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/7
Addresses2^121
/64 networks2^57
Network
2c00::/7
First address
2c00::
Last address
2dff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
2,658,455,991,569,831,745,807,614,120,560,689,152 (2^121)
/64 networks (LANs)
144,115,188,075,855,872 (2^57)
Full form
2c00:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zones
c.2.ip6.arpa
d.2.ip6.arpa
/7 is not on a 4-bit boundary, so it takes 2 /8 zones.
Split into smaller subnets/20
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/16 (512)/20 (8,192)

2c00::/7 makes 8,192 subnets of /20; the first 256 are listed.

Subnets
#SubnetLast address
12c00::/202c00:fff:ffff:ffff:ffff:ffff:ffff:ffff
22c00:1000::/202c00:1fff:ffff:ffff:ffff:ffff:ffff:ffff
32c00:2000::/202c00:2fff:ffff:ffff:ffff:ffff:ffff:ffff
42c00:3000::/202c00:3fff:ffff:ffff:ffff:ffff:ffff:ffff
52c00:4000::/202c00:4fff:ffff:ffff:ffff:ffff:ffff:ffff
62c00:5000::/202c00:5fff:ffff:ffff:ffff:ffff:ffff:ffff
72c00:6000::/202c00:6fff:ffff:ffff:ffff:ffff:ffff:ffff
82c00:7000::/202c00:7fff:ffff:ffff:ffff:ffff:ffff:ffff
92c00:8000::/202c00:8fff:ffff:ffff:ffff:ffff:ffff:ffff
102c00:9000::/202c00:9fff:ffff:ffff:ffff:ffff:ffff:ffff
112c00:a000::/202c00:afff:ffff:ffff:ffff:ffff:ffff:ffff
122c00:b000::/202c00:bfff:ffff:ffff:ffff:ffff:ffff:ffff
132c00:c000::/202c00:cfff:ffff:ffff:ffff:ffff:ffff:ffff
142c00:d000::/202c00:dfff:ffff:ffff:ffff:ffff:ffff:ffff
152c00:e000::/202c00:efff:ffff:ffff:ffff:ffff:ffff:ffff
162c00:f000::/202c00:ffff:ffff:ffff:ffff:ffff:ffff:ffff
172c01::/202c01:fff:ffff:ffff:ffff:ffff:ffff:ffff
182c01:1000::/202c01:1fff:ffff:ffff:ffff:ffff:ffff:ffff
192c01:2000::/202c01:2fff:ffff:ffff:ffff:ffff:ffff:ffff
202c01:3000::/202c01:3fff:ffff:ffff:ffff:ffff:ffff:ffff
212c01:4000::/202c01:4fff:ffff:ffff:ffff:ffff:ffff:ffff
222c01:5000::/202c01:5fff:ffff:ffff:ffff:ffff:ffff:ffff
232c01:6000::/202c01:6fff:ffff:ffff:ffff:ffff:ffff:ffff
242c01:7000::/202c01:7fff:ffff:ffff:ffff:ffff:ffff:ffff
252c01:8000::/202c01:8fff:ffff:ffff:ffff:ffff:ffff:ffff
262c01:9000::/202c01:9fff:ffff:ffff:ffff:ffff:ffff:ffff
272c01:a000::/202c01:afff:ffff:ffff:ffff:ffff:ffff:ffff
282c01:b000::/202c01:bfff:ffff:ffff:ffff:ffff:ffff:ffff
292c01:c000::/202c01:cfff:ffff:ffff:ffff:ffff:ffff:ffff
302c01:d000::/202c01:dfff:ffff:ffff:ffff:ffff:ffff:ffff
312c01:e000::/202c01:efff:ffff:ffff:ffff:ffff:ffff:ffff
322c01:f000::/202c01:ffff:ffff:ffff:ffff:ffff:ffff:ffff
332c02::/202c02:fff:ffff:ffff:ffff:ffff:ffff:ffff
342c02:1000::/202c02:1fff:ffff:ffff:ffff:ffff:ffff:ffff
352c02:2000::/202c02:2fff:ffff:ffff:ffff:ffff:ffff:ffff
362c02:3000::/202c02:3fff:ffff:ffff:ffff:ffff:ffff:ffff
372c02:4000::/202c02:4fff:ffff:ffff:ffff:ffff:ffff:ffff
382c02:5000::/202c02:5fff:ffff:ffff:ffff:ffff:ffff:ffff
392c02:6000::/202c02:6fff:ffff:ffff:ffff:ffff:ffff:ffff
402c02:7000::/202c02:7fff:ffff:ffff:ffff:ffff:ffff:ffff
412c02:8000::/202c02:8fff:ffff:ffff:ffff:ffff:ffff:ffff
422c02:9000::/202c02:9fff:ffff:ffff:ffff:ffff:ffff:ffff
432c02:a000::/202c02:afff:ffff:ffff:ffff:ffff:ffff:ffff
442c02:b000::/202c02:bfff:ffff:ffff:ffff:ffff:ffff:ffff
452c02:c000::/202c02:cfff:ffff:ffff:ffff:ffff:ffff:ffff
462c02:d000::/202c02:dfff:ffff:ffff:ffff:ffff:ffff:ffff
472c02:e000::/202c02:efff:ffff:ffff:ffff:ffff:ffff:ffff
482c02:f000::/202c02:ffff:ffff:ffff:ffff:ffff:ffff:ffff
492c03::/202c03:fff:ffff:ffff:ffff:ffff:ffff:ffff
502c03:1000::/202c03:1fff:ffff:ffff:ffff:ffff:ffff:ffff
512c03:2000::/202c03:2fff:ffff:ffff:ffff:ffff:ffff:ffff
522c03:3000::/202c03:3fff:ffff:ffff:ffff:ffff:ffff:ffff
532c03:4000::/202c03:4fff:ffff:ffff:ffff:ffff:ffff:ffff
542c03:5000::/202c03:5fff:ffff:ffff:ffff:ffff:ffff:ffff
552c03:6000::/202c03:6fff:ffff:ffff:ffff:ffff:ffff:ffff
562c03:7000::/202c03:7fff:ffff:ffff:ffff:ffff:ffff:ffff
572c03:8000::/202c03:8fff:ffff:ffff:ffff:ffff:ffff:ffff
582c03:9000::/202c03:9fff:ffff:ffff:ffff:ffff:ffff:ffff
592c03:a000::/202c03:afff:ffff:ffff:ffff:ffff:ffff:ffff
602c03:b000::/202c03:bfff:ffff:ffff:ffff:ffff:ffff:ffff
612c03:c000::/202c03:cfff:ffff:ffff:ffff:ffff:ffff:ffff
622c03:d000::/202c03:dfff:ffff:ffff:ffff:ffff:ffff:ffff
632c03:e000::/202c03:efff:ffff:ffff:ffff:ffff:ffff:ffff
642c03:f000::/202c03:ffff:ffff:ffff:ffff:ffff:ffff:ffff
652c04::/202c04:fff:ffff:ffff:ffff:ffff:ffff:ffff
662c04:1000::/202c04:1fff:ffff:ffff:ffff:ffff:ffff:ffff
672c04:2000::/202c04:2fff:ffff:ffff:ffff:ffff:ffff:ffff
682c04:3000::/202c04:3fff:ffff:ffff:ffff:ffff:ffff:ffff
692c04:4000::/202c04:4fff:ffff:ffff:ffff:ffff:ffff:ffff
702c04:5000::/202c04:5fff:ffff:ffff:ffff:ffff:ffff:ffff
712c04:6000::/202c04:6fff:ffff:ffff:ffff:ffff:ffff:ffff
722c04:7000::/202c04:7fff:ffff:ffff:ffff:ffff:ffff:ffff
732c04:8000::/202c04:8fff:ffff:ffff:ffff:ffff:ffff:ffff
742c04:9000::/202c04:9fff:ffff:ffff:ffff:ffff:ffff:ffff
752c04:a000::/202c04:afff:ffff:ffff:ffff:ffff:ffff:ffff
762c04:b000::/202c04:bfff:ffff:ffff:ffff:ffff:ffff:ffff
772c04:c000::/202c04:cfff:ffff:ffff:ffff:ffff:ffff:ffff
782c04:d000::/202c04:dfff:ffff:ffff:ffff:ffff:ffff:ffff
792c04:e000::/202c04:efff:ffff:ffff:ffff:ffff:ffff:ffff
802c04:f000::/202c04:ffff:ffff:ffff:ffff:ffff:ffff:ffff
812c05::/202c05:fff:ffff:ffff:ffff:ffff:ffff:ffff
822c05:1000::/202c05:1fff:ffff:ffff:ffff:ffff:ffff:ffff
832c05:2000::/202c05:2fff:ffff:ffff:ffff:ffff:ffff:ffff
842c05:3000::/202c05:3fff:ffff:ffff:ffff:ffff:ffff:ffff
852c05:4000::/202c05:4fff:ffff:ffff:ffff:ffff:ffff:ffff
862c05:5000::/202c05:5fff:ffff:ffff:ffff:ffff:ffff:ffff
872c05:6000::/202c05:6fff:ffff:ffff:ffff:ffff:ffff:ffff
882c05:7000::/202c05:7fff:ffff:ffff:ffff:ffff:ffff:ffff
892c05:8000::/202c05:8fff:ffff:ffff:ffff:ffff:ffff:ffff
902c05:9000::/202c05:9fff:ffff:ffff:ffff:ffff:ffff:ffff
912c05:a000::/202c05:afff:ffff:ffff:ffff:ffff:ffff:ffff
922c05:b000::/202c05:bfff:ffff:ffff:ffff:ffff:ffff:ffff
932c05:c000::/202c05:cfff:ffff:ffff:ffff:ffff:ffff:ffff
942c05:d000::/202c05:dfff:ffff:ffff:ffff:ffff:ffff:ffff
952c05:e000::/202c05:efff:ffff:ffff:ffff:ffff:ffff:ffff
962c05:f000::/202c05:ffff:ffff:ffff:ffff:ffff:ffff:ffff
972c06::/202c06:fff:ffff:ffff:ffff:ffff:ffff:ffff
982c06:1000::/202c06:1fff:ffff:ffff:ffff:ffff:ffff:ffff
992c06:2000::/202c06:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1002c06:3000::/202c06:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1012c06:4000::/202c06:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1022c06:5000::/202c06:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1032c06:6000::/202c06:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1042c06:7000::/202c06:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1052c06:8000::/202c06:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1062c06:9000::/202c06:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1072c06:a000::/202c06:afff:ffff:ffff:ffff:ffff:ffff:ffff
1082c06:b000::/202c06:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1092c06:c000::/202c06:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1102c06:d000::/202c06:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1112c06:e000::/202c06:efff:ffff:ffff:ffff:ffff:ffff:ffff
1122c06:f000::/202c06:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1132c07::/202c07:fff:ffff:ffff:ffff:ffff:ffff:ffff
1142c07:1000::/202c07:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1152c07:2000::/202c07:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1162c07:3000::/202c07:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1172c07:4000::/202c07:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1182c07:5000::/202c07:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1192c07:6000::/202c07:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1202c07:7000::/202c07:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1212c07:8000::/202c07:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1222c07:9000::/202c07:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1232c07:a000::/202c07:afff:ffff:ffff:ffff:ffff:ffff:ffff
1242c07:b000::/202c07:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1252c07:c000::/202c07:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1262c07:d000::/202c07:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1272c07:e000::/202c07:efff:ffff:ffff:ffff:ffff:ffff:ffff
1282c07:f000::/202c07:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1292c08::/202c08:fff:ffff:ffff:ffff:ffff:ffff:ffff
1302c08:1000::/202c08:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1312c08:2000::/202c08:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1322c08:3000::/202c08:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1332c08:4000::/202c08:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1342c08:5000::/202c08:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1352c08:6000::/202c08:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1362c08:7000::/202c08:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1372c08:8000::/202c08:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1382c08:9000::/202c08:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1392c08:a000::/202c08:afff:ffff:ffff:ffff:ffff:ffff:ffff
1402c08:b000::/202c08:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1412c08:c000::/202c08:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1422c08:d000::/202c08:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1432c08:e000::/202c08:efff:ffff:ffff:ffff:ffff:ffff:ffff
1442c08:f000::/202c08:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1452c09::/202c09:fff:ffff:ffff:ffff:ffff:ffff:ffff
1462c09:1000::/202c09:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1472c09:2000::/202c09:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1482c09:3000::/202c09:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1492c09:4000::/202c09:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1502c09:5000::/202c09:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1512c09:6000::/202c09:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1522c09:7000::/202c09:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1532c09:8000::/202c09:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1542c09:9000::/202c09:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1552c09:a000::/202c09:afff:ffff:ffff:ffff:ffff:ffff:ffff
1562c09:b000::/202c09:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1572c09:c000::/202c09:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1582c09:d000::/202c09:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1592c09:e000::/202c09:efff:ffff:ffff:ffff:ffff:ffff:ffff
1602c09:f000::/202c09:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1612c0a::/202c0a:fff:ffff:ffff:ffff:ffff:ffff:ffff
1622c0a:1000::/202c0a:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1632c0a:2000::/202c0a:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1642c0a:3000::/202c0a:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1652c0a:4000::/202c0a:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1662c0a:5000::/202c0a:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1672c0a:6000::/202c0a:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1682c0a:7000::/202c0a:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1692c0a:8000::/202c0a:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1702c0a:9000::/202c0a:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1712c0a:a000::/202c0a:afff:ffff:ffff:ffff:ffff:ffff:ffff
1722c0a:b000::/202c0a:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1732c0a:c000::/202c0a:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1742c0a:d000::/202c0a:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1752c0a:e000::/202c0a:efff:ffff:ffff:ffff:ffff:ffff:ffff
1762c0a:f000::/202c0a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1772c0b::/202c0b:fff:ffff:ffff:ffff:ffff:ffff:ffff
1782c0b:1000::/202c0b:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1792c0b:2000::/202c0b:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1802c0b:3000::/202c0b:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1812c0b:4000::/202c0b:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1822c0b:5000::/202c0b:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1832c0b:6000::/202c0b:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1842c0b:7000::/202c0b:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1852c0b:8000::/202c0b:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1862c0b:9000::/202c0b:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1872c0b:a000::/202c0b:afff:ffff:ffff:ffff:ffff:ffff:ffff
1882c0b:b000::/202c0b:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1892c0b:c000::/202c0b:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1902c0b:d000::/202c0b:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1912c0b:e000::/202c0b:efff:ffff:ffff:ffff:ffff:ffff:ffff
1922c0b:f000::/202c0b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1932c0c::/202c0c:fff:ffff:ffff:ffff:ffff:ffff:ffff
1942c0c:1000::/202c0c:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1952c0c:2000::/202c0c:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1962c0c:3000::/202c0c:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1972c0c:4000::/202c0c:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1982c0c:5000::/202c0c:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1992c0c:6000::/202c0c:6fff:ffff:ffff:ffff:ffff:ffff:ffff
2002c0c:7000::/202c0c:7fff:ffff:ffff:ffff:ffff:ffff:ffff
2012c0c:8000::/202c0c:8fff:ffff:ffff:ffff:ffff:ffff:ffff
2022c0c:9000::/202c0c:9fff:ffff:ffff:ffff:ffff:ffff:ffff
2032c0c:a000::/202c0c:afff:ffff:ffff:ffff:ffff:ffff:ffff
2042c0c:b000::/202c0c:bfff:ffff:ffff:ffff:ffff:ffff:ffff
2052c0c:c000::/202c0c:cfff:ffff:ffff:ffff:ffff:ffff:ffff
2062c0c:d000::/202c0c:dfff:ffff:ffff:ffff:ffff:ffff:ffff
2072c0c:e000::/202c0c:efff:ffff:ffff:ffff:ffff:ffff:ffff
2082c0c:f000::/202c0c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2092c0d::/202c0d:fff:ffff:ffff:ffff:ffff:ffff:ffff
2102c0d:1000::/202c0d:1fff:ffff:ffff:ffff:ffff:ffff:ffff
2112c0d:2000::/202c0d:2fff:ffff:ffff:ffff:ffff:ffff:ffff
2122c0d:3000::/202c0d:3fff:ffff:ffff:ffff:ffff:ffff:ffff
2132c0d:4000::/202c0d:4fff:ffff:ffff:ffff:ffff:ffff:ffff
2142c0d:5000::/202c0d:5fff:ffff:ffff:ffff:ffff:ffff:ffff
2152c0d:6000::/202c0d:6fff:ffff:ffff:ffff:ffff:ffff:ffff
2162c0d:7000::/202c0d:7fff:ffff:ffff:ffff:ffff:ffff:ffff
2172c0d:8000::/202c0d:8fff:ffff:ffff:ffff:ffff:ffff:ffff
2182c0d:9000::/202c0d:9fff:ffff:ffff:ffff:ffff:ffff:ffff
2192c0d:a000::/202c0d:afff:ffff:ffff:ffff:ffff:ffff:ffff
2202c0d:b000::/202c0d:bfff:ffff:ffff:ffff:ffff:ffff:ffff
2212c0d:c000::/202c0d:cfff:ffff:ffff:ffff:ffff:ffff:ffff
2222c0d:d000::/202c0d:dfff:ffff:ffff:ffff:ffff:ffff:ffff
2232c0d:e000::/202c0d:efff:ffff:ffff:ffff:ffff:ffff:ffff
2242c0d:f000::/202c0d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2252c0e::/202c0e:fff:ffff:ffff:ffff:ffff:ffff:ffff
2262c0e:1000::/202c0e:1fff:ffff:ffff:ffff:ffff:ffff:ffff
2272c0e:2000::/202c0e:2fff:ffff:ffff:ffff:ffff:ffff:ffff
2282c0e:3000::/202c0e:3fff:ffff:ffff:ffff:ffff:ffff:ffff
2292c0e:4000::/202c0e:4fff:ffff:ffff:ffff:ffff:ffff:ffff
2302c0e:5000::/202c0e:5fff:ffff:ffff:ffff:ffff:ffff:ffff
2312c0e:6000::/202c0e:6fff:ffff:ffff:ffff:ffff:ffff:ffff
2322c0e:7000::/202c0e:7fff:ffff:ffff:ffff:ffff:ffff:ffff
2332c0e:8000::/202c0e:8fff:ffff:ffff:ffff:ffff:ffff:ffff
2342c0e:9000::/202c0e:9fff:ffff:ffff:ffff:ffff:ffff:ffff
2352c0e:a000::/202c0e:afff:ffff:ffff:ffff:ffff:ffff:ffff
2362c0e:b000::/202c0e:bfff:ffff:ffff:ffff:ffff:ffff:ffff
2372c0e:c000::/202c0e:cfff:ffff:ffff:ffff:ffff:ffff:ffff
2382c0e:d000::/202c0e:dfff:ffff:ffff:ffff:ffff:ffff:ffff
2392c0e:e000::/202c0e:efff:ffff:ffff:ffff:ffff:ffff:ffff
2402c0e:f000::/202c0e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2412c0f::/202c0f:fff:ffff:ffff:ffff:ffff:ffff:ffff
2422c0f:1000::/202c0f:1fff:ffff:ffff:ffff:ffff:ffff:ffff
2432c0f:2000::/202c0f:2fff:ffff:ffff:ffff:ffff:ffff:ffff
2442c0f:3000::/202c0f:3fff:ffff:ffff:ffff:ffff:ffff:ffff
2452c0f:4000::/202c0f:4fff:ffff:ffff:ffff:ffff:ffff:ffff
2462c0f:5000::/202c0f:5fff:ffff:ffff:ffff:ffff:ffff:ffff
2472c0f:6000::/202c0f:6fff:ffff:ffff:ffff:ffff:ffff:ffff
2482c0f:7000::/202c0f:7fff:ffff:ffff:ffff:ffff:ffff:ffff
2492c0f:8000::/202c0f:8fff:ffff:ffff:ffff:ffff:ffff:ffff
2502c0f:9000::/202c0f:9fff:ffff:ffff:ffff:ffff:ffff:ffff
2512c0f:a000::/202c0f:afff:ffff:ffff:ffff:ffff:ffff:ffff
2522c0f:b000::/202c0f:bfff:ffff:ffff:ffff:ffff:ffff:ffff
2532c0f:c000::/202c0f:cfff:ffff:ffff:ffff:ffff:ffff:ffff
2542c0f:d000::/202c0f:dfff:ffff:ffff:ffff:ffff:ffff:ffff
2552c0f:e000::/202c0f:efff:ffff:ffff:ffff:ffff:ffff:ffff
2562c0f:f000::/202c0f: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.