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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/16
Addresses2^112
/64 networks2^48
Network
20b5::/16
First address
20b5::
Last address
20b5: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
20b5:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
5.b.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)

20b5::/16 makes 256 subnets of /24.

Subnets
#SubnetLast address
120b5::/2420b5:ff:ffff:ffff:ffff:ffff:ffff:ffff
220b5:100::/2420b5:1ff:ffff:ffff:ffff:ffff:ffff:ffff
320b5:200::/2420b5:2ff:ffff:ffff:ffff:ffff:ffff:ffff
420b5:300::/2420b5:3ff:ffff:ffff:ffff:ffff:ffff:ffff
520b5:400::/2420b5:4ff:ffff:ffff:ffff:ffff:ffff:ffff
620b5:500::/2420b5:5ff:ffff:ffff:ffff:ffff:ffff:ffff
720b5:600::/2420b5:6ff:ffff:ffff:ffff:ffff:ffff:ffff
820b5:700::/2420b5:7ff:ffff:ffff:ffff:ffff:ffff:ffff
920b5:800::/2420b5:8ff:ffff:ffff:ffff:ffff:ffff:ffff
1020b5:900::/2420b5:9ff:ffff:ffff:ffff:ffff:ffff:ffff
1120b5:a00::/2420b5:aff:ffff:ffff:ffff:ffff:ffff:ffff
1220b5:b00::/2420b5:bff:ffff:ffff:ffff:ffff:ffff:ffff
1320b5:c00::/2420b5:cff:ffff:ffff:ffff:ffff:ffff:ffff
1420b5:d00::/2420b5:dff:ffff:ffff:ffff:ffff:ffff:ffff
1520b5:e00::/2420b5:eff:ffff:ffff:ffff:ffff:ffff:ffff
1620b5:f00::/2420b5:fff:ffff:ffff:ffff:ffff:ffff:ffff
1720b5:1000::/2420b5:10ff:ffff:ffff:ffff:ffff:ffff:ffff
1820b5:1100::/2420b5:11ff:ffff:ffff:ffff:ffff:ffff:ffff
1920b5:1200::/2420b5:12ff:ffff:ffff:ffff:ffff:ffff:ffff
2020b5:1300::/2420b5:13ff:ffff:ffff:ffff:ffff:ffff:ffff
2120b5:1400::/2420b5:14ff:ffff:ffff:ffff:ffff:ffff:ffff
2220b5:1500::/2420b5:15ff:ffff:ffff:ffff:ffff:ffff:ffff
2320b5:1600::/2420b5:16ff:ffff:ffff:ffff:ffff:ffff:ffff
2420b5:1700::/2420b5:17ff:ffff:ffff:ffff:ffff:ffff:ffff
2520b5:1800::/2420b5:18ff:ffff:ffff:ffff:ffff:ffff:ffff
2620b5:1900::/2420b5:19ff:ffff:ffff:ffff:ffff:ffff:ffff
2720b5:1a00::/2420b5:1aff:ffff:ffff:ffff:ffff:ffff:ffff
2820b5:1b00::/2420b5:1bff:ffff:ffff:ffff:ffff:ffff:ffff
2920b5:1c00::/2420b5:1cff:ffff:ffff:ffff:ffff:ffff:ffff
3020b5:1d00::/2420b5:1dff:ffff:ffff:ffff:ffff:ffff:ffff
3120b5:1e00::/2420b5:1eff:ffff:ffff:ffff:ffff:ffff:ffff
3220b5:1f00::/2420b5:1fff:ffff:ffff:ffff:ffff:ffff:ffff
3320b5:2000::/2420b5:20ff:ffff:ffff:ffff:ffff:ffff:ffff
3420b5:2100::/2420b5:21ff:ffff:ffff:ffff:ffff:ffff:ffff
3520b5:2200::/2420b5:22ff:ffff:ffff:ffff:ffff:ffff:ffff
3620b5:2300::/2420b5:23ff:ffff:ffff:ffff:ffff:ffff:ffff
3720b5:2400::/2420b5:24ff:ffff:ffff:ffff:ffff:ffff:ffff
3820b5:2500::/2420b5:25ff:ffff:ffff:ffff:ffff:ffff:ffff
3920b5:2600::/2420b5:26ff:ffff:ffff:ffff:ffff:ffff:ffff
4020b5:2700::/2420b5:27ff:ffff:ffff:ffff:ffff:ffff:ffff
4120b5:2800::/2420b5:28ff:ffff:ffff:ffff:ffff:ffff:ffff
4220b5:2900::/2420b5:29ff:ffff:ffff:ffff:ffff:ffff:ffff
4320b5:2a00::/2420b5:2aff:ffff:ffff:ffff:ffff:ffff:ffff
4420b5:2b00::/2420b5:2bff:ffff:ffff:ffff:ffff:ffff:ffff
4520b5:2c00::/2420b5:2cff:ffff:ffff:ffff:ffff:ffff:ffff
4620b5:2d00::/2420b5:2dff:ffff:ffff:ffff:ffff:ffff:ffff
4720b5:2e00::/2420b5:2eff:ffff:ffff:ffff:ffff:ffff:ffff
4820b5:2f00::/2420b5:2fff:ffff:ffff:ffff:ffff:ffff:ffff
4920b5:3000::/2420b5:30ff:ffff:ffff:ffff:ffff:ffff:ffff
5020b5:3100::/2420b5:31ff:ffff:ffff:ffff:ffff:ffff:ffff
5120b5:3200::/2420b5:32ff:ffff:ffff:ffff:ffff:ffff:ffff
5220b5:3300::/2420b5:33ff:ffff:ffff:ffff:ffff:ffff:ffff
5320b5:3400::/2420b5:34ff:ffff:ffff:ffff:ffff:ffff:ffff
5420b5:3500::/2420b5:35ff:ffff:ffff:ffff:ffff:ffff:ffff
5520b5:3600::/2420b5:36ff:ffff:ffff:ffff:ffff:ffff:ffff
5620b5:3700::/2420b5:37ff:ffff:ffff:ffff:ffff:ffff:ffff
5720b5:3800::/2420b5:38ff:ffff:ffff:ffff:ffff:ffff:ffff
5820b5:3900::/2420b5:39ff:ffff:ffff:ffff:ffff:ffff:ffff
5920b5:3a00::/2420b5:3aff:ffff:ffff:ffff:ffff:ffff:ffff
6020b5:3b00::/2420b5:3bff:ffff:ffff:ffff:ffff:ffff:ffff
6120b5:3c00::/2420b5:3cff:ffff:ffff:ffff:ffff:ffff:ffff
6220b5:3d00::/2420b5:3dff:ffff:ffff:ffff:ffff:ffff:ffff
6320b5:3e00::/2420b5:3eff:ffff:ffff:ffff:ffff:ffff:ffff
6420b5:3f00::/2420b5:3fff:ffff:ffff:ffff:ffff:ffff:ffff
6520b5:4000::/2420b5:40ff:ffff:ffff:ffff:ffff:ffff:ffff
6620b5:4100::/2420b5:41ff:ffff:ffff:ffff:ffff:ffff:ffff
6720b5:4200::/2420b5:42ff:ffff:ffff:ffff:ffff:ffff:ffff
6820b5:4300::/2420b5:43ff:ffff:ffff:ffff:ffff:ffff:ffff
6920b5:4400::/2420b5:44ff:ffff:ffff:ffff:ffff:ffff:ffff
7020b5:4500::/2420b5:45ff:ffff:ffff:ffff:ffff:ffff:ffff
7120b5:4600::/2420b5:46ff:ffff:ffff:ffff:ffff:ffff:ffff
7220b5:4700::/2420b5:47ff:ffff:ffff:ffff:ffff:ffff:ffff
7320b5:4800::/2420b5:48ff:ffff:ffff:ffff:ffff:ffff:ffff
7420b5:4900::/2420b5:49ff:ffff:ffff:ffff:ffff:ffff:ffff
7520b5:4a00::/2420b5:4aff:ffff:ffff:ffff:ffff:ffff:ffff
7620b5:4b00::/2420b5:4bff:ffff:ffff:ffff:ffff:ffff:ffff
7720b5:4c00::/2420b5:4cff:ffff:ffff:ffff:ffff:ffff:ffff
7820b5:4d00::/2420b5:4dff:ffff:ffff:ffff:ffff:ffff:ffff
7920b5:4e00::/2420b5:4eff:ffff:ffff:ffff:ffff:ffff:ffff
8020b5:4f00::/2420b5:4fff:ffff:ffff:ffff:ffff:ffff:ffff
8120b5:5000::/2420b5:50ff:ffff:ffff:ffff:ffff:ffff:ffff
8220b5:5100::/2420b5:51ff:ffff:ffff:ffff:ffff:ffff:ffff
8320b5:5200::/2420b5:52ff:ffff:ffff:ffff:ffff:ffff:ffff
8420b5:5300::/2420b5:53ff:ffff:ffff:ffff:ffff:ffff:ffff
8520b5:5400::/2420b5:54ff:ffff:ffff:ffff:ffff:ffff:ffff
8620b5:5500::/2420b5:55ff:ffff:ffff:ffff:ffff:ffff:ffff
8720b5:5600::/2420b5:56ff:ffff:ffff:ffff:ffff:ffff:ffff
8820b5:5700::/2420b5:57ff:ffff:ffff:ffff:ffff:ffff:ffff
8920b5:5800::/2420b5:58ff:ffff:ffff:ffff:ffff:ffff:ffff
9020b5:5900::/2420b5:59ff:ffff:ffff:ffff:ffff:ffff:ffff
9120b5:5a00::/2420b5:5aff:ffff:ffff:ffff:ffff:ffff:ffff
9220b5:5b00::/2420b5:5bff:ffff:ffff:ffff:ffff:ffff:ffff
9320b5:5c00::/2420b5:5cff:ffff:ffff:ffff:ffff:ffff:ffff
9420b5:5d00::/2420b5:5dff:ffff:ffff:ffff:ffff:ffff:ffff
9520b5:5e00::/2420b5:5eff:ffff:ffff:ffff:ffff:ffff:ffff
9620b5:5f00::/2420b5:5fff:ffff:ffff:ffff:ffff:ffff:ffff
9720b5:6000::/2420b5:60ff:ffff:ffff:ffff:ffff:ffff:ffff
9820b5:6100::/2420b5:61ff:ffff:ffff:ffff:ffff:ffff:ffff
9920b5:6200::/2420b5:62ff:ffff:ffff:ffff:ffff:ffff:ffff
10020b5:6300::/2420b5:63ff:ffff:ffff:ffff:ffff:ffff:ffff
10120b5:6400::/2420b5:64ff:ffff:ffff:ffff:ffff:ffff:ffff
10220b5:6500::/2420b5:65ff:ffff:ffff:ffff:ffff:ffff:ffff
10320b5:6600::/2420b5:66ff:ffff:ffff:ffff:ffff:ffff:ffff
10420b5:6700::/2420b5:67ff:ffff:ffff:ffff:ffff:ffff:ffff
10520b5:6800::/2420b5:68ff:ffff:ffff:ffff:ffff:ffff:ffff
10620b5:6900::/2420b5:69ff:ffff:ffff:ffff:ffff:ffff:ffff
10720b5:6a00::/2420b5:6aff:ffff:ffff:ffff:ffff:ffff:ffff
10820b5:6b00::/2420b5:6bff:ffff:ffff:ffff:ffff:ffff:ffff
10920b5:6c00::/2420b5:6cff:ffff:ffff:ffff:ffff:ffff:ffff
11020b5:6d00::/2420b5:6dff:ffff:ffff:ffff:ffff:ffff:ffff
11120b5:6e00::/2420b5:6eff:ffff:ffff:ffff:ffff:ffff:ffff
11220b5:6f00::/2420b5:6fff:ffff:ffff:ffff:ffff:ffff:ffff
11320b5:7000::/2420b5:70ff:ffff:ffff:ffff:ffff:ffff:ffff
11420b5:7100::/2420b5:71ff:ffff:ffff:ffff:ffff:ffff:ffff
11520b5:7200::/2420b5:72ff:ffff:ffff:ffff:ffff:ffff:ffff
11620b5:7300::/2420b5:73ff:ffff:ffff:ffff:ffff:ffff:ffff
11720b5:7400::/2420b5:74ff:ffff:ffff:ffff:ffff:ffff:ffff
11820b5:7500::/2420b5:75ff:ffff:ffff:ffff:ffff:ffff:ffff
11920b5:7600::/2420b5:76ff:ffff:ffff:ffff:ffff:ffff:ffff
12020b5:7700::/2420b5:77ff:ffff:ffff:ffff:ffff:ffff:ffff
12120b5:7800::/2420b5:78ff:ffff:ffff:ffff:ffff:ffff:ffff
12220b5:7900::/2420b5:79ff:ffff:ffff:ffff:ffff:ffff:ffff
12320b5:7a00::/2420b5:7aff:ffff:ffff:ffff:ffff:ffff:ffff
12420b5:7b00::/2420b5:7bff:ffff:ffff:ffff:ffff:ffff:ffff
12520b5:7c00::/2420b5:7cff:ffff:ffff:ffff:ffff:ffff:ffff
12620b5:7d00::/2420b5:7dff:ffff:ffff:ffff:ffff:ffff:ffff
12720b5:7e00::/2420b5:7eff:ffff:ffff:ffff:ffff:ffff:ffff
12820b5:7f00::/2420b5:7fff:ffff:ffff:ffff:ffff:ffff:ffff
12920b5:8000::/2420b5:80ff:ffff:ffff:ffff:ffff:ffff:ffff
13020b5:8100::/2420b5:81ff:ffff:ffff:ffff:ffff:ffff:ffff
13120b5:8200::/2420b5:82ff:ffff:ffff:ffff:ffff:ffff:ffff
13220b5:8300::/2420b5:83ff:ffff:ffff:ffff:ffff:ffff:ffff
13320b5:8400::/2420b5:84ff:ffff:ffff:ffff:ffff:ffff:ffff
13420b5:8500::/2420b5:85ff:ffff:ffff:ffff:ffff:ffff:ffff
13520b5:8600::/2420b5:86ff:ffff:ffff:ffff:ffff:ffff:ffff
13620b5:8700::/2420b5:87ff:ffff:ffff:ffff:ffff:ffff:ffff
13720b5:8800::/2420b5:88ff:ffff:ffff:ffff:ffff:ffff:ffff
13820b5:8900::/2420b5:89ff:ffff:ffff:ffff:ffff:ffff:ffff
13920b5:8a00::/2420b5:8aff:ffff:ffff:ffff:ffff:ffff:ffff
14020b5:8b00::/2420b5:8bff:ffff:ffff:ffff:ffff:ffff:ffff
14120b5:8c00::/2420b5:8cff:ffff:ffff:ffff:ffff:ffff:ffff
14220b5:8d00::/2420b5:8dff:ffff:ffff:ffff:ffff:ffff:ffff
14320b5:8e00::/2420b5:8eff:ffff:ffff:ffff:ffff:ffff:ffff
14420b5:8f00::/2420b5:8fff:ffff:ffff:ffff:ffff:ffff:ffff
14520b5:9000::/2420b5:90ff:ffff:ffff:ffff:ffff:ffff:ffff
14620b5:9100::/2420b5:91ff:ffff:ffff:ffff:ffff:ffff:ffff
14720b5:9200::/2420b5:92ff:ffff:ffff:ffff:ffff:ffff:ffff
14820b5:9300::/2420b5:93ff:ffff:ffff:ffff:ffff:ffff:ffff
14920b5:9400::/2420b5:94ff:ffff:ffff:ffff:ffff:ffff:ffff
15020b5:9500::/2420b5:95ff:ffff:ffff:ffff:ffff:ffff:ffff
15120b5:9600::/2420b5:96ff:ffff:ffff:ffff:ffff:ffff:ffff
15220b5:9700::/2420b5:97ff:ffff:ffff:ffff:ffff:ffff:ffff
15320b5:9800::/2420b5:98ff:ffff:ffff:ffff:ffff:ffff:ffff
15420b5:9900::/2420b5:99ff:ffff:ffff:ffff:ffff:ffff:ffff
15520b5:9a00::/2420b5:9aff:ffff:ffff:ffff:ffff:ffff:ffff
15620b5:9b00::/2420b5:9bff:ffff:ffff:ffff:ffff:ffff:ffff
15720b5:9c00::/2420b5:9cff:ffff:ffff:ffff:ffff:ffff:ffff
15820b5:9d00::/2420b5:9dff:ffff:ffff:ffff:ffff:ffff:ffff
15920b5:9e00::/2420b5:9eff:ffff:ffff:ffff:ffff:ffff:ffff
16020b5:9f00::/2420b5:9fff:ffff:ffff:ffff:ffff:ffff:ffff
16120b5:a000::/2420b5:a0ff:ffff:ffff:ffff:ffff:ffff:ffff
16220b5:a100::/2420b5:a1ff:ffff:ffff:ffff:ffff:ffff:ffff
16320b5:a200::/2420b5:a2ff:ffff:ffff:ffff:ffff:ffff:ffff
16420b5:a300::/2420b5:a3ff:ffff:ffff:ffff:ffff:ffff:ffff
16520b5:a400::/2420b5:a4ff:ffff:ffff:ffff:ffff:ffff:ffff
16620b5:a500::/2420b5:a5ff:ffff:ffff:ffff:ffff:ffff:ffff
16720b5:a600::/2420b5:a6ff:ffff:ffff:ffff:ffff:ffff:ffff
16820b5:a700::/2420b5:a7ff:ffff:ffff:ffff:ffff:ffff:ffff
16920b5:a800::/2420b5:a8ff:ffff:ffff:ffff:ffff:ffff:ffff
17020b5:a900::/2420b5:a9ff:ffff:ffff:ffff:ffff:ffff:ffff
17120b5:aa00::/2420b5:aaff:ffff:ffff:ffff:ffff:ffff:ffff
17220b5:ab00::/2420b5:abff:ffff:ffff:ffff:ffff:ffff:ffff
17320b5:ac00::/2420b5:acff:ffff:ffff:ffff:ffff:ffff:ffff
17420b5:ad00::/2420b5:adff:ffff:ffff:ffff:ffff:ffff:ffff
17520b5:ae00::/2420b5:aeff:ffff:ffff:ffff:ffff:ffff:ffff
17620b5:af00::/2420b5:afff:ffff:ffff:ffff:ffff:ffff:ffff
17720b5:b000::/2420b5:b0ff:ffff:ffff:ffff:ffff:ffff:ffff
17820b5:b100::/2420b5:b1ff:ffff:ffff:ffff:ffff:ffff:ffff
17920b5:b200::/2420b5:b2ff:ffff:ffff:ffff:ffff:ffff:ffff
18020b5:b300::/2420b5:b3ff:ffff:ffff:ffff:ffff:ffff:ffff
18120b5:b400::/2420b5:b4ff:ffff:ffff:ffff:ffff:ffff:ffff
18220b5:b500::/2420b5:b5ff:ffff:ffff:ffff:ffff:ffff:ffff
18320b5:b600::/2420b5:b6ff:ffff:ffff:ffff:ffff:ffff:ffff
18420b5:b700::/2420b5:b7ff:ffff:ffff:ffff:ffff:ffff:ffff
18520b5:b800::/2420b5:b8ff:ffff:ffff:ffff:ffff:ffff:ffff
18620b5:b900::/2420b5:b9ff:ffff:ffff:ffff:ffff:ffff:ffff
18720b5:ba00::/2420b5:baff:ffff:ffff:ffff:ffff:ffff:ffff
18820b5:bb00::/2420b5:bbff:ffff:ffff:ffff:ffff:ffff:ffff
18920b5:bc00::/2420b5:bcff:ffff:ffff:ffff:ffff:ffff:ffff
19020b5:bd00::/2420b5:bdff:ffff:ffff:ffff:ffff:ffff:ffff
19120b5:be00::/2420b5:beff:ffff:ffff:ffff:ffff:ffff:ffff
19220b5:bf00::/2420b5:bfff:ffff:ffff:ffff:ffff:ffff:ffff
19320b5:c000::/2420b5:c0ff:ffff:ffff:ffff:ffff:ffff:ffff
19420b5:c100::/2420b5:c1ff:ffff:ffff:ffff:ffff:ffff:ffff
19520b5:c200::/2420b5:c2ff:ffff:ffff:ffff:ffff:ffff:ffff
19620b5:c300::/2420b5:c3ff:ffff:ffff:ffff:ffff:ffff:ffff
19720b5:c400::/2420b5:c4ff:ffff:ffff:ffff:ffff:ffff:ffff
19820b5:c500::/2420b5:c5ff:ffff:ffff:ffff:ffff:ffff:ffff
19920b5:c600::/2420b5:c6ff:ffff:ffff:ffff:ffff:ffff:ffff
20020b5:c700::/2420b5:c7ff:ffff:ffff:ffff:ffff:ffff:ffff
20120b5:c800::/2420b5:c8ff:ffff:ffff:ffff:ffff:ffff:ffff
20220b5:c900::/2420b5:c9ff:ffff:ffff:ffff:ffff:ffff:ffff
20320b5:ca00::/2420b5:caff:ffff:ffff:ffff:ffff:ffff:ffff
20420b5:cb00::/2420b5:cbff:ffff:ffff:ffff:ffff:ffff:ffff
20520b5:cc00::/2420b5:ccff:ffff:ffff:ffff:ffff:ffff:ffff
20620b5:cd00::/2420b5:cdff:ffff:ffff:ffff:ffff:ffff:ffff
20720b5:ce00::/2420b5:ceff:ffff:ffff:ffff:ffff:ffff:ffff
20820b5:cf00::/2420b5:cfff:ffff:ffff:ffff:ffff:ffff:ffff
20920b5:d000::/2420b5:d0ff:ffff:ffff:ffff:ffff:ffff:ffff
21020b5:d100::/2420b5:d1ff:ffff:ffff:ffff:ffff:ffff:ffff
21120b5:d200::/2420b5:d2ff:ffff:ffff:ffff:ffff:ffff:ffff
21220b5:d300::/2420b5:d3ff:ffff:ffff:ffff:ffff:ffff:ffff
21320b5:d400::/2420b5:d4ff:ffff:ffff:ffff:ffff:ffff:ffff
21420b5:d500::/2420b5:d5ff:ffff:ffff:ffff:ffff:ffff:ffff
21520b5:d600::/2420b5:d6ff:ffff:ffff:ffff:ffff:ffff:ffff
21620b5:d700::/2420b5:d7ff:ffff:ffff:ffff:ffff:ffff:ffff
21720b5:d800::/2420b5:d8ff:ffff:ffff:ffff:ffff:ffff:ffff
21820b5:d900::/2420b5:d9ff:ffff:ffff:ffff:ffff:ffff:ffff
21920b5:da00::/2420b5:daff:ffff:ffff:ffff:ffff:ffff:ffff
22020b5:db00::/2420b5:dbff:ffff:ffff:ffff:ffff:ffff:ffff
22120b5:dc00::/2420b5:dcff:ffff:ffff:ffff:ffff:ffff:ffff
22220b5:dd00::/2420b5:ddff:ffff:ffff:ffff:ffff:ffff:ffff
22320b5:de00::/2420b5:deff:ffff:ffff:ffff:ffff:ffff:ffff
22420b5:df00::/2420b5:dfff:ffff:ffff:ffff:ffff:ffff:ffff
22520b5:e000::/2420b5:e0ff:ffff:ffff:ffff:ffff:ffff:ffff
22620b5:e100::/2420b5:e1ff:ffff:ffff:ffff:ffff:ffff:ffff
22720b5:e200::/2420b5:e2ff:ffff:ffff:ffff:ffff:ffff:ffff
22820b5:e300::/2420b5:e3ff:ffff:ffff:ffff:ffff:ffff:ffff
22920b5:e400::/2420b5:e4ff:ffff:ffff:ffff:ffff:ffff:ffff
23020b5:e500::/2420b5:e5ff:ffff:ffff:ffff:ffff:ffff:ffff
23120b5:e600::/2420b5:e6ff:ffff:ffff:ffff:ffff:ffff:ffff
23220b5:e700::/2420b5:e7ff:ffff:ffff:ffff:ffff:ffff:ffff
23320b5:e800::/2420b5:e8ff:ffff:ffff:ffff:ffff:ffff:ffff
23420b5:e900::/2420b5:e9ff:ffff:ffff:ffff:ffff:ffff:ffff
23520b5:ea00::/2420b5:eaff:ffff:ffff:ffff:ffff:ffff:ffff
23620b5:eb00::/2420b5:ebff:ffff:ffff:ffff:ffff:ffff:ffff
23720b5:ec00::/2420b5:ecff:ffff:ffff:ffff:ffff:ffff:ffff
23820b5:ed00::/2420b5:edff:ffff:ffff:ffff:ffff:ffff:ffff
23920b5:ee00::/2420b5:eeff:ffff:ffff:ffff:ffff:ffff:ffff
24020b5:ef00::/2420b5:efff:ffff:ffff:ffff:ffff:ffff:ffff
24120b5:f000::/2420b5:f0ff:ffff:ffff:ffff:ffff:ffff:ffff
24220b5:f100::/2420b5:f1ff:ffff:ffff:ffff:ffff:ffff:ffff
24320b5:f200::/2420b5:f2ff:ffff:ffff:ffff:ffff:ffff:ffff
24420b5:f300::/2420b5:f3ff:ffff:ffff:ffff:ffff:ffff:ffff
24520b5:f400::/2420b5:f4ff:ffff:ffff:ffff:ffff:ffff:ffff
24620b5:f500::/2420b5:f5ff:ffff:ffff:ffff:ffff:ffff:ffff
24720b5:f600::/2420b5:f6ff:ffff:ffff:ffff:ffff:ffff:ffff
24820b5:f700::/2420b5:f7ff:ffff:ffff:ffff:ffff:ffff:ffff
24920b5:f800::/2420b5:f8ff:ffff:ffff:ffff:ffff:ffff:ffff
25020b5:f900::/2420b5:f9ff:ffff:ffff:ffff:ffff:ffff:ffff
25120b5:fa00::/2420b5:faff:ffff:ffff:ffff:ffff:ffff:ffff
25220b5:fb00::/2420b5:fbff:ffff:ffff:ffff:ffff:ffff:ffff
25320b5:fc00::/2420b5:fcff:ffff:ffff:ffff:ffff:ffff:ffff
25420b5:fd00::/2420b5:fdff:ffff:ffff:ffff:ffff:ffff:ffff
25520b5:fe00::/2420b5:feff:ffff:ffff:ffff:ffff:ffff:ffff
25620b5:ff00::/2420b5: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.