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.

Network24.0.0.0/6
Usable hosts67,108,862
Subnet mask252.0.0.0
Addresses67,108,864
Network address
24.0.0.0
Broadcast address
27.255.255.255
First usable
24.0.0.1
Last usable
27.255.255.254
Usable hosts
67,108,862 (67,108,864 less the network and broadcast addresses)
Subnet mask
252.0.0.0
Wildcard mask
3.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/6
Type
Public public
Old class
A (default /8)
As numbers
Hex 18000000 · Integer 402653184 to 469762047
Reverse DNS zones
24.in-addr.arpa
25.in-addr.arpa
26.in-addr.arpa
27.in-addr.arpa
/6 is not on a 8-bit boundary, so it takes 4 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00011000.00000000.00000000.0000000024.0.0.0
Subnet mask11111100.00000000.00000000.00000000252.0.0.0
Network00011000.00000000.00000000.0000000024.0.0.0
Broadcast00011011.11111111.11111111.1111111127.255.255.255
Split into smaller subnets/17
/7 (2)/8 (4)/9 (8)/10 (16)/11 (32)/12 (64)/13 (128)/14 (256)/15 (512)/16 (1,024)/17 (2,048)/18 (4,096)

24.0.0.0/6 makes 2,048 subnets of /17; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
124.0.0.0/1724.0.0.1 to 24.0.127.25424.0.127.25532,766
224.0.128.0/1724.0.128.1 to 24.0.255.25424.0.255.25532,766
324.1.0.0/1724.1.0.1 to 24.1.127.25424.1.127.25532,766
424.1.128.0/1724.1.128.1 to 24.1.255.25424.1.255.25532,766
524.2.0.0/1724.2.0.1 to 24.2.127.25424.2.127.25532,766
624.2.128.0/1724.2.128.1 to 24.2.255.25424.2.255.25532,766
724.3.0.0/1724.3.0.1 to 24.3.127.25424.3.127.25532,766
824.3.128.0/1724.3.128.1 to 24.3.255.25424.3.255.25532,766
924.4.0.0/1724.4.0.1 to 24.4.127.25424.4.127.25532,766
1024.4.128.0/1724.4.128.1 to 24.4.255.25424.4.255.25532,766
1124.5.0.0/1724.5.0.1 to 24.5.127.25424.5.127.25532,766
1224.5.128.0/1724.5.128.1 to 24.5.255.25424.5.255.25532,766
1324.6.0.0/1724.6.0.1 to 24.6.127.25424.6.127.25532,766
1424.6.128.0/1724.6.128.1 to 24.6.255.25424.6.255.25532,766
1524.7.0.0/1724.7.0.1 to 24.7.127.25424.7.127.25532,766
1624.7.128.0/1724.7.128.1 to 24.7.255.25424.7.255.25532,766
1724.8.0.0/1724.8.0.1 to 24.8.127.25424.8.127.25532,766
1824.8.128.0/1724.8.128.1 to 24.8.255.25424.8.255.25532,766
1924.9.0.0/1724.9.0.1 to 24.9.127.25424.9.127.25532,766
2024.9.128.0/1724.9.128.1 to 24.9.255.25424.9.255.25532,766
2124.10.0.0/1724.10.0.1 to 24.10.127.25424.10.127.25532,766
2224.10.128.0/1724.10.128.1 to 24.10.255.25424.10.255.25532,766
2324.11.0.0/1724.11.0.1 to 24.11.127.25424.11.127.25532,766
2424.11.128.0/1724.11.128.1 to 24.11.255.25424.11.255.25532,766
2524.12.0.0/1724.12.0.1 to 24.12.127.25424.12.127.25532,766
2624.12.128.0/1724.12.128.1 to 24.12.255.25424.12.255.25532,766
2724.13.0.0/1724.13.0.1 to 24.13.127.25424.13.127.25532,766
2824.13.128.0/1724.13.128.1 to 24.13.255.25424.13.255.25532,766
2924.14.0.0/1724.14.0.1 to 24.14.127.25424.14.127.25532,766
3024.14.128.0/1724.14.128.1 to 24.14.255.25424.14.255.25532,766
3124.15.0.0/1724.15.0.1 to 24.15.127.25424.15.127.25532,766
3224.15.128.0/1724.15.128.1 to 24.15.255.25424.15.255.25532,766
3324.16.0.0/1724.16.0.1 to 24.16.127.25424.16.127.25532,766
3424.16.128.0/1724.16.128.1 to 24.16.255.25424.16.255.25532,766
3524.17.0.0/1724.17.0.1 to 24.17.127.25424.17.127.25532,766
3624.17.128.0/1724.17.128.1 to 24.17.255.25424.17.255.25532,766
3724.18.0.0/1724.18.0.1 to 24.18.127.25424.18.127.25532,766
3824.18.128.0/1724.18.128.1 to 24.18.255.25424.18.255.25532,766
3924.19.0.0/1724.19.0.1 to 24.19.127.25424.19.127.25532,766
4024.19.128.0/1724.19.128.1 to 24.19.255.25424.19.255.25532,766
4124.20.0.0/1724.20.0.1 to 24.20.127.25424.20.127.25532,766
4224.20.128.0/1724.20.128.1 to 24.20.255.25424.20.255.25532,766
4324.21.0.0/1724.21.0.1 to 24.21.127.25424.21.127.25532,766
4424.21.128.0/1724.21.128.1 to 24.21.255.25424.21.255.25532,766
4524.22.0.0/1724.22.0.1 to 24.22.127.25424.22.127.25532,766
4624.22.128.0/1724.22.128.1 to 24.22.255.25424.22.255.25532,766
4724.23.0.0/1724.23.0.1 to 24.23.127.25424.23.127.25532,766
4824.23.128.0/1724.23.128.1 to 24.23.255.25424.23.255.25532,766
4924.24.0.0/1724.24.0.1 to 24.24.127.25424.24.127.25532,766
5024.24.128.0/1724.24.128.1 to 24.24.255.25424.24.255.25532,766
5124.25.0.0/1724.25.0.1 to 24.25.127.25424.25.127.25532,766
5224.25.128.0/1724.25.128.1 to 24.25.255.25424.25.255.25532,766
5324.26.0.0/1724.26.0.1 to 24.26.127.25424.26.127.25532,766
5424.26.128.0/1724.26.128.1 to 24.26.255.25424.26.255.25532,766
5524.27.0.0/1724.27.0.1 to 24.27.127.25424.27.127.25532,766
5624.27.128.0/1724.27.128.1 to 24.27.255.25424.27.255.25532,766
5724.28.0.0/1724.28.0.1 to 24.28.127.25424.28.127.25532,766
5824.28.128.0/1724.28.128.1 to 24.28.255.25424.28.255.25532,766
5924.29.0.0/1724.29.0.1 to 24.29.127.25424.29.127.25532,766
6024.29.128.0/1724.29.128.1 to 24.29.255.25424.29.255.25532,766
6124.30.0.0/1724.30.0.1 to 24.30.127.25424.30.127.25532,766
6224.30.128.0/1724.30.128.1 to 24.30.255.25424.30.255.25532,766
6324.31.0.0/1724.31.0.1 to 24.31.127.25424.31.127.25532,766
6424.31.128.0/1724.31.128.1 to 24.31.255.25424.31.255.25532,766
6524.32.0.0/1724.32.0.1 to 24.32.127.25424.32.127.25532,766
6624.32.128.0/1724.32.128.1 to 24.32.255.25424.32.255.25532,766
6724.33.0.0/1724.33.0.1 to 24.33.127.25424.33.127.25532,766
6824.33.128.0/1724.33.128.1 to 24.33.255.25424.33.255.25532,766
6924.34.0.0/1724.34.0.1 to 24.34.127.25424.34.127.25532,766
7024.34.128.0/1724.34.128.1 to 24.34.255.25424.34.255.25532,766
7124.35.0.0/1724.35.0.1 to 24.35.127.25424.35.127.25532,766
7224.35.128.0/1724.35.128.1 to 24.35.255.25424.35.255.25532,766
7324.36.0.0/1724.36.0.1 to 24.36.127.25424.36.127.25532,766
7424.36.128.0/1724.36.128.1 to 24.36.255.25424.36.255.25532,766
7524.37.0.0/1724.37.0.1 to 24.37.127.25424.37.127.25532,766
7624.37.128.0/1724.37.128.1 to 24.37.255.25424.37.255.25532,766
7724.38.0.0/1724.38.0.1 to 24.38.127.25424.38.127.25532,766
7824.38.128.0/1724.38.128.1 to 24.38.255.25424.38.255.25532,766
7924.39.0.0/1724.39.0.1 to 24.39.127.25424.39.127.25532,766
8024.39.128.0/1724.39.128.1 to 24.39.255.25424.39.255.25532,766
8124.40.0.0/1724.40.0.1 to 24.40.127.25424.40.127.25532,766
8224.40.128.0/1724.40.128.1 to 24.40.255.25424.40.255.25532,766
8324.41.0.0/1724.41.0.1 to 24.41.127.25424.41.127.25532,766
8424.41.128.0/1724.41.128.1 to 24.41.255.25424.41.255.25532,766
8524.42.0.0/1724.42.0.1 to 24.42.127.25424.42.127.25532,766
8624.42.128.0/1724.42.128.1 to 24.42.255.25424.42.255.25532,766
8724.43.0.0/1724.43.0.1 to 24.43.127.25424.43.127.25532,766
8824.43.128.0/1724.43.128.1 to 24.43.255.25424.43.255.25532,766
8924.44.0.0/1724.44.0.1 to 24.44.127.25424.44.127.25532,766
9024.44.128.0/1724.44.128.1 to 24.44.255.25424.44.255.25532,766
9124.45.0.0/1724.45.0.1 to 24.45.127.25424.45.127.25532,766
9224.45.128.0/1724.45.128.1 to 24.45.255.25424.45.255.25532,766
9324.46.0.0/1724.46.0.1 to 24.46.127.25424.46.127.25532,766
9424.46.128.0/1724.46.128.1 to 24.46.255.25424.46.255.25532,766
9524.47.0.0/1724.47.0.1 to 24.47.127.25424.47.127.25532,766
9624.47.128.0/1724.47.128.1 to 24.47.255.25424.47.255.25532,766
9724.48.0.0/1724.48.0.1 to 24.48.127.25424.48.127.25532,766
9824.48.128.0/1724.48.128.1 to 24.48.255.25424.48.255.25532,766
9924.49.0.0/1724.49.0.1 to 24.49.127.25424.49.127.25532,766
10024.49.128.0/1724.49.128.1 to 24.49.255.25424.49.255.25532,766
10124.50.0.0/1724.50.0.1 to 24.50.127.25424.50.127.25532,766
10224.50.128.0/1724.50.128.1 to 24.50.255.25424.50.255.25532,766
10324.51.0.0/1724.51.0.1 to 24.51.127.25424.51.127.25532,766
10424.51.128.0/1724.51.128.1 to 24.51.255.25424.51.255.25532,766
10524.52.0.0/1724.52.0.1 to 24.52.127.25424.52.127.25532,766
10624.52.128.0/1724.52.128.1 to 24.52.255.25424.52.255.25532,766
10724.53.0.0/1724.53.0.1 to 24.53.127.25424.53.127.25532,766
10824.53.128.0/1724.53.128.1 to 24.53.255.25424.53.255.25532,766
10924.54.0.0/1724.54.0.1 to 24.54.127.25424.54.127.25532,766
11024.54.128.0/1724.54.128.1 to 24.54.255.25424.54.255.25532,766
11124.55.0.0/1724.55.0.1 to 24.55.127.25424.55.127.25532,766
11224.55.128.0/1724.55.128.1 to 24.55.255.25424.55.255.25532,766
11324.56.0.0/1724.56.0.1 to 24.56.127.25424.56.127.25532,766
11424.56.128.0/1724.56.128.1 to 24.56.255.25424.56.255.25532,766
11524.57.0.0/1724.57.0.1 to 24.57.127.25424.57.127.25532,766
11624.57.128.0/1724.57.128.1 to 24.57.255.25424.57.255.25532,766
11724.58.0.0/1724.58.0.1 to 24.58.127.25424.58.127.25532,766
11824.58.128.0/1724.58.128.1 to 24.58.255.25424.58.255.25532,766
11924.59.0.0/1724.59.0.1 to 24.59.127.25424.59.127.25532,766
12024.59.128.0/1724.59.128.1 to 24.59.255.25424.59.255.25532,766
12124.60.0.0/1724.60.0.1 to 24.60.127.25424.60.127.25532,766
12224.60.128.0/1724.60.128.1 to 24.60.255.25424.60.255.25532,766
12324.61.0.0/1724.61.0.1 to 24.61.127.25424.61.127.25532,766
12424.61.128.0/1724.61.128.1 to 24.61.255.25424.61.255.25532,766
12524.62.0.0/1724.62.0.1 to 24.62.127.25424.62.127.25532,766
12624.62.128.0/1724.62.128.1 to 24.62.255.25424.62.255.25532,766
12724.63.0.0/1724.63.0.1 to 24.63.127.25424.63.127.25532,766
12824.63.128.0/1724.63.128.1 to 24.63.255.25424.63.255.25532,766
12924.64.0.0/1724.64.0.1 to 24.64.127.25424.64.127.25532,766
13024.64.128.0/1724.64.128.1 to 24.64.255.25424.64.255.25532,766
13124.65.0.0/1724.65.0.1 to 24.65.127.25424.65.127.25532,766
13224.65.128.0/1724.65.128.1 to 24.65.255.25424.65.255.25532,766
13324.66.0.0/1724.66.0.1 to 24.66.127.25424.66.127.25532,766
13424.66.128.0/1724.66.128.1 to 24.66.255.25424.66.255.25532,766
13524.67.0.0/1724.67.0.1 to 24.67.127.25424.67.127.25532,766
13624.67.128.0/1724.67.128.1 to 24.67.255.25424.67.255.25532,766
13724.68.0.0/1724.68.0.1 to 24.68.127.25424.68.127.25532,766
13824.68.128.0/1724.68.128.1 to 24.68.255.25424.68.255.25532,766
13924.69.0.0/1724.69.0.1 to 24.69.127.25424.69.127.25532,766
14024.69.128.0/1724.69.128.1 to 24.69.255.25424.69.255.25532,766
14124.70.0.0/1724.70.0.1 to 24.70.127.25424.70.127.25532,766
14224.70.128.0/1724.70.128.1 to 24.70.255.25424.70.255.25532,766
14324.71.0.0/1724.71.0.1 to 24.71.127.25424.71.127.25532,766
14424.71.128.0/1724.71.128.1 to 24.71.255.25424.71.255.25532,766
14524.72.0.0/1724.72.0.1 to 24.72.127.25424.72.127.25532,766
14624.72.128.0/1724.72.128.1 to 24.72.255.25424.72.255.25532,766
14724.73.0.0/1724.73.0.1 to 24.73.127.25424.73.127.25532,766
14824.73.128.0/1724.73.128.1 to 24.73.255.25424.73.255.25532,766
14924.74.0.0/1724.74.0.1 to 24.74.127.25424.74.127.25532,766
15024.74.128.0/1724.74.128.1 to 24.74.255.25424.74.255.25532,766
15124.75.0.0/1724.75.0.1 to 24.75.127.25424.75.127.25532,766
15224.75.128.0/1724.75.128.1 to 24.75.255.25424.75.255.25532,766
15324.76.0.0/1724.76.0.1 to 24.76.127.25424.76.127.25532,766
15424.76.128.0/1724.76.128.1 to 24.76.255.25424.76.255.25532,766
15524.77.0.0/1724.77.0.1 to 24.77.127.25424.77.127.25532,766
15624.77.128.0/1724.77.128.1 to 24.77.255.25424.77.255.25532,766
15724.78.0.0/1724.78.0.1 to 24.78.127.25424.78.127.25532,766
15824.78.128.0/1724.78.128.1 to 24.78.255.25424.78.255.25532,766
15924.79.0.0/1724.79.0.1 to 24.79.127.25424.79.127.25532,766
16024.79.128.0/1724.79.128.1 to 24.79.255.25424.79.255.25532,766
16124.80.0.0/1724.80.0.1 to 24.80.127.25424.80.127.25532,766
16224.80.128.0/1724.80.128.1 to 24.80.255.25424.80.255.25532,766
16324.81.0.0/1724.81.0.1 to 24.81.127.25424.81.127.25532,766
16424.81.128.0/1724.81.128.1 to 24.81.255.25424.81.255.25532,766
16524.82.0.0/1724.82.0.1 to 24.82.127.25424.82.127.25532,766
16624.82.128.0/1724.82.128.1 to 24.82.255.25424.82.255.25532,766
16724.83.0.0/1724.83.0.1 to 24.83.127.25424.83.127.25532,766
16824.83.128.0/1724.83.128.1 to 24.83.255.25424.83.255.25532,766
16924.84.0.0/1724.84.0.1 to 24.84.127.25424.84.127.25532,766
17024.84.128.0/1724.84.128.1 to 24.84.255.25424.84.255.25532,766
17124.85.0.0/1724.85.0.1 to 24.85.127.25424.85.127.25532,766
17224.85.128.0/1724.85.128.1 to 24.85.255.25424.85.255.25532,766
17324.86.0.0/1724.86.0.1 to 24.86.127.25424.86.127.25532,766
17424.86.128.0/1724.86.128.1 to 24.86.255.25424.86.255.25532,766
17524.87.0.0/1724.87.0.1 to 24.87.127.25424.87.127.25532,766
17624.87.128.0/1724.87.128.1 to 24.87.255.25424.87.255.25532,766
17724.88.0.0/1724.88.0.1 to 24.88.127.25424.88.127.25532,766
17824.88.128.0/1724.88.128.1 to 24.88.255.25424.88.255.25532,766
17924.89.0.0/1724.89.0.1 to 24.89.127.25424.89.127.25532,766
18024.89.128.0/1724.89.128.1 to 24.89.255.25424.89.255.25532,766
18124.90.0.0/1724.90.0.1 to 24.90.127.25424.90.127.25532,766
18224.90.128.0/1724.90.128.1 to 24.90.255.25424.90.255.25532,766
18324.91.0.0/1724.91.0.1 to 24.91.127.25424.91.127.25532,766
18424.91.128.0/1724.91.128.1 to 24.91.255.25424.91.255.25532,766
18524.92.0.0/1724.92.0.1 to 24.92.127.25424.92.127.25532,766
18624.92.128.0/1724.92.128.1 to 24.92.255.25424.92.255.25532,766
18724.93.0.0/1724.93.0.1 to 24.93.127.25424.93.127.25532,766
18824.93.128.0/1724.93.128.1 to 24.93.255.25424.93.255.25532,766
18924.94.0.0/1724.94.0.1 to 24.94.127.25424.94.127.25532,766
19024.94.128.0/1724.94.128.1 to 24.94.255.25424.94.255.25532,766
19124.95.0.0/1724.95.0.1 to 24.95.127.25424.95.127.25532,766
19224.95.128.0/1724.95.128.1 to 24.95.255.25424.95.255.25532,766
19324.96.0.0/1724.96.0.1 to 24.96.127.25424.96.127.25532,766
19424.96.128.0/1724.96.128.1 to 24.96.255.25424.96.255.25532,766
19524.97.0.0/1724.97.0.1 to 24.97.127.25424.97.127.25532,766
19624.97.128.0/1724.97.128.1 to 24.97.255.25424.97.255.25532,766
19724.98.0.0/1724.98.0.1 to 24.98.127.25424.98.127.25532,766
19824.98.128.0/1724.98.128.1 to 24.98.255.25424.98.255.25532,766
19924.99.0.0/1724.99.0.1 to 24.99.127.25424.99.127.25532,766
20024.99.128.0/1724.99.128.1 to 24.99.255.25424.99.255.25532,766
20124.100.0.0/1724.100.0.1 to 24.100.127.25424.100.127.25532,766
20224.100.128.0/1724.100.128.1 to 24.100.255.25424.100.255.25532,766
20324.101.0.0/1724.101.0.1 to 24.101.127.25424.101.127.25532,766
20424.101.128.0/1724.101.128.1 to 24.101.255.25424.101.255.25532,766
20524.102.0.0/1724.102.0.1 to 24.102.127.25424.102.127.25532,766
20624.102.128.0/1724.102.128.1 to 24.102.255.25424.102.255.25532,766
20724.103.0.0/1724.103.0.1 to 24.103.127.25424.103.127.25532,766
20824.103.128.0/1724.103.128.1 to 24.103.255.25424.103.255.25532,766
20924.104.0.0/1724.104.0.1 to 24.104.127.25424.104.127.25532,766
21024.104.128.0/1724.104.128.1 to 24.104.255.25424.104.255.25532,766
21124.105.0.0/1724.105.0.1 to 24.105.127.25424.105.127.25532,766
21224.105.128.0/1724.105.128.1 to 24.105.255.25424.105.255.25532,766
21324.106.0.0/1724.106.0.1 to 24.106.127.25424.106.127.25532,766
21424.106.128.0/1724.106.128.1 to 24.106.255.25424.106.255.25532,766
21524.107.0.0/1724.107.0.1 to 24.107.127.25424.107.127.25532,766
21624.107.128.0/1724.107.128.1 to 24.107.255.25424.107.255.25532,766
21724.108.0.0/1724.108.0.1 to 24.108.127.25424.108.127.25532,766
21824.108.128.0/1724.108.128.1 to 24.108.255.25424.108.255.25532,766
21924.109.0.0/1724.109.0.1 to 24.109.127.25424.109.127.25532,766
22024.109.128.0/1724.109.128.1 to 24.109.255.25424.109.255.25532,766
22124.110.0.0/1724.110.0.1 to 24.110.127.25424.110.127.25532,766
22224.110.128.0/1724.110.128.1 to 24.110.255.25424.110.255.25532,766
22324.111.0.0/1724.111.0.1 to 24.111.127.25424.111.127.25532,766
22424.111.128.0/1724.111.128.1 to 24.111.255.25424.111.255.25532,766
22524.112.0.0/1724.112.0.1 to 24.112.127.25424.112.127.25532,766
22624.112.128.0/1724.112.128.1 to 24.112.255.25424.112.255.25532,766
22724.113.0.0/1724.113.0.1 to 24.113.127.25424.113.127.25532,766
22824.113.128.0/1724.113.128.1 to 24.113.255.25424.113.255.25532,766
22924.114.0.0/1724.114.0.1 to 24.114.127.25424.114.127.25532,766
23024.114.128.0/1724.114.128.1 to 24.114.255.25424.114.255.25532,766
23124.115.0.0/1724.115.0.1 to 24.115.127.25424.115.127.25532,766
23224.115.128.0/1724.115.128.1 to 24.115.255.25424.115.255.25532,766
23324.116.0.0/1724.116.0.1 to 24.116.127.25424.116.127.25532,766
23424.116.128.0/1724.116.128.1 to 24.116.255.25424.116.255.25532,766
23524.117.0.0/1724.117.0.1 to 24.117.127.25424.117.127.25532,766
23624.117.128.0/1724.117.128.1 to 24.117.255.25424.117.255.25532,766
23724.118.0.0/1724.118.0.1 to 24.118.127.25424.118.127.25532,766
23824.118.128.0/1724.118.128.1 to 24.118.255.25424.118.255.25532,766
23924.119.0.0/1724.119.0.1 to 24.119.127.25424.119.127.25532,766
24024.119.128.0/1724.119.128.1 to 24.119.255.25424.119.255.25532,766
24124.120.0.0/1724.120.0.1 to 24.120.127.25424.120.127.25532,766
24224.120.128.0/1724.120.128.1 to 24.120.255.25424.120.255.25532,766
24324.121.0.0/1724.121.0.1 to 24.121.127.25424.121.127.25532,766
24424.121.128.0/1724.121.128.1 to 24.121.255.25424.121.255.25532,766
24524.122.0.0/1724.122.0.1 to 24.122.127.25424.122.127.25532,766
24624.122.128.0/1724.122.128.1 to 24.122.255.25424.122.255.25532,766
24724.123.0.0/1724.123.0.1 to 24.123.127.25424.123.127.25532,766
24824.123.128.0/1724.123.128.1 to 24.123.255.25424.123.255.25532,766
24924.124.0.0/1724.124.0.1 to 24.124.127.25424.124.127.25532,766
25024.124.128.0/1724.124.128.1 to 24.124.255.25424.124.255.25532,766
25124.125.0.0/1724.125.0.1 to 24.125.127.25424.125.127.25532,766
25224.125.128.0/1724.125.128.1 to 24.125.255.25424.125.255.25532,766
25324.126.0.0/1724.126.0.1 to 24.126.127.25424.126.127.25532,766
25424.126.128.0/1724.126.128.1 to 24.126.255.25424.126.255.25532,766
25524.127.0.0/1724.127.0.1 to 24.127.127.25424.127.127.25532,766
25624.127.128.0/1724.127.128.1 to 24.127.255.25424.127.255.25532,766

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.