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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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Update checkIs this computer, phone and browser up to date? With links to update.Camera and mic testCheck your webcam and microphone before a call.Test print pagePrint an A4 page to check a printer: edges, text, line art and colours.

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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/16
Addresses2^112
/64 networks2^48
Network
20f1::/16
First address
20f1::
Last address
20f1:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
5,192,296,858,534,827,628,530,496,329,220,096 (2^112)
/64 networks (LANs)
281,474,976,710,656 (2^48)
Full form
20f1:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
1.f.0.2.ip6.arpa
Split into smaller subnets/24
/17 (2)/18 (4)/19 (8)/20 (16)/24 (256)/28 (4,096)/32 (65,536)

20f1::/16 makes 256 subnets of /24.

Subnets
#SubnetLast address
120f1::/2420f1:ff:ffff:ffff:ffff:ffff:ffff:ffff
220f1:100::/2420f1:1ff:ffff:ffff:ffff:ffff:ffff:ffff
320f1:200::/2420f1:2ff:ffff:ffff:ffff:ffff:ffff:ffff
420f1:300::/2420f1:3ff:ffff:ffff:ffff:ffff:ffff:ffff
520f1:400::/2420f1:4ff:ffff:ffff:ffff:ffff:ffff:ffff
620f1:500::/2420f1:5ff:ffff:ffff:ffff:ffff:ffff:ffff
720f1:600::/2420f1:6ff:ffff:ffff:ffff:ffff:ffff:ffff
820f1:700::/2420f1:7ff:ffff:ffff:ffff:ffff:ffff:ffff
920f1:800::/2420f1:8ff:ffff:ffff:ffff:ffff:ffff:ffff
1020f1:900::/2420f1:9ff:ffff:ffff:ffff:ffff:ffff:ffff
1120f1:a00::/2420f1:aff:ffff:ffff:ffff:ffff:ffff:ffff
1220f1:b00::/2420f1:bff:ffff:ffff:ffff:ffff:ffff:ffff
1320f1:c00::/2420f1:cff:ffff:ffff:ffff:ffff:ffff:ffff
1420f1:d00::/2420f1:dff:ffff:ffff:ffff:ffff:ffff:ffff
1520f1:e00::/2420f1:eff:ffff:ffff:ffff:ffff:ffff:ffff
1620f1:f00::/2420f1:fff:ffff:ffff:ffff:ffff:ffff:ffff
1720f1:1000::/2420f1:10ff:ffff:ffff:ffff:ffff:ffff:ffff
1820f1:1100::/2420f1:11ff:ffff:ffff:ffff:ffff:ffff:ffff
1920f1:1200::/2420f1:12ff:ffff:ffff:ffff:ffff:ffff:ffff
2020f1:1300::/2420f1:13ff:ffff:ffff:ffff:ffff:ffff:ffff
2120f1:1400::/2420f1:14ff:ffff:ffff:ffff:ffff:ffff:ffff
2220f1:1500::/2420f1:15ff:ffff:ffff:ffff:ffff:ffff:ffff
2320f1:1600::/2420f1:16ff:ffff:ffff:ffff:ffff:ffff:ffff
2420f1:1700::/2420f1:17ff:ffff:ffff:ffff:ffff:ffff:ffff
2520f1:1800::/2420f1:18ff:ffff:ffff:ffff:ffff:ffff:ffff
2620f1:1900::/2420f1:19ff:ffff:ffff:ffff:ffff:ffff:ffff
2720f1:1a00::/2420f1:1aff:ffff:ffff:ffff:ffff:ffff:ffff
2820f1:1b00::/2420f1:1bff:ffff:ffff:ffff:ffff:ffff:ffff
2920f1:1c00::/2420f1:1cff:ffff:ffff:ffff:ffff:ffff:ffff
3020f1:1d00::/2420f1:1dff:ffff:ffff:ffff:ffff:ffff:ffff
3120f1:1e00::/2420f1:1eff:ffff:ffff:ffff:ffff:ffff:ffff
3220f1:1f00::/2420f1:1fff:ffff:ffff:ffff:ffff:ffff:ffff
3320f1:2000::/2420f1:20ff:ffff:ffff:ffff:ffff:ffff:ffff
3420f1:2100::/2420f1:21ff:ffff:ffff:ffff:ffff:ffff:ffff
3520f1:2200::/2420f1:22ff:ffff:ffff:ffff:ffff:ffff:ffff
3620f1:2300::/2420f1:23ff:ffff:ffff:ffff:ffff:ffff:ffff
3720f1:2400::/2420f1:24ff:ffff:ffff:ffff:ffff:ffff:ffff
3820f1:2500::/2420f1:25ff:ffff:ffff:ffff:ffff:ffff:ffff
3920f1:2600::/2420f1:26ff:ffff:ffff:ffff:ffff:ffff:ffff
4020f1:2700::/2420f1:27ff:ffff:ffff:ffff:ffff:ffff:ffff
4120f1:2800::/2420f1:28ff:ffff:ffff:ffff:ffff:ffff:ffff
4220f1:2900::/2420f1:29ff:ffff:ffff:ffff:ffff:ffff:ffff
4320f1:2a00::/2420f1:2aff:ffff:ffff:ffff:ffff:ffff:ffff
4420f1:2b00::/2420f1:2bff:ffff:ffff:ffff:ffff:ffff:ffff
4520f1:2c00::/2420f1:2cff:ffff:ffff:ffff:ffff:ffff:ffff
4620f1:2d00::/2420f1:2dff:ffff:ffff:ffff:ffff:ffff:ffff
4720f1:2e00::/2420f1:2eff:ffff:ffff:ffff:ffff:ffff:ffff
4820f1:2f00::/2420f1:2fff:ffff:ffff:ffff:ffff:ffff:ffff
4920f1:3000::/2420f1:30ff:ffff:ffff:ffff:ffff:ffff:ffff
5020f1:3100::/2420f1:31ff:ffff:ffff:ffff:ffff:ffff:ffff
5120f1:3200::/2420f1:32ff:ffff:ffff:ffff:ffff:ffff:ffff
5220f1:3300::/2420f1:33ff:ffff:ffff:ffff:ffff:ffff:ffff
5320f1:3400::/2420f1:34ff:ffff:ffff:ffff:ffff:ffff:ffff
5420f1:3500::/2420f1:35ff:ffff:ffff:ffff:ffff:ffff:ffff
5520f1:3600::/2420f1:36ff:ffff:ffff:ffff:ffff:ffff:ffff
5620f1:3700::/2420f1:37ff:ffff:ffff:ffff:ffff:ffff:ffff
5720f1:3800::/2420f1:38ff:ffff:ffff:ffff:ffff:ffff:ffff
5820f1:3900::/2420f1:39ff:ffff:ffff:ffff:ffff:ffff:ffff
5920f1:3a00::/2420f1:3aff:ffff:ffff:ffff:ffff:ffff:ffff
6020f1:3b00::/2420f1:3bff:ffff:ffff:ffff:ffff:ffff:ffff
6120f1:3c00::/2420f1:3cff:ffff:ffff:ffff:ffff:ffff:ffff
6220f1:3d00::/2420f1:3dff:ffff:ffff:ffff:ffff:ffff:ffff
6320f1:3e00::/2420f1:3eff:ffff:ffff:ffff:ffff:ffff:ffff
6420f1:3f00::/2420f1:3fff:ffff:ffff:ffff:ffff:ffff:ffff
6520f1:4000::/2420f1:40ff:ffff:ffff:ffff:ffff:ffff:ffff
6620f1:4100::/2420f1:41ff:ffff:ffff:ffff:ffff:ffff:ffff
6720f1:4200::/2420f1:42ff:ffff:ffff:ffff:ffff:ffff:ffff
6820f1:4300::/2420f1:43ff:ffff:ffff:ffff:ffff:ffff:ffff
6920f1:4400::/2420f1:44ff:ffff:ffff:ffff:ffff:ffff:ffff
7020f1:4500::/2420f1:45ff:ffff:ffff:ffff:ffff:ffff:ffff
7120f1:4600::/2420f1:46ff:ffff:ffff:ffff:ffff:ffff:ffff
7220f1:4700::/2420f1:47ff:ffff:ffff:ffff:ffff:ffff:ffff
7320f1:4800::/2420f1:48ff:ffff:ffff:ffff:ffff:ffff:ffff
7420f1:4900::/2420f1:49ff:ffff:ffff:ffff:ffff:ffff:ffff
7520f1:4a00::/2420f1:4aff:ffff:ffff:ffff:ffff:ffff:ffff
7620f1:4b00::/2420f1:4bff:ffff:ffff:ffff:ffff:ffff:ffff
7720f1:4c00::/2420f1:4cff:ffff:ffff:ffff:ffff:ffff:ffff
7820f1:4d00::/2420f1:4dff:ffff:ffff:ffff:ffff:ffff:ffff
7920f1:4e00::/2420f1:4eff:ffff:ffff:ffff:ffff:ffff:ffff
8020f1:4f00::/2420f1:4fff:ffff:ffff:ffff:ffff:ffff:ffff
8120f1:5000::/2420f1:50ff:ffff:ffff:ffff:ffff:ffff:ffff
8220f1:5100::/2420f1:51ff:ffff:ffff:ffff:ffff:ffff:ffff
8320f1:5200::/2420f1:52ff:ffff:ffff:ffff:ffff:ffff:ffff
8420f1:5300::/2420f1:53ff:ffff:ffff:ffff:ffff:ffff:ffff
8520f1:5400::/2420f1:54ff:ffff:ffff:ffff:ffff:ffff:ffff
8620f1:5500::/2420f1:55ff:ffff:ffff:ffff:ffff:ffff:ffff
8720f1:5600::/2420f1:56ff:ffff:ffff:ffff:ffff:ffff:ffff
8820f1:5700::/2420f1:57ff:ffff:ffff:ffff:ffff:ffff:ffff
8920f1:5800::/2420f1:58ff:ffff:ffff:ffff:ffff:ffff:ffff
9020f1:5900::/2420f1:59ff:ffff:ffff:ffff:ffff:ffff:ffff
9120f1:5a00::/2420f1:5aff:ffff:ffff:ffff:ffff:ffff:ffff
9220f1:5b00::/2420f1:5bff:ffff:ffff:ffff:ffff:ffff:ffff
9320f1:5c00::/2420f1:5cff:ffff:ffff:ffff:ffff:ffff:ffff
9420f1:5d00::/2420f1:5dff:ffff:ffff:ffff:ffff:ffff:ffff
9520f1:5e00::/2420f1:5eff:ffff:ffff:ffff:ffff:ffff:ffff
9620f1:5f00::/2420f1:5fff:ffff:ffff:ffff:ffff:ffff:ffff
9720f1:6000::/2420f1:60ff:ffff:ffff:ffff:ffff:ffff:ffff
9820f1:6100::/2420f1:61ff:ffff:ffff:ffff:ffff:ffff:ffff
9920f1:6200::/2420f1:62ff:ffff:ffff:ffff:ffff:ffff:ffff
10020f1:6300::/2420f1:63ff:ffff:ffff:ffff:ffff:ffff:ffff
10120f1:6400::/2420f1:64ff:ffff:ffff:ffff:ffff:ffff:ffff
10220f1:6500::/2420f1:65ff:ffff:ffff:ffff:ffff:ffff:ffff
10320f1:6600::/2420f1:66ff:ffff:ffff:ffff:ffff:ffff:ffff
10420f1:6700::/2420f1:67ff:ffff:ffff:ffff:ffff:ffff:ffff
10520f1:6800::/2420f1:68ff:ffff:ffff:ffff:ffff:ffff:ffff
10620f1:6900::/2420f1:69ff:ffff:ffff:ffff:ffff:ffff:ffff
10720f1:6a00::/2420f1:6aff:ffff:ffff:ffff:ffff:ffff:ffff
10820f1:6b00::/2420f1:6bff:ffff:ffff:ffff:ffff:ffff:ffff
10920f1:6c00::/2420f1:6cff:ffff:ffff:ffff:ffff:ffff:ffff
11020f1:6d00::/2420f1:6dff:ffff:ffff:ffff:ffff:ffff:ffff
11120f1:6e00::/2420f1:6eff:ffff:ffff:ffff:ffff:ffff:ffff
11220f1:6f00::/2420f1:6fff:ffff:ffff:ffff:ffff:ffff:ffff
11320f1:7000::/2420f1:70ff:ffff:ffff:ffff:ffff:ffff:ffff
11420f1:7100::/2420f1:71ff:ffff:ffff:ffff:ffff:ffff:ffff
11520f1:7200::/2420f1:72ff:ffff:ffff:ffff:ffff:ffff:ffff
11620f1:7300::/2420f1:73ff:ffff:ffff:ffff:ffff:ffff:ffff
11720f1:7400::/2420f1:74ff:ffff:ffff:ffff:ffff:ffff:ffff
11820f1:7500::/2420f1:75ff:ffff:ffff:ffff:ffff:ffff:ffff
11920f1:7600::/2420f1:76ff:ffff:ffff:ffff:ffff:ffff:ffff
12020f1:7700::/2420f1:77ff:ffff:ffff:ffff:ffff:ffff:ffff
12120f1:7800::/2420f1:78ff:ffff:ffff:ffff:ffff:ffff:ffff
12220f1:7900::/2420f1:79ff:ffff:ffff:ffff:ffff:ffff:ffff
12320f1:7a00::/2420f1:7aff:ffff:ffff:ffff:ffff:ffff:ffff
12420f1:7b00::/2420f1:7bff:ffff:ffff:ffff:ffff:ffff:ffff
12520f1:7c00::/2420f1:7cff:ffff:ffff:ffff:ffff:ffff:ffff
12620f1:7d00::/2420f1:7dff:ffff:ffff:ffff:ffff:ffff:ffff
12720f1:7e00::/2420f1:7eff:ffff:ffff:ffff:ffff:ffff:ffff
12820f1:7f00::/2420f1:7fff:ffff:ffff:ffff:ffff:ffff:ffff
12920f1:8000::/2420f1:80ff:ffff:ffff:ffff:ffff:ffff:ffff
13020f1:8100::/2420f1:81ff:ffff:ffff:ffff:ffff:ffff:ffff
13120f1:8200::/2420f1:82ff:ffff:ffff:ffff:ffff:ffff:ffff
13220f1:8300::/2420f1:83ff:ffff:ffff:ffff:ffff:ffff:ffff
13320f1:8400::/2420f1:84ff:ffff:ffff:ffff:ffff:ffff:ffff
13420f1:8500::/2420f1:85ff:ffff:ffff:ffff:ffff:ffff:ffff
13520f1:8600::/2420f1:86ff:ffff:ffff:ffff:ffff:ffff:ffff
13620f1:8700::/2420f1:87ff:ffff:ffff:ffff:ffff:ffff:ffff
13720f1:8800::/2420f1:88ff:ffff:ffff:ffff:ffff:ffff:ffff
13820f1:8900::/2420f1:89ff:ffff:ffff:ffff:ffff:ffff:ffff
13920f1:8a00::/2420f1:8aff:ffff:ffff:ffff:ffff:ffff:ffff
14020f1:8b00::/2420f1:8bff:ffff:ffff:ffff:ffff:ffff:ffff
14120f1:8c00::/2420f1:8cff:ffff:ffff:ffff:ffff:ffff:ffff
14220f1:8d00::/2420f1:8dff:ffff:ffff:ffff:ffff:ffff:ffff
14320f1:8e00::/2420f1:8eff:ffff:ffff:ffff:ffff:ffff:ffff
14420f1:8f00::/2420f1:8fff:ffff:ffff:ffff:ffff:ffff:ffff
14520f1:9000::/2420f1:90ff:ffff:ffff:ffff:ffff:ffff:ffff
14620f1:9100::/2420f1:91ff:ffff:ffff:ffff:ffff:ffff:ffff
14720f1:9200::/2420f1:92ff:ffff:ffff:ffff:ffff:ffff:ffff
14820f1:9300::/2420f1:93ff:ffff:ffff:ffff:ffff:ffff:ffff
14920f1:9400::/2420f1:94ff:ffff:ffff:ffff:ffff:ffff:ffff
15020f1:9500::/2420f1:95ff:ffff:ffff:ffff:ffff:ffff:ffff
15120f1:9600::/2420f1:96ff:ffff:ffff:ffff:ffff:ffff:ffff
15220f1:9700::/2420f1:97ff:ffff:ffff:ffff:ffff:ffff:ffff
15320f1:9800::/2420f1:98ff:ffff:ffff:ffff:ffff:ffff:ffff
15420f1:9900::/2420f1:99ff:ffff:ffff:ffff:ffff:ffff:ffff
15520f1:9a00::/2420f1:9aff:ffff:ffff:ffff:ffff:ffff:ffff
15620f1:9b00::/2420f1:9bff:ffff:ffff:ffff:ffff:ffff:ffff
15720f1:9c00::/2420f1:9cff:ffff:ffff:ffff:ffff:ffff:ffff
15820f1:9d00::/2420f1:9dff:ffff:ffff:ffff:ffff:ffff:ffff
15920f1:9e00::/2420f1:9eff:ffff:ffff:ffff:ffff:ffff:ffff
16020f1:9f00::/2420f1:9fff:ffff:ffff:ffff:ffff:ffff:ffff
16120f1:a000::/2420f1:a0ff:ffff:ffff:ffff:ffff:ffff:ffff
16220f1:a100::/2420f1:a1ff:ffff:ffff:ffff:ffff:ffff:ffff
16320f1:a200::/2420f1:a2ff:ffff:ffff:ffff:ffff:ffff:ffff
16420f1:a300::/2420f1:a3ff:ffff:ffff:ffff:ffff:ffff:ffff
16520f1:a400::/2420f1:a4ff:ffff:ffff:ffff:ffff:ffff:ffff
16620f1:a500::/2420f1:a5ff:ffff:ffff:ffff:ffff:ffff:ffff
16720f1:a600::/2420f1:a6ff:ffff:ffff:ffff:ffff:ffff:ffff
16820f1:a700::/2420f1:a7ff:ffff:ffff:ffff:ffff:ffff:ffff
16920f1:a800::/2420f1:a8ff:ffff:ffff:ffff:ffff:ffff:ffff
17020f1:a900::/2420f1:a9ff:ffff:ffff:ffff:ffff:ffff:ffff
17120f1:aa00::/2420f1:aaff:ffff:ffff:ffff:ffff:ffff:ffff
17220f1:ab00::/2420f1:abff:ffff:ffff:ffff:ffff:ffff:ffff
17320f1:ac00::/2420f1:acff:ffff:ffff:ffff:ffff:ffff:ffff
17420f1:ad00::/2420f1:adff:ffff:ffff:ffff:ffff:ffff:ffff
17520f1:ae00::/2420f1:aeff:ffff:ffff:ffff:ffff:ffff:ffff
17620f1:af00::/2420f1:afff:ffff:ffff:ffff:ffff:ffff:ffff
17720f1:b000::/2420f1:b0ff:ffff:ffff:ffff:ffff:ffff:ffff
17820f1:b100::/2420f1:b1ff:ffff:ffff:ffff:ffff:ffff:ffff
17920f1:b200::/2420f1:b2ff:ffff:ffff:ffff:ffff:ffff:ffff
18020f1:b300::/2420f1:b3ff:ffff:ffff:ffff:ffff:ffff:ffff
18120f1:b400::/2420f1:b4ff:ffff:ffff:ffff:ffff:ffff:ffff
18220f1:b500::/2420f1:b5ff:ffff:ffff:ffff:ffff:ffff:ffff
18320f1:b600::/2420f1:b6ff:ffff:ffff:ffff:ffff:ffff:ffff
18420f1:b700::/2420f1:b7ff:ffff:ffff:ffff:ffff:ffff:ffff
18520f1:b800::/2420f1:b8ff:ffff:ffff:ffff:ffff:ffff:ffff
18620f1:b900::/2420f1:b9ff:ffff:ffff:ffff:ffff:ffff:ffff
18720f1:ba00::/2420f1:baff:ffff:ffff:ffff:ffff:ffff:ffff
18820f1:bb00::/2420f1:bbff:ffff:ffff:ffff:ffff:ffff:ffff
18920f1:bc00::/2420f1:bcff:ffff:ffff:ffff:ffff:ffff:ffff
19020f1:bd00::/2420f1:bdff:ffff:ffff:ffff:ffff:ffff:ffff
19120f1:be00::/2420f1:beff:ffff:ffff:ffff:ffff:ffff:ffff
19220f1:bf00::/2420f1:bfff:ffff:ffff:ffff:ffff:ffff:ffff
19320f1:c000::/2420f1:c0ff:ffff:ffff:ffff:ffff:ffff:ffff
19420f1:c100::/2420f1:c1ff:ffff:ffff:ffff:ffff:ffff:ffff
19520f1:c200::/2420f1:c2ff:ffff:ffff:ffff:ffff:ffff:ffff
19620f1:c300::/2420f1:c3ff:ffff:ffff:ffff:ffff:ffff:ffff
19720f1:c400::/2420f1:c4ff:ffff:ffff:ffff:ffff:ffff:ffff
19820f1:c500::/2420f1:c5ff:ffff:ffff:ffff:ffff:ffff:ffff
19920f1:c600::/2420f1:c6ff:ffff:ffff:ffff:ffff:ffff:ffff
20020f1:c700::/2420f1:c7ff:ffff:ffff:ffff:ffff:ffff:ffff
20120f1:c800::/2420f1:c8ff:ffff:ffff:ffff:ffff:ffff:ffff
20220f1:c900::/2420f1:c9ff:ffff:ffff:ffff:ffff:ffff:ffff
20320f1:ca00::/2420f1:caff:ffff:ffff:ffff:ffff:ffff:ffff
20420f1:cb00::/2420f1:cbff:ffff:ffff:ffff:ffff:ffff:ffff
20520f1:cc00::/2420f1:ccff:ffff:ffff:ffff:ffff:ffff:ffff
20620f1:cd00::/2420f1:cdff:ffff:ffff:ffff:ffff:ffff:ffff
20720f1:ce00::/2420f1:ceff:ffff:ffff:ffff:ffff:ffff:ffff
20820f1:cf00::/2420f1:cfff:ffff:ffff:ffff:ffff:ffff:ffff
20920f1:d000::/2420f1:d0ff:ffff:ffff:ffff:ffff:ffff:ffff
21020f1:d100::/2420f1:d1ff:ffff:ffff:ffff:ffff:ffff:ffff
21120f1:d200::/2420f1:d2ff:ffff:ffff:ffff:ffff:ffff:ffff
21220f1:d300::/2420f1:d3ff:ffff:ffff:ffff:ffff:ffff:ffff
21320f1:d400::/2420f1:d4ff:ffff:ffff:ffff:ffff:ffff:ffff
21420f1:d500::/2420f1:d5ff:ffff:ffff:ffff:ffff:ffff:ffff
21520f1:d600::/2420f1:d6ff:ffff:ffff:ffff:ffff:ffff:ffff
21620f1:d700::/2420f1:d7ff:ffff:ffff:ffff:ffff:ffff:ffff
21720f1:d800::/2420f1:d8ff:ffff:ffff:ffff:ffff:ffff:ffff
21820f1:d900::/2420f1:d9ff:ffff:ffff:ffff:ffff:ffff:ffff
21920f1:da00::/2420f1:daff:ffff:ffff:ffff:ffff:ffff:ffff
22020f1:db00::/2420f1:dbff:ffff:ffff:ffff:ffff:ffff:ffff
22120f1:dc00::/2420f1:dcff:ffff:ffff:ffff:ffff:ffff:ffff
22220f1:dd00::/2420f1:ddff:ffff:ffff:ffff:ffff:ffff:ffff
22320f1:de00::/2420f1:deff:ffff:ffff:ffff:ffff:ffff:ffff
22420f1:df00::/2420f1:dfff:ffff:ffff:ffff:ffff:ffff:ffff
22520f1:e000::/2420f1:e0ff:ffff:ffff:ffff:ffff:ffff:ffff
22620f1:e100::/2420f1:e1ff:ffff:ffff:ffff:ffff:ffff:ffff
22720f1:e200::/2420f1:e2ff:ffff:ffff:ffff:ffff:ffff:ffff
22820f1:e300::/2420f1:e3ff:ffff:ffff:ffff:ffff:ffff:ffff
22920f1:e400::/2420f1:e4ff:ffff:ffff:ffff:ffff:ffff:ffff
23020f1:e500::/2420f1:e5ff:ffff:ffff:ffff:ffff:ffff:ffff
23120f1:e600::/2420f1:e6ff:ffff:ffff:ffff:ffff:ffff:ffff
23220f1:e700::/2420f1:e7ff:ffff:ffff:ffff:ffff:ffff:ffff
23320f1:e800::/2420f1:e8ff:ffff:ffff:ffff:ffff:ffff:ffff
23420f1:e900::/2420f1:e9ff:ffff:ffff:ffff:ffff:ffff:ffff
23520f1:ea00::/2420f1:eaff:ffff:ffff:ffff:ffff:ffff:ffff
23620f1:eb00::/2420f1:ebff:ffff:ffff:ffff:ffff:ffff:ffff
23720f1:ec00::/2420f1:ecff:ffff:ffff:ffff:ffff:ffff:ffff
23820f1:ed00::/2420f1:edff:ffff:ffff:ffff:ffff:ffff:ffff
23920f1:ee00::/2420f1:eeff:ffff:ffff:ffff:ffff:ffff:ffff
24020f1:ef00::/2420f1:efff:ffff:ffff:ffff:ffff:ffff:ffff
24120f1:f000::/2420f1:f0ff:ffff:ffff:ffff:ffff:ffff:ffff
24220f1:f100::/2420f1:f1ff:ffff:ffff:ffff:ffff:ffff:ffff
24320f1:f200::/2420f1:f2ff:ffff:ffff:ffff:ffff:ffff:ffff
24420f1:f300::/2420f1:f3ff:ffff:ffff:ffff:ffff:ffff:ffff
24520f1:f400::/2420f1:f4ff:ffff:ffff:ffff:ffff:ffff:ffff
24620f1:f500::/2420f1:f5ff:ffff:ffff:ffff:ffff:ffff:ffff
24720f1:f600::/2420f1:f6ff:ffff:ffff:ffff:ffff:ffff:ffff
24820f1:f700::/2420f1:f7ff:ffff:ffff:ffff:ffff:ffff:ffff
24920f1:f800::/2420f1:f8ff:ffff:ffff:ffff:ffff:ffff:ffff
25020f1:f900::/2420f1:f9ff:ffff:ffff:ffff:ffff:ffff:ffff
25120f1:fa00::/2420f1:faff:ffff:ffff:ffff:ffff:ffff:ffff
25220f1:fb00::/2420f1:fbff:ffff:ffff:ffff:ffff:ffff:ffff
25320f1:fc00::/2420f1:fcff:ffff:ffff:ffff:ffff:ffff:ffff
25420f1:fd00::/2420f1:fdff:ffff:ffff:ffff:ffff:ffff:ffff
25520f1:fe00::/2420f1:feff:ffff:ffff:ffff:ffff:ffff:ffff
25620f1:ff00::/2420f1: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.