 3021)
/32255.255.255.2550.0.0.0111/256 of a /24One host

IPv6 prefix reference

IPv6 prefix lengths
PrefixAddresses/64 LANs/48 sitesNibbleTypical use
/342,535,295,865,117,307,932,921,825,928,971,026,432 (2^125)2,305,843,009,213,693,95235,184,372,088,832NoAll global unicast (2000::/3)
/165,192,296,858,534,827,628,530,496,329,220,096 (2^112)281,474,976,710,6564,294,967,296Yes
/20324,518,553,658,426,726,783,156,020,576,256 (2^108)17,592,186,044,416268,435,456YesLarge provider allocation (RIPE minimum for some)
/29633,825,300,114,114,700,748,351,602,688 (2^99)34,359,738,368524,288NoRIPE allocation to a provider (often)
/3279,228,162,514,264,337,593,543,950,336 (2^96)4,294,967,29665,536YesProvider allocation (RIPE default)
/364,951,760,157,141,521,099,596,496,896 (2^92)268,435,4564,096Yes
/40309,485,009,821,345,068,724,781,056 (2^88)16,777,216256Yes
/4419,342,813,113,834,066,795,298,816 (2^84)1,048,57616Yes
/481,208,925,819,614,629,174,706,176 (2^80)65,5361YesOne site or organisation (RIPE PI / assignment)
/5275,557,863,725,914,323,419,136 (2^76)4,096Yes
/564,722,366,482,869,645,213,696 (2^72)256YesSmall site or home (common provider assignment)
/60295,147,905,179,352,825,856 (2^68)16YesSome home broadband (16 LANs)
/6418,446,744,073,709,551,616 (2^64)1YesOne LAN or VLAN (needed for SLAAC)
/7272,057,594,037,927,936 (2^56)1/256 of a /64Yes
/80281,474,976,710,656 (2^48)1/65,536 of a /64Yes
/964,294,967,2961/4,294,967,296 of a /64YesEmbeds an IPv4 address (NAT64)
/11265,5361/281,474,976,710,656 of a /64Yes
/1202561/72,057,594,037,927,936 of a /64Yes
/124161/1,152,921,504,606,846,976 of a /64Yes
/12641/4,611,686,018,427,387,904 of a /64No
/12721/9,223,372,036,854,775,808 of a /64NoPoint-to-point link (RFC 6164)
/12811/18,446,744,073,709,551,616 of a /64YesOne host or loopback

Private and special ranges

IPv4

Special-purpose ranges
RangeNameWhat it is
255.255.255.255/32Limited broadcastEvery host on the local network
0.0.0.0/8This networkNot routed; 0.0.0.0 means "any address" in settings
10.0.0.0/8Private (RFC 1918)Office and home networks; not routed on the internet
100.64.0.0/10Shared address space (CGNAT)Used by providers behind carrier-grade NAT (RFC 6598)
127.0.0.0/8LoopbackThis computer
169.254.0.0/16Link-local (APIPA)Self-assigned when no DHCP server answers
172.16.0.0/12Private (RFC 1918)Office and home networks; not routed on the internet
192.0.0.0/24IETF protocol assignmentsSpecial uses such as DS-Lite
192.0.2.0/24Documentation (TEST-NET-1)For examples; never used on a network
192.88.99.0/246to4 relay (deprecated)Formerly anycast for 6to4
192.168.0.0/16Private (RFC 1918)Office and home networks; not routed on the internet
198.18.0.0/15BenchmarkingNetwork equipment testing (RFC 2544)
198.51.100.0/24Documentation (TEST-NET-2)For examples; never used on a network
203.0.113.0/24Documentation (TEST-NET-3)For examples; never used on a network
224.0.0.0/4MulticastOne-to-many traffic, such as IPTV and routing protocols
240.0.0.0/4ReservedFuture use; not usable on most systems

IPv6

Special-purpose ranges
RangeNameWhat it is
::/128UnspecifiedNo address; :: means "any address" in settings
::1/128LoopbackThis computer
::ffff:0:0/96IPv4-mappedAn IPv4 address written as IPv6
64:ff9b::/96NAT64IPv4 addresses reached through a NAT64 gateway
100::/64Discard onlyTraffic sent here is dropped (RFC 6666)
2001:db8::/32DocumentationFor examples; never used on a network
2001::/32TeredoIPv6 tunnelled over IPv4 UDP
2002::/166to4IPv6 tunnelled over IPv4 (largely retired)
3fff::/20DocumentationFor examples (RFC 9637)
fc00::/7Unique local (ULA)Private IPv6, like RFC 1918; usually fd00::/8
fe80::/10Link-localEvery IPv6 interface has one; not routed
ff00::/8MulticastOne-to-many traffic; replaces broadcast
2000::/3Global unicastPublic internet addresses

About this tool

A network is written as an address and a prefix length, such as 192.168.1.0/24: the first 24 bits name the network and the rest number the devices on it. The calculator works out where the network starts and ends, how many devices it holds, its subnet and wildcard masks, and the reverse DNS zone to ask your provider for.

It also splits a network into equal smaller ones (one per VLAN or site), turns a range of addresses into the fewest CIDR blocks for a firewall rule, and lists every IPv4 prefix length and the common IPv6 ones in reference tables.

Common questions

Why are two addresses lost in every IPv4 subnet?

The first address names the network and the last is the broadcast address, so a /24 has 256 addresses but 254 for devices. A /31 (a link between two routers) and a /32 (one host) are the exceptions.

What size of IPv6 network should a LAN use?

Always /64. Devices pick their own address within it (SLAAC), which needs the full 64 bits. A site usually gets a /48 or /56 from its provider, which holds 65,536 or 256 LANs.

What is a wildcard mask?

The subnet mask turned inside out: 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF use it to say which bits must match.

Which ranges can I use inside an office?

IPv4: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. IPv6: unique local addresses from fd00::/8, though most networks use the public prefix from their provider.