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.

Network28.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
28.0.0.0
Broadcast address
29.255.255.255
First usable
28.0.0.1
Last usable
29.255.255.254
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 1C000000 · Integer 469762048 to 503316479
Reverse DNS zones
28.in-addr.arpa
29.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
Address00011100.00000000.00000000.0000000028.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network00011100.00000000.00000000.0000000028.0.0.0
Broadcast00011101.11111111.11111111.1111111129.255.255.255
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)

28.0.0.0/7 makes 2,048 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
128.0.0.0/1828.0.0.1 to 28.0.63.25428.0.63.25516,382
228.0.64.0/1828.0.64.1 to 28.0.127.25428.0.127.25516,382
328.0.128.0/1828.0.128.1 to 28.0.191.25428.0.191.25516,382
428.0.192.0/1828.0.192.1 to 28.0.255.25428.0.255.25516,382
528.1.0.0/1828.1.0.1 to 28.1.63.25428.1.63.25516,382
628.1.64.0/1828.1.64.1 to 28.1.127.25428.1.127.25516,382
728.1.128.0/1828.1.128.1 to 28.1.191.25428.1.191.25516,382
828.1.192.0/1828.1.192.1 to 28.1.255.25428.1.255.25516,382
928.2.0.0/1828.2.0.1 to 28.2.63.25428.2.63.25516,382
1028.2.64.0/1828.2.64.1 to 28.2.127.25428.2.127.25516,382
1128.2.128.0/1828.2.128.1 to 28.2.191.25428.2.191.25516,382
1228.2.192.0/1828.2.192.1 to 28.2.255.25428.2.255.25516,382
1328.3.0.0/1828.3.0.1 to 28.3.63.25428.3.63.25516,382
1428.3.64.0/1828.3.64.1 to 28.3.127.25428.3.127.25516,382
1528.3.128.0/1828.3.128.1 to 28.3.191.25428.3.191.25516,382
1628.3.192.0/1828.3.192.1 to 28.3.255.25428.3.255.25516,382
1728.4.0.0/1828.4.0.1 to 28.4.63.25428.4.63.25516,382
1828.4.64.0/1828.4.64.1 to 28.4.127.25428.4.127.25516,382
1928.4.128.0/1828.4.128.1 to 28.4.191.25428.4.191.25516,382
2028.4.192.0/1828.4.192.1 to 28.4.255.25428.4.255.25516,382
2128.5.0.0/1828.5.0.1 to 28.5.63.25428.5.63.25516,382
2228.5.64.0/1828.5.64.1 to 28.5.127.25428.5.127.25516,382
2328.5.128.0/1828.5.128.1 to 28.5.191.25428.5.191.25516,382
2428.5.192.0/1828.5.192.1 to 28.5.255.25428.5.255.25516,382
2528.6.0.0/1828.6.0.1 to 28.6.63.25428.6.63.25516,382
2628.6.64.0/1828.6.64.1 to 28.6.127.25428.6.127.25516,382
2728.6.128.0/1828.6.128.1 to 28.6.191.25428.6.191.25516,382
2828.6.192.0/1828.6.192.1 to 28.6.255.25428.6.255.25516,382
2928.7.0.0/1828.7.0.1 to 28.7.63.25428.7.63.25516,382
3028.7.64.0/1828.7.64.1 to 28.7.127.25428.7.127.25516,382
3128.7.128.0/1828.7.128.1 to 28.7.191.25428.7.191.25516,382
3228.7.192.0/1828.7.192.1 to 28.7.255.25428.7.255.25516,382
3328.8.0.0/1828.8.0.1 to 28.8.63.25428.8.63.25516,382
3428.8.64.0/1828.8.64.1 to 28.8.127.25428.8.127.25516,382
3528.8.128.0/1828.8.128.1 to 28.8.191.25428.8.191.25516,382
3628.8.192.0/1828.8.192.1 to 28.8.255.25428.8.255.25516,382
3728.9.0.0/1828.9.0.1 to 28.9.63.25428.9.63.25516,382
3828.9.64.0/1828.9.64.1 to 28.9.127.25428.9.127.25516,382
3928.9.128.0/1828.9.128.1 to 28.9.191.25428.9.191.25516,382
4028.9.192.0/1828.9.192.1 to 28.9.255.25428.9.255.25516,382
4128.10.0.0/1828.10.0.1 to 28.10.63.25428.10.63.25516,382
4228.10.64.0/1828.10.64.1 to 28.10.127.25428.10.127.25516,382
4328.10.128.0/1828.10.128.1 to 28.10.191.25428.10.191.25516,382
4428.10.192.0/1828.10.192.1 to 28.10.255.25428.10.255.25516,382
4528.11.0.0/1828.11.0.1 to 28.11.63.25428.11.63.25516,382
4628.11.64.0/1828.11.64.1 to 28.11.127.25428.11.127.25516,382
4728.11.128.0/1828.11.128.1 to 28.11.191.25428.11.191.25516,382
4828.11.192.0/1828.11.192.1 to 28.11.255.25428.11.255.25516,382
4928.12.0.0/1828.12.0.1 to 28.12.63.25428.12.63.25516,382
5028.12.64.0/1828.12.64.1 to 28.12.127.25428.12.127.25516,382
5128.12.128.0/1828.12.128.1 to 28.12.191.25428.12.191.25516,382
5228.12.192.0/1828.12.192.1 to 28.12.255.25428.12.255.25516,382
5328.13.0.0/1828.13.0.1 to 28.13.63.25428.13.63.25516,382
5428.13.64.0/1828.13.64.1 to 28.13.127.25428.13.127.25516,382
5528.13.128.0/1828.13.128.1 to 28.13.191.25428.13.191.25516,382
5628.13.192.0/1828.13.192.1 to 28.13.255.25428.13.255.25516,382
5728.14.0.0/1828.14.0.1 to 28.14.63.25428.14.63.25516,382
5828.14.64.0/1828.14.64.1 to 28.14.127.25428.14.127.25516,382
5928.14.128.0/1828.14.128.1 to 28.14.191.25428.14.191.25516,382
6028.14.192.0/1828.14.192.1 to 28.14.255.25428.14.255.25516,382
6128.15.0.0/1828.15.0.1 to 28.15.63.25428.15.63.25516,382
6228.15.64.0/1828.15.64.1 to 28.15.127.25428.15.127.25516,382
6328.15.128.0/1828.15.128.1 to 28.15.191.25428.15.191.25516,382
6428.15.192.0/1828.15.192.1 to 28.15.255.25428.15.255.25516,382
6528.16.0.0/1828.16.0.1 to 28.16.63.25428.16.63.25516,382
6628.16.64.0/1828.16.64.1 to 28.16.127.25428.16.127.25516,382
6728.16.128.0/1828.16.128.1 to 28.16.191.25428.16.191.25516,382
6828.16.192.0/1828.16.192.1 to 28.16.255.25428.16.255.25516,382
6928.17.0.0/1828.17.0.1 to 28.17.63.25428.17.63.25516,382
7028.17.64.0/1828.17.64.1 to 28.17.127.25428.17.127.25516,382
7128.17.128.0/1828.17.128.1 to 28.17.191.25428.17.191.25516,382
7228.17.192.0/1828.17.192.1 to 28.17.255.25428.17.255.25516,382
7328.18.0.0/1828.18.0.1 to 28.18.63.25428.18.63.25516,382
7428.18.64.0/1828.18.64.1 to 28.18.127.25428.18.127.25516,382
7528.18.128.0/1828.18.128.1 to 28.18.191.25428.18.191.25516,382
7628.18.192.0/1828.18.192.1 to 28.18.255.25428.18.255.25516,382
7728.19.0.0/1828.19.0.1 to 28.19.63.25428.19.63.25516,382
7828.19.64.0/1828.19.64.1 to 28.19.127.25428.19.127.25516,382
7928.19.128.0/1828.19.128.1 to 28.19.191.25428.19.191.25516,382
8028.19.192.0/1828.19.192.1 to 28.19.255.25428.19.255.25516,382
8128.20.0.0/1828.20.0.1 to 28.20.63.25428.20.63.25516,382
8228.20.64.0/1828.20.64.1 to 28.20.127.25428.20.127.25516,382
8328.20.128.0/1828.20.128.1 to 28.20.191.25428.20.191.25516,382
8428.20.192.0/1828.20.192.1 to 28.20.255.25428.20.255.25516,382
8528.21.0.0/1828.21.0.1 to 28.21.63.25428.21.63.25516,382
8628.21.64.0/1828.21.64.1 to 28.21.127.25428.21.127.25516,382
8728.21.128.0/1828.21.128.1 to 28.21.191.25428.21.191.25516,382
8828.21.192.0/1828.21.192.1 to 28.21.255.25428.21.255.25516,382
8928.22.0.0/1828.22.0.1 to 28.22.63.25428.22.63.25516,382
9028.22.64.0/1828.22.64.1 to 28.22.127.25428.22.127.25516,382
9128.22.128.0/1828.22.128.1 to 28.22.191.25428.22.191.25516,382
9228.22.192.0/1828.22.192.1 to 28.22.255.25428.22.255.25516,382
9328.23.0.0/1828.23.0.1 to 28.23.63.25428.23.63.25516,382
9428.23.64.0/1828.23.64.1 to 28.23.127.25428.23.127.25516,382
9528.23.128.0/1828.23.128.1 to 28.23.191.25428.23.191.25516,382
9628.23.192.0/1828.23.192.1 to 28.23.255.25428.23.255.25516,382
9728.24.0.0/1828.24.0.1 to 28.24.63.25428.24.63.25516,382
9828.24.64.0/1828.24.64.1 to 28.24.127.25428.24.127.25516,382
9928.24.128.0/1828.24.128.1 to 28.24.191.25428.24.191.25516,382
10028.24.192.0/1828.24.192.1 to 28.24.255.25428.24.255.25516,382
10128.25.0.0/1828.25.0.1 to 28.25.63.25428.25.63.25516,382
10228.25.64.0/1828.25.64.1 to 28.25.127.25428.25.127.25516,382
10328.25.128.0/1828.25.128.1 to 28.25.191.25428.25.191.25516,382
10428.25.192.0/1828.25.192.1 to 28.25.255.25428.25.255.25516,382
10528.26.0.0/1828.26.0.1 to 28.26.63.25428.26.63.25516,382
10628.26.64.0/1828.26.64.1 to 28.26.127.25428.26.127.25516,382
10728.26.128.0/1828.26.128.1 to 28.26.191.25428.26.191.25516,382
10828.26.192.0/1828.26.192.1 to 28.26.255.25428.26.255.25516,382
10928.27.0.0/1828.27.0.1 to 28.27.63.25428.27.63.25516,382
11028.27.64.0/1828.27.64.1 to 28.27.127.25428.27.127.25516,382
11128.27.128.0/1828.27.128.1 to 28.27.191.25428.27.191.25516,382
11228.27.192.0/1828.27.192.1 to 28.27.255.25428.27.255.25516,382
11328.28.0.0/1828.28.0.1 to 28.28.63.25428.28.63.25516,382
11428.28.64.0/1828.28.64.1 to 28.28.127.25428.28.127.25516,382
11528.28.128.0/1828.28.128.1 to 28.28.191.25428.28.191.25516,382
11628.28.192.0/1828.28.192.1 to 28.28.255.25428.28.255.25516,382
11728.29.0.0/1828.29.0.1 to 28.29.63.25428.29.63.25516,382
11828.29.64.0/1828.29.64.1 to 28.29.127.25428.29.127.25516,382
11928.29.128.0/1828.29.128.1 to 28.29.191.25428.29.191.25516,382
12028.29.192.0/1828.29.192.1 to 28.29.255.25428.29.255.25516,382
12128.30.0.0/1828.30.0.1 to 28.30.63.25428.30.63.25516,382
12228.30.64.0/1828.30.64.1 to 28.30.127.25428.30.127.25516,382
12328.30.128.0/1828.30.128.1 to 28.30.191.25428.30.191.25516,382
12428.30.192.0/1828.30.192.1 to 28.30.255.25428.30.255.25516,382
12528.31.0.0/1828.31.0.1 to 28.31.63.25428.31.63.25516,382
12628.31.64.0/1828.31.64.1 to 28.31.127.25428.31.127.25516,382
12728.31.128.0/1828.31.128.1 to 28.31.191.25428.31.191.25516,382
12828.31.192.0/1828.31.192.1 to 28.31.255.25428.31.255.25516,382
12928.32.0.0/1828.32.0.1 to 28.32.63.25428.32.63.25516,382
13028.32.64.0/1828.32.64.1 to 28.32.127.25428.32.127.25516,382
13128.32.128.0/1828.32.128.1 to 28.32.191.25428.32.191.25516,382
13228.32.192.0/1828.32.192.1 to 28.32.255.25428.32.255.25516,382
13328.33.0.0/1828.33.0.1 to 28.33.63.25428.33.63.25516,382
13428.33.64.0/1828.33.64.1 to 28.33.127.25428.33.127.25516,382
13528.33.128.0/1828.33.128.1 to 28.33.191.25428.33.191.25516,382
13628.33.192.0/1828.33.192.1 to 28.33.255.25428.33.255.25516,382
13728.34.0.0/1828.34.0.1 to 28.34.63.25428.34.63.25516,382
13828.34.64.0/1828.34.64.1 to 28.34.127.25428.34.127.25516,382
13928.34.128.0/1828.34.128.1 to 28.34.191.25428.34.191.25516,382
14028.34.192.0/1828.34.192.1 to 28.34.255.25428.34.255.25516,382
14128.35.0.0/1828.35.0.1 to 28.35.63.25428.35.63.25516,382
14228.35.64.0/1828.35.64.1 to 28.35.127.25428.35.127.25516,382
14328.35.128.0/1828.35.128.1 to 28.35.191.25428.35.191.25516,382
14428.35.192.0/1828.35.192.1 to 28.35.255.25428.35.255.25516,382
14528.36.0.0/1828.36.0.1 to 28.36.63.25428.36.63.25516,382
14628.36.64.0/1828.36.64.1 to 28.36.127.25428.36.127.25516,382
14728.36.128.0/1828.36.128.1 to 28.36.191.25428.36.191.25516,382
14828.36.192.0/1828.36.192.1 to 28.36.255.25428.36.255.25516,382
14928.37.0.0/1828.37.0.1 to 28.37.63.25428.37.63.25516,382
15028.37.64.0/1828.37.64.1 to 28.37.127.25428.37.127.25516,382
15128.37.128.0/1828.37.128.1 to 28.37.191.25428.37.191.25516,382
15228.37.192.0/1828.37.192.1 to 28.37.255.25428.37.255.25516,382
15328.38.0.0/1828.38.0.1 to 28.38.63.25428.38.63.25516,382
15428.38.64.0/1828.38.64.1 to 28.38.127.25428.38.127.25516,382
15528.38.128.0/1828.38.128.1 to 28.38.191.25428.38.191.25516,382
15628.38.192.0/1828.38.192.1 to 28.38.255.25428.38.255.25516,382
15728.39.0.0/1828.39.0.1 to 28.39.63.25428.39.63.25516,382
15828.39.64.0/1828.39.64.1 to 28.39.127.25428.39.127.25516,382
15928.39.128.0/1828.39.128.1 to 28.39.191.25428.39.191.25516,382
16028.39.192.0/1828.39.192.1 to 28.39.255.25428.39.255.25516,382
16128.40.0.0/1828.40.0.1 to 28.40.63.25428.40.63.25516,382
16228.40.64.0/1828.40.64.1 to 28.40.127.25428.40.127.25516,382
16328.40.128.0/1828.40.128.1 to 28.40.191.25428.40.191.25516,382
16428.40.192.0/1828.40.192.1 to 28.40.255.25428.40.255.25516,382
16528.41.0.0/1828.41.0.1 to 28.41.63.25428.41.63.25516,382
16628.41.64.0/1828.41.64.1 to 28.41.127.25428.41.127.25516,382
16728.41.128.0/1828.41.128.1 to 28.41.191.25428.41.191.25516,382
16828.41.192.0/1828.41.192.1 to 28.41.255.25428.41.255.25516,382
16928.42.0.0/1828.42.0.1 to 28.42.63.25428.42.63.25516,382
17028.42.64.0/1828.42.64.1 to 28.42.127.25428.42.127.25516,382
17128.42.128.0/1828.42.128.1 to 28.42.191.25428.42.191.25516,382
17228.42.192.0/1828.42.192.1 to 28.42.255.25428.42.255.25516,382
17328.43.0.0/1828.43.0.1 to 28.43.63.25428.43.63.25516,382
17428.43.64.0/1828.43.64.1 to 28.43.127.25428.43.127.25516,382
17528.43.128.0/1828.43.128.1 to 28.43.191.25428.43.191.25516,382
17628.43.192.0/1828.43.192.1 to 28.43.255.25428.43.255.25516,382
17728.44.0.0/1828.44.0.1 to 28.44.63.25428.44.63.25516,382
17828.44.64.0/1828.44.64.1 to 28.44.127.25428.44.127.25516,382
17928.44.128.0/1828.44.128.1 to 28.44.191.25428.44.191.25516,382
18028.44.192.0/1828.44.192.1 to 28.44.255.25428.44.255.25516,382
18128.45.0.0/1828.45.0.1 to 28.45.63.25428.45.63.25516,382
18228.45.64.0/1828.45.64.1 to 28.45.127.25428.45.127.25516,382
18328.45.128.0/1828.45.128.1 to 28.45.191.25428.45.191.25516,382
18428.45.192.0/1828.45.192.1 to 28.45.255.25428.45.255.25516,382
18528.46.0.0/1828.46.0.1 to 28.46.63.25428.46.63.25516,382
18628.46.64.0/1828.46.64.1 to 28.46.127.25428.46.127.25516,382
18728.46.128.0/1828.46.128.1 to 28.46.191.25428.46.191.25516,382
18828.46.192.0/1828.46.192.1 to 28.46.255.25428.46.255.25516,382
18928.47.0.0/1828.47.0.1 to 28.47.63.25428.47.63.25516,382
19028.47.64.0/1828.47.64.1 to 28.47.127.25428.47.127.25516,382
19128.47.128.0/1828.47.128.1 to 28.47.191.25428.47.191.25516,382
19228.47.192.0/1828.47.192.1 to 28.47.255.25428.47.255.25516,382
19328.48.0.0/1828.48.0.1 to 28.48.63.25428.48.63.25516,382
19428.48.64.0/1828.48.64.1 to 28.48.127.25428.48.127.25516,382
19528.48.128.0/1828.48.128.1 to 28.48.191.25428.48.191.25516,382
19628.48.192.0/1828.48.192.1 to 28.48.255.25428.48.255.25516,382
19728.49.0.0/1828.49.0.1 to 28.49.63.25428.49.63.25516,382
19828.49.64.0/1828.49.64.1 to 28.49.127.25428.49.127.25516,382
19928.49.128.0/1828.49.128.1 to 28.49.191.25428.49.191.25516,382
20028.49.192.0/1828.49.192.1 to 28.49.255.25428.49.255.25516,382
20128.50.0.0/1828.50.0.1 to 28.50.63.25428.50.63.25516,382
20228.50.64.0/1828.50.64.1 to 28.50.127.25428.50.127.25516,382
20328.50.128.0/1828.50.128.1 to 28.50.191.25428.50.191.25516,382
20428.50.192.0/1828.50.192.1 to 28.50.255.25428.50.255.25516,382
20528.51.0.0/1828.51.0.1 to 28.51.63.25428.51.63.25516,382
20628.51.64.0/1828.51.64.1 to 28.51.127.25428.51.127.25516,382
20728.51.128.0/1828.51.128.1 to 28.51.191.25428.51.191.25516,382
20828.51.192.0/1828.51.192.1 to 28.51.255.25428.51.255.25516,382
20928.52.0.0/1828.52.0.1 to 28.52.63.25428.52.63.25516,382
21028.52.64.0/1828.52.64.1 to 28.52.127.25428.52.127.25516,382
21128.52.128.0/1828.52.128.1 to 28.52.191.25428.52.191.25516,382
21228.52.192.0/1828.52.192.1 to 28.52.255.25428.52.255.25516,382
21328.53.0.0/1828.53.0.1 to 28.53.63.25428.53.63.25516,382
21428.53.64.0/1828.53.64.1 to 28.53.127.25428.53.127.25516,382
21528.53.128.0/1828.53.128.1 to 28.53.191.25428.53.191.25516,382
21628.53.192.0/1828.53.192.1 to 28.53.255.25428.53.255.25516,382
21728.54.0.0/1828.54.0.1 to 28.54.63.25428.54.63.25516,382
21828.54.64.0/1828.54.64.1 to 28.54.127.25428.54.127.25516,382
21928.54.128.0/1828.54.128.1 to 28.54.191.25428.54.191.25516,382
22028.54.192.0/1828.54.192.1 to 28.54.255.25428.54.255.25516,382
22128.55.0.0/1828.55.0.1 to 28.55.63.25428.55.63.25516,382
22228.55.64.0/1828.55.64.1 to 28.55.127.25428.55.127.25516,382
22328.55.128.0/1828.55.128.1 to 28.55.191.25428.55.191.25516,382
22428.55.192.0/1828.55.192.1 to 28.55.255.25428.55.255.25516,382
22528.56.0.0/1828.56.0.1 to 28.56.63.25428.56.63.25516,382
22628.56.64.0/1828.56.64.1 to 28.56.127.25428.56.127.25516,382
22728.56.128.0/1828.56.128.1 to 28.56.191.25428.56.191.25516,382
22828.56.192.0/1828.56.192.1 to 28.56.255.25428.56.255.25516,382
22928.57.0.0/1828.57.0.1 to 28.57.63.25428.57.63.25516,382
23028.57.64.0/1828.57.64.1 to 28.57.127.25428.57.127.25516,382
23128.57.128.0/1828.57.128.1 to 28.57.191.25428.57.191.25516,382
23228.57.192.0/1828.57.192.1 to 28.57.255.25428.57.255.25516,382
23328.58.0.0/1828.58.0.1 to 28.58.63.25428.58.63.25516,382
23428.58.64.0/1828.58.64.1 to 28.58.127.25428.58.127.25516,382
23528.58.128.0/1828.58.128.1 to 28.58.191.25428.58.191.25516,382
23628.58.192.0/1828.58.192.1 to 28.58.255.25428.58.255.25516,382
23728.59.0.0/1828.59.0.1 to 28.59.63.25428.59.63.25516,382
23828.59.64.0/1828.59.64.1 to 28.59.127.25428.59.127.25516,382
23928.59.128.0/1828.59.128.1 to 28.59.191.25428.59.191.25516,382
24028.59.192.0/1828.59.192.1 to 28.59.255.25428.59.255.25516,382
24128.60.0.0/1828.60.0.1 to 28.60.63.25428.60.63.25516,382
24228.60.64.0/1828.60.64.1 to 28.60.127.25428.60.127.25516,382
24328.60.128.0/1828.60.128.1 to 28.60.191.25428.60.191.25516,382
24428.60.192.0/1828.60.192.1 to 28.60.255.25428.60.255.25516,382
24528.61.0.0/1828.61.0.1 to 28.61.63.25428.61.63.25516,382
24628.61.64.0/1828.61.64.1 to 28.61.127.25428.61.127.25516,382
24728.61.128.0/1828.61.128.1 to 28.61.191.25428.61.191.25516,382
24828.61.192.0/1828.61.192.1 to 28.61.255.25428.61.255.25516,382
24928.62.0.0/1828.62.0.1 to 28.62.63.25428.62.63.25516,382
25028.62.64.0/1828.62.64.1 to 28.62.127.25428.62.127.25516,382
25128.62.128.0/1828.62.128.1 to 28.62.191.25428.62.191.25516,382
25228.62.192.0/1828.62.192.1 to 28.62.255.25428.62.255.25516,382
25328.63.0.0/1828.63.0.1 to 28.63.63.25428.63.63.25516,382
25428.63.64.0/1828.63.64.1 to 28.63.127.25428.63.127.25516,382
25528.63.128.0/1828.63.128.1 to 28.63.191.25428.63.191.25516,382
25628.63.192.0/1828.63.192.1 to 28.63.255.25428.63.255.25516,382

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.