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.

Network8.6.64.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
8.6.64.0
Broadcast address
8.6.127.255
First usable
8.6.64.1
Last usable
8.6.127.254
Usable hosts
16,382 (16,384 less the network and broadcast addresses)
Subnet mask
255.255.192.0
Wildcard mask
0.0.63.255 (Cisco ACLs, OSPF)
Prefix length
/18
Type
Public public
Old class
A (default /8)
As numbers
Hex 08064000 · Integer 134627328 to 134643711
Reverse DNS zones
64.6.8.in-addr.arpa
65.6.8.in-addr.arpa
66.6.8.in-addr.arpa
67.6.8.in-addr.arpa
68.6.8.in-addr.arpa
69.6.8.in-addr.arpa
70.6.8.in-addr.arpa
71.6.8.in-addr.arpa
72.6.8.in-addr.arpa
73.6.8.in-addr.arpa
74.6.8.in-addr.arpa
75.6.8.in-addr.arpa
76.6.8.in-addr.arpa
77.6.8.in-addr.arpa
78.6.8.in-addr.arpa
79.6.8.in-addr.arpa
and 48 more
/18 is not on a 8-bit boundary, so it takes 64 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00001000.00000110.01000000.000000008.6.64.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network00001000.00000110.01000000.000000008.6.64.0
Broadcast00001000.00000110.01111111.111111118.6.127.255
Split into smaller subnets/30
/19 (2)/20 (4)/21 (8)/22 (16)/23 (32)/24 (64)/25 (128)/26 (256)/27 (512)/28 (1,024)/29 (2,048)/30 (4,096)

8.6.64.0/18 makes 4,096 subnets of /30; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
18.6.64.0/308.6.64.1 to 8.6.64.28.6.64.32
28.6.64.4/308.6.64.5 to 8.6.64.68.6.64.72
38.6.64.8/308.6.64.9 to 8.6.64.108.6.64.112
48.6.64.12/308.6.64.13 to 8.6.64.148.6.64.152
58.6.64.16/308.6.64.17 to 8.6.64.188.6.64.192
68.6.64.20/308.6.64.21 to 8.6.64.228.6.64.232
78.6.64.24/308.6.64.25 to 8.6.64.268.6.64.272
88.6.64.28/308.6.64.29 to 8.6.64.308.6.64.312
98.6.64.32/308.6.64.33 to 8.6.64.348.6.64.352
108.6.64.36/308.6.64.37 to 8.6.64.388.6.64.392
118.6.64.40/308.6.64.41 to 8.6.64.428.6.64.432
128.6.64.44/308.6.64.45 to 8.6.64.468.6.64.472
138.6.64.48/308.6.64.49 to 8.6.64.508.6.64.512
148.6.64.52/308.6.64.53 to 8.6.64.548.6.64.552
158.6.64.56/308.6.64.57 to 8.6.64.588.6.64.592
168.6.64.60/308.6.64.61 to 8.6.64.628.6.64.632
178.6.64.64/308.6.64.65 to 8.6.64.668.6.64.672
188.6.64.68/308.6.64.69 to 8.6.64.708.6.64.712
198.6.64.72/308.6.64.73 to 8.6.64.748.6.64.752
208.6.64.76/308.6.64.77 to 8.6.64.788.6.64.792
218.6.64.80/308.6.64.81 to 8.6.64.828.6.64.832
228.6.64.84/308.6.64.85 to 8.6.64.868.6.64.872
238.6.64.88/308.6.64.89 to 8.6.64.908.6.64.912
248.6.64.92/308.6.64.93 to 8.6.64.948.6.64.952
258.6.64.96/308.6.64.97 to 8.6.64.988.6.64.992
268.6.64.100/308.6.64.101 to 8.6.64.1028.6.64.1032
278.6.64.104/308.6.64.105 to 8.6.64.1068.6.64.1072
288.6.64.108/308.6.64.109 to 8.6.64.1108.6.64.1112
298.6.64.112/308.6.64.113 to 8.6.64.1148.6.64.1152
308.6.64.116/308.6.64.117 to 8.6.64.1188.6.64.1192
318.6.64.120/308.6.64.121 to 8.6.64.1228.6.64.1232
328.6.64.124/308.6.64.125 to 8.6.64.1268.6.64.1272
338.6.64.128/308.6.64.129 to 8.6.64.1308.6.64.1312
348.6.64.132/308.6.64.133 to 8.6.64.1348.6.64.1352
358.6.64.136/308.6.64.137 to 8.6.64.1388.6.64.1392
368.6.64.140/308.6.64.141 to 8.6.64.1428.6.64.1432
378.6.64.144/308.6.64.145 to 8.6.64.1468.6.64.1472
388.6.64.148/308.6.64.149 to 8.6.64.1508.6.64.1512
398.6.64.152/308.6.64.153 to 8.6.64.1548.6.64.1552
408.6.64.156/308.6.64.157 to 8.6.64.1588.6.64.1592
418.6.64.160/308.6.64.161 to 8.6.64.1628.6.64.1632
428.6.64.164/308.6.64.165 to 8.6.64.1668.6.64.1672
438.6.64.168/308.6.64.169 to 8.6.64.1708.6.64.1712
448.6.64.172/308.6.64.173 to 8.6.64.1748.6.64.1752
458.6.64.176/308.6.64.177 to 8.6.64.1788.6.64.1792
468.6.64.180/308.6.64.181 to 8.6.64.1828.6.64.1832
478.6.64.184/308.6.64.185 to 8.6.64.1868.6.64.1872
488.6.64.188/308.6.64.189 to 8.6.64.1908.6.64.1912
498.6.64.192/308.6.64.193 to 8.6.64.1948.6.64.1952
508.6.64.196/308.6.64.197 to 8.6.64.1988.6.64.1992
518.6.64.200/308.6.64.201 to 8.6.64.2028.6.64.2032
528.6.64.204/308.6.64.205 to 8.6.64.2068.6.64.2072
538.6.64.208/308.6.64.209 to 8.6.64.2108.6.64.2112
548.6.64.212/308.6.64.213 to 8.6.64.2148.6.64.2152
558.6.64.216/308.6.64.217 to 8.6.64.2188.6.64.2192
568.6.64.220/308.6.64.221 to 8.6.64.2228.6.64.2232
578.6.64.224/308.6.64.225 to 8.6.64.2268.6.64.2272
588.6.64.228/308.6.64.229 to 8.6.64.2308.6.64.2312
598.6.64.232/308.6.64.233 to 8.6.64.2348.6.64.2352
608.6.64.236/308.6.64.237 to 8.6.64.2388.6.64.2392
618.6.64.240/308.6.64.241 to 8.6.64.2428.6.64.2432
628.6.64.244/308.6.64.245 to 8.6.64.2468.6.64.2472
638.6.64.248/308.6.64.249 to 8.6.64.2508.6.64.2512
648.6.64.252/308.6.64.253 to 8.6.64.2548.6.64.2552
658.6.65.0/308.6.65.1 to 8.6.65.28.6.65.32
668.6.65.4/308.6.65.5 to 8.6.65.68.6.65.72
678.6.65.8/308.6.65.9 to 8.6.65.108.6.65.112
688.6.65.12/308.6.65.13 to 8.6.65.148.6.65.152
698.6.65.16/308.6.65.17 to 8.6.65.188.6.65.192
708.6.65.20/308.6.65.21 to 8.6.65.228.6.65.232
718.6.65.24/308.6.65.25 to 8.6.65.268.6.65.272
728.6.65.28/308.6.65.29 to 8.6.65.308.6.65.312
738.6.65.32/308.6.65.33 to 8.6.65.348.6.65.352
748.6.65.36/308.6.65.37 to 8.6.65.388.6.65.392
758.6.65.40/308.6.65.41 to 8.6.65.428.6.65.432
768.6.65.44/308.6.65.45 to 8.6.65.468.6.65.472
778.6.65.48/308.6.65.49 to 8.6.65.508.6.65.512
788.6.65.52/308.6.65.53 to 8.6.65.548.6.65.552
798.6.65.56/308.6.65.57 to 8.6.65.588.6.65.592
808.6.65.60/308.6.65.61 to 8.6.65.628.6.65.632
818.6.65.64/308.6.65.65 to 8.6.65.668.6.65.672
828.6.65.68/308.6.65.69 to 8.6.65.708.6.65.712
838.6.65.72/308.6.65.73 to 8.6.65.748.6.65.752
848.6.65.76/308.6.65.77 to 8.6.65.788.6.65.792
858.6.65.80/308.6.65.81 to 8.6.65.828.6.65.832
868.6.65.84/308.6.65.85 to 8.6.65.868.6.65.872
878.6.65.88/308.6.65.89 to 8.6.65.908.6.65.912
888.6.65.92/308.6.65.93 to 8.6.65.948.6.65.952
898.6.65.96/308.6.65.97 to 8.6.65.988.6.65.992
908.6.65.100/308.6.65.101 to 8.6.65.1028.6.65.1032
918.6.65.104/308.6.65.105 to 8.6.65.1068.6.65.1072
928.6.65.108/308.6.65.109 to 8.6.65.1108.6.65.1112
938.6.65.112/308.6.65.113 to 8.6.65.1148.6.65.1152
948.6.65.116/308.6.65.117 to 8.6.65.1188.6.65.1192
958.6.65.120/308.6.65.121 to 8.6.65.1228.6.65.1232
968.6.65.124/308.6.65.125 to 8.6.65.1268.6.65.1272
978.6.65.128/308.6.65.129 to 8.6.65.1308.6.65.1312
988.6.65.132/308.6.65.133 to 8.6.65.1348.6.65.1352
998.6.65.136/308.6.65.137 to 8.6.65.1388.6.65.1392
1008.6.65.140/308.6.65.141 to 8.6.65.1428.6.65.1432
1018.6.65.144/308.6.65.145 to 8.6.65.1468.6.65.1472
1028.6.65.148/308.6.65.149 to 8.6.65.1508.6.65.1512
1038.6.65.152/308.6.65.153 to 8.6.65.1548.6.65.1552
1048.6.65.156/308.6.65.157 to 8.6.65.1588.6.65.1592
1058.6.65.160/308.6.65.161 to 8.6.65.1628.6.65.1632
1068.6.65.164/308.6.65.165 to 8.6.65.1668.6.65.1672
1078.6.65.168/308.6.65.169 to 8.6.65.1708.6.65.1712
1088.6.65.172/308.6.65.173 to 8.6.65.1748.6.65.1752
1098.6.65.176/308.6.65.177 to 8.6.65.1788.6.65.1792
1108.6.65.180/308.6.65.181 to 8.6.65.1828.6.65.1832
1118.6.65.184/308.6.65.185 to 8.6.65.1868.6.65.1872
1128.6.65.188/308.6.65.189 to 8.6.65.1908.6.65.1912
1138.6.65.192/308.6.65.193 to 8.6.65.1948.6.65.1952
1148.6.65.196/308.6.65.197 to 8.6.65.1988.6.65.1992
1158.6.65.200/308.6.65.201 to 8.6.65.2028.6.65.2032
1168.6.65.204/308.6.65.205 to 8.6.65.2068.6.65.2072
1178.6.65.208/308.6.65.209 to 8.6.65.2108.6.65.2112
1188.6.65.212/308.6.65.213 to 8.6.65.2148.6.65.2152
1198.6.65.216/308.6.65.217 to 8.6.65.2188.6.65.2192
1208.6.65.220/308.6.65.221 to 8.6.65.2228.6.65.2232
1218.6.65.224/308.6.65.225 to 8.6.65.2268.6.65.2272
1228.6.65.228/308.6.65.229 to 8.6.65.2308.6.65.2312
1238.6.65.232/308.6.65.233 to 8.6.65.2348.6.65.2352
1248.6.65.236/308.6.65.237 to 8.6.65.2388.6.65.2392
1258.6.65.240/308.6.65.241 to 8.6.65.2428.6.65.2432
1268.6.65.244/308.6.65.245 to 8.6.65.2468.6.65.2472
1278.6.65.248/308.6.65.249 to 8.6.65.2508.6.65.2512
1288.6.65.252/308.6.65.253 to 8.6.65.2548.6.65.2552
1298.6.66.0/308.6.66.1 to 8.6.66.28.6.66.32
1308.6.66.4/308.6.66.5 to 8.6.66.68.6.66.72
1318.6.66.8/308.6.66.9 to 8.6.66.108.6.66.112
1328.6.66.12/308.6.66.13 to 8.6.66.148.6.66.152
1338.6.66.16/308.6.66.17 to 8.6.66.188.6.66.192
1348.6.66.20/308.6.66.21 to 8.6.66.228.6.66.232
1358.6.66.24/308.6.66.25 to 8.6.66.268.6.66.272
1368.6.66.28/308.6.66.29 to 8.6.66.308.6.66.312
1378.6.66.32/308.6.66.33 to 8.6.66.348.6.66.352
1388.6.66.36/308.6.66.37 to 8.6.66.388.6.66.392
1398.6.66.40/308.6.66.41 to 8.6.66.428.6.66.432
1408.6.66.44/308.6.66.45 to 8.6.66.468.6.66.472
1418.6.66.48/308.6.66.49 to 8.6.66.508.6.66.512
1428.6.66.52/308.6.66.53 to 8.6.66.548.6.66.552
1438.6.66.56/308.6.66.57 to 8.6.66.588.6.66.592
1448.6.66.60/308.6.66.61 to 8.6.66.628.6.66.632
1458.6.66.64/308.6.66.65 to 8.6.66.668.6.66.672
1468.6.66.68/308.6.66.69 to 8.6.66.708.6.66.712
1478.6.66.72/308.6.66.73 to 8.6.66.748.6.66.752
1488.6.66.76/308.6.66.77 to 8.6.66.788.6.66.792
1498.6.66.80/308.6.66.81 to 8.6.66.828.6.66.832
1508.6.66.84/308.6.66.85 to 8.6.66.868.6.66.872
1518.6.66.88/308.6.66.89 to 8.6.66.908.6.66.912
1528.6.66.92/308.6.66.93 to 8.6.66.948.6.66.952
1538.6.66.96/308.6.66.97 to 8.6.66.988.6.66.992
1548.6.66.100/308.6.66.101 to 8.6.66.1028.6.66.1032
1558.6.66.104/308.6.66.105 to 8.6.66.1068.6.66.1072
1568.6.66.108/308.6.66.109 to 8.6.66.1108.6.66.1112
1578.6.66.112/308.6.66.113 to 8.6.66.1148.6.66.1152
1588.6.66.116/308.6.66.117 to 8.6.66.1188.6.66.1192
1598.6.66.120/308.6.66.121 to 8.6.66.1228.6.66.1232
1608.6.66.124/308.6.66.125 to 8.6.66.1268.6.66.1272
1618.6.66.128/308.6.66.129 to 8.6.66.1308.6.66.1312
1628.6.66.132/308.6.66.133 to 8.6.66.1348.6.66.1352
1638.6.66.136/308.6.66.137 to 8.6.66.1388.6.66.1392
1648.6.66.140/308.6.66.141 to 8.6.66.1428.6.66.1432
1658.6.66.144/308.6.66.145 to 8.6.66.1468.6.66.1472
1668.6.66.148/308.6.66.149 to 8.6.66.1508.6.66.1512
1678.6.66.152/308.6.66.153 to 8.6.66.1548.6.66.1552
1688.6.66.156/308.6.66.157 to 8.6.66.1588.6.66.1592
1698.6.66.160/308.6.66.161 to 8.6.66.1628.6.66.1632
1708.6.66.164/308.6.66.165 to 8.6.66.1668.6.66.1672
1718.6.66.168/308.6.66.169 to 8.6.66.1708.6.66.1712
1728.6.66.172/308.6.66.173 to 8.6.66.1748.6.66.1752
1738.6.66.176/308.6.66.177 to 8.6.66.1788.6.66.1792
1748.6.66.180/308.6.66.181 to 8.6.66.1828.6.66.1832
1758.6.66.184/308.6.66.185 to 8.6.66.1868.6.66.1872
1768.6.66.188/308.6.66.189 to 8.6.66.1908.6.66.1912
1778.6.66.192/308.6.66.193 to 8.6.66.1948.6.66.1952
1788.6.66.196/308.6.66.197 to 8.6.66.1988.6.66.1992
1798.6.66.200/308.6.66.201 to 8.6.66.2028.6.66.2032
1808.6.66.204/308.6.66.205 to 8.6.66.2068.6.66.2072
1818.6.66.208/308.6.66.209 to 8.6.66.2108.6.66.2112
1828.6.66.212/308.6.66.213 to 8.6.66.2148.6.66.2152
1838.6.66.216/308.6.66.217 to 8.6.66.2188.6.66.2192
1848.6.66.220/308.6.66.221 to 8.6.66.2228.6.66.2232
1858.6.66.224/308.6.66.225 to 8.6.66.2268.6.66.2272
1868.6.66.228/308.6.66.229 to 8.6.66.2308.6.66.2312
1878.6.66.232/308.6.66.233 to 8.6.66.2348.6.66.2352
1888.6.66.236/308.6.66.237 to 8.6.66.2388.6.66.2392
1898.6.66.240/308.6.66.241 to 8.6.66.2428.6.66.2432
1908.6.66.244/308.6.66.245 to 8.6.66.2468.6.66.2472
1918.6.66.248/308.6.66.249 to 8.6.66.2508.6.66.2512
1928.6.66.252/308.6.66.253 to 8.6.66.2548.6.66.2552
1938.6.67.0/308.6.67.1 to 8.6.67.28.6.67.32
1948.6.67.4/308.6.67.5 to 8.6.67.68.6.67.72
1958.6.67.8/308.6.67.9 to 8.6.67.108.6.67.112
1968.6.67.12/308.6.67.13 to 8.6.67.148.6.67.152
1978.6.67.16/308.6.67.17 to 8.6.67.188.6.67.192
1988.6.67.20/308.6.67.21 to 8.6.67.228.6.67.232
1998.6.67.24/308.6.67.25 to 8.6.67.268.6.67.272
2008.6.67.28/308.6.67.29 to 8.6.67.308.6.67.312
2018.6.67.32/308.6.67.33 to 8.6.67.348.6.67.352
2028.6.67.36/308.6.67.37 to 8.6.67.388.6.67.392
2038.6.67.40/308.6.67.41 to 8.6.67.428.6.67.432
2048.6.67.44/308.6.67.45 to 8.6.67.468.6.67.472
2058.6.67.48/308.6.67.49 to 8.6.67.508.6.67.512
2068.6.67.52/308.6.67.53 to 8.6.67.548.6.67.552
2078.6.67.56/308.6.67.57 to 8.6.67.588.6.67.592
2088.6.67.60/308.6.67.61 to 8.6.67.628.6.67.632
2098.6.67.64/308.6.67.65 to 8.6.67.668.6.67.672
2108.6.67.68/308.6.67.69 to 8.6.67.708.6.67.712
2118.6.67.72/308.6.67.73 to 8.6.67.748.6.67.752
2128.6.67.76/308.6.67.77 to 8.6.67.788.6.67.792
2138.6.67.80/308.6.67.81 to 8.6.67.828.6.67.832
2148.6.67.84/308.6.67.85 to 8.6.67.868.6.67.872
2158.6.67.88/308.6.67.89 to 8.6.67.908.6.67.912
2168.6.67.92/308.6.67.93 to 8.6.67.948.6.67.952
2178.6.67.96/308.6.67.97 to 8.6.67.988.6.67.992
2188.6.67.100/308.6.67.101 to 8.6.67.1028.6.67.1032
2198.6.67.104/308.6.67.105 to 8.6.67.1068.6.67.1072
2208.6.67.108/308.6.67.109 to 8.6.67.1108.6.67.1112
2218.6.67.112/308.6.67.113 to 8.6.67.1148.6.67.1152
2228.6.67.116/308.6.67.117 to 8.6.67.1188.6.67.1192
2238.6.67.120/308.6.67.121 to 8.6.67.1228.6.67.1232
2248.6.67.124/308.6.67.125 to 8.6.67.1268.6.67.1272
2258.6.67.128/308.6.67.129 to 8.6.67.1308.6.67.1312
2268.6.67.132/308.6.67.133 to 8.6.67.1348.6.67.1352
2278.6.67.136/308.6.67.137 to 8.6.67.1388.6.67.1392
2288.6.67.140/308.6.67.141 to 8.6.67.1428.6.67.1432
2298.6.67.144/308.6.67.145 to 8.6.67.1468.6.67.1472
2308.6.67.148/308.6.67.149 to 8.6.67.1508.6.67.1512
2318.6.67.152/308.6.67.153 to 8.6.67.1548.6.67.1552
2328.6.67.156/308.6.67.157 to 8.6.67.1588.6.67.1592
2338.6.67.160/308.6.67.161 to 8.6.67.1628.6.67.1632
2348.6.67.164/308.6.67.165 to 8.6.67.1668.6.67.1672
2358.6.67.168/308.6.67.169 to 8.6.67.1708.6.67.1712
2368.6.67.172/308.6.67.173 to 8.6.67.1748.6.67.1752
2378.6.67.176/308.6.67.177 to 8.6.67.1788.6.67.1792
2388.6.67.180/308.6.67.181 to 8.6.67.1828.6.67.1832
2398.6.67.184/308.6.67.185 to 8.6.67.1868.6.67.1872
2408.6.67.188/308.6.67.189 to 8.6.67.1908.6.67.1912
2418.6.67.192/308.6.67.193 to 8.6.67.1948.6.67.1952
2428.6.67.196/308.6.67.197 to 8.6.67.1988.6.67.1992
2438.6.67.200/308.6.67.201 to 8.6.67.2028.6.67.2032
2448.6.67.204/308.6.67.205 to 8.6.67.2068.6.67.2072
2458.6.67.208/308.6.67.209 to 8.6.67.2108.6.67.2112
2468.6.67.212/308.6.67.213 to 8.6.67.2148.6.67.2152
2478.6.67.216/308.6.67.217 to 8.6.67.2188.6.67.2192
2488.6.67.220/308.6.67.221 to 8.6.67.2228.6.67.2232
2498.6.67.224/308.6.67.225 to 8.6.67.2268.6.67.2272
2508.6.67.228/308.6.67.229 to 8.6.67.2308.6.67.2312
2518.6.67.232/308.6.67.233 to 8.6.67.2348.6.67.2352
2528.6.67.236/308.6.67.237 to 8.6.67.2388.6.67.2392
2538.6.67.240/308.6.67.241 to 8.6.67.2428.6.67.2432
2548.6.67.244/308.6.67.245 to 8.6.67.2468.6.67.2472
2558.6.67.248/308.6.67.249 to 8.6.67.2508.6.67.2512
2568.6.67.252/308.6.67.253 to 8.6.67.2548.6.67.2552

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.