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.

Network31.22.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
31.22.0.0
Broadcast address
31.23.255.255
First usable
31.22.0.1
Last usable
31.23.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
A (default /8)
As numbers
Hex 1F160000 · Integer 521535488 to 521666559
Reverse DNS zones
22.31.in-addr.arpa
23.31.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00011111.00010110.00000000.0000000031.22.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network00011111.00010110.00000000.0000000031.22.0.0
Broadcast00011111.00010111.11111111.1111111131.23.255.255
Split into smaller subnets/26
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

31.22.0.0/15 makes 2,048 subnets of /26; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
131.22.0.0/2631.22.0.1 to 31.22.0.6231.22.0.6362
231.22.0.64/2631.22.0.65 to 31.22.0.12631.22.0.12762
331.22.0.128/2631.22.0.129 to 31.22.0.19031.22.0.19162
431.22.0.192/2631.22.0.193 to 31.22.0.25431.22.0.25562
531.22.1.0/2631.22.1.1 to 31.22.1.6231.22.1.6362
631.22.1.64/2631.22.1.65 to 31.22.1.12631.22.1.12762
731.22.1.128/2631.22.1.129 to 31.22.1.19031.22.1.19162
831.22.1.192/2631.22.1.193 to 31.22.1.25431.22.1.25562
931.22.2.0/2631.22.2.1 to 31.22.2.6231.22.2.6362
1031.22.2.64/2631.22.2.65 to 31.22.2.12631.22.2.12762
1131.22.2.128/2631.22.2.129 to 31.22.2.19031.22.2.19162
1231.22.2.192/2631.22.2.193 to 31.22.2.25431.22.2.25562
1331.22.3.0/2631.22.3.1 to 31.22.3.6231.22.3.6362
1431.22.3.64/2631.22.3.65 to 31.22.3.12631.22.3.12762
1531.22.3.128/2631.22.3.129 to 31.22.3.19031.22.3.19162
1631.22.3.192/2631.22.3.193 to 31.22.3.25431.22.3.25562
1731.22.4.0/2631.22.4.1 to 31.22.4.6231.22.4.6362
1831.22.4.64/2631.22.4.65 to 31.22.4.12631.22.4.12762
1931.22.4.128/2631.22.4.129 to 31.22.4.19031.22.4.19162
2031.22.4.192/2631.22.4.193 to 31.22.4.25431.22.4.25562
2131.22.5.0/2631.22.5.1 to 31.22.5.6231.22.5.6362
2231.22.5.64/2631.22.5.65 to 31.22.5.12631.22.5.12762
2331.22.5.128/2631.22.5.129 to 31.22.5.19031.22.5.19162
2431.22.5.192/2631.22.5.193 to 31.22.5.25431.22.5.25562
2531.22.6.0/2631.22.6.1 to 31.22.6.6231.22.6.6362
2631.22.6.64/2631.22.6.65 to 31.22.6.12631.22.6.12762
2731.22.6.128/2631.22.6.129 to 31.22.6.19031.22.6.19162
2831.22.6.192/2631.22.6.193 to 31.22.6.25431.22.6.25562
2931.22.7.0/2631.22.7.1 to 31.22.7.6231.22.7.6362
3031.22.7.64/2631.22.7.65 to 31.22.7.12631.22.7.12762
3131.22.7.128/2631.22.7.129 to 31.22.7.19031.22.7.19162
3231.22.7.192/2631.22.7.193 to 31.22.7.25431.22.7.25562
3331.22.8.0/2631.22.8.1 to 31.22.8.6231.22.8.6362
3431.22.8.64/2631.22.8.65 to 31.22.8.12631.22.8.12762
3531.22.8.128/2631.22.8.129 to 31.22.8.19031.22.8.19162
3631.22.8.192/2631.22.8.193 to 31.22.8.25431.22.8.25562
3731.22.9.0/2631.22.9.1 to 31.22.9.6231.22.9.6362
3831.22.9.64/2631.22.9.65 to 31.22.9.12631.22.9.12762
3931.22.9.128/2631.22.9.129 to 31.22.9.19031.22.9.19162
4031.22.9.192/2631.22.9.193 to 31.22.9.25431.22.9.25562
4131.22.10.0/2631.22.10.1 to 31.22.10.6231.22.10.6362
4231.22.10.64/2631.22.10.65 to 31.22.10.12631.22.10.12762
4331.22.10.128/2631.22.10.129 to 31.22.10.19031.22.10.19162
4431.22.10.192/2631.22.10.193 to 31.22.10.25431.22.10.25562
4531.22.11.0/2631.22.11.1 to 31.22.11.6231.22.11.6362
4631.22.11.64/2631.22.11.65 to 31.22.11.12631.22.11.12762
4731.22.11.128/2631.22.11.129 to 31.22.11.19031.22.11.19162
4831.22.11.192/2631.22.11.193 to 31.22.11.25431.22.11.25562
4931.22.12.0/2631.22.12.1 to 31.22.12.6231.22.12.6362
5031.22.12.64/2631.22.12.65 to 31.22.12.12631.22.12.12762
5131.22.12.128/2631.22.12.129 to 31.22.12.19031.22.12.19162
5231.22.12.192/2631.22.12.193 to 31.22.12.25431.22.12.25562
5331.22.13.0/2631.22.13.1 to 31.22.13.6231.22.13.6362
5431.22.13.64/2631.22.13.65 to 31.22.13.12631.22.13.12762
5531.22.13.128/2631.22.13.129 to 31.22.13.19031.22.13.19162
5631.22.13.192/2631.22.13.193 to 31.22.13.25431.22.13.25562
5731.22.14.0/2631.22.14.1 to 31.22.14.6231.22.14.6362
5831.22.14.64/2631.22.14.65 to 31.22.14.12631.22.14.12762
5931.22.14.128/2631.22.14.129 to 31.22.14.19031.22.14.19162
6031.22.14.192/2631.22.14.193 to 31.22.14.25431.22.14.25562
6131.22.15.0/2631.22.15.1 to 31.22.15.6231.22.15.6362
6231.22.15.64/2631.22.15.65 to 31.22.15.12631.22.15.12762
6331.22.15.128/2631.22.15.129 to 31.22.15.19031.22.15.19162
6431.22.15.192/2631.22.15.193 to 31.22.15.25431.22.15.25562
6531.22.16.0/2631.22.16.1 to 31.22.16.6231.22.16.6362
6631.22.16.64/2631.22.16.65 to 31.22.16.12631.22.16.12762
6731.22.16.128/2631.22.16.129 to 31.22.16.19031.22.16.19162
6831.22.16.192/2631.22.16.193 to 31.22.16.25431.22.16.25562
6931.22.17.0/2631.22.17.1 to 31.22.17.6231.22.17.6362
7031.22.17.64/2631.22.17.65 to 31.22.17.12631.22.17.12762
7131.22.17.128/2631.22.17.129 to 31.22.17.19031.22.17.19162
7231.22.17.192/2631.22.17.193 to 31.22.17.25431.22.17.25562
7331.22.18.0/2631.22.18.1 to 31.22.18.6231.22.18.6362
7431.22.18.64/2631.22.18.65 to 31.22.18.12631.22.18.12762
7531.22.18.128/2631.22.18.129 to 31.22.18.19031.22.18.19162
7631.22.18.192/2631.22.18.193 to 31.22.18.25431.22.18.25562
7731.22.19.0/2631.22.19.1 to 31.22.19.6231.22.19.6362
7831.22.19.64/2631.22.19.65 to 31.22.19.12631.22.19.12762
7931.22.19.128/2631.22.19.129 to 31.22.19.19031.22.19.19162
8031.22.19.192/2631.22.19.193 to 31.22.19.25431.22.19.25562
8131.22.20.0/2631.22.20.1 to 31.22.20.6231.22.20.6362
8231.22.20.64/2631.22.20.65 to 31.22.20.12631.22.20.12762
8331.22.20.128/2631.22.20.129 to 31.22.20.19031.22.20.19162
8431.22.20.192/2631.22.20.193 to 31.22.20.25431.22.20.25562
8531.22.21.0/2631.22.21.1 to 31.22.21.6231.22.21.6362
8631.22.21.64/2631.22.21.65 to 31.22.21.12631.22.21.12762
8731.22.21.128/2631.22.21.129 to 31.22.21.19031.22.21.19162
8831.22.21.192/2631.22.21.193 to 31.22.21.25431.22.21.25562
8931.22.22.0/2631.22.22.1 to 31.22.22.6231.22.22.6362
9031.22.22.64/2631.22.22.65 to 31.22.22.12631.22.22.12762
9131.22.22.128/2631.22.22.129 to 31.22.22.19031.22.22.19162
9231.22.22.192/2631.22.22.193 to 31.22.22.25431.22.22.25562
9331.22.23.0/2631.22.23.1 to 31.22.23.6231.22.23.6362
9431.22.23.64/2631.22.23.65 to 31.22.23.12631.22.23.12762
9531.22.23.128/2631.22.23.129 to 31.22.23.19031.22.23.19162
9631.22.23.192/2631.22.23.193 to 31.22.23.25431.22.23.25562
9731.22.24.0/2631.22.24.1 to 31.22.24.6231.22.24.6362
9831.22.24.64/2631.22.24.65 to 31.22.24.12631.22.24.12762
9931.22.24.128/2631.22.24.129 to 31.22.24.19031.22.24.19162
10031.22.24.192/2631.22.24.193 to 31.22.24.25431.22.24.25562
10131.22.25.0/2631.22.25.1 to 31.22.25.6231.22.25.6362
10231.22.25.64/2631.22.25.65 to 31.22.25.12631.22.25.12762
10331.22.25.128/2631.22.25.129 to 31.22.25.19031.22.25.19162
10431.22.25.192/2631.22.25.193 to 31.22.25.25431.22.25.25562
10531.22.26.0/2631.22.26.1 to 31.22.26.6231.22.26.6362
10631.22.26.64/2631.22.26.65 to 31.22.26.12631.22.26.12762
10731.22.26.128/2631.22.26.129 to 31.22.26.19031.22.26.19162
10831.22.26.192/2631.22.26.193 to 31.22.26.25431.22.26.25562
10931.22.27.0/2631.22.27.1 to 31.22.27.6231.22.27.6362
11031.22.27.64/2631.22.27.65 to 31.22.27.12631.22.27.12762
11131.22.27.128/2631.22.27.129 to 31.22.27.19031.22.27.19162
11231.22.27.192/2631.22.27.193 to 31.22.27.25431.22.27.25562
11331.22.28.0/2631.22.28.1 to 31.22.28.6231.22.28.6362
11431.22.28.64/2631.22.28.65 to 31.22.28.12631.22.28.12762
11531.22.28.128/2631.22.28.129 to 31.22.28.19031.22.28.19162
11631.22.28.192/2631.22.28.193 to 31.22.28.25431.22.28.25562
11731.22.29.0/2631.22.29.1 to 31.22.29.6231.22.29.6362
11831.22.29.64/2631.22.29.65 to 31.22.29.12631.22.29.12762
11931.22.29.128/2631.22.29.129 to 31.22.29.19031.22.29.19162
12031.22.29.192/2631.22.29.193 to 31.22.29.25431.22.29.25562
12131.22.30.0/2631.22.30.1 to 31.22.30.6231.22.30.6362
12231.22.30.64/2631.22.30.65 to 31.22.30.12631.22.30.12762
12331.22.30.128/2631.22.30.129 to 31.22.30.19031.22.30.19162
12431.22.30.192/2631.22.30.193 to 31.22.30.25431.22.30.25562
12531.22.31.0/2631.22.31.1 to 31.22.31.6231.22.31.6362
12631.22.31.64/2631.22.31.65 to 31.22.31.12631.22.31.12762
12731.22.31.128/2631.22.31.129 to 31.22.31.19031.22.31.19162
12831.22.31.192/2631.22.31.193 to 31.22.31.25431.22.31.25562
12931.22.32.0/2631.22.32.1 to 31.22.32.6231.22.32.6362
13031.22.32.64/2631.22.32.65 to 31.22.32.12631.22.32.12762
13131.22.32.128/2631.22.32.129 to 31.22.32.19031.22.32.19162
13231.22.32.192/2631.22.32.193 to 31.22.32.25431.22.32.25562
13331.22.33.0/2631.22.33.1 to 31.22.33.6231.22.33.6362
13431.22.33.64/2631.22.33.65 to 31.22.33.12631.22.33.12762
13531.22.33.128/2631.22.33.129 to 31.22.33.19031.22.33.19162
13631.22.33.192/2631.22.33.193 to 31.22.33.25431.22.33.25562
13731.22.34.0/2631.22.34.1 to 31.22.34.6231.22.34.6362
13831.22.34.64/2631.22.34.65 to 31.22.34.12631.22.34.12762
13931.22.34.128/2631.22.34.129 to 31.22.34.19031.22.34.19162
14031.22.34.192/2631.22.34.193 to 31.22.34.25431.22.34.25562
14131.22.35.0/2631.22.35.1 to 31.22.35.6231.22.35.6362
14231.22.35.64/2631.22.35.65 to 31.22.35.12631.22.35.12762
14331.22.35.128/2631.22.35.129 to 31.22.35.19031.22.35.19162
14431.22.35.192/2631.22.35.193 to 31.22.35.25431.22.35.25562
14531.22.36.0/2631.22.36.1 to 31.22.36.6231.22.36.6362
14631.22.36.64/2631.22.36.65 to 31.22.36.12631.22.36.12762
14731.22.36.128/2631.22.36.129 to 31.22.36.19031.22.36.19162
14831.22.36.192/2631.22.36.193 to 31.22.36.25431.22.36.25562
14931.22.37.0/2631.22.37.1 to 31.22.37.6231.22.37.6362
15031.22.37.64/2631.22.37.65 to 31.22.37.12631.22.37.12762
15131.22.37.128/2631.22.37.129 to 31.22.37.19031.22.37.19162
15231.22.37.192/2631.22.37.193 to 31.22.37.25431.22.37.25562
15331.22.38.0/2631.22.38.1 to 31.22.38.6231.22.38.6362
15431.22.38.64/2631.22.38.65 to 31.22.38.12631.22.38.12762
15531.22.38.128/2631.22.38.129 to 31.22.38.19031.22.38.19162
15631.22.38.192/2631.22.38.193 to 31.22.38.25431.22.38.25562
15731.22.39.0/2631.22.39.1 to 31.22.39.6231.22.39.6362
15831.22.39.64/2631.22.39.65 to 31.22.39.12631.22.39.12762
15931.22.39.128/2631.22.39.129 to 31.22.39.19031.22.39.19162
16031.22.39.192/2631.22.39.193 to 31.22.39.25431.22.39.25562
16131.22.40.0/2631.22.40.1 to 31.22.40.6231.22.40.6362
16231.22.40.64/2631.22.40.65 to 31.22.40.12631.22.40.12762
16331.22.40.128/2631.22.40.129 to 31.22.40.19031.22.40.19162
16431.22.40.192/2631.22.40.193 to 31.22.40.25431.22.40.25562
16531.22.41.0/2631.22.41.1 to 31.22.41.6231.22.41.6362
16631.22.41.64/2631.22.41.65 to 31.22.41.12631.22.41.12762
16731.22.41.128/2631.22.41.129 to 31.22.41.19031.22.41.19162
16831.22.41.192/2631.22.41.193 to 31.22.41.25431.22.41.25562
16931.22.42.0/2631.22.42.1 to 31.22.42.6231.22.42.6362
17031.22.42.64/2631.22.42.65 to 31.22.42.12631.22.42.12762
17131.22.42.128/2631.22.42.129 to 31.22.42.19031.22.42.19162
17231.22.42.192/2631.22.42.193 to 31.22.42.25431.22.42.25562
17331.22.43.0/2631.22.43.1 to 31.22.43.6231.22.43.6362
17431.22.43.64/2631.22.43.65 to 31.22.43.12631.22.43.12762
17531.22.43.128/2631.22.43.129 to 31.22.43.19031.22.43.19162
17631.22.43.192/2631.22.43.193 to 31.22.43.25431.22.43.25562
17731.22.44.0/2631.22.44.1 to 31.22.44.6231.22.44.6362
17831.22.44.64/2631.22.44.65 to 31.22.44.12631.22.44.12762
17931.22.44.128/2631.22.44.129 to 31.22.44.19031.22.44.19162
18031.22.44.192/2631.22.44.193 to 31.22.44.25431.22.44.25562
18131.22.45.0/2631.22.45.1 to 31.22.45.6231.22.45.6362
18231.22.45.64/2631.22.45.65 to 31.22.45.12631.22.45.12762
18331.22.45.128/2631.22.45.129 to 31.22.45.19031.22.45.19162
18431.22.45.192/2631.22.45.193 to 31.22.45.25431.22.45.25562
18531.22.46.0/2631.22.46.1 to 31.22.46.6231.22.46.6362
18631.22.46.64/2631.22.46.65 to 31.22.46.12631.22.46.12762
18731.22.46.128/2631.22.46.129 to 31.22.46.19031.22.46.19162
18831.22.46.192/2631.22.46.193 to 31.22.46.25431.22.46.25562
18931.22.47.0/2631.22.47.1 to 31.22.47.6231.22.47.6362
19031.22.47.64/2631.22.47.65 to 31.22.47.12631.22.47.12762
19131.22.47.128/2631.22.47.129 to 31.22.47.19031.22.47.19162
19231.22.47.192/2631.22.47.193 to 31.22.47.25431.22.47.25562
19331.22.48.0/2631.22.48.1 to 31.22.48.6231.22.48.6362
19431.22.48.64/2631.22.48.65 to 31.22.48.12631.22.48.12762
19531.22.48.128/2631.22.48.129 to 31.22.48.19031.22.48.19162
19631.22.48.192/2631.22.48.193 to 31.22.48.25431.22.48.25562
19731.22.49.0/2631.22.49.1 to 31.22.49.6231.22.49.6362
19831.22.49.64/2631.22.49.65 to 31.22.49.12631.22.49.12762
19931.22.49.128/2631.22.49.129 to 31.22.49.19031.22.49.19162
20031.22.49.192/2631.22.49.193 to 31.22.49.25431.22.49.25562
20131.22.50.0/2631.22.50.1 to 31.22.50.6231.22.50.6362
20231.22.50.64/2631.22.50.65 to 31.22.50.12631.22.50.12762
20331.22.50.128/2631.22.50.129 to 31.22.50.19031.22.50.19162
20431.22.50.192/2631.22.50.193 to 31.22.50.25431.22.50.25562
20531.22.51.0/2631.22.51.1 to 31.22.51.6231.22.51.6362
20631.22.51.64/2631.22.51.65 to 31.22.51.12631.22.51.12762
20731.22.51.128/2631.22.51.129 to 31.22.51.19031.22.51.19162
20831.22.51.192/2631.22.51.193 to 31.22.51.25431.22.51.25562
20931.22.52.0/2631.22.52.1 to 31.22.52.6231.22.52.6362
21031.22.52.64/2631.22.52.65 to 31.22.52.12631.22.52.12762
21131.22.52.128/2631.22.52.129 to 31.22.52.19031.22.52.19162
21231.22.52.192/2631.22.52.193 to 31.22.52.25431.22.52.25562
21331.22.53.0/2631.22.53.1 to 31.22.53.6231.22.53.6362
21431.22.53.64/2631.22.53.65 to 31.22.53.12631.22.53.12762
21531.22.53.128/2631.22.53.129 to 31.22.53.19031.22.53.19162
21631.22.53.192/2631.22.53.193 to 31.22.53.25431.22.53.25562
21731.22.54.0/2631.22.54.1 to 31.22.54.6231.22.54.6362
21831.22.54.64/2631.22.54.65 to 31.22.54.12631.22.54.12762
21931.22.54.128/2631.22.54.129 to 31.22.54.19031.22.54.19162
22031.22.54.192/2631.22.54.193 to 31.22.54.25431.22.54.25562
22131.22.55.0/2631.22.55.1 to 31.22.55.6231.22.55.6362
22231.22.55.64/2631.22.55.65 to 31.22.55.12631.22.55.12762
22331.22.55.128/2631.22.55.129 to 31.22.55.19031.22.55.19162
22431.22.55.192/2631.22.55.193 to 31.22.55.25431.22.55.25562
22531.22.56.0/2631.22.56.1 to 31.22.56.6231.22.56.6362
22631.22.56.64/2631.22.56.65 to 31.22.56.12631.22.56.12762
22731.22.56.128/2631.22.56.129 to 31.22.56.19031.22.56.19162
22831.22.56.192/2631.22.56.193 to 31.22.56.25431.22.56.25562
22931.22.57.0/2631.22.57.1 to 31.22.57.6231.22.57.6362
23031.22.57.64/2631.22.57.65 to 31.22.57.12631.22.57.12762
23131.22.57.128/2631.22.57.129 to 31.22.57.19031.22.57.19162
23231.22.57.192/2631.22.57.193 to 31.22.57.25431.22.57.25562
23331.22.58.0/2631.22.58.1 to 31.22.58.6231.22.58.6362
23431.22.58.64/2631.22.58.65 to 31.22.58.12631.22.58.12762
23531.22.58.128/2631.22.58.129 to 31.22.58.19031.22.58.19162
23631.22.58.192/2631.22.58.193 to 31.22.58.25431.22.58.25562
23731.22.59.0/2631.22.59.1 to 31.22.59.6231.22.59.6362
23831.22.59.64/2631.22.59.65 to 31.22.59.12631.22.59.12762
23931.22.59.128/2631.22.59.129 to 31.22.59.19031.22.59.19162
24031.22.59.192/2631.22.59.193 to 31.22.59.25431.22.59.25562
24131.22.60.0/2631.22.60.1 to 31.22.60.6231.22.60.6362
24231.22.60.64/2631.22.60.65 to 31.22.60.12631.22.60.12762
24331.22.60.128/2631.22.60.129 to 31.22.60.19031.22.60.19162
24431.22.60.192/2631.22.60.193 to 31.22.60.25431.22.60.25562
24531.22.61.0/2631.22.61.1 to 31.22.61.6231.22.61.6362
24631.22.61.64/2631.22.61.65 to 31.22.61.12631.22.61.12762
24731.22.61.128/2631.22.61.129 to 31.22.61.19031.22.61.19162
24831.22.61.192/2631.22.61.193 to 31.22.61.25431.22.61.25562
24931.22.62.0/2631.22.62.1 to 31.22.62.6231.22.62.6362
25031.22.62.64/2631.22.62.65 to 31.22.62.12631.22.62.12762
25131.22.62.128/2631.22.62.129 to 31.22.62.19031.22.62.19162
25231.22.62.192/2631.22.62.193 to 31.22.62.25431.22.62.25562
25331.22.63.0/2631.22.63.1 to 31.22.63.6231.22.63.6362
25431.22.63.64/2631.22.63.65 to 31.22.63.12631.22.63.12762
25531.22.63.128/2631.22.63.129 to 31.22.63.19031.22.63.19162
25631.22.63.192/2631.22.63.193 to 31.22.63.25431.22.63.25562

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.