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.

Network85.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
85.0.0.0
Broadcast address
85.127.255.255
First usable
85.0.0.1
Last usable
85.127.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Public public
Old class
A (default /8)
As numbers
Hex 55000000 · Integer 1426063360 to 1434451967
Reverse DNS zones
0.85.in-addr.arpa
1.85.in-addr.arpa
2.85.in-addr.arpa
3.85.in-addr.arpa
4.85.in-addr.arpa
5.85.in-addr.arpa
6.85.in-addr.arpa
7.85.in-addr.arpa
8.85.in-addr.arpa
9.85.in-addr.arpa
10.85.in-addr.arpa
11.85.in-addr.arpa
12.85.in-addr.arpa
13.85.in-addr.arpa
14.85.in-addr.arpa
15.85.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01010101.00000000.00000000.0000000085.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network01010101.00000000.00000000.0000000085.0.0.0
Broadcast01010101.01111111.11111111.1111111185.127.255.255
Split into smaller subnets/18
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

85.0.0.0/9 makes 512 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
185.0.0.0/1885.0.0.1 to 85.0.63.25485.0.63.25516,382
285.0.64.0/1885.0.64.1 to 85.0.127.25485.0.127.25516,382
385.0.128.0/1885.0.128.1 to 85.0.191.25485.0.191.25516,382
485.0.192.0/1885.0.192.1 to 85.0.255.25485.0.255.25516,382
585.1.0.0/1885.1.0.1 to 85.1.63.25485.1.63.25516,382
685.1.64.0/1885.1.64.1 to 85.1.127.25485.1.127.25516,382
785.1.128.0/1885.1.128.1 to 85.1.191.25485.1.191.25516,382
885.1.192.0/1885.1.192.1 to 85.1.255.25485.1.255.25516,382
985.2.0.0/1885.2.0.1 to 85.2.63.25485.2.63.25516,382
1085.2.64.0/1885.2.64.1 to 85.2.127.25485.2.127.25516,382
1185.2.128.0/1885.2.128.1 to 85.2.191.25485.2.191.25516,382
1285.2.192.0/1885.2.192.1 to 85.2.255.25485.2.255.25516,382
1385.3.0.0/1885.3.0.1 to 85.3.63.25485.3.63.25516,382
1485.3.64.0/1885.3.64.1 to 85.3.127.25485.3.127.25516,382
1585.3.128.0/1885.3.128.1 to 85.3.191.25485.3.191.25516,382
1685.3.192.0/1885.3.192.1 to 85.3.255.25485.3.255.25516,382
1785.4.0.0/1885.4.0.1 to 85.4.63.25485.4.63.25516,382
1885.4.64.0/1885.4.64.1 to 85.4.127.25485.4.127.25516,382
1985.4.128.0/1885.4.128.1 to 85.4.191.25485.4.191.25516,382
2085.4.192.0/1885.4.192.1 to 85.4.255.25485.4.255.25516,382
2185.5.0.0/1885.5.0.1 to 85.5.63.25485.5.63.25516,382
2285.5.64.0/1885.5.64.1 to 85.5.127.25485.5.127.25516,382
2385.5.128.0/1885.5.128.1 to 85.5.191.25485.5.191.25516,382
2485.5.192.0/1885.5.192.1 to 85.5.255.25485.5.255.25516,382
2585.6.0.0/1885.6.0.1 to 85.6.63.25485.6.63.25516,382
2685.6.64.0/1885.6.64.1 to 85.6.127.25485.6.127.25516,382
2785.6.128.0/1885.6.128.1 to 85.6.191.25485.6.191.25516,382
2885.6.192.0/1885.6.192.1 to 85.6.255.25485.6.255.25516,382
2985.7.0.0/1885.7.0.1 to 85.7.63.25485.7.63.25516,382
3085.7.64.0/1885.7.64.1 to 85.7.127.25485.7.127.25516,382
3185.7.128.0/1885.7.128.1 to 85.7.191.25485.7.191.25516,382
3285.7.192.0/1885.7.192.1 to 85.7.255.25485.7.255.25516,382
3385.8.0.0/1885.8.0.1 to 85.8.63.25485.8.63.25516,382
3485.8.64.0/1885.8.64.1 to 85.8.127.25485.8.127.25516,382
3585.8.128.0/1885.8.128.1 to 85.8.191.25485.8.191.25516,382
3685.8.192.0/1885.8.192.1 to 85.8.255.25485.8.255.25516,382
3785.9.0.0/1885.9.0.1 to 85.9.63.25485.9.63.25516,382
3885.9.64.0/1885.9.64.1 to 85.9.127.25485.9.127.25516,382
3985.9.128.0/1885.9.128.1 to 85.9.191.25485.9.191.25516,382
4085.9.192.0/1885.9.192.1 to 85.9.255.25485.9.255.25516,382
4185.10.0.0/1885.10.0.1 to 85.10.63.25485.10.63.25516,382
4285.10.64.0/1885.10.64.1 to 85.10.127.25485.10.127.25516,382
4385.10.128.0/1885.10.128.1 to 85.10.191.25485.10.191.25516,382
4485.10.192.0/1885.10.192.1 to 85.10.255.25485.10.255.25516,382
4585.11.0.0/1885.11.0.1 to 85.11.63.25485.11.63.25516,382
4685.11.64.0/1885.11.64.1 to 85.11.127.25485.11.127.25516,382
4785.11.128.0/1885.11.128.1 to 85.11.191.25485.11.191.25516,382
4885.11.192.0/1885.11.192.1 to 85.11.255.25485.11.255.25516,382
4985.12.0.0/1885.12.0.1 to 85.12.63.25485.12.63.25516,382
5085.12.64.0/1885.12.64.1 to 85.12.127.25485.12.127.25516,382
5185.12.128.0/1885.12.128.1 to 85.12.191.25485.12.191.25516,382
5285.12.192.0/1885.12.192.1 to 85.12.255.25485.12.255.25516,382
5385.13.0.0/1885.13.0.1 to 85.13.63.25485.13.63.25516,382
5485.13.64.0/1885.13.64.1 to 85.13.127.25485.13.127.25516,382
5585.13.128.0/1885.13.128.1 to 85.13.191.25485.13.191.25516,382
5685.13.192.0/1885.13.192.1 to 85.13.255.25485.13.255.25516,382
5785.14.0.0/1885.14.0.1 to 85.14.63.25485.14.63.25516,382
5885.14.64.0/1885.14.64.1 to 85.14.127.25485.14.127.25516,382
5985.14.128.0/1885.14.128.1 to 85.14.191.25485.14.191.25516,382
6085.14.192.0/1885.14.192.1 to 85.14.255.25485.14.255.25516,382
6185.15.0.0/1885.15.0.1 to 85.15.63.25485.15.63.25516,382
6285.15.64.0/1885.15.64.1 to 85.15.127.25485.15.127.25516,382
6385.15.128.0/1885.15.128.1 to 85.15.191.25485.15.191.25516,382
6485.15.192.0/1885.15.192.1 to 85.15.255.25485.15.255.25516,382
6585.16.0.0/1885.16.0.1 to 85.16.63.25485.16.63.25516,382
6685.16.64.0/1885.16.64.1 to 85.16.127.25485.16.127.25516,382
6785.16.128.0/1885.16.128.1 to 85.16.191.25485.16.191.25516,382
6885.16.192.0/1885.16.192.1 to 85.16.255.25485.16.255.25516,382
6985.17.0.0/1885.17.0.1 to 85.17.63.25485.17.63.25516,382
7085.17.64.0/1885.17.64.1 to 85.17.127.25485.17.127.25516,382
7185.17.128.0/1885.17.128.1 to 85.17.191.25485.17.191.25516,382
7285.17.192.0/1885.17.192.1 to 85.17.255.25485.17.255.25516,382
7385.18.0.0/1885.18.0.1 to 85.18.63.25485.18.63.25516,382
7485.18.64.0/1885.18.64.1 to 85.18.127.25485.18.127.25516,382
7585.18.128.0/1885.18.128.1 to 85.18.191.25485.18.191.25516,382
7685.18.192.0/1885.18.192.1 to 85.18.255.25485.18.255.25516,382
7785.19.0.0/1885.19.0.1 to 85.19.63.25485.19.63.25516,382
7885.19.64.0/1885.19.64.1 to 85.19.127.25485.19.127.25516,382
7985.19.128.0/1885.19.128.1 to 85.19.191.25485.19.191.25516,382
8085.19.192.0/1885.19.192.1 to 85.19.255.25485.19.255.25516,382
8185.20.0.0/1885.20.0.1 to 85.20.63.25485.20.63.25516,382
8285.20.64.0/1885.20.64.1 to 85.20.127.25485.20.127.25516,382
8385.20.128.0/1885.20.128.1 to 85.20.191.25485.20.191.25516,382
8485.20.192.0/1885.20.192.1 to 85.20.255.25485.20.255.25516,382
8585.21.0.0/1885.21.0.1 to 85.21.63.25485.21.63.25516,382
8685.21.64.0/1885.21.64.1 to 85.21.127.25485.21.127.25516,382
8785.21.128.0/1885.21.128.1 to 85.21.191.25485.21.191.25516,382
8885.21.192.0/1885.21.192.1 to 85.21.255.25485.21.255.25516,382
8985.22.0.0/1885.22.0.1 to 85.22.63.25485.22.63.25516,382
9085.22.64.0/1885.22.64.1 to 85.22.127.25485.22.127.25516,382
9185.22.128.0/1885.22.128.1 to 85.22.191.25485.22.191.25516,382
9285.22.192.0/1885.22.192.1 to 85.22.255.25485.22.255.25516,382
9385.23.0.0/1885.23.0.1 to 85.23.63.25485.23.63.25516,382
9485.23.64.0/1885.23.64.1 to 85.23.127.25485.23.127.25516,382
9585.23.128.0/1885.23.128.1 to 85.23.191.25485.23.191.25516,382
9685.23.192.0/1885.23.192.1 to 85.23.255.25485.23.255.25516,382
9785.24.0.0/1885.24.0.1 to 85.24.63.25485.24.63.25516,382
9885.24.64.0/1885.24.64.1 to 85.24.127.25485.24.127.25516,382
9985.24.128.0/1885.24.128.1 to 85.24.191.25485.24.191.25516,382
10085.24.192.0/1885.24.192.1 to 85.24.255.25485.24.255.25516,382
10185.25.0.0/1885.25.0.1 to 85.25.63.25485.25.63.25516,382
10285.25.64.0/1885.25.64.1 to 85.25.127.25485.25.127.25516,382
10385.25.128.0/1885.25.128.1 to 85.25.191.25485.25.191.25516,382
10485.25.192.0/1885.25.192.1 to 85.25.255.25485.25.255.25516,382
10585.26.0.0/1885.26.0.1 to 85.26.63.25485.26.63.25516,382
10685.26.64.0/1885.26.64.1 to 85.26.127.25485.26.127.25516,382
10785.26.128.0/1885.26.128.1 to 85.26.191.25485.26.191.25516,382
10885.26.192.0/1885.26.192.1 to 85.26.255.25485.26.255.25516,382
10985.27.0.0/1885.27.0.1 to 85.27.63.25485.27.63.25516,382
11085.27.64.0/1885.27.64.1 to 85.27.127.25485.27.127.25516,382
11185.27.128.0/1885.27.128.1 to 85.27.191.25485.27.191.25516,382
11285.27.192.0/1885.27.192.1 to 85.27.255.25485.27.255.25516,382
11385.28.0.0/1885.28.0.1 to 85.28.63.25485.28.63.25516,382
11485.28.64.0/1885.28.64.1 to 85.28.127.25485.28.127.25516,382
11585.28.128.0/1885.28.128.1 to 85.28.191.25485.28.191.25516,382
11685.28.192.0/1885.28.192.1 to 85.28.255.25485.28.255.25516,382
11785.29.0.0/1885.29.0.1 to 85.29.63.25485.29.63.25516,382
11885.29.64.0/1885.29.64.1 to 85.29.127.25485.29.127.25516,382
11985.29.128.0/1885.29.128.1 to 85.29.191.25485.29.191.25516,382
12085.29.192.0/1885.29.192.1 to 85.29.255.25485.29.255.25516,382
12185.30.0.0/1885.30.0.1 to 85.30.63.25485.30.63.25516,382
12285.30.64.0/1885.30.64.1 to 85.30.127.25485.30.127.25516,382
12385.30.128.0/1885.30.128.1 to 85.30.191.25485.30.191.25516,382
12485.30.192.0/1885.30.192.1 to 85.30.255.25485.30.255.25516,382
12585.31.0.0/1885.31.0.1 to 85.31.63.25485.31.63.25516,382
12685.31.64.0/1885.31.64.1 to 85.31.127.25485.31.127.25516,382
12785.31.128.0/1885.31.128.1 to 85.31.191.25485.31.191.25516,382
12885.31.192.0/1885.31.192.1 to 85.31.255.25485.31.255.25516,382
12985.32.0.0/1885.32.0.1 to 85.32.63.25485.32.63.25516,382
13085.32.64.0/1885.32.64.1 to 85.32.127.25485.32.127.25516,382
13185.32.128.0/1885.32.128.1 to 85.32.191.25485.32.191.25516,382
13285.32.192.0/1885.32.192.1 to 85.32.255.25485.32.255.25516,382
13385.33.0.0/1885.33.0.1 to 85.33.63.25485.33.63.25516,382
13485.33.64.0/1885.33.64.1 to 85.33.127.25485.33.127.25516,382
13585.33.128.0/1885.33.128.1 to 85.33.191.25485.33.191.25516,382
13685.33.192.0/1885.33.192.1 to 85.33.255.25485.33.255.25516,382
13785.34.0.0/1885.34.0.1 to 85.34.63.25485.34.63.25516,382
13885.34.64.0/1885.34.64.1 to 85.34.127.25485.34.127.25516,382
13985.34.128.0/1885.34.128.1 to 85.34.191.25485.34.191.25516,382
14085.34.192.0/1885.34.192.1 to 85.34.255.25485.34.255.25516,382
14185.35.0.0/1885.35.0.1 to 85.35.63.25485.35.63.25516,382
14285.35.64.0/1885.35.64.1 to 85.35.127.25485.35.127.25516,382
14385.35.128.0/1885.35.128.1 to 85.35.191.25485.35.191.25516,382
14485.35.192.0/1885.35.192.1 to 85.35.255.25485.35.255.25516,382
14585.36.0.0/1885.36.0.1 to 85.36.63.25485.36.63.25516,382
14685.36.64.0/1885.36.64.1 to 85.36.127.25485.36.127.25516,382
14785.36.128.0/1885.36.128.1 to 85.36.191.25485.36.191.25516,382
14885.36.192.0/1885.36.192.1 to 85.36.255.25485.36.255.25516,382
14985.37.0.0/1885.37.0.1 to 85.37.63.25485.37.63.25516,382
15085.37.64.0/1885.37.64.1 to 85.37.127.25485.37.127.25516,382
15185.37.128.0/1885.37.128.1 to 85.37.191.25485.37.191.25516,382
15285.37.192.0/1885.37.192.1 to 85.37.255.25485.37.255.25516,382
15385.38.0.0/1885.38.0.1 to 85.38.63.25485.38.63.25516,382
15485.38.64.0/1885.38.64.1 to 85.38.127.25485.38.127.25516,382
15585.38.128.0/1885.38.128.1 to 85.38.191.25485.38.191.25516,382
15685.38.192.0/1885.38.192.1 to 85.38.255.25485.38.255.25516,382
15785.39.0.0/1885.39.0.1 to 85.39.63.25485.39.63.25516,382
15885.39.64.0/1885.39.64.1 to 85.39.127.25485.39.127.25516,382
15985.39.128.0/1885.39.128.1 to 85.39.191.25485.39.191.25516,382
16085.39.192.0/1885.39.192.1 to 85.39.255.25485.39.255.25516,382
16185.40.0.0/1885.40.0.1 to 85.40.63.25485.40.63.25516,382
16285.40.64.0/1885.40.64.1 to 85.40.127.25485.40.127.25516,382
16385.40.128.0/1885.40.128.1 to 85.40.191.25485.40.191.25516,382
16485.40.192.0/1885.40.192.1 to 85.40.255.25485.40.255.25516,382
16585.41.0.0/1885.41.0.1 to 85.41.63.25485.41.63.25516,382
16685.41.64.0/1885.41.64.1 to 85.41.127.25485.41.127.25516,382
16785.41.128.0/1885.41.128.1 to 85.41.191.25485.41.191.25516,382
16885.41.192.0/1885.41.192.1 to 85.41.255.25485.41.255.25516,382
16985.42.0.0/1885.42.0.1 to 85.42.63.25485.42.63.25516,382
17085.42.64.0/1885.42.64.1 to 85.42.127.25485.42.127.25516,382
17185.42.128.0/1885.42.128.1 to 85.42.191.25485.42.191.25516,382
17285.42.192.0/1885.42.192.1 to 85.42.255.25485.42.255.25516,382
17385.43.0.0/1885.43.0.1 to 85.43.63.25485.43.63.25516,382
17485.43.64.0/1885.43.64.1 to 85.43.127.25485.43.127.25516,382
17585.43.128.0/1885.43.128.1 to 85.43.191.25485.43.191.25516,382
17685.43.192.0/1885.43.192.1 to 85.43.255.25485.43.255.25516,382
17785.44.0.0/1885.44.0.1 to 85.44.63.25485.44.63.25516,382
17885.44.64.0/1885.44.64.1 to 85.44.127.25485.44.127.25516,382
17985.44.128.0/1885.44.128.1 to 85.44.191.25485.44.191.25516,382
18085.44.192.0/1885.44.192.1 to 85.44.255.25485.44.255.25516,382
18185.45.0.0/1885.45.0.1 to 85.45.63.25485.45.63.25516,382
18285.45.64.0/1885.45.64.1 to 85.45.127.25485.45.127.25516,382
18385.45.128.0/1885.45.128.1 to 85.45.191.25485.45.191.25516,382
18485.45.192.0/1885.45.192.1 to 85.45.255.25485.45.255.25516,382
18585.46.0.0/1885.46.0.1 to 85.46.63.25485.46.63.25516,382
18685.46.64.0/1885.46.64.1 to 85.46.127.25485.46.127.25516,382
18785.46.128.0/1885.46.128.1 to 85.46.191.25485.46.191.25516,382
18885.46.192.0/1885.46.192.1 to 85.46.255.25485.46.255.25516,382
18985.47.0.0/1885.47.0.1 to 85.47.63.25485.47.63.25516,382
19085.47.64.0/1885.47.64.1 to 85.47.127.25485.47.127.25516,382
19185.47.128.0/1885.47.128.1 to 85.47.191.25485.47.191.25516,382
19285.47.192.0/1885.47.192.1 to 85.47.255.25485.47.255.25516,382
19385.48.0.0/1885.48.0.1 to 85.48.63.25485.48.63.25516,382
19485.48.64.0/1885.48.64.1 to 85.48.127.25485.48.127.25516,382
19585.48.128.0/1885.48.128.1 to 85.48.191.25485.48.191.25516,382
19685.48.192.0/1885.48.192.1 to 85.48.255.25485.48.255.25516,382
19785.49.0.0/1885.49.0.1 to 85.49.63.25485.49.63.25516,382
19885.49.64.0/1885.49.64.1 to 85.49.127.25485.49.127.25516,382
19985.49.128.0/1885.49.128.1 to 85.49.191.25485.49.191.25516,382
20085.49.192.0/1885.49.192.1 to 85.49.255.25485.49.255.25516,382
20185.50.0.0/1885.50.0.1 to 85.50.63.25485.50.63.25516,382
20285.50.64.0/1885.50.64.1 to 85.50.127.25485.50.127.25516,382
20385.50.128.0/1885.50.128.1 to 85.50.191.25485.50.191.25516,382
20485.50.192.0/1885.50.192.1 to 85.50.255.25485.50.255.25516,382
20585.51.0.0/1885.51.0.1 to 85.51.63.25485.51.63.25516,382
20685.51.64.0/1885.51.64.1 to 85.51.127.25485.51.127.25516,382
20785.51.128.0/1885.51.128.1 to 85.51.191.25485.51.191.25516,382
20885.51.192.0/1885.51.192.1 to 85.51.255.25485.51.255.25516,382
20985.52.0.0/1885.52.0.1 to 85.52.63.25485.52.63.25516,382
21085.52.64.0/1885.52.64.1 to 85.52.127.25485.52.127.25516,382
21185.52.128.0/1885.52.128.1 to 85.52.191.25485.52.191.25516,382
21285.52.192.0/1885.52.192.1 to 85.52.255.25485.52.255.25516,382
21385.53.0.0/1885.53.0.1 to 85.53.63.25485.53.63.25516,382
21485.53.64.0/1885.53.64.1 to 85.53.127.25485.53.127.25516,382
21585.53.128.0/1885.53.128.1 to 85.53.191.25485.53.191.25516,382
21685.53.192.0/1885.53.192.1 to 85.53.255.25485.53.255.25516,382
21785.54.0.0/1885.54.0.1 to 85.54.63.25485.54.63.25516,382
21885.54.64.0/1885.54.64.1 to 85.54.127.25485.54.127.25516,382
21985.54.128.0/1885.54.128.1 to 85.54.191.25485.54.191.25516,382
22085.54.192.0/1885.54.192.1 to 85.54.255.25485.54.255.25516,382
22185.55.0.0/1885.55.0.1 to 85.55.63.25485.55.63.25516,382
22285.55.64.0/1885.55.64.1 to 85.55.127.25485.55.127.25516,382
22385.55.128.0/1885.55.128.1 to 85.55.191.25485.55.191.25516,382
22485.55.192.0/1885.55.192.1 to 85.55.255.25485.55.255.25516,382
22585.56.0.0/1885.56.0.1 to 85.56.63.25485.56.63.25516,382
22685.56.64.0/1885.56.64.1 to 85.56.127.25485.56.127.25516,382
22785.56.128.0/1885.56.128.1 to 85.56.191.25485.56.191.25516,382
22885.56.192.0/1885.56.192.1 to 85.56.255.25485.56.255.25516,382
22985.57.0.0/1885.57.0.1 to 85.57.63.25485.57.63.25516,382
23085.57.64.0/1885.57.64.1 to 85.57.127.25485.57.127.25516,382
23185.57.128.0/1885.57.128.1 to 85.57.191.25485.57.191.25516,382
23285.57.192.0/1885.57.192.1 to 85.57.255.25485.57.255.25516,382
23385.58.0.0/1885.58.0.1 to 85.58.63.25485.58.63.25516,382
23485.58.64.0/1885.58.64.1 to 85.58.127.25485.58.127.25516,382
23585.58.128.0/1885.58.128.1 to 85.58.191.25485.58.191.25516,382
23685.58.192.0/1885.58.192.1 to 85.58.255.25485.58.255.25516,382
23785.59.0.0/1885.59.0.1 to 85.59.63.25485.59.63.25516,382
23885.59.64.0/1885.59.64.1 to 85.59.127.25485.59.127.25516,382
23985.59.128.0/1885.59.128.1 to 85.59.191.25485.59.191.25516,382
24085.59.192.0/1885.59.192.1 to 85.59.255.25485.59.255.25516,382
24185.60.0.0/1885.60.0.1 to 85.60.63.25485.60.63.25516,382
24285.60.64.0/1885.60.64.1 to 85.60.127.25485.60.127.25516,382
24385.60.128.0/1885.60.128.1 to 85.60.191.25485.60.191.25516,382
24485.60.192.0/1885.60.192.1 to 85.60.255.25485.60.255.25516,382
24585.61.0.0/1885.61.0.1 to 85.61.63.25485.61.63.25516,382
24685.61.64.0/1885.61.64.1 to 85.61.127.25485.61.127.25516,382
24785.61.128.0/1885.61.128.1 to 85.61.191.25485.61.191.25516,382
24885.61.192.0/1885.61.192.1 to 85.61.255.25485.61.255.25516,382
24985.62.0.0/1885.62.0.1 to 85.62.63.25485.62.63.25516,382
25085.62.64.0/1885.62.64.1 to 85.62.127.25485.62.127.25516,382
25185.62.128.0/1885.62.128.1 to 85.62.191.25485.62.191.25516,382
25285.62.192.0/1885.62.192.1 to 85.62.255.25485.62.255.25516,382
25385.63.0.0/1885.63.0.1 to 85.63.63.25485.63.63.25516,382
25485.63.64.0/1885.63.64.1 to 85.63.127.25485.63.127.25516,382
25585.63.128.0/1885.63.128.1 to 85.63.191.25485.63.191.25516,382
25685.63.192.0/1885.63.192.1 to 85.63.255.25485.63.255.25516,382

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.