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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.

Network77.78.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
77.78.0.0
Broadcast address
77.78.127.255
First usable
77.78.0.1
Last usable
77.78.127.254
Usable hosts
32,766 (32,768 less the network and broadcast addresses)
Subnet mask
255.255.128.0
Wildcard mask
0.0.127.255 (Cisco ACLs, OSPF)
Prefix length
/17
Type
Public public
Old class
A (default /8)
As numbers
Hex 4D4E0000 · Integer 1296957440 to 1296990207
Reverse DNS zones
0.78.77.in-addr.arpa
1.78.77.in-addr.arpa
2.78.77.in-addr.arpa
3.78.77.in-addr.arpa
4.78.77.in-addr.arpa
5.78.77.in-addr.arpa
6.78.77.in-addr.arpa
7.78.77.in-addr.arpa
8.78.77.in-addr.arpa
9.78.77.in-addr.arpa
10.78.77.in-addr.arpa
11.78.77.in-addr.arpa
12.78.77.in-addr.arpa
13.78.77.in-addr.arpa
14.78.77.in-addr.arpa
15.78.77.in-addr.arpa
and 112 more
/17 is not on a 8-bit boundary, so it takes 128 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01001101.01001110.00000000.0000000077.78.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network01001101.01001110.00000000.0000000077.78.0.0
Broadcast01001101.01001110.01111111.1111111177.78.127.255
Split into smaller subnets/23
/18 (2)/19 (4)/20 (8)/21 (16)/22 (32)/23 (64)/24 (128)/25 (256)/26 (512)/27 (1,024)/28 (2,048)/29 (4,096)

77.78.0.0/17 makes 64 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
177.78.0.0/2377.78.0.1 to 77.78.1.25477.78.1.255510
277.78.2.0/2377.78.2.1 to 77.78.3.25477.78.3.255510
377.78.4.0/2377.78.4.1 to 77.78.5.25477.78.5.255510
477.78.6.0/2377.78.6.1 to 77.78.7.25477.78.7.255510
577.78.8.0/2377.78.8.1 to 77.78.9.25477.78.9.255510
677.78.10.0/2377.78.10.1 to 77.78.11.25477.78.11.255510
777.78.12.0/2377.78.12.1 to 77.78.13.25477.78.13.255510
877.78.14.0/2377.78.14.1 to 77.78.15.25477.78.15.255510
977.78.16.0/2377.78.16.1 to 77.78.17.25477.78.17.255510
1077.78.18.0/2377.78.18.1 to 77.78.19.25477.78.19.255510
1177.78.20.0/2377.78.20.1 to 77.78.21.25477.78.21.255510
1277.78.22.0/2377.78.22.1 to 77.78.23.25477.78.23.255510
1377.78.24.0/2377.78.24.1 to 77.78.25.25477.78.25.255510
1477.78.26.0/2377.78.26.1 to 77.78.27.25477.78.27.255510
1577.78.28.0/2377.78.28.1 to 77.78.29.25477.78.29.255510
1677.78.30.0/2377.78.30.1 to 77.78.31.25477.78.31.255510
1777.78.32.0/2377.78.32.1 to 77.78.33.25477.78.33.255510
1877.78.34.0/2377.78.34.1 to 77.78.35.25477.78.35.255510
1977.78.36.0/2377.78.36.1 to 77.78.37.25477.78.37.255510
2077.78.38.0/2377.78.38.1 to 77.78.39.25477.78.39.255510
2177.78.40.0/2377.78.40.1 to 77.78.41.25477.78.41.255510
2277.78.42.0/2377.78.42.1 to 77.78.43.25477.78.43.255510
2377.78.44.0/2377.78.44.1 to 77.78.45.25477.78.45.255510
2477.78.46.0/2377.78.46.1 to 77.78.47.25477.78.47.255510
2577.78.48.0/2377.78.48.1 to 77.78.49.25477.78.49.255510
2677.78.50.0/2377.78.50.1 to 77.78.51.25477.78.51.255510
2777.78.52.0/2377.78.52.1 to 77.78.53.25477.78.53.255510
2877.78.54.0/2377.78.54.1 to 77.78.55.25477.78.55.255510
2977.78.56.0/2377.78.56.1 to 77.78.57.25477.78.57.255510
3077.78.58.0/2377.78.58.1 to 77.78.59.25477.78.59.255510
3177.78.60.0/2377.78.60.1 to 77.78.61.25477.78.61.255510
3277.78.62.0/2377.78.62.1 to 77.78.63.25477.78.63.255510
3377.78.64.0/2377.78.64.1 to 77.78.65.25477.78.65.255510
3477.78.66.0/2377.78.66.1 to 77.78.67.25477.78.67.255510
3577.78.68.0/2377.78.68.1 to 77.78.69.25477.78.69.255510
3677.78.70.0/2377.78.70.1 to 77.78.71.25477.78.71.255510
3777.78.72.0/2377.78.72.1 to 77.78.73.25477.78.73.255510
3877.78.74.0/2377.78.74.1 to 77.78.75.25477.78.75.255510
3977.78.76.0/2377.78.76.1 to 77.78.77.25477.78.77.255510
4077.78.78.0/2377.78.78.1 to 77.78.79.25477.78.79.255510
4177.78.80.0/2377.78.80.1 to 77.78.81.25477.78.81.255510
4277.78.82.0/2377.78.82.1 to 77.78.83.25477.78.83.255510
4377.78.84.0/2377.78.84.1 to 77.78.85.25477.78.85.255510
4477.78.86.0/2377.78.86.1 to 77.78.87.25477.78.87.255510
4577.78.88.0/2377.78.88.1 to 77.78.89.25477.78.89.255510
4677.78.90.0/2377.78.90.1 to 77.78.91.25477.78.91.255510
4777.78.92.0/2377.78.92.1 to 77.78.93.25477.78.93.255510
4877.78.94.0/2377.78.94.1 to 77.78.95.25477.78.95.255510
4977.78.96.0/2377.78.96.1 to 77.78.97.25477.78.97.255510
5077.78.98.0/2377.78.98.1 to 77.78.99.25477.78.99.255510
5177.78.100.0/2377.78.100.1 to 77.78.101.25477.78.101.255510
5277.78.102.0/2377.78.102.1 to 77.78.103.25477.78.103.255510
5377.78.104.0/2377.78.104.1 to 77.78.105.25477.78.105.255510
5477.78.106.0/2377.78.106.1 to 77.78.107.25477.78.107.255510
5577.78.108.0/2377.78.108.1 to 77.78.109.25477.78.109.255510
5677.78.110.0/2377.78.110.1 to 77.78.111.25477.78.111.255510
5777.78.112.0/2377.78.112.1 to 77.78.113.25477.78.113.255510
5877.78.114.0/2377.78.114.1 to 77.78.115.25477.78.115.255510
5977.78.116.0/2377.78.116.1 to 77.78.117.25477.78.117.255510
6077.78.118.0/2377.78.118.1 to 77.78.119.25477.78.119.255510
6177.78.120.0/2377.78.120.1 to 77.78.121.25477.78.121.255510
6277.78.122.0/2377.78.122.1 to 77.78.123.25477.78.123.255510
6377.78.124.0/2377.78.124.1 to 77.78.125.25477.78.125.255510
6477.78.126.0/2377.78.126.1 to 77.78.127.25477.78.127.255510

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.