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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.

Network184.71.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
184.71.0.0
Broadcast address
184.71.127.255
First usable
184.71.0.1
Last usable
184.71.127.254
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
B (default /16)
As numbers
Hex B8470000 · Integer 3091660800 to 3091693567
Reverse DNS zones
0.71.184.in-addr.arpa
1.71.184.in-addr.arpa
2.71.184.in-addr.arpa
3.71.184.in-addr.arpa
4.71.184.in-addr.arpa
5.71.184.in-addr.arpa
6.71.184.in-addr.arpa
7.71.184.in-addr.arpa
8.71.184.in-addr.arpa
9.71.184.in-addr.arpa
10.71.184.in-addr.arpa
11.71.184.in-addr.arpa
12.71.184.in-addr.arpa
13.71.184.in-addr.arpa
14.71.184.in-addr.arpa
15.71.184.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
Address10111000.01000111.00000000.00000000184.71.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network10111000.01000111.00000000.00000000184.71.0.0
Broadcast10111000.01000111.01111111.11111111184.71.127.255
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)

184.71.0.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1184.71.0.0/24184.71.0.1 to 184.71.0.254184.71.0.255254
2184.71.1.0/24184.71.1.1 to 184.71.1.254184.71.1.255254
3184.71.2.0/24184.71.2.1 to 184.71.2.254184.71.2.255254
4184.71.3.0/24184.71.3.1 to 184.71.3.254184.71.3.255254
5184.71.4.0/24184.71.4.1 to 184.71.4.254184.71.4.255254
6184.71.5.0/24184.71.5.1 to 184.71.5.254184.71.5.255254
7184.71.6.0/24184.71.6.1 to 184.71.6.254184.71.6.255254
8184.71.7.0/24184.71.7.1 to 184.71.7.254184.71.7.255254
9184.71.8.0/24184.71.8.1 to 184.71.8.254184.71.8.255254
10184.71.9.0/24184.71.9.1 to 184.71.9.254184.71.9.255254
11184.71.10.0/24184.71.10.1 to 184.71.10.254184.71.10.255254
12184.71.11.0/24184.71.11.1 to 184.71.11.254184.71.11.255254
13184.71.12.0/24184.71.12.1 to 184.71.12.254184.71.12.255254
14184.71.13.0/24184.71.13.1 to 184.71.13.254184.71.13.255254
15184.71.14.0/24184.71.14.1 to 184.71.14.254184.71.14.255254
16184.71.15.0/24184.71.15.1 to 184.71.15.254184.71.15.255254
17184.71.16.0/24184.71.16.1 to 184.71.16.254184.71.16.255254
18184.71.17.0/24184.71.17.1 to 184.71.17.254184.71.17.255254
19184.71.18.0/24184.71.18.1 to 184.71.18.254184.71.18.255254
20184.71.19.0/24184.71.19.1 to 184.71.19.254184.71.19.255254
21184.71.20.0/24184.71.20.1 to 184.71.20.254184.71.20.255254
22184.71.21.0/24184.71.21.1 to 184.71.21.254184.71.21.255254
23184.71.22.0/24184.71.22.1 to 184.71.22.254184.71.22.255254
24184.71.23.0/24184.71.23.1 to 184.71.23.254184.71.23.255254
25184.71.24.0/24184.71.24.1 to 184.71.24.254184.71.24.255254
26184.71.25.0/24184.71.25.1 to 184.71.25.254184.71.25.255254
27184.71.26.0/24184.71.26.1 to 184.71.26.254184.71.26.255254
28184.71.27.0/24184.71.27.1 to 184.71.27.254184.71.27.255254
29184.71.28.0/24184.71.28.1 to 184.71.28.254184.71.28.255254
30184.71.29.0/24184.71.29.1 to 184.71.29.254184.71.29.255254
31184.71.30.0/24184.71.30.1 to 184.71.30.254184.71.30.255254
32184.71.31.0/24184.71.31.1 to 184.71.31.254184.71.31.255254
33184.71.32.0/24184.71.32.1 to 184.71.32.254184.71.32.255254
34184.71.33.0/24184.71.33.1 to 184.71.33.254184.71.33.255254
35184.71.34.0/24184.71.34.1 to 184.71.34.254184.71.34.255254
36184.71.35.0/24184.71.35.1 to 184.71.35.254184.71.35.255254
37184.71.36.0/24184.71.36.1 to 184.71.36.254184.71.36.255254
38184.71.37.0/24184.71.37.1 to 184.71.37.254184.71.37.255254
39184.71.38.0/24184.71.38.1 to 184.71.38.254184.71.38.255254
40184.71.39.0/24184.71.39.1 to 184.71.39.254184.71.39.255254
41184.71.40.0/24184.71.40.1 to 184.71.40.254184.71.40.255254
42184.71.41.0/24184.71.41.1 to 184.71.41.254184.71.41.255254
43184.71.42.0/24184.71.42.1 to 184.71.42.254184.71.42.255254
44184.71.43.0/24184.71.43.1 to 184.71.43.254184.71.43.255254
45184.71.44.0/24184.71.44.1 to 184.71.44.254184.71.44.255254
46184.71.45.0/24184.71.45.1 to 184.71.45.254184.71.45.255254
47184.71.46.0/24184.71.46.1 to 184.71.46.254184.71.46.255254
48184.71.47.0/24184.71.47.1 to 184.71.47.254184.71.47.255254
49184.71.48.0/24184.71.48.1 to 184.71.48.254184.71.48.255254
50184.71.49.0/24184.71.49.1 to 184.71.49.254184.71.49.255254
51184.71.50.0/24184.71.50.1 to 184.71.50.254184.71.50.255254
52184.71.51.0/24184.71.51.1 to 184.71.51.254184.71.51.255254
53184.71.52.0/24184.71.52.1 to 184.71.52.254184.71.52.255254
54184.71.53.0/24184.71.53.1 to 184.71.53.254184.71.53.255254
55184.71.54.0/24184.71.54.1 to 184.71.54.254184.71.54.255254
56184.71.55.0/24184.71.55.1 to 184.71.55.254184.71.55.255254
57184.71.56.0/24184.71.56.1 to 184.71.56.254184.71.56.255254
58184.71.57.0/24184.71.57.1 to 184.71.57.254184.71.57.255254
59184.71.58.0/24184.71.58.1 to 184.71.58.254184.71.58.255254
60184.71.59.0/24184.71.59.1 to 184.71.59.254184.71.59.255254
61184.71.60.0/24184.71.60.1 to 184.71.60.254184.71.60.255254
62184.71.61.0/24184.71.61.1 to 184.71.61.254184.71.61.255254
63184.71.62.0/24184.71.62.1 to 184.71.62.254184.71.62.255254
64184.71.63.0/24184.71.63.1 to 184.71.63.254184.71.63.255254
65184.71.64.0/24184.71.64.1 to 184.71.64.254184.71.64.255254
66184.71.65.0/24184.71.65.1 to 184.71.65.254184.71.65.255254
67184.71.66.0/24184.71.66.1 to 184.71.66.254184.71.66.255254
68184.71.67.0/24184.71.67.1 to 184.71.67.254184.71.67.255254
69184.71.68.0/24184.71.68.1 to 184.71.68.254184.71.68.255254
70184.71.69.0/24184.71.69.1 to 184.71.69.254184.71.69.255254
71184.71.70.0/24184.71.70.1 to 184.71.70.254184.71.70.255254
72184.71.71.0/24184.71.71.1 to 184.71.71.254184.71.71.255254
73184.71.72.0/24184.71.72.1 to 184.71.72.254184.71.72.255254
74184.71.73.0/24184.71.73.1 to 184.71.73.254184.71.73.255254
75184.71.74.0/24184.71.74.1 to 184.71.74.254184.71.74.255254
76184.71.75.0/24184.71.75.1 to 184.71.75.254184.71.75.255254
77184.71.76.0/24184.71.76.1 to 184.71.76.254184.71.76.255254
78184.71.77.0/24184.71.77.1 to 184.71.77.254184.71.77.255254
79184.71.78.0/24184.71.78.1 to 184.71.78.254184.71.78.255254
80184.71.79.0/24184.71.79.1 to 184.71.79.254184.71.79.255254
81184.71.80.0/24184.71.80.1 to 184.71.80.254184.71.80.255254
82184.71.81.0/24184.71.81.1 to 184.71.81.254184.71.81.255254
83184.71.82.0/24184.71.82.1 to 184.71.82.254184.71.82.255254
84184.71.83.0/24184.71.83.1 to 184.71.83.254184.71.83.255254
85184.71.84.0/24184.71.84.1 to 184.71.84.254184.71.84.255254
86184.71.85.0/24184.71.85.1 to 184.71.85.254184.71.85.255254
87184.71.86.0/24184.71.86.1 to 184.71.86.254184.71.86.255254
88184.71.87.0/24184.71.87.1 to 184.71.87.254184.71.87.255254
89184.71.88.0/24184.71.88.1 to 184.71.88.254184.71.88.255254
90184.71.89.0/24184.71.89.1 to 184.71.89.254184.71.89.255254
91184.71.90.0/24184.71.90.1 to 184.71.90.254184.71.90.255254
92184.71.91.0/24184.71.91.1 to 184.71.91.254184.71.91.255254
93184.71.92.0/24184.71.92.1 to 184.71.92.254184.71.92.255254
94184.71.93.0/24184.71.93.1 to 184.71.93.254184.71.93.255254
95184.71.94.0/24184.71.94.1 to 184.71.94.254184.71.94.255254
96184.71.95.0/24184.71.95.1 to 184.71.95.254184.71.95.255254
97184.71.96.0/24184.71.96.1 to 184.71.96.254184.71.96.255254
98184.71.97.0/24184.71.97.1 to 184.71.97.254184.71.97.255254
99184.71.98.0/24184.71.98.1 to 184.71.98.254184.71.98.255254
100184.71.99.0/24184.71.99.1 to 184.71.99.254184.71.99.255254
101184.71.100.0/24184.71.100.1 to 184.71.100.254184.71.100.255254
102184.71.101.0/24184.71.101.1 to 184.71.101.254184.71.101.255254
103184.71.102.0/24184.71.102.1 to 184.71.102.254184.71.102.255254
104184.71.103.0/24184.71.103.1 to 184.71.103.254184.71.103.255254
105184.71.104.0/24184.71.104.1 to 184.71.104.254184.71.104.255254
106184.71.105.0/24184.71.105.1 to 184.71.105.254184.71.105.255254
107184.71.106.0/24184.71.106.1 to 184.71.106.254184.71.106.255254
108184.71.107.0/24184.71.107.1 to 184.71.107.254184.71.107.255254
109184.71.108.0/24184.71.108.1 to 184.71.108.254184.71.108.255254
110184.71.109.0/24184.71.109.1 to 184.71.109.254184.71.109.255254
111184.71.110.0/24184.71.110.1 to 184.71.110.254184.71.110.255254
112184.71.111.0/24184.71.111.1 to 184.71.111.254184.71.111.255254
113184.71.112.0/24184.71.112.1 to 184.71.112.254184.71.112.255254
114184.71.113.0/24184.71.113.1 to 184.71.113.254184.71.113.255254
115184.71.114.0/24184.71.114.1 to 184.71.114.254184.71.114.255254
116184.71.115.0/24184.71.115.1 to 184.71.115.254184.71.115.255254
117184.71.116.0/24184.71.116.1 to 184.71.116.254184.71.116.255254
118184.71.117.0/24184.71.117.1 to 184.71.117.254184.71.117.255254
119184.71.118.0/24184.71.118.1 to 184.71.118.254184.71.118.255254
120184.71.119.0/24184.71.119.1 to 184.71.119.254184.71.119.255254
121184.71.120.0/24184.71.120.1 to 184.71.120.254184.71.120.255254
122184.71.121.0/24184.71.121.1 to 184.71.121.254184.71.121.255254
123184.71.122.0/24184.71.122.1 to 184.71.122.254184.71.122.255254
124184.71.123.0/24184.71.123.1 to 184.71.123.254184.71.123.255254
125184.71.124.0/24184.71.124.1 to 184.71.124.254184.71.124.255254
126184.71.125.0/24184.71.125.1 to 184.71.125.254184.71.125.255254
127184.71.126.0/24184.71.126.1 to 184.71.126.254184.71.126.255254
128184.71.127.0/24184.71.127.1 to 184.71.127.254184.71.127.255254

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.