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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.

Network55.64.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
55.64.0.0
Broadcast address
55.64.127.255
First usable
55.64.0.1
Last usable
55.64.127.254
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 37400000 · Integer 926941184 to 926973951
Reverse DNS zones
0.64.55.in-addr.arpa
1.64.55.in-addr.arpa
2.64.55.in-addr.arpa
3.64.55.in-addr.arpa
4.64.55.in-addr.arpa
5.64.55.in-addr.arpa
6.64.55.in-addr.arpa
7.64.55.in-addr.arpa
8.64.55.in-addr.arpa
9.64.55.in-addr.arpa
10.64.55.in-addr.arpa
11.64.55.in-addr.arpa
12.64.55.in-addr.arpa
13.64.55.in-addr.arpa
14.64.55.in-addr.arpa
15.64.55.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
Address00110111.01000000.00000000.0000000055.64.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network00110111.01000000.00000000.0000000055.64.0.0
Broadcast00110111.01000000.01111111.1111111155.64.127.255
Split into smaller subnets/24
/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)

55.64.0.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
155.64.0.0/2455.64.0.1 to 55.64.0.25455.64.0.255254
255.64.1.0/2455.64.1.1 to 55.64.1.25455.64.1.255254
355.64.2.0/2455.64.2.1 to 55.64.2.25455.64.2.255254
455.64.3.0/2455.64.3.1 to 55.64.3.25455.64.3.255254
555.64.4.0/2455.64.4.1 to 55.64.4.25455.64.4.255254
655.64.5.0/2455.64.5.1 to 55.64.5.25455.64.5.255254
755.64.6.0/2455.64.6.1 to 55.64.6.25455.64.6.255254
855.64.7.0/2455.64.7.1 to 55.64.7.25455.64.7.255254
955.64.8.0/2455.64.8.1 to 55.64.8.25455.64.8.255254
1055.64.9.0/2455.64.9.1 to 55.64.9.25455.64.9.255254
1155.64.10.0/2455.64.10.1 to 55.64.10.25455.64.10.255254
1255.64.11.0/2455.64.11.1 to 55.64.11.25455.64.11.255254
1355.64.12.0/2455.64.12.1 to 55.64.12.25455.64.12.255254
1455.64.13.0/2455.64.13.1 to 55.64.13.25455.64.13.255254
1555.64.14.0/2455.64.14.1 to 55.64.14.25455.64.14.255254
1655.64.15.0/2455.64.15.1 to 55.64.15.25455.64.15.255254
1755.64.16.0/2455.64.16.1 to 55.64.16.25455.64.16.255254
1855.64.17.0/2455.64.17.1 to 55.64.17.25455.64.17.255254
1955.64.18.0/2455.64.18.1 to 55.64.18.25455.64.18.255254
2055.64.19.0/2455.64.19.1 to 55.64.19.25455.64.19.255254
2155.64.20.0/2455.64.20.1 to 55.64.20.25455.64.20.255254
2255.64.21.0/2455.64.21.1 to 55.64.21.25455.64.21.255254
2355.64.22.0/2455.64.22.1 to 55.64.22.25455.64.22.255254
2455.64.23.0/2455.64.23.1 to 55.64.23.25455.64.23.255254
2555.64.24.0/2455.64.24.1 to 55.64.24.25455.64.24.255254
2655.64.25.0/2455.64.25.1 to 55.64.25.25455.64.25.255254
2755.64.26.0/2455.64.26.1 to 55.64.26.25455.64.26.255254
2855.64.27.0/2455.64.27.1 to 55.64.27.25455.64.27.255254
2955.64.28.0/2455.64.28.1 to 55.64.28.25455.64.28.255254
3055.64.29.0/2455.64.29.1 to 55.64.29.25455.64.29.255254
3155.64.30.0/2455.64.30.1 to 55.64.30.25455.64.30.255254
3255.64.31.0/2455.64.31.1 to 55.64.31.25455.64.31.255254
3355.64.32.0/2455.64.32.1 to 55.64.32.25455.64.32.255254
3455.64.33.0/2455.64.33.1 to 55.64.33.25455.64.33.255254
3555.64.34.0/2455.64.34.1 to 55.64.34.25455.64.34.255254
3655.64.35.0/2455.64.35.1 to 55.64.35.25455.64.35.255254
3755.64.36.0/2455.64.36.1 to 55.64.36.25455.64.36.255254
3855.64.37.0/2455.64.37.1 to 55.64.37.25455.64.37.255254
3955.64.38.0/2455.64.38.1 to 55.64.38.25455.64.38.255254
4055.64.39.0/2455.64.39.1 to 55.64.39.25455.64.39.255254
4155.64.40.0/2455.64.40.1 to 55.64.40.25455.64.40.255254
4255.64.41.0/2455.64.41.1 to 55.64.41.25455.64.41.255254
4355.64.42.0/2455.64.42.1 to 55.64.42.25455.64.42.255254
4455.64.43.0/2455.64.43.1 to 55.64.43.25455.64.43.255254
4555.64.44.0/2455.64.44.1 to 55.64.44.25455.64.44.255254
4655.64.45.0/2455.64.45.1 to 55.64.45.25455.64.45.255254
4755.64.46.0/2455.64.46.1 to 55.64.46.25455.64.46.255254
4855.64.47.0/2455.64.47.1 to 55.64.47.25455.64.47.255254
4955.64.48.0/2455.64.48.1 to 55.64.48.25455.64.48.255254
5055.64.49.0/2455.64.49.1 to 55.64.49.25455.64.49.255254
5155.64.50.0/2455.64.50.1 to 55.64.50.25455.64.50.255254
5255.64.51.0/2455.64.51.1 to 55.64.51.25455.64.51.255254
5355.64.52.0/2455.64.52.1 to 55.64.52.25455.64.52.255254
5455.64.53.0/2455.64.53.1 to 55.64.53.25455.64.53.255254
5555.64.54.0/2455.64.54.1 to 55.64.54.25455.64.54.255254
5655.64.55.0/2455.64.55.1 to 55.64.55.25455.64.55.255254
5755.64.56.0/2455.64.56.1 to 55.64.56.25455.64.56.255254
5855.64.57.0/2455.64.57.1 to 55.64.57.25455.64.57.255254
5955.64.58.0/2455.64.58.1 to 55.64.58.25455.64.58.255254
6055.64.59.0/2455.64.59.1 to 55.64.59.25455.64.59.255254
6155.64.60.0/2455.64.60.1 to 55.64.60.25455.64.60.255254
6255.64.61.0/2455.64.61.1 to 55.64.61.25455.64.61.255254
6355.64.62.0/2455.64.62.1 to 55.64.62.25455.64.62.255254
6455.64.63.0/2455.64.63.1 to 55.64.63.25455.64.63.255254
6555.64.64.0/2455.64.64.1 to 55.64.64.25455.64.64.255254
6655.64.65.0/2455.64.65.1 to 55.64.65.25455.64.65.255254
6755.64.66.0/2455.64.66.1 to 55.64.66.25455.64.66.255254
6855.64.67.0/2455.64.67.1 to 55.64.67.25455.64.67.255254
6955.64.68.0/2455.64.68.1 to 55.64.68.25455.64.68.255254
7055.64.69.0/2455.64.69.1 to 55.64.69.25455.64.69.255254
7155.64.70.0/2455.64.70.1 to 55.64.70.25455.64.70.255254
7255.64.71.0/2455.64.71.1 to 55.64.71.25455.64.71.255254
7355.64.72.0/2455.64.72.1 to 55.64.72.25455.64.72.255254
7455.64.73.0/2455.64.73.1 to 55.64.73.25455.64.73.255254
7555.64.74.0/2455.64.74.1 to 55.64.74.25455.64.74.255254
7655.64.75.0/2455.64.75.1 to 55.64.75.25455.64.75.255254
7755.64.76.0/2455.64.76.1 to 55.64.76.25455.64.76.255254
7855.64.77.0/2455.64.77.1 to 55.64.77.25455.64.77.255254
7955.64.78.0/2455.64.78.1 to 55.64.78.25455.64.78.255254
8055.64.79.0/2455.64.79.1 to 55.64.79.25455.64.79.255254
8155.64.80.0/2455.64.80.1 to 55.64.80.25455.64.80.255254
8255.64.81.0/2455.64.81.1 to 55.64.81.25455.64.81.255254
8355.64.82.0/2455.64.82.1 to 55.64.82.25455.64.82.255254
8455.64.83.0/2455.64.83.1 to 55.64.83.25455.64.83.255254
8555.64.84.0/2455.64.84.1 to 55.64.84.25455.64.84.255254
8655.64.85.0/2455.64.85.1 to 55.64.85.25455.64.85.255254
8755.64.86.0/2455.64.86.1 to 55.64.86.25455.64.86.255254
8855.64.87.0/2455.64.87.1 to 55.64.87.25455.64.87.255254
8955.64.88.0/2455.64.88.1 to 55.64.88.25455.64.88.255254
9055.64.89.0/2455.64.89.1 to 55.64.89.25455.64.89.255254
9155.64.90.0/2455.64.90.1 to 55.64.90.25455.64.90.255254
9255.64.91.0/2455.64.91.1 to 55.64.91.25455.64.91.255254
9355.64.92.0/2455.64.92.1 to 55.64.92.25455.64.92.255254
9455.64.93.0/2455.64.93.1 to 55.64.93.25455.64.93.255254
9555.64.94.0/2455.64.94.1 to 55.64.94.25455.64.94.255254
9655.64.95.0/2455.64.95.1 to 55.64.95.25455.64.95.255254
9755.64.96.0/2455.64.96.1 to 55.64.96.25455.64.96.255254
9855.64.97.0/2455.64.97.1 to 55.64.97.25455.64.97.255254
9955.64.98.0/2455.64.98.1 to 55.64.98.25455.64.98.255254
10055.64.99.0/2455.64.99.1 to 55.64.99.25455.64.99.255254
10155.64.100.0/2455.64.100.1 to 55.64.100.25455.64.100.255254
10255.64.101.0/2455.64.101.1 to 55.64.101.25455.64.101.255254
10355.64.102.0/2455.64.102.1 to 55.64.102.25455.64.102.255254
10455.64.103.0/2455.64.103.1 to 55.64.103.25455.64.103.255254
10555.64.104.0/2455.64.104.1 to 55.64.104.25455.64.104.255254
10655.64.105.0/2455.64.105.1 to 55.64.105.25455.64.105.255254
10755.64.106.0/2455.64.106.1 to 55.64.106.25455.64.106.255254
10855.64.107.0/2455.64.107.1 to 55.64.107.25455.64.107.255254
10955.64.108.0/2455.64.108.1 to 55.64.108.25455.64.108.255254
11055.64.109.0/2455.64.109.1 to 55.64.109.25455.64.109.255254
11155.64.110.0/2455.64.110.1 to 55.64.110.25455.64.110.255254
11255.64.111.0/2455.64.111.1 to 55.64.111.25455.64.111.255254
11355.64.112.0/2455.64.112.1 to 55.64.112.25455.64.112.255254
11455.64.113.0/2455.64.113.1 to 55.64.113.25455.64.113.255254
11555.64.114.0/2455.64.114.1 to 55.64.114.25455.64.114.255254
11655.64.115.0/2455.64.115.1 to 55.64.115.25455.64.115.255254
11755.64.116.0/2455.64.116.1 to 55.64.116.25455.64.116.255254
11855.64.117.0/2455.64.117.1 to 55.64.117.25455.64.117.255254
11955.64.118.0/2455.64.118.1 to 55.64.118.25455.64.118.255254
12055.64.119.0/2455.64.119.1 to 55.64.119.25455.64.119.255254
12155.64.120.0/2455.64.120.1 to 55.64.120.25455.64.120.255254
12255.64.121.0/2455.64.121.1 to 55.64.121.25455.64.121.255254
12355.64.122.0/2455.64.122.1 to 55.64.122.25455.64.122.255254
12455.64.123.0/2455.64.123.1 to 55.64.123.25455.64.123.255254
12555.64.124.0/2455.64.124.1 to 55.64.124.25455.64.124.255254
12655.64.125.0/2455.64.125.1 to 55.64.125.25455.64.125.255254
12755.64.126.0/2455.64.126.1 to 55.64.126.25455.64.126.255254
12855.64.127.0/2455.64.127.1 to 55.64.127.25455.64.127.255254

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.