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.

Network56.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
56.0.0.0
Broadcast address
57.255.255.255
First usable
56.0.0.1
Last usable
57.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
A (default /8)
As numbers
Hex 38000000 · Integer 939524096 to 973078527
Reverse DNS zones
56.in-addr.arpa
57.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00111000.00000000.00000000.0000000056.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network00111000.00000000.00000000.0000000056.0.0.0
Broadcast00111001.11111111.11111111.1111111157.255.255.255
Split into smaller subnets/15
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

56.0.0.0/7 makes 256 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
156.0.0.0/1556.0.0.1 to 56.1.255.25456.1.255.255131,070
256.2.0.0/1556.2.0.1 to 56.3.255.25456.3.255.255131,070
356.4.0.0/1556.4.0.1 to 56.5.255.25456.5.255.255131,070
456.6.0.0/1556.6.0.1 to 56.7.255.25456.7.255.255131,070
556.8.0.0/1556.8.0.1 to 56.9.255.25456.9.255.255131,070
656.10.0.0/1556.10.0.1 to 56.11.255.25456.11.255.255131,070
756.12.0.0/1556.12.0.1 to 56.13.255.25456.13.255.255131,070
856.14.0.0/1556.14.0.1 to 56.15.255.25456.15.255.255131,070
956.16.0.0/1556.16.0.1 to 56.17.255.25456.17.255.255131,070
1056.18.0.0/1556.18.0.1 to 56.19.255.25456.19.255.255131,070
1156.20.0.0/1556.20.0.1 to 56.21.255.25456.21.255.255131,070
1256.22.0.0/1556.22.0.1 to 56.23.255.25456.23.255.255131,070
1356.24.0.0/1556.24.0.1 to 56.25.255.25456.25.255.255131,070
1456.26.0.0/1556.26.0.1 to 56.27.255.25456.27.255.255131,070
1556.28.0.0/1556.28.0.1 to 56.29.255.25456.29.255.255131,070
1656.30.0.0/1556.30.0.1 to 56.31.255.25456.31.255.255131,070
1756.32.0.0/1556.32.0.1 to 56.33.255.25456.33.255.255131,070
1856.34.0.0/1556.34.0.1 to 56.35.255.25456.35.255.255131,070
1956.36.0.0/1556.36.0.1 to 56.37.255.25456.37.255.255131,070
2056.38.0.0/1556.38.0.1 to 56.39.255.25456.39.255.255131,070
2156.40.0.0/1556.40.0.1 to 56.41.255.25456.41.255.255131,070
2256.42.0.0/1556.42.0.1 to 56.43.255.25456.43.255.255131,070
2356.44.0.0/1556.44.0.1 to 56.45.255.25456.45.255.255131,070
2456.46.0.0/1556.46.0.1 to 56.47.255.25456.47.255.255131,070
2556.48.0.0/1556.48.0.1 to 56.49.255.25456.49.255.255131,070
2656.50.0.0/1556.50.0.1 to 56.51.255.25456.51.255.255131,070
2756.52.0.0/1556.52.0.1 to 56.53.255.25456.53.255.255131,070
2856.54.0.0/1556.54.0.1 to 56.55.255.25456.55.255.255131,070
2956.56.0.0/1556.56.0.1 to 56.57.255.25456.57.255.255131,070
3056.58.0.0/1556.58.0.1 to 56.59.255.25456.59.255.255131,070
3156.60.0.0/1556.60.0.1 to 56.61.255.25456.61.255.255131,070
3256.62.0.0/1556.62.0.1 to 56.63.255.25456.63.255.255131,070
3356.64.0.0/1556.64.0.1 to 56.65.255.25456.65.255.255131,070
3456.66.0.0/1556.66.0.1 to 56.67.255.25456.67.255.255131,070
3556.68.0.0/1556.68.0.1 to 56.69.255.25456.69.255.255131,070
3656.70.0.0/1556.70.0.1 to 56.71.255.25456.71.255.255131,070
3756.72.0.0/1556.72.0.1 to 56.73.255.25456.73.255.255131,070
3856.74.0.0/1556.74.0.1 to 56.75.255.25456.75.255.255131,070
3956.76.0.0/1556.76.0.1 to 56.77.255.25456.77.255.255131,070
4056.78.0.0/1556.78.0.1 to 56.79.255.25456.79.255.255131,070
4156.80.0.0/1556.80.0.1 to 56.81.255.25456.81.255.255131,070
4256.82.0.0/1556.82.0.1 to 56.83.255.25456.83.255.255131,070
4356.84.0.0/1556.84.0.1 to 56.85.255.25456.85.255.255131,070
4456.86.0.0/1556.86.0.1 to 56.87.255.25456.87.255.255131,070
4556.88.0.0/1556.88.0.1 to 56.89.255.25456.89.255.255131,070
4656.90.0.0/1556.90.0.1 to 56.91.255.25456.91.255.255131,070
4756.92.0.0/1556.92.0.1 to 56.93.255.25456.93.255.255131,070
4856.94.0.0/1556.94.0.1 to 56.95.255.25456.95.255.255131,070
4956.96.0.0/1556.96.0.1 to 56.97.255.25456.97.255.255131,070
5056.98.0.0/1556.98.0.1 to 56.99.255.25456.99.255.255131,070
5156.100.0.0/1556.100.0.1 to 56.101.255.25456.101.255.255131,070
5256.102.0.0/1556.102.0.1 to 56.103.255.25456.103.255.255131,070
5356.104.0.0/1556.104.0.1 to 56.105.255.25456.105.255.255131,070
5456.106.0.0/1556.106.0.1 to 56.107.255.25456.107.255.255131,070
5556.108.0.0/1556.108.0.1 to 56.109.255.25456.109.255.255131,070
5656.110.0.0/1556.110.0.1 to 56.111.255.25456.111.255.255131,070
5756.112.0.0/1556.112.0.1 to 56.113.255.25456.113.255.255131,070
5856.114.0.0/1556.114.0.1 to 56.115.255.25456.115.255.255131,070
5956.116.0.0/1556.116.0.1 to 56.117.255.25456.117.255.255131,070
6056.118.0.0/1556.118.0.1 to 56.119.255.25456.119.255.255131,070
6156.120.0.0/1556.120.0.1 to 56.121.255.25456.121.255.255131,070
6256.122.0.0/1556.122.0.1 to 56.123.255.25456.123.255.255131,070
6356.124.0.0/1556.124.0.1 to 56.125.255.25456.125.255.255131,070
6456.126.0.0/1556.126.0.1 to 56.127.255.25456.127.255.255131,070
6556.128.0.0/1556.128.0.1 to 56.129.255.25456.129.255.255131,070
6656.130.0.0/1556.130.0.1 to 56.131.255.25456.131.255.255131,070
6756.132.0.0/1556.132.0.1 to 56.133.255.25456.133.255.255131,070
6856.134.0.0/1556.134.0.1 to 56.135.255.25456.135.255.255131,070
6956.136.0.0/1556.136.0.1 to 56.137.255.25456.137.255.255131,070
7056.138.0.0/1556.138.0.1 to 56.139.255.25456.139.255.255131,070
7156.140.0.0/1556.140.0.1 to 56.141.255.25456.141.255.255131,070
7256.142.0.0/1556.142.0.1 to 56.143.255.25456.143.255.255131,070
7356.144.0.0/1556.144.0.1 to 56.145.255.25456.145.255.255131,070
7456.146.0.0/1556.146.0.1 to 56.147.255.25456.147.255.255131,070
7556.148.0.0/1556.148.0.1 to 56.149.255.25456.149.255.255131,070
7656.150.0.0/1556.150.0.1 to 56.151.255.25456.151.255.255131,070
7756.152.0.0/1556.152.0.1 to 56.153.255.25456.153.255.255131,070
7856.154.0.0/1556.154.0.1 to 56.155.255.25456.155.255.255131,070
7956.156.0.0/1556.156.0.1 to 56.157.255.25456.157.255.255131,070
8056.158.0.0/1556.158.0.1 to 56.159.255.25456.159.255.255131,070
8156.160.0.0/1556.160.0.1 to 56.161.255.25456.161.255.255131,070
8256.162.0.0/1556.162.0.1 to 56.163.255.25456.163.255.255131,070
8356.164.0.0/1556.164.0.1 to 56.165.255.25456.165.255.255131,070
8456.166.0.0/1556.166.0.1 to 56.167.255.25456.167.255.255131,070
8556.168.0.0/1556.168.0.1 to 56.169.255.25456.169.255.255131,070
8656.170.0.0/1556.170.0.1 to 56.171.255.25456.171.255.255131,070
8756.172.0.0/1556.172.0.1 to 56.173.255.25456.173.255.255131,070
8856.174.0.0/1556.174.0.1 to 56.175.255.25456.175.255.255131,070
8956.176.0.0/1556.176.0.1 to 56.177.255.25456.177.255.255131,070
9056.178.0.0/1556.178.0.1 to 56.179.255.25456.179.255.255131,070
9156.180.0.0/1556.180.0.1 to 56.181.255.25456.181.255.255131,070
9256.182.0.0/1556.182.0.1 to 56.183.255.25456.183.255.255131,070
9356.184.0.0/1556.184.0.1 to 56.185.255.25456.185.255.255131,070
9456.186.0.0/1556.186.0.1 to 56.187.255.25456.187.255.255131,070
9556.188.0.0/1556.188.0.1 to 56.189.255.25456.189.255.255131,070
9656.190.0.0/1556.190.0.1 to 56.191.255.25456.191.255.255131,070
9756.192.0.0/1556.192.0.1 to 56.193.255.25456.193.255.255131,070
9856.194.0.0/1556.194.0.1 to 56.195.255.25456.195.255.255131,070
9956.196.0.0/1556.196.0.1 to 56.197.255.25456.197.255.255131,070
10056.198.0.0/1556.198.0.1 to 56.199.255.25456.199.255.255131,070
10156.200.0.0/1556.200.0.1 to 56.201.255.25456.201.255.255131,070
10256.202.0.0/1556.202.0.1 to 56.203.255.25456.203.255.255131,070
10356.204.0.0/1556.204.0.1 to 56.205.255.25456.205.255.255131,070
10456.206.0.0/1556.206.0.1 to 56.207.255.25456.207.255.255131,070
10556.208.0.0/1556.208.0.1 to 56.209.255.25456.209.255.255131,070
10656.210.0.0/1556.210.0.1 to 56.211.255.25456.211.255.255131,070
10756.212.0.0/1556.212.0.1 to 56.213.255.25456.213.255.255131,070
10856.214.0.0/1556.214.0.1 to 56.215.255.25456.215.255.255131,070
10956.216.0.0/1556.216.0.1 to 56.217.255.25456.217.255.255131,070
11056.218.0.0/1556.218.0.1 to 56.219.255.25456.219.255.255131,070
11156.220.0.0/1556.220.0.1 to 56.221.255.25456.221.255.255131,070
11256.222.0.0/1556.222.0.1 to 56.223.255.25456.223.255.255131,070
11356.224.0.0/1556.224.0.1 to 56.225.255.25456.225.255.255131,070
11456.226.0.0/1556.226.0.1 to 56.227.255.25456.227.255.255131,070
11556.228.0.0/1556.228.0.1 to 56.229.255.25456.229.255.255131,070
11656.230.0.0/1556.230.0.1 to 56.231.255.25456.231.255.255131,070
11756.232.0.0/1556.232.0.1 to 56.233.255.25456.233.255.255131,070
11856.234.0.0/1556.234.0.1 to 56.235.255.25456.235.255.255131,070
11956.236.0.0/1556.236.0.1 to 56.237.255.25456.237.255.255131,070
12056.238.0.0/1556.238.0.1 to 56.239.255.25456.239.255.255131,070
12156.240.0.0/1556.240.0.1 to 56.241.255.25456.241.255.255131,070
12256.242.0.0/1556.242.0.1 to 56.243.255.25456.243.255.255131,070
12356.244.0.0/1556.244.0.1 to 56.245.255.25456.245.255.255131,070
12456.246.0.0/1556.246.0.1 to 56.247.255.25456.247.255.255131,070
12556.248.0.0/1556.248.0.1 to 56.249.255.25456.249.255.255131,070
12656.250.0.0/1556.250.0.1 to 56.251.255.25456.251.255.255131,070
12756.252.0.0/1556.252.0.1 to 56.253.255.25456.253.255.255131,070
12856.254.0.0/1556.254.0.1 to 56.255.255.25456.255.255.255131,070
12957.0.0.0/1557.0.0.1 to 57.1.255.25457.1.255.255131,070
13057.2.0.0/1557.2.0.1 to 57.3.255.25457.3.255.255131,070
13157.4.0.0/1557.4.0.1 to 57.5.255.25457.5.255.255131,070
13257.6.0.0/1557.6.0.1 to 57.7.255.25457.7.255.255131,070
13357.8.0.0/1557.8.0.1 to 57.9.255.25457.9.255.255131,070
13457.10.0.0/1557.10.0.1 to 57.11.255.25457.11.255.255131,070
13557.12.0.0/1557.12.0.1 to 57.13.255.25457.13.255.255131,070
13657.14.0.0/1557.14.0.1 to 57.15.255.25457.15.255.255131,070
13757.16.0.0/1557.16.0.1 to 57.17.255.25457.17.255.255131,070
13857.18.0.0/1557.18.0.1 to 57.19.255.25457.19.255.255131,070
13957.20.0.0/1557.20.0.1 to 57.21.255.25457.21.255.255131,070
14057.22.0.0/1557.22.0.1 to 57.23.255.25457.23.255.255131,070
14157.24.0.0/1557.24.0.1 to 57.25.255.25457.25.255.255131,070
14257.26.0.0/1557.26.0.1 to 57.27.255.25457.27.255.255131,070
14357.28.0.0/1557.28.0.1 to 57.29.255.25457.29.255.255131,070
14457.30.0.0/1557.30.0.1 to 57.31.255.25457.31.255.255131,070
14557.32.0.0/1557.32.0.1 to 57.33.255.25457.33.255.255131,070
14657.34.0.0/1557.34.0.1 to 57.35.255.25457.35.255.255131,070
14757.36.0.0/1557.36.0.1 to 57.37.255.25457.37.255.255131,070
14857.38.0.0/1557.38.0.1 to 57.39.255.25457.39.255.255131,070
14957.40.0.0/1557.40.0.1 to 57.41.255.25457.41.255.255131,070
15057.42.0.0/1557.42.0.1 to 57.43.255.25457.43.255.255131,070
15157.44.0.0/1557.44.0.1 to 57.45.255.25457.45.255.255131,070
15257.46.0.0/1557.46.0.1 to 57.47.255.25457.47.255.255131,070
15357.48.0.0/1557.48.0.1 to 57.49.255.25457.49.255.255131,070
15457.50.0.0/1557.50.0.1 to 57.51.255.25457.51.255.255131,070
15557.52.0.0/1557.52.0.1 to 57.53.255.25457.53.255.255131,070
15657.54.0.0/1557.54.0.1 to 57.55.255.25457.55.255.255131,070
15757.56.0.0/1557.56.0.1 to 57.57.255.25457.57.255.255131,070
15857.58.0.0/1557.58.0.1 to 57.59.255.25457.59.255.255131,070
15957.60.0.0/1557.60.0.1 to 57.61.255.25457.61.255.255131,070
16057.62.0.0/1557.62.0.1 to 57.63.255.25457.63.255.255131,070
16157.64.0.0/1557.64.0.1 to 57.65.255.25457.65.255.255131,070
16257.66.0.0/1557.66.0.1 to 57.67.255.25457.67.255.255131,070
16357.68.0.0/1557.68.0.1 to 57.69.255.25457.69.255.255131,070
16457.70.0.0/1557.70.0.1 to 57.71.255.25457.71.255.255131,070
16557.72.0.0/1557.72.0.1 to 57.73.255.25457.73.255.255131,070
16657.74.0.0/1557.74.0.1 to 57.75.255.25457.75.255.255131,070
16757.76.0.0/1557.76.0.1 to 57.77.255.25457.77.255.255131,070
16857.78.0.0/1557.78.0.1 to 57.79.255.25457.79.255.255131,070
16957.80.0.0/1557.80.0.1 to 57.81.255.25457.81.255.255131,070
17057.82.0.0/1557.82.0.1 to 57.83.255.25457.83.255.255131,070
17157.84.0.0/1557.84.0.1 to 57.85.255.25457.85.255.255131,070
17257.86.0.0/1557.86.0.1 to 57.87.255.25457.87.255.255131,070
17357.88.0.0/1557.88.0.1 to 57.89.255.25457.89.255.255131,070
17457.90.0.0/1557.90.0.1 to 57.91.255.25457.91.255.255131,070
17557.92.0.0/1557.92.0.1 to 57.93.255.25457.93.255.255131,070
17657.94.0.0/1557.94.0.1 to 57.95.255.25457.95.255.255131,070
17757.96.0.0/1557.96.0.1 to 57.97.255.25457.97.255.255131,070
17857.98.0.0/1557.98.0.1 to 57.99.255.25457.99.255.255131,070
17957.100.0.0/1557.100.0.1 to 57.101.255.25457.101.255.255131,070
18057.102.0.0/1557.102.0.1 to 57.103.255.25457.103.255.255131,070
18157.104.0.0/1557.104.0.1 to 57.105.255.25457.105.255.255131,070
18257.106.0.0/1557.106.0.1 to 57.107.255.25457.107.255.255131,070
18357.108.0.0/1557.108.0.1 to 57.109.255.25457.109.255.255131,070
18457.110.0.0/1557.110.0.1 to 57.111.255.25457.111.255.255131,070
18557.112.0.0/1557.112.0.1 to 57.113.255.25457.113.255.255131,070
18657.114.0.0/1557.114.0.1 to 57.115.255.25457.115.255.255131,070
18757.116.0.0/1557.116.0.1 to 57.117.255.25457.117.255.255131,070
18857.118.0.0/1557.118.0.1 to 57.119.255.25457.119.255.255131,070
18957.120.0.0/1557.120.0.1 to 57.121.255.25457.121.255.255131,070
19057.122.0.0/1557.122.0.1 to 57.123.255.25457.123.255.255131,070
19157.124.0.0/1557.124.0.1 to 57.125.255.25457.125.255.255131,070
19257.126.0.0/1557.126.0.1 to 57.127.255.25457.127.255.255131,070
19357.128.0.0/1557.128.0.1 to 57.129.255.25457.129.255.255131,070
19457.130.0.0/1557.130.0.1 to 57.131.255.25457.131.255.255131,070
19557.132.0.0/1557.132.0.1 to 57.133.255.25457.133.255.255131,070
19657.134.0.0/1557.134.0.1 to 57.135.255.25457.135.255.255131,070
19757.136.0.0/1557.136.0.1 to 57.137.255.25457.137.255.255131,070
19857.138.0.0/1557.138.0.1 to 57.139.255.25457.139.255.255131,070
19957.140.0.0/1557.140.0.1 to 57.141.255.25457.141.255.255131,070
20057.142.0.0/1557.142.0.1 to 57.143.255.25457.143.255.255131,070
20157.144.0.0/1557.144.0.1 to 57.145.255.25457.145.255.255131,070
20257.146.0.0/1557.146.0.1 to 57.147.255.25457.147.255.255131,070
20357.148.0.0/1557.148.0.1 to 57.149.255.25457.149.255.255131,070
20457.150.0.0/1557.150.0.1 to 57.151.255.25457.151.255.255131,070
20557.152.0.0/1557.152.0.1 to 57.153.255.25457.153.255.255131,070
20657.154.0.0/1557.154.0.1 to 57.155.255.25457.155.255.255131,070
20757.156.0.0/1557.156.0.1 to 57.157.255.25457.157.255.255131,070
20857.158.0.0/1557.158.0.1 to 57.159.255.25457.159.255.255131,070
20957.160.0.0/1557.160.0.1 to 57.161.255.25457.161.255.255131,070
21057.162.0.0/1557.162.0.1 to 57.163.255.25457.163.255.255131,070
21157.164.0.0/1557.164.0.1 to 57.165.255.25457.165.255.255131,070
21257.166.0.0/1557.166.0.1 to 57.167.255.25457.167.255.255131,070
21357.168.0.0/1557.168.0.1 to 57.169.255.25457.169.255.255131,070
21457.170.0.0/1557.170.0.1 to 57.171.255.25457.171.255.255131,070
21557.172.0.0/1557.172.0.1 to 57.173.255.25457.173.255.255131,070
21657.174.0.0/1557.174.0.1 to 57.175.255.25457.175.255.255131,070
21757.176.0.0/1557.176.0.1 to 57.177.255.25457.177.255.255131,070
21857.178.0.0/1557.178.0.1 to 57.179.255.25457.179.255.255131,070
21957.180.0.0/1557.180.0.1 to 57.181.255.25457.181.255.255131,070
22057.182.0.0/1557.182.0.1 to 57.183.255.25457.183.255.255131,070
22157.184.0.0/1557.184.0.1 to 57.185.255.25457.185.255.255131,070
22257.186.0.0/1557.186.0.1 to 57.187.255.25457.187.255.255131,070
22357.188.0.0/1557.188.0.1 to 57.189.255.25457.189.255.255131,070
22457.190.0.0/1557.190.0.1 to 57.191.255.25457.191.255.255131,070
22557.192.0.0/1557.192.0.1 to 57.193.255.25457.193.255.255131,070
22657.194.0.0/1557.194.0.1 to 57.195.255.25457.195.255.255131,070
22757.196.0.0/1557.196.0.1 to 57.197.255.25457.197.255.255131,070
22857.198.0.0/1557.198.0.1 to 57.199.255.25457.199.255.255131,070
22957.200.0.0/1557.200.0.1 to 57.201.255.25457.201.255.255131,070
23057.202.0.0/1557.202.0.1 to 57.203.255.25457.203.255.255131,070
23157.204.0.0/1557.204.0.1 to 57.205.255.25457.205.255.255131,070
23257.206.0.0/1557.206.0.1 to 57.207.255.25457.207.255.255131,070
23357.208.0.0/1557.208.0.1 to 57.209.255.25457.209.255.255131,070
23457.210.0.0/1557.210.0.1 to 57.211.255.25457.211.255.255131,070
23557.212.0.0/1557.212.0.1 to 57.213.255.25457.213.255.255131,070
23657.214.0.0/1557.214.0.1 to 57.215.255.25457.215.255.255131,070
23757.216.0.0/1557.216.0.1 to 57.217.255.25457.217.255.255131,070
23857.218.0.0/1557.218.0.1 to 57.219.255.25457.219.255.255131,070
23957.220.0.0/1557.220.0.1 to 57.221.255.25457.221.255.255131,070
24057.222.0.0/1557.222.0.1 to 57.223.255.25457.223.255.255131,070
24157.224.0.0/1557.224.0.1 to 57.225.255.25457.225.255.255131,070
24257.226.0.0/1557.226.0.1 to 57.227.255.25457.227.255.255131,070
24357.228.0.0/1557.228.0.1 to 57.229.255.25457.229.255.255131,070
24457.230.0.0/1557.230.0.1 to 57.231.255.25457.231.255.255131,070
24557.232.0.0/1557.232.0.1 to 57.233.255.25457.233.255.255131,070
24657.234.0.0/1557.234.0.1 to 57.235.255.25457.235.255.255131,070
24757.236.0.0/1557.236.0.1 to 57.237.255.25457.237.255.255131,070
24857.238.0.0/1557.238.0.1 to 57.239.255.25457.239.255.255131,070
24957.240.0.0/1557.240.0.1 to 57.241.255.25457.241.255.255131,070
25057.242.0.0/1557.242.0.1 to 57.243.255.25457.243.255.255131,070
25157.244.0.0/1557.244.0.1 to 57.245.255.25457.245.255.255131,070
25257.246.0.0/1557.246.0.1 to 57.247.255.25457.247.255.255131,070
25357.248.0.0/1557.248.0.1 to 57.249.255.25457.249.255.255131,070
25457.250.0.0/1557.250.0.1 to 57.251.255.25457.251.255.255131,070
25557.252.0.0/1557.252.0.1 to 57.253.255.25457.253.255.255131,070
25657.254.0.0/1557.254.0.1 to 57.255.255.25457.255.255.255131,070

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.