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.

Network8.192.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
8.192.0.0
Broadcast address
8.199.255.255
First usable
8.192.0.1
Last usable
8.199.255.254
Usable hosts
524,286 (524,288 less the network and broadcast addresses)
Subnet mask
255.248.0.0
Wildcard mask
0.7.255.255 (Cisco ACLs, OSPF)
Prefix length
/13
Type
Public public
Old class
A (default /8)
As numbers
Hex 08C00000 · Integer 146800640 to 147324927
Reverse DNS zones
192.8.in-addr.arpa
193.8.in-addr.arpa
194.8.in-addr.arpa
195.8.in-addr.arpa
196.8.in-addr.arpa
197.8.in-addr.arpa
198.8.in-addr.arpa
199.8.in-addr.arpa
/13 is not on a 8-bit boundary, so it takes 8 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00001000.11000000.00000000.000000008.192.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network00001000.11000000.00000000.000000008.192.0.0
Broadcast00001000.11000111.11111111.111111118.199.255.255
Split into smaller subnets/24
/14 (2)/15 (4)/16 (8)/17 (16)/18 (32)/19 (64)/20 (128)/21 (256)/22 (512)/23 (1,024)/24 (2,048)/25 (4,096)

8.192.0.0/13 makes 2,048 subnets of /24; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
18.192.0.0/248.192.0.1 to 8.192.0.2548.192.0.255254
28.192.1.0/248.192.1.1 to 8.192.1.2548.192.1.255254
38.192.2.0/248.192.2.1 to 8.192.2.2548.192.2.255254
48.192.3.0/248.192.3.1 to 8.192.3.2548.192.3.255254
58.192.4.0/248.192.4.1 to 8.192.4.2548.192.4.255254
68.192.5.0/248.192.5.1 to 8.192.5.2548.192.5.255254
78.192.6.0/248.192.6.1 to 8.192.6.2548.192.6.255254
88.192.7.0/248.192.7.1 to 8.192.7.2548.192.7.255254
98.192.8.0/248.192.8.1 to 8.192.8.2548.192.8.255254
108.192.9.0/248.192.9.1 to 8.192.9.2548.192.9.255254
118.192.10.0/248.192.10.1 to 8.192.10.2548.192.10.255254
128.192.11.0/248.192.11.1 to 8.192.11.2548.192.11.255254
138.192.12.0/248.192.12.1 to 8.192.12.2548.192.12.255254
148.192.13.0/248.192.13.1 to 8.192.13.2548.192.13.255254
158.192.14.0/248.192.14.1 to 8.192.14.2548.192.14.255254
168.192.15.0/248.192.15.1 to 8.192.15.2548.192.15.255254
178.192.16.0/248.192.16.1 to 8.192.16.2548.192.16.255254
188.192.17.0/248.192.17.1 to 8.192.17.2548.192.17.255254
198.192.18.0/248.192.18.1 to 8.192.18.2548.192.18.255254
208.192.19.0/248.192.19.1 to 8.192.19.2548.192.19.255254
218.192.20.0/248.192.20.1 to 8.192.20.2548.192.20.255254
228.192.21.0/248.192.21.1 to 8.192.21.2548.192.21.255254
238.192.22.0/248.192.22.1 to 8.192.22.2548.192.22.255254
248.192.23.0/248.192.23.1 to 8.192.23.2548.192.23.255254
258.192.24.0/248.192.24.1 to 8.192.24.2548.192.24.255254
268.192.25.0/248.192.25.1 to 8.192.25.2548.192.25.255254
278.192.26.0/248.192.26.1 to 8.192.26.2548.192.26.255254
288.192.27.0/248.192.27.1 to 8.192.27.2548.192.27.255254
298.192.28.0/248.192.28.1 to 8.192.28.2548.192.28.255254
308.192.29.0/248.192.29.1 to 8.192.29.2548.192.29.255254
318.192.30.0/248.192.30.1 to 8.192.30.2548.192.30.255254
328.192.31.0/248.192.31.1 to 8.192.31.2548.192.31.255254
338.192.32.0/248.192.32.1 to 8.192.32.2548.192.32.255254
348.192.33.0/248.192.33.1 to 8.192.33.2548.192.33.255254
358.192.34.0/248.192.34.1 to 8.192.34.2548.192.34.255254
368.192.35.0/248.192.35.1 to 8.192.35.2548.192.35.255254
378.192.36.0/248.192.36.1 to 8.192.36.2548.192.36.255254
388.192.37.0/248.192.37.1 to 8.192.37.2548.192.37.255254
398.192.38.0/248.192.38.1 to 8.192.38.2548.192.38.255254
408.192.39.0/248.192.39.1 to 8.192.39.2548.192.39.255254
418.192.40.0/248.192.40.1 to 8.192.40.2548.192.40.255254
428.192.41.0/248.192.41.1 to 8.192.41.2548.192.41.255254
438.192.42.0/248.192.42.1 to 8.192.42.2548.192.42.255254
448.192.43.0/248.192.43.1 to 8.192.43.2548.192.43.255254
458.192.44.0/248.192.44.1 to 8.192.44.2548.192.44.255254
468.192.45.0/248.192.45.1 to 8.192.45.2548.192.45.255254
478.192.46.0/248.192.46.1 to 8.192.46.2548.192.46.255254
488.192.47.0/248.192.47.1 to 8.192.47.2548.192.47.255254
498.192.48.0/248.192.48.1 to 8.192.48.2548.192.48.255254
508.192.49.0/248.192.49.1 to 8.192.49.2548.192.49.255254
518.192.50.0/248.192.50.1 to 8.192.50.2548.192.50.255254
528.192.51.0/248.192.51.1 to 8.192.51.2548.192.51.255254
538.192.52.0/248.192.52.1 to 8.192.52.2548.192.52.255254
548.192.53.0/248.192.53.1 to 8.192.53.2548.192.53.255254
558.192.54.0/248.192.54.1 to 8.192.54.2548.192.54.255254
568.192.55.0/248.192.55.1 to 8.192.55.2548.192.55.255254
578.192.56.0/248.192.56.1 to 8.192.56.2548.192.56.255254
588.192.57.0/248.192.57.1 to 8.192.57.2548.192.57.255254
598.192.58.0/248.192.58.1 to 8.192.58.2548.192.58.255254
608.192.59.0/248.192.59.1 to 8.192.59.2548.192.59.255254
618.192.60.0/248.192.60.1 to 8.192.60.2548.192.60.255254
628.192.61.0/248.192.61.1 to 8.192.61.2548.192.61.255254
638.192.62.0/248.192.62.1 to 8.192.62.2548.192.62.255254
648.192.63.0/248.192.63.1 to 8.192.63.2548.192.63.255254
658.192.64.0/248.192.64.1 to 8.192.64.2548.192.64.255254
668.192.65.0/248.192.65.1 to 8.192.65.2548.192.65.255254
678.192.66.0/248.192.66.1 to 8.192.66.2548.192.66.255254
688.192.67.0/248.192.67.1 to 8.192.67.2548.192.67.255254
698.192.68.0/248.192.68.1 to 8.192.68.2548.192.68.255254
708.192.69.0/248.192.69.1 to 8.192.69.2548.192.69.255254
718.192.70.0/248.192.70.1 to 8.192.70.2548.192.70.255254
728.192.71.0/248.192.71.1 to 8.192.71.2548.192.71.255254
738.192.72.0/248.192.72.1 to 8.192.72.2548.192.72.255254
748.192.73.0/248.192.73.1 to 8.192.73.2548.192.73.255254
758.192.74.0/248.192.74.1 to 8.192.74.2548.192.74.255254
768.192.75.0/248.192.75.1 to 8.192.75.2548.192.75.255254
778.192.76.0/248.192.76.1 to 8.192.76.2548.192.76.255254
788.192.77.0/248.192.77.1 to 8.192.77.2548.192.77.255254
798.192.78.0/248.192.78.1 to 8.192.78.2548.192.78.255254
808.192.79.0/248.192.79.1 to 8.192.79.2548.192.79.255254
818.192.80.0/248.192.80.1 to 8.192.80.2548.192.80.255254
828.192.81.0/248.192.81.1 to 8.192.81.2548.192.81.255254
838.192.82.0/248.192.82.1 to 8.192.82.2548.192.82.255254
848.192.83.0/248.192.83.1 to 8.192.83.2548.192.83.255254
858.192.84.0/248.192.84.1 to 8.192.84.2548.192.84.255254
868.192.85.0/248.192.85.1 to 8.192.85.2548.192.85.255254
878.192.86.0/248.192.86.1 to 8.192.86.2548.192.86.255254
888.192.87.0/248.192.87.1 to 8.192.87.2548.192.87.255254
898.192.88.0/248.192.88.1 to 8.192.88.2548.192.88.255254
908.192.89.0/248.192.89.1 to 8.192.89.2548.192.89.255254
918.192.90.0/248.192.90.1 to 8.192.90.2548.192.90.255254
928.192.91.0/248.192.91.1 to 8.192.91.2548.192.91.255254
938.192.92.0/248.192.92.1 to 8.192.92.2548.192.92.255254
948.192.93.0/248.192.93.1 to 8.192.93.2548.192.93.255254
958.192.94.0/248.192.94.1 to 8.192.94.2548.192.94.255254
968.192.95.0/248.192.95.1 to 8.192.95.2548.192.95.255254
978.192.96.0/248.192.96.1 to 8.192.96.2548.192.96.255254
988.192.97.0/248.192.97.1 to 8.192.97.2548.192.97.255254
998.192.98.0/248.192.98.1 to 8.192.98.2548.192.98.255254
1008.192.99.0/248.192.99.1 to 8.192.99.2548.192.99.255254
1018.192.100.0/248.192.100.1 to 8.192.100.2548.192.100.255254
1028.192.101.0/248.192.101.1 to 8.192.101.2548.192.101.255254
1038.192.102.0/248.192.102.1 to 8.192.102.2548.192.102.255254
1048.192.103.0/248.192.103.1 to 8.192.103.2548.192.103.255254
1058.192.104.0/248.192.104.1 to 8.192.104.2548.192.104.255254
1068.192.105.0/248.192.105.1 to 8.192.105.2548.192.105.255254
1078.192.106.0/248.192.106.1 to 8.192.106.2548.192.106.255254
1088.192.107.0/248.192.107.1 to 8.192.107.2548.192.107.255254
1098.192.108.0/248.192.108.1 to 8.192.108.2548.192.108.255254
1108.192.109.0/248.192.109.1 to 8.192.109.2548.192.109.255254
1118.192.110.0/248.192.110.1 to 8.192.110.2548.192.110.255254
1128.192.111.0/248.192.111.1 to 8.192.111.2548.192.111.255254
1138.192.112.0/248.192.112.1 to 8.192.112.2548.192.112.255254
1148.192.113.0/248.192.113.1 to 8.192.113.2548.192.113.255254
1158.192.114.0/248.192.114.1 to 8.192.114.2548.192.114.255254
1168.192.115.0/248.192.115.1 to 8.192.115.2548.192.115.255254
1178.192.116.0/248.192.116.1 to 8.192.116.2548.192.116.255254
1188.192.117.0/248.192.117.1 to 8.192.117.2548.192.117.255254
1198.192.118.0/248.192.118.1 to 8.192.118.2548.192.118.255254
1208.192.119.0/248.192.119.1 to 8.192.119.2548.192.119.255254
1218.192.120.0/248.192.120.1 to 8.192.120.2548.192.120.255254
1228.192.121.0/248.192.121.1 to 8.192.121.2548.192.121.255254
1238.192.122.0/248.192.122.1 to 8.192.122.2548.192.122.255254
1248.192.123.0/248.192.123.1 to 8.192.123.2548.192.123.255254
1258.192.124.0/248.192.124.1 to 8.192.124.2548.192.124.255254
1268.192.125.0/248.192.125.1 to 8.192.125.2548.192.125.255254
1278.192.126.0/248.192.126.1 to 8.192.126.2548.192.126.255254
1288.192.127.0/248.192.127.1 to 8.192.127.2548.192.127.255254
1298.192.128.0/248.192.128.1 to 8.192.128.2548.192.128.255254
1308.192.129.0/248.192.129.1 to 8.192.129.2548.192.129.255254
1318.192.130.0/248.192.130.1 to 8.192.130.2548.192.130.255254
1328.192.131.0/248.192.131.1 to 8.192.131.2548.192.131.255254
1338.192.132.0/248.192.132.1 to 8.192.132.2548.192.132.255254
1348.192.133.0/248.192.133.1 to 8.192.133.2548.192.133.255254
1358.192.134.0/248.192.134.1 to 8.192.134.2548.192.134.255254
1368.192.135.0/248.192.135.1 to 8.192.135.2548.192.135.255254
1378.192.136.0/248.192.136.1 to 8.192.136.2548.192.136.255254
1388.192.137.0/248.192.137.1 to 8.192.137.2548.192.137.255254
1398.192.138.0/248.192.138.1 to 8.192.138.2548.192.138.255254
1408.192.139.0/248.192.139.1 to 8.192.139.2548.192.139.255254
1418.192.140.0/248.192.140.1 to 8.192.140.2548.192.140.255254
1428.192.141.0/248.192.141.1 to 8.192.141.2548.192.141.255254
1438.192.142.0/248.192.142.1 to 8.192.142.2548.192.142.255254
1448.192.143.0/248.192.143.1 to 8.192.143.2548.192.143.255254
1458.192.144.0/248.192.144.1 to 8.192.144.2548.192.144.255254
1468.192.145.0/248.192.145.1 to 8.192.145.2548.192.145.255254
1478.192.146.0/248.192.146.1 to 8.192.146.2548.192.146.255254
1488.192.147.0/248.192.147.1 to 8.192.147.2548.192.147.255254
1498.192.148.0/248.192.148.1 to 8.192.148.2548.192.148.255254
1508.192.149.0/248.192.149.1 to 8.192.149.2548.192.149.255254
1518.192.150.0/248.192.150.1 to 8.192.150.2548.192.150.255254
1528.192.151.0/248.192.151.1 to 8.192.151.2548.192.151.255254
1538.192.152.0/248.192.152.1 to 8.192.152.2548.192.152.255254
1548.192.153.0/248.192.153.1 to 8.192.153.2548.192.153.255254
1558.192.154.0/248.192.154.1 to 8.192.154.2548.192.154.255254
1568.192.155.0/248.192.155.1 to 8.192.155.2548.192.155.255254
1578.192.156.0/248.192.156.1 to 8.192.156.2548.192.156.255254
1588.192.157.0/248.192.157.1 to 8.192.157.2548.192.157.255254
1598.192.158.0/248.192.158.1 to 8.192.158.2548.192.158.255254
1608.192.159.0/248.192.159.1 to 8.192.159.2548.192.159.255254
1618.192.160.0/248.192.160.1 to 8.192.160.2548.192.160.255254
1628.192.161.0/248.192.161.1 to 8.192.161.2548.192.161.255254
1638.192.162.0/248.192.162.1 to 8.192.162.2548.192.162.255254
1648.192.163.0/248.192.163.1 to 8.192.163.2548.192.163.255254
1658.192.164.0/248.192.164.1 to 8.192.164.2548.192.164.255254
1668.192.165.0/248.192.165.1 to 8.192.165.2548.192.165.255254
1678.192.166.0/248.192.166.1 to 8.192.166.2548.192.166.255254
1688.192.167.0/248.192.167.1 to 8.192.167.2548.192.167.255254
1698.192.168.0/248.192.168.1 to 8.192.168.2548.192.168.255254
1708.192.169.0/248.192.169.1 to 8.192.169.2548.192.169.255254
1718.192.170.0/248.192.170.1 to 8.192.170.2548.192.170.255254
1728.192.171.0/248.192.171.1 to 8.192.171.2548.192.171.255254
1738.192.172.0/248.192.172.1 to 8.192.172.2548.192.172.255254
1748.192.173.0/248.192.173.1 to 8.192.173.2548.192.173.255254
1758.192.174.0/248.192.174.1 to 8.192.174.2548.192.174.255254
1768.192.175.0/248.192.175.1 to 8.192.175.2548.192.175.255254
1778.192.176.0/248.192.176.1 to 8.192.176.2548.192.176.255254
1788.192.177.0/248.192.177.1 to 8.192.177.2548.192.177.255254
1798.192.178.0/248.192.178.1 to 8.192.178.2548.192.178.255254
1808.192.179.0/248.192.179.1 to 8.192.179.2548.192.179.255254
1818.192.180.0/248.192.180.1 to 8.192.180.2548.192.180.255254
1828.192.181.0/248.192.181.1 to 8.192.181.2548.192.181.255254
1838.192.182.0/248.192.182.1 to 8.192.182.2548.192.182.255254
1848.192.183.0/248.192.183.1 to 8.192.183.2548.192.183.255254
1858.192.184.0/248.192.184.1 to 8.192.184.2548.192.184.255254
1868.192.185.0/248.192.185.1 to 8.192.185.2548.192.185.255254
1878.192.186.0/248.192.186.1 to 8.192.186.2548.192.186.255254
1888.192.187.0/248.192.187.1 to 8.192.187.2548.192.187.255254
1898.192.188.0/248.192.188.1 to 8.192.188.2548.192.188.255254
1908.192.189.0/248.192.189.1 to 8.192.189.2548.192.189.255254
1918.192.190.0/248.192.190.1 to 8.192.190.2548.192.190.255254
1928.192.191.0/248.192.191.1 to 8.192.191.2548.192.191.255254
1938.192.192.0/248.192.192.1 to 8.192.192.2548.192.192.255254
1948.192.193.0/248.192.193.1 to 8.192.193.2548.192.193.255254
1958.192.194.0/248.192.194.1 to 8.192.194.2548.192.194.255254
1968.192.195.0/248.192.195.1 to 8.192.195.2548.192.195.255254
1978.192.196.0/248.192.196.1 to 8.192.196.2548.192.196.255254
1988.192.197.0/248.192.197.1 to 8.192.197.2548.192.197.255254
1998.192.198.0/248.192.198.1 to 8.192.198.2548.192.198.255254
2008.192.199.0/248.192.199.1 to 8.192.199.2548.192.199.255254
2018.192.200.0/248.192.200.1 to 8.192.200.2548.192.200.255254
2028.192.201.0/248.192.201.1 to 8.192.201.2548.192.201.255254
2038.192.202.0/248.192.202.1 to 8.192.202.2548.192.202.255254
2048.192.203.0/248.192.203.1 to 8.192.203.2548.192.203.255254
2058.192.204.0/248.192.204.1 to 8.192.204.2548.192.204.255254
2068.192.205.0/248.192.205.1 to 8.192.205.2548.192.205.255254
2078.192.206.0/248.192.206.1 to 8.192.206.2548.192.206.255254
2088.192.207.0/248.192.207.1 to 8.192.207.2548.192.207.255254
2098.192.208.0/248.192.208.1 to 8.192.208.2548.192.208.255254
2108.192.209.0/248.192.209.1 to 8.192.209.2548.192.209.255254
2118.192.210.0/248.192.210.1 to 8.192.210.2548.192.210.255254
2128.192.211.0/248.192.211.1 to 8.192.211.2548.192.211.255254
2138.192.212.0/248.192.212.1 to 8.192.212.2548.192.212.255254
2148.192.213.0/248.192.213.1 to 8.192.213.2548.192.213.255254
2158.192.214.0/248.192.214.1 to 8.192.214.2548.192.214.255254
2168.192.215.0/248.192.215.1 to 8.192.215.2548.192.215.255254
2178.192.216.0/248.192.216.1 to 8.192.216.2548.192.216.255254
2188.192.217.0/248.192.217.1 to 8.192.217.2548.192.217.255254
2198.192.218.0/248.192.218.1 to 8.192.218.2548.192.218.255254
2208.192.219.0/248.192.219.1 to 8.192.219.2548.192.219.255254
2218.192.220.0/248.192.220.1 to 8.192.220.2548.192.220.255254
2228.192.221.0/248.192.221.1 to 8.192.221.2548.192.221.255254
2238.192.222.0/248.192.222.1 to 8.192.222.2548.192.222.255254
2248.192.223.0/248.192.223.1 to 8.192.223.2548.192.223.255254
2258.192.224.0/248.192.224.1 to 8.192.224.2548.192.224.255254
2268.192.225.0/248.192.225.1 to 8.192.225.2548.192.225.255254
2278.192.226.0/248.192.226.1 to 8.192.226.2548.192.226.255254
2288.192.227.0/248.192.227.1 to 8.192.227.2548.192.227.255254
2298.192.228.0/248.192.228.1 to 8.192.228.2548.192.228.255254
2308.192.229.0/248.192.229.1 to 8.192.229.2548.192.229.255254
2318.192.230.0/248.192.230.1 to 8.192.230.2548.192.230.255254
2328.192.231.0/248.192.231.1 to 8.192.231.2548.192.231.255254
2338.192.232.0/248.192.232.1 to 8.192.232.2548.192.232.255254
2348.192.233.0/248.192.233.1 to 8.192.233.2548.192.233.255254
2358.192.234.0/248.192.234.1 to 8.192.234.2548.192.234.255254
2368.192.235.0/248.192.235.1 to 8.192.235.2548.192.235.255254
2378.192.236.0/248.192.236.1 to 8.192.236.2548.192.236.255254
2388.192.237.0/248.192.237.1 to 8.192.237.2548.192.237.255254
2398.192.238.0/248.192.238.1 to 8.192.238.2548.192.238.255254
2408.192.239.0/248.192.239.1 to 8.192.239.2548.192.239.255254
2418.192.240.0/248.192.240.1 to 8.192.240.2548.192.240.255254
2428.192.241.0/248.192.241.1 to 8.192.241.2548.192.241.255254
2438.192.242.0/248.192.242.1 to 8.192.242.2548.192.242.255254
2448.192.243.0/248.192.243.1 to 8.192.243.2548.192.243.255254
2458.192.244.0/248.192.244.1 to 8.192.244.2548.192.244.255254
2468.192.245.0/248.192.245.1 to 8.192.245.2548.192.245.255254
2478.192.246.0/248.192.246.1 to 8.192.246.2548.192.246.255254
2488.192.247.0/248.192.247.1 to 8.192.247.2548.192.247.255254
2498.192.248.0/248.192.248.1 to 8.192.248.2548.192.248.255254
2508.192.249.0/248.192.249.1 to 8.192.249.2548.192.249.255254
2518.192.250.0/248.192.250.1 to 8.192.250.2548.192.250.255254
2528.192.251.0/248.192.251.1 to 8.192.251.2548.192.251.255254
2538.192.252.0/248.192.252.1 to 8.192.252.2548.192.252.255254
2548.192.253.0/248.192.253.1 to 8.192.253.2548.192.253.255254
2558.192.254.0/248.192.254.1 to 8.192.254.2548.192.254.255254
2568.192.255.0/248.192.255.1 to 8.192.255.2548.192.255.255254

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.