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.

Network0.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
0.0.0.0
Broadcast address
0.255.255.255
First usable
0.0.0.1
Last usable
0.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
This network 0.0.0.0/8
Not routed; 0.0.0.0 means "any address" in settings
Old class
A (default /8)
As numbers
Hex 00000000 · Integer 0 to 16777215
Reverse DNS zone
0.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00000000..00000000.00000000.000000000.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network00000000..00000000.00000000.000000000.0.0.0
Broadcast00000000..11111111.11111111.111111110.255.255.255
Split into smaller subnets/20
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

0.0.0.0/8 makes 4,096 subnets of /20; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
10.0.0.0/200.0.0.1 to 0.0.15.2540.0.15.2554,094
20.0.16.0/200.0.16.1 to 0.0.31.2540.0.31.2554,094
30.0.32.0/200.0.32.1 to 0.0.47.2540.0.47.2554,094
40.0.48.0/200.0.48.1 to 0.0.63.2540.0.63.2554,094
50.0.64.0/200.0.64.1 to 0.0.79.2540.0.79.2554,094
60.0.80.0/200.0.80.1 to 0.0.95.2540.0.95.2554,094
70.0.96.0/200.0.96.1 to 0.0.111.2540.0.111.2554,094
80.0.112.0/200.0.112.1 to 0.0.127.2540.0.127.2554,094
90.0.128.0/200.0.128.1 to 0.0.143.2540.0.143.2554,094
100.0.144.0/200.0.144.1 to 0.0.159.2540.0.159.2554,094
110.0.160.0/200.0.160.1 to 0.0.175.2540.0.175.2554,094
120.0.176.0/200.0.176.1 to 0.0.191.2540.0.191.2554,094
130.0.192.0/200.0.192.1 to 0.0.207.2540.0.207.2554,094
140.0.208.0/200.0.208.1 to 0.0.223.2540.0.223.2554,094
150.0.224.0/200.0.224.1 to 0.0.239.2540.0.239.2554,094
160.0.240.0/200.0.240.1 to 0.0.255.2540.0.255.2554,094
170.1.0.0/200.1.0.1 to 0.1.15.2540.1.15.2554,094
180.1.16.0/200.1.16.1 to 0.1.31.2540.1.31.2554,094
190.1.32.0/200.1.32.1 to 0.1.47.2540.1.47.2554,094
200.1.48.0/200.1.48.1 to 0.1.63.2540.1.63.2554,094
210.1.64.0/200.1.64.1 to 0.1.79.2540.1.79.2554,094
220.1.80.0/200.1.80.1 to 0.1.95.2540.1.95.2554,094
230.1.96.0/200.1.96.1 to 0.1.111.2540.1.111.2554,094
240.1.112.0/200.1.112.1 to 0.1.127.2540.1.127.2554,094
250.1.128.0/200.1.128.1 to 0.1.143.2540.1.143.2554,094
260.1.144.0/200.1.144.1 to 0.1.159.2540.1.159.2554,094
270.1.160.0/200.1.160.1 to 0.1.175.2540.1.175.2554,094
280.1.176.0/200.1.176.1 to 0.1.191.2540.1.191.2554,094
290.1.192.0/200.1.192.1 to 0.1.207.2540.1.207.2554,094
300.1.208.0/200.1.208.1 to 0.1.223.2540.1.223.2554,094
310.1.224.0/200.1.224.1 to 0.1.239.2540.1.239.2554,094
320.1.240.0/200.1.240.1 to 0.1.255.2540.1.255.2554,094
330.2.0.0/200.2.0.1 to 0.2.15.2540.2.15.2554,094
340.2.16.0/200.2.16.1 to 0.2.31.2540.2.31.2554,094
350.2.32.0/200.2.32.1 to 0.2.47.2540.2.47.2554,094
360.2.48.0/200.2.48.1 to 0.2.63.2540.2.63.2554,094
370.2.64.0/200.2.64.1 to 0.2.79.2540.2.79.2554,094
380.2.80.0/200.2.80.1 to 0.2.95.2540.2.95.2554,094
390.2.96.0/200.2.96.1 to 0.2.111.2540.2.111.2554,094
400.2.112.0/200.2.112.1 to 0.2.127.2540.2.127.2554,094
410.2.128.0/200.2.128.1 to 0.2.143.2540.2.143.2554,094
420.2.144.0/200.2.144.1 to 0.2.159.2540.2.159.2554,094
430.2.160.0/200.2.160.1 to 0.2.175.2540.2.175.2554,094
440.2.176.0/200.2.176.1 to 0.2.191.2540.2.191.2554,094
450.2.192.0/200.2.192.1 to 0.2.207.2540.2.207.2554,094
460.2.208.0/200.2.208.1 to 0.2.223.2540.2.223.2554,094
470.2.224.0/200.2.224.1 to 0.2.239.2540.2.239.2554,094
480.2.240.0/200.2.240.1 to 0.2.255.2540.2.255.2554,094
490.3.0.0/200.3.0.1 to 0.3.15.2540.3.15.2554,094
500.3.16.0/200.3.16.1 to 0.3.31.2540.3.31.2554,094
510.3.32.0/200.3.32.1 to 0.3.47.2540.3.47.2554,094
520.3.48.0/200.3.48.1 to 0.3.63.2540.3.63.2554,094
530.3.64.0/200.3.64.1 to 0.3.79.2540.3.79.2554,094
540.3.80.0/200.3.80.1 to 0.3.95.2540.3.95.2554,094
550.3.96.0/200.3.96.1 to 0.3.111.2540.3.111.2554,094
560.3.112.0/200.3.112.1 to 0.3.127.2540.3.127.2554,094
570.3.128.0/200.3.128.1 to 0.3.143.2540.3.143.2554,094
580.3.144.0/200.3.144.1 to 0.3.159.2540.3.159.2554,094
590.3.160.0/200.3.160.1 to 0.3.175.2540.3.175.2554,094
600.3.176.0/200.3.176.1 to 0.3.191.2540.3.191.2554,094
610.3.192.0/200.3.192.1 to 0.3.207.2540.3.207.2554,094
620.3.208.0/200.3.208.1 to 0.3.223.2540.3.223.2554,094
630.3.224.0/200.3.224.1 to 0.3.239.2540.3.239.2554,094
640.3.240.0/200.3.240.1 to 0.3.255.2540.3.255.2554,094
650.4.0.0/200.4.0.1 to 0.4.15.2540.4.15.2554,094
660.4.16.0/200.4.16.1 to 0.4.31.2540.4.31.2554,094
670.4.32.0/200.4.32.1 to 0.4.47.2540.4.47.2554,094
680.4.48.0/200.4.48.1 to 0.4.63.2540.4.63.2554,094
690.4.64.0/200.4.64.1 to 0.4.79.2540.4.79.2554,094
700.4.80.0/200.4.80.1 to 0.4.95.2540.4.95.2554,094
710.4.96.0/200.4.96.1 to 0.4.111.2540.4.111.2554,094
720.4.112.0/200.4.112.1 to 0.4.127.2540.4.127.2554,094
730.4.128.0/200.4.128.1 to 0.4.143.2540.4.143.2554,094
740.4.144.0/200.4.144.1 to 0.4.159.2540.4.159.2554,094
750.4.160.0/200.4.160.1 to 0.4.175.2540.4.175.2554,094
760.4.176.0/200.4.176.1 to 0.4.191.2540.4.191.2554,094
770.4.192.0/200.4.192.1 to 0.4.207.2540.4.207.2554,094
780.4.208.0/200.4.208.1 to 0.4.223.2540.4.223.2554,094
790.4.224.0/200.4.224.1 to 0.4.239.2540.4.239.2554,094
800.4.240.0/200.4.240.1 to 0.4.255.2540.4.255.2554,094
810.5.0.0/200.5.0.1 to 0.5.15.2540.5.15.2554,094
820.5.16.0/200.5.16.1 to 0.5.31.2540.5.31.2554,094
830.5.32.0/200.5.32.1 to 0.5.47.2540.5.47.2554,094
840.5.48.0/200.5.48.1 to 0.5.63.2540.5.63.2554,094
850.5.64.0/200.5.64.1 to 0.5.79.2540.5.79.2554,094
860.5.80.0/200.5.80.1 to 0.5.95.2540.5.95.2554,094
870.5.96.0/200.5.96.1 to 0.5.111.2540.5.111.2554,094
880.5.112.0/200.5.112.1 to 0.5.127.2540.5.127.2554,094
890.5.128.0/200.5.128.1 to 0.5.143.2540.5.143.2554,094
900.5.144.0/200.5.144.1 to 0.5.159.2540.5.159.2554,094
910.5.160.0/200.5.160.1 to 0.5.175.2540.5.175.2554,094
920.5.176.0/200.5.176.1 to 0.5.191.2540.5.191.2554,094
930.5.192.0/200.5.192.1 to 0.5.207.2540.5.207.2554,094
940.5.208.0/200.5.208.1 to 0.5.223.2540.5.223.2554,094
950.5.224.0/200.5.224.1 to 0.5.239.2540.5.239.2554,094
960.5.240.0/200.5.240.1 to 0.5.255.2540.5.255.2554,094
970.6.0.0/200.6.0.1 to 0.6.15.2540.6.15.2554,094
980.6.16.0/200.6.16.1 to 0.6.31.2540.6.31.2554,094
990.6.32.0/200.6.32.1 to 0.6.47.2540.6.47.2554,094
1000.6.48.0/200.6.48.1 to 0.6.63.2540.6.63.2554,094
1010.6.64.0/200.6.64.1 to 0.6.79.2540.6.79.2554,094
1020.6.80.0/200.6.80.1 to 0.6.95.2540.6.95.2554,094
1030.6.96.0/200.6.96.1 to 0.6.111.2540.6.111.2554,094
1040.6.112.0/200.6.112.1 to 0.6.127.2540.6.127.2554,094
1050.6.128.0/200.6.128.1 to 0.6.143.2540.6.143.2554,094
1060.6.144.0/200.6.144.1 to 0.6.159.2540.6.159.2554,094
1070.6.160.0/200.6.160.1 to 0.6.175.2540.6.175.2554,094
1080.6.176.0/200.6.176.1 to 0.6.191.2540.6.191.2554,094
1090.6.192.0/200.6.192.1 to 0.6.207.2540.6.207.2554,094
1100.6.208.0/200.6.208.1 to 0.6.223.2540.6.223.2554,094
1110.6.224.0/200.6.224.1 to 0.6.239.2540.6.239.2554,094
1120.6.240.0/200.6.240.1 to 0.6.255.2540.6.255.2554,094
1130.7.0.0/200.7.0.1 to 0.7.15.2540.7.15.2554,094
1140.7.16.0/200.7.16.1 to 0.7.31.2540.7.31.2554,094
1150.7.32.0/200.7.32.1 to 0.7.47.2540.7.47.2554,094
1160.7.48.0/200.7.48.1 to 0.7.63.2540.7.63.2554,094
1170.7.64.0/200.7.64.1 to 0.7.79.2540.7.79.2554,094
1180.7.80.0/200.7.80.1 to 0.7.95.2540.7.95.2554,094
1190.7.96.0/200.7.96.1 to 0.7.111.2540.7.111.2554,094
1200.7.112.0/200.7.112.1 to 0.7.127.2540.7.127.2554,094
1210.7.128.0/200.7.128.1 to 0.7.143.2540.7.143.2554,094
1220.7.144.0/200.7.144.1 to 0.7.159.2540.7.159.2554,094
1230.7.160.0/200.7.160.1 to 0.7.175.2540.7.175.2554,094
1240.7.176.0/200.7.176.1 to 0.7.191.2540.7.191.2554,094
1250.7.192.0/200.7.192.1 to 0.7.207.2540.7.207.2554,094
1260.7.208.0/200.7.208.1 to 0.7.223.2540.7.223.2554,094
1270.7.224.0/200.7.224.1 to 0.7.239.2540.7.239.2554,094
1280.7.240.0/200.7.240.1 to 0.7.255.2540.7.255.2554,094
1290.8.0.0/200.8.0.1 to 0.8.15.2540.8.15.2554,094
1300.8.16.0/200.8.16.1 to 0.8.31.2540.8.31.2554,094
1310.8.32.0/200.8.32.1 to 0.8.47.2540.8.47.2554,094
1320.8.48.0/200.8.48.1 to 0.8.63.2540.8.63.2554,094
1330.8.64.0/200.8.64.1 to 0.8.79.2540.8.79.2554,094
1340.8.80.0/200.8.80.1 to 0.8.95.2540.8.95.2554,094
1350.8.96.0/200.8.96.1 to 0.8.111.2540.8.111.2554,094
1360.8.112.0/200.8.112.1 to 0.8.127.2540.8.127.2554,094
1370.8.128.0/200.8.128.1 to 0.8.143.2540.8.143.2554,094
1380.8.144.0/200.8.144.1 to 0.8.159.2540.8.159.2554,094
1390.8.160.0/200.8.160.1 to 0.8.175.2540.8.175.2554,094
1400.8.176.0/200.8.176.1 to 0.8.191.2540.8.191.2554,094
1410.8.192.0/200.8.192.1 to 0.8.207.2540.8.207.2554,094
1420.8.208.0/200.8.208.1 to 0.8.223.2540.8.223.2554,094
1430.8.224.0/200.8.224.1 to 0.8.239.2540.8.239.2554,094
1440.8.240.0/200.8.240.1 to 0.8.255.2540.8.255.2554,094
1450.9.0.0/200.9.0.1 to 0.9.15.2540.9.15.2554,094
1460.9.16.0/200.9.16.1 to 0.9.31.2540.9.31.2554,094
1470.9.32.0/200.9.32.1 to 0.9.47.2540.9.47.2554,094
1480.9.48.0/200.9.48.1 to 0.9.63.2540.9.63.2554,094
1490.9.64.0/200.9.64.1 to 0.9.79.2540.9.79.2554,094
1500.9.80.0/200.9.80.1 to 0.9.95.2540.9.95.2554,094
1510.9.96.0/200.9.96.1 to 0.9.111.2540.9.111.2554,094
1520.9.112.0/200.9.112.1 to 0.9.127.2540.9.127.2554,094
1530.9.128.0/200.9.128.1 to 0.9.143.2540.9.143.2554,094
1540.9.144.0/200.9.144.1 to 0.9.159.2540.9.159.2554,094
1550.9.160.0/200.9.160.1 to 0.9.175.2540.9.175.2554,094
1560.9.176.0/200.9.176.1 to 0.9.191.2540.9.191.2554,094
1570.9.192.0/200.9.192.1 to 0.9.207.2540.9.207.2554,094
1580.9.208.0/200.9.208.1 to 0.9.223.2540.9.223.2554,094
1590.9.224.0/200.9.224.1 to 0.9.239.2540.9.239.2554,094
1600.9.240.0/200.9.240.1 to 0.9.255.2540.9.255.2554,094
1610.10.0.0/200.10.0.1 to 0.10.15.2540.10.15.2554,094
1620.10.16.0/200.10.16.1 to 0.10.31.2540.10.31.2554,094
1630.10.32.0/200.10.32.1 to 0.10.47.2540.10.47.2554,094
1640.10.48.0/200.10.48.1 to 0.10.63.2540.10.63.2554,094
1650.10.64.0/200.10.64.1 to 0.10.79.2540.10.79.2554,094
1660.10.80.0/200.10.80.1 to 0.10.95.2540.10.95.2554,094
1670.10.96.0/200.10.96.1 to 0.10.111.2540.10.111.2554,094
1680.10.112.0/200.10.112.1 to 0.10.127.2540.10.127.2554,094
1690.10.128.0/200.10.128.1 to 0.10.143.2540.10.143.2554,094
1700.10.144.0/200.10.144.1 to 0.10.159.2540.10.159.2554,094
1710.10.160.0/200.10.160.1 to 0.10.175.2540.10.175.2554,094
1720.10.176.0/200.10.176.1 to 0.10.191.2540.10.191.2554,094
1730.10.192.0/200.10.192.1 to 0.10.207.2540.10.207.2554,094
1740.10.208.0/200.10.208.1 to 0.10.223.2540.10.223.2554,094
1750.10.224.0/200.10.224.1 to 0.10.239.2540.10.239.2554,094
1760.10.240.0/200.10.240.1 to 0.10.255.2540.10.255.2554,094
1770.11.0.0/200.11.0.1 to 0.11.15.2540.11.15.2554,094
1780.11.16.0/200.11.16.1 to 0.11.31.2540.11.31.2554,094
1790.11.32.0/200.11.32.1 to 0.11.47.2540.11.47.2554,094
1800.11.48.0/200.11.48.1 to 0.11.63.2540.11.63.2554,094
1810.11.64.0/200.11.64.1 to 0.11.79.2540.11.79.2554,094
1820.11.80.0/200.11.80.1 to 0.11.95.2540.11.95.2554,094
1830.11.96.0/200.11.96.1 to 0.11.111.2540.11.111.2554,094
1840.11.112.0/200.11.112.1 to 0.11.127.2540.11.127.2554,094
1850.11.128.0/200.11.128.1 to 0.11.143.2540.11.143.2554,094
1860.11.144.0/200.11.144.1 to 0.11.159.2540.11.159.2554,094
1870.11.160.0/200.11.160.1 to 0.11.175.2540.11.175.2554,094
1880.11.176.0/200.11.176.1 to 0.11.191.2540.11.191.2554,094
1890.11.192.0/200.11.192.1 to 0.11.207.2540.11.207.2554,094
1900.11.208.0/200.11.208.1 to 0.11.223.2540.11.223.2554,094
1910.11.224.0/200.11.224.1 to 0.11.239.2540.11.239.2554,094
1920.11.240.0/200.11.240.1 to 0.11.255.2540.11.255.2554,094
1930.12.0.0/200.12.0.1 to 0.12.15.2540.12.15.2554,094
1940.12.16.0/200.12.16.1 to 0.12.31.2540.12.31.2554,094
1950.12.32.0/200.12.32.1 to 0.12.47.2540.12.47.2554,094
1960.12.48.0/200.12.48.1 to 0.12.63.2540.12.63.2554,094
1970.12.64.0/200.12.64.1 to 0.12.79.2540.12.79.2554,094
1980.12.80.0/200.12.80.1 to 0.12.95.2540.12.95.2554,094
1990.12.96.0/200.12.96.1 to 0.12.111.2540.12.111.2554,094
2000.12.112.0/200.12.112.1 to 0.12.127.2540.12.127.2554,094
2010.12.128.0/200.12.128.1 to 0.12.143.2540.12.143.2554,094
2020.12.144.0/200.12.144.1 to 0.12.159.2540.12.159.2554,094
2030.12.160.0/200.12.160.1 to 0.12.175.2540.12.175.2554,094
2040.12.176.0/200.12.176.1 to 0.12.191.2540.12.191.2554,094
2050.12.192.0/200.12.192.1 to 0.12.207.2540.12.207.2554,094
2060.12.208.0/200.12.208.1 to 0.12.223.2540.12.223.2554,094
2070.12.224.0/200.12.224.1 to 0.12.239.2540.12.239.2554,094
2080.12.240.0/200.12.240.1 to 0.12.255.2540.12.255.2554,094
2090.13.0.0/200.13.0.1 to 0.13.15.2540.13.15.2554,094
2100.13.16.0/200.13.16.1 to 0.13.31.2540.13.31.2554,094
2110.13.32.0/200.13.32.1 to 0.13.47.2540.13.47.2554,094
2120.13.48.0/200.13.48.1 to 0.13.63.2540.13.63.2554,094
2130.13.64.0/200.13.64.1 to 0.13.79.2540.13.79.2554,094
2140.13.80.0/200.13.80.1 to 0.13.95.2540.13.95.2554,094
2150.13.96.0/200.13.96.1 to 0.13.111.2540.13.111.2554,094
2160.13.112.0/200.13.112.1 to 0.13.127.2540.13.127.2554,094
2170.13.128.0/200.13.128.1 to 0.13.143.2540.13.143.2554,094
2180.13.144.0/200.13.144.1 to 0.13.159.2540.13.159.2554,094
2190.13.160.0/200.13.160.1 to 0.13.175.2540.13.175.2554,094
2200.13.176.0/200.13.176.1 to 0.13.191.2540.13.191.2554,094
2210.13.192.0/200.13.192.1 to 0.13.207.2540.13.207.2554,094
2220.13.208.0/200.13.208.1 to 0.13.223.2540.13.223.2554,094
2230.13.224.0/200.13.224.1 to 0.13.239.2540.13.239.2554,094
2240.13.240.0/200.13.240.1 to 0.13.255.2540.13.255.2554,094
2250.14.0.0/200.14.0.1 to 0.14.15.2540.14.15.2554,094
2260.14.16.0/200.14.16.1 to 0.14.31.2540.14.31.2554,094
2270.14.32.0/200.14.32.1 to 0.14.47.2540.14.47.2554,094
2280.14.48.0/200.14.48.1 to 0.14.63.2540.14.63.2554,094
2290.14.64.0/200.14.64.1 to 0.14.79.2540.14.79.2554,094
2300.14.80.0/200.14.80.1 to 0.14.95.2540.14.95.2554,094
2310.14.96.0/200.14.96.1 to 0.14.111.2540.14.111.2554,094
2320.14.112.0/200.14.112.1 to 0.14.127.2540.14.127.2554,094
2330.14.128.0/200.14.128.1 to 0.14.143.2540.14.143.2554,094
2340.14.144.0/200.14.144.1 to 0.14.159.2540.14.159.2554,094
2350.14.160.0/200.14.160.1 to 0.14.175.2540.14.175.2554,094
2360.14.176.0/200.14.176.1 to 0.14.191.2540.14.191.2554,094
2370.14.192.0/200.14.192.1 to 0.14.207.2540.14.207.2554,094
2380.14.208.0/200.14.208.1 to 0.14.223.2540.14.223.2554,094
2390.14.224.0/200.14.224.1 to 0.14.239.2540.14.239.2554,094
2400.14.240.0/200.14.240.1 to 0.14.255.2540.14.255.2554,094
2410.15.0.0/200.15.0.1 to 0.15.15.2540.15.15.2554,094
2420.15.16.0/200.15.16.1 to 0.15.31.2540.15.31.2554,094
2430.15.32.0/200.15.32.1 to 0.15.47.2540.15.47.2554,094
2440.15.48.0/200.15.48.1 to 0.15.63.2540.15.63.2554,094
2450.15.64.0/200.15.64.1 to 0.15.79.2540.15.79.2554,094
2460.15.80.0/200.15.80.1 to 0.15.95.2540.15.95.2554,094
2470.15.96.0/200.15.96.1 to 0.15.111.2540.15.111.2554,094
2480.15.112.0/200.15.112.1 to 0.15.127.2540.15.127.2554,094
2490.15.128.0/200.15.128.1 to 0.15.143.2540.15.143.2554,094
2500.15.144.0/200.15.144.1 to 0.15.159.2540.15.159.2554,094
2510.15.160.0/200.15.160.1 to 0.15.175.2540.15.175.2554,094
2520.15.176.0/200.15.176.1 to 0.15.191.2540.15.191.2554,094
2530.15.192.0/200.15.192.1 to 0.15.207.2540.15.207.2554,094
2540.15.208.0/200.15.208.1 to 0.15.223.2540.15.223.2554,094
2550.15.224.0/200.15.224.1 to 0.15.239.2540.15.239.2554,094
2560.15.240.0/200.15.240.1 to 0.15.255.2540.15.255.2554,094

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.