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.

Network58.40.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
58.40.0.0
Broadcast address
58.41.255.255
First usable
58.40.0.1
Last usable
58.41.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
A (default /8)
As numbers
Hex 3A280000 · Integer 975699968 to 975831039
Reverse DNS zones
40.58.in-addr.arpa
41.58.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00111010.00101000.00000000.0000000058.40.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network00111010.00101000.00000000.0000000058.40.0.0
Broadcast00111010.00101001.11111111.1111111158.41.255.255
Split into smaller subnets/24
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

58.40.0.0/15 makes 512 subnets of /24; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
158.40.0.0/2458.40.0.1 to 58.40.0.25458.40.0.255254
258.40.1.0/2458.40.1.1 to 58.40.1.25458.40.1.255254
358.40.2.0/2458.40.2.1 to 58.40.2.25458.40.2.255254
458.40.3.0/2458.40.3.1 to 58.40.3.25458.40.3.255254
558.40.4.0/2458.40.4.1 to 58.40.4.25458.40.4.255254
658.40.5.0/2458.40.5.1 to 58.40.5.25458.40.5.255254
758.40.6.0/2458.40.6.1 to 58.40.6.25458.40.6.255254
858.40.7.0/2458.40.7.1 to 58.40.7.25458.40.7.255254
958.40.8.0/2458.40.8.1 to 58.40.8.25458.40.8.255254
1058.40.9.0/2458.40.9.1 to 58.40.9.25458.40.9.255254
1158.40.10.0/2458.40.10.1 to 58.40.10.25458.40.10.255254
1258.40.11.0/2458.40.11.1 to 58.40.11.25458.40.11.255254
1358.40.12.0/2458.40.12.1 to 58.40.12.25458.40.12.255254
1458.40.13.0/2458.40.13.1 to 58.40.13.25458.40.13.255254
1558.40.14.0/2458.40.14.1 to 58.40.14.25458.40.14.255254
1658.40.15.0/2458.40.15.1 to 58.40.15.25458.40.15.255254
1758.40.16.0/2458.40.16.1 to 58.40.16.25458.40.16.255254
1858.40.17.0/2458.40.17.1 to 58.40.17.25458.40.17.255254
1958.40.18.0/2458.40.18.1 to 58.40.18.25458.40.18.255254
2058.40.19.0/2458.40.19.1 to 58.40.19.25458.40.19.255254
2158.40.20.0/2458.40.20.1 to 58.40.20.25458.40.20.255254
2258.40.21.0/2458.40.21.1 to 58.40.21.25458.40.21.255254
2358.40.22.0/2458.40.22.1 to 58.40.22.25458.40.22.255254
2458.40.23.0/2458.40.23.1 to 58.40.23.25458.40.23.255254
2558.40.24.0/2458.40.24.1 to 58.40.24.25458.40.24.255254
2658.40.25.0/2458.40.25.1 to 58.40.25.25458.40.25.255254
2758.40.26.0/2458.40.26.1 to 58.40.26.25458.40.26.255254
2858.40.27.0/2458.40.27.1 to 58.40.27.25458.40.27.255254
2958.40.28.0/2458.40.28.1 to 58.40.28.25458.40.28.255254
3058.40.29.0/2458.40.29.1 to 58.40.29.25458.40.29.255254
3158.40.30.0/2458.40.30.1 to 58.40.30.25458.40.30.255254
3258.40.31.0/2458.40.31.1 to 58.40.31.25458.40.31.255254
3358.40.32.0/2458.40.32.1 to 58.40.32.25458.40.32.255254
3458.40.33.0/2458.40.33.1 to 58.40.33.25458.40.33.255254
3558.40.34.0/2458.40.34.1 to 58.40.34.25458.40.34.255254
3658.40.35.0/2458.40.35.1 to 58.40.35.25458.40.35.255254
3758.40.36.0/2458.40.36.1 to 58.40.36.25458.40.36.255254
3858.40.37.0/2458.40.37.1 to 58.40.37.25458.40.37.255254
3958.40.38.0/2458.40.38.1 to 58.40.38.25458.40.38.255254
4058.40.39.0/2458.40.39.1 to 58.40.39.25458.40.39.255254
4158.40.40.0/2458.40.40.1 to 58.40.40.25458.40.40.255254
4258.40.41.0/2458.40.41.1 to 58.40.41.25458.40.41.255254
4358.40.42.0/2458.40.42.1 to 58.40.42.25458.40.42.255254
4458.40.43.0/2458.40.43.1 to 58.40.43.25458.40.43.255254
4558.40.44.0/2458.40.44.1 to 58.40.44.25458.40.44.255254
4658.40.45.0/2458.40.45.1 to 58.40.45.25458.40.45.255254
4758.40.46.0/2458.40.46.1 to 58.40.46.25458.40.46.255254
4858.40.47.0/2458.40.47.1 to 58.40.47.25458.40.47.255254
4958.40.48.0/2458.40.48.1 to 58.40.48.25458.40.48.255254
5058.40.49.0/2458.40.49.1 to 58.40.49.25458.40.49.255254
5158.40.50.0/2458.40.50.1 to 58.40.50.25458.40.50.255254
5258.40.51.0/2458.40.51.1 to 58.40.51.25458.40.51.255254
5358.40.52.0/2458.40.52.1 to 58.40.52.25458.40.52.255254
5458.40.53.0/2458.40.53.1 to 58.40.53.25458.40.53.255254
5558.40.54.0/2458.40.54.1 to 58.40.54.25458.40.54.255254
5658.40.55.0/2458.40.55.1 to 58.40.55.25458.40.55.255254
5758.40.56.0/2458.40.56.1 to 58.40.56.25458.40.56.255254
5858.40.57.0/2458.40.57.1 to 58.40.57.25458.40.57.255254
5958.40.58.0/2458.40.58.1 to 58.40.58.25458.40.58.255254
6058.40.59.0/2458.40.59.1 to 58.40.59.25458.40.59.255254
6158.40.60.0/2458.40.60.1 to 58.40.60.25458.40.60.255254
6258.40.61.0/2458.40.61.1 to 58.40.61.25458.40.61.255254
6358.40.62.0/2458.40.62.1 to 58.40.62.25458.40.62.255254
6458.40.63.0/2458.40.63.1 to 58.40.63.25458.40.63.255254
6558.40.64.0/2458.40.64.1 to 58.40.64.25458.40.64.255254
6658.40.65.0/2458.40.65.1 to 58.40.65.25458.40.65.255254
6758.40.66.0/2458.40.66.1 to 58.40.66.25458.40.66.255254
6858.40.67.0/2458.40.67.1 to 58.40.67.25458.40.67.255254
6958.40.68.0/2458.40.68.1 to 58.40.68.25458.40.68.255254
7058.40.69.0/2458.40.69.1 to 58.40.69.25458.40.69.255254
7158.40.70.0/2458.40.70.1 to 58.40.70.25458.40.70.255254
7258.40.71.0/2458.40.71.1 to 58.40.71.25458.40.71.255254
7358.40.72.0/2458.40.72.1 to 58.40.72.25458.40.72.255254
7458.40.73.0/2458.40.73.1 to 58.40.73.25458.40.73.255254
7558.40.74.0/2458.40.74.1 to 58.40.74.25458.40.74.255254
7658.40.75.0/2458.40.75.1 to 58.40.75.25458.40.75.255254
7758.40.76.0/2458.40.76.1 to 58.40.76.25458.40.76.255254
7858.40.77.0/2458.40.77.1 to 58.40.77.25458.40.77.255254
7958.40.78.0/2458.40.78.1 to 58.40.78.25458.40.78.255254
8058.40.79.0/2458.40.79.1 to 58.40.79.25458.40.79.255254
8158.40.80.0/2458.40.80.1 to 58.40.80.25458.40.80.255254
8258.40.81.0/2458.40.81.1 to 58.40.81.25458.40.81.255254
8358.40.82.0/2458.40.82.1 to 58.40.82.25458.40.82.255254
8458.40.83.0/2458.40.83.1 to 58.40.83.25458.40.83.255254
8558.40.84.0/2458.40.84.1 to 58.40.84.25458.40.84.255254
8658.40.85.0/2458.40.85.1 to 58.40.85.25458.40.85.255254
8758.40.86.0/2458.40.86.1 to 58.40.86.25458.40.86.255254
8858.40.87.0/2458.40.87.1 to 58.40.87.25458.40.87.255254
8958.40.88.0/2458.40.88.1 to 58.40.88.25458.40.88.255254
9058.40.89.0/2458.40.89.1 to 58.40.89.25458.40.89.255254
9158.40.90.0/2458.40.90.1 to 58.40.90.25458.40.90.255254
9258.40.91.0/2458.40.91.1 to 58.40.91.25458.40.91.255254
9358.40.92.0/2458.40.92.1 to 58.40.92.25458.40.92.255254
9458.40.93.0/2458.40.93.1 to 58.40.93.25458.40.93.255254
9558.40.94.0/2458.40.94.1 to 58.40.94.25458.40.94.255254
9658.40.95.0/2458.40.95.1 to 58.40.95.25458.40.95.255254
9758.40.96.0/2458.40.96.1 to 58.40.96.25458.40.96.255254
9858.40.97.0/2458.40.97.1 to 58.40.97.25458.40.97.255254
9958.40.98.0/2458.40.98.1 to 58.40.98.25458.40.98.255254
10058.40.99.0/2458.40.99.1 to 58.40.99.25458.40.99.255254
10158.40.100.0/2458.40.100.1 to 58.40.100.25458.40.100.255254
10258.40.101.0/2458.40.101.1 to 58.40.101.25458.40.101.255254
10358.40.102.0/2458.40.102.1 to 58.40.102.25458.40.102.255254
10458.40.103.0/2458.40.103.1 to 58.40.103.25458.40.103.255254
10558.40.104.0/2458.40.104.1 to 58.40.104.25458.40.104.255254
10658.40.105.0/2458.40.105.1 to 58.40.105.25458.40.105.255254
10758.40.106.0/2458.40.106.1 to 58.40.106.25458.40.106.255254
10858.40.107.0/2458.40.107.1 to 58.40.107.25458.40.107.255254
10958.40.108.0/2458.40.108.1 to 58.40.108.25458.40.108.255254
11058.40.109.0/2458.40.109.1 to 58.40.109.25458.40.109.255254
11158.40.110.0/2458.40.110.1 to 58.40.110.25458.40.110.255254
11258.40.111.0/2458.40.111.1 to 58.40.111.25458.40.111.255254
11358.40.112.0/2458.40.112.1 to 58.40.112.25458.40.112.255254
11458.40.113.0/2458.40.113.1 to 58.40.113.25458.40.113.255254
11558.40.114.0/2458.40.114.1 to 58.40.114.25458.40.114.255254
11658.40.115.0/2458.40.115.1 to 58.40.115.25458.40.115.255254
11758.40.116.0/2458.40.116.1 to 58.40.116.25458.40.116.255254
11858.40.117.0/2458.40.117.1 to 58.40.117.25458.40.117.255254
11958.40.118.0/2458.40.118.1 to 58.40.118.25458.40.118.255254
12058.40.119.0/2458.40.119.1 to 58.40.119.25458.40.119.255254
12158.40.120.0/2458.40.120.1 to 58.40.120.25458.40.120.255254
12258.40.121.0/2458.40.121.1 to 58.40.121.25458.40.121.255254
12358.40.122.0/2458.40.122.1 to 58.40.122.25458.40.122.255254
12458.40.123.0/2458.40.123.1 to 58.40.123.25458.40.123.255254
12558.40.124.0/2458.40.124.1 to 58.40.124.25458.40.124.255254
12658.40.125.0/2458.40.125.1 to 58.40.125.25458.40.125.255254
12758.40.126.0/2458.40.126.1 to 58.40.126.25458.40.126.255254
12858.40.127.0/2458.40.127.1 to 58.40.127.25458.40.127.255254
12958.40.128.0/2458.40.128.1 to 58.40.128.25458.40.128.255254
13058.40.129.0/2458.40.129.1 to 58.40.129.25458.40.129.255254
13158.40.130.0/2458.40.130.1 to 58.40.130.25458.40.130.255254
13258.40.131.0/2458.40.131.1 to 58.40.131.25458.40.131.255254
13358.40.132.0/2458.40.132.1 to 58.40.132.25458.40.132.255254
13458.40.133.0/2458.40.133.1 to 58.40.133.25458.40.133.255254
13558.40.134.0/2458.40.134.1 to 58.40.134.25458.40.134.255254
13658.40.135.0/2458.40.135.1 to 58.40.135.25458.40.135.255254
13758.40.136.0/2458.40.136.1 to 58.40.136.25458.40.136.255254
13858.40.137.0/2458.40.137.1 to 58.40.137.25458.40.137.255254
13958.40.138.0/2458.40.138.1 to 58.40.138.25458.40.138.255254
14058.40.139.0/2458.40.139.1 to 58.40.139.25458.40.139.255254
14158.40.140.0/2458.40.140.1 to 58.40.140.25458.40.140.255254
14258.40.141.0/2458.40.141.1 to 58.40.141.25458.40.141.255254
14358.40.142.0/2458.40.142.1 to 58.40.142.25458.40.142.255254
14458.40.143.0/2458.40.143.1 to 58.40.143.25458.40.143.255254
14558.40.144.0/2458.40.144.1 to 58.40.144.25458.40.144.255254
14658.40.145.0/2458.40.145.1 to 58.40.145.25458.40.145.255254
14758.40.146.0/2458.40.146.1 to 58.40.146.25458.40.146.255254
14858.40.147.0/2458.40.147.1 to 58.40.147.25458.40.147.255254
14958.40.148.0/2458.40.148.1 to 58.40.148.25458.40.148.255254
15058.40.149.0/2458.40.149.1 to 58.40.149.25458.40.149.255254
15158.40.150.0/2458.40.150.1 to 58.40.150.25458.40.150.255254
15258.40.151.0/2458.40.151.1 to 58.40.151.25458.40.151.255254
15358.40.152.0/2458.40.152.1 to 58.40.152.25458.40.152.255254
15458.40.153.0/2458.40.153.1 to 58.40.153.25458.40.153.255254
15558.40.154.0/2458.40.154.1 to 58.40.154.25458.40.154.255254
15658.40.155.0/2458.40.155.1 to 58.40.155.25458.40.155.255254
15758.40.156.0/2458.40.156.1 to 58.40.156.25458.40.156.255254
15858.40.157.0/2458.40.157.1 to 58.40.157.25458.40.157.255254
15958.40.158.0/2458.40.158.1 to 58.40.158.25458.40.158.255254
16058.40.159.0/2458.40.159.1 to 58.40.159.25458.40.159.255254
16158.40.160.0/2458.40.160.1 to 58.40.160.25458.40.160.255254
16258.40.161.0/2458.40.161.1 to 58.40.161.25458.40.161.255254
16358.40.162.0/2458.40.162.1 to 58.40.162.25458.40.162.255254
16458.40.163.0/2458.40.163.1 to 58.40.163.25458.40.163.255254
16558.40.164.0/2458.40.164.1 to 58.40.164.25458.40.164.255254
16658.40.165.0/2458.40.165.1 to 58.40.165.25458.40.165.255254
16758.40.166.0/2458.40.166.1 to 58.40.166.25458.40.166.255254
16858.40.167.0/2458.40.167.1 to 58.40.167.25458.40.167.255254
16958.40.168.0/2458.40.168.1 to 58.40.168.25458.40.168.255254
17058.40.169.0/2458.40.169.1 to 58.40.169.25458.40.169.255254
17158.40.170.0/2458.40.170.1 to 58.40.170.25458.40.170.255254
17258.40.171.0/2458.40.171.1 to 58.40.171.25458.40.171.255254
17358.40.172.0/2458.40.172.1 to 58.40.172.25458.40.172.255254
17458.40.173.0/2458.40.173.1 to 58.40.173.25458.40.173.255254
17558.40.174.0/2458.40.174.1 to 58.40.174.25458.40.174.255254
17658.40.175.0/2458.40.175.1 to 58.40.175.25458.40.175.255254
17758.40.176.0/2458.40.176.1 to 58.40.176.25458.40.176.255254
17858.40.177.0/2458.40.177.1 to 58.40.177.25458.40.177.255254
17958.40.178.0/2458.40.178.1 to 58.40.178.25458.40.178.255254
18058.40.179.0/2458.40.179.1 to 58.40.179.25458.40.179.255254
18158.40.180.0/2458.40.180.1 to 58.40.180.25458.40.180.255254
18258.40.181.0/2458.40.181.1 to 58.40.181.25458.40.181.255254
18358.40.182.0/2458.40.182.1 to 58.40.182.25458.40.182.255254
18458.40.183.0/2458.40.183.1 to 58.40.183.25458.40.183.255254
18558.40.184.0/2458.40.184.1 to 58.40.184.25458.40.184.255254
18658.40.185.0/2458.40.185.1 to 58.40.185.25458.40.185.255254
18758.40.186.0/2458.40.186.1 to 58.40.186.25458.40.186.255254
18858.40.187.0/2458.40.187.1 to 58.40.187.25458.40.187.255254
18958.40.188.0/2458.40.188.1 to 58.40.188.25458.40.188.255254
19058.40.189.0/2458.40.189.1 to 58.40.189.25458.40.189.255254
19158.40.190.0/2458.40.190.1 to 58.40.190.25458.40.190.255254
19258.40.191.0/2458.40.191.1 to 58.40.191.25458.40.191.255254
19358.40.192.0/2458.40.192.1 to 58.40.192.25458.40.192.255254
19458.40.193.0/2458.40.193.1 to 58.40.193.25458.40.193.255254
19558.40.194.0/2458.40.194.1 to 58.40.194.25458.40.194.255254
19658.40.195.0/2458.40.195.1 to 58.40.195.25458.40.195.255254
19758.40.196.0/2458.40.196.1 to 58.40.196.25458.40.196.255254
19858.40.197.0/2458.40.197.1 to 58.40.197.25458.40.197.255254
19958.40.198.0/2458.40.198.1 to 58.40.198.25458.40.198.255254
20058.40.199.0/2458.40.199.1 to 58.40.199.25458.40.199.255254
20158.40.200.0/2458.40.200.1 to 58.40.200.25458.40.200.255254
20258.40.201.0/2458.40.201.1 to 58.40.201.25458.40.201.255254
20358.40.202.0/2458.40.202.1 to 58.40.202.25458.40.202.255254
20458.40.203.0/2458.40.203.1 to 58.40.203.25458.40.203.255254
20558.40.204.0/2458.40.204.1 to 58.40.204.25458.40.204.255254
20658.40.205.0/2458.40.205.1 to 58.40.205.25458.40.205.255254
20758.40.206.0/2458.40.206.1 to 58.40.206.25458.40.206.255254
20858.40.207.0/2458.40.207.1 to 58.40.207.25458.40.207.255254
20958.40.208.0/2458.40.208.1 to 58.40.208.25458.40.208.255254
21058.40.209.0/2458.40.209.1 to 58.40.209.25458.40.209.255254
21158.40.210.0/2458.40.210.1 to 58.40.210.25458.40.210.255254
21258.40.211.0/2458.40.211.1 to 58.40.211.25458.40.211.255254
21358.40.212.0/2458.40.212.1 to 58.40.212.25458.40.212.255254
21458.40.213.0/2458.40.213.1 to 58.40.213.25458.40.213.255254
21558.40.214.0/2458.40.214.1 to 58.40.214.25458.40.214.255254
21658.40.215.0/2458.40.215.1 to 58.40.215.25458.40.215.255254
21758.40.216.0/2458.40.216.1 to 58.40.216.25458.40.216.255254
21858.40.217.0/2458.40.217.1 to 58.40.217.25458.40.217.255254
21958.40.218.0/2458.40.218.1 to 58.40.218.25458.40.218.255254
22058.40.219.0/2458.40.219.1 to 58.40.219.25458.40.219.255254
22158.40.220.0/2458.40.220.1 to 58.40.220.25458.40.220.255254
22258.40.221.0/2458.40.221.1 to 58.40.221.25458.40.221.255254
22358.40.222.0/2458.40.222.1 to 58.40.222.25458.40.222.255254
22458.40.223.0/2458.40.223.1 to 58.40.223.25458.40.223.255254
22558.40.224.0/2458.40.224.1 to 58.40.224.25458.40.224.255254
22658.40.225.0/2458.40.225.1 to 58.40.225.25458.40.225.255254
22758.40.226.0/2458.40.226.1 to 58.40.226.25458.40.226.255254
22858.40.227.0/2458.40.227.1 to 58.40.227.25458.40.227.255254
22958.40.228.0/2458.40.228.1 to 58.40.228.25458.40.228.255254
23058.40.229.0/2458.40.229.1 to 58.40.229.25458.40.229.255254
23158.40.230.0/2458.40.230.1 to 58.40.230.25458.40.230.255254
23258.40.231.0/2458.40.231.1 to 58.40.231.25458.40.231.255254
23358.40.232.0/2458.40.232.1 to 58.40.232.25458.40.232.255254
23458.40.233.0/2458.40.233.1 to 58.40.233.25458.40.233.255254
23558.40.234.0/2458.40.234.1 to 58.40.234.25458.40.234.255254
23658.40.235.0/2458.40.235.1 to 58.40.235.25458.40.235.255254
23758.40.236.0/2458.40.236.1 to 58.40.236.25458.40.236.255254
23858.40.237.0/2458.40.237.1 to 58.40.237.25458.40.237.255254
23958.40.238.0/2458.40.238.1 to 58.40.238.25458.40.238.255254
24058.40.239.0/2458.40.239.1 to 58.40.239.25458.40.239.255254
24158.40.240.0/2458.40.240.1 to 58.40.240.25458.40.240.255254
24258.40.241.0/2458.40.241.1 to 58.40.241.25458.40.241.255254
24358.40.242.0/2458.40.242.1 to 58.40.242.25458.40.242.255254
24458.40.243.0/2458.40.243.1 to 58.40.243.25458.40.243.255254
24558.40.244.0/2458.40.244.1 to 58.40.244.25458.40.244.255254
24658.40.245.0/2458.40.245.1 to 58.40.245.25458.40.245.255254
24758.40.246.0/2458.40.246.1 to 58.40.246.25458.40.246.255254
24858.40.247.0/2458.40.247.1 to 58.40.247.25458.40.247.255254
24958.40.248.0/2458.40.248.1 to 58.40.248.25458.40.248.255254
25058.40.249.0/2458.40.249.1 to 58.40.249.25458.40.249.255254
25158.40.250.0/2458.40.250.1 to 58.40.250.25458.40.250.255254
25258.40.251.0/2458.40.251.1 to 58.40.251.25458.40.251.255254
25358.40.252.0/2458.40.252.1 to 58.40.252.25458.40.252.255254
25458.40.253.0/2458.40.253.1 to 58.40.253.25458.40.253.255254
25558.40.254.0/2458.40.254.1 to 58.40.254.25458.40.254.255254
25658.40.255.0/2458.40.255.1 to 58.40.255.25458.40.255.255254

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.