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
2740::/12
First address
2740::
Last address
274f: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
2740:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
4.7.2.ip6.arpa
Split into smaller subnets/24
/13 (2)/14 (4)/15 (8)/16 (16)/20 (256)/24 (4,096)/28 (65,536)

2740::/12 makes 4,096 subnets of /24; the first 256 are listed.

Subnets
#SubnetLast address
12740::/242740:ff:ffff:ffff:ffff:ffff:ffff:ffff
22740:100::/242740:1ff:ffff:ffff:ffff:ffff:ffff:ffff
32740:200::/242740:2ff:ffff:ffff:ffff:ffff:ffff:ffff
42740:300::/242740:3ff:ffff:ffff:ffff:ffff:ffff:ffff
52740:400::/242740:4ff:ffff:ffff:ffff:ffff:ffff:ffff
62740:500::/242740:5ff:ffff:ffff:ffff:ffff:ffff:ffff
72740:600::/242740:6ff:ffff:ffff:ffff:ffff:ffff:ffff
82740:700::/242740:7ff:ffff:ffff:ffff:ffff:ffff:ffff
92740:800::/242740:8ff:ffff:ffff:ffff:ffff:ffff:ffff
102740:900::/242740:9ff:ffff:ffff:ffff:ffff:ffff:ffff
112740:a00::/242740:aff:ffff:ffff:ffff:ffff:ffff:ffff
122740:b00::/242740:bff:ffff:ffff:ffff:ffff:ffff:ffff
132740:c00::/242740:cff:ffff:ffff:ffff:ffff:ffff:ffff
142740:d00::/242740:dff:ffff:ffff:ffff:ffff:ffff:ffff
152740:e00::/242740:eff:ffff:ffff:ffff:ffff:ffff:ffff
162740:f00::/242740:fff:ffff:ffff:ffff:ffff:ffff:ffff
172740:1000::/242740:10ff:ffff:ffff:ffff:ffff:ffff:ffff
182740:1100::/242740:11ff:ffff:ffff:ffff:ffff:ffff:ffff
192740:1200::/242740:12ff:ffff:ffff:ffff:ffff:ffff:ffff
202740:1300::/242740:13ff:ffff:ffff:ffff:ffff:ffff:ffff
212740:1400::/242740:14ff:ffff:ffff:ffff:ffff:ffff:ffff
222740:1500::/242740:15ff:ffff:ffff:ffff:ffff:ffff:ffff
232740:1600::/242740:16ff:ffff:ffff:ffff:ffff:ffff:ffff
242740:1700::/242740:17ff:ffff:ffff:ffff:ffff:ffff:ffff
252740:1800::/242740:18ff:ffff:ffff:ffff:ffff:ffff:ffff
262740:1900::/242740:19ff:ffff:ffff:ffff:ffff:ffff:ffff
272740:1a00::/242740:1aff:ffff:ffff:ffff:ffff:ffff:ffff
282740:1b00::/242740:1bff:ffff:ffff:ffff:ffff:ffff:ffff
292740:1c00::/242740:1cff:ffff:ffff:ffff:ffff:ffff:ffff
302740:1d00::/242740:1dff:ffff:ffff:ffff:ffff:ffff:ffff
312740:1e00::/242740:1eff:ffff:ffff:ffff:ffff:ffff:ffff
322740:1f00::/242740:1fff:ffff:ffff:ffff:ffff:ffff:ffff
332740:2000::/242740:20ff:ffff:ffff:ffff:ffff:ffff:ffff
342740:2100::/242740:21ff:ffff:ffff:ffff:ffff:ffff:ffff
352740:2200::/242740:22ff:ffff:ffff:ffff:ffff:ffff:ffff
362740:2300::/242740:23ff:ffff:ffff:ffff:ffff:ffff:ffff
372740:2400::/242740:24ff:ffff:ffff:ffff:ffff:ffff:ffff
382740:2500::/242740:25ff:ffff:ffff:ffff:ffff:ffff:ffff
392740:2600::/242740:26ff:ffff:ffff:ffff:ffff:ffff:ffff
402740:2700::/242740:27ff:ffff:ffff:ffff:ffff:ffff:ffff
412740:2800::/242740:28ff:ffff:ffff:ffff:ffff:ffff:ffff
422740:2900::/242740:29ff:ffff:ffff:ffff:ffff:ffff:ffff
432740:2a00::/242740:2aff:ffff:ffff:ffff:ffff:ffff:ffff
442740:2b00::/242740:2bff:ffff:ffff:ffff:ffff:ffff:ffff
452740:2c00::/242740:2cff:ffff:ffff:ffff:ffff:ffff:ffff
462740:2d00::/242740:2dff:ffff:ffff:ffff:ffff:ffff:ffff
472740:2e00::/242740:2eff:ffff:ffff:ffff:ffff:ffff:ffff
482740:2f00::/242740:2fff:ffff:ffff:ffff:ffff:ffff:ffff
492740:3000::/242740:30ff:ffff:ffff:ffff:ffff:ffff:ffff
502740:3100::/242740:31ff:ffff:ffff:ffff:ffff:ffff:ffff
512740:3200::/242740:32ff:ffff:ffff:ffff:ffff:ffff:ffff
522740:3300::/242740:33ff:ffff:ffff:ffff:ffff:ffff:ffff
532740:3400::/242740:34ff:ffff:ffff:ffff:ffff:ffff:ffff
542740:3500::/242740:35ff:ffff:ffff:ffff:ffff:ffff:ffff
552740:3600::/242740:36ff:ffff:ffff:ffff:ffff:ffff:ffff
562740:3700::/242740:37ff:ffff:ffff:ffff:ffff:ffff:ffff
572740:3800::/242740:38ff:ffff:ffff:ffff:ffff:ffff:ffff
582740:3900::/242740:39ff:ffff:ffff:ffff:ffff:ffff:ffff
592740:3a00::/242740:3aff:ffff:ffff:ffff:ffff:ffff:ffff
602740:3b00::/242740:3bff:ffff:ffff:ffff:ffff:ffff:ffff
612740:3c00::/242740:3cff:ffff:ffff:ffff:ffff:ffff:ffff
622740:3d00::/242740:3dff:ffff:ffff:ffff:ffff:ffff:ffff
632740:3e00::/242740:3eff:ffff:ffff:ffff:ffff:ffff:ffff
642740:3f00::/242740:3fff:ffff:ffff:ffff:ffff:ffff:ffff
652740:4000::/242740:40ff:ffff:ffff:ffff:ffff:ffff:ffff
662740:4100::/242740:41ff:ffff:ffff:ffff:ffff:ffff:ffff
672740:4200::/242740:42ff:ffff:ffff:ffff:ffff:ffff:ffff
682740:4300::/242740:43ff:ffff:ffff:ffff:ffff:ffff:ffff
692740:4400::/242740:44ff:ffff:ffff:ffff:ffff:ffff:ffff
702740:4500::/242740:45ff:ffff:ffff:ffff:ffff:ffff:ffff
712740:4600::/242740:46ff:ffff:ffff:ffff:ffff:ffff:ffff
722740:4700::/242740:47ff:ffff:ffff:ffff:ffff:ffff:ffff
732740:4800::/242740:48ff:ffff:ffff:ffff:ffff:ffff:ffff
742740:4900::/242740:49ff:ffff:ffff:ffff:ffff:ffff:ffff
752740:4a00::/242740:4aff:ffff:ffff:ffff:ffff:ffff:ffff
762740:4b00::/242740:4bff:ffff:ffff:ffff:ffff:ffff:ffff
772740:4c00::/242740:4cff:ffff:ffff:ffff:ffff:ffff:ffff
782740:4d00::/242740:4dff:ffff:ffff:ffff:ffff:ffff:ffff
792740:4e00::/242740:4eff:ffff:ffff:ffff:ffff:ffff:ffff
802740:4f00::/242740:4fff:ffff:ffff:ffff:ffff:ffff:ffff
812740:5000::/242740:50ff:ffff:ffff:ffff:ffff:ffff:ffff
822740:5100::/242740:51ff:ffff:ffff:ffff:ffff:ffff:ffff
832740:5200::/242740:52ff:ffff:ffff:ffff:ffff:ffff:ffff
842740:5300::/242740:53ff:ffff:ffff:ffff:ffff:ffff:ffff
852740:5400::/242740:54ff:ffff:ffff:ffff:ffff:ffff:ffff
862740:5500::/242740:55ff:ffff:ffff:ffff:ffff:ffff:ffff
872740:5600::/242740:56ff:ffff:ffff:ffff:ffff:ffff:ffff
882740:5700::/242740:57ff:ffff:ffff:ffff:ffff:ffff:ffff
892740:5800::/242740:58ff:ffff:ffff:ffff:ffff:ffff:ffff
902740:5900::/242740:59ff:ffff:ffff:ffff:ffff:ffff:ffff
912740:5a00::/242740:5aff:ffff:ffff:ffff:ffff:ffff:ffff
922740:5b00::/242740:5bff:ffff:ffff:ffff:ffff:ffff:ffff
932740:5c00::/242740:5cff:ffff:ffff:ffff:ffff:ffff:ffff
942740:5d00::/242740:5dff:ffff:ffff:ffff:ffff:ffff:ffff
952740:5e00::/242740:5eff:ffff:ffff:ffff:ffff:ffff:ffff
962740:5f00::/242740:5fff:ffff:ffff:ffff:ffff:ffff:ffff
972740:6000::/242740:60ff:ffff:ffff:ffff:ffff:ffff:ffff
982740:6100::/242740:61ff:ffff:ffff:ffff:ffff:ffff:ffff
992740:6200::/242740:62ff:ffff:ffff:ffff:ffff:ffff:ffff
1002740:6300::/242740:63ff:ffff:ffff:ffff:ffff:ffff:ffff
1012740:6400::/242740:64ff:ffff:ffff:ffff:ffff:ffff:ffff
1022740:6500::/242740:65ff:ffff:ffff:ffff:ffff:ffff:ffff
1032740:6600::/242740:66ff:ffff:ffff:ffff:ffff:ffff:ffff
1042740:6700::/242740:67ff:ffff:ffff:ffff:ffff:ffff:ffff
1052740:6800::/242740:68ff:ffff:ffff:ffff:ffff:ffff:ffff
1062740:6900::/242740:69ff:ffff:ffff:ffff:ffff:ffff:ffff
1072740:6a00::/242740:6aff:ffff:ffff:ffff:ffff:ffff:ffff
1082740:6b00::/242740:6bff:ffff:ffff:ffff:ffff:ffff:ffff
1092740:6c00::/242740:6cff:ffff:ffff:ffff:ffff:ffff:ffff
1102740:6d00::/242740:6dff:ffff:ffff:ffff:ffff:ffff:ffff
1112740:6e00::/242740:6eff:ffff:ffff:ffff:ffff:ffff:ffff
1122740:6f00::/242740:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1132740:7000::/242740:70ff:ffff:ffff:ffff:ffff:ffff:ffff
1142740:7100::/242740:71ff:ffff:ffff:ffff:ffff:ffff:ffff
1152740:7200::/242740:72ff:ffff:ffff:ffff:ffff:ffff:ffff
1162740:7300::/242740:73ff:ffff:ffff:ffff:ffff:ffff:ffff
1172740:7400::/242740:74ff:ffff:ffff:ffff:ffff:ffff:ffff
1182740:7500::/242740:75ff:ffff:ffff:ffff:ffff:ffff:ffff
1192740:7600::/242740:76ff:ffff:ffff:ffff:ffff:ffff:ffff
1202740:7700::/242740:77ff:ffff:ffff:ffff:ffff:ffff:ffff
1212740:7800::/242740:78ff:ffff:ffff:ffff:ffff:ffff:ffff
1222740:7900::/242740:79ff:ffff:ffff:ffff:ffff:ffff:ffff
1232740:7a00::/242740:7aff:ffff:ffff:ffff:ffff:ffff:ffff
1242740:7b00::/242740:7bff:ffff:ffff:ffff:ffff:ffff:ffff
1252740:7c00::/242740:7cff:ffff:ffff:ffff:ffff:ffff:ffff
1262740:7d00::/242740:7dff:ffff:ffff:ffff:ffff:ffff:ffff
1272740:7e00::/242740:7eff:ffff:ffff:ffff:ffff:ffff:ffff
1282740:7f00::/242740:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1292740:8000::/242740:80ff:ffff:ffff:ffff:ffff:ffff:ffff
1302740:8100::/242740:81ff:ffff:ffff:ffff:ffff:ffff:ffff
1312740:8200::/242740:82ff:ffff:ffff:ffff:ffff:ffff:ffff
1322740:8300::/242740:83ff:ffff:ffff:ffff:ffff:ffff:ffff
1332740:8400::/242740:84ff:ffff:ffff:ffff:ffff:ffff:ffff
1342740:8500::/242740:85ff:ffff:ffff:ffff:ffff:ffff:ffff
1352740:8600::/242740:86ff:ffff:ffff:ffff:ffff:ffff:ffff
1362740:8700::/242740:87ff:ffff:ffff:ffff:ffff:ffff:ffff
1372740:8800::/242740:88ff:ffff:ffff:ffff:ffff:ffff:ffff
1382740:8900::/242740:89ff:ffff:ffff:ffff:ffff:ffff:ffff
1392740:8a00::/242740:8aff:ffff:ffff:ffff:ffff:ffff:ffff
1402740:8b00::/242740:8bff:ffff:ffff:ffff:ffff:ffff:ffff
1412740:8c00::/242740:8cff:ffff:ffff:ffff:ffff:ffff:ffff
1422740:8d00::/242740:8dff:ffff:ffff:ffff:ffff:ffff:ffff
1432740:8e00::/242740:8eff:ffff:ffff:ffff:ffff:ffff:ffff
1442740:8f00::/242740:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1452740:9000::/242740:90ff:ffff:ffff:ffff:ffff:ffff:ffff
1462740:9100::/242740:91ff:ffff:ffff:ffff:ffff:ffff:ffff
1472740:9200::/242740:92ff:ffff:ffff:ffff:ffff:ffff:ffff
1482740:9300::/242740:93ff:ffff:ffff:ffff:ffff:ffff:ffff
1492740:9400::/242740:94ff:ffff:ffff:ffff:ffff:ffff:ffff
1502740:9500::/242740:95ff:ffff:ffff:ffff:ffff:ffff:ffff
1512740:9600::/242740:96ff:ffff:ffff:ffff:ffff:ffff:ffff
1522740:9700::/242740:97ff:ffff:ffff:ffff:ffff:ffff:ffff
1532740:9800::/242740:98ff:ffff:ffff:ffff:ffff:ffff:ffff
1542740:9900::/242740:99ff:ffff:ffff:ffff:ffff:ffff:ffff
1552740:9a00::/242740:9aff:ffff:ffff:ffff:ffff:ffff:ffff
1562740:9b00::/242740:9bff:ffff:ffff:ffff:ffff:ffff:ffff
1572740:9c00::/242740:9cff:ffff:ffff:ffff:ffff:ffff:ffff
1582740:9d00::/242740:9dff:ffff:ffff:ffff:ffff:ffff:ffff
1592740:9e00::/242740:9eff:ffff:ffff:ffff:ffff:ffff:ffff
1602740:9f00::/242740:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1612740:a000::/242740:a0ff:ffff:ffff:ffff:ffff:ffff:ffff
1622740:a100::/242740:a1ff:ffff:ffff:ffff:ffff:ffff:ffff
1632740:a200::/242740:a2ff:ffff:ffff:ffff:ffff:ffff:ffff
1642740:a300::/242740:a3ff:ffff:ffff:ffff:ffff:ffff:ffff
1652740:a400::/242740:a4ff:ffff:ffff:ffff:ffff:ffff:ffff
1662740:a500::/242740:a5ff:ffff:ffff:ffff:ffff:ffff:ffff
1672740:a600::/242740:a6ff:ffff:ffff:ffff:ffff:ffff:ffff
1682740:a700::/242740:a7ff:ffff:ffff:ffff:ffff:ffff:ffff
1692740:a800::/242740:a8ff:ffff:ffff:ffff:ffff:ffff:ffff
1702740:a900::/242740:a9ff:ffff:ffff:ffff:ffff:ffff:ffff
1712740:aa00::/242740:aaff:ffff:ffff:ffff:ffff:ffff:ffff
1722740:ab00::/242740:abff:ffff:ffff:ffff:ffff:ffff:ffff
1732740:ac00::/242740:acff:ffff:ffff:ffff:ffff:ffff:ffff
1742740:ad00::/242740:adff:ffff:ffff:ffff:ffff:ffff:ffff
1752740:ae00::/242740:aeff:ffff:ffff:ffff:ffff:ffff:ffff
1762740:af00::/242740:afff:ffff:ffff:ffff:ffff:ffff:ffff
1772740:b000::/242740:b0ff:ffff:ffff:ffff:ffff:ffff:ffff
1782740:b100::/242740:b1ff:ffff:ffff:ffff:ffff:ffff:ffff
1792740:b200::/242740:b2ff:ffff:ffff:ffff:ffff:ffff:ffff
1802740:b300::/242740:b3ff:ffff:ffff:ffff:ffff:ffff:ffff
1812740:b400::/242740:b4ff:ffff:ffff:ffff:ffff:ffff:ffff
1822740:b500::/242740:b5ff:ffff:ffff:ffff:ffff:ffff:ffff
1832740:b600::/242740:b6ff:ffff:ffff:ffff:ffff:ffff:ffff
1842740:b700::/242740:b7ff:ffff:ffff:ffff:ffff:ffff:ffff
1852740:b800::/242740:b8ff:ffff:ffff:ffff:ffff:ffff:ffff
1862740:b900::/242740:b9ff:ffff:ffff:ffff:ffff:ffff:ffff
1872740:ba00::/242740:baff:ffff:ffff:ffff:ffff:ffff:ffff
1882740:bb00::/242740:bbff:ffff:ffff:ffff:ffff:ffff:ffff
1892740:bc00::/242740:bcff:ffff:ffff:ffff:ffff:ffff:ffff
1902740:bd00::/242740:bdff:ffff:ffff:ffff:ffff:ffff:ffff
1912740:be00::/242740:beff:ffff:ffff:ffff:ffff:ffff:ffff
1922740:bf00::/242740:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1932740:c000::/242740:c0ff:ffff:ffff:ffff:ffff:ffff:ffff
1942740:c100::/242740:c1ff:ffff:ffff:ffff:ffff:ffff:ffff
1952740:c200::/242740:c2ff:ffff:ffff:ffff:ffff:ffff:ffff
1962740:c300::/242740:c3ff:ffff:ffff:ffff:ffff:ffff:ffff
1972740:c400::/242740:c4ff:ffff:ffff:ffff:ffff:ffff:ffff
1982740:c500::/242740:c5ff:ffff:ffff:ffff:ffff:ffff:ffff
1992740:c600::/242740:c6ff:ffff:ffff:ffff:ffff:ffff:ffff
2002740:c700::/242740:c7ff:ffff:ffff:ffff:ffff:ffff:ffff
2012740:c800::/242740:c8ff:ffff:ffff:ffff:ffff:ffff:ffff
2022740:c900::/242740:c9ff:ffff:ffff:ffff:ffff:ffff:ffff
2032740:ca00::/242740:caff:ffff:ffff:ffff:ffff:ffff:ffff
2042740:cb00::/242740:cbff:ffff:ffff:ffff:ffff:ffff:ffff
2052740:cc00::/242740:ccff:ffff:ffff:ffff:ffff:ffff:ffff
2062740:cd00::/242740:cdff:ffff:ffff:ffff:ffff:ffff:ffff
2072740:ce00::/242740:ceff:ffff:ffff:ffff:ffff:ffff:ffff
2082740:cf00::/242740:cfff:ffff:ffff:ffff:ffff:ffff:ffff
2092740:d000::/242740:d0ff:ffff:ffff:ffff:ffff:ffff:ffff
2102740:d100::/242740:d1ff:ffff:ffff:ffff:ffff:ffff:ffff
2112740:d200::/242740:d2ff:ffff:ffff:ffff:ffff:ffff:ffff
2122740:d300::/242740:d3ff:ffff:ffff:ffff:ffff:ffff:ffff
2132740:d400::/242740:d4ff:ffff:ffff:ffff:ffff:ffff:ffff
2142740:d500::/242740:d5ff:ffff:ffff:ffff:ffff:ffff:ffff
2152740:d600::/242740:d6ff:ffff:ffff:ffff:ffff:ffff:ffff
2162740:d700::/242740:d7ff:ffff:ffff:ffff:ffff:ffff:ffff
2172740:d800::/242740:d8ff:ffff:ffff:ffff:ffff:ffff:ffff
2182740:d900::/242740:d9ff:ffff:ffff:ffff:ffff:ffff:ffff
2192740:da00::/242740:daff:ffff:ffff:ffff:ffff:ffff:ffff
2202740:db00::/242740:dbff:ffff:ffff:ffff:ffff:ffff:ffff
2212740:dc00::/242740:dcff:ffff:ffff:ffff:ffff:ffff:ffff
2222740:dd00::/242740:ddff:ffff:ffff:ffff:ffff:ffff:ffff
2232740:de00::/242740:deff:ffff:ffff:ffff:ffff:ffff:ffff
2242740:df00::/242740:dfff:ffff:ffff:ffff:ffff:ffff:ffff
2252740:e000::/242740:e0ff:ffff:ffff:ffff:ffff:ffff:ffff
2262740:e100::/242740:e1ff:ffff:ffff:ffff:ffff:ffff:ffff
2272740:e200::/242740:e2ff:ffff:ffff:ffff:ffff:ffff:ffff
2282740:e300::/242740:e3ff:ffff:ffff:ffff:ffff:ffff:ffff
2292740:e400::/242740:e4ff:ffff:ffff:ffff:ffff:ffff:ffff
2302740:e500::/242740:e5ff:ffff:ffff:ffff:ffff:ffff:ffff
2312740:e600::/242740:e6ff:ffff:ffff:ffff:ffff:ffff:ffff
2322740:e700::/242740:e7ff:ffff:ffff:ffff:ffff:ffff:ffff
2332740:e800::/242740:e8ff:ffff:ffff:ffff:ffff:ffff:ffff
2342740:e900::/242740:e9ff:ffff:ffff:ffff:ffff:ffff:ffff
2352740:ea00::/242740:eaff:ffff:ffff:ffff:ffff:ffff:ffff
2362740:eb00::/242740:ebff:ffff:ffff:ffff:ffff:ffff:ffff
2372740:ec00::/242740:ecff:ffff:ffff:ffff:ffff:ffff:ffff
2382740:ed00::/242740:edff:ffff:ffff:ffff:ffff:ffff:ffff
2392740:ee00::/242740:eeff:ffff:ffff:ffff:ffff:ffff:ffff
2402740:ef00::/242740:efff:ffff:ffff:ffff:ffff:ffff:ffff
2412740:f000::/242740:f0ff:ffff:ffff:ffff:ffff:ffff:ffff
2422740:f100::/242740:f1ff:ffff:ffff:ffff:ffff:ffff:ffff
2432740:f200::/242740:f2ff:ffff:ffff:ffff:ffff:ffff:ffff
2442740:f300::/242740:f3ff:ffff:ffff:ffff:ffff:ffff:ffff
2452740:f400::/242740:f4ff:ffff:ffff:ffff:ffff:ffff:ffff
2462740:f500::/242740:f5ff:ffff:ffff:ffff:ffff:ffff:ffff
2472740:f600::/242740:f6ff:ffff:ffff:ffff:ffff:ffff:ffff
2482740:f700::/242740:f7ff:ffff:ffff:ffff:ffff:ffff:ffff
2492740:f800::/242740:f8ff:ffff:ffff:ffff:ffff:ffff:ffff
2502740:f900::/242740:f9ff:ffff:ffff:ffff:ffff:ffff:ffff
2512740:fa00::/242740:faff:ffff:ffff:ffff:ffff:ffff:ffff
2522740:fb00::/242740:fbff:ffff:ffff:ffff:ffff:ffff:ffff
2532740:fc00::/242740:fcff:ffff:ffff:ffff:ffff:ffff:ffff
2542740:fd00::/242740:fdff:ffff:ffff:ffff:ffff:ffff:ffff
2552740:fe00::/242740:feff:ffff:ffff:ffff:ffff:ffff:ffff
2562740:ff00::/242740: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.