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.

Network7.192.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
7.192.0.0
Broadcast address
7.207.255.255
First usable
7.192.0.1
Last usable
7.207.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Public public
Old class
A (default /8)
As numbers
Hex 07C00000 · Integer 130023424 to 131071999
Reverse DNS zones
192.7.in-addr.arpa
193.7.in-addr.arpa
194.7.in-addr.arpa
195.7.in-addr.arpa
196.7.in-addr.arpa
197.7.in-addr.arpa
198.7.in-addr.arpa
199.7.in-addr.arpa
200.7.in-addr.arpa
201.7.in-addr.arpa
202.7.in-addr.arpa
203.7.in-addr.arpa
204.7.in-addr.arpa
205.7.in-addr.arpa
206.7.in-addr.arpa
207.7.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00000111.11000000.00000000.000000007.192.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network00000111.11000000.00000000.000000007.192.0.0
Broadcast00000111.11001111.11111111.111111117.207.255.255
Split into smaller subnets/21
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

7.192.0.0/12 makes 512 subnets of /21; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
17.192.0.0/217.192.0.1 to 7.192.7.2547.192.7.2552,046
27.192.8.0/217.192.8.1 to 7.192.15.2547.192.15.2552,046
37.192.16.0/217.192.16.1 to 7.192.23.2547.192.23.2552,046
47.192.24.0/217.192.24.1 to 7.192.31.2547.192.31.2552,046
57.192.32.0/217.192.32.1 to 7.192.39.2547.192.39.2552,046
67.192.40.0/217.192.40.1 to 7.192.47.2547.192.47.2552,046
77.192.48.0/217.192.48.1 to 7.192.55.2547.192.55.2552,046
87.192.56.0/217.192.56.1 to 7.192.63.2547.192.63.2552,046
97.192.64.0/217.192.64.1 to 7.192.71.2547.192.71.2552,046
107.192.72.0/217.192.72.1 to 7.192.79.2547.192.79.2552,046
117.192.80.0/217.192.80.1 to 7.192.87.2547.192.87.2552,046
127.192.88.0/217.192.88.1 to 7.192.95.2547.192.95.2552,046
137.192.96.0/217.192.96.1 to 7.192.103.2547.192.103.2552,046
147.192.104.0/217.192.104.1 to 7.192.111.2547.192.111.2552,046
157.192.112.0/217.192.112.1 to 7.192.119.2547.192.119.2552,046
167.192.120.0/217.192.120.1 to 7.192.127.2547.192.127.2552,046
177.192.128.0/217.192.128.1 to 7.192.135.2547.192.135.2552,046
187.192.136.0/217.192.136.1 to 7.192.143.2547.192.143.2552,046
197.192.144.0/217.192.144.1 to 7.192.151.2547.192.151.2552,046
207.192.152.0/217.192.152.1 to 7.192.159.2547.192.159.2552,046
217.192.160.0/217.192.160.1 to 7.192.167.2547.192.167.2552,046
227.192.168.0/217.192.168.1 to 7.192.175.2547.192.175.2552,046
237.192.176.0/217.192.176.1 to 7.192.183.2547.192.183.2552,046
247.192.184.0/217.192.184.1 to 7.192.191.2547.192.191.2552,046
257.192.192.0/217.192.192.1 to 7.192.199.2547.192.199.2552,046
267.192.200.0/217.192.200.1 to 7.192.207.2547.192.207.2552,046
277.192.208.0/217.192.208.1 to 7.192.215.2547.192.215.2552,046
287.192.216.0/217.192.216.1 to 7.192.223.2547.192.223.2552,046
297.192.224.0/217.192.224.1 to 7.192.231.2547.192.231.2552,046
307.192.232.0/217.192.232.1 to 7.192.239.2547.192.239.2552,046
317.192.240.0/217.192.240.1 to 7.192.247.2547.192.247.2552,046
327.192.248.0/217.192.248.1 to 7.192.255.2547.192.255.2552,046
337.193.0.0/217.193.0.1 to 7.193.7.2547.193.7.2552,046
347.193.8.0/217.193.8.1 to 7.193.15.2547.193.15.2552,046
357.193.16.0/217.193.16.1 to 7.193.23.2547.193.23.2552,046
367.193.24.0/217.193.24.1 to 7.193.31.2547.193.31.2552,046
377.193.32.0/217.193.32.1 to 7.193.39.2547.193.39.2552,046
387.193.40.0/217.193.40.1 to 7.193.47.2547.193.47.2552,046
397.193.48.0/217.193.48.1 to 7.193.55.2547.193.55.2552,046
407.193.56.0/217.193.56.1 to 7.193.63.2547.193.63.2552,046
417.193.64.0/217.193.64.1 to 7.193.71.2547.193.71.2552,046
427.193.72.0/217.193.72.1 to 7.193.79.2547.193.79.2552,046
437.193.80.0/217.193.80.1 to 7.193.87.2547.193.87.2552,046
447.193.88.0/217.193.88.1 to 7.193.95.2547.193.95.2552,046
457.193.96.0/217.193.96.1 to 7.193.103.2547.193.103.2552,046
467.193.104.0/217.193.104.1 to 7.193.111.2547.193.111.2552,046
477.193.112.0/217.193.112.1 to 7.193.119.2547.193.119.2552,046
487.193.120.0/217.193.120.1 to 7.193.127.2547.193.127.2552,046
497.193.128.0/217.193.128.1 to 7.193.135.2547.193.135.2552,046
507.193.136.0/217.193.136.1 to 7.193.143.2547.193.143.2552,046
517.193.144.0/217.193.144.1 to 7.193.151.2547.193.151.2552,046
527.193.152.0/217.193.152.1 to 7.193.159.2547.193.159.2552,046
537.193.160.0/217.193.160.1 to 7.193.167.2547.193.167.2552,046
547.193.168.0/217.193.168.1 to 7.193.175.2547.193.175.2552,046
557.193.176.0/217.193.176.1 to 7.193.183.2547.193.183.2552,046
567.193.184.0/217.193.184.1 to 7.193.191.2547.193.191.2552,046
577.193.192.0/217.193.192.1 to 7.193.199.2547.193.199.2552,046
587.193.200.0/217.193.200.1 to 7.193.207.2547.193.207.2552,046
597.193.208.0/217.193.208.1 to 7.193.215.2547.193.215.2552,046
607.193.216.0/217.193.216.1 to 7.193.223.2547.193.223.2552,046
617.193.224.0/217.193.224.1 to 7.193.231.2547.193.231.2552,046
627.193.232.0/217.193.232.1 to 7.193.239.2547.193.239.2552,046
637.193.240.0/217.193.240.1 to 7.193.247.2547.193.247.2552,046
647.193.248.0/217.193.248.1 to 7.193.255.2547.193.255.2552,046
657.194.0.0/217.194.0.1 to 7.194.7.2547.194.7.2552,046
667.194.8.0/217.194.8.1 to 7.194.15.2547.194.15.2552,046
677.194.16.0/217.194.16.1 to 7.194.23.2547.194.23.2552,046
687.194.24.0/217.194.24.1 to 7.194.31.2547.194.31.2552,046
697.194.32.0/217.194.32.1 to 7.194.39.2547.194.39.2552,046
707.194.40.0/217.194.40.1 to 7.194.47.2547.194.47.2552,046
717.194.48.0/217.194.48.1 to 7.194.55.2547.194.55.2552,046
727.194.56.0/217.194.56.1 to 7.194.63.2547.194.63.2552,046
737.194.64.0/217.194.64.1 to 7.194.71.2547.194.71.2552,046
747.194.72.0/217.194.72.1 to 7.194.79.2547.194.79.2552,046
757.194.80.0/217.194.80.1 to 7.194.87.2547.194.87.2552,046
767.194.88.0/217.194.88.1 to 7.194.95.2547.194.95.2552,046
777.194.96.0/217.194.96.1 to 7.194.103.2547.194.103.2552,046
787.194.104.0/217.194.104.1 to 7.194.111.2547.194.111.2552,046
797.194.112.0/217.194.112.1 to 7.194.119.2547.194.119.2552,046
807.194.120.0/217.194.120.1 to 7.194.127.2547.194.127.2552,046
817.194.128.0/217.194.128.1 to 7.194.135.2547.194.135.2552,046
827.194.136.0/217.194.136.1 to 7.194.143.2547.194.143.2552,046
837.194.144.0/217.194.144.1 to 7.194.151.2547.194.151.2552,046
847.194.152.0/217.194.152.1 to 7.194.159.2547.194.159.2552,046
857.194.160.0/217.194.160.1 to 7.194.167.2547.194.167.2552,046
867.194.168.0/217.194.168.1 to 7.194.175.2547.194.175.2552,046
877.194.176.0/217.194.176.1 to 7.194.183.2547.194.183.2552,046
887.194.184.0/217.194.184.1 to 7.194.191.2547.194.191.2552,046
897.194.192.0/217.194.192.1 to 7.194.199.2547.194.199.2552,046
907.194.200.0/217.194.200.1 to 7.194.207.2547.194.207.2552,046
917.194.208.0/217.194.208.1 to 7.194.215.2547.194.215.2552,046
927.194.216.0/217.194.216.1 to 7.194.223.2547.194.223.2552,046
937.194.224.0/217.194.224.1 to 7.194.231.2547.194.231.2552,046
947.194.232.0/217.194.232.1 to 7.194.239.2547.194.239.2552,046
957.194.240.0/217.194.240.1 to 7.194.247.2547.194.247.2552,046
967.194.248.0/217.194.248.1 to 7.194.255.2547.194.255.2552,046
977.195.0.0/217.195.0.1 to 7.195.7.2547.195.7.2552,046
987.195.8.0/217.195.8.1 to 7.195.15.2547.195.15.2552,046
997.195.16.0/217.195.16.1 to 7.195.23.2547.195.23.2552,046
1007.195.24.0/217.195.24.1 to 7.195.31.2547.195.31.2552,046
1017.195.32.0/217.195.32.1 to 7.195.39.2547.195.39.2552,046
1027.195.40.0/217.195.40.1 to 7.195.47.2547.195.47.2552,046
1037.195.48.0/217.195.48.1 to 7.195.55.2547.195.55.2552,046
1047.195.56.0/217.195.56.1 to 7.195.63.2547.195.63.2552,046
1057.195.64.0/217.195.64.1 to 7.195.71.2547.195.71.2552,046
1067.195.72.0/217.195.72.1 to 7.195.79.2547.195.79.2552,046
1077.195.80.0/217.195.80.1 to 7.195.87.2547.195.87.2552,046
1087.195.88.0/217.195.88.1 to 7.195.95.2547.195.95.2552,046
1097.195.96.0/217.195.96.1 to 7.195.103.2547.195.103.2552,046
1107.195.104.0/217.195.104.1 to 7.195.111.2547.195.111.2552,046
1117.195.112.0/217.195.112.1 to 7.195.119.2547.195.119.2552,046
1127.195.120.0/217.195.120.1 to 7.195.127.2547.195.127.2552,046
1137.195.128.0/217.195.128.1 to 7.195.135.2547.195.135.2552,046
1147.195.136.0/217.195.136.1 to 7.195.143.2547.195.143.2552,046
1157.195.144.0/217.195.144.1 to 7.195.151.2547.195.151.2552,046
1167.195.152.0/217.195.152.1 to 7.195.159.2547.195.159.2552,046
1177.195.160.0/217.195.160.1 to 7.195.167.2547.195.167.2552,046
1187.195.168.0/217.195.168.1 to 7.195.175.2547.195.175.2552,046
1197.195.176.0/217.195.176.1 to 7.195.183.2547.195.183.2552,046
1207.195.184.0/217.195.184.1 to 7.195.191.2547.195.191.2552,046
1217.195.192.0/217.195.192.1 to 7.195.199.2547.195.199.2552,046
1227.195.200.0/217.195.200.1 to 7.195.207.2547.195.207.2552,046
1237.195.208.0/217.195.208.1 to 7.195.215.2547.195.215.2552,046
1247.195.216.0/217.195.216.1 to 7.195.223.2547.195.223.2552,046
1257.195.224.0/217.195.224.1 to 7.195.231.2547.195.231.2552,046
1267.195.232.0/217.195.232.1 to 7.195.239.2547.195.239.2552,046
1277.195.240.0/217.195.240.1 to 7.195.247.2547.195.247.2552,046
1287.195.248.0/217.195.248.1 to 7.195.255.2547.195.255.2552,046
1297.196.0.0/217.196.0.1 to 7.196.7.2547.196.7.2552,046
1307.196.8.0/217.196.8.1 to 7.196.15.2547.196.15.2552,046
1317.196.16.0/217.196.16.1 to 7.196.23.2547.196.23.2552,046
1327.196.24.0/217.196.24.1 to 7.196.31.2547.196.31.2552,046
1337.196.32.0/217.196.32.1 to 7.196.39.2547.196.39.2552,046
1347.196.40.0/217.196.40.1 to 7.196.47.2547.196.47.2552,046
1357.196.48.0/217.196.48.1 to 7.196.55.2547.196.55.2552,046
1367.196.56.0/217.196.56.1 to 7.196.63.2547.196.63.2552,046
1377.196.64.0/217.196.64.1 to 7.196.71.2547.196.71.2552,046
1387.196.72.0/217.196.72.1 to 7.196.79.2547.196.79.2552,046
1397.196.80.0/217.196.80.1 to 7.196.87.2547.196.87.2552,046
1407.196.88.0/217.196.88.1 to 7.196.95.2547.196.95.2552,046
1417.196.96.0/217.196.96.1 to 7.196.103.2547.196.103.2552,046
1427.196.104.0/217.196.104.1 to 7.196.111.2547.196.111.2552,046
1437.196.112.0/217.196.112.1 to 7.196.119.2547.196.119.2552,046
1447.196.120.0/217.196.120.1 to 7.196.127.2547.196.127.2552,046
1457.196.128.0/217.196.128.1 to 7.196.135.2547.196.135.2552,046
1467.196.136.0/217.196.136.1 to 7.196.143.2547.196.143.2552,046
1477.196.144.0/217.196.144.1 to 7.196.151.2547.196.151.2552,046
1487.196.152.0/217.196.152.1 to 7.196.159.2547.196.159.2552,046
1497.196.160.0/217.196.160.1 to 7.196.167.2547.196.167.2552,046
1507.196.168.0/217.196.168.1 to 7.196.175.2547.196.175.2552,046
1517.196.176.0/217.196.176.1 to 7.196.183.2547.196.183.2552,046
1527.196.184.0/217.196.184.1 to 7.196.191.2547.196.191.2552,046
1537.196.192.0/217.196.192.1 to 7.196.199.2547.196.199.2552,046
1547.196.200.0/217.196.200.1 to 7.196.207.2547.196.207.2552,046
1557.196.208.0/217.196.208.1 to 7.196.215.2547.196.215.2552,046
1567.196.216.0/217.196.216.1 to 7.196.223.2547.196.223.2552,046
1577.196.224.0/217.196.224.1 to 7.196.231.2547.196.231.2552,046
1587.196.232.0/217.196.232.1 to 7.196.239.2547.196.239.2552,046
1597.196.240.0/217.196.240.1 to 7.196.247.2547.196.247.2552,046
1607.196.248.0/217.196.248.1 to 7.196.255.2547.196.255.2552,046
1617.197.0.0/217.197.0.1 to 7.197.7.2547.197.7.2552,046
1627.197.8.0/217.197.8.1 to 7.197.15.2547.197.15.2552,046
1637.197.16.0/217.197.16.1 to 7.197.23.2547.197.23.2552,046
1647.197.24.0/217.197.24.1 to 7.197.31.2547.197.31.2552,046
1657.197.32.0/217.197.32.1 to 7.197.39.2547.197.39.2552,046
1667.197.40.0/217.197.40.1 to 7.197.47.2547.197.47.2552,046
1677.197.48.0/217.197.48.1 to 7.197.55.2547.197.55.2552,046
1687.197.56.0/217.197.56.1 to 7.197.63.2547.197.63.2552,046
1697.197.64.0/217.197.64.1 to 7.197.71.2547.197.71.2552,046
1707.197.72.0/217.197.72.1 to 7.197.79.2547.197.79.2552,046
1717.197.80.0/217.197.80.1 to 7.197.87.2547.197.87.2552,046
1727.197.88.0/217.197.88.1 to 7.197.95.2547.197.95.2552,046
1737.197.96.0/217.197.96.1 to 7.197.103.2547.197.103.2552,046
1747.197.104.0/217.197.104.1 to 7.197.111.2547.197.111.2552,046
1757.197.112.0/217.197.112.1 to 7.197.119.2547.197.119.2552,046
1767.197.120.0/217.197.120.1 to 7.197.127.2547.197.127.2552,046
1777.197.128.0/217.197.128.1 to 7.197.135.2547.197.135.2552,046
1787.197.136.0/217.197.136.1 to 7.197.143.2547.197.143.2552,046
1797.197.144.0/217.197.144.1 to 7.197.151.2547.197.151.2552,046
1807.197.152.0/217.197.152.1 to 7.197.159.2547.197.159.2552,046
1817.197.160.0/217.197.160.1 to 7.197.167.2547.197.167.2552,046
1827.197.168.0/217.197.168.1 to 7.197.175.2547.197.175.2552,046
1837.197.176.0/217.197.176.1 to 7.197.183.2547.197.183.2552,046
1847.197.184.0/217.197.184.1 to 7.197.191.2547.197.191.2552,046
1857.197.192.0/217.197.192.1 to 7.197.199.2547.197.199.2552,046
1867.197.200.0/217.197.200.1 to 7.197.207.2547.197.207.2552,046
1877.197.208.0/217.197.208.1 to 7.197.215.2547.197.215.2552,046
1887.197.216.0/217.197.216.1 to 7.197.223.2547.197.223.2552,046
1897.197.224.0/217.197.224.1 to 7.197.231.2547.197.231.2552,046
1907.197.232.0/217.197.232.1 to 7.197.239.2547.197.239.2552,046
1917.197.240.0/217.197.240.1 to 7.197.247.2547.197.247.2552,046
1927.197.248.0/217.197.248.1 to 7.197.255.2547.197.255.2552,046
1937.198.0.0/217.198.0.1 to 7.198.7.2547.198.7.2552,046
1947.198.8.0/217.198.8.1 to 7.198.15.2547.198.15.2552,046
1957.198.16.0/217.198.16.1 to 7.198.23.2547.198.23.2552,046
1967.198.24.0/217.198.24.1 to 7.198.31.2547.198.31.2552,046
1977.198.32.0/217.198.32.1 to 7.198.39.2547.198.39.2552,046
1987.198.40.0/217.198.40.1 to 7.198.47.2547.198.47.2552,046
1997.198.48.0/217.198.48.1 to 7.198.55.2547.198.55.2552,046
2007.198.56.0/217.198.56.1 to 7.198.63.2547.198.63.2552,046
2017.198.64.0/217.198.64.1 to 7.198.71.2547.198.71.2552,046
2027.198.72.0/217.198.72.1 to 7.198.79.2547.198.79.2552,046
2037.198.80.0/217.198.80.1 to 7.198.87.2547.198.87.2552,046
2047.198.88.0/217.198.88.1 to 7.198.95.2547.198.95.2552,046
2057.198.96.0/217.198.96.1 to 7.198.103.2547.198.103.2552,046
2067.198.104.0/217.198.104.1 to 7.198.111.2547.198.111.2552,046
2077.198.112.0/217.198.112.1 to 7.198.119.2547.198.119.2552,046
2087.198.120.0/217.198.120.1 to 7.198.127.2547.198.127.2552,046
2097.198.128.0/217.198.128.1 to 7.198.135.2547.198.135.2552,046
2107.198.136.0/217.198.136.1 to 7.198.143.2547.198.143.2552,046
2117.198.144.0/217.198.144.1 to 7.198.151.2547.198.151.2552,046
2127.198.152.0/217.198.152.1 to 7.198.159.2547.198.159.2552,046
2137.198.160.0/217.198.160.1 to 7.198.167.2547.198.167.2552,046
2147.198.168.0/217.198.168.1 to 7.198.175.2547.198.175.2552,046
2157.198.176.0/217.198.176.1 to 7.198.183.2547.198.183.2552,046
2167.198.184.0/217.198.184.1 to 7.198.191.2547.198.191.2552,046
2177.198.192.0/217.198.192.1 to 7.198.199.2547.198.199.2552,046
2187.198.200.0/217.198.200.1 to 7.198.207.2547.198.207.2552,046
2197.198.208.0/217.198.208.1 to 7.198.215.2547.198.215.2552,046
2207.198.216.0/217.198.216.1 to 7.198.223.2547.198.223.2552,046
2217.198.224.0/217.198.224.1 to 7.198.231.2547.198.231.2552,046
2227.198.232.0/217.198.232.1 to 7.198.239.2547.198.239.2552,046
2237.198.240.0/217.198.240.1 to 7.198.247.2547.198.247.2552,046
2247.198.248.0/217.198.248.1 to 7.198.255.2547.198.255.2552,046
2257.199.0.0/217.199.0.1 to 7.199.7.2547.199.7.2552,046
2267.199.8.0/217.199.8.1 to 7.199.15.2547.199.15.2552,046
2277.199.16.0/217.199.16.1 to 7.199.23.2547.199.23.2552,046
2287.199.24.0/217.199.24.1 to 7.199.31.2547.199.31.2552,046
2297.199.32.0/217.199.32.1 to 7.199.39.2547.199.39.2552,046
2307.199.40.0/217.199.40.1 to 7.199.47.2547.199.47.2552,046
2317.199.48.0/217.199.48.1 to 7.199.55.2547.199.55.2552,046
2327.199.56.0/217.199.56.1 to 7.199.63.2547.199.63.2552,046
2337.199.64.0/217.199.64.1 to 7.199.71.2547.199.71.2552,046
2347.199.72.0/217.199.72.1 to 7.199.79.2547.199.79.2552,046
2357.199.80.0/217.199.80.1 to 7.199.87.2547.199.87.2552,046
2367.199.88.0/217.199.88.1 to 7.199.95.2547.199.95.2552,046
2377.199.96.0/217.199.96.1 to 7.199.103.2547.199.103.2552,046
2387.199.104.0/217.199.104.1 to 7.199.111.2547.199.111.2552,046
2397.199.112.0/217.199.112.1 to 7.199.119.2547.199.119.2552,046
2407.199.120.0/217.199.120.1 to 7.199.127.2547.199.127.2552,046
2417.199.128.0/217.199.128.1 to 7.199.135.2547.199.135.2552,046
2427.199.136.0/217.199.136.1 to 7.199.143.2547.199.143.2552,046
2437.199.144.0/217.199.144.1 to 7.199.151.2547.199.151.2552,046
2447.199.152.0/217.199.152.1 to 7.199.159.2547.199.159.2552,046
2457.199.160.0/217.199.160.1 to 7.199.167.2547.199.167.2552,046
2467.199.168.0/217.199.168.1 to 7.199.175.2547.199.175.2552,046
2477.199.176.0/217.199.176.1 to 7.199.183.2547.199.183.2552,046
2487.199.184.0/217.199.184.1 to 7.199.191.2547.199.191.2552,046
2497.199.192.0/217.199.192.1 to 7.199.199.2547.199.199.2552,046
2507.199.200.0/217.199.200.1 to 7.199.207.2547.199.207.2552,046
2517.199.208.0/217.199.208.1 to 7.199.215.2547.199.215.2552,046
2527.199.216.0/217.199.216.1 to 7.199.223.2547.199.223.2552,046
2537.199.224.0/217.199.224.1 to 7.199.231.2547.199.231.2552,046
2547.199.232.0/217.199.232.1 to 7.199.239.2547.199.239.2552,046
2557.199.240.0/217.199.240.1 to 7.199.247.2547.199.247.2552,046
2567.199.248.0/217.199.248.1 to 7.199.255.2547.199.255.2552,046

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.