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.

Network66.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
66.0.0.0
Broadcast address
67.255.255.255
First usable
66.0.0.1
Last usable
67.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
A (default /8)
As numbers
Hex 42000000 · Integer 1107296256 to 1140850687
Reverse DNS zones
66.in-addr.arpa
67.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01000010.00000000.00000000.0000000066.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network01000010.00000000.00000000.0000000066.0.0.0
Broadcast01000011.11111111.11111111.1111111167.255.255.255
Split into smaller subnets/18
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

66.0.0.0/7 makes 2,048 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
166.0.0.0/1866.0.0.1 to 66.0.63.25466.0.63.25516,382
266.0.64.0/1866.0.64.1 to 66.0.127.25466.0.127.25516,382
366.0.128.0/1866.0.128.1 to 66.0.191.25466.0.191.25516,382
466.0.192.0/1866.0.192.1 to 66.0.255.25466.0.255.25516,382
566.1.0.0/1866.1.0.1 to 66.1.63.25466.1.63.25516,382
666.1.64.0/1866.1.64.1 to 66.1.127.25466.1.127.25516,382
766.1.128.0/1866.1.128.1 to 66.1.191.25466.1.191.25516,382
866.1.192.0/1866.1.192.1 to 66.1.255.25466.1.255.25516,382
966.2.0.0/1866.2.0.1 to 66.2.63.25466.2.63.25516,382
1066.2.64.0/1866.2.64.1 to 66.2.127.25466.2.127.25516,382
1166.2.128.0/1866.2.128.1 to 66.2.191.25466.2.191.25516,382
1266.2.192.0/1866.2.192.1 to 66.2.255.25466.2.255.25516,382
1366.3.0.0/1866.3.0.1 to 66.3.63.25466.3.63.25516,382
1466.3.64.0/1866.3.64.1 to 66.3.127.25466.3.127.25516,382
1566.3.128.0/1866.3.128.1 to 66.3.191.25466.3.191.25516,382
1666.3.192.0/1866.3.192.1 to 66.3.255.25466.3.255.25516,382
1766.4.0.0/1866.4.0.1 to 66.4.63.25466.4.63.25516,382
1866.4.64.0/1866.4.64.1 to 66.4.127.25466.4.127.25516,382
1966.4.128.0/1866.4.128.1 to 66.4.191.25466.4.191.25516,382
2066.4.192.0/1866.4.192.1 to 66.4.255.25466.4.255.25516,382
2166.5.0.0/1866.5.0.1 to 66.5.63.25466.5.63.25516,382
2266.5.64.0/1866.5.64.1 to 66.5.127.25466.5.127.25516,382
2366.5.128.0/1866.5.128.1 to 66.5.191.25466.5.191.25516,382
2466.5.192.0/1866.5.192.1 to 66.5.255.25466.5.255.25516,382
2566.6.0.0/1866.6.0.1 to 66.6.63.25466.6.63.25516,382
2666.6.64.0/1866.6.64.1 to 66.6.127.25466.6.127.25516,382
2766.6.128.0/1866.6.128.1 to 66.6.191.25466.6.191.25516,382
2866.6.192.0/1866.6.192.1 to 66.6.255.25466.6.255.25516,382
2966.7.0.0/1866.7.0.1 to 66.7.63.25466.7.63.25516,382
3066.7.64.0/1866.7.64.1 to 66.7.127.25466.7.127.25516,382
3166.7.128.0/1866.7.128.1 to 66.7.191.25466.7.191.25516,382
3266.7.192.0/1866.7.192.1 to 66.7.255.25466.7.255.25516,382
3366.8.0.0/1866.8.0.1 to 66.8.63.25466.8.63.25516,382
3466.8.64.0/1866.8.64.1 to 66.8.127.25466.8.127.25516,382
3566.8.128.0/1866.8.128.1 to 66.8.191.25466.8.191.25516,382
3666.8.192.0/1866.8.192.1 to 66.8.255.25466.8.255.25516,382
3766.9.0.0/1866.9.0.1 to 66.9.63.25466.9.63.25516,382
3866.9.64.0/1866.9.64.1 to 66.9.127.25466.9.127.25516,382
3966.9.128.0/1866.9.128.1 to 66.9.191.25466.9.191.25516,382
4066.9.192.0/1866.9.192.1 to 66.9.255.25466.9.255.25516,382
4166.10.0.0/1866.10.0.1 to 66.10.63.25466.10.63.25516,382
4266.10.64.0/1866.10.64.1 to 66.10.127.25466.10.127.25516,382
4366.10.128.0/1866.10.128.1 to 66.10.191.25466.10.191.25516,382
4466.10.192.0/1866.10.192.1 to 66.10.255.25466.10.255.25516,382
4566.11.0.0/1866.11.0.1 to 66.11.63.25466.11.63.25516,382
4666.11.64.0/1866.11.64.1 to 66.11.127.25466.11.127.25516,382
4766.11.128.0/1866.11.128.1 to 66.11.191.25466.11.191.25516,382
4866.11.192.0/1866.11.192.1 to 66.11.255.25466.11.255.25516,382
4966.12.0.0/1866.12.0.1 to 66.12.63.25466.12.63.25516,382
5066.12.64.0/1866.12.64.1 to 66.12.127.25466.12.127.25516,382
5166.12.128.0/1866.12.128.1 to 66.12.191.25466.12.191.25516,382
5266.12.192.0/1866.12.192.1 to 66.12.255.25466.12.255.25516,382
5366.13.0.0/1866.13.0.1 to 66.13.63.25466.13.63.25516,382
5466.13.64.0/1866.13.64.1 to 66.13.127.25466.13.127.25516,382
5566.13.128.0/1866.13.128.1 to 66.13.191.25466.13.191.25516,382
5666.13.192.0/1866.13.192.1 to 66.13.255.25466.13.255.25516,382
5766.14.0.0/1866.14.0.1 to 66.14.63.25466.14.63.25516,382
5866.14.64.0/1866.14.64.1 to 66.14.127.25466.14.127.25516,382
5966.14.128.0/1866.14.128.1 to 66.14.191.25466.14.191.25516,382
6066.14.192.0/1866.14.192.1 to 66.14.255.25466.14.255.25516,382
6166.15.0.0/1866.15.0.1 to 66.15.63.25466.15.63.25516,382
6266.15.64.0/1866.15.64.1 to 66.15.127.25466.15.127.25516,382
6366.15.128.0/1866.15.128.1 to 66.15.191.25466.15.191.25516,382
6466.15.192.0/1866.15.192.1 to 66.15.255.25466.15.255.25516,382
6566.16.0.0/1866.16.0.1 to 66.16.63.25466.16.63.25516,382
6666.16.64.0/1866.16.64.1 to 66.16.127.25466.16.127.25516,382
6766.16.128.0/1866.16.128.1 to 66.16.191.25466.16.191.25516,382
6866.16.192.0/1866.16.192.1 to 66.16.255.25466.16.255.25516,382
6966.17.0.0/1866.17.0.1 to 66.17.63.25466.17.63.25516,382
7066.17.64.0/1866.17.64.1 to 66.17.127.25466.17.127.25516,382
7166.17.128.0/1866.17.128.1 to 66.17.191.25466.17.191.25516,382
7266.17.192.0/1866.17.192.1 to 66.17.255.25466.17.255.25516,382
7366.18.0.0/1866.18.0.1 to 66.18.63.25466.18.63.25516,382
7466.18.64.0/1866.18.64.1 to 66.18.127.25466.18.127.25516,382
7566.18.128.0/1866.18.128.1 to 66.18.191.25466.18.191.25516,382
7666.18.192.0/1866.18.192.1 to 66.18.255.25466.18.255.25516,382
7766.19.0.0/1866.19.0.1 to 66.19.63.25466.19.63.25516,382
7866.19.64.0/1866.19.64.1 to 66.19.127.25466.19.127.25516,382
7966.19.128.0/1866.19.128.1 to 66.19.191.25466.19.191.25516,382
8066.19.192.0/1866.19.192.1 to 66.19.255.25466.19.255.25516,382
8166.20.0.0/1866.20.0.1 to 66.20.63.25466.20.63.25516,382
8266.20.64.0/1866.20.64.1 to 66.20.127.25466.20.127.25516,382
8366.20.128.0/1866.20.128.1 to 66.20.191.25466.20.191.25516,382
8466.20.192.0/1866.20.192.1 to 66.20.255.25466.20.255.25516,382
8566.21.0.0/1866.21.0.1 to 66.21.63.25466.21.63.25516,382
8666.21.64.0/1866.21.64.1 to 66.21.127.25466.21.127.25516,382
8766.21.128.0/1866.21.128.1 to 66.21.191.25466.21.191.25516,382
8866.21.192.0/1866.21.192.1 to 66.21.255.25466.21.255.25516,382
8966.22.0.0/1866.22.0.1 to 66.22.63.25466.22.63.25516,382
9066.22.64.0/1866.22.64.1 to 66.22.127.25466.22.127.25516,382
9166.22.128.0/1866.22.128.1 to 66.22.191.25466.22.191.25516,382
9266.22.192.0/1866.22.192.1 to 66.22.255.25466.22.255.25516,382
9366.23.0.0/1866.23.0.1 to 66.23.63.25466.23.63.25516,382
9466.23.64.0/1866.23.64.1 to 66.23.127.25466.23.127.25516,382
9566.23.128.0/1866.23.128.1 to 66.23.191.25466.23.191.25516,382
9666.23.192.0/1866.23.192.1 to 66.23.255.25466.23.255.25516,382
9766.24.0.0/1866.24.0.1 to 66.24.63.25466.24.63.25516,382
9866.24.64.0/1866.24.64.1 to 66.24.127.25466.24.127.25516,382
9966.24.128.0/1866.24.128.1 to 66.24.191.25466.24.191.25516,382
10066.24.192.0/1866.24.192.1 to 66.24.255.25466.24.255.25516,382
10166.25.0.0/1866.25.0.1 to 66.25.63.25466.25.63.25516,382
10266.25.64.0/1866.25.64.1 to 66.25.127.25466.25.127.25516,382
10366.25.128.0/1866.25.128.1 to 66.25.191.25466.25.191.25516,382
10466.25.192.0/1866.25.192.1 to 66.25.255.25466.25.255.25516,382
10566.26.0.0/1866.26.0.1 to 66.26.63.25466.26.63.25516,382
10666.26.64.0/1866.26.64.1 to 66.26.127.25466.26.127.25516,382
10766.26.128.0/1866.26.128.1 to 66.26.191.25466.26.191.25516,382
10866.26.192.0/1866.26.192.1 to 66.26.255.25466.26.255.25516,382
10966.27.0.0/1866.27.0.1 to 66.27.63.25466.27.63.25516,382
11066.27.64.0/1866.27.64.1 to 66.27.127.25466.27.127.25516,382
11166.27.128.0/1866.27.128.1 to 66.27.191.25466.27.191.25516,382
11266.27.192.0/1866.27.192.1 to 66.27.255.25466.27.255.25516,382
11366.28.0.0/1866.28.0.1 to 66.28.63.25466.28.63.25516,382
11466.28.64.0/1866.28.64.1 to 66.28.127.25466.28.127.25516,382
11566.28.128.0/1866.28.128.1 to 66.28.191.25466.28.191.25516,382
11666.28.192.0/1866.28.192.1 to 66.28.255.25466.28.255.25516,382
11766.29.0.0/1866.29.0.1 to 66.29.63.25466.29.63.25516,382
11866.29.64.0/1866.29.64.1 to 66.29.127.25466.29.127.25516,382
11966.29.128.0/1866.29.128.1 to 66.29.191.25466.29.191.25516,382
12066.29.192.0/1866.29.192.1 to 66.29.255.25466.29.255.25516,382
12166.30.0.0/1866.30.0.1 to 66.30.63.25466.30.63.25516,382
12266.30.64.0/1866.30.64.1 to 66.30.127.25466.30.127.25516,382
12366.30.128.0/1866.30.128.1 to 66.30.191.25466.30.191.25516,382
12466.30.192.0/1866.30.192.1 to 66.30.255.25466.30.255.25516,382
12566.31.0.0/1866.31.0.1 to 66.31.63.25466.31.63.25516,382
12666.31.64.0/1866.31.64.1 to 66.31.127.25466.31.127.25516,382
12766.31.128.0/1866.31.128.1 to 66.31.191.25466.31.191.25516,382
12866.31.192.0/1866.31.192.1 to 66.31.255.25466.31.255.25516,382
12966.32.0.0/1866.32.0.1 to 66.32.63.25466.32.63.25516,382
13066.32.64.0/1866.32.64.1 to 66.32.127.25466.32.127.25516,382
13166.32.128.0/1866.32.128.1 to 66.32.191.25466.32.191.25516,382
13266.32.192.0/1866.32.192.1 to 66.32.255.25466.32.255.25516,382
13366.33.0.0/1866.33.0.1 to 66.33.63.25466.33.63.25516,382
13466.33.64.0/1866.33.64.1 to 66.33.127.25466.33.127.25516,382
13566.33.128.0/1866.33.128.1 to 66.33.191.25466.33.191.25516,382
13666.33.192.0/1866.33.192.1 to 66.33.255.25466.33.255.25516,382
13766.34.0.0/1866.34.0.1 to 66.34.63.25466.34.63.25516,382
13866.34.64.0/1866.34.64.1 to 66.34.127.25466.34.127.25516,382
13966.34.128.0/1866.34.128.1 to 66.34.191.25466.34.191.25516,382
14066.34.192.0/1866.34.192.1 to 66.34.255.25466.34.255.25516,382
14166.35.0.0/1866.35.0.1 to 66.35.63.25466.35.63.25516,382
14266.35.64.0/1866.35.64.1 to 66.35.127.25466.35.127.25516,382
14366.35.128.0/1866.35.128.1 to 66.35.191.25466.35.191.25516,382
14466.35.192.0/1866.35.192.1 to 66.35.255.25466.35.255.25516,382
14566.36.0.0/1866.36.0.1 to 66.36.63.25466.36.63.25516,382
14666.36.64.0/1866.36.64.1 to 66.36.127.25466.36.127.25516,382
14766.36.128.0/1866.36.128.1 to 66.36.191.25466.36.191.25516,382
14866.36.192.0/1866.36.192.1 to 66.36.255.25466.36.255.25516,382
14966.37.0.0/1866.37.0.1 to 66.37.63.25466.37.63.25516,382
15066.37.64.0/1866.37.64.1 to 66.37.127.25466.37.127.25516,382
15166.37.128.0/1866.37.128.1 to 66.37.191.25466.37.191.25516,382
15266.37.192.0/1866.37.192.1 to 66.37.255.25466.37.255.25516,382
15366.38.0.0/1866.38.0.1 to 66.38.63.25466.38.63.25516,382
15466.38.64.0/1866.38.64.1 to 66.38.127.25466.38.127.25516,382
15566.38.128.0/1866.38.128.1 to 66.38.191.25466.38.191.25516,382
15666.38.192.0/1866.38.192.1 to 66.38.255.25466.38.255.25516,382
15766.39.0.0/1866.39.0.1 to 66.39.63.25466.39.63.25516,382
15866.39.64.0/1866.39.64.1 to 66.39.127.25466.39.127.25516,382
15966.39.128.0/1866.39.128.1 to 66.39.191.25466.39.191.25516,382
16066.39.192.0/1866.39.192.1 to 66.39.255.25466.39.255.25516,382
16166.40.0.0/1866.40.0.1 to 66.40.63.25466.40.63.25516,382
16266.40.64.0/1866.40.64.1 to 66.40.127.25466.40.127.25516,382
16366.40.128.0/1866.40.128.1 to 66.40.191.25466.40.191.25516,382
16466.40.192.0/1866.40.192.1 to 66.40.255.25466.40.255.25516,382
16566.41.0.0/1866.41.0.1 to 66.41.63.25466.41.63.25516,382
16666.41.64.0/1866.41.64.1 to 66.41.127.25466.41.127.25516,382
16766.41.128.0/1866.41.128.1 to 66.41.191.25466.41.191.25516,382
16866.41.192.0/1866.41.192.1 to 66.41.255.25466.41.255.25516,382
16966.42.0.0/1866.42.0.1 to 66.42.63.25466.42.63.25516,382
17066.42.64.0/1866.42.64.1 to 66.42.127.25466.42.127.25516,382
17166.42.128.0/1866.42.128.1 to 66.42.191.25466.42.191.25516,382
17266.42.192.0/1866.42.192.1 to 66.42.255.25466.42.255.25516,382
17366.43.0.0/1866.43.0.1 to 66.43.63.25466.43.63.25516,382
17466.43.64.0/1866.43.64.1 to 66.43.127.25466.43.127.25516,382
17566.43.128.0/1866.43.128.1 to 66.43.191.25466.43.191.25516,382
17666.43.192.0/1866.43.192.1 to 66.43.255.25466.43.255.25516,382
17766.44.0.0/1866.44.0.1 to 66.44.63.25466.44.63.25516,382
17866.44.64.0/1866.44.64.1 to 66.44.127.25466.44.127.25516,382
17966.44.128.0/1866.44.128.1 to 66.44.191.25466.44.191.25516,382
18066.44.192.0/1866.44.192.1 to 66.44.255.25466.44.255.25516,382
18166.45.0.0/1866.45.0.1 to 66.45.63.25466.45.63.25516,382
18266.45.64.0/1866.45.64.1 to 66.45.127.25466.45.127.25516,382
18366.45.128.0/1866.45.128.1 to 66.45.191.25466.45.191.25516,382
18466.45.192.0/1866.45.192.1 to 66.45.255.25466.45.255.25516,382
18566.46.0.0/1866.46.0.1 to 66.46.63.25466.46.63.25516,382
18666.46.64.0/1866.46.64.1 to 66.46.127.25466.46.127.25516,382
18766.46.128.0/1866.46.128.1 to 66.46.191.25466.46.191.25516,382
18866.46.192.0/1866.46.192.1 to 66.46.255.25466.46.255.25516,382
18966.47.0.0/1866.47.0.1 to 66.47.63.25466.47.63.25516,382
19066.47.64.0/1866.47.64.1 to 66.47.127.25466.47.127.25516,382
19166.47.128.0/1866.47.128.1 to 66.47.191.25466.47.191.25516,382
19266.47.192.0/1866.47.192.1 to 66.47.255.25466.47.255.25516,382
19366.48.0.0/1866.48.0.1 to 66.48.63.25466.48.63.25516,382
19466.48.64.0/1866.48.64.1 to 66.48.127.25466.48.127.25516,382
19566.48.128.0/1866.48.128.1 to 66.48.191.25466.48.191.25516,382
19666.48.192.0/1866.48.192.1 to 66.48.255.25466.48.255.25516,382
19766.49.0.0/1866.49.0.1 to 66.49.63.25466.49.63.25516,382
19866.49.64.0/1866.49.64.1 to 66.49.127.25466.49.127.25516,382
19966.49.128.0/1866.49.128.1 to 66.49.191.25466.49.191.25516,382
20066.49.192.0/1866.49.192.1 to 66.49.255.25466.49.255.25516,382
20166.50.0.0/1866.50.0.1 to 66.50.63.25466.50.63.25516,382
20266.50.64.0/1866.50.64.1 to 66.50.127.25466.50.127.25516,382
20366.50.128.0/1866.50.128.1 to 66.50.191.25466.50.191.25516,382
20466.50.192.0/1866.50.192.1 to 66.50.255.25466.50.255.25516,382
20566.51.0.0/1866.51.0.1 to 66.51.63.25466.51.63.25516,382
20666.51.64.0/1866.51.64.1 to 66.51.127.25466.51.127.25516,382
20766.51.128.0/1866.51.128.1 to 66.51.191.25466.51.191.25516,382
20866.51.192.0/1866.51.192.1 to 66.51.255.25466.51.255.25516,382
20966.52.0.0/1866.52.0.1 to 66.52.63.25466.52.63.25516,382
21066.52.64.0/1866.52.64.1 to 66.52.127.25466.52.127.25516,382
21166.52.128.0/1866.52.128.1 to 66.52.191.25466.52.191.25516,382
21266.52.192.0/1866.52.192.1 to 66.52.255.25466.52.255.25516,382
21366.53.0.0/1866.53.0.1 to 66.53.63.25466.53.63.25516,382
21466.53.64.0/1866.53.64.1 to 66.53.127.25466.53.127.25516,382
21566.53.128.0/1866.53.128.1 to 66.53.191.25466.53.191.25516,382
21666.53.192.0/1866.53.192.1 to 66.53.255.25466.53.255.25516,382
21766.54.0.0/1866.54.0.1 to 66.54.63.25466.54.63.25516,382
21866.54.64.0/1866.54.64.1 to 66.54.127.25466.54.127.25516,382
21966.54.128.0/1866.54.128.1 to 66.54.191.25466.54.191.25516,382
22066.54.192.0/1866.54.192.1 to 66.54.255.25466.54.255.25516,382
22166.55.0.0/1866.55.0.1 to 66.55.63.25466.55.63.25516,382
22266.55.64.0/1866.55.64.1 to 66.55.127.25466.55.127.25516,382
22366.55.128.0/1866.55.128.1 to 66.55.191.25466.55.191.25516,382
22466.55.192.0/1866.55.192.1 to 66.55.255.25466.55.255.25516,382
22566.56.0.0/1866.56.0.1 to 66.56.63.25466.56.63.25516,382
22666.56.64.0/1866.56.64.1 to 66.56.127.25466.56.127.25516,382
22766.56.128.0/1866.56.128.1 to 66.56.191.25466.56.191.25516,382
22866.56.192.0/1866.56.192.1 to 66.56.255.25466.56.255.25516,382
22966.57.0.0/1866.57.0.1 to 66.57.63.25466.57.63.25516,382
23066.57.64.0/1866.57.64.1 to 66.57.127.25466.57.127.25516,382
23166.57.128.0/1866.57.128.1 to 66.57.191.25466.57.191.25516,382
23266.57.192.0/1866.57.192.1 to 66.57.255.25466.57.255.25516,382
23366.58.0.0/1866.58.0.1 to 66.58.63.25466.58.63.25516,382
23466.58.64.0/1866.58.64.1 to 66.58.127.25466.58.127.25516,382
23566.58.128.0/1866.58.128.1 to 66.58.191.25466.58.191.25516,382
23666.58.192.0/1866.58.192.1 to 66.58.255.25466.58.255.25516,382
23766.59.0.0/1866.59.0.1 to 66.59.63.25466.59.63.25516,382
23866.59.64.0/1866.59.64.1 to 66.59.127.25466.59.127.25516,382
23966.59.128.0/1866.59.128.1 to 66.59.191.25466.59.191.25516,382
24066.59.192.0/1866.59.192.1 to 66.59.255.25466.59.255.25516,382
24166.60.0.0/1866.60.0.1 to 66.60.63.25466.60.63.25516,382
24266.60.64.0/1866.60.64.1 to 66.60.127.25466.60.127.25516,382
24366.60.128.0/1866.60.128.1 to 66.60.191.25466.60.191.25516,382
24466.60.192.0/1866.60.192.1 to 66.60.255.25466.60.255.25516,382
24566.61.0.0/1866.61.0.1 to 66.61.63.25466.61.63.25516,382
24666.61.64.0/1866.61.64.1 to 66.61.127.25466.61.127.25516,382
24766.61.128.0/1866.61.128.1 to 66.61.191.25466.61.191.25516,382
24866.61.192.0/1866.61.192.1 to 66.61.255.25466.61.255.25516,382
24966.62.0.0/1866.62.0.1 to 66.62.63.25466.62.63.25516,382
25066.62.64.0/1866.62.64.1 to 66.62.127.25466.62.127.25516,382
25166.62.128.0/1866.62.128.1 to 66.62.191.25466.62.191.25516,382
25266.62.192.0/1866.62.192.1 to 66.62.255.25466.62.255.25516,382
25366.63.0.0/1866.63.0.1 to 66.63.63.25466.63.63.25516,382
25466.63.64.0/1866.63.64.1 to 66.63.127.25466.63.127.25516,382
25566.63.128.0/1866.63.128.1 to 66.63.191.25466.63.191.25516,382
25666.63.192.0/1866.63.192.1 to 66.63.255.25466.63.255.25516,382

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.