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Speed and call quality testTest delay, jitter and speed, with a focus on phone calls.My IP addressYour public IPv4 and IPv6 addresses, provider and address range.WhoIs lookupWho owns a domain or IP address, when it expires, and its DNS.DNS reportEvery DNS record for a domain, with email setup checked.IP subnet calculatorWork out a network's range, mask and hosts, and split it into subnets.

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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
28fa::/17
First address
28fa::
Last address
28fa: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
28fa:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zones
0.a.f.8.2.ip6.arpa
1.a.f.8.2.ip6.arpa
2.a.f.8.2.ip6.arpa
3.a.f.8.2.ip6.arpa
4.a.f.8.2.ip6.arpa
5.a.f.8.2.ip6.arpa
6.a.f.8.2.ip6.arpa
7.a.f.8.2.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)

28fa::/17 makes 128 subnets of /24.

Subnets
#SubnetLast address
128fa::/2428fa:ff:ffff:ffff:ffff:ffff:ffff:ffff
228fa:100::/2428fa:1ff:ffff:ffff:ffff:ffff:ffff:ffff
328fa:200::/2428fa:2ff:ffff:ffff:ffff:ffff:ffff:ffff
428fa:300::/2428fa:3ff:ffff:ffff:ffff:ffff:ffff:ffff
528fa:400::/2428fa:4ff:ffff:ffff:ffff:ffff:ffff:ffff
628fa:500::/2428fa:5ff:ffff:ffff:ffff:ffff:ffff:ffff
728fa:600::/2428fa:6ff:ffff:ffff:ffff:ffff:ffff:ffff
828fa:700::/2428fa:7ff:ffff:ffff:ffff:ffff:ffff:ffff
928fa:800::/2428fa:8ff:ffff:ffff:ffff:ffff:ffff:ffff
1028fa:900::/2428fa:9ff:ffff:ffff:ffff:ffff:ffff:ffff
1128fa:a00::/2428fa:aff:ffff:ffff:ffff:ffff:ffff:ffff
1228fa:b00::/2428fa:bff:ffff:ffff:ffff:ffff:ffff:ffff
1328fa:c00::/2428fa:cff:ffff:ffff:ffff:ffff:ffff:ffff
1428fa:d00::/2428fa:dff:ffff:ffff:ffff:ffff:ffff:ffff
1528fa:e00::/2428fa:eff:ffff:ffff:ffff:ffff:ffff:ffff
1628fa:f00::/2428fa:fff:ffff:ffff:ffff:ffff:ffff:ffff
1728fa:1000::/2428fa:10ff:ffff:ffff:ffff:ffff:ffff:ffff
1828fa:1100::/2428fa:11ff:ffff:ffff:ffff:ffff:ffff:ffff
1928fa:1200::/2428fa:12ff:ffff:ffff:ffff:ffff:ffff:ffff
2028fa:1300::/2428fa:13ff:ffff:ffff:ffff:ffff:ffff:ffff
2128fa:1400::/2428fa:14ff:ffff:ffff:ffff:ffff:ffff:ffff
2228fa:1500::/2428fa:15ff:ffff:ffff:ffff:ffff:ffff:ffff
2328fa:1600::/2428fa:16ff:ffff:ffff:ffff:ffff:ffff:ffff
2428fa:1700::/2428fa:17ff:ffff:ffff:ffff:ffff:ffff:ffff
2528fa:1800::/2428fa:18ff:ffff:ffff:ffff:ffff:ffff:ffff
2628fa:1900::/2428fa:19ff:ffff:ffff:ffff:ffff:ffff:ffff
2728fa:1a00::/2428fa:1aff:ffff:ffff:ffff:ffff:ffff:ffff
2828fa:1b00::/2428fa:1bff:ffff:ffff:ffff:ffff:ffff:ffff
2928fa:1c00::/2428fa:1cff:ffff:ffff:ffff:ffff:ffff:ffff
3028fa:1d00::/2428fa:1dff:ffff:ffff:ffff:ffff:ffff:ffff
3128fa:1e00::/2428fa:1eff:ffff:ffff:ffff:ffff:ffff:ffff
3228fa:1f00::/2428fa:1fff:ffff:ffff:ffff:ffff:ffff:ffff
3328fa:2000::/2428fa:20ff:ffff:ffff:ffff:ffff:ffff:ffff
3428fa:2100::/2428fa:21ff:ffff:ffff:ffff:ffff:ffff:ffff
3528fa:2200::/2428fa:22ff:ffff:ffff:ffff:ffff:ffff:ffff
3628fa:2300::/2428fa:23ff:ffff:ffff:ffff:ffff:ffff:ffff
3728fa:2400::/2428fa:24ff:ffff:ffff:ffff:ffff:ffff:ffff
3828fa:2500::/2428fa:25ff:ffff:ffff:ffff:ffff:ffff:ffff
3928fa:2600::/2428fa:26ff:ffff:ffff:ffff:ffff:ffff:ffff
4028fa:2700::/2428fa:27ff:ffff:ffff:ffff:ffff:ffff:ffff
4128fa:2800::/2428fa:28ff:ffff:ffff:ffff:ffff:ffff:ffff
4228fa:2900::/2428fa:29ff:ffff:ffff:ffff:ffff:ffff:ffff
4328fa:2a00::/2428fa:2aff:ffff:ffff:ffff:ffff:ffff:ffff
4428fa:2b00::/2428fa:2bff:ffff:ffff:ffff:ffff:ffff:ffff
4528fa:2c00::/2428fa:2cff:ffff:ffff:ffff:ffff:ffff:ffff
4628fa:2d00::/2428fa:2dff:ffff:ffff:ffff:ffff:ffff:ffff
4728fa:2e00::/2428fa:2eff:ffff:ffff:ffff:ffff:ffff:ffff
4828fa:2f00::/2428fa:2fff:ffff:ffff:ffff:ffff:ffff:ffff
4928fa:3000::/2428fa:30ff:ffff:ffff:ffff:ffff:ffff:ffff
5028fa:3100::/2428fa:31ff:ffff:ffff:ffff:ffff:ffff:ffff
5128fa:3200::/2428fa:32ff:ffff:ffff:ffff:ffff:ffff:ffff
5228fa:3300::/2428fa:33ff:ffff:ffff:ffff:ffff:ffff:ffff
5328fa:3400::/2428fa:34ff:ffff:ffff:ffff:ffff:ffff:ffff
5428fa:3500::/2428fa:35ff:ffff:ffff:ffff:ffff:ffff:ffff
5528fa:3600::/2428fa:36ff:ffff:ffff:ffff:ffff:ffff:ffff
5628fa:3700::/2428fa:37ff:ffff:ffff:ffff:ffff:ffff:ffff
5728fa:3800::/2428fa:38ff:ffff:ffff:ffff:ffff:ffff:ffff
5828fa:3900::/2428fa:39ff:ffff:ffff:ffff:ffff:ffff:ffff
5928fa:3a00::/2428fa:3aff:ffff:ffff:ffff:ffff:ffff:ffff
6028fa:3b00::/2428fa:3bff:ffff:ffff:ffff:ffff:ffff:ffff
6128fa:3c00::/2428fa:3cff:ffff:ffff:ffff:ffff:ffff:ffff
6228fa:3d00::/2428fa:3dff:ffff:ffff:ffff:ffff:ffff:ffff
6328fa:3e00::/2428fa:3eff:ffff:ffff:ffff:ffff:ffff:ffff
6428fa:3f00::/2428fa:3fff:ffff:ffff:ffff:ffff:ffff:ffff
6528fa:4000::/2428fa:40ff:ffff:ffff:ffff:ffff:ffff:ffff
6628fa:4100::/2428fa:41ff:ffff:ffff:ffff:ffff:ffff:ffff
6728fa:4200::/2428fa:42ff:ffff:ffff:ffff:ffff:ffff:ffff
6828fa:4300::/2428fa:43ff:ffff:ffff:ffff:ffff:ffff:ffff
6928fa:4400::/2428fa:44ff:ffff:ffff:ffff:ffff:ffff:ffff
7028fa:4500::/2428fa:45ff:ffff:ffff:ffff:ffff:ffff:ffff
7128fa:4600::/2428fa:46ff:ffff:ffff:ffff:ffff:ffff:ffff
7228fa:4700::/2428fa:47ff:ffff:ffff:ffff:ffff:ffff:ffff
7328fa:4800::/2428fa:48ff:ffff:ffff:ffff:ffff:ffff:ffff
7428fa:4900::/2428fa:49ff:ffff:ffff:ffff:ffff:ffff:ffff
7528fa:4a00::/2428fa:4aff:ffff:ffff:ffff:ffff:ffff:ffff
7628fa:4b00::/2428fa:4bff:ffff:ffff:ffff:ffff:ffff:ffff
7728fa:4c00::/2428fa:4cff:ffff:ffff:ffff:ffff:ffff:ffff
7828fa:4d00::/2428fa:4dff:ffff:ffff:ffff:ffff:ffff:ffff
7928fa:4e00::/2428fa:4eff:ffff:ffff:ffff:ffff:ffff:ffff
8028fa:4f00::/2428fa:4fff:ffff:ffff:ffff:ffff:ffff:ffff
8128fa:5000::/2428fa:50ff:ffff:ffff:ffff:ffff:ffff:ffff
8228fa:5100::/2428fa:51ff:ffff:ffff:ffff:ffff:ffff:ffff
8328fa:5200::/2428fa:52ff:ffff:ffff:ffff:ffff:ffff:ffff
8428fa:5300::/2428fa:53ff:ffff:ffff:ffff:ffff:ffff:ffff
8528fa:5400::/2428fa:54ff:ffff:ffff:ffff:ffff:ffff:ffff
8628fa:5500::/2428fa:55ff:ffff:ffff:ffff:ffff:ffff:ffff
8728fa:5600::/2428fa:56ff:ffff:ffff:ffff:ffff:ffff:ffff
8828fa:5700::/2428fa:57ff:ffff:ffff:ffff:ffff:ffff:ffff
8928fa:5800::/2428fa:58ff:ffff:ffff:ffff:ffff:ffff:ffff
9028fa:5900::/2428fa:59ff:ffff:ffff:ffff:ffff:ffff:ffff
9128fa:5a00::/2428fa:5aff:ffff:ffff:ffff:ffff:ffff:ffff
9228fa:5b00::/2428fa:5bff:ffff:ffff:ffff:ffff:ffff:ffff
9328fa:5c00::/2428fa:5cff:ffff:ffff:ffff:ffff:ffff:ffff
9428fa:5d00::/2428fa:5dff:ffff:ffff:ffff:ffff:ffff:ffff
9528fa:5e00::/2428fa:5eff:ffff:ffff:ffff:ffff:ffff:ffff
9628fa:5f00::/2428fa:5fff:ffff:ffff:ffff:ffff:ffff:ffff
9728fa:6000::/2428fa:60ff:ffff:ffff:ffff:ffff:ffff:ffff
9828fa:6100::/2428fa:61ff:ffff:ffff:ffff:ffff:ffff:ffff
9928fa:6200::/2428fa:62ff:ffff:ffff:ffff:ffff:ffff:ffff
10028fa:6300::/2428fa:63ff:ffff:ffff:ffff:ffff:ffff:ffff
10128fa:6400::/2428fa:64ff:ffff:ffff:ffff:ffff:ffff:ffff
10228fa:6500::/2428fa:65ff:ffff:ffff:ffff:ffff:ffff:ffff
10328fa:6600::/2428fa:66ff:ffff:ffff:ffff:ffff:ffff:ffff
10428fa:6700::/2428fa:67ff:ffff:ffff:ffff:ffff:ffff:ffff
10528fa:6800::/2428fa:68ff:ffff:ffff:ffff:ffff:ffff:ffff
10628fa:6900::/2428fa:69ff:ffff:ffff:ffff:ffff:ffff:ffff
10728fa:6a00::/2428fa:6aff:ffff:ffff:ffff:ffff:ffff:ffff
10828fa:6b00::/2428fa:6bff:ffff:ffff:ffff:ffff:ffff:ffff
10928fa:6c00::/2428fa:6cff:ffff:ffff:ffff:ffff:ffff:ffff
11028fa:6d00::/2428fa:6dff:ffff:ffff:ffff:ffff:ffff:ffff
11128fa:6e00::/2428fa:6eff:ffff:ffff:ffff:ffff:ffff:ffff
11228fa:6f00::/2428fa:6fff:ffff:ffff:ffff:ffff:ffff:ffff
11328fa:7000::/2428fa:70ff:ffff:ffff:ffff:ffff:ffff:ffff
11428fa:7100::/2428fa:71ff:ffff:ffff:ffff:ffff:ffff:ffff
11528fa:7200::/2428fa:72ff:ffff:ffff:ffff:ffff:ffff:ffff
11628fa:7300::/2428fa:73ff:ffff:ffff:ffff:ffff:ffff:ffff
11728fa:7400::/2428fa:74ff:ffff:ffff:ffff:ffff:ffff:ffff
11828fa:7500::/2428fa:75ff:ffff:ffff:ffff:ffff:ffff:ffff
11928fa:7600::/2428fa:76ff:ffff:ffff:ffff:ffff:ffff:ffff
12028fa:7700::/2428fa:77ff:ffff:ffff:ffff:ffff:ffff:ffff
12128fa:7800::/2428fa:78ff:ffff:ffff:ffff:ffff:ffff:ffff
12228fa:7900::/2428fa:79ff:ffff:ffff:ffff:ffff:ffff:ffff
12328fa:7a00::/2428fa:7aff:ffff:ffff:ffff:ffff:ffff:ffff
12428fa:7b00::/2428fa:7bff:ffff:ffff:ffff:ffff:ffff:ffff
12528fa:7c00::/2428fa:7cff:ffff:ffff:ffff:ffff:ffff:ffff
12628fa:7d00::/2428fa:7dff:ffff:ffff:ffff:ffff:ffff:ffff
12728fa:7e00::/2428fa:7eff:ffff:ffff:ffff:ffff:ffff:ffff
12828fa:7f00::/2428fa: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.