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
3c00::/7
First address
3c00::
Last address
3dff: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
3c00:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zones
c.3.ip6.arpa
d.3.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)

3c00::/7 makes 8,192 subnets of /20; the first 256 are listed.

Subnets
#SubnetLast address
13c00::/203c00:fff:ffff:ffff:ffff:ffff:ffff:ffff
23c00:1000::/203c00:1fff:ffff:ffff:ffff:ffff:ffff:ffff
33c00:2000::/203c00:2fff:ffff:ffff:ffff:ffff:ffff:ffff
43c00:3000::/203c00:3fff:ffff:ffff:ffff:ffff:ffff:ffff
53c00:4000::/203c00:4fff:ffff:ffff:ffff:ffff:ffff:ffff
63c00:5000::/203c00:5fff:ffff:ffff:ffff:ffff:ffff:ffff
73c00:6000::/203c00:6fff:ffff:ffff:ffff:ffff:ffff:ffff
83c00:7000::/203c00:7fff:ffff:ffff:ffff:ffff:ffff:ffff
93c00:8000::/203c00:8fff:ffff:ffff:ffff:ffff:ffff:ffff
103c00:9000::/203c00:9fff:ffff:ffff:ffff:ffff:ffff:ffff
113c00:a000::/203c00:afff:ffff:ffff:ffff:ffff:ffff:ffff
123c00:b000::/203c00:bfff:ffff:ffff:ffff:ffff:ffff:ffff
133c00:c000::/203c00:cfff:ffff:ffff:ffff:ffff:ffff:ffff
143c00:d000::/203c00:dfff:ffff:ffff:ffff:ffff:ffff:ffff
153c00:e000::/203c00:efff:ffff:ffff:ffff:ffff:ffff:ffff
163c00:f000::/203c00:ffff:ffff:ffff:ffff:ffff:ffff:ffff
173c01::/203c01:fff:ffff:ffff:ffff:ffff:ffff:ffff
183c01:1000::/203c01:1fff:ffff:ffff:ffff:ffff:ffff:ffff
193c01:2000::/203c01:2fff:ffff:ffff:ffff:ffff:ffff:ffff
203c01:3000::/203c01:3fff:ffff:ffff:ffff:ffff:ffff:ffff
213c01:4000::/203c01:4fff:ffff:ffff:ffff:ffff:ffff:ffff
223c01:5000::/203c01:5fff:ffff:ffff:ffff:ffff:ffff:ffff
233c01:6000::/203c01:6fff:ffff:ffff:ffff:ffff:ffff:ffff
243c01:7000::/203c01:7fff:ffff:ffff:ffff:ffff:ffff:ffff
253c01:8000::/203c01:8fff:ffff:ffff:ffff:ffff:ffff:ffff
263c01:9000::/203c01:9fff:ffff:ffff:ffff:ffff:ffff:ffff
273c01:a000::/203c01:afff:ffff:ffff:ffff:ffff:ffff:ffff
283c01:b000::/203c01:bfff:ffff:ffff:ffff:ffff:ffff:ffff
293c01:c000::/203c01:cfff:ffff:ffff:ffff:ffff:ffff:ffff
303c01:d000::/203c01:dfff:ffff:ffff:ffff:ffff:ffff:ffff
313c01:e000::/203c01:efff:ffff:ffff:ffff:ffff:ffff:ffff
323c01:f000::/203c01:ffff:ffff:ffff:ffff:ffff:ffff:ffff
333c02::/203c02:fff:ffff:ffff:ffff:ffff:ffff:ffff
343c02:1000::/203c02:1fff:ffff:ffff:ffff:ffff:ffff:ffff
353c02:2000::/203c02:2fff:ffff:ffff:ffff:ffff:ffff:ffff
363c02:3000::/203c02:3fff:ffff:ffff:ffff:ffff:ffff:ffff
373c02:4000::/203c02:4fff:ffff:ffff:ffff:ffff:ffff:ffff
383c02:5000::/203c02:5fff:ffff:ffff:ffff:ffff:ffff:ffff
393c02:6000::/203c02:6fff:ffff:ffff:ffff:ffff:ffff:ffff
403c02:7000::/203c02:7fff:ffff:ffff:ffff:ffff:ffff:ffff
413c02:8000::/203c02:8fff:ffff:ffff:ffff:ffff:ffff:ffff
423c02:9000::/203c02:9fff:ffff:ffff:ffff:ffff:ffff:ffff
433c02:a000::/203c02:afff:ffff:ffff:ffff:ffff:ffff:ffff
443c02:b000::/203c02:bfff:ffff:ffff:ffff:ffff:ffff:ffff
453c02:c000::/203c02:cfff:ffff:ffff:ffff:ffff:ffff:ffff
463c02:d000::/203c02:dfff:ffff:ffff:ffff:ffff:ffff:ffff
473c02:e000::/203c02:efff:ffff:ffff:ffff:ffff:ffff:ffff
483c02:f000::/203c02:ffff:ffff:ffff:ffff:ffff:ffff:ffff
493c03::/203c03:fff:ffff:ffff:ffff:ffff:ffff:ffff
503c03:1000::/203c03:1fff:ffff:ffff:ffff:ffff:ffff:ffff
513c03:2000::/203c03:2fff:ffff:ffff:ffff:ffff:ffff:ffff
523c03:3000::/203c03:3fff:ffff:ffff:ffff:ffff:ffff:ffff
533c03:4000::/203c03:4fff:ffff:ffff:ffff:ffff:ffff:ffff
543c03:5000::/203c03:5fff:ffff:ffff:ffff:ffff:ffff:ffff
553c03:6000::/203c03:6fff:ffff:ffff:ffff:ffff:ffff:ffff
563c03:7000::/203c03:7fff:ffff:ffff:ffff:ffff:ffff:ffff
573c03:8000::/203c03:8fff:ffff:ffff:ffff:ffff:ffff:ffff
583c03:9000::/203c03:9fff:ffff:ffff:ffff:ffff:ffff:ffff
593c03:a000::/203c03:afff:ffff:ffff:ffff:ffff:ffff:ffff
603c03:b000::/203c03:bfff:ffff:ffff:ffff:ffff:ffff:ffff
613c03:c000::/203c03:cfff:ffff:ffff:ffff:ffff:ffff:ffff
623c03:d000::/203c03:dfff:ffff:ffff:ffff:ffff:ffff:ffff
633c03:e000::/203c03:efff:ffff:ffff:ffff:ffff:ffff:ffff
643c03:f000::/203c03:ffff:ffff:ffff:ffff:ffff:ffff:ffff
653c04::/203c04:fff:ffff:ffff:ffff:ffff:ffff:ffff
663c04:1000::/203c04:1fff:ffff:ffff:ffff:ffff:ffff:ffff
673c04:2000::/203c04:2fff:ffff:ffff:ffff:ffff:ffff:ffff
683c04:3000::/203c04:3fff:ffff:ffff:ffff:ffff:ffff:ffff
693c04:4000::/203c04:4fff:ffff:ffff:ffff:ffff:ffff:ffff
703c04:5000::/203c04:5fff:ffff:ffff:ffff:ffff:ffff:ffff
713c04:6000::/203c04:6fff:ffff:ffff:ffff:ffff:ffff:ffff
723c04:7000::/203c04:7fff:ffff:ffff:ffff:ffff:ffff:ffff
733c04:8000::/203c04:8fff:ffff:ffff:ffff:ffff:ffff:ffff
743c04:9000::/203c04:9fff:ffff:ffff:ffff:ffff:ffff:ffff
753c04:a000::/203c04:afff:ffff:ffff:ffff:ffff:ffff:ffff
763c04:b000::/203c04:bfff:ffff:ffff:ffff:ffff:ffff:ffff
773c04:c000::/203c04:cfff:ffff:ffff:ffff:ffff:ffff:ffff
783c04:d000::/203c04:dfff:ffff:ffff:ffff:ffff:ffff:ffff
793c04:e000::/203c04:efff:ffff:ffff:ffff:ffff:ffff:ffff
803c04:f000::/203c04:ffff:ffff:ffff:ffff:ffff:ffff:ffff
813c05::/203c05:fff:ffff:ffff:ffff:ffff:ffff:ffff
823c05:1000::/203c05:1fff:ffff:ffff:ffff:ffff:ffff:ffff
833c05:2000::/203c05:2fff:ffff:ffff:ffff:ffff:ffff:ffff
843c05:3000::/203c05:3fff:ffff:ffff:ffff:ffff:ffff:ffff
853c05:4000::/203c05:4fff:ffff:ffff:ffff:ffff:ffff:ffff
863c05:5000::/203c05:5fff:ffff:ffff:ffff:ffff:ffff:ffff
873c05:6000::/203c05:6fff:ffff:ffff:ffff:ffff:ffff:ffff
883c05:7000::/203c05:7fff:ffff:ffff:ffff:ffff:ffff:ffff
893c05:8000::/203c05:8fff:ffff:ffff:ffff:ffff:ffff:ffff
903c05:9000::/203c05:9fff:ffff:ffff:ffff:ffff:ffff:ffff
913c05:a000::/203c05:afff:ffff:ffff:ffff:ffff:ffff:ffff
923c05:b000::/203c05:bfff:ffff:ffff:ffff:ffff:ffff:ffff
933c05:c000::/203c05:cfff:ffff:ffff:ffff:ffff:ffff:ffff
943c05:d000::/203c05:dfff:ffff:ffff:ffff:ffff:ffff:ffff
953c05:e000::/203c05:efff:ffff:ffff:ffff:ffff:ffff:ffff
963c05:f000::/203c05:ffff:ffff:ffff:ffff:ffff:ffff:ffff
973c06::/203c06:fff:ffff:ffff:ffff:ffff:ffff:ffff
983c06:1000::/203c06:1fff:ffff:ffff:ffff:ffff:ffff:ffff
993c06:2000::/203c06:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1003c06:3000::/203c06:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1013c06:4000::/203c06:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1023c06:5000::/203c06:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1033c06:6000::/203c06:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1043c06:7000::/203c06:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1053c06:8000::/203c06:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1063c06:9000::/203c06:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1073c06:a000::/203c06:afff:ffff:ffff:ffff:ffff:ffff:ffff
1083c06:b000::/203c06:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1093c06:c000::/203c06:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1103c06:d000::/203c06:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1113c06:e000::/203c06:efff:ffff:ffff:ffff:ffff:ffff:ffff
1123c06:f000::/203c06:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1133c07::/203c07:fff:ffff:ffff:ffff:ffff:ffff:ffff
1143c07:1000::/203c07:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1153c07:2000::/203c07:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1163c07:3000::/203c07:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1173c07:4000::/203c07:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1183c07:5000::/203c07:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1193c07:6000::/203c07:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1203c07:7000::/203c07:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1213c07:8000::/203c07:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1223c07:9000::/203c07:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1233c07:a000::/203c07:afff:ffff:ffff:ffff:ffff:ffff:ffff
1243c07:b000::/203c07:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1253c07:c000::/203c07:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1263c07:d000::/203c07:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1273c07:e000::/203c07:efff:ffff:ffff:ffff:ffff:ffff:ffff
1283c07:f000::/203c07:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1293c08::/203c08:fff:ffff:ffff:ffff:ffff:ffff:ffff
1303c08:1000::/203c08:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1313c08:2000::/203c08:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1323c08:3000::/203c08:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1333c08:4000::/203c08:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1343c08:5000::/203c08:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1353c08:6000::/203c08:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1363c08:7000::/203c08:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1373c08:8000::/203c08:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1383c08:9000::/203c08:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1393c08:a000::/203c08:afff:ffff:ffff:ffff:ffff:ffff:ffff
1403c08:b000::/203c08:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1413c08:c000::/203c08:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1423c08:d000::/203c08:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1433c08:e000::/203c08:efff:ffff:ffff:ffff:ffff:ffff:ffff
1443c08:f000::/203c08:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1453c09::/203c09:fff:ffff:ffff:ffff:ffff:ffff:ffff
1463c09:1000::/203c09:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1473c09:2000::/203c09:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1483c09:3000::/203c09:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1493c09:4000::/203c09:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1503c09:5000::/203c09:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1513c09:6000::/203c09:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1523c09:7000::/203c09:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1533c09:8000::/203c09:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1543c09:9000::/203c09:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1553c09:a000::/203c09:afff:ffff:ffff:ffff:ffff:ffff:ffff
1563c09:b000::/203c09:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1573c09:c000::/203c09:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1583c09:d000::/203c09:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1593c09:e000::/203c09:efff:ffff:ffff:ffff:ffff:ffff:ffff
1603c09:f000::/203c09:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1613c0a::/203c0a:fff:ffff:ffff:ffff:ffff:ffff:ffff
1623c0a:1000::/203c0a:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1633c0a:2000::/203c0a:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1643c0a:3000::/203c0a:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1653c0a:4000::/203c0a:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1663c0a:5000::/203c0a:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1673c0a:6000::/203c0a:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1683c0a:7000::/203c0a:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1693c0a:8000::/203c0a:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1703c0a:9000::/203c0a:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1713c0a:a000::/203c0a:afff:ffff:ffff:ffff:ffff:ffff:ffff
1723c0a:b000::/203c0a:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1733c0a:c000::/203c0a:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1743c0a:d000::/203c0a:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1753c0a:e000::/203c0a:efff:ffff:ffff:ffff:ffff:ffff:ffff
1763c0a:f000::/203c0a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1773c0b::/203c0b:fff:ffff:ffff:ffff:ffff:ffff:ffff
1783c0b:1000::/203c0b:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1793c0b:2000::/203c0b:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1803c0b:3000::/203c0b:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1813c0b:4000::/203c0b:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1823c0b:5000::/203c0b:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1833c0b:6000::/203c0b:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1843c0b:7000::/203c0b:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1853c0b:8000::/203c0b:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1863c0b:9000::/203c0b:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1873c0b:a000::/203c0b:afff:ffff:ffff:ffff:ffff:ffff:ffff
1883c0b:b000::/203c0b:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1893c0b:c000::/203c0b:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1903c0b:d000::/203c0b:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1913c0b:e000::/203c0b:efff:ffff:ffff:ffff:ffff:ffff:ffff
1923c0b:f000::/203c0b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1933c0c::/203c0c:fff:ffff:ffff:ffff:ffff:ffff:ffff
1943c0c:1000::/203c0c:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1953c0c:2000::/203c0c:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1963c0c:3000::/203c0c:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1973c0c:4000::/203c0c:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1983c0c:5000::/203c0c:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1993c0c:6000::/203c0c:6fff:ffff:ffff:ffff:ffff:ffff:ffff
2003c0c:7000::/203c0c:7fff:ffff:ffff:ffff:ffff:ffff:ffff
2013c0c:8000::/203c0c:8fff:ffff:ffff:ffff:ffff:ffff:ffff
2023c0c:9000::/203c0c:9fff:ffff:ffff:ffff:ffff:ffff:ffff
2033c0c:a000::/203c0c:afff:ffff:ffff:ffff:ffff:ffff:ffff
2043c0c:b000::/203c0c:bfff:ffff:ffff:ffff:ffff:ffff:ffff
2053c0c:c000::/203c0c:cfff:ffff:ffff:ffff:ffff:ffff:ffff
2063c0c:d000::/203c0c:dfff:ffff:ffff:ffff:ffff:ffff:ffff
2073c0c:e000::/203c0c:efff:ffff:ffff:ffff:ffff:ffff:ffff
2083c0c:f000::/203c0c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2093c0d::/203c0d:fff:ffff:ffff:ffff:ffff:ffff:ffff
2103c0d:1000::/203c0d:1fff:ffff:ffff:ffff:ffff:ffff:ffff
2113c0d:2000::/203c0d:2fff:ffff:ffff:ffff:ffff:ffff:ffff
2123c0d:3000::/203c0d:3fff:ffff:ffff:ffff:ffff:ffff:ffff
2133c0d:4000::/203c0d:4fff:ffff:ffff:ffff:ffff:ffff:ffff
2143c0d:5000::/203c0d:5fff:ffff:ffff:ffff:ffff:ffff:ffff
2153c0d:6000::/203c0d:6fff:ffff:ffff:ffff:ffff:ffff:ffff
2163c0d:7000::/203c0d:7fff:ffff:ffff:ffff:ffff:ffff:ffff
2173c0d:8000::/203c0d:8fff:ffff:ffff:ffff:ffff:ffff:ffff
2183c0d:9000::/203c0d:9fff:ffff:ffff:ffff:ffff:ffff:ffff
2193c0d:a000::/203c0d:afff:ffff:ffff:ffff:ffff:ffff:ffff
2203c0d:b000::/203c0d:bfff:ffff:ffff:ffff:ffff:ffff:ffff
2213c0d:c000::/203c0d:cfff:ffff:ffff:ffff:ffff:ffff:ffff
2223c0d:d000::/203c0d:dfff:ffff:ffff:ffff:ffff:ffff:ffff
2233c0d:e000::/203c0d:efff:ffff:ffff:ffff:ffff:ffff:ffff
2243c0d:f000::/203c0d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2253c0e::/203c0e:fff:ffff:ffff:ffff:ffff:ffff:ffff
2263c0e:1000::/203c0e:1fff:ffff:ffff:ffff:ffff:ffff:ffff
2273c0e:2000::/203c0e:2fff:ffff:ffff:ffff:ffff:ffff:ffff
2283c0e:3000::/203c0e:3fff:ffff:ffff:ffff:ffff:ffff:ffff
2293c0e:4000::/203c0e:4fff:ffff:ffff:ffff:ffff:ffff:ffff
2303c0e:5000::/203c0e:5fff:ffff:ffff:ffff:ffff:ffff:ffff
2313c0e:6000::/203c0e:6fff:ffff:ffff:ffff:ffff:ffff:ffff
2323c0e:7000::/203c0e:7fff:ffff:ffff:ffff:ffff:ffff:ffff
2333c0e:8000::/203c0e:8fff:ffff:ffff:ffff:ffff:ffff:ffff
2343c0e:9000::/203c0e:9fff:ffff:ffff:ffff:ffff:ffff:ffff
2353c0e:a000::/203c0e:afff:ffff:ffff:ffff:ffff:ffff:ffff
2363c0e:b000::/203c0e:bfff:ffff:ffff:ffff:ffff:ffff:ffff
2373c0e:c000::/203c0e:cfff:ffff:ffff:ffff:ffff:ffff:ffff
2383c0e:d000::/203c0e:dfff:ffff:ffff:ffff:ffff:ffff:ffff
2393c0e:e000::/203c0e:efff:ffff:ffff:ffff:ffff:ffff:ffff
2403c0e:f000::/203c0e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2413c0f::/203c0f:fff:ffff:ffff:ffff:ffff:ffff:ffff
2423c0f:1000::/203c0f:1fff:ffff:ffff:ffff:ffff:ffff:ffff
2433c0f:2000::/203c0f:2fff:ffff:ffff:ffff:ffff:ffff:ffff
2443c0f:3000::/203c0f:3fff:ffff:ffff:ffff:ffff:ffff:ffff
2453c0f:4000::/203c0f:4fff:ffff:ffff:ffff:ffff:ffff:ffff
2463c0f:5000::/203c0f:5fff:ffff:ffff:ffff:ffff:ffff:ffff
2473c0f:6000::/203c0f:6fff:ffff:ffff:ffff:ffff:ffff:ffff
2483c0f:7000::/203c0f:7fff:ffff:ffff:ffff:ffff:ffff:ffff
2493c0f:8000::/203c0f:8fff:ffff:ffff:ffff:ffff:ffff:ffff
2503c0f:9000::/203c0f:9fff:ffff:ffff:ffff:ffff:ffff:ffff
2513c0f:a000::/203c0f:afff:ffff:ffff:ffff:ffff:ffff:ffff
2523c0f:b000::/203c0f:bfff:ffff:ffff:ffff:ffff:ffff:ffff
2533c0f:c000::/203c0f:cfff:ffff:ffff:ffff:ffff:ffff:ffff
2543c0f:d000::/203c0f:dfff:ffff:ffff:ffff:ffff:ffff:ffff
2553c0f:e000::/203c0f:efff:ffff:ffff:ffff:ffff:ffff:ffff
2563c0f:f000::/203c0f: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.