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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.

Network49.2.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
49.2.0.0
Broadcast address
49.2.127.255
First usable
49.2.0.1
Last usable
49.2.127.254
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 31020000 · Integer 822214656 to 822247423
Reverse DNS zones
0.2.49.in-addr.arpa
1.2.49.in-addr.arpa
2.2.49.in-addr.arpa
3.2.49.in-addr.arpa
4.2.49.in-addr.arpa
5.2.49.in-addr.arpa
6.2.49.in-addr.arpa
7.2.49.in-addr.arpa
8.2.49.in-addr.arpa
9.2.49.in-addr.arpa
10.2.49.in-addr.arpa
11.2.49.in-addr.arpa
12.2.49.in-addr.arpa
13.2.49.in-addr.arpa
14.2.49.in-addr.arpa
15.2.49.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
Address00110001.00000010.00000000.0000000049.2.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network00110001.00000010.00000000.0000000049.2.0.0
Broadcast00110001.00000010.01111111.1111111149.2.127.255
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)

49.2.0.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
149.2.0.0/2449.2.0.1 to 49.2.0.25449.2.0.255254
249.2.1.0/2449.2.1.1 to 49.2.1.25449.2.1.255254
349.2.2.0/2449.2.2.1 to 49.2.2.25449.2.2.255254
449.2.3.0/2449.2.3.1 to 49.2.3.25449.2.3.255254
549.2.4.0/2449.2.4.1 to 49.2.4.25449.2.4.255254
649.2.5.0/2449.2.5.1 to 49.2.5.25449.2.5.255254
749.2.6.0/2449.2.6.1 to 49.2.6.25449.2.6.255254
849.2.7.0/2449.2.7.1 to 49.2.7.25449.2.7.255254
949.2.8.0/2449.2.8.1 to 49.2.8.25449.2.8.255254
1049.2.9.0/2449.2.9.1 to 49.2.9.25449.2.9.255254
1149.2.10.0/2449.2.10.1 to 49.2.10.25449.2.10.255254
1249.2.11.0/2449.2.11.1 to 49.2.11.25449.2.11.255254
1349.2.12.0/2449.2.12.1 to 49.2.12.25449.2.12.255254
1449.2.13.0/2449.2.13.1 to 49.2.13.25449.2.13.255254
1549.2.14.0/2449.2.14.1 to 49.2.14.25449.2.14.255254
1649.2.15.0/2449.2.15.1 to 49.2.15.25449.2.15.255254
1749.2.16.0/2449.2.16.1 to 49.2.16.25449.2.16.255254
1849.2.17.0/2449.2.17.1 to 49.2.17.25449.2.17.255254
1949.2.18.0/2449.2.18.1 to 49.2.18.25449.2.18.255254
2049.2.19.0/2449.2.19.1 to 49.2.19.25449.2.19.255254
2149.2.20.0/2449.2.20.1 to 49.2.20.25449.2.20.255254
2249.2.21.0/2449.2.21.1 to 49.2.21.25449.2.21.255254
2349.2.22.0/2449.2.22.1 to 49.2.22.25449.2.22.255254
2449.2.23.0/2449.2.23.1 to 49.2.23.25449.2.23.255254
2549.2.24.0/2449.2.24.1 to 49.2.24.25449.2.24.255254
2649.2.25.0/2449.2.25.1 to 49.2.25.25449.2.25.255254
2749.2.26.0/2449.2.26.1 to 49.2.26.25449.2.26.255254
2849.2.27.0/2449.2.27.1 to 49.2.27.25449.2.27.255254
2949.2.28.0/2449.2.28.1 to 49.2.28.25449.2.28.255254
3049.2.29.0/2449.2.29.1 to 49.2.29.25449.2.29.255254
3149.2.30.0/2449.2.30.1 to 49.2.30.25449.2.30.255254
3249.2.31.0/2449.2.31.1 to 49.2.31.25449.2.31.255254
3349.2.32.0/2449.2.32.1 to 49.2.32.25449.2.32.255254
3449.2.33.0/2449.2.33.1 to 49.2.33.25449.2.33.255254
3549.2.34.0/2449.2.34.1 to 49.2.34.25449.2.34.255254
3649.2.35.0/2449.2.35.1 to 49.2.35.25449.2.35.255254
3749.2.36.0/2449.2.36.1 to 49.2.36.25449.2.36.255254
3849.2.37.0/2449.2.37.1 to 49.2.37.25449.2.37.255254
3949.2.38.0/2449.2.38.1 to 49.2.38.25449.2.38.255254
4049.2.39.0/2449.2.39.1 to 49.2.39.25449.2.39.255254
4149.2.40.0/2449.2.40.1 to 49.2.40.25449.2.40.255254
4249.2.41.0/2449.2.41.1 to 49.2.41.25449.2.41.255254
4349.2.42.0/2449.2.42.1 to 49.2.42.25449.2.42.255254
4449.2.43.0/2449.2.43.1 to 49.2.43.25449.2.43.255254
4549.2.44.0/2449.2.44.1 to 49.2.44.25449.2.44.255254
4649.2.45.0/2449.2.45.1 to 49.2.45.25449.2.45.255254
4749.2.46.0/2449.2.46.1 to 49.2.46.25449.2.46.255254
4849.2.47.0/2449.2.47.1 to 49.2.47.25449.2.47.255254
4949.2.48.0/2449.2.48.1 to 49.2.48.25449.2.48.255254
5049.2.49.0/2449.2.49.1 to 49.2.49.25449.2.49.255254
5149.2.50.0/2449.2.50.1 to 49.2.50.25449.2.50.255254
5249.2.51.0/2449.2.51.1 to 49.2.51.25449.2.51.255254
5349.2.52.0/2449.2.52.1 to 49.2.52.25449.2.52.255254
5449.2.53.0/2449.2.53.1 to 49.2.53.25449.2.53.255254
5549.2.54.0/2449.2.54.1 to 49.2.54.25449.2.54.255254
5649.2.55.0/2449.2.55.1 to 49.2.55.25449.2.55.255254
5749.2.56.0/2449.2.56.1 to 49.2.56.25449.2.56.255254
5849.2.57.0/2449.2.57.1 to 49.2.57.25449.2.57.255254
5949.2.58.0/2449.2.58.1 to 49.2.58.25449.2.58.255254
6049.2.59.0/2449.2.59.1 to 49.2.59.25449.2.59.255254
6149.2.60.0/2449.2.60.1 to 49.2.60.25449.2.60.255254
6249.2.61.0/2449.2.61.1 to 49.2.61.25449.2.61.255254
6349.2.62.0/2449.2.62.1 to 49.2.62.25449.2.62.255254
6449.2.63.0/2449.2.63.1 to 49.2.63.25449.2.63.255254
6549.2.64.0/2449.2.64.1 to 49.2.64.25449.2.64.255254
6649.2.65.0/2449.2.65.1 to 49.2.65.25449.2.65.255254
6749.2.66.0/2449.2.66.1 to 49.2.66.25449.2.66.255254
6849.2.67.0/2449.2.67.1 to 49.2.67.25449.2.67.255254
6949.2.68.0/2449.2.68.1 to 49.2.68.25449.2.68.255254
7049.2.69.0/2449.2.69.1 to 49.2.69.25449.2.69.255254
7149.2.70.0/2449.2.70.1 to 49.2.70.25449.2.70.255254
7249.2.71.0/2449.2.71.1 to 49.2.71.25449.2.71.255254
7349.2.72.0/2449.2.72.1 to 49.2.72.25449.2.72.255254
7449.2.73.0/2449.2.73.1 to 49.2.73.25449.2.73.255254
7549.2.74.0/2449.2.74.1 to 49.2.74.25449.2.74.255254
7649.2.75.0/2449.2.75.1 to 49.2.75.25449.2.75.255254
7749.2.76.0/2449.2.76.1 to 49.2.76.25449.2.76.255254
7849.2.77.0/2449.2.77.1 to 49.2.77.25449.2.77.255254
7949.2.78.0/2449.2.78.1 to 49.2.78.25449.2.78.255254
8049.2.79.0/2449.2.79.1 to 49.2.79.25449.2.79.255254
8149.2.80.0/2449.2.80.1 to 49.2.80.25449.2.80.255254
8249.2.81.0/2449.2.81.1 to 49.2.81.25449.2.81.255254
8349.2.82.0/2449.2.82.1 to 49.2.82.25449.2.82.255254
8449.2.83.0/2449.2.83.1 to 49.2.83.25449.2.83.255254
8549.2.84.0/2449.2.84.1 to 49.2.84.25449.2.84.255254
8649.2.85.0/2449.2.85.1 to 49.2.85.25449.2.85.255254
8749.2.86.0/2449.2.86.1 to 49.2.86.25449.2.86.255254
8849.2.87.0/2449.2.87.1 to 49.2.87.25449.2.87.255254
8949.2.88.0/2449.2.88.1 to 49.2.88.25449.2.88.255254
9049.2.89.0/2449.2.89.1 to 49.2.89.25449.2.89.255254
9149.2.90.0/2449.2.90.1 to 49.2.90.25449.2.90.255254
9249.2.91.0/2449.2.91.1 to 49.2.91.25449.2.91.255254
9349.2.92.0/2449.2.92.1 to 49.2.92.25449.2.92.255254
9449.2.93.0/2449.2.93.1 to 49.2.93.25449.2.93.255254
9549.2.94.0/2449.2.94.1 to 49.2.94.25449.2.94.255254
9649.2.95.0/2449.2.95.1 to 49.2.95.25449.2.95.255254
9749.2.96.0/2449.2.96.1 to 49.2.96.25449.2.96.255254
9849.2.97.0/2449.2.97.1 to 49.2.97.25449.2.97.255254
9949.2.98.0/2449.2.98.1 to 49.2.98.25449.2.98.255254
10049.2.99.0/2449.2.99.1 to 49.2.99.25449.2.99.255254
10149.2.100.0/2449.2.100.1 to 49.2.100.25449.2.100.255254
10249.2.101.0/2449.2.101.1 to 49.2.101.25449.2.101.255254
10349.2.102.0/2449.2.102.1 to 49.2.102.25449.2.102.255254
10449.2.103.0/2449.2.103.1 to 49.2.103.25449.2.103.255254
10549.2.104.0/2449.2.104.1 to 49.2.104.25449.2.104.255254
10649.2.105.0/2449.2.105.1 to 49.2.105.25449.2.105.255254
10749.2.106.0/2449.2.106.1 to 49.2.106.25449.2.106.255254
10849.2.107.0/2449.2.107.1 to 49.2.107.25449.2.107.255254
10949.2.108.0/2449.2.108.1 to 49.2.108.25449.2.108.255254
11049.2.109.0/2449.2.109.1 to 49.2.109.25449.2.109.255254
11149.2.110.0/2449.2.110.1 to 49.2.110.25449.2.110.255254
11249.2.111.0/2449.2.111.1 to 49.2.111.25449.2.111.255254
11349.2.112.0/2449.2.112.1 to 49.2.112.25449.2.112.255254
11449.2.113.0/2449.2.113.1 to 49.2.113.25449.2.113.255254
11549.2.114.0/2449.2.114.1 to 49.2.114.25449.2.114.255254
11649.2.115.0/2449.2.115.1 to 49.2.115.25449.2.115.255254
11749.2.116.0/2449.2.116.1 to 49.2.116.25449.2.116.255254
11849.2.117.0/2449.2.117.1 to 49.2.117.25449.2.117.255254
11949.2.118.0/2449.2.118.1 to 49.2.118.25449.2.118.255254
12049.2.119.0/2449.2.119.1 to 49.2.119.25449.2.119.255254
12149.2.120.0/2449.2.120.1 to 49.2.120.25449.2.120.255254
12249.2.121.0/2449.2.121.1 to 49.2.121.25449.2.121.255254
12349.2.122.0/2449.2.122.1 to 49.2.122.25449.2.122.255254
12449.2.123.0/2449.2.123.1 to 49.2.123.25449.2.123.255254
12549.2.124.0/2449.2.124.1 to 49.2.124.25449.2.124.255254
12649.2.125.0/2449.2.125.1 to 49.2.125.25449.2.125.255254
12749.2.126.0/2449.2.126.1 to 49.2.126.25449.2.126.255254
12849.2.127.0/2449.2.127.1 to 49.2.127.25449.2.127.255254

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.