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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
fc70::/17
First address
fc70::
Last address
fc70:7fff: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
fc70:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zones
0.0.7.c.f.ip6.arpa
1.0.7.c.f.ip6.arpa
2.0.7.c.f.ip6.arpa
3.0.7.c.f.ip6.arpa
4.0.7.c.f.ip6.arpa
5.0.7.c.f.ip6.arpa
6.0.7.c.f.ip6.arpa
7.0.7.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)

fc70::/17 makes 128 subnets of /24.

Subnets
#SubnetLast address
1fc70::/24fc70:ff:ffff:ffff:ffff:ffff:ffff:ffff
2fc70:100::/24fc70:1ff:ffff:ffff:ffff:ffff:ffff:ffff
3fc70:200::/24fc70:2ff:ffff:ffff:ffff:ffff:ffff:ffff
4fc70:300::/24fc70:3ff:ffff:ffff:ffff:ffff:ffff:ffff
5fc70:400::/24fc70:4ff:ffff:ffff:ffff:ffff:ffff:ffff
6fc70:500::/24fc70:5ff:ffff:ffff:ffff:ffff:ffff:ffff
7fc70:600::/24fc70:6ff:ffff:ffff:ffff:ffff:ffff:ffff
8fc70:700::/24fc70:7ff:ffff:ffff:ffff:ffff:ffff:ffff
9fc70:800::/24fc70:8ff:ffff:ffff:ffff:ffff:ffff:ffff
10fc70:900::/24fc70:9ff:ffff:ffff:ffff:ffff:ffff:ffff
11fc70:a00::/24fc70:aff:ffff:ffff:ffff:ffff:ffff:ffff
12fc70:b00::/24fc70:bff:ffff:ffff:ffff:ffff:ffff:ffff
13fc70:c00::/24fc70:cff:ffff:ffff:ffff:ffff:ffff:ffff
14fc70:d00::/24fc70:dff:ffff:ffff:ffff:ffff:ffff:ffff
15fc70:e00::/24fc70:eff:ffff:ffff:ffff:ffff:ffff:ffff
16fc70:f00::/24fc70:fff:ffff:ffff:ffff:ffff:ffff:ffff
17fc70:1000::/24fc70:10ff:ffff:ffff:ffff:ffff:ffff:ffff
18fc70:1100::/24fc70:11ff:ffff:ffff:ffff:ffff:ffff:ffff
19fc70:1200::/24fc70:12ff:ffff:ffff:ffff:ffff:ffff:ffff
20fc70:1300::/24fc70:13ff:ffff:ffff:ffff:ffff:ffff:ffff
21fc70:1400::/24fc70:14ff:ffff:ffff:ffff:ffff:ffff:ffff
22fc70:1500::/24fc70:15ff:ffff:ffff:ffff:ffff:ffff:ffff
23fc70:1600::/24fc70:16ff:ffff:ffff:ffff:ffff:ffff:ffff
24fc70:1700::/24fc70:17ff:ffff:ffff:ffff:ffff:ffff:ffff
25fc70:1800::/24fc70:18ff:ffff:ffff:ffff:ffff:ffff:ffff
26fc70:1900::/24fc70:19ff:ffff:ffff:ffff:ffff:ffff:ffff
27fc70:1a00::/24fc70:1aff:ffff:ffff:ffff:ffff:ffff:ffff
28fc70:1b00::/24fc70:1bff:ffff:ffff:ffff:ffff:ffff:ffff
29fc70:1c00::/24fc70:1cff:ffff:ffff:ffff:ffff:ffff:ffff
30fc70:1d00::/24fc70:1dff:ffff:ffff:ffff:ffff:ffff:ffff
31fc70:1e00::/24fc70:1eff:ffff:ffff:ffff:ffff:ffff:ffff
32fc70:1f00::/24fc70:1fff:ffff:ffff:ffff:ffff:ffff:ffff
33fc70:2000::/24fc70:20ff:ffff:ffff:ffff:ffff:ffff:ffff
34fc70:2100::/24fc70:21ff:ffff:ffff:ffff:ffff:ffff:ffff
35fc70:2200::/24fc70:22ff:ffff:ffff:ffff:ffff:ffff:ffff
36fc70:2300::/24fc70:23ff:ffff:ffff:ffff:ffff:ffff:ffff
37fc70:2400::/24fc70:24ff:ffff:ffff:ffff:ffff:ffff:ffff
38fc70:2500::/24fc70:25ff:ffff:ffff:ffff:ffff:ffff:ffff
39fc70:2600::/24fc70:26ff:ffff:ffff:ffff:ffff:ffff:ffff
40fc70:2700::/24fc70:27ff:ffff:ffff:ffff:ffff:ffff:ffff
41fc70:2800::/24fc70:28ff:ffff:ffff:ffff:ffff:ffff:ffff
42fc70:2900::/24fc70:29ff:ffff:ffff:ffff:ffff:ffff:ffff
43fc70:2a00::/24fc70:2aff:ffff:ffff:ffff:ffff:ffff:ffff
44fc70:2b00::/24fc70:2bff:ffff:ffff:ffff:ffff:ffff:ffff
45fc70:2c00::/24fc70:2cff:ffff:ffff:ffff:ffff:ffff:ffff
46fc70:2d00::/24fc70:2dff:ffff:ffff:ffff:ffff:ffff:ffff
47fc70:2e00::/24fc70:2eff:ffff:ffff:ffff:ffff:ffff:ffff
48fc70:2f00::/24fc70:2fff:ffff:ffff:ffff:ffff:ffff:ffff
49fc70:3000::/24fc70:30ff:ffff:ffff:ffff:ffff:ffff:ffff
50fc70:3100::/24fc70:31ff:ffff:ffff:ffff:ffff:ffff:ffff
51fc70:3200::/24fc70:32ff:ffff:ffff:ffff:ffff:ffff:ffff
52fc70:3300::/24fc70:33ff:ffff:ffff:ffff:ffff:ffff:ffff
53fc70:3400::/24fc70:34ff:ffff:ffff:ffff:ffff:ffff:ffff
54fc70:3500::/24fc70:35ff:ffff:ffff:ffff:ffff:ffff:ffff
55fc70:3600::/24fc70:36ff:ffff:ffff:ffff:ffff:ffff:ffff
56fc70:3700::/24fc70:37ff:ffff:ffff:ffff:ffff:ffff:ffff
57fc70:3800::/24fc70:38ff:ffff:ffff:ffff:ffff:ffff:ffff
58fc70:3900::/24fc70:39ff:ffff:ffff:ffff:ffff:ffff:ffff
59fc70:3a00::/24fc70:3aff:ffff:ffff:ffff:ffff:ffff:ffff
60fc70:3b00::/24fc70:3bff:ffff:ffff:ffff:ffff:ffff:ffff
61fc70:3c00::/24fc70:3cff:ffff:ffff:ffff:ffff:ffff:ffff
62fc70:3d00::/24fc70:3dff:ffff:ffff:ffff:ffff:ffff:ffff
63fc70:3e00::/24fc70:3eff:ffff:ffff:ffff:ffff:ffff:ffff
64fc70:3f00::/24fc70:3fff:ffff:ffff:ffff:ffff:ffff:ffff
65fc70:4000::/24fc70:40ff:ffff:ffff:ffff:ffff:ffff:ffff
66fc70:4100::/24fc70:41ff:ffff:ffff:ffff:ffff:ffff:ffff
67fc70:4200::/24fc70:42ff:ffff:ffff:ffff:ffff:ffff:ffff
68fc70:4300::/24fc70:43ff:ffff:ffff:ffff:ffff:ffff:ffff
69fc70:4400::/24fc70:44ff:ffff:ffff:ffff:ffff:ffff:ffff
70fc70:4500::/24fc70:45ff:ffff:ffff:ffff:ffff:ffff:ffff
71fc70:4600::/24fc70:46ff:ffff:ffff:ffff:ffff:ffff:ffff
72fc70:4700::/24fc70:47ff:ffff:ffff:ffff:ffff:ffff:ffff
73fc70:4800::/24fc70:48ff:ffff:ffff:ffff:ffff:ffff:ffff
74fc70:4900::/24fc70:49ff:ffff:ffff:ffff:ffff:ffff:ffff
75fc70:4a00::/24fc70:4aff:ffff:ffff:ffff:ffff:ffff:ffff
76fc70:4b00::/24fc70:4bff:ffff:ffff:ffff:ffff:ffff:ffff
77fc70:4c00::/24fc70:4cff:ffff:ffff:ffff:ffff:ffff:ffff
78fc70:4d00::/24fc70:4dff:ffff:ffff:ffff:ffff:ffff:ffff
79fc70:4e00::/24fc70:4eff:ffff:ffff:ffff:ffff:ffff:ffff
80fc70:4f00::/24fc70:4fff:ffff:ffff:ffff:ffff:ffff:ffff
81fc70:5000::/24fc70:50ff:ffff:ffff:ffff:ffff:ffff:ffff
82fc70:5100::/24fc70:51ff:ffff:ffff:ffff:ffff:ffff:ffff
83fc70:5200::/24fc70:52ff:ffff:ffff:ffff:ffff:ffff:ffff
84fc70:5300::/24fc70:53ff:ffff:ffff:ffff:ffff:ffff:ffff
85fc70:5400::/24fc70:54ff:ffff:ffff:ffff:ffff:ffff:ffff
86fc70:5500::/24fc70:55ff:ffff:ffff:ffff:ffff:ffff:ffff
87fc70:5600::/24fc70:56ff:ffff:ffff:ffff:ffff:ffff:ffff
88fc70:5700::/24fc70:57ff:ffff:ffff:ffff:ffff:ffff:ffff
89fc70:5800::/24fc70:58ff:ffff:ffff:ffff:ffff:ffff:ffff
90fc70:5900::/24fc70:59ff:ffff:ffff:ffff:ffff:ffff:ffff
91fc70:5a00::/24fc70:5aff:ffff:ffff:ffff:ffff:ffff:ffff
92fc70:5b00::/24fc70:5bff:ffff:ffff:ffff:ffff:ffff:ffff
93fc70:5c00::/24fc70:5cff:ffff:ffff:ffff:ffff:ffff:ffff
94fc70:5d00::/24fc70:5dff:ffff:ffff:ffff:ffff:ffff:ffff
95fc70:5e00::/24fc70:5eff:ffff:ffff:ffff:ffff:ffff:ffff
96fc70:5f00::/24fc70:5fff:ffff:ffff:ffff:ffff:ffff:ffff
97fc70:6000::/24fc70:60ff:ffff:ffff:ffff:ffff:ffff:ffff
98fc70:6100::/24fc70:61ff:ffff:ffff:ffff:ffff:ffff:ffff
99fc70:6200::/24fc70:62ff:ffff:ffff:ffff:ffff:ffff:ffff
100fc70:6300::/24fc70:63ff:ffff:ffff:ffff:ffff:ffff:ffff
101fc70:6400::/24fc70:64ff:ffff:ffff:ffff:ffff:ffff:ffff
102fc70:6500::/24fc70:65ff:ffff:ffff:ffff:ffff:ffff:ffff
103fc70:6600::/24fc70:66ff:ffff:ffff:ffff:ffff:ffff:ffff
104fc70:6700::/24fc70:67ff:ffff:ffff:ffff:ffff:ffff:ffff
105fc70:6800::/24fc70:68ff:ffff:ffff:ffff:ffff:ffff:ffff
106fc70:6900::/24fc70:69ff:ffff:ffff:ffff:ffff:ffff:ffff
107fc70:6a00::/24fc70:6aff:ffff:ffff:ffff:ffff:ffff:ffff
108fc70:6b00::/24fc70:6bff:ffff:ffff:ffff:ffff:ffff:ffff
109fc70:6c00::/24fc70:6cff:ffff:ffff:ffff:ffff:ffff:ffff
110fc70:6d00::/24fc70:6dff:ffff:ffff:ffff:ffff:ffff:ffff
111fc70:6e00::/24fc70:6eff:ffff:ffff:ffff:ffff:ffff:ffff
112fc70:6f00::/24fc70:6fff:ffff:ffff:ffff:ffff:ffff:ffff
113fc70:7000::/24fc70:70ff:ffff:ffff:ffff:ffff:ffff:ffff
114fc70:7100::/24fc70:71ff:ffff:ffff:ffff:ffff:ffff:ffff
115fc70:7200::/24fc70:72ff:ffff:ffff:ffff:ffff:ffff:ffff
116fc70:7300::/24fc70:73ff:ffff:ffff:ffff:ffff:ffff:ffff
117fc70:7400::/24fc70:74ff:ffff:ffff:ffff:ffff:ffff:ffff
118fc70:7500::/24fc70:75ff:ffff:ffff:ffff:ffff:ffff:ffff
119fc70:7600::/24fc70:76ff:ffff:ffff:ffff:ffff:ffff:ffff
120fc70:7700::/24fc70:77ff:ffff:ffff:ffff:ffff:ffff:ffff
121fc70:7800::/24fc70:78ff:ffff:ffff:ffff:ffff:ffff:ffff
122fc70:7900::/24fc70:79ff:ffff:ffff:ffff:ffff:ffff:ffff
123fc70:7a00::/24fc70:7aff:ffff:ffff:ffff:ffff:ffff:ffff
124fc70:7b00::/24fc70:7bff:ffff:ffff:ffff:ffff:ffff:ffff
125fc70:7c00::/24fc70:7cff:ffff:ffff:ffff:ffff:ffff:ffff
126fc70:7d00::/24fc70:7dff:ffff:ffff:ffff:ffff:ffff:ffff
127fc70:7e00::/24fc70:7eff:ffff:ffff:ffff:ffff:ffff:ffff
128fc70:7f00::/24fc70:7fff: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.