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.

Network22.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
22.0.0.0
Broadcast address
22.255.255.255
First usable
22.0.0.1
Last usable
22.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Public public
Old class
A (default /8)
As numbers
Hex 16000000 · Integer 369098752 to 385875967
Reverse DNS zone
22.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00010110..00000000.00000000.0000000022.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network00010110..00000000.00000000.0000000022.0.0.0
Broadcast00010110..11111111.11111111.1111111122.255.255.255
Split into smaller subnets/17
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

22.0.0.0/8 makes 512 subnets of /17; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
122.0.0.0/1722.0.0.1 to 22.0.127.25422.0.127.25532,766
222.0.128.0/1722.0.128.1 to 22.0.255.25422.0.255.25532,766
322.1.0.0/1722.1.0.1 to 22.1.127.25422.1.127.25532,766
422.1.128.0/1722.1.128.1 to 22.1.255.25422.1.255.25532,766
522.2.0.0/1722.2.0.1 to 22.2.127.25422.2.127.25532,766
622.2.128.0/1722.2.128.1 to 22.2.255.25422.2.255.25532,766
722.3.0.0/1722.3.0.1 to 22.3.127.25422.3.127.25532,766
822.3.128.0/1722.3.128.1 to 22.3.255.25422.3.255.25532,766
922.4.0.0/1722.4.0.1 to 22.4.127.25422.4.127.25532,766
1022.4.128.0/1722.4.128.1 to 22.4.255.25422.4.255.25532,766
1122.5.0.0/1722.5.0.1 to 22.5.127.25422.5.127.25532,766
1222.5.128.0/1722.5.128.1 to 22.5.255.25422.5.255.25532,766
1322.6.0.0/1722.6.0.1 to 22.6.127.25422.6.127.25532,766
1422.6.128.0/1722.6.128.1 to 22.6.255.25422.6.255.25532,766
1522.7.0.0/1722.7.0.1 to 22.7.127.25422.7.127.25532,766
1622.7.128.0/1722.7.128.1 to 22.7.255.25422.7.255.25532,766
1722.8.0.0/1722.8.0.1 to 22.8.127.25422.8.127.25532,766
1822.8.128.0/1722.8.128.1 to 22.8.255.25422.8.255.25532,766
1922.9.0.0/1722.9.0.1 to 22.9.127.25422.9.127.25532,766
2022.9.128.0/1722.9.128.1 to 22.9.255.25422.9.255.25532,766
2122.10.0.0/1722.10.0.1 to 22.10.127.25422.10.127.25532,766
2222.10.128.0/1722.10.128.1 to 22.10.255.25422.10.255.25532,766
2322.11.0.0/1722.11.0.1 to 22.11.127.25422.11.127.25532,766
2422.11.128.0/1722.11.128.1 to 22.11.255.25422.11.255.25532,766
2522.12.0.0/1722.12.0.1 to 22.12.127.25422.12.127.25532,766
2622.12.128.0/1722.12.128.1 to 22.12.255.25422.12.255.25532,766
2722.13.0.0/1722.13.0.1 to 22.13.127.25422.13.127.25532,766
2822.13.128.0/1722.13.128.1 to 22.13.255.25422.13.255.25532,766
2922.14.0.0/1722.14.0.1 to 22.14.127.25422.14.127.25532,766
3022.14.128.0/1722.14.128.1 to 22.14.255.25422.14.255.25532,766
3122.15.0.0/1722.15.0.1 to 22.15.127.25422.15.127.25532,766
3222.15.128.0/1722.15.128.1 to 22.15.255.25422.15.255.25532,766
3322.16.0.0/1722.16.0.1 to 22.16.127.25422.16.127.25532,766
3422.16.128.0/1722.16.128.1 to 22.16.255.25422.16.255.25532,766
3522.17.0.0/1722.17.0.1 to 22.17.127.25422.17.127.25532,766
3622.17.128.0/1722.17.128.1 to 22.17.255.25422.17.255.25532,766
3722.18.0.0/1722.18.0.1 to 22.18.127.25422.18.127.25532,766
3822.18.128.0/1722.18.128.1 to 22.18.255.25422.18.255.25532,766
3922.19.0.0/1722.19.0.1 to 22.19.127.25422.19.127.25532,766
4022.19.128.0/1722.19.128.1 to 22.19.255.25422.19.255.25532,766
4122.20.0.0/1722.20.0.1 to 22.20.127.25422.20.127.25532,766
4222.20.128.0/1722.20.128.1 to 22.20.255.25422.20.255.25532,766
4322.21.0.0/1722.21.0.1 to 22.21.127.25422.21.127.25532,766
4422.21.128.0/1722.21.128.1 to 22.21.255.25422.21.255.25532,766
4522.22.0.0/1722.22.0.1 to 22.22.127.25422.22.127.25532,766
4622.22.128.0/1722.22.128.1 to 22.22.255.25422.22.255.25532,766
4722.23.0.0/1722.23.0.1 to 22.23.127.25422.23.127.25532,766
4822.23.128.0/1722.23.128.1 to 22.23.255.25422.23.255.25532,766
4922.24.0.0/1722.24.0.1 to 22.24.127.25422.24.127.25532,766
5022.24.128.0/1722.24.128.1 to 22.24.255.25422.24.255.25532,766
5122.25.0.0/1722.25.0.1 to 22.25.127.25422.25.127.25532,766
5222.25.128.0/1722.25.128.1 to 22.25.255.25422.25.255.25532,766
5322.26.0.0/1722.26.0.1 to 22.26.127.25422.26.127.25532,766
5422.26.128.0/1722.26.128.1 to 22.26.255.25422.26.255.25532,766
5522.27.0.0/1722.27.0.1 to 22.27.127.25422.27.127.25532,766
5622.27.128.0/1722.27.128.1 to 22.27.255.25422.27.255.25532,766
5722.28.0.0/1722.28.0.1 to 22.28.127.25422.28.127.25532,766
5822.28.128.0/1722.28.128.1 to 22.28.255.25422.28.255.25532,766
5922.29.0.0/1722.29.0.1 to 22.29.127.25422.29.127.25532,766
6022.29.128.0/1722.29.128.1 to 22.29.255.25422.29.255.25532,766
6122.30.0.0/1722.30.0.1 to 22.30.127.25422.30.127.25532,766
6222.30.128.0/1722.30.128.1 to 22.30.255.25422.30.255.25532,766
6322.31.0.0/1722.31.0.1 to 22.31.127.25422.31.127.25532,766
6422.31.128.0/1722.31.128.1 to 22.31.255.25422.31.255.25532,766
6522.32.0.0/1722.32.0.1 to 22.32.127.25422.32.127.25532,766
6622.32.128.0/1722.32.128.1 to 22.32.255.25422.32.255.25532,766
6722.33.0.0/1722.33.0.1 to 22.33.127.25422.33.127.25532,766
6822.33.128.0/1722.33.128.1 to 22.33.255.25422.33.255.25532,766
6922.34.0.0/1722.34.0.1 to 22.34.127.25422.34.127.25532,766
7022.34.128.0/1722.34.128.1 to 22.34.255.25422.34.255.25532,766
7122.35.0.0/1722.35.0.1 to 22.35.127.25422.35.127.25532,766
7222.35.128.0/1722.35.128.1 to 22.35.255.25422.35.255.25532,766
7322.36.0.0/1722.36.0.1 to 22.36.127.25422.36.127.25532,766
7422.36.128.0/1722.36.128.1 to 22.36.255.25422.36.255.25532,766
7522.37.0.0/1722.37.0.1 to 22.37.127.25422.37.127.25532,766
7622.37.128.0/1722.37.128.1 to 22.37.255.25422.37.255.25532,766
7722.38.0.0/1722.38.0.1 to 22.38.127.25422.38.127.25532,766
7822.38.128.0/1722.38.128.1 to 22.38.255.25422.38.255.25532,766
7922.39.0.0/1722.39.0.1 to 22.39.127.25422.39.127.25532,766
8022.39.128.0/1722.39.128.1 to 22.39.255.25422.39.255.25532,766
8122.40.0.0/1722.40.0.1 to 22.40.127.25422.40.127.25532,766
8222.40.128.0/1722.40.128.1 to 22.40.255.25422.40.255.25532,766
8322.41.0.0/1722.41.0.1 to 22.41.127.25422.41.127.25532,766
8422.41.128.0/1722.41.128.1 to 22.41.255.25422.41.255.25532,766
8522.42.0.0/1722.42.0.1 to 22.42.127.25422.42.127.25532,766
8622.42.128.0/1722.42.128.1 to 22.42.255.25422.42.255.25532,766
8722.43.0.0/1722.43.0.1 to 22.43.127.25422.43.127.25532,766
8822.43.128.0/1722.43.128.1 to 22.43.255.25422.43.255.25532,766
8922.44.0.0/1722.44.0.1 to 22.44.127.25422.44.127.25532,766
9022.44.128.0/1722.44.128.1 to 22.44.255.25422.44.255.25532,766
9122.45.0.0/1722.45.0.1 to 22.45.127.25422.45.127.25532,766
9222.45.128.0/1722.45.128.1 to 22.45.255.25422.45.255.25532,766
9322.46.0.0/1722.46.0.1 to 22.46.127.25422.46.127.25532,766
9422.46.128.0/1722.46.128.1 to 22.46.255.25422.46.255.25532,766
9522.47.0.0/1722.47.0.1 to 22.47.127.25422.47.127.25532,766
9622.47.128.0/1722.47.128.1 to 22.47.255.25422.47.255.25532,766
9722.48.0.0/1722.48.0.1 to 22.48.127.25422.48.127.25532,766
9822.48.128.0/1722.48.128.1 to 22.48.255.25422.48.255.25532,766
9922.49.0.0/1722.49.0.1 to 22.49.127.25422.49.127.25532,766
10022.49.128.0/1722.49.128.1 to 22.49.255.25422.49.255.25532,766
10122.50.0.0/1722.50.0.1 to 22.50.127.25422.50.127.25532,766
10222.50.128.0/1722.50.128.1 to 22.50.255.25422.50.255.25532,766
10322.51.0.0/1722.51.0.1 to 22.51.127.25422.51.127.25532,766
10422.51.128.0/1722.51.128.1 to 22.51.255.25422.51.255.25532,766
10522.52.0.0/1722.52.0.1 to 22.52.127.25422.52.127.25532,766
10622.52.128.0/1722.52.128.1 to 22.52.255.25422.52.255.25532,766
10722.53.0.0/1722.53.0.1 to 22.53.127.25422.53.127.25532,766
10822.53.128.0/1722.53.128.1 to 22.53.255.25422.53.255.25532,766
10922.54.0.0/1722.54.0.1 to 22.54.127.25422.54.127.25532,766
11022.54.128.0/1722.54.128.1 to 22.54.255.25422.54.255.25532,766
11122.55.0.0/1722.55.0.1 to 22.55.127.25422.55.127.25532,766
11222.55.128.0/1722.55.128.1 to 22.55.255.25422.55.255.25532,766
11322.56.0.0/1722.56.0.1 to 22.56.127.25422.56.127.25532,766
11422.56.128.0/1722.56.128.1 to 22.56.255.25422.56.255.25532,766
11522.57.0.0/1722.57.0.1 to 22.57.127.25422.57.127.25532,766
11622.57.128.0/1722.57.128.1 to 22.57.255.25422.57.255.25532,766
11722.58.0.0/1722.58.0.1 to 22.58.127.25422.58.127.25532,766
11822.58.128.0/1722.58.128.1 to 22.58.255.25422.58.255.25532,766
11922.59.0.0/1722.59.0.1 to 22.59.127.25422.59.127.25532,766
12022.59.128.0/1722.59.128.1 to 22.59.255.25422.59.255.25532,766
12122.60.0.0/1722.60.0.1 to 22.60.127.25422.60.127.25532,766
12222.60.128.0/1722.60.128.1 to 22.60.255.25422.60.255.25532,766
12322.61.0.0/1722.61.0.1 to 22.61.127.25422.61.127.25532,766
12422.61.128.0/1722.61.128.1 to 22.61.255.25422.61.255.25532,766
12522.62.0.0/1722.62.0.1 to 22.62.127.25422.62.127.25532,766
12622.62.128.0/1722.62.128.1 to 22.62.255.25422.62.255.25532,766
12722.63.0.0/1722.63.0.1 to 22.63.127.25422.63.127.25532,766
12822.63.128.0/1722.63.128.1 to 22.63.255.25422.63.255.25532,766
12922.64.0.0/1722.64.0.1 to 22.64.127.25422.64.127.25532,766
13022.64.128.0/1722.64.128.1 to 22.64.255.25422.64.255.25532,766
13122.65.0.0/1722.65.0.1 to 22.65.127.25422.65.127.25532,766
13222.65.128.0/1722.65.128.1 to 22.65.255.25422.65.255.25532,766
13322.66.0.0/1722.66.0.1 to 22.66.127.25422.66.127.25532,766
13422.66.128.0/1722.66.128.1 to 22.66.255.25422.66.255.25532,766
13522.67.0.0/1722.67.0.1 to 22.67.127.25422.67.127.25532,766
13622.67.128.0/1722.67.128.1 to 22.67.255.25422.67.255.25532,766
13722.68.0.0/1722.68.0.1 to 22.68.127.25422.68.127.25532,766
13822.68.128.0/1722.68.128.1 to 22.68.255.25422.68.255.25532,766
13922.69.0.0/1722.69.0.1 to 22.69.127.25422.69.127.25532,766
14022.69.128.0/1722.69.128.1 to 22.69.255.25422.69.255.25532,766
14122.70.0.0/1722.70.0.1 to 22.70.127.25422.70.127.25532,766
14222.70.128.0/1722.70.128.1 to 22.70.255.25422.70.255.25532,766
14322.71.0.0/1722.71.0.1 to 22.71.127.25422.71.127.25532,766
14422.71.128.0/1722.71.128.1 to 22.71.255.25422.71.255.25532,766
14522.72.0.0/1722.72.0.1 to 22.72.127.25422.72.127.25532,766
14622.72.128.0/1722.72.128.1 to 22.72.255.25422.72.255.25532,766
14722.73.0.0/1722.73.0.1 to 22.73.127.25422.73.127.25532,766
14822.73.128.0/1722.73.128.1 to 22.73.255.25422.73.255.25532,766
14922.74.0.0/1722.74.0.1 to 22.74.127.25422.74.127.25532,766
15022.74.128.0/1722.74.128.1 to 22.74.255.25422.74.255.25532,766
15122.75.0.0/1722.75.0.1 to 22.75.127.25422.75.127.25532,766
15222.75.128.0/1722.75.128.1 to 22.75.255.25422.75.255.25532,766
15322.76.0.0/1722.76.0.1 to 22.76.127.25422.76.127.25532,766
15422.76.128.0/1722.76.128.1 to 22.76.255.25422.76.255.25532,766
15522.77.0.0/1722.77.0.1 to 22.77.127.25422.77.127.25532,766
15622.77.128.0/1722.77.128.1 to 22.77.255.25422.77.255.25532,766
15722.78.0.0/1722.78.0.1 to 22.78.127.25422.78.127.25532,766
15822.78.128.0/1722.78.128.1 to 22.78.255.25422.78.255.25532,766
15922.79.0.0/1722.79.0.1 to 22.79.127.25422.79.127.25532,766
16022.79.128.0/1722.79.128.1 to 22.79.255.25422.79.255.25532,766
16122.80.0.0/1722.80.0.1 to 22.80.127.25422.80.127.25532,766
16222.80.128.0/1722.80.128.1 to 22.80.255.25422.80.255.25532,766
16322.81.0.0/1722.81.0.1 to 22.81.127.25422.81.127.25532,766
16422.81.128.0/1722.81.128.1 to 22.81.255.25422.81.255.25532,766
16522.82.0.0/1722.82.0.1 to 22.82.127.25422.82.127.25532,766
16622.82.128.0/1722.82.128.1 to 22.82.255.25422.82.255.25532,766
16722.83.0.0/1722.83.0.1 to 22.83.127.25422.83.127.25532,766
16822.83.128.0/1722.83.128.1 to 22.83.255.25422.83.255.25532,766
16922.84.0.0/1722.84.0.1 to 22.84.127.25422.84.127.25532,766
17022.84.128.0/1722.84.128.1 to 22.84.255.25422.84.255.25532,766
17122.85.0.0/1722.85.0.1 to 22.85.127.25422.85.127.25532,766
17222.85.128.0/1722.85.128.1 to 22.85.255.25422.85.255.25532,766
17322.86.0.0/1722.86.0.1 to 22.86.127.25422.86.127.25532,766
17422.86.128.0/1722.86.128.1 to 22.86.255.25422.86.255.25532,766
17522.87.0.0/1722.87.0.1 to 22.87.127.25422.87.127.25532,766
17622.87.128.0/1722.87.128.1 to 22.87.255.25422.87.255.25532,766
17722.88.0.0/1722.88.0.1 to 22.88.127.25422.88.127.25532,766
17822.88.128.0/1722.88.128.1 to 22.88.255.25422.88.255.25532,766
17922.89.0.0/1722.89.0.1 to 22.89.127.25422.89.127.25532,766
18022.89.128.0/1722.89.128.1 to 22.89.255.25422.89.255.25532,766
18122.90.0.0/1722.90.0.1 to 22.90.127.25422.90.127.25532,766
18222.90.128.0/1722.90.128.1 to 22.90.255.25422.90.255.25532,766
18322.91.0.0/1722.91.0.1 to 22.91.127.25422.91.127.25532,766
18422.91.128.0/1722.91.128.1 to 22.91.255.25422.91.255.25532,766
18522.92.0.0/1722.92.0.1 to 22.92.127.25422.92.127.25532,766
18622.92.128.0/1722.92.128.1 to 22.92.255.25422.92.255.25532,766
18722.93.0.0/1722.93.0.1 to 22.93.127.25422.93.127.25532,766
18822.93.128.0/1722.93.128.1 to 22.93.255.25422.93.255.25532,766
18922.94.0.0/1722.94.0.1 to 22.94.127.25422.94.127.25532,766
19022.94.128.0/1722.94.128.1 to 22.94.255.25422.94.255.25532,766
19122.95.0.0/1722.95.0.1 to 22.95.127.25422.95.127.25532,766
19222.95.128.0/1722.95.128.1 to 22.95.255.25422.95.255.25532,766
19322.96.0.0/1722.96.0.1 to 22.96.127.25422.96.127.25532,766
19422.96.128.0/1722.96.128.1 to 22.96.255.25422.96.255.25532,766
19522.97.0.0/1722.97.0.1 to 22.97.127.25422.97.127.25532,766
19622.97.128.0/1722.97.128.1 to 22.97.255.25422.97.255.25532,766
19722.98.0.0/1722.98.0.1 to 22.98.127.25422.98.127.25532,766
19822.98.128.0/1722.98.128.1 to 22.98.255.25422.98.255.25532,766
19922.99.0.0/1722.99.0.1 to 22.99.127.25422.99.127.25532,766
20022.99.128.0/1722.99.128.1 to 22.99.255.25422.99.255.25532,766
20122.100.0.0/1722.100.0.1 to 22.100.127.25422.100.127.25532,766
20222.100.128.0/1722.100.128.1 to 22.100.255.25422.100.255.25532,766
20322.101.0.0/1722.101.0.1 to 22.101.127.25422.101.127.25532,766
20422.101.128.0/1722.101.128.1 to 22.101.255.25422.101.255.25532,766
20522.102.0.0/1722.102.0.1 to 22.102.127.25422.102.127.25532,766
20622.102.128.0/1722.102.128.1 to 22.102.255.25422.102.255.25532,766
20722.103.0.0/1722.103.0.1 to 22.103.127.25422.103.127.25532,766
20822.103.128.0/1722.103.128.1 to 22.103.255.25422.103.255.25532,766
20922.104.0.0/1722.104.0.1 to 22.104.127.25422.104.127.25532,766
21022.104.128.0/1722.104.128.1 to 22.104.255.25422.104.255.25532,766
21122.105.0.0/1722.105.0.1 to 22.105.127.25422.105.127.25532,766
21222.105.128.0/1722.105.128.1 to 22.105.255.25422.105.255.25532,766
21322.106.0.0/1722.106.0.1 to 22.106.127.25422.106.127.25532,766
21422.106.128.0/1722.106.128.1 to 22.106.255.25422.106.255.25532,766
21522.107.0.0/1722.107.0.1 to 22.107.127.25422.107.127.25532,766
21622.107.128.0/1722.107.128.1 to 22.107.255.25422.107.255.25532,766
21722.108.0.0/1722.108.0.1 to 22.108.127.25422.108.127.25532,766
21822.108.128.0/1722.108.128.1 to 22.108.255.25422.108.255.25532,766
21922.109.0.0/1722.109.0.1 to 22.109.127.25422.109.127.25532,766
22022.109.128.0/1722.109.128.1 to 22.109.255.25422.109.255.25532,766
22122.110.0.0/1722.110.0.1 to 22.110.127.25422.110.127.25532,766
22222.110.128.0/1722.110.128.1 to 22.110.255.25422.110.255.25532,766
22322.111.0.0/1722.111.0.1 to 22.111.127.25422.111.127.25532,766
22422.111.128.0/1722.111.128.1 to 22.111.255.25422.111.255.25532,766
22522.112.0.0/1722.112.0.1 to 22.112.127.25422.112.127.25532,766
22622.112.128.0/1722.112.128.1 to 22.112.255.25422.112.255.25532,766
22722.113.0.0/1722.113.0.1 to 22.113.127.25422.113.127.25532,766
22822.113.128.0/1722.113.128.1 to 22.113.255.25422.113.255.25532,766
22922.114.0.0/1722.114.0.1 to 22.114.127.25422.114.127.25532,766
23022.114.128.0/1722.114.128.1 to 22.114.255.25422.114.255.25532,766
23122.115.0.0/1722.115.0.1 to 22.115.127.25422.115.127.25532,766
23222.115.128.0/1722.115.128.1 to 22.115.255.25422.115.255.25532,766
23322.116.0.0/1722.116.0.1 to 22.116.127.25422.116.127.25532,766
23422.116.128.0/1722.116.128.1 to 22.116.255.25422.116.255.25532,766
23522.117.0.0/1722.117.0.1 to 22.117.127.25422.117.127.25532,766
23622.117.128.0/1722.117.128.1 to 22.117.255.25422.117.255.25532,766
23722.118.0.0/1722.118.0.1 to 22.118.127.25422.118.127.25532,766
23822.118.128.0/1722.118.128.1 to 22.118.255.25422.118.255.25532,766
23922.119.0.0/1722.119.0.1 to 22.119.127.25422.119.127.25532,766
24022.119.128.0/1722.119.128.1 to 22.119.255.25422.119.255.25532,766
24122.120.0.0/1722.120.0.1 to 22.120.127.25422.120.127.25532,766
24222.120.128.0/1722.120.128.1 to 22.120.255.25422.120.255.25532,766
24322.121.0.0/1722.121.0.1 to 22.121.127.25422.121.127.25532,766
24422.121.128.0/1722.121.128.1 to 22.121.255.25422.121.255.25532,766
24522.122.0.0/1722.122.0.1 to 22.122.127.25422.122.127.25532,766
24622.122.128.0/1722.122.128.1 to 22.122.255.25422.122.255.25532,766
24722.123.0.0/1722.123.0.1 to 22.123.127.25422.123.127.25532,766
24822.123.128.0/1722.123.128.1 to 22.123.255.25422.123.255.25532,766
24922.124.0.0/1722.124.0.1 to 22.124.127.25422.124.127.25532,766
25022.124.128.0/1722.124.128.1 to 22.124.255.25422.124.255.25532,766
25122.125.0.0/1722.125.0.1 to 22.125.127.25422.125.127.25532,766
25222.125.128.0/1722.125.128.1 to 22.125.255.25422.125.255.25532,766
25322.126.0.0/1722.126.0.1 to 22.126.127.25422.126.127.25532,766
25422.126.128.0/1722.126.128.1 to 22.126.255.25422.126.255.25532,766
25522.127.0.0/1722.127.0.1 to 22.127.127.25422.127.127.25532,766
25622.127.128.0/1722.127.128.1 to 22.127.255.25422.127.255.25532,766

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.