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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
fc58::/17
First address
fc58::
Last address
fc58:7fff: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
fc58:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zones
0.8.5.c.f.ip6.arpa
1.8.5.c.f.ip6.arpa
2.8.5.c.f.ip6.arpa
3.8.5.c.f.ip6.arpa
4.8.5.c.f.ip6.arpa
5.8.5.c.f.ip6.arpa
6.8.5.c.f.ip6.arpa
7.8.5.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)

fc58::/17 makes 128 subnets of /24.

Subnets
#SubnetLast address
1fc58::/24fc58:ff:ffff:ffff:ffff:ffff:ffff:ffff
2fc58:100::/24fc58:1ff:ffff:ffff:ffff:ffff:ffff:ffff
3fc58:200::/24fc58:2ff:ffff:ffff:ffff:ffff:ffff:ffff
4fc58:300::/24fc58:3ff:ffff:ffff:ffff:ffff:ffff:ffff
5fc58:400::/24fc58:4ff:ffff:ffff:ffff:ffff:ffff:ffff
6fc58:500::/24fc58:5ff:ffff:ffff:ffff:ffff:ffff:ffff
7fc58:600::/24fc58:6ff:ffff:ffff:ffff:ffff:ffff:ffff
8fc58:700::/24fc58:7ff:ffff:ffff:ffff:ffff:ffff:ffff
9fc58:800::/24fc58:8ff:ffff:ffff:ffff:ffff:ffff:ffff
10fc58:900::/24fc58:9ff:ffff:ffff:ffff:ffff:ffff:ffff
11fc58:a00::/24fc58:aff:ffff:ffff:ffff:ffff:ffff:ffff
12fc58:b00::/24fc58:bff:ffff:ffff:ffff:ffff:ffff:ffff
13fc58:c00::/24fc58:cff:ffff:ffff:ffff:ffff:ffff:ffff
14fc58:d00::/24fc58:dff:ffff:ffff:ffff:ffff:ffff:ffff
15fc58:e00::/24fc58:eff:ffff:ffff:ffff:ffff:ffff:ffff
16fc58:f00::/24fc58:fff:ffff:ffff:ffff:ffff:ffff:ffff
17fc58:1000::/24fc58:10ff:ffff:ffff:ffff:ffff:ffff:ffff
18fc58:1100::/24fc58:11ff:ffff:ffff:ffff:ffff:ffff:ffff
19fc58:1200::/24fc58:12ff:ffff:ffff:ffff:ffff:ffff:ffff
20fc58:1300::/24fc58:13ff:ffff:ffff:ffff:ffff:ffff:ffff
21fc58:1400::/24fc58:14ff:ffff:ffff:ffff:ffff:ffff:ffff
22fc58:1500::/24fc58:15ff:ffff:ffff:ffff:ffff:ffff:ffff
23fc58:1600::/24fc58:16ff:ffff:ffff:ffff:ffff:ffff:ffff
24fc58:1700::/24fc58:17ff:ffff:ffff:ffff:ffff:ffff:ffff
25fc58:1800::/24fc58:18ff:ffff:ffff:ffff:ffff:ffff:ffff
26fc58:1900::/24fc58:19ff:ffff:ffff:ffff:ffff:ffff:ffff
27fc58:1a00::/24fc58:1aff:ffff:ffff:ffff:ffff:ffff:ffff
28fc58:1b00::/24fc58:1bff:ffff:ffff:ffff:ffff:ffff:ffff
29fc58:1c00::/24fc58:1cff:ffff:ffff:ffff:ffff:ffff:ffff
30fc58:1d00::/24fc58:1dff:ffff:ffff:ffff:ffff:ffff:ffff
31fc58:1e00::/24fc58:1eff:ffff:ffff:ffff:ffff:ffff:ffff
32fc58:1f00::/24fc58:1fff:ffff:ffff:ffff:ffff:ffff:ffff
33fc58:2000::/24fc58:20ff:ffff:ffff:ffff:ffff:ffff:ffff
34fc58:2100::/24fc58:21ff:ffff:ffff:ffff:ffff:ffff:ffff
35fc58:2200::/24fc58:22ff:ffff:ffff:ffff:ffff:ffff:ffff
36fc58:2300::/24fc58:23ff:ffff:ffff:ffff:ffff:ffff:ffff
37fc58:2400::/24fc58:24ff:ffff:ffff:ffff:ffff:ffff:ffff
38fc58:2500::/24fc58:25ff:ffff:ffff:ffff:ffff:ffff:ffff
39fc58:2600::/24fc58:26ff:ffff:ffff:ffff:ffff:ffff:ffff
40fc58:2700::/24fc58:27ff:ffff:ffff:ffff:ffff:ffff:ffff
41fc58:2800::/24fc58:28ff:ffff:ffff:ffff:ffff:ffff:ffff
42fc58:2900::/24fc58:29ff:ffff:ffff:ffff:ffff:ffff:ffff
43fc58:2a00::/24fc58:2aff:ffff:ffff:ffff:ffff:ffff:ffff
44fc58:2b00::/24fc58:2bff:ffff:ffff:ffff:ffff:ffff:ffff
45fc58:2c00::/24fc58:2cff:ffff:ffff:ffff:ffff:ffff:ffff
46fc58:2d00::/24fc58:2dff:ffff:ffff:ffff:ffff:ffff:ffff
47fc58:2e00::/24fc58:2eff:ffff:ffff:ffff:ffff:ffff:ffff
48fc58:2f00::/24fc58:2fff:ffff:ffff:ffff:ffff:ffff:ffff
49fc58:3000::/24fc58:30ff:ffff:ffff:ffff:ffff:ffff:ffff
50fc58:3100::/24fc58:31ff:ffff:ffff:ffff:ffff:ffff:ffff
51fc58:3200::/24fc58:32ff:ffff:ffff:ffff:ffff:ffff:ffff
52fc58:3300::/24fc58:33ff:ffff:ffff:ffff:ffff:ffff:ffff
53fc58:3400::/24fc58:34ff:ffff:ffff:ffff:ffff:ffff:ffff
54fc58:3500::/24fc58:35ff:ffff:ffff:ffff:ffff:ffff:ffff
55fc58:3600::/24fc58:36ff:ffff:ffff:ffff:ffff:ffff:ffff
56fc58:3700::/24fc58:37ff:ffff:ffff:ffff:ffff:ffff:ffff
57fc58:3800::/24fc58:38ff:ffff:ffff:ffff:ffff:ffff:ffff
58fc58:3900::/24fc58:39ff:ffff:ffff:ffff:ffff:ffff:ffff
59fc58:3a00::/24fc58:3aff:ffff:ffff:ffff:ffff:ffff:ffff
60fc58:3b00::/24fc58:3bff:ffff:ffff:ffff:ffff:ffff:ffff
61fc58:3c00::/24fc58:3cff:ffff:ffff:ffff:ffff:ffff:ffff
62fc58:3d00::/24fc58:3dff:ffff:ffff:ffff:ffff:ffff:ffff
63fc58:3e00::/24fc58:3eff:ffff:ffff:ffff:ffff:ffff:ffff
64fc58:3f00::/24fc58:3fff:ffff:ffff:ffff:ffff:ffff:ffff
65fc58:4000::/24fc58:40ff:ffff:ffff:ffff:ffff:ffff:ffff
66fc58:4100::/24fc58:41ff:ffff:ffff:ffff:ffff:ffff:ffff
67fc58:4200::/24fc58:42ff:ffff:ffff:ffff:ffff:ffff:ffff
68fc58:4300::/24fc58:43ff:ffff:ffff:ffff:ffff:ffff:ffff
69fc58:4400::/24fc58:44ff:ffff:ffff:ffff:ffff:ffff:ffff
70fc58:4500::/24fc58:45ff:ffff:ffff:ffff:ffff:ffff:ffff
71fc58:4600::/24fc58:46ff:ffff:ffff:ffff:ffff:ffff:ffff
72fc58:4700::/24fc58:47ff:ffff:ffff:ffff:ffff:ffff:ffff
73fc58:4800::/24fc58:48ff:ffff:ffff:ffff:ffff:ffff:ffff
74fc58:4900::/24fc58:49ff:ffff:ffff:ffff:ffff:ffff:ffff
75fc58:4a00::/24fc58:4aff:ffff:ffff:ffff:ffff:ffff:ffff
76fc58:4b00::/24fc58:4bff:ffff:ffff:ffff:ffff:ffff:ffff
77fc58:4c00::/24fc58:4cff:ffff:ffff:ffff:ffff:ffff:ffff
78fc58:4d00::/24fc58:4dff:ffff:ffff:ffff:ffff:ffff:ffff
79fc58:4e00::/24fc58:4eff:ffff:ffff:ffff:ffff:ffff:ffff
80fc58:4f00::/24fc58:4fff:ffff:ffff:ffff:ffff:ffff:ffff
81fc58:5000::/24fc58:50ff:ffff:ffff:ffff:ffff:ffff:ffff
82fc58:5100::/24fc58:51ff:ffff:ffff:ffff:ffff:ffff:ffff
83fc58:5200::/24fc58:52ff:ffff:ffff:ffff:ffff:ffff:ffff
84fc58:5300::/24fc58:53ff:ffff:ffff:ffff:ffff:ffff:ffff
85fc58:5400::/24fc58:54ff:ffff:ffff:ffff:ffff:ffff:ffff
86fc58:5500::/24fc58:55ff:ffff:ffff:ffff:ffff:ffff:ffff
87fc58:5600::/24fc58:56ff:ffff:ffff:ffff:ffff:ffff:ffff
88fc58:5700::/24fc58:57ff:ffff:ffff:ffff:ffff:ffff:ffff
89fc58:5800::/24fc58:58ff:ffff:ffff:ffff:ffff:ffff:ffff
90fc58:5900::/24fc58:59ff:ffff:ffff:ffff:ffff:ffff:ffff
91fc58:5a00::/24fc58:5aff:ffff:ffff:ffff:ffff:ffff:ffff
92fc58:5b00::/24fc58:5bff:ffff:ffff:ffff:ffff:ffff:ffff
93fc58:5c00::/24fc58:5cff:ffff:ffff:ffff:ffff:ffff:ffff
94fc58:5d00::/24fc58:5dff:ffff:ffff:ffff:ffff:ffff:ffff
95fc58:5e00::/24fc58:5eff:ffff:ffff:ffff:ffff:ffff:ffff
96fc58:5f00::/24fc58:5fff:ffff:ffff:ffff:ffff:ffff:ffff
97fc58:6000::/24fc58:60ff:ffff:ffff:ffff:ffff:ffff:ffff
98fc58:6100::/24fc58:61ff:ffff:ffff:ffff:ffff:ffff:ffff
99fc58:6200::/24fc58:62ff:ffff:ffff:ffff:ffff:ffff:ffff
100fc58:6300::/24fc58:63ff:ffff:ffff:ffff:ffff:ffff:ffff
101fc58:6400::/24fc58:64ff:ffff:ffff:ffff:ffff:ffff:ffff
102fc58:6500::/24fc58:65ff:ffff:ffff:ffff:ffff:ffff:ffff
103fc58:6600::/24fc58:66ff:ffff:ffff:ffff:ffff:ffff:ffff
104fc58:6700::/24fc58:67ff:ffff:ffff:ffff:ffff:ffff:ffff
105fc58:6800::/24fc58:68ff:ffff:ffff:ffff:ffff:ffff:ffff
106fc58:6900::/24fc58:69ff:ffff:ffff:ffff:ffff:ffff:ffff
107fc58:6a00::/24fc58:6aff:ffff:ffff:ffff:ffff:ffff:ffff
108fc58:6b00::/24fc58:6bff:ffff:ffff:ffff:ffff:ffff:ffff
109fc58:6c00::/24fc58:6cff:ffff:ffff:ffff:ffff:ffff:ffff
110fc58:6d00::/24fc58:6dff:ffff:ffff:ffff:ffff:ffff:ffff
111fc58:6e00::/24fc58:6eff:ffff:ffff:ffff:ffff:ffff:ffff
112fc58:6f00::/24fc58:6fff:ffff:ffff:ffff:ffff:ffff:ffff
113fc58:7000::/24fc58:70ff:ffff:ffff:ffff:ffff:ffff:ffff
114fc58:7100::/24fc58:71ff:ffff:ffff:ffff:ffff:ffff:ffff
115fc58:7200::/24fc58:72ff:ffff:ffff:ffff:ffff:ffff:ffff
116fc58:7300::/24fc58:73ff:ffff:ffff:ffff:ffff:ffff:ffff
117fc58:7400::/24fc58:74ff:ffff:ffff:ffff:ffff:ffff:ffff
118fc58:7500::/24fc58:75ff:ffff:ffff:ffff:ffff:ffff:ffff
119fc58:7600::/24fc58:76ff:ffff:ffff:ffff:ffff:ffff:ffff
120fc58:7700::/24fc58:77ff:ffff:ffff:ffff:ffff:ffff:ffff
121fc58:7800::/24fc58:78ff:ffff:ffff:ffff:ffff:ffff:ffff
122fc58:7900::/24fc58:79ff:ffff:ffff:ffff:ffff:ffff:ffff
123fc58:7a00::/24fc58:7aff:ffff:ffff:ffff:ffff:ffff:ffff
124fc58:7b00::/24fc58:7bff:ffff:ffff:ffff:ffff:ffff:ffff
125fc58:7c00::/24fc58:7cff:ffff:ffff:ffff:ffff:ffff:ffff
126fc58:7d00::/24fc58:7dff:ffff:ffff:ffff:ffff:ffff:ffff
127fc58:7e00::/24fc58:7eff:ffff:ffff:ffff:ffff:ffff:ffff
128fc58:7f00::/24fc58:7fff: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.