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.

Network36.0.0.0/6
Usable hosts67,108,862
Subnet mask252.0.0.0
Addresses67,108,864
Network address
36.0.0.0
Broadcast address
39.255.255.255
First usable
36.0.0.1
Last usable
39.255.255.254
Usable hosts
67,108,862 (67,108,864 less the network and broadcast addresses)
Subnet mask
252.0.0.0
Wildcard mask
3.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/6
Type
Public public
Old class
A (default /8)
As numbers
Hex 24000000 · Integer 603979776 to 671088639
Reverse DNS zones
36.in-addr.arpa
37.in-addr.arpa
38.in-addr.arpa
39.in-addr.arpa
/6 is not on a 8-bit boundary, so it takes 4 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00100100.00000000.00000000.0000000036.0.0.0
Subnet mask11111100.00000000.00000000.00000000252.0.0.0
Network00100100.00000000.00000000.0000000036.0.0.0
Broadcast00100111.11111111.11111111.1111111139.255.255.255
Split into smaller subnets/16
/7 (2)/8 (4)/9 (8)/10 (16)/11 (32)/12 (64)/13 (128)/14 (256)/15 (512)/16 (1,024)/17 (2,048)/18 (4,096)

36.0.0.0/6 makes 1,024 subnets of /16; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
136.0.0.0/1636.0.0.1 to 36.0.255.25436.0.255.25565,534
236.1.0.0/1636.1.0.1 to 36.1.255.25436.1.255.25565,534
336.2.0.0/1636.2.0.1 to 36.2.255.25436.2.255.25565,534
436.3.0.0/1636.3.0.1 to 36.3.255.25436.3.255.25565,534
536.4.0.0/1636.4.0.1 to 36.4.255.25436.4.255.25565,534
636.5.0.0/1636.5.0.1 to 36.5.255.25436.5.255.25565,534
736.6.0.0/1636.6.0.1 to 36.6.255.25436.6.255.25565,534
836.7.0.0/1636.7.0.1 to 36.7.255.25436.7.255.25565,534
936.8.0.0/1636.8.0.1 to 36.8.255.25436.8.255.25565,534
1036.9.0.0/1636.9.0.1 to 36.9.255.25436.9.255.25565,534
1136.10.0.0/1636.10.0.1 to 36.10.255.25436.10.255.25565,534
1236.11.0.0/1636.11.0.1 to 36.11.255.25436.11.255.25565,534
1336.12.0.0/1636.12.0.1 to 36.12.255.25436.12.255.25565,534
1436.13.0.0/1636.13.0.1 to 36.13.255.25436.13.255.25565,534
1536.14.0.0/1636.14.0.1 to 36.14.255.25436.14.255.25565,534
1636.15.0.0/1636.15.0.1 to 36.15.255.25436.15.255.25565,534
1736.16.0.0/1636.16.0.1 to 36.16.255.25436.16.255.25565,534
1836.17.0.0/1636.17.0.1 to 36.17.255.25436.17.255.25565,534
1936.18.0.0/1636.18.0.1 to 36.18.255.25436.18.255.25565,534
2036.19.0.0/1636.19.0.1 to 36.19.255.25436.19.255.25565,534
2136.20.0.0/1636.20.0.1 to 36.20.255.25436.20.255.25565,534
2236.21.0.0/1636.21.0.1 to 36.21.255.25436.21.255.25565,534
2336.22.0.0/1636.22.0.1 to 36.22.255.25436.22.255.25565,534
2436.23.0.0/1636.23.0.1 to 36.23.255.25436.23.255.25565,534
2536.24.0.0/1636.24.0.1 to 36.24.255.25436.24.255.25565,534
2636.25.0.0/1636.25.0.1 to 36.25.255.25436.25.255.25565,534
2736.26.0.0/1636.26.0.1 to 36.26.255.25436.26.255.25565,534
2836.27.0.0/1636.27.0.1 to 36.27.255.25436.27.255.25565,534
2936.28.0.0/1636.28.0.1 to 36.28.255.25436.28.255.25565,534
3036.29.0.0/1636.29.0.1 to 36.29.255.25436.29.255.25565,534
3136.30.0.0/1636.30.0.1 to 36.30.255.25436.30.255.25565,534
3236.31.0.0/1636.31.0.1 to 36.31.255.25436.31.255.25565,534
3336.32.0.0/1636.32.0.1 to 36.32.255.25436.32.255.25565,534
3436.33.0.0/1636.33.0.1 to 36.33.255.25436.33.255.25565,534
3536.34.0.0/1636.34.0.1 to 36.34.255.25436.34.255.25565,534
3636.35.0.0/1636.35.0.1 to 36.35.255.25436.35.255.25565,534
3736.36.0.0/1636.36.0.1 to 36.36.255.25436.36.255.25565,534
3836.37.0.0/1636.37.0.1 to 36.37.255.25436.37.255.25565,534
3936.38.0.0/1636.38.0.1 to 36.38.255.25436.38.255.25565,534
4036.39.0.0/1636.39.0.1 to 36.39.255.25436.39.255.25565,534
4136.40.0.0/1636.40.0.1 to 36.40.255.25436.40.255.25565,534
4236.41.0.0/1636.41.0.1 to 36.41.255.25436.41.255.25565,534
4336.42.0.0/1636.42.0.1 to 36.42.255.25436.42.255.25565,534
4436.43.0.0/1636.43.0.1 to 36.43.255.25436.43.255.25565,534
4536.44.0.0/1636.44.0.1 to 36.44.255.25436.44.255.25565,534
4636.45.0.0/1636.45.0.1 to 36.45.255.25436.45.255.25565,534
4736.46.0.0/1636.46.0.1 to 36.46.255.25436.46.255.25565,534
4836.47.0.0/1636.47.0.1 to 36.47.255.25436.47.255.25565,534
4936.48.0.0/1636.48.0.1 to 36.48.255.25436.48.255.25565,534
5036.49.0.0/1636.49.0.1 to 36.49.255.25436.49.255.25565,534
5136.50.0.0/1636.50.0.1 to 36.50.255.25436.50.255.25565,534
5236.51.0.0/1636.51.0.1 to 36.51.255.25436.51.255.25565,534
5336.52.0.0/1636.52.0.1 to 36.52.255.25436.52.255.25565,534
5436.53.0.0/1636.53.0.1 to 36.53.255.25436.53.255.25565,534
5536.54.0.0/1636.54.0.1 to 36.54.255.25436.54.255.25565,534
5636.55.0.0/1636.55.0.1 to 36.55.255.25436.55.255.25565,534
5736.56.0.0/1636.56.0.1 to 36.56.255.25436.56.255.25565,534
5836.57.0.0/1636.57.0.1 to 36.57.255.25436.57.255.25565,534
5936.58.0.0/1636.58.0.1 to 36.58.255.25436.58.255.25565,534
6036.59.0.0/1636.59.0.1 to 36.59.255.25436.59.255.25565,534
6136.60.0.0/1636.60.0.1 to 36.60.255.25436.60.255.25565,534
6236.61.0.0/1636.61.0.1 to 36.61.255.25436.61.255.25565,534
6336.62.0.0/1636.62.0.1 to 36.62.255.25436.62.255.25565,534
6436.63.0.0/1636.63.0.1 to 36.63.255.25436.63.255.25565,534
6536.64.0.0/1636.64.0.1 to 36.64.255.25436.64.255.25565,534
6636.65.0.0/1636.65.0.1 to 36.65.255.25436.65.255.25565,534
6736.66.0.0/1636.66.0.1 to 36.66.255.25436.66.255.25565,534
6836.67.0.0/1636.67.0.1 to 36.67.255.25436.67.255.25565,534
6936.68.0.0/1636.68.0.1 to 36.68.255.25436.68.255.25565,534
7036.69.0.0/1636.69.0.1 to 36.69.255.25436.69.255.25565,534
7136.70.0.0/1636.70.0.1 to 36.70.255.25436.70.255.25565,534
7236.71.0.0/1636.71.0.1 to 36.71.255.25436.71.255.25565,534
7336.72.0.0/1636.72.0.1 to 36.72.255.25436.72.255.25565,534
7436.73.0.0/1636.73.0.1 to 36.73.255.25436.73.255.25565,534
7536.74.0.0/1636.74.0.1 to 36.74.255.25436.74.255.25565,534
7636.75.0.0/1636.75.0.1 to 36.75.255.25436.75.255.25565,534
7736.76.0.0/1636.76.0.1 to 36.76.255.25436.76.255.25565,534
7836.77.0.0/1636.77.0.1 to 36.77.255.25436.77.255.25565,534
7936.78.0.0/1636.78.0.1 to 36.78.255.25436.78.255.25565,534
8036.79.0.0/1636.79.0.1 to 36.79.255.25436.79.255.25565,534
8136.80.0.0/1636.80.0.1 to 36.80.255.25436.80.255.25565,534
8236.81.0.0/1636.81.0.1 to 36.81.255.25436.81.255.25565,534
8336.82.0.0/1636.82.0.1 to 36.82.255.25436.82.255.25565,534
8436.83.0.0/1636.83.0.1 to 36.83.255.25436.83.255.25565,534
8536.84.0.0/1636.84.0.1 to 36.84.255.25436.84.255.25565,534
8636.85.0.0/1636.85.0.1 to 36.85.255.25436.85.255.25565,534
8736.86.0.0/1636.86.0.1 to 36.86.255.25436.86.255.25565,534
8836.87.0.0/1636.87.0.1 to 36.87.255.25436.87.255.25565,534
8936.88.0.0/1636.88.0.1 to 36.88.255.25436.88.255.25565,534
9036.89.0.0/1636.89.0.1 to 36.89.255.25436.89.255.25565,534
9136.90.0.0/1636.90.0.1 to 36.90.255.25436.90.255.25565,534
9236.91.0.0/1636.91.0.1 to 36.91.255.25436.91.255.25565,534
9336.92.0.0/1636.92.0.1 to 36.92.255.25436.92.255.25565,534
9436.93.0.0/1636.93.0.1 to 36.93.255.25436.93.255.25565,534
9536.94.0.0/1636.94.0.1 to 36.94.255.25436.94.255.25565,534
9636.95.0.0/1636.95.0.1 to 36.95.255.25436.95.255.25565,534
9736.96.0.0/1636.96.0.1 to 36.96.255.25436.96.255.25565,534
9836.97.0.0/1636.97.0.1 to 36.97.255.25436.97.255.25565,534
9936.98.0.0/1636.98.0.1 to 36.98.255.25436.98.255.25565,534
10036.99.0.0/1636.99.0.1 to 36.99.255.25436.99.255.25565,534
10136.100.0.0/1636.100.0.1 to 36.100.255.25436.100.255.25565,534
10236.101.0.0/1636.101.0.1 to 36.101.255.25436.101.255.25565,534
10336.102.0.0/1636.102.0.1 to 36.102.255.25436.102.255.25565,534
10436.103.0.0/1636.103.0.1 to 36.103.255.25436.103.255.25565,534
10536.104.0.0/1636.104.0.1 to 36.104.255.25436.104.255.25565,534
10636.105.0.0/1636.105.0.1 to 36.105.255.25436.105.255.25565,534
10736.106.0.0/1636.106.0.1 to 36.106.255.25436.106.255.25565,534
10836.107.0.0/1636.107.0.1 to 36.107.255.25436.107.255.25565,534
10936.108.0.0/1636.108.0.1 to 36.108.255.25436.108.255.25565,534
11036.109.0.0/1636.109.0.1 to 36.109.255.25436.109.255.25565,534
11136.110.0.0/1636.110.0.1 to 36.110.255.25436.110.255.25565,534
11236.111.0.0/1636.111.0.1 to 36.111.255.25436.111.255.25565,534
11336.112.0.0/1636.112.0.1 to 36.112.255.25436.112.255.25565,534
11436.113.0.0/1636.113.0.1 to 36.113.255.25436.113.255.25565,534
11536.114.0.0/1636.114.0.1 to 36.114.255.25436.114.255.25565,534
11636.115.0.0/1636.115.0.1 to 36.115.255.25436.115.255.25565,534
11736.116.0.0/1636.116.0.1 to 36.116.255.25436.116.255.25565,534
11836.117.0.0/1636.117.0.1 to 36.117.255.25436.117.255.25565,534
11936.118.0.0/1636.118.0.1 to 36.118.255.25436.118.255.25565,534
12036.119.0.0/1636.119.0.1 to 36.119.255.25436.119.255.25565,534
12136.120.0.0/1636.120.0.1 to 36.120.255.25436.120.255.25565,534
12236.121.0.0/1636.121.0.1 to 36.121.255.25436.121.255.25565,534
12336.122.0.0/1636.122.0.1 to 36.122.255.25436.122.255.25565,534
12436.123.0.0/1636.123.0.1 to 36.123.255.25436.123.255.25565,534
12536.124.0.0/1636.124.0.1 to 36.124.255.25436.124.255.25565,534
12636.125.0.0/1636.125.0.1 to 36.125.255.25436.125.255.25565,534
12736.126.0.0/1636.126.0.1 to 36.126.255.25436.126.255.25565,534
12836.127.0.0/1636.127.0.1 to 36.127.255.25436.127.255.25565,534
12936.128.0.0/1636.128.0.1 to 36.128.255.25436.128.255.25565,534
13036.129.0.0/1636.129.0.1 to 36.129.255.25436.129.255.25565,534
13136.130.0.0/1636.130.0.1 to 36.130.255.25436.130.255.25565,534
13236.131.0.0/1636.131.0.1 to 36.131.255.25436.131.255.25565,534
13336.132.0.0/1636.132.0.1 to 36.132.255.25436.132.255.25565,534
13436.133.0.0/1636.133.0.1 to 36.133.255.25436.133.255.25565,534
13536.134.0.0/1636.134.0.1 to 36.134.255.25436.134.255.25565,534
13636.135.0.0/1636.135.0.1 to 36.135.255.25436.135.255.25565,534
13736.136.0.0/1636.136.0.1 to 36.136.255.25436.136.255.25565,534
13836.137.0.0/1636.137.0.1 to 36.137.255.25436.137.255.25565,534
13936.138.0.0/1636.138.0.1 to 36.138.255.25436.138.255.25565,534
14036.139.0.0/1636.139.0.1 to 36.139.255.25436.139.255.25565,534
14136.140.0.0/1636.140.0.1 to 36.140.255.25436.140.255.25565,534
14236.141.0.0/1636.141.0.1 to 36.141.255.25436.141.255.25565,534
14336.142.0.0/1636.142.0.1 to 36.142.255.25436.142.255.25565,534
14436.143.0.0/1636.143.0.1 to 36.143.255.25436.143.255.25565,534
14536.144.0.0/1636.144.0.1 to 36.144.255.25436.144.255.25565,534
14636.145.0.0/1636.145.0.1 to 36.145.255.25436.145.255.25565,534
14736.146.0.0/1636.146.0.1 to 36.146.255.25436.146.255.25565,534
14836.147.0.0/1636.147.0.1 to 36.147.255.25436.147.255.25565,534
14936.148.0.0/1636.148.0.1 to 36.148.255.25436.148.255.25565,534
15036.149.0.0/1636.149.0.1 to 36.149.255.25436.149.255.25565,534
15136.150.0.0/1636.150.0.1 to 36.150.255.25436.150.255.25565,534
15236.151.0.0/1636.151.0.1 to 36.151.255.25436.151.255.25565,534
15336.152.0.0/1636.152.0.1 to 36.152.255.25436.152.255.25565,534
15436.153.0.0/1636.153.0.1 to 36.153.255.25436.153.255.25565,534
15536.154.0.0/1636.154.0.1 to 36.154.255.25436.154.255.25565,534
15636.155.0.0/1636.155.0.1 to 36.155.255.25436.155.255.25565,534
15736.156.0.0/1636.156.0.1 to 36.156.255.25436.156.255.25565,534
15836.157.0.0/1636.157.0.1 to 36.157.255.25436.157.255.25565,534
15936.158.0.0/1636.158.0.1 to 36.158.255.25436.158.255.25565,534
16036.159.0.0/1636.159.0.1 to 36.159.255.25436.159.255.25565,534
16136.160.0.0/1636.160.0.1 to 36.160.255.25436.160.255.25565,534
16236.161.0.0/1636.161.0.1 to 36.161.255.25436.161.255.25565,534
16336.162.0.0/1636.162.0.1 to 36.162.255.25436.162.255.25565,534
16436.163.0.0/1636.163.0.1 to 36.163.255.25436.163.255.25565,534
16536.164.0.0/1636.164.0.1 to 36.164.255.25436.164.255.25565,534
16636.165.0.0/1636.165.0.1 to 36.165.255.25436.165.255.25565,534
16736.166.0.0/1636.166.0.1 to 36.166.255.25436.166.255.25565,534
16836.167.0.0/1636.167.0.1 to 36.167.255.25436.167.255.25565,534
16936.168.0.0/1636.168.0.1 to 36.168.255.25436.168.255.25565,534
17036.169.0.0/1636.169.0.1 to 36.169.255.25436.169.255.25565,534
17136.170.0.0/1636.170.0.1 to 36.170.255.25436.170.255.25565,534
17236.171.0.0/1636.171.0.1 to 36.171.255.25436.171.255.25565,534
17336.172.0.0/1636.172.0.1 to 36.172.255.25436.172.255.25565,534
17436.173.0.0/1636.173.0.1 to 36.173.255.25436.173.255.25565,534
17536.174.0.0/1636.174.0.1 to 36.174.255.25436.174.255.25565,534
17636.175.0.0/1636.175.0.1 to 36.175.255.25436.175.255.25565,534
17736.176.0.0/1636.176.0.1 to 36.176.255.25436.176.255.25565,534
17836.177.0.0/1636.177.0.1 to 36.177.255.25436.177.255.25565,534
17936.178.0.0/1636.178.0.1 to 36.178.255.25436.178.255.25565,534
18036.179.0.0/1636.179.0.1 to 36.179.255.25436.179.255.25565,534
18136.180.0.0/1636.180.0.1 to 36.180.255.25436.180.255.25565,534
18236.181.0.0/1636.181.0.1 to 36.181.255.25436.181.255.25565,534
18336.182.0.0/1636.182.0.1 to 36.182.255.25436.182.255.25565,534
18436.183.0.0/1636.183.0.1 to 36.183.255.25436.183.255.25565,534
18536.184.0.0/1636.184.0.1 to 36.184.255.25436.184.255.25565,534
18636.185.0.0/1636.185.0.1 to 36.185.255.25436.185.255.25565,534
18736.186.0.0/1636.186.0.1 to 36.186.255.25436.186.255.25565,534
18836.187.0.0/1636.187.0.1 to 36.187.255.25436.187.255.25565,534
18936.188.0.0/1636.188.0.1 to 36.188.255.25436.188.255.25565,534
19036.189.0.0/1636.189.0.1 to 36.189.255.25436.189.255.25565,534
19136.190.0.0/1636.190.0.1 to 36.190.255.25436.190.255.25565,534
19236.191.0.0/1636.191.0.1 to 36.191.255.25436.191.255.25565,534
19336.192.0.0/1636.192.0.1 to 36.192.255.25436.192.255.25565,534
19436.193.0.0/1636.193.0.1 to 36.193.255.25436.193.255.25565,534
19536.194.0.0/1636.194.0.1 to 36.194.255.25436.194.255.25565,534
19636.195.0.0/1636.195.0.1 to 36.195.255.25436.195.255.25565,534
19736.196.0.0/1636.196.0.1 to 36.196.255.25436.196.255.25565,534
19836.197.0.0/1636.197.0.1 to 36.197.255.25436.197.255.25565,534
19936.198.0.0/1636.198.0.1 to 36.198.255.25436.198.255.25565,534
20036.199.0.0/1636.199.0.1 to 36.199.255.25436.199.255.25565,534
20136.200.0.0/1636.200.0.1 to 36.200.255.25436.200.255.25565,534
20236.201.0.0/1636.201.0.1 to 36.201.255.25436.201.255.25565,534
20336.202.0.0/1636.202.0.1 to 36.202.255.25436.202.255.25565,534
20436.203.0.0/1636.203.0.1 to 36.203.255.25436.203.255.25565,534
20536.204.0.0/1636.204.0.1 to 36.204.255.25436.204.255.25565,534
20636.205.0.0/1636.205.0.1 to 36.205.255.25436.205.255.25565,534
20736.206.0.0/1636.206.0.1 to 36.206.255.25436.206.255.25565,534
20836.207.0.0/1636.207.0.1 to 36.207.255.25436.207.255.25565,534
20936.208.0.0/1636.208.0.1 to 36.208.255.25436.208.255.25565,534
21036.209.0.0/1636.209.0.1 to 36.209.255.25436.209.255.25565,534
21136.210.0.0/1636.210.0.1 to 36.210.255.25436.210.255.25565,534
21236.211.0.0/1636.211.0.1 to 36.211.255.25436.211.255.25565,534
21336.212.0.0/1636.212.0.1 to 36.212.255.25436.212.255.25565,534
21436.213.0.0/1636.213.0.1 to 36.213.255.25436.213.255.25565,534
21536.214.0.0/1636.214.0.1 to 36.214.255.25436.214.255.25565,534
21636.215.0.0/1636.215.0.1 to 36.215.255.25436.215.255.25565,534
21736.216.0.0/1636.216.0.1 to 36.216.255.25436.216.255.25565,534
21836.217.0.0/1636.217.0.1 to 36.217.255.25436.217.255.25565,534
21936.218.0.0/1636.218.0.1 to 36.218.255.25436.218.255.25565,534
22036.219.0.0/1636.219.0.1 to 36.219.255.25436.219.255.25565,534
22136.220.0.0/1636.220.0.1 to 36.220.255.25436.220.255.25565,534
22236.221.0.0/1636.221.0.1 to 36.221.255.25436.221.255.25565,534
22336.222.0.0/1636.222.0.1 to 36.222.255.25436.222.255.25565,534
22436.223.0.0/1636.223.0.1 to 36.223.255.25436.223.255.25565,534
22536.224.0.0/1636.224.0.1 to 36.224.255.25436.224.255.25565,534
22636.225.0.0/1636.225.0.1 to 36.225.255.25436.225.255.25565,534
22736.226.0.0/1636.226.0.1 to 36.226.255.25436.226.255.25565,534
22836.227.0.0/1636.227.0.1 to 36.227.255.25436.227.255.25565,534
22936.228.0.0/1636.228.0.1 to 36.228.255.25436.228.255.25565,534
23036.229.0.0/1636.229.0.1 to 36.229.255.25436.229.255.25565,534
23136.230.0.0/1636.230.0.1 to 36.230.255.25436.230.255.25565,534
23236.231.0.0/1636.231.0.1 to 36.231.255.25436.231.255.25565,534
23336.232.0.0/1636.232.0.1 to 36.232.255.25436.232.255.25565,534
23436.233.0.0/1636.233.0.1 to 36.233.255.25436.233.255.25565,534
23536.234.0.0/1636.234.0.1 to 36.234.255.25436.234.255.25565,534
23636.235.0.0/1636.235.0.1 to 36.235.255.25436.235.255.25565,534
23736.236.0.0/1636.236.0.1 to 36.236.255.25436.236.255.25565,534
23836.237.0.0/1636.237.0.1 to 36.237.255.25436.237.255.25565,534
23936.238.0.0/1636.238.0.1 to 36.238.255.25436.238.255.25565,534
24036.239.0.0/1636.239.0.1 to 36.239.255.25436.239.255.25565,534
24136.240.0.0/1636.240.0.1 to 36.240.255.25436.240.255.25565,534
24236.241.0.0/1636.241.0.1 to 36.241.255.25436.241.255.25565,534
24336.242.0.0/1636.242.0.1 to 36.242.255.25436.242.255.25565,534
24436.243.0.0/1636.243.0.1 to 36.243.255.25436.243.255.25565,534
24536.244.0.0/1636.244.0.1 to 36.244.255.25436.244.255.25565,534
24636.245.0.0/1636.245.0.1 to 36.245.255.25436.245.255.25565,534
24736.246.0.0/1636.246.0.1 to 36.246.255.25436.246.255.25565,534
24836.247.0.0/1636.247.0.1 to 36.247.255.25436.247.255.25565,534
24936.248.0.0/1636.248.0.1 to 36.248.255.25436.248.255.25565,534
25036.249.0.0/1636.249.0.1 to 36.249.255.25436.249.255.25565,534
25136.250.0.0/1636.250.0.1 to 36.250.255.25436.250.255.25565,534
25236.251.0.0/1636.251.0.1 to 36.251.255.25436.251.255.25565,534
25336.252.0.0/1636.252.0.1 to 36.252.255.25436.252.255.25565,534
25436.253.0.0/1636.253.0.1 to 36.253.255.25436.253.255.25565,534
25536.254.0.0/1636.254.0.1 to 36.254.255.25436.254.255.25565,534
25636.255.0.0/1636.255.0.1 to 36.255.255.25436.255.255.25565,534

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.