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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
fc3d::/17
First address
fc3d::
Last address
fc3d: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
fc3d:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zones
0.d.3.c.f.ip6.arpa
1.d.3.c.f.ip6.arpa
2.d.3.c.f.ip6.arpa
3.d.3.c.f.ip6.arpa
4.d.3.c.f.ip6.arpa
5.d.3.c.f.ip6.arpa
6.d.3.c.f.ip6.arpa
7.d.3.c.f.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)

fc3d::/17 makes 128 subnets of /24.

Subnets
#SubnetLast address
1fc3d::/24fc3d:ff:ffff:ffff:ffff:ffff:ffff:ffff
2fc3d:100::/24fc3d:1ff:ffff:ffff:ffff:ffff:ffff:ffff
3fc3d:200::/24fc3d:2ff:ffff:ffff:ffff:ffff:ffff:ffff
4fc3d:300::/24fc3d:3ff:ffff:ffff:ffff:ffff:ffff:ffff
5fc3d:400::/24fc3d:4ff:ffff:ffff:ffff:ffff:ffff:ffff
6fc3d:500::/24fc3d:5ff:ffff:ffff:ffff:ffff:ffff:ffff
7fc3d:600::/24fc3d:6ff:ffff:ffff:ffff:ffff:ffff:ffff
8fc3d:700::/24fc3d:7ff:ffff:ffff:ffff:ffff:ffff:ffff
9fc3d:800::/24fc3d:8ff:ffff:ffff:ffff:ffff:ffff:ffff
10fc3d:900::/24fc3d:9ff:ffff:ffff:ffff:ffff:ffff:ffff
11fc3d:a00::/24fc3d:aff:ffff:ffff:ffff:ffff:ffff:ffff
12fc3d:b00::/24fc3d:bff:ffff:ffff:ffff:ffff:ffff:ffff
13fc3d:c00::/24fc3d:cff:ffff:ffff:ffff:ffff:ffff:ffff
14fc3d:d00::/24fc3d:dff:ffff:ffff:ffff:ffff:ffff:ffff
15fc3d:e00::/24fc3d:eff:ffff:ffff:ffff:ffff:ffff:ffff
16fc3d:f00::/24fc3d:fff:ffff:ffff:ffff:ffff:ffff:ffff
17fc3d:1000::/24fc3d:10ff:ffff:ffff:ffff:ffff:ffff:ffff
18fc3d:1100::/24fc3d:11ff:ffff:ffff:ffff:ffff:ffff:ffff
19fc3d:1200::/24fc3d:12ff:ffff:ffff:ffff:ffff:ffff:ffff
20fc3d:1300::/24fc3d:13ff:ffff:ffff:ffff:ffff:ffff:ffff
21fc3d:1400::/24fc3d:14ff:ffff:ffff:ffff:ffff:ffff:ffff
22fc3d:1500::/24fc3d:15ff:ffff:ffff:ffff:ffff:ffff:ffff
23fc3d:1600::/24fc3d:16ff:ffff:ffff:ffff:ffff:ffff:ffff
24fc3d:1700::/24fc3d:17ff:ffff:ffff:ffff:ffff:ffff:ffff
25fc3d:1800::/24fc3d:18ff:ffff:ffff:ffff:ffff:ffff:ffff
26fc3d:1900::/24fc3d:19ff:ffff:ffff:ffff:ffff:ffff:ffff
27fc3d:1a00::/24fc3d:1aff:ffff:ffff:ffff:ffff:ffff:ffff
28fc3d:1b00::/24fc3d:1bff:ffff:ffff:ffff:ffff:ffff:ffff
29fc3d:1c00::/24fc3d:1cff:ffff:ffff:ffff:ffff:ffff:ffff
30fc3d:1d00::/24fc3d:1dff:ffff:ffff:ffff:ffff:ffff:ffff
31fc3d:1e00::/24fc3d:1eff:ffff:ffff:ffff:ffff:ffff:ffff
32fc3d:1f00::/24fc3d:1fff:ffff:ffff:ffff:ffff:ffff:ffff
33fc3d:2000::/24fc3d:20ff:ffff:ffff:ffff:ffff:ffff:ffff
34fc3d:2100::/24fc3d:21ff:ffff:ffff:ffff:ffff:ffff:ffff
35fc3d:2200::/24fc3d:22ff:ffff:ffff:ffff:ffff:ffff:ffff
36fc3d:2300::/24fc3d:23ff:ffff:ffff:ffff:ffff:ffff:ffff
37fc3d:2400::/24fc3d:24ff:ffff:ffff:ffff:ffff:ffff:ffff
38fc3d:2500::/24fc3d:25ff:ffff:ffff:ffff:ffff:ffff:ffff
39fc3d:2600::/24fc3d:26ff:ffff:ffff:ffff:ffff:ffff:ffff
40fc3d:2700::/24fc3d:27ff:ffff:ffff:ffff:ffff:ffff:ffff
41fc3d:2800::/24fc3d:28ff:ffff:ffff:ffff:ffff:ffff:ffff
42fc3d:2900::/24fc3d:29ff:ffff:ffff:ffff:ffff:ffff:ffff
43fc3d:2a00::/24fc3d:2aff:ffff:ffff:ffff:ffff:ffff:ffff
44fc3d:2b00::/24fc3d:2bff:ffff:ffff:ffff:ffff:ffff:ffff
45fc3d:2c00::/24fc3d:2cff:ffff:ffff:ffff:ffff:ffff:ffff
46fc3d:2d00::/24fc3d:2dff:ffff:ffff:ffff:ffff:ffff:ffff
47fc3d:2e00::/24fc3d:2eff:ffff:ffff:ffff:ffff:ffff:ffff
48fc3d:2f00::/24fc3d:2fff:ffff:ffff:ffff:ffff:ffff:ffff
49fc3d:3000::/24fc3d:30ff:ffff:ffff:ffff:ffff:ffff:ffff
50fc3d:3100::/24fc3d:31ff:ffff:ffff:ffff:ffff:ffff:ffff
51fc3d:3200::/24fc3d:32ff:ffff:ffff:ffff:ffff:ffff:ffff
52fc3d:3300::/24fc3d:33ff:ffff:ffff:ffff:ffff:ffff:ffff
53fc3d:3400::/24fc3d:34ff:ffff:ffff:ffff:ffff:ffff:ffff
54fc3d:3500::/24fc3d:35ff:ffff:ffff:ffff:ffff:ffff:ffff
55fc3d:3600::/24fc3d:36ff:ffff:ffff:ffff:ffff:ffff:ffff
56fc3d:3700::/24fc3d:37ff:ffff:ffff:ffff:ffff:ffff:ffff
57fc3d:3800::/24fc3d:38ff:ffff:ffff:ffff:ffff:ffff:ffff
58fc3d:3900::/24fc3d:39ff:ffff:ffff:ffff:ffff:ffff:ffff
59fc3d:3a00::/24fc3d:3aff:ffff:ffff:ffff:ffff:ffff:ffff
60fc3d:3b00::/24fc3d:3bff:ffff:ffff:ffff:ffff:ffff:ffff
61fc3d:3c00::/24fc3d:3cff:ffff:ffff:ffff:ffff:ffff:ffff
62fc3d:3d00::/24fc3d:3dff:ffff:ffff:ffff:ffff:ffff:ffff
63fc3d:3e00::/24fc3d:3eff:ffff:ffff:ffff:ffff:ffff:ffff
64fc3d:3f00::/24fc3d:3fff:ffff:ffff:ffff:ffff:ffff:ffff
65fc3d:4000::/24fc3d:40ff:ffff:ffff:ffff:ffff:ffff:ffff
66fc3d:4100::/24fc3d:41ff:ffff:ffff:ffff:ffff:ffff:ffff
67fc3d:4200::/24fc3d:42ff:ffff:ffff:ffff:ffff:ffff:ffff
68fc3d:4300::/24fc3d:43ff:ffff:ffff:ffff:ffff:ffff:ffff
69fc3d:4400::/24fc3d:44ff:ffff:ffff:ffff:ffff:ffff:ffff
70fc3d:4500::/24fc3d:45ff:ffff:ffff:ffff:ffff:ffff:ffff
71fc3d:4600::/24fc3d:46ff:ffff:ffff:ffff:ffff:ffff:ffff
72fc3d:4700::/24fc3d:47ff:ffff:ffff:ffff:ffff:ffff:ffff
73fc3d:4800::/24fc3d:48ff:ffff:ffff:ffff:ffff:ffff:ffff
74fc3d:4900::/24fc3d:49ff:ffff:ffff:ffff:ffff:ffff:ffff
75fc3d:4a00::/24fc3d:4aff:ffff:ffff:ffff:ffff:ffff:ffff
76fc3d:4b00::/24fc3d:4bff:ffff:ffff:ffff:ffff:ffff:ffff
77fc3d:4c00::/24fc3d:4cff:ffff:ffff:ffff:ffff:ffff:ffff
78fc3d:4d00::/24fc3d:4dff:ffff:ffff:ffff:ffff:ffff:ffff
79fc3d:4e00::/24fc3d:4eff:ffff:ffff:ffff:ffff:ffff:ffff
80fc3d:4f00::/24fc3d:4fff:ffff:ffff:ffff:ffff:ffff:ffff
81fc3d:5000::/24fc3d:50ff:ffff:ffff:ffff:ffff:ffff:ffff
82fc3d:5100::/24fc3d:51ff:ffff:ffff:ffff:ffff:ffff:ffff
83fc3d:5200::/24fc3d:52ff:ffff:ffff:ffff:ffff:ffff:ffff
84fc3d:5300::/24fc3d:53ff:ffff:ffff:ffff:ffff:ffff:ffff
85fc3d:5400::/24fc3d:54ff:ffff:ffff:ffff:ffff:ffff:ffff
86fc3d:5500::/24fc3d:55ff:ffff:ffff:ffff:ffff:ffff:ffff
87fc3d:5600::/24fc3d:56ff:ffff:ffff:ffff:ffff:ffff:ffff
88fc3d:5700::/24fc3d:57ff:ffff:ffff:ffff:ffff:ffff:ffff
89fc3d:5800::/24fc3d:58ff:ffff:ffff:ffff:ffff:ffff:ffff
90fc3d:5900::/24fc3d:59ff:ffff:ffff:ffff:ffff:ffff:ffff
91fc3d:5a00::/24fc3d:5aff:ffff:ffff:ffff:ffff:ffff:ffff
92fc3d:5b00::/24fc3d:5bff:ffff:ffff:ffff:ffff:ffff:ffff
93fc3d:5c00::/24fc3d:5cff:ffff:ffff:ffff:ffff:ffff:ffff
94fc3d:5d00::/24fc3d:5dff:ffff:ffff:ffff:ffff:ffff:ffff
95fc3d:5e00::/24fc3d:5eff:ffff:ffff:ffff:ffff:ffff:ffff
96fc3d:5f00::/24fc3d:5fff:ffff:ffff:ffff:ffff:ffff:ffff
97fc3d:6000::/24fc3d:60ff:ffff:ffff:ffff:ffff:ffff:ffff
98fc3d:6100::/24fc3d:61ff:ffff:ffff:ffff:ffff:ffff:ffff
99fc3d:6200::/24fc3d:62ff:ffff:ffff:ffff:ffff:ffff:ffff
100fc3d:6300::/24fc3d:63ff:ffff:ffff:ffff:ffff:ffff:ffff
101fc3d:6400::/24fc3d:64ff:ffff:ffff:ffff:ffff:ffff:ffff
102fc3d:6500::/24fc3d:65ff:ffff:ffff:ffff:ffff:ffff:ffff
103fc3d:6600::/24fc3d:66ff:ffff:ffff:ffff:ffff:ffff:ffff
104fc3d:6700::/24fc3d:67ff:ffff:ffff:ffff:ffff:ffff:ffff
105fc3d:6800::/24fc3d:68ff:ffff:ffff:ffff:ffff:ffff:ffff
106fc3d:6900::/24fc3d:69ff:ffff:ffff:ffff:ffff:ffff:ffff
107fc3d:6a00::/24fc3d:6aff:ffff:ffff:ffff:ffff:ffff:ffff
108fc3d:6b00::/24fc3d:6bff:ffff:ffff:ffff:ffff:ffff:ffff
109fc3d:6c00::/24fc3d:6cff:ffff:ffff:ffff:ffff:ffff:ffff
110fc3d:6d00::/24fc3d:6dff:ffff:ffff:ffff:ffff:ffff:ffff
111fc3d:6e00::/24fc3d:6eff:ffff:ffff:ffff:ffff:ffff:ffff
112fc3d:6f00::/24fc3d:6fff:ffff:ffff:ffff:ffff:ffff:ffff
113fc3d:7000::/24fc3d:70ff:ffff:ffff:ffff:ffff:ffff:ffff
114fc3d:7100::/24fc3d:71ff:ffff:ffff:ffff:ffff:ffff:ffff
115fc3d:7200::/24fc3d:72ff:ffff:ffff:ffff:ffff:ffff:ffff
116fc3d:7300::/24fc3d:73ff:ffff:ffff:ffff:ffff:ffff:ffff
117fc3d:7400::/24fc3d:74ff:ffff:ffff:ffff:ffff:ffff:ffff
118fc3d:7500::/24fc3d:75ff:ffff:ffff:ffff:ffff:ffff:ffff
119fc3d:7600::/24fc3d:76ff:ffff:ffff:ffff:ffff:ffff:ffff
120fc3d:7700::/24fc3d:77ff:ffff:ffff:ffff:ffff:ffff:ffff
121fc3d:7800::/24fc3d:78ff:ffff:ffff:ffff:ffff:ffff:ffff
122fc3d:7900::/24fc3d:79ff:ffff:ffff:ffff:ffff:ffff:ffff
123fc3d:7a00::/24fc3d:7aff:ffff:ffff:ffff:ffff:ffff:ffff
124fc3d:7b00::/24fc3d:7bff:ffff:ffff:ffff:ffff:ffff:ffff
125fc3d:7c00::/24fc3d:7cff:ffff:ffff:ffff:ffff:ffff:ffff
126fc3d:7d00::/24fc3d:7dff:ffff:ffff:ffff:ffff:ffff:ffff
127fc3d:7e00::/24fc3d:7eff:ffff:ffff:ffff:ffff:ffff:ffff
128fc3d:7f00::/24fc3d: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.