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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
fcba::/17
First address
fcba::
Last address
fcba: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
fcba: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.a.b.c.f.ip6.arpa
1.a.b.c.f.ip6.arpa
2.a.b.c.f.ip6.arpa
3.a.b.c.f.ip6.arpa
4.a.b.c.f.ip6.arpa
5.a.b.c.f.ip6.arpa
6.a.b.c.f.ip6.arpa
7.a.b.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)

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

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