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.

Network74.240.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
74.240.0.0
Broadcast address
74.255.255.255
First usable
74.240.0.1
Last usable
74.255.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Public public
Old class
A (default /8)
As numbers
Hex 4AF00000 · Integer 1257242624 to 1258291199
Reverse DNS zones
240.74.in-addr.arpa
241.74.in-addr.arpa
242.74.in-addr.arpa
243.74.in-addr.arpa
244.74.in-addr.arpa
245.74.in-addr.arpa
246.74.in-addr.arpa
247.74.in-addr.arpa
248.74.in-addr.arpa
249.74.in-addr.arpa
250.74.in-addr.arpa
251.74.in-addr.arpa
252.74.in-addr.arpa
253.74.in-addr.arpa
254.74.in-addr.arpa
255.74.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01001010.11110000.00000000.0000000074.240.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network01001010.11110000.00000000.0000000074.240.0.0
Broadcast01001010.11111111.11111111.1111111174.255.255.255
Split into smaller subnets/22
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

74.240.0.0/12 makes 1,024 subnets of /22; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
174.240.0.0/2274.240.0.1 to 74.240.3.25474.240.3.2551,022
274.240.4.0/2274.240.4.1 to 74.240.7.25474.240.7.2551,022
374.240.8.0/2274.240.8.1 to 74.240.11.25474.240.11.2551,022
474.240.12.0/2274.240.12.1 to 74.240.15.25474.240.15.2551,022
574.240.16.0/2274.240.16.1 to 74.240.19.25474.240.19.2551,022
674.240.20.0/2274.240.20.1 to 74.240.23.25474.240.23.2551,022
774.240.24.0/2274.240.24.1 to 74.240.27.25474.240.27.2551,022
874.240.28.0/2274.240.28.1 to 74.240.31.25474.240.31.2551,022
974.240.32.0/2274.240.32.1 to 74.240.35.25474.240.35.2551,022
1074.240.36.0/2274.240.36.1 to 74.240.39.25474.240.39.2551,022
1174.240.40.0/2274.240.40.1 to 74.240.43.25474.240.43.2551,022
1274.240.44.0/2274.240.44.1 to 74.240.47.25474.240.47.2551,022
1374.240.48.0/2274.240.48.1 to 74.240.51.25474.240.51.2551,022
1474.240.52.0/2274.240.52.1 to 74.240.55.25474.240.55.2551,022
1574.240.56.0/2274.240.56.1 to 74.240.59.25474.240.59.2551,022
1674.240.60.0/2274.240.60.1 to 74.240.63.25474.240.63.2551,022
1774.240.64.0/2274.240.64.1 to 74.240.67.25474.240.67.2551,022
1874.240.68.0/2274.240.68.1 to 74.240.71.25474.240.71.2551,022
1974.240.72.0/2274.240.72.1 to 74.240.75.25474.240.75.2551,022
2074.240.76.0/2274.240.76.1 to 74.240.79.25474.240.79.2551,022
2174.240.80.0/2274.240.80.1 to 74.240.83.25474.240.83.2551,022
2274.240.84.0/2274.240.84.1 to 74.240.87.25474.240.87.2551,022
2374.240.88.0/2274.240.88.1 to 74.240.91.25474.240.91.2551,022
2474.240.92.0/2274.240.92.1 to 74.240.95.25474.240.95.2551,022
2574.240.96.0/2274.240.96.1 to 74.240.99.25474.240.99.2551,022
2674.240.100.0/2274.240.100.1 to 74.240.103.25474.240.103.2551,022
2774.240.104.0/2274.240.104.1 to 74.240.107.25474.240.107.2551,022
2874.240.108.0/2274.240.108.1 to 74.240.111.25474.240.111.2551,022
2974.240.112.0/2274.240.112.1 to 74.240.115.25474.240.115.2551,022
3074.240.116.0/2274.240.116.1 to 74.240.119.25474.240.119.2551,022
3174.240.120.0/2274.240.120.1 to 74.240.123.25474.240.123.2551,022
3274.240.124.0/2274.240.124.1 to 74.240.127.25474.240.127.2551,022
3374.240.128.0/2274.240.128.1 to 74.240.131.25474.240.131.2551,022
3474.240.132.0/2274.240.132.1 to 74.240.135.25474.240.135.2551,022
3574.240.136.0/2274.240.136.1 to 74.240.139.25474.240.139.2551,022
3674.240.140.0/2274.240.140.1 to 74.240.143.25474.240.143.2551,022
3774.240.144.0/2274.240.144.1 to 74.240.147.25474.240.147.2551,022
3874.240.148.0/2274.240.148.1 to 74.240.151.25474.240.151.2551,022
3974.240.152.0/2274.240.152.1 to 74.240.155.25474.240.155.2551,022
4074.240.156.0/2274.240.156.1 to 74.240.159.25474.240.159.2551,022
4174.240.160.0/2274.240.160.1 to 74.240.163.25474.240.163.2551,022
4274.240.164.0/2274.240.164.1 to 74.240.167.25474.240.167.2551,022
4374.240.168.0/2274.240.168.1 to 74.240.171.25474.240.171.2551,022
4474.240.172.0/2274.240.172.1 to 74.240.175.25474.240.175.2551,022
4574.240.176.0/2274.240.176.1 to 74.240.179.25474.240.179.2551,022
4674.240.180.0/2274.240.180.1 to 74.240.183.25474.240.183.2551,022
4774.240.184.0/2274.240.184.1 to 74.240.187.25474.240.187.2551,022
4874.240.188.0/2274.240.188.1 to 74.240.191.25474.240.191.2551,022
4974.240.192.0/2274.240.192.1 to 74.240.195.25474.240.195.2551,022
5074.240.196.0/2274.240.196.1 to 74.240.199.25474.240.199.2551,022
5174.240.200.0/2274.240.200.1 to 74.240.203.25474.240.203.2551,022
5274.240.204.0/2274.240.204.1 to 74.240.207.25474.240.207.2551,022
5374.240.208.0/2274.240.208.1 to 74.240.211.25474.240.211.2551,022
5474.240.212.0/2274.240.212.1 to 74.240.215.25474.240.215.2551,022
5574.240.216.0/2274.240.216.1 to 74.240.219.25474.240.219.2551,022
5674.240.220.0/2274.240.220.1 to 74.240.223.25474.240.223.2551,022
5774.240.224.0/2274.240.224.1 to 74.240.227.25474.240.227.2551,022
5874.240.228.0/2274.240.228.1 to 74.240.231.25474.240.231.2551,022
5974.240.232.0/2274.240.232.1 to 74.240.235.25474.240.235.2551,022
6074.240.236.0/2274.240.236.1 to 74.240.239.25474.240.239.2551,022
6174.240.240.0/2274.240.240.1 to 74.240.243.25474.240.243.2551,022
6274.240.244.0/2274.240.244.1 to 74.240.247.25474.240.247.2551,022
6374.240.248.0/2274.240.248.1 to 74.240.251.25474.240.251.2551,022
6474.240.252.0/2274.240.252.1 to 74.240.255.25474.240.255.2551,022
6574.241.0.0/2274.241.0.1 to 74.241.3.25474.241.3.2551,022
6674.241.4.0/2274.241.4.1 to 74.241.7.25474.241.7.2551,022
6774.241.8.0/2274.241.8.1 to 74.241.11.25474.241.11.2551,022
6874.241.12.0/2274.241.12.1 to 74.241.15.25474.241.15.2551,022
6974.241.16.0/2274.241.16.1 to 74.241.19.25474.241.19.2551,022
7074.241.20.0/2274.241.20.1 to 74.241.23.25474.241.23.2551,022
7174.241.24.0/2274.241.24.1 to 74.241.27.25474.241.27.2551,022
7274.241.28.0/2274.241.28.1 to 74.241.31.25474.241.31.2551,022
7374.241.32.0/2274.241.32.1 to 74.241.35.25474.241.35.2551,022
7474.241.36.0/2274.241.36.1 to 74.241.39.25474.241.39.2551,022
7574.241.40.0/2274.241.40.1 to 74.241.43.25474.241.43.2551,022
7674.241.44.0/2274.241.44.1 to 74.241.47.25474.241.47.2551,022
7774.241.48.0/2274.241.48.1 to 74.241.51.25474.241.51.2551,022
7874.241.52.0/2274.241.52.1 to 74.241.55.25474.241.55.2551,022
7974.241.56.0/2274.241.56.1 to 74.241.59.25474.241.59.2551,022
8074.241.60.0/2274.241.60.1 to 74.241.63.25474.241.63.2551,022
8174.241.64.0/2274.241.64.1 to 74.241.67.25474.241.67.2551,022
8274.241.68.0/2274.241.68.1 to 74.241.71.25474.241.71.2551,022
8374.241.72.0/2274.241.72.1 to 74.241.75.25474.241.75.2551,022
8474.241.76.0/2274.241.76.1 to 74.241.79.25474.241.79.2551,022
8574.241.80.0/2274.241.80.1 to 74.241.83.25474.241.83.2551,022
8674.241.84.0/2274.241.84.1 to 74.241.87.25474.241.87.2551,022
8774.241.88.0/2274.241.88.1 to 74.241.91.25474.241.91.2551,022
8874.241.92.0/2274.241.92.1 to 74.241.95.25474.241.95.2551,022
8974.241.96.0/2274.241.96.1 to 74.241.99.25474.241.99.2551,022
9074.241.100.0/2274.241.100.1 to 74.241.103.25474.241.103.2551,022
9174.241.104.0/2274.241.104.1 to 74.241.107.25474.241.107.2551,022
9274.241.108.0/2274.241.108.1 to 74.241.111.25474.241.111.2551,022
9374.241.112.0/2274.241.112.1 to 74.241.115.25474.241.115.2551,022
9474.241.116.0/2274.241.116.1 to 74.241.119.25474.241.119.2551,022
9574.241.120.0/2274.241.120.1 to 74.241.123.25474.241.123.2551,022
9674.241.124.0/2274.241.124.1 to 74.241.127.25474.241.127.2551,022
9774.241.128.0/2274.241.128.1 to 74.241.131.25474.241.131.2551,022
9874.241.132.0/2274.241.132.1 to 74.241.135.25474.241.135.2551,022
9974.241.136.0/2274.241.136.1 to 74.241.139.25474.241.139.2551,022
10074.241.140.0/2274.241.140.1 to 74.241.143.25474.241.143.2551,022
10174.241.144.0/2274.241.144.1 to 74.241.147.25474.241.147.2551,022
10274.241.148.0/2274.241.148.1 to 74.241.151.25474.241.151.2551,022
10374.241.152.0/2274.241.152.1 to 74.241.155.25474.241.155.2551,022
10474.241.156.0/2274.241.156.1 to 74.241.159.25474.241.159.2551,022
10574.241.160.0/2274.241.160.1 to 74.241.163.25474.241.163.2551,022
10674.241.164.0/2274.241.164.1 to 74.241.167.25474.241.167.2551,022
10774.241.168.0/2274.241.168.1 to 74.241.171.25474.241.171.2551,022
10874.241.172.0/2274.241.172.1 to 74.241.175.25474.241.175.2551,022
10974.241.176.0/2274.241.176.1 to 74.241.179.25474.241.179.2551,022
11074.241.180.0/2274.241.180.1 to 74.241.183.25474.241.183.2551,022
11174.241.184.0/2274.241.184.1 to 74.241.187.25474.241.187.2551,022
11274.241.188.0/2274.241.188.1 to 74.241.191.25474.241.191.2551,022
11374.241.192.0/2274.241.192.1 to 74.241.195.25474.241.195.2551,022
11474.241.196.0/2274.241.196.1 to 74.241.199.25474.241.199.2551,022
11574.241.200.0/2274.241.200.1 to 74.241.203.25474.241.203.2551,022
11674.241.204.0/2274.241.204.1 to 74.241.207.25474.241.207.2551,022
11774.241.208.0/2274.241.208.1 to 74.241.211.25474.241.211.2551,022
11874.241.212.0/2274.241.212.1 to 74.241.215.25474.241.215.2551,022
11974.241.216.0/2274.241.216.1 to 74.241.219.25474.241.219.2551,022
12074.241.220.0/2274.241.220.1 to 74.241.223.25474.241.223.2551,022
12174.241.224.0/2274.241.224.1 to 74.241.227.25474.241.227.2551,022
12274.241.228.0/2274.241.228.1 to 74.241.231.25474.241.231.2551,022
12374.241.232.0/2274.241.232.1 to 74.241.235.25474.241.235.2551,022
12474.241.236.0/2274.241.236.1 to 74.241.239.25474.241.239.2551,022
12574.241.240.0/2274.241.240.1 to 74.241.243.25474.241.243.2551,022
12674.241.244.0/2274.241.244.1 to 74.241.247.25474.241.247.2551,022
12774.241.248.0/2274.241.248.1 to 74.241.251.25474.241.251.2551,022
12874.241.252.0/2274.241.252.1 to 74.241.255.25474.241.255.2551,022
12974.242.0.0/2274.242.0.1 to 74.242.3.25474.242.3.2551,022
13074.242.4.0/2274.242.4.1 to 74.242.7.25474.242.7.2551,022
13174.242.8.0/2274.242.8.1 to 74.242.11.25474.242.11.2551,022
13274.242.12.0/2274.242.12.1 to 74.242.15.25474.242.15.2551,022
13374.242.16.0/2274.242.16.1 to 74.242.19.25474.242.19.2551,022
13474.242.20.0/2274.242.20.1 to 74.242.23.25474.242.23.2551,022
13574.242.24.0/2274.242.24.1 to 74.242.27.25474.242.27.2551,022
13674.242.28.0/2274.242.28.1 to 74.242.31.25474.242.31.2551,022
13774.242.32.0/2274.242.32.1 to 74.242.35.25474.242.35.2551,022
13874.242.36.0/2274.242.36.1 to 74.242.39.25474.242.39.2551,022
13974.242.40.0/2274.242.40.1 to 74.242.43.25474.242.43.2551,022
14074.242.44.0/2274.242.44.1 to 74.242.47.25474.242.47.2551,022
14174.242.48.0/2274.242.48.1 to 74.242.51.25474.242.51.2551,022
14274.242.52.0/2274.242.52.1 to 74.242.55.25474.242.55.2551,022
14374.242.56.0/2274.242.56.1 to 74.242.59.25474.242.59.2551,022
14474.242.60.0/2274.242.60.1 to 74.242.63.25474.242.63.2551,022
14574.242.64.0/2274.242.64.1 to 74.242.67.25474.242.67.2551,022
14674.242.68.0/2274.242.68.1 to 74.242.71.25474.242.71.2551,022
14774.242.72.0/2274.242.72.1 to 74.242.75.25474.242.75.2551,022
14874.242.76.0/2274.242.76.1 to 74.242.79.25474.242.79.2551,022
14974.242.80.0/2274.242.80.1 to 74.242.83.25474.242.83.2551,022
15074.242.84.0/2274.242.84.1 to 74.242.87.25474.242.87.2551,022
15174.242.88.0/2274.242.88.1 to 74.242.91.25474.242.91.2551,022
15274.242.92.0/2274.242.92.1 to 74.242.95.25474.242.95.2551,022
15374.242.96.0/2274.242.96.1 to 74.242.99.25474.242.99.2551,022
15474.242.100.0/2274.242.100.1 to 74.242.103.25474.242.103.2551,022
15574.242.104.0/2274.242.104.1 to 74.242.107.25474.242.107.2551,022
15674.242.108.0/2274.242.108.1 to 74.242.111.25474.242.111.2551,022
15774.242.112.0/2274.242.112.1 to 74.242.115.25474.242.115.2551,022
15874.242.116.0/2274.242.116.1 to 74.242.119.25474.242.119.2551,022
15974.242.120.0/2274.242.120.1 to 74.242.123.25474.242.123.2551,022
16074.242.124.0/2274.242.124.1 to 74.242.127.25474.242.127.2551,022
16174.242.128.0/2274.242.128.1 to 74.242.131.25474.242.131.2551,022
16274.242.132.0/2274.242.132.1 to 74.242.135.25474.242.135.2551,022
16374.242.136.0/2274.242.136.1 to 74.242.139.25474.242.139.2551,022
16474.242.140.0/2274.242.140.1 to 74.242.143.25474.242.143.2551,022
16574.242.144.0/2274.242.144.1 to 74.242.147.25474.242.147.2551,022
16674.242.148.0/2274.242.148.1 to 74.242.151.25474.242.151.2551,022
16774.242.152.0/2274.242.152.1 to 74.242.155.25474.242.155.2551,022
16874.242.156.0/2274.242.156.1 to 74.242.159.25474.242.159.2551,022
16974.242.160.0/2274.242.160.1 to 74.242.163.25474.242.163.2551,022
17074.242.164.0/2274.242.164.1 to 74.242.167.25474.242.167.2551,022
17174.242.168.0/2274.242.168.1 to 74.242.171.25474.242.171.2551,022
17274.242.172.0/2274.242.172.1 to 74.242.175.25474.242.175.2551,022
17374.242.176.0/2274.242.176.1 to 74.242.179.25474.242.179.2551,022
17474.242.180.0/2274.242.180.1 to 74.242.183.25474.242.183.2551,022
17574.242.184.0/2274.242.184.1 to 74.242.187.25474.242.187.2551,022
17674.242.188.0/2274.242.188.1 to 74.242.191.25474.242.191.2551,022
17774.242.192.0/2274.242.192.1 to 74.242.195.25474.242.195.2551,022
17874.242.196.0/2274.242.196.1 to 74.242.199.25474.242.199.2551,022
17974.242.200.0/2274.242.200.1 to 74.242.203.25474.242.203.2551,022
18074.242.204.0/2274.242.204.1 to 74.242.207.25474.242.207.2551,022
18174.242.208.0/2274.242.208.1 to 74.242.211.25474.242.211.2551,022
18274.242.212.0/2274.242.212.1 to 74.242.215.25474.242.215.2551,022
18374.242.216.0/2274.242.216.1 to 74.242.219.25474.242.219.2551,022
18474.242.220.0/2274.242.220.1 to 74.242.223.25474.242.223.2551,022
18574.242.224.0/2274.242.224.1 to 74.242.227.25474.242.227.2551,022
18674.242.228.0/2274.242.228.1 to 74.242.231.25474.242.231.2551,022
18774.242.232.0/2274.242.232.1 to 74.242.235.25474.242.235.2551,022
18874.242.236.0/2274.242.236.1 to 74.242.239.25474.242.239.2551,022
18974.242.240.0/2274.242.240.1 to 74.242.243.25474.242.243.2551,022
19074.242.244.0/2274.242.244.1 to 74.242.247.25474.242.247.2551,022
19174.242.248.0/2274.242.248.1 to 74.242.251.25474.242.251.2551,022
19274.242.252.0/2274.242.252.1 to 74.242.255.25474.242.255.2551,022
19374.243.0.0/2274.243.0.1 to 74.243.3.25474.243.3.2551,022
19474.243.4.0/2274.243.4.1 to 74.243.7.25474.243.7.2551,022
19574.243.8.0/2274.243.8.1 to 74.243.11.25474.243.11.2551,022
19674.243.12.0/2274.243.12.1 to 74.243.15.25474.243.15.2551,022
19774.243.16.0/2274.243.16.1 to 74.243.19.25474.243.19.2551,022
19874.243.20.0/2274.243.20.1 to 74.243.23.25474.243.23.2551,022
19974.243.24.0/2274.243.24.1 to 74.243.27.25474.243.27.2551,022
20074.243.28.0/2274.243.28.1 to 74.243.31.25474.243.31.2551,022
20174.243.32.0/2274.243.32.1 to 74.243.35.25474.243.35.2551,022
20274.243.36.0/2274.243.36.1 to 74.243.39.25474.243.39.2551,022
20374.243.40.0/2274.243.40.1 to 74.243.43.25474.243.43.2551,022
20474.243.44.0/2274.243.44.1 to 74.243.47.25474.243.47.2551,022
20574.243.48.0/2274.243.48.1 to 74.243.51.25474.243.51.2551,022
20674.243.52.0/2274.243.52.1 to 74.243.55.25474.243.55.2551,022
20774.243.56.0/2274.243.56.1 to 74.243.59.25474.243.59.2551,022
20874.243.60.0/2274.243.60.1 to 74.243.63.25474.243.63.2551,022
20974.243.64.0/2274.243.64.1 to 74.243.67.25474.243.67.2551,022
21074.243.68.0/2274.243.68.1 to 74.243.71.25474.243.71.2551,022
21174.243.72.0/2274.243.72.1 to 74.243.75.25474.243.75.2551,022
21274.243.76.0/2274.243.76.1 to 74.243.79.25474.243.79.2551,022
21374.243.80.0/2274.243.80.1 to 74.243.83.25474.243.83.2551,022
21474.243.84.0/2274.243.84.1 to 74.243.87.25474.243.87.2551,022
21574.243.88.0/2274.243.88.1 to 74.243.91.25474.243.91.2551,022
21674.243.92.0/2274.243.92.1 to 74.243.95.25474.243.95.2551,022
21774.243.96.0/2274.243.96.1 to 74.243.99.25474.243.99.2551,022
21874.243.100.0/2274.243.100.1 to 74.243.103.25474.243.103.2551,022
21974.243.104.0/2274.243.104.1 to 74.243.107.25474.243.107.2551,022
22074.243.108.0/2274.243.108.1 to 74.243.111.25474.243.111.2551,022
22174.243.112.0/2274.243.112.1 to 74.243.115.25474.243.115.2551,022
22274.243.116.0/2274.243.116.1 to 74.243.119.25474.243.119.2551,022
22374.243.120.0/2274.243.120.1 to 74.243.123.25474.243.123.2551,022
22474.243.124.0/2274.243.124.1 to 74.243.127.25474.243.127.2551,022
22574.243.128.0/2274.243.128.1 to 74.243.131.25474.243.131.2551,022
22674.243.132.0/2274.243.132.1 to 74.243.135.25474.243.135.2551,022
22774.243.136.0/2274.243.136.1 to 74.243.139.25474.243.139.2551,022
22874.243.140.0/2274.243.140.1 to 74.243.143.25474.243.143.2551,022
22974.243.144.0/2274.243.144.1 to 74.243.147.25474.243.147.2551,022
23074.243.148.0/2274.243.148.1 to 74.243.151.25474.243.151.2551,022
23174.243.152.0/2274.243.152.1 to 74.243.155.25474.243.155.2551,022
23274.243.156.0/2274.243.156.1 to 74.243.159.25474.243.159.2551,022
23374.243.160.0/2274.243.160.1 to 74.243.163.25474.243.163.2551,022
23474.243.164.0/2274.243.164.1 to 74.243.167.25474.243.167.2551,022
23574.243.168.0/2274.243.168.1 to 74.243.171.25474.243.171.2551,022
23674.243.172.0/2274.243.172.1 to 74.243.175.25474.243.175.2551,022
23774.243.176.0/2274.243.176.1 to 74.243.179.25474.243.179.2551,022
23874.243.180.0/2274.243.180.1 to 74.243.183.25474.243.183.2551,022
23974.243.184.0/2274.243.184.1 to 74.243.187.25474.243.187.2551,022
24074.243.188.0/2274.243.188.1 to 74.243.191.25474.243.191.2551,022
24174.243.192.0/2274.243.192.1 to 74.243.195.25474.243.195.2551,022
24274.243.196.0/2274.243.196.1 to 74.243.199.25474.243.199.2551,022
24374.243.200.0/2274.243.200.1 to 74.243.203.25474.243.203.2551,022
24474.243.204.0/2274.243.204.1 to 74.243.207.25474.243.207.2551,022
24574.243.208.0/2274.243.208.1 to 74.243.211.25474.243.211.2551,022
24674.243.212.0/2274.243.212.1 to 74.243.215.25474.243.215.2551,022
24774.243.216.0/2274.243.216.1 to 74.243.219.25474.243.219.2551,022
24874.243.220.0/2274.243.220.1 to 74.243.223.25474.243.223.2551,022
24974.243.224.0/2274.243.224.1 to 74.243.227.25474.243.227.2551,022
25074.243.228.0/2274.243.228.1 to 74.243.231.25474.243.231.2551,022
25174.243.232.0/2274.243.232.1 to 74.243.235.25474.243.235.2551,022
25274.243.236.0/2274.243.236.1 to 74.243.239.25474.243.239.2551,022
25374.243.240.0/2274.243.240.1 to 74.243.243.25474.243.243.2551,022
25474.243.244.0/2274.243.244.1 to 74.243.247.25474.243.247.2551,022
25574.243.248.0/2274.243.248.1 to 74.243.251.25474.243.251.2551,022
25674.243.252.0/2274.243.252.1 to 74.243.255.25474.243.255.2551,022

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.