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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.

Network17.96.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
17.96.0.0
Broadcast address
17.111.255.255
First usable
17.96.0.1
Last usable
17.111.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Public public
Old class
A (default /8)
As numbers
Hex 11600000 · Integer 291504128 to 292552703
Reverse DNS zones
96.17.in-addr.arpa
97.17.in-addr.arpa
98.17.in-addr.arpa
99.17.in-addr.arpa
100.17.in-addr.arpa
101.17.in-addr.arpa
102.17.in-addr.arpa
103.17.in-addr.arpa
104.17.in-addr.arpa
105.17.in-addr.arpa
106.17.in-addr.arpa
107.17.in-addr.arpa
108.17.in-addr.arpa
109.17.in-addr.arpa
110.17.in-addr.arpa
111.17.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00010001.01100000.00000000.0000000017.96.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network00010001.01100000.00000000.0000000017.96.0.0
Broadcast00010001.01101111.11111111.1111111117.111.255.255
Split into smaller subnets/19
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

17.96.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
117.96.0.0/1917.96.0.1 to 17.96.31.25417.96.31.2558,190
217.96.32.0/1917.96.32.1 to 17.96.63.25417.96.63.2558,190
317.96.64.0/1917.96.64.1 to 17.96.95.25417.96.95.2558,190
417.96.96.0/1917.96.96.1 to 17.96.127.25417.96.127.2558,190
517.96.128.0/1917.96.128.1 to 17.96.159.25417.96.159.2558,190
617.96.160.0/1917.96.160.1 to 17.96.191.25417.96.191.2558,190
717.96.192.0/1917.96.192.1 to 17.96.223.25417.96.223.2558,190
817.96.224.0/1917.96.224.1 to 17.96.255.25417.96.255.2558,190
917.97.0.0/1917.97.0.1 to 17.97.31.25417.97.31.2558,190
1017.97.32.0/1917.97.32.1 to 17.97.63.25417.97.63.2558,190
1117.97.64.0/1917.97.64.1 to 17.97.95.25417.97.95.2558,190
1217.97.96.0/1917.97.96.1 to 17.97.127.25417.97.127.2558,190
1317.97.128.0/1917.97.128.1 to 17.97.159.25417.97.159.2558,190
1417.97.160.0/1917.97.160.1 to 17.97.191.25417.97.191.2558,190
1517.97.192.0/1917.97.192.1 to 17.97.223.25417.97.223.2558,190
1617.97.224.0/1917.97.224.1 to 17.97.255.25417.97.255.2558,190
1717.98.0.0/1917.98.0.1 to 17.98.31.25417.98.31.2558,190
1817.98.32.0/1917.98.32.1 to 17.98.63.25417.98.63.2558,190
1917.98.64.0/1917.98.64.1 to 17.98.95.25417.98.95.2558,190
2017.98.96.0/1917.98.96.1 to 17.98.127.25417.98.127.2558,190
2117.98.128.0/1917.98.128.1 to 17.98.159.25417.98.159.2558,190
2217.98.160.0/1917.98.160.1 to 17.98.191.25417.98.191.2558,190
2317.98.192.0/1917.98.192.1 to 17.98.223.25417.98.223.2558,190
2417.98.224.0/1917.98.224.1 to 17.98.255.25417.98.255.2558,190
2517.99.0.0/1917.99.0.1 to 17.99.31.25417.99.31.2558,190
2617.99.32.0/1917.99.32.1 to 17.99.63.25417.99.63.2558,190
2717.99.64.0/1917.99.64.1 to 17.99.95.25417.99.95.2558,190
2817.99.96.0/1917.99.96.1 to 17.99.127.25417.99.127.2558,190
2917.99.128.0/1917.99.128.1 to 17.99.159.25417.99.159.2558,190
3017.99.160.0/1917.99.160.1 to 17.99.191.25417.99.191.2558,190
3117.99.192.0/1917.99.192.1 to 17.99.223.25417.99.223.2558,190
3217.99.224.0/1917.99.224.1 to 17.99.255.25417.99.255.2558,190
3317.100.0.0/1917.100.0.1 to 17.100.31.25417.100.31.2558,190
3417.100.32.0/1917.100.32.1 to 17.100.63.25417.100.63.2558,190
3517.100.64.0/1917.100.64.1 to 17.100.95.25417.100.95.2558,190
3617.100.96.0/1917.100.96.1 to 17.100.127.25417.100.127.2558,190
3717.100.128.0/1917.100.128.1 to 17.100.159.25417.100.159.2558,190
3817.100.160.0/1917.100.160.1 to 17.100.191.25417.100.191.2558,190
3917.100.192.0/1917.100.192.1 to 17.100.223.25417.100.223.2558,190
4017.100.224.0/1917.100.224.1 to 17.100.255.25417.100.255.2558,190
4117.101.0.0/1917.101.0.1 to 17.101.31.25417.101.31.2558,190
4217.101.32.0/1917.101.32.1 to 17.101.63.25417.101.63.2558,190
4317.101.64.0/1917.101.64.1 to 17.101.95.25417.101.95.2558,190
4417.101.96.0/1917.101.96.1 to 17.101.127.25417.101.127.2558,190
4517.101.128.0/1917.101.128.1 to 17.101.159.25417.101.159.2558,190
4617.101.160.0/1917.101.160.1 to 17.101.191.25417.101.191.2558,190
4717.101.192.0/1917.101.192.1 to 17.101.223.25417.101.223.2558,190
4817.101.224.0/1917.101.224.1 to 17.101.255.25417.101.255.2558,190
4917.102.0.0/1917.102.0.1 to 17.102.31.25417.102.31.2558,190
5017.102.32.0/1917.102.32.1 to 17.102.63.25417.102.63.2558,190
5117.102.64.0/1917.102.64.1 to 17.102.95.25417.102.95.2558,190
5217.102.96.0/1917.102.96.1 to 17.102.127.25417.102.127.2558,190
5317.102.128.0/1917.102.128.1 to 17.102.159.25417.102.159.2558,190
5417.102.160.0/1917.102.160.1 to 17.102.191.25417.102.191.2558,190
5517.102.192.0/1917.102.192.1 to 17.102.223.25417.102.223.2558,190
5617.102.224.0/1917.102.224.1 to 17.102.255.25417.102.255.2558,190
5717.103.0.0/1917.103.0.1 to 17.103.31.25417.103.31.2558,190
5817.103.32.0/1917.103.32.1 to 17.103.63.25417.103.63.2558,190
5917.103.64.0/1917.103.64.1 to 17.103.95.25417.103.95.2558,190
6017.103.96.0/1917.103.96.1 to 17.103.127.25417.103.127.2558,190
6117.103.128.0/1917.103.128.1 to 17.103.159.25417.103.159.2558,190
6217.103.160.0/1917.103.160.1 to 17.103.191.25417.103.191.2558,190
6317.103.192.0/1917.103.192.1 to 17.103.223.25417.103.223.2558,190
6417.103.224.0/1917.103.224.1 to 17.103.255.25417.103.255.2558,190
6517.104.0.0/1917.104.0.1 to 17.104.31.25417.104.31.2558,190
6617.104.32.0/1917.104.32.1 to 17.104.63.25417.104.63.2558,190
6717.104.64.0/1917.104.64.1 to 17.104.95.25417.104.95.2558,190
6817.104.96.0/1917.104.96.1 to 17.104.127.25417.104.127.2558,190
6917.104.128.0/1917.104.128.1 to 17.104.159.25417.104.159.2558,190
7017.104.160.0/1917.104.160.1 to 17.104.191.25417.104.191.2558,190
7117.104.192.0/1917.104.192.1 to 17.104.223.25417.104.223.2558,190
7217.104.224.0/1917.104.224.1 to 17.104.255.25417.104.255.2558,190
7317.105.0.0/1917.105.0.1 to 17.105.31.25417.105.31.2558,190
7417.105.32.0/1917.105.32.1 to 17.105.63.25417.105.63.2558,190
7517.105.64.0/1917.105.64.1 to 17.105.95.25417.105.95.2558,190
7617.105.96.0/1917.105.96.1 to 17.105.127.25417.105.127.2558,190
7717.105.128.0/1917.105.128.1 to 17.105.159.25417.105.159.2558,190
7817.105.160.0/1917.105.160.1 to 17.105.191.25417.105.191.2558,190
7917.105.192.0/1917.105.192.1 to 17.105.223.25417.105.223.2558,190
8017.105.224.0/1917.105.224.1 to 17.105.255.25417.105.255.2558,190
8117.106.0.0/1917.106.0.1 to 17.106.31.25417.106.31.2558,190
8217.106.32.0/1917.106.32.1 to 17.106.63.25417.106.63.2558,190
8317.106.64.0/1917.106.64.1 to 17.106.95.25417.106.95.2558,190
8417.106.96.0/1917.106.96.1 to 17.106.127.25417.106.127.2558,190
8517.106.128.0/1917.106.128.1 to 17.106.159.25417.106.159.2558,190
8617.106.160.0/1917.106.160.1 to 17.106.191.25417.106.191.2558,190
8717.106.192.0/1917.106.192.1 to 17.106.223.25417.106.223.2558,190
8817.106.224.0/1917.106.224.1 to 17.106.255.25417.106.255.2558,190
8917.107.0.0/1917.107.0.1 to 17.107.31.25417.107.31.2558,190
9017.107.32.0/1917.107.32.1 to 17.107.63.25417.107.63.2558,190
9117.107.64.0/1917.107.64.1 to 17.107.95.25417.107.95.2558,190
9217.107.96.0/1917.107.96.1 to 17.107.127.25417.107.127.2558,190
9317.107.128.0/1917.107.128.1 to 17.107.159.25417.107.159.2558,190
9417.107.160.0/1917.107.160.1 to 17.107.191.25417.107.191.2558,190
9517.107.192.0/1917.107.192.1 to 17.107.223.25417.107.223.2558,190
9617.107.224.0/1917.107.224.1 to 17.107.255.25417.107.255.2558,190
9717.108.0.0/1917.108.0.1 to 17.108.31.25417.108.31.2558,190
9817.108.32.0/1917.108.32.1 to 17.108.63.25417.108.63.2558,190
9917.108.64.0/1917.108.64.1 to 17.108.95.25417.108.95.2558,190
10017.108.96.0/1917.108.96.1 to 17.108.127.25417.108.127.2558,190
10117.108.128.0/1917.108.128.1 to 17.108.159.25417.108.159.2558,190
10217.108.160.0/1917.108.160.1 to 17.108.191.25417.108.191.2558,190
10317.108.192.0/1917.108.192.1 to 17.108.223.25417.108.223.2558,190
10417.108.224.0/1917.108.224.1 to 17.108.255.25417.108.255.2558,190
10517.109.0.0/1917.109.0.1 to 17.109.31.25417.109.31.2558,190
10617.109.32.0/1917.109.32.1 to 17.109.63.25417.109.63.2558,190
10717.109.64.0/1917.109.64.1 to 17.109.95.25417.109.95.2558,190
10817.109.96.0/1917.109.96.1 to 17.109.127.25417.109.127.2558,190
10917.109.128.0/1917.109.128.1 to 17.109.159.25417.109.159.2558,190
11017.109.160.0/1917.109.160.1 to 17.109.191.25417.109.191.2558,190
11117.109.192.0/1917.109.192.1 to 17.109.223.25417.109.223.2558,190
11217.109.224.0/1917.109.224.1 to 17.109.255.25417.109.255.2558,190
11317.110.0.0/1917.110.0.1 to 17.110.31.25417.110.31.2558,190
11417.110.32.0/1917.110.32.1 to 17.110.63.25417.110.63.2558,190
11517.110.64.0/1917.110.64.1 to 17.110.95.25417.110.95.2558,190
11617.110.96.0/1917.110.96.1 to 17.110.127.25417.110.127.2558,190
11717.110.128.0/1917.110.128.1 to 17.110.159.25417.110.159.2558,190
11817.110.160.0/1917.110.160.1 to 17.110.191.25417.110.191.2558,190
11917.110.192.0/1917.110.192.1 to 17.110.223.25417.110.223.2558,190
12017.110.224.0/1917.110.224.1 to 17.110.255.25417.110.255.2558,190
12117.111.0.0/1917.111.0.1 to 17.111.31.25417.111.31.2558,190
12217.111.32.0/1917.111.32.1 to 17.111.63.25417.111.63.2558,190
12317.111.64.0/1917.111.64.1 to 17.111.95.25417.111.95.2558,190
12417.111.96.0/1917.111.96.1 to 17.111.127.25417.111.127.2558,190
12517.111.128.0/1917.111.128.1 to 17.111.159.25417.111.159.2558,190
12617.111.160.0/1917.111.160.1 to 17.111.191.25417.111.191.2558,190
12717.111.192.0/1917.111.192.1 to 17.111.223.25417.111.223.2558,190
12817.111.224.0/1917.111.224.1 to 17.111.255.25417.111.255.2558,190

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.