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/40
Addresses2^88
/64 networks16,777,216
Network
3c19:c25f:ff00::/40
First address
3c19:c25f:ff00::
Last address
3c19:c25f:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
309,485,009,821,345,068,724,781,056 (2^88)
/64 networks (LANs)
16,777,216
Full form
3c19:c25f:ff00:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
f.f.f.5.2.c.9.1.c.3.ip6.arpa
Split into smaller subnets/48
/41 (2)/42 (4)/43 (8)/44 (16)/48 (256)/52 (4,096)/56 (65,536)

3c19:c25f:ff00::/40 makes 256 subnets of /48.

Subnets
#SubnetLast address
13c19:c25f:ff00::/483c19:c25f:ff00:ffff:ffff:ffff:ffff:ffff
23c19:c25f:ff01::/483c19:c25f:ff01:ffff:ffff:ffff:ffff:ffff
33c19:c25f:ff02::/483c19:c25f:ff02:ffff:ffff:ffff:ffff:ffff
43c19:c25f:ff03::/483c19:c25f:ff03:ffff:ffff:ffff:ffff:ffff
53c19:c25f:ff04::/483c19:c25f:ff04:ffff:ffff:ffff:ffff:ffff
63c19:c25f:ff05::/483c19:c25f:ff05:ffff:ffff:ffff:ffff:ffff
73c19:c25f:ff06::/483c19:c25f:ff06:ffff:ffff:ffff:ffff:ffff
83c19:c25f:ff07::/483c19:c25f:ff07:ffff:ffff:ffff:ffff:ffff
93c19:c25f:ff08::/483c19:c25f:ff08:ffff:ffff:ffff:ffff:ffff
103c19:c25f:ff09::/483c19:c25f:ff09:ffff:ffff:ffff:ffff:ffff
113c19:c25f:ff0a::/483c19:c25f:ff0a:ffff:ffff:ffff:ffff:ffff
123c19:c25f:ff0b::/483c19:c25f:ff0b:ffff:ffff:ffff:ffff:ffff
133c19:c25f:ff0c::/483c19:c25f:ff0c:ffff:ffff:ffff:ffff:ffff
143c19:c25f:ff0d::/483c19:c25f:ff0d:ffff:ffff:ffff:ffff:ffff
153c19:c25f:ff0e::/483c19:c25f:ff0e:ffff:ffff:ffff:ffff:ffff
163c19:c25f:ff0f::/483c19:c25f:ff0f:ffff:ffff:ffff:ffff:ffff
173c19:c25f:ff10::/483c19:c25f:ff10:ffff:ffff:ffff:ffff:ffff
183c19:c25f:ff11::/483c19:c25f:ff11:ffff:ffff:ffff:ffff:ffff
193c19:c25f:ff12::/483c19:c25f:ff12:ffff:ffff:ffff:ffff:ffff
203c19:c25f:ff13::/483c19:c25f:ff13:ffff:ffff:ffff:ffff:ffff
213c19:c25f:ff14::/483c19:c25f:ff14:ffff:ffff:ffff:ffff:ffff
223c19:c25f:ff15::/483c19:c25f:ff15:ffff:ffff:ffff:ffff:ffff
233c19:c25f:ff16::/483c19:c25f:ff16:ffff:ffff:ffff:ffff:ffff
243c19:c25f:ff17::/483c19:c25f:ff17:ffff:ffff:ffff:ffff:ffff
253c19:c25f:ff18::/483c19:c25f:ff18:ffff:ffff:ffff:ffff:ffff
263c19:c25f:ff19::/483c19:c25f:ff19:ffff:ffff:ffff:ffff:ffff
273c19:c25f:ff1a::/483c19:c25f:ff1a:ffff:ffff:ffff:ffff:ffff
283c19:c25f:ff1b::/483c19:c25f:ff1b:ffff:ffff:ffff:ffff:ffff
293c19:c25f:ff1c::/483c19:c25f:ff1c:ffff:ffff:ffff:ffff:ffff
303c19:c25f:ff1d::/483c19:c25f:ff1d:ffff:ffff:ffff:ffff:ffff
313c19:c25f:ff1e::/483c19:c25f:ff1e:ffff:ffff:ffff:ffff:ffff
323c19:c25f:ff1f::/483c19:c25f:ff1f:ffff:ffff:ffff:ffff:ffff
333c19:c25f:ff20::/483c19:c25f:ff20:ffff:ffff:ffff:ffff:ffff
343c19:c25f:ff21::/483c19:c25f:ff21:ffff:ffff:ffff:ffff:ffff
353c19:c25f:ff22::/483c19:c25f:ff22:ffff:ffff:ffff:ffff:ffff
363c19:c25f:ff23::/483c19:c25f:ff23:ffff:ffff:ffff:ffff:ffff
373c19:c25f:ff24::/483c19:c25f:ff24:ffff:ffff:ffff:ffff:ffff
383c19:c25f:ff25::/483c19:c25f:ff25:ffff:ffff:ffff:ffff:ffff
393c19:c25f:ff26::/483c19:c25f:ff26:ffff:ffff:ffff:ffff:ffff
403c19:c25f:ff27::/483c19:c25f:ff27:ffff:ffff:ffff:ffff:ffff
413c19:c25f:ff28::/483c19:c25f:ff28:ffff:ffff:ffff:ffff:ffff
423c19:c25f:ff29::/483c19:c25f:ff29:ffff:ffff:ffff:ffff:ffff
433c19:c25f:ff2a::/483c19:c25f:ff2a:ffff:ffff:ffff:ffff:ffff
443c19:c25f:ff2b::/483c19:c25f:ff2b:ffff:ffff:ffff:ffff:ffff
453c19:c25f:ff2c::/483c19:c25f:ff2c:ffff:ffff:ffff:ffff:ffff
463c19:c25f:ff2d::/483c19:c25f:ff2d:ffff:ffff:ffff:ffff:ffff
473c19:c25f:ff2e::/483c19:c25f:ff2e:ffff:ffff:ffff:ffff:ffff
483c19:c25f:ff2f::/483c19:c25f:ff2f:ffff:ffff:ffff:ffff:ffff
493c19:c25f:ff30::/483c19:c25f:ff30:ffff:ffff:ffff:ffff:ffff
503c19:c25f:ff31::/483c19:c25f:ff31:ffff:ffff:ffff:ffff:ffff
513c19:c25f:ff32::/483c19:c25f:ff32:ffff:ffff:ffff:ffff:ffff
523c19:c25f:ff33::/483c19:c25f:ff33:ffff:ffff:ffff:ffff:ffff
533c19:c25f:ff34::/483c19:c25f:ff34:ffff:ffff:ffff:ffff:ffff
543c19:c25f:ff35::/483c19:c25f:ff35:ffff:ffff:ffff:ffff:ffff
553c19:c25f:ff36::/483c19:c25f:ff36:ffff:ffff:ffff:ffff:ffff
563c19:c25f:ff37::/483c19:c25f:ff37:ffff:ffff:ffff:ffff:ffff
573c19:c25f:ff38::/483c19:c25f:ff38:ffff:ffff:ffff:ffff:ffff
583c19:c25f:ff39::/483c19:c25f:ff39:ffff:ffff:ffff:ffff:ffff
593c19:c25f:ff3a::/483c19:c25f:ff3a:ffff:ffff:ffff:ffff:ffff
603c19:c25f:ff3b::/483c19:c25f:ff3b:ffff:ffff:ffff:ffff:ffff
613c19:c25f:ff3c::/483c19:c25f:ff3c:ffff:ffff:ffff:ffff:ffff
623c19:c25f:ff3d::/483c19:c25f:ff3d:ffff:ffff:ffff:ffff:ffff
633c19:c25f:ff3e::/483c19:c25f:ff3e:ffff:ffff:ffff:ffff:ffff
643c19:c25f:ff3f::/483c19:c25f:ff3f:ffff:ffff:ffff:ffff:ffff
653c19:c25f:ff40::/483c19:c25f:ff40:ffff:ffff:ffff:ffff:ffff
663c19:c25f:ff41::/483c19:c25f:ff41:ffff:ffff:ffff:ffff:ffff
673c19:c25f:ff42::/483c19:c25f:ff42:ffff:ffff:ffff:ffff:ffff
683c19:c25f:ff43::/483c19:c25f:ff43:ffff:ffff:ffff:ffff:ffff
693c19:c25f:ff44::/483c19:c25f:ff44:ffff:ffff:ffff:ffff:ffff
703c19:c25f:ff45::/483c19:c25f:ff45:ffff:ffff:ffff:ffff:ffff
713c19:c25f:ff46::/483c19:c25f:ff46:ffff:ffff:ffff:ffff:ffff
723c19:c25f:ff47::/483c19:c25f:ff47:ffff:ffff:ffff:ffff:ffff
733c19:c25f:ff48::/483c19:c25f:ff48:ffff:ffff:ffff:ffff:ffff
743c19:c25f:ff49::/483c19:c25f:ff49:ffff:ffff:ffff:ffff:ffff
753c19:c25f:ff4a::/483c19:c25f:ff4a:ffff:ffff:ffff:ffff:ffff
763c19:c25f:ff4b::/483c19:c25f:ff4b:ffff:ffff:ffff:ffff:ffff
773c19:c25f:ff4c::/483c19:c25f:ff4c:ffff:ffff:ffff:ffff:ffff
783c19:c25f:ff4d::/483c19:c25f:ff4d:ffff:ffff:ffff:ffff:ffff
793c19:c25f:ff4e::/483c19:c25f:ff4e:ffff:ffff:ffff:ffff:ffff
803c19:c25f:ff4f::/483c19:c25f:ff4f:ffff:ffff:ffff:ffff:ffff
813c19:c25f:ff50::/483c19:c25f:ff50:ffff:ffff:ffff:ffff:ffff
823c19:c25f:ff51::/483c19:c25f:ff51:ffff:ffff:ffff:ffff:ffff
833c19:c25f:ff52::/483c19:c25f:ff52:ffff:ffff:ffff:ffff:ffff
843c19:c25f:ff53::/483c19:c25f:ff53:ffff:ffff:ffff:ffff:ffff
853c19:c25f:ff54::/483c19:c25f:ff54:ffff:ffff:ffff:ffff:ffff
863c19:c25f:ff55::/483c19:c25f:ff55:ffff:ffff:ffff:ffff:ffff
873c19:c25f:ff56::/483c19:c25f:ff56:ffff:ffff:ffff:ffff:ffff
883c19:c25f:ff57::/483c19:c25f:ff57:ffff:ffff:ffff:ffff:ffff
893c19:c25f:ff58::/483c19:c25f:ff58:ffff:ffff:ffff:ffff:ffff
903c19:c25f:ff59::/483c19:c25f:ff59:ffff:ffff:ffff:ffff:ffff
913c19:c25f:ff5a::/483c19:c25f:ff5a:ffff:ffff:ffff:ffff:ffff
923c19:c25f:ff5b::/483c19:c25f:ff5b:ffff:ffff:ffff:ffff:ffff
933c19:c25f:ff5c::/483c19:c25f:ff5c:ffff:ffff:ffff:ffff:ffff
943c19:c25f:ff5d::/483c19:c25f:ff5d:ffff:ffff:ffff:ffff:ffff
953c19:c25f:ff5e::/483c19:c25f:ff5e:ffff:ffff:ffff:ffff:ffff
963c19:c25f:ff5f::/483c19:c25f:ff5f:ffff:ffff:ffff:ffff:ffff
973c19:c25f:ff60::/483c19:c25f:ff60:ffff:ffff:ffff:ffff:ffff
983c19:c25f:ff61::/483c19:c25f:ff61:ffff:ffff:ffff:ffff:ffff
993c19:c25f:ff62::/483c19:c25f:ff62:ffff:ffff:ffff:ffff:ffff
1003c19:c25f:ff63::/483c19:c25f:ff63:ffff:ffff:ffff:ffff:ffff
1013c19:c25f:ff64::/483c19:c25f:ff64:ffff:ffff:ffff:ffff:ffff
1023c19:c25f:ff65::/483c19:c25f:ff65:ffff:ffff:ffff:ffff:ffff
1033c19:c25f:ff66::/483c19:c25f:ff66:ffff:ffff:ffff:ffff:ffff
1043c19:c25f:ff67::/483c19:c25f:ff67:ffff:ffff:ffff:ffff:ffff
1053c19:c25f:ff68::/483c19:c25f:ff68:ffff:ffff:ffff:ffff:ffff
1063c19:c25f:ff69::/483c19:c25f:ff69:ffff:ffff:ffff:ffff:ffff
1073c19:c25f:ff6a::/483c19:c25f:ff6a:ffff:ffff:ffff:ffff:ffff
1083c19:c25f:ff6b::/483c19:c25f:ff6b:ffff:ffff:ffff:ffff:ffff
1093c19:c25f:ff6c::/483c19:c25f:ff6c:ffff:ffff:ffff:ffff:ffff
1103c19:c25f:ff6d::/483c19:c25f:ff6d:ffff:ffff:ffff:ffff:ffff
1113c19:c25f:ff6e::/483c19:c25f:ff6e:ffff:ffff:ffff:ffff:ffff
1123c19:c25f:ff6f::/483c19:c25f:ff6f:ffff:ffff:ffff:ffff:ffff
1133c19:c25f:ff70::/483c19:c25f:ff70:ffff:ffff:ffff:ffff:ffff
1143c19:c25f:ff71::/483c19:c25f:ff71:ffff:ffff:ffff:ffff:ffff
1153c19:c25f:ff72::/483c19:c25f:ff72:ffff:ffff:ffff:ffff:ffff
1163c19:c25f:ff73::/483c19:c25f:ff73:ffff:ffff:ffff:ffff:ffff
1173c19:c25f:ff74::/483c19:c25f:ff74:ffff:ffff:ffff:ffff:ffff
1183c19:c25f:ff75::/483c19:c25f:ff75:ffff:ffff:ffff:ffff:ffff
1193c19:c25f:ff76::/483c19:c25f:ff76:ffff:ffff:ffff:ffff:ffff
1203c19:c25f:ff77::/483c19:c25f:ff77:ffff:ffff:ffff:ffff:ffff
1213c19:c25f:ff78::/483c19:c25f:ff78:ffff:ffff:ffff:ffff:ffff
1223c19:c25f:ff79::/483c19:c25f:ff79:ffff:ffff:ffff:ffff:ffff
1233c19:c25f:ff7a::/483c19:c25f:ff7a:ffff:ffff:ffff:ffff:ffff
1243c19:c25f:ff7b::/483c19:c25f:ff7b:ffff:ffff:ffff:ffff:ffff
1253c19:c25f:ff7c::/483c19:c25f:ff7c:ffff:ffff:ffff:ffff:ffff
1263c19:c25f:ff7d::/483c19:c25f:ff7d:ffff:ffff:ffff:ffff:ffff
1273c19:c25f:ff7e::/483c19:c25f:ff7e:ffff:ffff:ffff:ffff:ffff
1283c19:c25f:ff7f::/483c19:c25f:ff7f:ffff:ffff:ffff:ffff:ffff
1293c19:c25f:ff80::/483c19:c25f:ff80:ffff:ffff:ffff:ffff:ffff
1303c19:c25f:ff81::/483c19:c25f:ff81:ffff:ffff:ffff:ffff:ffff
1313c19:c25f:ff82::/483c19:c25f:ff82:ffff:ffff:ffff:ffff:ffff
1323c19:c25f:ff83::/483c19:c25f:ff83:ffff:ffff:ffff:ffff:ffff
1333c19:c25f:ff84::/483c19:c25f:ff84:ffff:ffff:ffff:ffff:ffff
1343c19:c25f:ff85::/483c19:c25f:ff85:ffff:ffff:ffff:ffff:ffff
1353c19:c25f:ff86::/483c19:c25f:ff86:ffff:ffff:ffff:ffff:ffff
1363c19:c25f:ff87::/483c19:c25f:ff87:ffff:ffff:ffff:ffff:ffff
1373c19:c25f:ff88::/483c19:c25f:ff88:ffff:ffff:ffff:ffff:ffff
1383c19:c25f:ff89::/483c19:c25f:ff89:ffff:ffff:ffff:ffff:ffff
1393c19:c25f:ff8a::/483c19:c25f:ff8a:ffff:ffff:ffff:ffff:ffff
1403c19:c25f:ff8b::/483c19:c25f:ff8b:ffff:ffff:ffff:ffff:ffff
1413c19:c25f:ff8c::/483c19:c25f:ff8c:ffff:ffff:ffff:ffff:ffff
1423c19:c25f:ff8d::/483c19:c25f:ff8d:ffff:ffff:ffff:ffff:ffff
1433c19:c25f:ff8e::/483c19:c25f:ff8e:ffff:ffff:ffff:ffff:ffff
1443c19:c25f:ff8f::/483c19:c25f:ff8f:ffff:ffff:ffff:ffff:ffff
1453c19:c25f:ff90::/483c19:c25f:ff90:ffff:ffff:ffff:ffff:ffff
1463c19:c25f:ff91::/483c19:c25f:ff91:ffff:ffff:ffff:ffff:ffff
1473c19:c25f:ff92::/483c19:c25f:ff92:ffff:ffff:ffff:ffff:ffff
1483c19:c25f:ff93::/483c19:c25f:ff93:ffff:ffff:ffff:ffff:ffff
1493c19:c25f:ff94::/483c19:c25f:ff94:ffff:ffff:ffff:ffff:ffff
1503c19:c25f:ff95::/483c19:c25f:ff95:ffff:ffff:ffff:ffff:ffff
1513c19:c25f:ff96::/483c19:c25f:ff96:ffff:ffff:ffff:ffff:ffff
1523c19:c25f:ff97::/483c19:c25f:ff97:ffff:ffff:ffff:ffff:ffff
1533c19:c25f:ff98::/483c19:c25f:ff98:ffff:ffff:ffff:ffff:ffff
1543c19:c25f:ff99::/483c19:c25f:ff99:ffff:ffff:ffff:ffff:ffff
1553c19:c25f:ff9a::/483c19:c25f:ff9a:ffff:ffff:ffff:ffff:ffff
1563c19:c25f:ff9b::/483c19:c25f:ff9b:ffff:ffff:ffff:ffff:ffff
1573c19:c25f:ff9c::/483c19:c25f:ff9c:ffff:ffff:ffff:ffff:ffff
1583c19:c25f:ff9d::/483c19:c25f:ff9d:ffff:ffff:ffff:ffff:ffff
1593c19:c25f:ff9e::/483c19:c25f:ff9e:ffff:ffff:ffff:ffff:ffff
1603c19:c25f:ff9f::/483c19:c25f:ff9f:ffff:ffff:ffff:ffff:ffff
1613c19:c25f:ffa0::/483c19:c25f:ffa0:ffff:ffff:ffff:ffff:ffff
1623c19:c25f:ffa1::/483c19:c25f:ffa1:ffff:ffff:ffff:ffff:ffff
1633c19:c25f:ffa2::/483c19:c25f:ffa2:ffff:ffff:ffff:ffff:ffff
1643c19:c25f:ffa3::/483c19:c25f:ffa3:ffff:ffff:ffff:ffff:ffff
1653c19:c25f:ffa4::/483c19:c25f:ffa4:ffff:ffff:ffff:ffff:ffff
1663c19:c25f:ffa5::/483c19:c25f:ffa5:ffff:ffff:ffff:ffff:ffff
1673c19:c25f:ffa6::/483c19:c25f:ffa6:ffff:ffff:ffff:ffff:ffff
1683c19:c25f:ffa7::/483c19:c25f:ffa7:ffff:ffff:ffff:ffff:ffff
1693c19:c25f:ffa8::/483c19:c25f:ffa8:ffff:ffff:ffff:ffff:ffff
1703c19:c25f:ffa9::/483c19:c25f:ffa9:ffff:ffff:ffff:ffff:ffff
1713c19:c25f:ffaa::/483c19:c25f:ffaa:ffff:ffff:ffff:ffff:ffff
1723c19:c25f:ffab::/483c19:c25f:ffab:ffff:ffff:ffff:ffff:ffff
1733c19:c25f:ffac::/483c19:c25f:ffac:ffff:ffff:ffff:ffff:ffff
1743c19:c25f:ffad::/483c19:c25f:ffad:ffff:ffff:ffff:ffff:ffff
1753c19:c25f:ffae::/483c19:c25f:ffae:ffff:ffff:ffff:ffff:ffff
1763c19:c25f:ffaf::/483c19:c25f:ffaf:ffff:ffff:ffff:ffff:ffff
1773c19:c25f:ffb0::/483c19:c25f:ffb0:ffff:ffff:ffff:ffff:ffff
1783c19:c25f:ffb1::/483c19:c25f:ffb1:ffff:ffff:ffff:ffff:ffff
1793c19:c25f:ffb2::/483c19:c25f:ffb2:ffff:ffff:ffff:ffff:ffff
1803c19:c25f:ffb3::/483c19:c25f:ffb3:ffff:ffff:ffff:ffff:ffff
1813c19:c25f:ffb4::/483c19:c25f:ffb4:ffff:ffff:ffff:ffff:ffff
1823c19:c25f:ffb5::/483c19:c25f:ffb5:ffff:ffff:ffff:ffff:ffff
1833c19:c25f:ffb6::/483c19:c25f:ffb6:ffff:ffff:ffff:ffff:ffff
1843c19:c25f:ffb7::/483c19:c25f:ffb7:ffff:ffff:ffff:ffff:ffff
1853c19:c25f:ffb8::/483c19:c25f:ffb8:ffff:ffff:ffff:ffff:ffff
1863c19:c25f:ffb9::/483c19:c25f:ffb9:ffff:ffff:ffff:ffff:ffff
1873c19:c25f:ffba::/483c19:c25f:ffba:ffff:ffff:ffff:ffff:ffff
1883c19:c25f:ffbb::/483c19:c25f:ffbb:ffff:ffff:ffff:ffff:ffff
1893c19:c25f:ffbc::/483c19:c25f:ffbc:ffff:ffff:ffff:ffff:ffff
1903c19:c25f:ffbd::/483c19:c25f:ffbd:ffff:ffff:ffff:ffff:ffff
1913c19:c25f:ffbe::/483c19:c25f:ffbe:ffff:ffff:ffff:ffff:ffff
1923c19:c25f:ffbf::/483c19:c25f:ffbf:ffff:ffff:ffff:ffff:ffff
1933c19:c25f:ffc0::/483c19:c25f:ffc0:ffff:ffff:ffff:ffff:ffff
1943c19:c25f:ffc1::/483c19:c25f:ffc1:ffff:ffff:ffff:ffff:ffff
1953c19:c25f:ffc2::/483c19:c25f:ffc2:ffff:ffff:ffff:ffff:ffff
1963c19:c25f:ffc3::/483c19:c25f:ffc3:ffff:ffff:ffff:ffff:ffff
1973c19:c25f:ffc4::/483c19:c25f:ffc4:ffff:ffff:ffff:ffff:ffff
1983c19:c25f:ffc5::/483c19:c25f:ffc5:ffff:ffff:ffff:ffff:ffff
1993c19:c25f:ffc6::/483c19:c25f:ffc6:ffff:ffff:ffff:ffff:ffff
2003c19:c25f:ffc7::/483c19:c25f:ffc7:ffff:ffff:ffff:ffff:ffff
2013c19:c25f:ffc8::/483c19:c25f:ffc8:ffff:ffff:ffff:ffff:ffff
2023c19:c25f:ffc9::/483c19:c25f:ffc9:ffff:ffff:ffff:ffff:ffff
2033c19:c25f:ffca::/483c19:c25f:ffca:ffff:ffff:ffff:ffff:ffff
2043c19:c25f:ffcb::/483c19:c25f:ffcb:ffff:ffff:ffff:ffff:ffff
2053c19:c25f:ffcc::/483c19:c25f:ffcc:ffff:ffff:ffff:ffff:ffff
2063c19:c25f:ffcd::/483c19:c25f:ffcd:ffff:ffff:ffff:ffff:ffff
2073c19:c25f:ffce::/483c19:c25f:ffce:ffff:ffff:ffff:ffff:ffff
2083c19:c25f:ffcf::/483c19:c25f:ffcf:ffff:ffff:ffff:ffff:ffff
2093c19:c25f:ffd0::/483c19:c25f:ffd0:ffff:ffff:ffff:ffff:ffff
2103c19:c25f:ffd1::/483c19:c25f:ffd1:ffff:ffff:ffff:ffff:ffff
2113c19:c25f:ffd2::/483c19:c25f:ffd2:ffff:ffff:ffff:ffff:ffff
2123c19:c25f:ffd3::/483c19:c25f:ffd3:ffff:ffff:ffff:ffff:ffff
2133c19:c25f:ffd4::/483c19:c25f:ffd4:ffff:ffff:ffff:ffff:ffff
2143c19:c25f:ffd5::/483c19:c25f:ffd5:ffff:ffff:ffff:ffff:ffff
2153c19:c25f:ffd6::/483c19:c25f:ffd6:ffff:ffff:ffff:ffff:ffff
2163c19:c25f:ffd7::/483c19:c25f:ffd7:ffff:ffff:ffff:ffff:ffff
2173c19:c25f:ffd8::/483c19:c25f:ffd8:ffff:ffff:ffff:ffff:ffff
2183c19:c25f:ffd9::/483c19:c25f:ffd9:ffff:ffff:ffff:ffff:ffff
2193c19:c25f:ffda::/483c19:c25f:ffda:ffff:ffff:ffff:ffff:ffff
2203c19:c25f:ffdb::/483c19:c25f:ffdb:ffff:ffff:ffff:ffff:ffff
2213c19:c25f:ffdc::/483c19:c25f:ffdc:ffff:ffff:ffff:ffff:ffff
2223c19:c25f:ffdd::/483c19:c25f:ffdd:ffff:ffff:ffff:ffff:ffff
2233c19:c25f:ffde::/483c19:c25f:ffde:ffff:ffff:ffff:ffff:ffff
2243c19:c25f:ffdf::/483c19:c25f:ffdf:ffff:ffff:ffff:ffff:ffff
2253c19:c25f:ffe0::/483c19:c25f:ffe0:ffff:ffff:ffff:ffff:ffff
2263c19:c25f:ffe1::/483c19:c25f:ffe1:ffff:ffff:ffff:ffff:ffff
2273c19:c25f:ffe2::/483c19:c25f:ffe2:ffff:ffff:ffff:ffff:ffff
2283c19:c25f:ffe3::/483c19:c25f:ffe3:ffff:ffff:ffff:ffff:ffff
2293c19:c25f:ffe4::/483c19:c25f:ffe4:ffff:ffff:ffff:ffff:ffff
2303c19:c25f:ffe5::/483c19:c25f:ffe5:ffff:ffff:ffff:ffff:ffff
2313c19:c25f:ffe6::/483c19:c25f:ffe6:ffff:ffff:ffff:ffff:ffff
2323c19:c25f:ffe7::/483c19:c25f:ffe7:ffff:ffff:ffff:ffff:ffff
2333c19:c25f:ffe8::/483c19:c25f:ffe8:ffff:ffff:ffff:ffff:ffff
2343c19:c25f:ffe9::/483c19:c25f:ffe9:ffff:ffff:ffff:ffff:ffff
2353c19:c25f:ffea::/483c19:c25f:ffea:ffff:ffff:ffff:ffff:ffff
2363c19:c25f:ffeb::/483c19:c25f:ffeb:ffff:ffff:ffff:ffff:ffff
2373c19:c25f:ffec::/483c19:c25f:ffec:ffff:ffff:ffff:ffff:ffff
2383c19:c25f:ffed::/483c19:c25f:ffed:ffff:ffff:ffff:ffff:ffff
2393c19:c25f:ffee::/483c19:c25f:ffee:ffff:ffff:ffff:ffff:ffff
2403c19:c25f:ffef::/483c19:c25f:ffef:ffff:ffff:ffff:ffff:ffff
2413c19:c25f:fff0::/483c19:c25f:fff0:ffff:ffff:ffff:ffff:ffff
2423c19:c25f:fff1::/483c19:c25f:fff1:ffff:ffff:ffff:ffff:ffff
2433c19:c25f:fff2::/483c19:c25f:fff2:ffff:ffff:ffff:ffff:ffff
2443c19:c25f:fff3::/483c19:c25f:fff3:ffff:ffff:ffff:ffff:ffff
2453c19:c25f:fff4::/483c19:c25f:fff4:ffff:ffff:ffff:ffff:ffff
2463c19:c25f:fff5::/483c19:c25f:fff5:ffff:ffff:ffff:ffff:ffff
2473c19:c25f:fff6::/483c19:c25f:fff6:ffff:ffff:ffff:ffff:ffff
2483c19:c25f:fff7::/483c19:c25f:fff7:ffff:ffff:ffff:ffff:ffff
2493c19:c25f:fff8::/483c19:c25f:fff8:ffff:ffff:ffff:ffff:ffff
2503c19:c25f:fff9::/483c19:c25f:fff9:ffff:ffff:ffff:ffff:ffff
2513c19:c25f:fffa::/483c19:c25f:fffa:ffff:ffff:ffff:ffff:ffff
2523c19:c25f:fffb::/483c19:c25f:fffb:ffff:ffff:ffff:ffff:ffff
2533c19:c25f:fffc::/483c19:c25f:fffc:ffff:ffff:ffff:ffff:ffff
2543c19:c25f:fffd::/483c19:c25f:fffd:ffff:ffff:ffff:ffff:ffff
2553c19:c25f:fffe::/483c19:c25f:fffe:ffff:ffff:ffff:ffff:ffff
2563c19:c25f:ffff::/483c19:c25f: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.