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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/14
Addresses2^114
/64 networks2^50
Network
fc68::/14
First address
fc68::
Last address
fc6b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
20,769,187,434,139,310,514,121,985,316,880,384 (2^114)
/64 networks (LANs)
1,125,899,906,842,624 (2^50)
Full form
fc68:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zones
8.6.c.f.ip6.arpa
9.6.c.f.ip6.arpa
a.6.c.f.ip6.arpa
b.6.c.f.ip6.arpa
/14 is not on a 4-bit boundary, so it takes 4 /16 zones.
Split into smaller subnets/20
/15 (2)/16 (4)/17 (8)/18 (16)/20 (64)/24 (1,024)/28 (16,384)

fc68::/14 makes 64 subnets of /20.

Subnets
#SubnetLast address
1fc68::/20fc68:fff:ffff:ffff:ffff:ffff:ffff:ffff
2fc68:1000::/20fc68:1fff:ffff:ffff:ffff:ffff:ffff:ffff
3fc68:2000::/20fc68:2fff:ffff:ffff:ffff:ffff:ffff:ffff
4fc68:3000::/20fc68:3fff:ffff:ffff:ffff:ffff:ffff:ffff
5fc68:4000::/20fc68:4fff:ffff:ffff:ffff:ffff:ffff:ffff
6fc68:5000::/20fc68:5fff:ffff:ffff:ffff:ffff:ffff:ffff
7fc68:6000::/20fc68:6fff:ffff:ffff:ffff:ffff:ffff:ffff
8fc68:7000::/20fc68:7fff:ffff:ffff:ffff:ffff:ffff:ffff
9fc68:8000::/20fc68:8fff:ffff:ffff:ffff:ffff:ffff:ffff
10fc68:9000::/20fc68:9fff:ffff:ffff:ffff:ffff:ffff:ffff
11fc68:a000::/20fc68:afff:ffff:ffff:ffff:ffff:ffff:ffff
12fc68:b000::/20fc68:bfff:ffff:ffff:ffff:ffff:ffff:ffff
13fc68:c000::/20fc68:cfff:ffff:ffff:ffff:ffff:ffff:ffff
14fc68:d000::/20fc68:dfff:ffff:ffff:ffff:ffff:ffff:ffff
15fc68:e000::/20fc68:efff:ffff:ffff:ffff:ffff:ffff:ffff
16fc68:f000::/20fc68:ffff:ffff:ffff:ffff:ffff:ffff:ffff
17fc69::/20fc69:fff:ffff:ffff:ffff:ffff:ffff:ffff
18fc69:1000::/20fc69:1fff:ffff:ffff:ffff:ffff:ffff:ffff
19fc69:2000::/20fc69:2fff:ffff:ffff:ffff:ffff:ffff:ffff
20fc69:3000::/20fc69:3fff:ffff:ffff:ffff:ffff:ffff:ffff
21fc69:4000::/20fc69:4fff:ffff:ffff:ffff:ffff:ffff:ffff
22fc69:5000::/20fc69:5fff:ffff:ffff:ffff:ffff:ffff:ffff
23fc69:6000::/20fc69:6fff:ffff:ffff:ffff:ffff:ffff:ffff
24fc69:7000::/20fc69:7fff:ffff:ffff:ffff:ffff:ffff:ffff
25fc69:8000::/20fc69:8fff:ffff:ffff:ffff:ffff:ffff:ffff
26fc69:9000::/20fc69:9fff:ffff:ffff:ffff:ffff:ffff:ffff
27fc69:a000::/20fc69:afff:ffff:ffff:ffff:ffff:ffff:ffff
28fc69:b000::/20fc69:bfff:ffff:ffff:ffff:ffff:ffff:ffff
29fc69:c000::/20fc69:cfff:ffff:ffff:ffff:ffff:ffff:ffff
30fc69:d000::/20fc69:dfff:ffff:ffff:ffff:ffff:ffff:ffff
31fc69:e000::/20fc69:efff:ffff:ffff:ffff:ffff:ffff:ffff
32fc69:f000::/20fc69:ffff:ffff:ffff:ffff:ffff:ffff:ffff
33fc6a::/20fc6a:fff:ffff:ffff:ffff:ffff:ffff:ffff
34fc6a:1000::/20fc6a:1fff:ffff:ffff:ffff:ffff:ffff:ffff
35fc6a:2000::/20fc6a:2fff:ffff:ffff:ffff:ffff:ffff:ffff
36fc6a:3000::/20fc6a:3fff:ffff:ffff:ffff:ffff:ffff:ffff
37fc6a:4000::/20fc6a:4fff:ffff:ffff:ffff:ffff:ffff:ffff
38fc6a:5000::/20fc6a:5fff:ffff:ffff:ffff:ffff:ffff:ffff
39fc6a:6000::/20fc6a:6fff:ffff:ffff:ffff:ffff:ffff:ffff
40fc6a:7000::/20fc6a:7fff:ffff:ffff:ffff:ffff:ffff:ffff
41fc6a:8000::/20fc6a:8fff:ffff:ffff:ffff:ffff:ffff:ffff
42fc6a:9000::/20fc6a:9fff:ffff:ffff:ffff:ffff:ffff:ffff
43fc6a:a000::/20fc6a:afff:ffff:ffff:ffff:ffff:ffff:ffff
44fc6a:b000::/20fc6a:bfff:ffff:ffff:ffff:ffff:ffff:ffff
45fc6a:c000::/20fc6a:cfff:ffff:ffff:ffff:ffff:ffff:ffff
46fc6a:d000::/20fc6a:dfff:ffff:ffff:ffff:ffff:ffff:ffff
47fc6a:e000::/20fc6a:efff:ffff:ffff:ffff:ffff:ffff:ffff
48fc6a:f000::/20fc6a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
49fc6b::/20fc6b:fff:ffff:ffff:ffff:ffff:ffff:ffff
50fc6b:1000::/20fc6b:1fff:ffff:ffff:ffff:ffff:ffff:ffff
51fc6b:2000::/20fc6b:2fff:ffff:ffff:ffff:ffff:ffff:ffff
52fc6b:3000::/20fc6b:3fff:ffff:ffff:ffff:ffff:ffff:ffff
53fc6b:4000::/20fc6b:4fff:ffff:ffff:ffff:ffff:ffff:ffff
54fc6b:5000::/20fc6b:5fff:ffff:ffff:ffff:ffff:ffff:ffff
55fc6b:6000::/20fc6b:6fff:ffff:ffff:ffff:ffff:ffff:ffff
56fc6b:7000::/20fc6b:7fff:ffff:ffff:ffff:ffff:ffff:ffff
57fc6b:8000::/20fc6b:8fff:ffff:ffff:ffff:ffff:ffff:ffff
58fc6b:9000::/20fc6b:9fff:ffff:ffff:ffff:ffff:ffff:ffff
59fc6b:a000::/20fc6b:afff:ffff:ffff:ffff:ffff:ffff:ffff
60fc6b:b000::/20fc6b:bfff:ffff:ffff:ffff:ffff:ffff:ffff
61fc6b:c000::/20fc6b:cfff:ffff:ffff:ffff:ffff:ffff:ffff
62fc6b:d000::/20fc6b:dfff:ffff:ffff:ffff:ffff:ffff:ffff
63fc6b:e000::/20fc6b:efff:ffff:ffff:ffff:ffff:ffff:ffff
64fc6b:f000::/20fc6b:ffff: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.