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.

Network73.78.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
73.78.0.0
Broadcast address
73.79.255.255
First usable
73.78.0.1
Last usable
73.79.255.254
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 494E0000 · Integer 1229848576 to 1229979647
Reverse DNS zones
78.73.in-addr.arpa
79.73.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
Address01001001.01001110.00000000.0000000073.78.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network01001001.01001110.00000000.0000000073.78.0.0
Broadcast01001001.01001111.11111111.1111111173.79.255.255
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)

73.78.0.0/15 makes 512 subnets of /24; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
173.78.0.0/2473.78.0.1 to 73.78.0.25473.78.0.255254
273.78.1.0/2473.78.1.1 to 73.78.1.25473.78.1.255254
373.78.2.0/2473.78.2.1 to 73.78.2.25473.78.2.255254
473.78.3.0/2473.78.3.1 to 73.78.3.25473.78.3.255254
573.78.4.0/2473.78.4.1 to 73.78.4.25473.78.4.255254
673.78.5.0/2473.78.5.1 to 73.78.5.25473.78.5.255254
773.78.6.0/2473.78.6.1 to 73.78.6.25473.78.6.255254
873.78.7.0/2473.78.7.1 to 73.78.7.25473.78.7.255254
973.78.8.0/2473.78.8.1 to 73.78.8.25473.78.8.255254
1073.78.9.0/2473.78.9.1 to 73.78.9.25473.78.9.255254
1173.78.10.0/2473.78.10.1 to 73.78.10.25473.78.10.255254
1273.78.11.0/2473.78.11.1 to 73.78.11.25473.78.11.255254
1373.78.12.0/2473.78.12.1 to 73.78.12.25473.78.12.255254
1473.78.13.0/2473.78.13.1 to 73.78.13.25473.78.13.255254
1573.78.14.0/2473.78.14.1 to 73.78.14.25473.78.14.255254
1673.78.15.0/2473.78.15.1 to 73.78.15.25473.78.15.255254
1773.78.16.0/2473.78.16.1 to 73.78.16.25473.78.16.255254
1873.78.17.0/2473.78.17.1 to 73.78.17.25473.78.17.255254
1973.78.18.0/2473.78.18.1 to 73.78.18.25473.78.18.255254
2073.78.19.0/2473.78.19.1 to 73.78.19.25473.78.19.255254
2173.78.20.0/2473.78.20.1 to 73.78.20.25473.78.20.255254
2273.78.21.0/2473.78.21.1 to 73.78.21.25473.78.21.255254
2373.78.22.0/2473.78.22.1 to 73.78.22.25473.78.22.255254
2473.78.23.0/2473.78.23.1 to 73.78.23.25473.78.23.255254
2573.78.24.0/2473.78.24.1 to 73.78.24.25473.78.24.255254
2673.78.25.0/2473.78.25.1 to 73.78.25.25473.78.25.255254
2773.78.26.0/2473.78.26.1 to 73.78.26.25473.78.26.255254
2873.78.27.0/2473.78.27.1 to 73.78.27.25473.78.27.255254
2973.78.28.0/2473.78.28.1 to 73.78.28.25473.78.28.255254
3073.78.29.0/2473.78.29.1 to 73.78.29.25473.78.29.255254
3173.78.30.0/2473.78.30.1 to 73.78.30.25473.78.30.255254
3273.78.31.0/2473.78.31.1 to 73.78.31.25473.78.31.255254
3373.78.32.0/2473.78.32.1 to 73.78.32.25473.78.32.255254
3473.78.33.0/2473.78.33.1 to 73.78.33.25473.78.33.255254
3573.78.34.0/2473.78.34.1 to 73.78.34.25473.78.34.255254
3673.78.35.0/2473.78.35.1 to 73.78.35.25473.78.35.255254
3773.78.36.0/2473.78.36.1 to 73.78.36.25473.78.36.255254
3873.78.37.0/2473.78.37.1 to 73.78.37.25473.78.37.255254
3973.78.38.0/2473.78.38.1 to 73.78.38.25473.78.38.255254
4073.78.39.0/2473.78.39.1 to 73.78.39.25473.78.39.255254
4173.78.40.0/2473.78.40.1 to 73.78.40.25473.78.40.255254
4273.78.41.0/2473.78.41.1 to 73.78.41.25473.78.41.255254
4373.78.42.0/2473.78.42.1 to 73.78.42.25473.78.42.255254
4473.78.43.0/2473.78.43.1 to 73.78.43.25473.78.43.255254
4573.78.44.0/2473.78.44.1 to 73.78.44.25473.78.44.255254
4673.78.45.0/2473.78.45.1 to 73.78.45.25473.78.45.255254
4773.78.46.0/2473.78.46.1 to 73.78.46.25473.78.46.255254
4873.78.47.0/2473.78.47.1 to 73.78.47.25473.78.47.255254
4973.78.48.0/2473.78.48.1 to 73.78.48.25473.78.48.255254
5073.78.49.0/2473.78.49.1 to 73.78.49.25473.78.49.255254
5173.78.50.0/2473.78.50.1 to 73.78.50.25473.78.50.255254
5273.78.51.0/2473.78.51.1 to 73.78.51.25473.78.51.255254
5373.78.52.0/2473.78.52.1 to 73.78.52.25473.78.52.255254
5473.78.53.0/2473.78.53.1 to 73.78.53.25473.78.53.255254
5573.78.54.0/2473.78.54.1 to 73.78.54.25473.78.54.255254
5673.78.55.0/2473.78.55.1 to 73.78.55.25473.78.55.255254
5773.78.56.0/2473.78.56.1 to 73.78.56.25473.78.56.255254
5873.78.57.0/2473.78.57.1 to 73.78.57.25473.78.57.255254
5973.78.58.0/2473.78.58.1 to 73.78.58.25473.78.58.255254
6073.78.59.0/2473.78.59.1 to 73.78.59.25473.78.59.255254
6173.78.60.0/2473.78.60.1 to 73.78.60.25473.78.60.255254
6273.78.61.0/2473.78.61.1 to 73.78.61.25473.78.61.255254
6373.78.62.0/2473.78.62.1 to 73.78.62.25473.78.62.255254
6473.78.63.0/2473.78.63.1 to 73.78.63.25473.78.63.255254
6573.78.64.0/2473.78.64.1 to 73.78.64.25473.78.64.255254
6673.78.65.0/2473.78.65.1 to 73.78.65.25473.78.65.255254
6773.78.66.0/2473.78.66.1 to 73.78.66.25473.78.66.255254
6873.78.67.0/2473.78.67.1 to 73.78.67.25473.78.67.255254
6973.78.68.0/2473.78.68.1 to 73.78.68.25473.78.68.255254
7073.78.69.0/2473.78.69.1 to 73.78.69.25473.78.69.255254
7173.78.70.0/2473.78.70.1 to 73.78.70.25473.78.70.255254
7273.78.71.0/2473.78.71.1 to 73.78.71.25473.78.71.255254
7373.78.72.0/2473.78.72.1 to 73.78.72.25473.78.72.255254
7473.78.73.0/2473.78.73.1 to 73.78.73.25473.78.73.255254
7573.78.74.0/2473.78.74.1 to 73.78.74.25473.78.74.255254
7673.78.75.0/2473.78.75.1 to 73.78.75.25473.78.75.255254
7773.78.76.0/2473.78.76.1 to 73.78.76.25473.78.76.255254
7873.78.77.0/2473.78.77.1 to 73.78.77.25473.78.77.255254
7973.78.78.0/2473.78.78.1 to 73.78.78.25473.78.78.255254
8073.78.79.0/2473.78.79.1 to 73.78.79.25473.78.79.255254
8173.78.80.0/2473.78.80.1 to 73.78.80.25473.78.80.255254
8273.78.81.0/2473.78.81.1 to 73.78.81.25473.78.81.255254
8373.78.82.0/2473.78.82.1 to 73.78.82.25473.78.82.255254
8473.78.83.0/2473.78.83.1 to 73.78.83.25473.78.83.255254
8573.78.84.0/2473.78.84.1 to 73.78.84.25473.78.84.255254
8673.78.85.0/2473.78.85.1 to 73.78.85.25473.78.85.255254
8773.78.86.0/2473.78.86.1 to 73.78.86.25473.78.86.255254
8873.78.87.0/2473.78.87.1 to 73.78.87.25473.78.87.255254
8973.78.88.0/2473.78.88.1 to 73.78.88.25473.78.88.255254
9073.78.89.0/2473.78.89.1 to 73.78.89.25473.78.89.255254
9173.78.90.0/2473.78.90.1 to 73.78.90.25473.78.90.255254
9273.78.91.0/2473.78.91.1 to 73.78.91.25473.78.91.255254
9373.78.92.0/2473.78.92.1 to 73.78.92.25473.78.92.255254
9473.78.93.0/2473.78.93.1 to 73.78.93.25473.78.93.255254
9573.78.94.0/2473.78.94.1 to 73.78.94.25473.78.94.255254
9673.78.95.0/2473.78.95.1 to 73.78.95.25473.78.95.255254
9773.78.96.0/2473.78.96.1 to 73.78.96.25473.78.96.255254
9873.78.97.0/2473.78.97.1 to 73.78.97.25473.78.97.255254
9973.78.98.0/2473.78.98.1 to 73.78.98.25473.78.98.255254
10073.78.99.0/2473.78.99.1 to 73.78.99.25473.78.99.255254
10173.78.100.0/2473.78.100.1 to 73.78.100.25473.78.100.255254
10273.78.101.0/2473.78.101.1 to 73.78.101.25473.78.101.255254
10373.78.102.0/2473.78.102.1 to 73.78.102.25473.78.102.255254
10473.78.103.0/2473.78.103.1 to 73.78.103.25473.78.103.255254
10573.78.104.0/2473.78.104.1 to 73.78.104.25473.78.104.255254
10673.78.105.0/2473.78.105.1 to 73.78.105.25473.78.105.255254
10773.78.106.0/2473.78.106.1 to 73.78.106.25473.78.106.255254
10873.78.107.0/2473.78.107.1 to 73.78.107.25473.78.107.255254
10973.78.108.0/2473.78.108.1 to 73.78.108.25473.78.108.255254
11073.78.109.0/2473.78.109.1 to 73.78.109.25473.78.109.255254
11173.78.110.0/2473.78.110.1 to 73.78.110.25473.78.110.255254
11273.78.111.0/2473.78.111.1 to 73.78.111.25473.78.111.255254
11373.78.112.0/2473.78.112.1 to 73.78.112.25473.78.112.255254
11473.78.113.0/2473.78.113.1 to 73.78.113.25473.78.113.255254
11573.78.114.0/2473.78.114.1 to 73.78.114.25473.78.114.255254
11673.78.115.0/2473.78.115.1 to 73.78.115.25473.78.115.255254
11773.78.116.0/2473.78.116.1 to 73.78.116.25473.78.116.255254
11873.78.117.0/2473.78.117.1 to 73.78.117.25473.78.117.255254
11973.78.118.0/2473.78.118.1 to 73.78.118.25473.78.118.255254
12073.78.119.0/2473.78.119.1 to 73.78.119.25473.78.119.255254
12173.78.120.0/2473.78.120.1 to 73.78.120.25473.78.120.255254
12273.78.121.0/2473.78.121.1 to 73.78.121.25473.78.121.255254
12373.78.122.0/2473.78.122.1 to 73.78.122.25473.78.122.255254
12473.78.123.0/2473.78.123.1 to 73.78.123.25473.78.123.255254
12573.78.124.0/2473.78.124.1 to 73.78.124.25473.78.124.255254
12673.78.125.0/2473.78.125.1 to 73.78.125.25473.78.125.255254
12773.78.126.0/2473.78.126.1 to 73.78.126.25473.78.126.255254
12873.78.127.0/2473.78.127.1 to 73.78.127.25473.78.127.255254
12973.78.128.0/2473.78.128.1 to 73.78.128.25473.78.128.255254
13073.78.129.0/2473.78.129.1 to 73.78.129.25473.78.129.255254
13173.78.130.0/2473.78.130.1 to 73.78.130.25473.78.130.255254
13273.78.131.0/2473.78.131.1 to 73.78.131.25473.78.131.255254
13373.78.132.0/2473.78.132.1 to 73.78.132.25473.78.132.255254
13473.78.133.0/2473.78.133.1 to 73.78.133.25473.78.133.255254
13573.78.134.0/2473.78.134.1 to 73.78.134.25473.78.134.255254
13673.78.135.0/2473.78.135.1 to 73.78.135.25473.78.135.255254
13773.78.136.0/2473.78.136.1 to 73.78.136.25473.78.136.255254
13873.78.137.0/2473.78.137.1 to 73.78.137.25473.78.137.255254
13973.78.138.0/2473.78.138.1 to 73.78.138.25473.78.138.255254
14073.78.139.0/2473.78.139.1 to 73.78.139.25473.78.139.255254
14173.78.140.0/2473.78.140.1 to 73.78.140.25473.78.140.255254
14273.78.141.0/2473.78.141.1 to 73.78.141.25473.78.141.255254
14373.78.142.0/2473.78.142.1 to 73.78.142.25473.78.142.255254
14473.78.143.0/2473.78.143.1 to 73.78.143.25473.78.143.255254
14573.78.144.0/2473.78.144.1 to 73.78.144.25473.78.144.255254
14673.78.145.0/2473.78.145.1 to 73.78.145.25473.78.145.255254
14773.78.146.0/2473.78.146.1 to 73.78.146.25473.78.146.255254
14873.78.147.0/2473.78.147.1 to 73.78.147.25473.78.147.255254
14973.78.148.0/2473.78.148.1 to 73.78.148.25473.78.148.255254
15073.78.149.0/2473.78.149.1 to 73.78.149.25473.78.149.255254
15173.78.150.0/2473.78.150.1 to 73.78.150.25473.78.150.255254
15273.78.151.0/2473.78.151.1 to 73.78.151.25473.78.151.255254
15373.78.152.0/2473.78.152.1 to 73.78.152.25473.78.152.255254
15473.78.153.0/2473.78.153.1 to 73.78.153.25473.78.153.255254
15573.78.154.0/2473.78.154.1 to 73.78.154.25473.78.154.255254
15673.78.155.0/2473.78.155.1 to 73.78.155.25473.78.155.255254
15773.78.156.0/2473.78.156.1 to 73.78.156.25473.78.156.255254
15873.78.157.0/2473.78.157.1 to 73.78.157.25473.78.157.255254
15973.78.158.0/2473.78.158.1 to 73.78.158.25473.78.158.255254
16073.78.159.0/2473.78.159.1 to 73.78.159.25473.78.159.255254
16173.78.160.0/2473.78.160.1 to 73.78.160.25473.78.160.255254
16273.78.161.0/2473.78.161.1 to 73.78.161.25473.78.161.255254
16373.78.162.0/2473.78.162.1 to 73.78.162.25473.78.162.255254
16473.78.163.0/2473.78.163.1 to 73.78.163.25473.78.163.255254
16573.78.164.0/2473.78.164.1 to 73.78.164.25473.78.164.255254
16673.78.165.0/2473.78.165.1 to 73.78.165.25473.78.165.255254
16773.78.166.0/2473.78.166.1 to 73.78.166.25473.78.166.255254
16873.78.167.0/2473.78.167.1 to 73.78.167.25473.78.167.255254
16973.78.168.0/2473.78.168.1 to 73.78.168.25473.78.168.255254
17073.78.169.0/2473.78.169.1 to 73.78.169.25473.78.169.255254
17173.78.170.0/2473.78.170.1 to 73.78.170.25473.78.170.255254
17273.78.171.0/2473.78.171.1 to 73.78.171.25473.78.171.255254
17373.78.172.0/2473.78.172.1 to 73.78.172.25473.78.172.255254
17473.78.173.0/2473.78.173.1 to 73.78.173.25473.78.173.255254
17573.78.174.0/2473.78.174.1 to 73.78.174.25473.78.174.255254
17673.78.175.0/2473.78.175.1 to 73.78.175.25473.78.175.255254
17773.78.176.0/2473.78.176.1 to 73.78.176.25473.78.176.255254
17873.78.177.0/2473.78.177.1 to 73.78.177.25473.78.177.255254
17973.78.178.0/2473.78.178.1 to 73.78.178.25473.78.178.255254
18073.78.179.0/2473.78.179.1 to 73.78.179.25473.78.179.255254
18173.78.180.0/2473.78.180.1 to 73.78.180.25473.78.180.255254
18273.78.181.0/2473.78.181.1 to 73.78.181.25473.78.181.255254
18373.78.182.0/2473.78.182.1 to 73.78.182.25473.78.182.255254
18473.78.183.0/2473.78.183.1 to 73.78.183.25473.78.183.255254
18573.78.184.0/2473.78.184.1 to 73.78.184.25473.78.184.255254
18673.78.185.0/2473.78.185.1 to 73.78.185.25473.78.185.255254
18773.78.186.0/2473.78.186.1 to 73.78.186.25473.78.186.255254
18873.78.187.0/2473.78.187.1 to 73.78.187.25473.78.187.255254
18973.78.188.0/2473.78.188.1 to 73.78.188.25473.78.188.255254
19073.78.189.0/2473.78.189.1 to 73.78.189.25473.78.189.255254
19173.78.190.0/2473.78.190.1 to 73.78.190.25473.78.190.255254
19273.78.191.0/2473.78.191.1 to 73.78.191.25473.78.191.255254
19373.78.192.0/2473.78.192.1 to 73.78.192.25473.78.192.255254
19473.78.193.0/2473.78.193.1 to 73.78.193.25473.78.193.255254
19573.78.194.0/2473.78.194.1 to 73.78.194.25473.78.194.255254
19673.78.195.0/2473.78.195.1 to 73.78.195.25473.78.195.255254
19773.78.196.0/2473.78.196.1 to 73.78.196.25473.78.196.255254
19873.78.197.0/2473.78.197.1 to 73.78.197.25473.78.197.255254
19973.78.198.0/2473.78.198.1 to 73.78.198.25473.78.198.255254
20073.78.199.0/2473.78.199.1 to 73.78.199.25473.78.199.255254
20173.78.200.0/2473.78.200.1 to 73.78.200.25473.78.200.255254
20273.78.201.0/2473.78.201.1 to 73.78.201.25473.78.201.255254
20373.78.202.0/2473.78.202.1 to 73.78.202.25473.78.202.255254
20473.78.203.0/2473.78.203.1 to 73.78.203.25473.78.203.255254
20573.78.204.0/2473.78.204.1 to 73.78.204.25473.78.204.255254
20673.78.205.0/2473.78.205.1 to 73.78.205.25473.78.205.255254
20773.78.206.0/2473.78.206.1 to 73.78.206.25473.78.206.255254
20873.78.207.0/2473.78.207.1 to 73.78.207.25473.78.207.255254
20973.78.208.0/2473.78.208.1 to 73.78.208.25473.78.208.255254
21073.78.209.0/2473.78.209.1 to 73.78.209.25473.78.209.255254
21173.78.210.0/2473.78.210.1 to 73.78.210.25473.78.210.255254
21273.78.211.0/2473.78.211.1 to 73.78.211.25473.78.211.255254
21373.78.212.0/2473.78.212.1 to 73.78.212.25473.78.212.255254
21473.78.213.0/2473.78.213.1 to 73.78.213.25473.78.213.255254
21573.78.214.0/2473.78.214.1 to 73.78.214.25473.78.214.255254
21673.78.215.0/2473.78.215.1 to 73.78.215.25473.78.215.255254
21773.78.216.0/2473.78.216.1 to 73.78.216.25473.78.216.255254
21873.78.217.0/2473.78.217.1 to 73.78.217.25473.78.217.255254
21973.78.218.0/2473.78.218.1 to 73.78.218.25473.78.218.255254
22073.78.219.0/2473.78.219.1 to 73.78.219.25473.78.219.255254
22173.78.220.0/2473.78.220.1 to 73.78.220.25473.78.220.255254
22273.78.221.0/2473.78.221.1 to 73.78.221.25473.78.221.255254
22373.78.222.0/2473.78.222.1 to 73.78.222.25473.78.222.255254
22473.78.223.0/2473.78.223.1 to 73.78.223.25473.78.223.255254
22573.78.224.0/2473.78.224.1 to 73.78.224.25473.78.224.255254
22673.78.225.0/2473.78.225.1 to 73.78.225.25473.78.225.255254
22773.78.226.0/2473.78.226.1 to 73.78.226.25473.78.226.255254
22873.78.227.0/2473.78.227.1 to 73.78.227.25473.78.227.255254
22973.78.228.0/2473.78.228.1 to 73.78.228.25473.78.228.255254
23073.78.229.0/2473.78.229.1 to 73.78.229.25473.78.229.255254
23173.78.230.0/2473.78.230.1 to 73.78.230.25473.78.230.255254
23273.78.231.0/2473.78.231.1 to 73.78.231.25473.78.231.255254
23373.78.232.0/2473.78.232.1 to 73.78.232.25473.78.232.255254
23473.78.233.0/2473.78.233.1 to 73.78.233.25473.78.233.255254
23573.78.234.0/2473.78.234.1 to 73.78.234.25473.78.234.255254
23673.78.235.0/2473.78.235.1 to 73.78.235.25473.78.235.255254
23773.78.236.0/2473.78.236.1 to 73.78.236.25473.78.236.255254
23873.78.237.0/2473.78.237.1 to 73.78.237.25473.78.237.255254
23973.78.238.0/2473.78.238.1 to 73.78.238.25473.78.238.255254
24073.78.239.0/2473.78.239.1 to 73.78.239.25473.78.239.255254
24173.78.240.0/2473.78.240.1 to 73.78.240.25473.78.240.255254
24273.78.241.0/2473.78.241.1 to 73.78.241.25473.78.241.255254
24373.78.242.0/2473.78.242.1 to 73.78.242.25473.78.242.255254
24473.78.243.0/2473.78.243.1 to 73.78.243.25473.78.243.255254
24573.78.244.0/2473.78.244.1 to 73.78.244.25473.78.244.255254
24673.78.245.0/2473.78.245.1 to 73.78.245.25473.78.245.255254
24773.78.246.0/2473.78.246.1 to 73.78.246.25473.78.246.255254
24873.78.247.0/2473.78.247.1 to 73.78.247.25473.78.247.255254
24973.78.248.0/2473.78.248.1 to 73.78.248.25473.78.248.255254
25073.78.249.0/2473.78.249.1 to 73.78.249.25473.78.249.255254
25173.78.250.0/2473.78.250.1 to 73.78.250.25473.78.250.255254
25273.78.251.0/2473.78.251.1 to 73.78.251.25473.78.251.255254
25373.78.252.0/2473.78.252.1 to 73.78.252.25473.78.252.255254
25473.78.253.0/2473.78.253.1 to 73.78.253.25473.78.253.255254
25573.78.254.0/2473.78.254.1 to 73.78.254.25473.78.254.255254
25673.78.255.0/2473.78.255.1 to 73.78.255.25473.78.255.255254

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.