Speed and call quality testMy IP addressIP subnet calculatorDNS reportWhoIs lookupRemote support

Internet and network

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.

Computers and devices

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.

Make and print

Clean textStrip hidden characters, smart quotes and odd spaces from pasted text.QR code makerMake a QR code for a link, contact or message. Nothing leaves your browser.Wi-Fi QR posterPrint an A4 poster that lets guests join your Wi-Fi by scanning.

Surftec support

Remote supportLet a Surftec engineer connect to your computer to help you.All workingA full-screen confirmation that everything is up and running.

Surftec

Surftec websiteServices, news and how to contact Surftec
Cloud Tools
Guest
GuestNot signed in

Surftec customers will be recognised automatically when they use these tools from their office network.

Customer sign-in is coming soon.

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/12
Addresses2^116
/64 networks2^52
Network
2310::/12
First address
2310::
Last address
231f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
83,076,749,736,557,242,056,487,941,267,521,536 (2^116)
/64 networks (LANs)
4,503,599,627,370,496 (2^52)
Full form
2310:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
1.3.2.ip6.arpa
Split into smaller subnets/24
/13 (2)/14 (4)/15 (8)/16 (16)/20 (256)/24 (4,096)/28 (65,536)

2310::/12 makes 4,096 subnets of /24; the first 256 are listed.

Subnets
#SubnetLast address
12310::/242310:ff:ffff:ffff:ffff:ffff:ffff:ffff
22310:100::/242310:1ff:ffff:ffff:ffff:ffff:ffff:ffff
32310:200::/242310:2ff:ffff:ffff:ffff:ffff:ffff:ffff
42310:300::/242310:3ff:ffff:ffff:ffff:ffff:ffff:ffff
52310:400::/242310:4ff:ffff:ffff:ffff:ffff:ffff:ffff
62310:500::/242310:5ff:ffff:ffff:ffff:ffff:ffff:ffff
72310:600::/242310:6ff:ffff:ffff:ffff:ffff:ffff:ffff
82310:700::/242310:7ff:ffff:ffff:ffff:ffff:ffff:ffff
92310:800::/242310:8ff:ffff:ffff:ffff:ffff:ffff:ffff
102310:900::/242310:9ff:ffff:ffff:ffff:ffff:ffff:ffff
112310:a00::/242310:aff:ffff:ffff:ffff:ffff:ffff:ffff
122310:b00::/242310:bff:ffff:ffff:ffff:ffff:ffff:ffff
132310:c00::/242310:cff:ffff:ffff:ffff:ffff:ffff:ffff
142310:d00::/242310:dff:ffff:ffff:ffff:ffff:ffff:ffff
152310:e00::/242310:eff:ffff:ffff:ffff:ffff:ffff:ffff
162310:f00::/242310:fff:ffff:ffff:ffff:ffff:ffff:ffff
172310:1000::/242310:10ff:ffff:ffff:ffff:ffff:ffff:ffff
182310:1100::/242310:11ff:ffff:ffff:ffff:ffff:ffff:ffff
192310:1200::/242310:12ff:ffff:ffff:ffff:ffff:ffff:ffff
202310:1300::/242310:13ff:ffff:ffff:ffff:ffff:ffff:ffff
212310:1400::/242310:14ff:ffff:ffff:ffff:ffff:ffff:ffff
222310:1500::/242310:15ff:ffff:ffff:ffff:ffff:ffff:ffff
232310:1600::/242310:16ff:ffff:ffff:ffff:ffff:ffff:ffff
242310:1700::/242310:17ff:ffff:ffff:ffff:ffff:ffff:ffff
252310:1800::/242310:18ff:ffff:ffff:ffff:ffff:ffff:ffff
262310:1900::/242310:19ff:ffff:ffff:ffff:ffff:ffff:ffff
272310:1a00::/242310:1aff:ffff:ffff:ffff:ffff:ffff:ffff
282310:1b00::/242310:1bff:ffff:ffff:ffff:ffff:ffff:ffff
292310:1c00::/242310:1cff:ffff:ffff:ffff:ffff:ffff:ffff
302310:1d00::/242310:1dff:ffff:ffff:ffff:ffff:ffff:ffff
312310:1e00::/242310:1eff:ffff:ffff:ffff:ffff:ffff:ffff
322310:1f00::/242310:1fff:ffff:ffff:ffff:ffff:ffff:ffff
332310:2000::/242310:20ff:ffff:ffff:ffff:ffff:ffff:ffff
342310:2100::/242310:21ff:ffff:ffff:ffff:ffff:ffff:ffff
352310:2200::/242310:22ff:ffff:ffff:ffff:ffff:ffff:ffff
362310:2300::/242310:23ff:ffff:ffff:ffff:ffff:ffff:ffff
372310:2400::/242310:24ff:ffff:ffff:ffff:ffff:ffff:ffff
382310:2500::/242310:25ff:ffff:ffff:ffff:ffff:ffff:ffff
392310:2600::/242310:26ff:ffff:ffff:ffff:ffff:ffff:ffff
402310:2700::/242310:27ff:ffff:ffff:ffff:ffff:ffff:ffff
412310:2800::/242310:28ff:ffff:ffff:ffff:ffff:ffff:ffff
422310:2900::/242310:29ff:ffff:ffff:ffff:ffff:ffff:ffff
432310:2a00::/242310:2aff:ffff:ffff:ffff:ffff:ffff:ffff
442310:2b00::/242310:2bff:ffff:ffff:ffff:ffff:ffff:ffff
452310:2c00::/242310:2cff:ffff:ffff:ffff:ffff:ffff:ffff
462310:2d00::/242310:2dff:ffff:ffff:ffff:ffff:ffff:ffff
472310:2e00::/242310:2eff:ffff:ffff:ffff:ffff:ffff:ffff
482310:2f00::/242310:2fff:ffff:ffff:ffff:ffff:ffff:ffff
492310:3000::/242310:30ff:ffff:ffff:ffff:ffff:ffff:ffff
502310:3100::/242310:31ff:ffff:ffff:ffff:ffff:ffff:ffff
512310:3200::/242310:32ff:ffff:ffff:ffff:ffff:ffff:ffff
522310:3300::/242310:33ff:ffff:ffff:ffff:ffff:ffff:ffff
532310:3400::/242310:34ff:ffff:ffff:ffff:ffff:ffff:ffff
542310:3500::/242310:35ff:ffff:ffff:ffff:ffff:ffff:ffff
552310:3600::/242310:36ff:ffff:ffff:ffff:ffff:ffff:ffff
562310:3700::/242310:37ff:ffff:ffff:ffff:ffff:ffff:ffff
572310:3800::/242310:38ff:ffff:ffff:ffff:ffff:ffff:ffff
582310:3900::/242310:39ff:ffff:ffff:ffff:ffff:ffff:ffff
592310:3a00::/242310:3aff:ffff:ffff:ffff:ffff:ffff:ffff
602310:3b00::/242310:3bff:ffff:ffff:ffff:ffff:ffff:ffff
612310:3c00::/242310:3cff:ffff:ffff:ffff:ffff:ffff:ffff
622310:3d00::/242310:3dff:ffff:ffff:ffff:ffff:ffff:ffff
632310:3e00::/242310:3eff:ffff:ffff:ffff:ffff:ffff:ffff
642310:3f00::/242310:3fff:ffff:ffff:ffff:ffff:ffff:ffff
652310:4000::/242310:40ff:ffff:ffff:ffff:ffff:ffff:ffff
662310:4100::/242310:41ff:ffff:ffff:ffff:ffff:ffff:ffff
672310:4200::/242310:42ff:ffff:ffff:ffff:ffff:ffff:ffff
682310:4300::/242310:43ff:ffff:ffff:ffff:ffff:ffff:ffff
692310:4400::/242310:44ff:ffff:ffff:ffff:ffff:ffff:ffff
702310:4500::/242310:45ff:ffff:ffff:ffff:ffff:ffff:ffff
712310:4600::/242310:46ff:ffff:ffff:ffff:ffff:ffff:ffff
722310:4700::/242310:47ff:ffff:ffff:ffff:ffff:ffff:ffff
732310:4800::/242310:48ff:ffff:ffff:ffff:ffff:ffff:ffff
742310:4900::/242310:49ff:ffff:ffff:ffff:ffff:ffff:ffff
752310:4a00::/242310:4aff:ffff:ffff:ffff:ffff:ffff:ffff
762310:4b00::/242310:4bff:ffff:ffff:ffff:ffff:ffff:ffff
772310:4c00::/242310:4cff:ffff:ffff:ffff:ffff:ffff:ffff
782310:4d00::/242310:4dff:ffff:ffff:ffff:ffff:ffff:ffff
792310:4e00::/242310:4eff:ffff:ffff:ffff:ffff:ffff:ffff
802310:4f00::/242310:4fff:ffff:ffff:ffff:ffff:ffff:ffff
812310:5000::/242310:50ff:ffff:ffff:ffff:ffff:ffff:ffff
822310:5100::/242310:51ff:ffff:ffff:ffff:ffff:ffff:ffff
832310:5200::/242310:52ff:ffff:ffff:ffff:ffff:ffff:ffff
842310:5300::/242310:53ff:ffff:ffff:ffff:ffff:ffff:ffff
852310:5400::/242310:54ff:ffff:ffff:ffff:ffff:ffff:ffff
862310:5500::/242310:55ff:ffff:ffff:ffff:ffff:ffff:ffff
872310:5600::/242310:56ff:ffff:ffff:ffff:ffff:ffff:ffff
882310:5700::/242310:57ff:ffff:ffff:ffff:ffff:ffff:ffff
892310:5800::/242310:58ff:ffff:ffff:ffff:ffff:ffff:ffff
902310:5900::/242310:59ff:ffff:ffff:ffff:ffff:ffff:ffff
912310:5a00::/242310:5aff:ffff:ffff:ffff:ffff:ffff:ffff
922310:5b00::/242310:5bff:ffff:ffff:ffff:ffff:ffff:ffff
932310:5c00::/242310:5cff:ffff:ffff:ffff:ffff:ffff:ffff
942310:5d00::/242310:5dff:ffff:ffff:ffff:ffff:ffff:ffff
952310:5e00::/242310:5eff:ffff:ffff:ffff:ffff:ffff:ffff
962310:5f00::/242310:5fff:ffff:ffff:ffff:ffff:ffff:ffff
972310:6000::/242310:60ff:ffff:ffff:ffff:ffff:ffff:ffff
982310:6100::/242310:61ff:ffff:ffff:ffff:ffff:ffff:ffff
992310:6200::/242310:62ff:ffff:ffff:ffff:ffff:ffff:ffff
1002310:6300::/242310:63ff:ffff:ffff:ffff:ffff:ffff:ffff
1012310:6400::/242310:64ff:ffff:ffff:ffff:ffff:ffff:ffff
1022310:6500::/242310:65ff:ffff:ffff:ffff:ffff:ffff:ffff
1032310:6600::/242310:66ff:ffff:ffff:ffff:ffff:ffff:ffff
1042310:6700::/242310:67ff:ffff:ffff:ffff:ffff:ffff:ffff
1052310:6800::/242310:68ff:ffff:ffff:ffff:ffff:ffff:ffff
1062310:6900::/242310:69ff:ffff:ffff:ffff:ffff:ffff:ffff
1072310:6a00::/242310:6aff:ffff:ffff:ffff:ffff:ffff:ffff
1082310:6b00::/242310:6bff:ffff:ffff:ffff:ffff:ffff:ffff
1092310:6c00::/242310:6cff:ffff:ffff:ffff:ffff:ffff:ffff
1102310:6d00::/242310:6dff:ffff:ffff:ffff:ffff:ffff:ffff
1112310:6e00::/242310:6eff:ffff:ffff:ffff:ffff:ffff:ffff
1122310:6f00::/242310:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1132310:7000::/242310:70ff:ffff:ffff:ffff:ffff:ffff:ffff
1142310:7100::/242310:71ff:ffff:ffff:ffff:ffff:ffff:ffff
1152310:7200::/242310:72ff:ffff:ffff:ffff:ffff:ffff:ffff
1162310:7300::/242310:73ff:ffff:ffff:ffff:ffff:ffff:ffff
1172310:7400::/242310:74ff:ffff:ffff:ffff:ffff:ffff:ffff
1182310:7500::/242310:75ff:ffff:ffff:ffff:ffff:ffff:ffff
1192310:7600::/242310:76ff:ffff:ffff:ffff:ffff:ffff:ffff
1202310:7700::/242310:77ff:ffff:ffff:ffff:ffff:ffff:ffff
1212310:7800::/242310:78ff:ffff:ffff:ffff:ffff:ffff:ffff
1222310:7900::/242310:79ff:ffff:ffff:ffff:ffff:ffff:ffff
1232310:7a00::/242310:7aff:ffff:ffff:ffff:ffff:ffff:ffff
1242310:7b00::/242310:7bff:ffff:ffff:ffff:ffff:ffff:ffff
1252310:7c00::/242310:7cff:ffff:ffff:ffff:ffff:ffff:ffff
1262310:7d00::/242310:7dff:ffff:ffff:ffff:ffff:ffff:ffff
1272310:7e00::/242310:7eff:ffff:ffff:ffff:ffff:ffff:ffff
1282310:7f00::/242310:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1292310:8000::/242310:80ff:ffff:ffff:ffff:ffff:ffff:ffff
1302310:8100::/242310:81ff:ffff:ffff:ffff:ffff:ffff:ffff
1312310:8200::/242310:82ff:ffff:ffff:ffff:ffff:ffff:ffff
1322310:8300::/242310:83ff:ffff:ffff:ffff:ffff:ffff:ffff
1332310:8400::/242310:84ff:ffff:ffff:ffff:ffff:ffff:ffff
1342310:8500::/242310:85ff:ffff:ffff:ffff:ffff:ffff:ffff
1352310:8600::/242310:86ff:ffff:ffff:ffff:ffff:ffff:ffff
1362310:8700::/242310:87ff:ffff:ffff:ffff:ffff:ffff:ffff
1372310:8800::/242310:88ff:ffff:ffff:ffff:ffff:ffff:ffff
1382310:8900::/242310:89ff:ffff:ffff:ffff:ffff:ffff:ffff
1392310:8a00::/242310:8aff:ffff:ffff:ffff:ffff:ffff:ffff
1402310:8b00::/242310:8bff:ffff:ffff:ffff:ffff:ffff:ffff
1412310:8c00::/242310:8cff:ffff:ffff:ffff:ffff:ffff:ffff
1422310:8d00::/242310:8dff:ffff:ffff:ffff:ffff:ffff:ffff
1432310:8e00::/242310:8eff:ffff:ffff:ffff:ffff:ffff:ffff
1442310:8f00::/242310:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1452310:9000::/242310:90ff:ffff:ffff:ffff:ffff:ffff:ffff
1462310:9100::/242310:91ff:ffff:ffff:ffff:ffff:ffff:ffff
1472310:9200::/242310:92ff:ffff:ffff:ffff:ffff:ffff:ffff
1482310:9300::/242310:93ff:ffff:ffff:ffff:ffff:ffff:ffff
1492310:9400::/242310:94ff:ffff:ffff:ffff:ffff:ffff:ffff
1502310:9500::/242310:95ff:ffff:ffff:ffff:ffff:ffff:ffff
1512310:9600::/242310:96ff:ffff:ffff:ffff:ffff:ffff:ffff
1522310:9700::/242310:97ff:ffff:ffff:ffff:ffff:ffff:ffff
1532310:9800::/242310:98ff:ffff:ffff:ffff:ffff:ffff:ffff
1542310:9900::/242310:99ff:ffff:ffff:ffff:ffff:ffff:ffff
1552310:9a00::/242310:9aff:ffff:ffff:ffff:ffff:ffff:ffff
1562310:9b00::/242310:9bff:ffff:ffff:ffff:ffff:ffff:ffff
1572310:9c00::/242310:9cff:ffff:ffff:ffff:ffff:ffff:ffff
1582310:9d00::/242310:9dff:ffff:ffff:ffff:ffff:ffff:ffff
1592310:9e00::/242310:9eff:ffff:ffff:ffff:ffff:ffff:ffff
1602310:9f00::/242310:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1612310:a000::/242310:a0ff:ffff:ffff:ffff:ffff:ffff:ffff
1622310:a100::/242310:a1ff:ffff:ffff:ffff:ffff:ffff:ffff
1632310:a200::/242310:a2ff:ffff:ffff:ffff:ffff:ffff:ffff
1642310:a300::/242310:a3ff:ffff:ffff:ffff:ffff:ffff:ffff
1652310:a400::/242310:a4ff:ffff:ffff:ffff:ffff:ffff:ffff
1662310:a500::/242310:a5ff:ffff:ffff:ffff:ffff:ffff:ffff
1672310:a600::/242310:a6ff:ffff:ffff:ffff:ffff:ffff:ffff
1682310:a700::/242310:a7ff:ffff:ffff:ffff:ffff:ffff:ffff
1692310:a800::/242310:a8ff:ffff:ffff:ffff:ffff:ffff:ffff
1702310:a900::/242310:a9ff:ffff:ffff:ffff:ffff:ffff:ffff
1712310:aa00::/242310:aaff:ffff:ffff:ffff:ffff:ffff:ffff
1722310:ab00::/242310:abff:ffff:ffff:ffff:ffff:ffff:ffff
1732310:ac00::/242310:acff:ffff:ffff:ffff:ffff:ffff:ffff
1742310:ad00::/242310:adff:ffff:ffff:ffff:ffff:ffff:ffff
1752310:ae00::/242310:aeff:ffff:ffff:ffff:ffff:ffff:ffff
1762310:af00::/242310:afff:ffff:ffff:ffff:ffff:ffff:ffff
1772310:b000::/242310:b0ff:ffff:ffff:ffff:ffff:ffff:ffff
1782310:b100::/242310:b1ff:ffff:ffff:ffff:ffff:ffff:ffff
1792310:b200::/242310:b2ff:ffff:ffff:ffff:ffff:ffff:ffff
1802310:b300::/242310:b3ff:ffff:ffff:ffff:ffff:ffff:ffff
1812310:b400::/242310:b4ff:ffff:ffff:ffff:ffff:ffff:ffff
1822310:b500::/242310:b5ff:ffff:ffff:ffff:ffff:ffff:ffff
1832310:b600::/242310:b6ff:ffff:ffff:ffff:ffff:ffff:ffff
1842310:b700::/242310:b7ff:ffff:ffff:ffff:ffff:ffff:ffff
1852310:b800::/242310:b8ff:ffff:ffff:ffff:ffff:ffff:ffff
1862310:b900::/242310:b9ff:ffff:ffff:ffff:ffff:ffff:ffff
1872310:ba00::/242310:baff:ffff:ffff:ffff:ffff:ffff:ffff
1882310:bb00::/242310:bbff:ffff:ffff:ffff:ffff:ffff:ffff
1892310:bc00::/242310:bcff:ffff:ffff:ffff:ffff:ffff:ffff
1902310:bd00::/242310:bdff:ffff:ffff:ffff:ffff:ffff:ffff
1912310:be00::/242310:beff:ffff:ffff:ffff:ffff:ffff:ffff
1922310:bf00::/242310:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1932310:c000::/242310:c0ff:ffff:ffff:ffff:ffff:ffff:ffff
1942310:c100::/242310:c1ff:ffff:ffff:ffff:ffff:ffff:ffff
1952310:c200::/242310:c2ff:ffff:ffff:ffff:ffff:ffff:ffff
1962310:c300::/242310:c3ff:ffff:ffff:ffff:ffff:ffff:ffff
1972310:c400::/242310:c4ff:ffff:ffff:ffff:ffff:ffff:ffff
1982310:c500::/242310:c5ff:ffff:ffff:ffff:ffff:ffff:ffff
1992310:c600::/242310:c6ff:ffff:ffff:ffff:ffff:ffff:ffff
2002310:c700::/242310:c7ff:ffff:ffff:ffff:ffff:ffff:ffff
2012310:c800::/242310:c8ff:ffff:ffff:ffff:ffff:ffff:ffff
2022310:c900::/242310:c9ff:ffff:ffff:ffff:ffff:ffff:ffff
2032310:ca00::/242310:caff:ffff:ffff:ffff:ffff:ffff:ffff
2042310:cb00::/242310:cbff:ffff:ffff:ffff:ffff:ffff:ffff
2052310:cc00::/242310:ccff:ffff:ffff:ffff:ffff:ffff:ffff
2062310:cd00::/242310:cdff:ffff:ffff:ffff:ffff:ffff:ffff
2072310:ce00::/242310:ceff:ffff:ffff:ffff:ffff:ffff:ffff
2082310:cf00::/242310:cfff:ffff:ffff:ffff:ffff:ffff:ffff
2092310:d000::/242310:d0ff:ffff:ffff:ffff:ffff:ffff:ffff
2102310:d100::/242310:d1ff:ffff:ffff:ffff:ffff:ffff:ffff
2112310:d200::/242310:d2ff:ffff:ffff:ffff:ffff:ffff:ffff
2122310:d300::/242310:d3ff:ffff:ffff:ffff:ffff:ffff:ffff
2132310:d400::/242310:d4ff:ffff:ffff:ffff:ffff:ffff:ffff
2142310:d500::/242310:d5ff:ffff:ffff:ffff:ffff:ffff:ffff
2152310:d600::/242310:d6ff:ffff:ffff:ffff:ffff:ffff:ffff
2162310:d700::/242310:d7ff:ffff:ffff:ffff:ffff:ffff:ffff
2172310:d800::/242310:d8ff:ffff:ffff:ffff:ffff:ffff:ffff
2182310:d900::/242310:d9ff:ffff:ffff:ffff:ffff:ffff:ffff
2192310:da00::/242310:daff:ffff:ffff:ffff:ffff:ffff:ffff
2202310:db00::/242310:dbff:ffff:ffff:ffff:ffff:ffff:ffff
2212310:dc00::/242310:dcff:ffff:ffff:ffff:ffff:ffff:ffff
2222310:dd00::/242310:ddff:ffff:ffff:ffff:ffff:ffff:ffff
2232310:de00::/242310:deff:ffff:ffff:ffff:ffff:ffff:ffff
2242310:df00::/242310:dfff:ffff:ffff:ffff:ffff:ffff:ffff
2252310:e000::/242310:e0ff:ffff:ffff:ffff:ffff:ffff:ffff
2262310:e100::/242310:e1ff:ffff:ffff:ffff:ffff:ffff:ffff
2272310:e200::/242310:e2ff:ffff:ffff:ffff:ffff:ffff:ffff
2282310:e300::/242310:e3ff:ffff:ffff:ffff:ffff:ffff:ffff
2292310:e400::/242310:e4ff:ffff:ffff:ffff:ffff:ffff:ffff
2302310:e500::/242310:e5ff:ffff:ffff:ffff:ffff:ffff:ffff
2312310:e600::/242310:e6ff:ffff:ffff:ffff:ffff:ffff:ffff
2322310:e700::/242310:e7ff:ffff:ffff:ffff:ffff:ffff:ffff
2332310:e800::/242310:e8ff:ffff:ffff:ffff:ffff:ffff:ffff
2342310:e900::/242310:e9ff:ffff:ffff:ffff:ffff:ffff:ffff
2352310:ea00::/242310:eaff:ffff:ffff:ffff:ffff:ffff:ffff
2362310:eb00::/242310:ebff:ffff:ffff:ffff:ffff:ffff:ffff
2372310:ec00::/242310:ecff:ffff:ffff:ffff:ffff:ffff:ffff
2382310:ed00::/242310:edff:ffff:ffff:ffff:ffff:ffff:ffff
2392310:ee00::/242310:eeff:ffff:ffff:ffff:ffff:ffff:ffff
2402310:ef00::/242310:efff:ffff:ffff:ffff:ffff:ffff:ffff
2412310:f000::/242310:f0ff:ffff:ffff:ffff:ffff:ffff:ffff
2422310:f100::/242310:f1ff:ffff:ffff:ffff:ffff:ffff:ffff
2432310:f200::/242310:f2ff:ffff:ffff:ffff:ffff:ffff:ffff
2442310:f300::/242310:f3ff:ffff:ffff:ffff:ffff:ffff:ffff
2452310:f400::/242310:f4ff:ffff:ffff:ffff:ffff:ffff:ffff
2462310:f500::/242310:f5ff:ffff:ffff:ffff:ffff:ffff:ffff
2472310:f600::/242310:f6ff:ffff:ffff:ffff:ffff:ffff:ffff
2482310:f700::/242310:f7ff:ffff:ffff:ffff:ffff:ffff:ffff
2492310:f800::/242310:f8ff:ffff:ffff:ffff:ffff:ffff:ffff
2502310:f900::/242310:f9ff:ffff:ffff:ffff:ffff:ffff:ffff
2512310:fa00::/242310:faff:ffff:ffff:ffff:ffff:ffff:ffff
2522310:fb00::/242310:fbff:ffff:ffff:ffff:ffff:ffff:ffff
2532310:fc00::/242310:fcff:ffff:ffff:ffff:ffff:ffff:ffff
2542310:fd00::/242310:fdff:ffff:ffff:ffff:ffff:ffff:ffff
2552310:fe00::/242310:feff:ffff:ffff:ffff:ffff:ffff:ffff
2562310:ff00::/242310: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.