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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.

Prefix/17
Addresses2^111
/64 networks2^47
Network
261f::/17
First address
261f::
Last address
261f:7fff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
2,596,148,429,267,413,814,265,248,164,610,048 (2^111)
/64 networks (LANs)
140,737,488,355,328 (2^47)
Full form
261f:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zones
0.f.1.6.2.ip6.arpa
1.f.1.6.2.ip6.arpa
2.f.1.6.2.ip6.arpa
3.f.1.6.2.ip6.arpa
4.f.1.6.2.ip6.arpa
5.f.1.6.2.ip6.arpa
6.f.1.6.2.ip6.arpa
7.f.1.6.2.ip6.arpa
/17 is not on a 4-bit boundary, so it takes 8 /20 zones.
Split into smaller subnets/24
/18 (2)/19 (4)/20 (8)/21 (16)/24 (128)/28 (2,048)/32 (32,768)

261f::/17 makes 128 subnets of /24.

Subnets
#SubnetLast address
1261f::/24261f:ff:ffff:ffff:ffff:ffff:ffff:ffff
2261f:100::/24261f:1ff:ffff:ffff:ffff:ffff:ffff:ffff
3261f:200::/24261f:2ff:ffff:ffff:ffff:ffff:ffff:ffff
4261f:300::/24261f:3ff:ffff:ffff:ffff:ffff:ffff:ffff
5261f:400::/24261f:4ff:ffff:ffff:ffff:ffff:ffff:ffff
6261f:500::/24261f:5ff:ffff:ffff:ffff:ffff:ffff:ffff
7261f:600::/24261f:6ff:ffff:ffff:ffff:ffff:ffff:ffff
8261f:700::/24261f:7ff:ffff:ffff:ffff:ffff:ffff:ffff
9261f:800::/24261f:8ff:ffff:ffff:ffff:ffff:ffff:ffff
10261f:900::/24261f:9ff:ffff:ffff:ffff:ffff:ffff:ffff
11261f:a00::/24261f:aff:ffff:ffff:ffff:ffff:ffff:ffff
12261f:b00::/24261f:bff:ffff:ffff:ffff:ffff:ffff:ffff
13261f:c00::/24261f:cff:ffff:ffff:ffff:ffff:ffff:ffff
14261f:d00::/24261f:dff:ffff:ffff:ffff:ffff:ffff:ffff
15261f:e00::/24261f:eff:ffff:ffff:ffff:ffff:ffff:ffff
16261f:f00::/24261f:fff:ffff:ffff:ffff:ffff:ffff:ffff
17261f:1000::/24261f:10ff:ffff:ffff:ffff:ffff:ffff:ffff
18261f:1100::/24261f:11ff:ffff:ffff:ffff:ffff:ffff:ffff
19261f:1200::/24261f:12ff:ffff:ffff:ffff:ffff:ffff:ffff
20261f:1300::/24261f:13ff:ffff:ffff:ffff:ffff:ffff:ffff
21261f:1400::/24261f:14ff:ffff:ffff:ffff:ffff:ffff:ffff
22261f:1500::/24261f:15ff:ffff:ffff:ffff:ffff:ffff:ffff
23261f:1600::/24261f:16ff:ffff:ffff:ffff:ffff:ffff:ffff
24261f:1700::/24261f:17ff:ffff:ffff:ffff:ffff:ffff:ffff
25261f:1800::/24261f:18ff:ffff:ffff:ffff:ffff:ffff:ffff
26261f:1900::/24261f:19ff:ffff:ffff:ffff:ffff:ffff:ffff
27261f:1a00::/24261f:1aff:ffff:ffff:ffff:ffff:ffff:ffff
28261f:1b00::/24261f:1bff:ffff:ffff:ffff:ffff:ffff:ffff
29261f:1c00::/24261f:1cff:ffff:ffff:ffff:ffff:ffff:ffff
30261f:1d00::/24261f:1dff:ffff:ffff:ffff:ffff:ffff:ffff
31261f:1e00::/24261f:1eff:ffff:ffff:ffff:ffff:ffff:ffff
32261f:1f00::/24261f:1fff:ffff:ffff:ffff:ffff:ffff:ffff
33261f:2000::/24261f:20ff:ffff:ffff:ffff:ffff:ffff:ffff
34261f:2100::/24261f:21ff:ffff:ffff:ffff:ffff:ffff:ffff
35261f:2200::/24261f:22ff:ffff:ffff:ffff:ffff:ffff:ffff
36261f:2300::/24261f:23ff:ffff:ffff:ffff:ffff:ffff:ffff
37261f:2400::/24261f:24ff:ffff:ffff:ffff:ffff:ffff:ffff
38261f:2500::/24261f:25ff:ffff:ffff:ffff:ffff:ffff:ffff
39261f:2600::/24261f:26ff:ffff:ffff:ffff:ffff:ffff:ffff
40261f:2700::/24261f:27ff:ffff:ffff:ffff:ffff:ffff:ffff
41261f:2800::/24261f:28ff:ffff:ffff:ffff:ffff:ffff:ffff
42261f:2900::/24261f:29ff:ffff:ffff:ffff:ffff:ffff:ffff
43261f:2a00::/24261f:2aff:ffff:ffff:ffff:ffff:ffff:ffff
44261f:2b00::/24261f:2bff:ffff:ffff:ffff:ffff:ffff:ffff
45261f:2c00::/24261f:2cff:ffff:ffff:ffff:ffff:ffff:ffff
46261f:2d00::/24261f:2dff:ffff:ffff:ffff:ffff:ffff:ffff
47261f:2e00::/24261f:2eff:ffff:ffff:ffff:ffff:ffff:ffff
48261f:2f00::/24261f:2fff:ffff:ffff:ffff:ffff:ffff:ffff
49261f:3000::/24261f:30ff:ffff:ffff:ffff:ffff:ffff:ffff
50261f:3100::/24261f:31ff:ffff:ffff:ffff:ffff:ffff:ffff
51261f:3200::/24261f:32ff:ffff:ffff:ffff:ffff:ffff:ffff
52261f:3300::/24261f:33ff:ffff:ffff:ffff:ffff:ffff:ffff
53261f:3400::/24261f:34ff:ffff:ffff:ffff:ffff:ffff:ffff
54261f:3500::/24261f:35ff:ffff:ffff:ffff:ffff:ffff:ffff
55261f:3600::/24261f:36ff:ffff:ffff:ffff:ffff:ffff:ffff
56261f:3700::/24261f:37ff:ffff:ffff:ffff:ffff:ffff:ffff
57261f:3800::/24261f:38ff:ffff:ffff:ffff:ffff:ffff:ffff
58261f:3900::/24261f:39ff:ffff:ffff:ffff:ffff:ffff:ffff
59261f:3a00::/24261f:3aff:ffff:ffff:ffff:ffff:ffff:ffff
60261f:3b00::/24261f:3bff:ffff:ffff:ffff:ffff:ffff:ffff
61261f:3c00::/24261f:3cff:ffff:ffff:ffff:ffff:ffff:ffff
62261f:3d00::/24261f:3dff:ffff:ffff:ffff:ffff:ffff:ffff
63261f:3e00::/24261f:3eff:ffff:ffff:ffff:ffff:ffff:ffff
64261f:3f00::/24261f:3fff:ffff:ffff:ffff:ffff:ffff:ffff
65261f:4000::/24261f:40ff:ffff:ffff:ffff:ffff:ffff:ffff
66261f:4100::/24261f:41ff:ffff:ffff:ffff:ffff:ffff:ffff
67261f:4200::/24261f:42ff:ffff:ffff:ffff:ffff:ffff:ffff
68261f:4300::/24261f:43ff:ffff:ffff:ffff:ffff:ffff:ffff
69261f:4400::/24261f:44ff:ffff:ffff:ffff:ffff:ffff:ffff
70261f:4500::/24261f:45ff:ffff:ffff:ffff:ffff:ffff:ffff
71261f:4600::/24261f:46ff:ffff:ffff:ffff:ffff:ffff:ffff
72261f:4700::/24261f:47ff:ffff:ffff:ffff:ffff:ffff:ffff
73261f:4800::/24261f:48ff:ffff:ffff:ffff:ffff:ffff:ffff
74261f:4900::/24261f:49ff:ffff:ffff:ffff:ffff:ffff:ffff
75261f:4a00::/24261f:4aff:ffff:ffff:ffff:ffff:ffff:ffff
76261f:4b00::/24261f:4bff:ffff:ffff:ffff:ffff:ffff:ffff
77261f:4c00::/24261f:4cff:ffff:ffff:ffff:ffff:ffff:ffff
78261f:4d00::/24261f:4dff:ffff:ffff:ffff:ffff:ffff:ffff
79261f:4e00::/24261f:4eff:ffff:ffff:ffff:ffff:ffff:ffff
80261f:4f00::/24261f:4fff:ffff:ffff:ffff:ffff:ffff:ffff
81261f:5000::/24261f:50ff:ffff:ffff:ffff:ffff:ffff:ffff
82261f:5100::/24261f:51ff:ffff:ffff:ffff:ffff:ffff:ffff
83261f:5200::/24261f:52ff:ffff:ffff:ffff:ffff:ffff:ffff
84261f:5300::/24261f:53ff:ffff:ffff:ffff:ffff:ffff:ffff
85261f:5400::/24261f:54ff:ffff:ffff:ffff:ffff:ffff:ffff
86261f:5500::/24261f:55ff:ffff:ffff:ffff:ffff:ffff:ffff
87261f:5600::/24261f:56ff:ffff:ffff:ffff:ffff:ffff:ffff
88261f:5700::/24261f:57ff:ffff:ffff:ffff:ffff:ffff:ffff
89261f:5800::/24261f:58ff:ffff:ffff:ffff:ffff:ffff:ffff
90261f:5900::/24261f:59ff:ffff:ffff:ffff:ffff:ffff:ffff
91261f:5a00::/24261f:5aff:ffff:ffff:ffff:ffff:ffff:ffff
92261f:5b00::/24261f:5bff:ffff:ffff:ffff:ffff:ffff:ffff
93261f:5c00::/24261f:5cff:ffff:ffff:ffff:ffff:ffff:ffff
94261f:5d00::/24261f:5dff:ffff:ffff:ffff:ffff:ffff:ffff
95261f:5e00::/24261f:5eff:ffff:ffff:ffff:ffff:ffff:ffff
96261f:5f00::/24261f:5fff:ffff:ffff:ffff:ffff:ffff:ffff
97261f:6000::/24261f:60ff:ffff:ffff:ffff:ffff:ffff:ffff
98261f:6100::/24261f:61ff:ffff:ffff:ffff:ffff:ffff:ffff
99261f:6200::/24261f:62ff:ffff:ffff:ffff:ffff:ffff:ffff
100261f:6300::/24261f:63ff:ffff:ffff:ffff:ffff:ffff:ffff
101261f:6400::/24261f:64ff:ffff:ffff:ffff:ffff:ffff:ffff
102261f:6500::/24261f:65ff:ffff:ffff:ffff:ffff:ffff:ffff
103261f:6600::/24261f:66ff:ffff:ffff:ffff:ffff:ffff:ffff
104261f:6700::/24261f:67ff:ffff:ffff:ffff:ffff:ffff:ffff
105261f:6800::/24261f:68ff:ffff:ffff:ffff:ffff:ffff:ffff
106261f:6900::/24261f:69ff:ffff:ffff:ffff:ffff:ffff:ffff
107261f:6a00::/24261f:6aff:ffff:ffff:ffff:ffff:ffff:ffff
108261f:6b00::/24261f:6bff:ffff:ffff:ffff:ffff:ffff:ffff
109261f:6c00::/24261f:6cff:ffff:ffff:ffff:ffff:ffff:ffff
110261f:6d00::/24261f:6dff:ffff:ffff:ffff:ffff:ffff:ffff
111261f:6e00::/24261f:6eff:ffff:ffff:ffff:ffff:ffff:ffff
112261f:6f00::/24261f:6fff:ffff:ffff:ffff:ffff:ffff:ffff
113261f:7000::/24261f:70ff:ffff:ffff:ffff:ffff:ffff:ffff
114261f:7100::/24261f:71ff:ffff:ffff:ffff:ffff:ffff:ffff
115261f:7200::/24261f:72ff:ffff:ffff:ffff:ffff:ffff:ffff
116261f:7300::/24261f:73ff:ffff:ffff:ffff:ffff:ffff:ffff
117261f:7400::/24261f:74ff:ffff:ffff:ffff:ffff:ffff:ffff
118261f:7500::/24261f:75ff:ffff:ffff:ffff:ffff:ffff:ffff
119261f:7600::/24261f:76ff:ffff:ffff:ffff:ffff:ffff:ffff
120261f:7700::/24261f:77ff:ffff:ffff:ffff:ffff:ffff:ffff
121261f:7800::/24261f:78ff:ffff:ffff:ffff:ffff:ffff:ffff
122261f:7900::/24261f:79ff:ffff:ffff:ffff:ffff:ffff:ffff
123261f:7a00::/24261f:7aff:ffff:ffff:ffff:ffff:ffff:ffff
124261f:7b00::/24261f:7bff:ffff:ffff:ffff:ffff:ffff:ffff
125261f:7c00::/24261f:7cff:ffff:ffff:ffff:ffff:ffff:ffff
126261f:7d00::/24261f:7dff:ffff:ffff:ffff:ffff:ffff:ffff
127261f:7e00::/24261f:7eff:ffff:ffff:ffff:ffff:ffff:ffff
128261f:7f00::/24261f:7fff:ffff:ffff:ffff:ffff:ffff:ffff

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.