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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.

Network234.166.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
234.166.0.0
Broadcast address
234.166.127.255
First usable
234.166.0.1
Last usable
234.166.127.254
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
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex EAA60000 · Integer 3936747520 to 3936780287
Reverse DNS zones
0.166.234.in-addr.arpa
1.166.234.in-addr.arpa
2.166.234.in-addr.arpa
3.166.234.in-addr.arpa
4.166.234.in-addr.arpa
5.166.234.in-addr.arpa
6.166.234.in-addr.arpa
7.166.234.in-addr.arpa
8.166.234.in-addr.arpa
9.166.234.in-addr.arpa
10.166.234.in-addr.arpa
11.166.234.in-addr.arpa
12.166.234.in-addr.arpa
13.166.234.in-addr.arpa
14.166.234.in-addr.arpa
15.166.234.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
Address11101010.10100110.00000000.00000000234.166.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network11101010.10100110.00000000.00000000234.166.0.0
Broadcast11101010.10100110.01111111.11111111234.166.127.255
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)

234.166.0.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1234.166.0.0/24234.166.0.1 to 234.166.0.254234.166.0.255254
2234.166.1.0/24234.166.1.1 to 234.166.1.254234.166.1.255254
3234.166.2.0/24234.166.2.1 to 234.166.2.254234.166.2.255254
4234.166.3.0/24234.166.3.1 to 234.166.3.254234.166.3.255254
5234.166.4.0/24234.166.4.1 to 234.166.4.254234.166.4.255254
6234.166.5.0/24234.166.5.1 to 234.166.5.254234.166.5.255254
7234.166.6.0/24234.166.6.1 to 234.166.6.254234.166.6.255254
8234.166.7.0/24234.166.7.1 to 234.166.7.254234.166.7.255254
9234.166.8.0/24234.166.8.1 to 234.166.8.254234.166.8.255254
10234.166.9.0/24234.166.9.1 to 234.166.9.254234.166.9.255254
11234.166.10.0/24234.166.10.1 to 234.166.10.254234.166.10.255254
12234.166.11.0/24234.166.11.1 to 234.166.11.254234.166.11.255254
13234.166.12.0/24234.166.12.1 to 234.166.12.254234.166.12.255254
14234.166.13.0/24234.166.13.1 to 234.166.13.254234.166.13.255254
15234.166.14.0/24234.166.14.1 to 234.166.14.254234.166.14.255254
16234.166.15.0/24234.166.15.1 to 234.166.15.254234.166.15.255254
17234.166.16.0/24234.166.16.1 to 234.166.16.254234.166.16.255254
18234.166.17.0/24234.166.17.1 to 234.166.17.254234.166.17.255254
19234.166.18.0/24234.166.18.1 to 234.166.18.254234.166.18.255254
20234.166.19.0/24234.166.19.1 to 234.166.19.254234.166.19.255254
21234.166.20.0/24234.166.20.1 to 234.166.20.254234.166.20.255254
22234.166.21.0/24234.166.21.1 to 234.166.21.254234.166.21.255254
23234.166.22.0/24234.166.22.1 to 234.166.22.254234.166.22.255254
24234.166.23.0/24234.166.23.1 to 234.166.23.254234.166.23.255254
25234.166.24.0/24234.166.24.1 to 234.166.24.254234.166.24.255254
26234.166.25.0/24234.166.25.1 to 234.166.25.254234.166.25.255254
27234.166.26.0/24234.166.26.1 to 234.166.26.254234.166.26.255254
28234.166.27.0/24234.166.27.1 to 234.166.27.254234.166.27.255254
29234.166.28.0/24234.166.28.1 to 234.166.28.254234.166.28.255254
30234.166.29.0/24234.166.29.1 to 234.166.29.254234.166.29.255254
31234.166.30.0/24234.166.30.1 to 234.166.30.254234.166.30.255254
32234.166.31.0/24234.166.31.1 to 234.166.31.254234.166.31.255254
33234.166.32.0/24234.166.32.1 to 234.166.32.254234.166.32.255254
34234.166.33.0/24234.166.33.1 to 234.166.33.254234.166.33.255254
35234.166.34.0/24234.166.34.1 to 234.166.34.254234.166.34.255254
36234.166.35.0/24234.166.35.1 to 234.166.35.254234.166.35.255254
37234.166.36.0/24234.166.36.1 to 234.166.36.254234.166.36.255254
38234.166.37.0/24234.166.37.1 to 234.166.37.254234.166.37.255254
39234.166.38.0/24234.166.38.1 to 234.166.38.254234.166.38.255254
40234.166.39.0/24234.166.39.1 to 234.166.39.254234.166.39.255254
41234.166.40.0/24234.166.40.1 to 234.166.40.254234.166.40.255254
42234.166.41.0/24234.166.41.1 to 234.166.41.254234.166.41.255254
43234.166.42.0/24234.166.42.1 to 234.166.42.254234.166.42.255254
44234.166.43.0/24234.166.43.1 to 234.166.43.254234.166.43.255254
45234.166.44.0/24234.166.44.1 to 234.166.44.254234.166.44.255254
46234.166.45.0/24234.166.45.1 to 234.166.45.254234.166.45.255254
47234.166.46.0/24234.166.46.1 to 234.166.46.254234.166.46.255254
48234.166.47.0/24234.166.47.1 to 234.166.47.254234.166.47.255254
49234.166.48.0/24234.166.48.1 to 234.166.48.254234.166.48.255254
50234.166.49.0/24234.166.49.1 to 234.166.49.254234.166.49.255254
51234.166.50.0/24234.166.50.1 to 234.166.50.254234.166.50.255254
52234.166.51.0/24234.166.51.1 to 234.166.51.254234.166.51.255254
53234.166.52.0/24234.166.52.1 to 234.166.52.254234.166.52.255254
54234.166.53.0/24234.166.53.1 to 234.166.53.254234.166.53.255254
55234.166.54.0/24234.166.54.1 to 234.166.54.254234.166.54.255254
56234.166.55.0/24234.166.55.1 to 234.166.55.254234.166.55.255254
57234.166.56.0/24234.166.56.1 to 234.166.56.254234.166.56.255254
58234.166.57.0/24234.166.57.1 to 234.166.57.254234.166.57.255254
59234.166.58.0/24234.166.58.1 to 234.166.58.254234.166.58.255254
60234.166.59.0/24234.166.59.1 to 234.166.59.254234.166.59.255254
61234.166.60.0/24234.166.60.1 to 234.166.60.254234.166.60.255254
62234.166.61.0/24234.166.61.1 to 234.166.61.254234.166.61.255254
63234.166.62.0/24234.166.62.1 to 234.166.62.254234.166.62.255254
64234.166.63.0/24234.166.63.1 to 234.166.63.254234.166.63.255254
65234.166.64.0/24234.166.64.1 to 234.166.64.254234.166.64.255254
66234.166.65.0/24234.166.65.1 to 234.166.65.254234.166.65.255254
67234.166.66.0/24234.166.66.1 to 234.166.66.254234.166.66.255254
68234.166.67.0/24234.166.67.1 to 234.166.67.254234.166.67.255254
69234.166.68.0/24234.166.68.1 to 234.166.68.254234.166.68.255254
70234.166.69.0/24234.166.69.1 to 234.166.69.254234.166.69.255254
71234.166.70.0/24234.166.70.1 to 234.166.70.254234.166.70.255254
72234.166.71.0/24234.166.71.1 to 234.166.71.254234.166.71.255254
73234.166.72.0/24234.166.72.1 to 234.166.72.254234.166.72.255254
74234.166.73.0/24234.166.73.1 to 234.166.73.254234.166.73.255254
75234.166.74.0/24234.166.74.1 to 234.166.74.254234.166.74.255254
76234.166.75.0/24234.166.75.1 to 234.166.75.254234.166.75.255254
77234.166.76.0/24234.166.76.1 to 234.166.76.254234.166.76.255254
78234.166.77.0/24234.166.77.1 to 234.166.77.254234.166.77.255254
79234.166.78.0/24234.166.78.1 to 234.166.78.254234.166.78.255254
80234.166.79.0/24234.166.79.1 to 234.166.79.254234.166.79.255254
81234.166.80.0/24234.166.80.1 to 234.166.80.254234.166.80.255254
82234.166.81.0/24234.166.81.1 to 234.166.81.254234.166.81.255254
83234.166.82.0/24234.166.82.1 to 234.166.82.254234.166.82.255254
84234.166.83.0/24234.166.83.1 to 234.166.83.254234.166.83.255254
85234.166.84.0/24234.166.84.1 to 234.166.84.254234.166.84.255254
86234.166.85.0/24234.166.85.1 to 234.166.85.254234.166.85.255254
87234.166.86.0/24234.166.86.1 to 234.166.86.254234.166.86.255254
88234.166.87.0/24234.166.87.1 to 234.166.87.254234.166.87.255254
89234.166.88.0/24234.166.88.1 to 234.166.88.254234.166.88.255254
90234.166.89.0/24234.166.89.1 to 234.166.89.254234.166.89.255254
91234.166.90.0/24234.166.90.1 to 234.166.90.254234.166.90.255254
92234.166.91.0/24234.166.91.1 to 234.166.91.254234.166.91.255254
93234.166.92.0/24234.166.92.1 to 234.166.92.254234.166.92.255254
94234.166.93.0/24234.166.93.1 to 234.166.93.254234.166.93.255254
95234.166.94.0/24234.166.94.1 to 234.166.94.254234.166.94.255254
96234.166.95.0/24234.166.95.1 to 234.166.95.254234.166.95.255254
97234.166.96.0/24234.166.96.1 to 234.166.96.254234.166.96.255254
98234.166.97.0/24234.166.97.1 to 234.166.97.254234.166.97.255254
99234.166.98.0/24234.166.98.1 to 234.166.98.254234.166.98.255254
100234.166.99.0/24234.166.99.1 to 234.166.99.254234.166.99.255254
101234.166.100.0/24234.166.100.1 to 234.166.100.254234.166.100.255254
102234.166.101.0/24234.166.101.1 to 234.166.101.254234.166.101.255254
103234.166.102.0/24234.166.102.1 to 234.166.102.254234.166.102.255254
104234.166.103.0/24234.166.103.1 to 234.166.103.254234.166.103.255254
105234.166.104.0/24234.166.104.1 to 234.166.104.254234.166.104.255254
106234.166.105.0/24234.166.105.1 to 234.166.105.254234.166.105.255254
107234.166.106.0/24234.166.106.1 to 234.166.106.254234.166.106.255254
108234.166.107.0/24234.166.107.1 to 234.166.107.254234.166.107.255254
109234.166.108.0/24234.166.108.1 to 234.166.108.254234.166.108.255254
110234.166.109.0/24234.166.109.1 to 234.166.109.254234.166.109.255254
111234.166.110.0/24234.166.110.1 to 234.166.110.254234.166.110.255254
112234.166.111.0/24234.166.111.1 to 234.166.111.254234.166.111.255254
113234.166.112.0/24234.166.112.1 to 234.166.112.254234.166.112.255254
114234.166.113.0/24234.166.113.1 to 234.166.113.254234.166.113.255254
115234.166.114.0/24234.166.114.1 to 234.166.114.254234.166.114.255254
116234.166.115.0/24234.166.115.1 to 234.166.115.254234.166.115.255254
117234.166.116.0/24234.166.116.1 to 234.166.116.254234.166.116.255254
118234.166.117.0/24234.166.117.1 to 234.166.117.254234.166.117.255254
119234.166.118.0/24234.166.118.1 to 234.166.118.254234.166.118.255254
120234.166.119.0/24234.166.119.1 to 234.166.119.254234.166.119.255254
121234.166.120.0/24234.166.120.1 to 234.166.120.254234.166.120.255254
122234.166.121.0/24234.166.121.1 to 234.166.121.254234.166.121.255254
123234.166.122.0/24234.166.122.1 to 234.166.122.254234.166.122.255254
124234.166.123.0/24234.166.123.1 to 234.166.123.254234.166.123.255254
125234.166.124.0/24234.166.124.1 to 234.166.124.254234.166.124.255254
126234.166.125.0/24234.166.125.1 to 234.166.125.254234.166.125.255254
127234.166.126.0/24234.166.126.1 to 234.166.126.254234.166.126.255254
128234.166.127.0/24234.166.127.1 to 234.166.127.254234.166.127.255254

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.