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.

Network23.96.0.0/11
Usable hosts2,097,150
Subnet mask255.224.0.0
Addresses2,097,152
Network address
23.96.0.0
Broadcast address
23.127.255.255
First usable
23.96.0.1
Last usable
23.127.255.254
Usable hosts
2,097,150 (2,097,152 less the network and broadcast addresses)
Subnet mask
255.224.0.0
Wildcard mask
0.31.255.255 (Cisco ACLs, OSPF)
Prefix length
/11
Type
Public public
Old class
A (default /8)
As numbers
Hex 17600000 · Integer 392167424 to 394264575
Reverse DNS zones
96.23.in-addr.arpa
97.23.in-addr.arpa
98.23.in-addr.arpa
99.23.in-addr.arpa
100.23.in-addr.arpa
101.23.in-addr.arpa
102.23.in-addr.arpa
103.23.in-addr.arpa
104.23.in-addr.arpa
105.23.in-addr.arpa
106.23.in-addr.arpa
107.23.in-addr.arpa
108.23.in-addr.arpa
109.23.in-addr.arpa
110.23.in-addr.arpa
111.23.in-addr.arpa
and 16 more
/11 is not on a 8-bit boundary, so it takes 32 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00010111.01100000.00000000.0000000023.96.0.0
Subnet mask11111111.11100000.00000000.00000000255.224.0.0
Network00010111.01100000.00000000.0000000023.96.0.0
Broadcast00010111.01111111.11111111.1111111123.127.255.255
Split into smaller subnets/23
/12 (2)/13 (4)/14 (8)/15 (16)/16 (32)/17 (64)/18 (128)/19 (256)/20 (512)/21 (1,024)/22 (2,048)/23 (4,096)

23.96.0.0/11 makes 4,096 subnets of /23; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
123.96.0.0/2323.96.0.1 to 23.96.1.25423.96.1.255510
223.96.2.0/2323.96.2.1 to 23.96.3.25423.96.3.255510
323.96.4.0/2323.96.4.1 to 23.96.5.25423.96.5.255510
423.96.6.0/2323.96.6.1 to 23.96.7.25423.96.7.255510
523.96.8.0/2323.96.8.1 to 23.96.9.25423.96.9.255510
623.96.10.0/2323.96.10.1 to 23.96.11.25423.96.11.255510
723.96.12.0/2323.96.12.1 to 23.96.13.25423.96.13.255510
823.96.14.0/2323.96.14.1 to 23.96.15.25423.96.15.255510
923.96.16.0/2323.96.16.1 to 23.96.17.25423.96.17.255510
1023.96.18.0/2323.96.18.1 to 23.96.19.25423.96.19.255510
1123.96.20.0/2323.96.20.1 to 23.96.21.25423.96.21.255510
1223.96.22.0/2323.96.22.1 to 23.96.23.25423.96.23.255510
1323.96.24.0/2323.96.24.1 to 23.96.25.25423.96.25.255510
1423.96.26.0/2323.96.26.1 to 23.96.27.25423.96.27.255510
1523.96.28.0/2323.96.28.1 to 23.96.29.25423.96.29.255510
1623.96.30.0/2323.96.30.1 to 23.96.31.25423.96.31.255510
1723.96.32.0/2323.96.32.1 to 23.96.33.25423.96.33.255510
1823.96.34.0/2323.96.34.1 to 23.96.35.25423.96.35.255510
1923.96.36.0/2323.96.36.1 to 23.96.37.25423.96.37.255510
2023.96.38.0/2323.96.38.1 to 23.96.39.25423.96.39.255510
2123.96.40.0/2323.96.40.1 to 23.96.41.25423.96.41.255510
2223.96.42.0/2323.96.42.1 to 23.96.43.25423.96.43.255510
2323.96.44.0/2323.96.44.1 to 23.96.45.25423.96.45.255510
2423.96.46.0/2323.96.46.1 to 23.96.47.25423.96.47.255510
2523.96.48.0/2323.96.48.1 to 23.96.49.25423.96.49.255510
2623.96.50.0/2323.96.50.1 to 23.96.51.25423.96.51.255510
2723.96.52.0/2323.96.52.1 to 23.96.53.25423.96.53.255510
2823.96.54.0/2323.96.54.1 to 23.96.55.25423.96.55.255510
2923.96.56.0/2323.96.56.1 to 23.96.57.25423.96.57.255510
3023.96.58.0/2323.96.58.1 to 23.96.59.25423.96.59.255510
3123.96.60.0/2323.96.60.1 to 23.96.61.25423.96.61.255510
3223.96.62.0/2323.96.62.1 to 23.96.63.25423.96.63.255510
3323.96.64.0/2323.96.64.1 to 23.96.65.25423.96.65.255510
3423.96.66.0/2323.96.66.1 to 23.96.67.25423.96.67.255510
3523.96.68.0/2323.96.68.1 to 23.96.69.25423.96.69.255510
3623.96.70.0/2323.96.70.1 to 23.96.71.25423.96.71.255510
3723.96.72.0/2323.96.72.1 to 23.96.73.25423.96.73.255510
3823.96.74.0/2323.96.74.1 to 23.96.75.25423.96.75.255510
3923.96.76.0/2323.96.76.1 to 23.96.77.25423.96.77.255510
4023.96.78.0/2323.96.78.1 to 23.96.79.25423.96.79.255510
4123.96.80.0/2323.96.80.1 to 23.96.81.25423.96.81.255510
4223.96.82.0/2323.96.82.1 to 23.96.83.25423.96.83.255510
4323.96.84.0/2323.96.84.1 to 23.96.85.25423.96.85.255510
4423.96.86.0/2323.96.86.1 to 23.96.87.25423.96.87.255510
4523.96.88.0/2323.96.88.1 to 23.96.89.25423.96.89.255510
4623.96.90.0/2323.96.90.1 to 23.96.91.25423.96.91.255510
4723.96.92.0/2323.96.92.1 to 23.96.93.25423.96.93.255510
4823.96.94.0/2323.96.94.1 to 23.96.95.25423.96.95.255510
4923.96.96.0/2323.96.96.1 to 23.96.97.25423.96.97.255510
5023.96.98.0/2323.96.98.1 to 23.96.99.25423.96.99.255510
5123.96.100.0/2323.96.100.1 to 23.96.101.25423.96.101.255510
5223.96.102.0/2323.96.102.1 to 23.96.103.25423.96.103.255510
5323.96.104.0/2323.96.104.1 to 23.96.105.25423.96.105.255510
5423.96.106.0/2323.96.106.1 to 23.96.107.25423.96.107.255510
5523.96.108.0/2323.96.108.1 to 23.96.109.25423.96.109.255510
5623.96.110.0/2323.96.110.1 to 23.96.111.25423.96.111.255510
5723.96.112.0/2323.96.112.1 to 23.96.113.25423.96.113.255510
5823.96.114.0/2323.96.114.1 to 23.96.115.25423.96.115.255510
5923.96.116.0/2323.96.116.1 to 23.96.117.25423.96.117.255510
6023.96.118.0/2323.96.118.1 to 23.96.119.25423.96.119.255510
6123.96.120.0/2323.96.120.1 to 23.96.121.25423.96.121.255510
6223.96.122.0/2323.96.122.1 to 23.96.123.25423.96.123.255510
6323.96.124.0/2323.96.124.1 to 23.96.125.25423.96.125.255510
6423.96.126.0/2323.96.126.1 to 23.96.127.25423.96.127.255510
6523.96.128.0/2323.96.128.1 to 23.96.129.25423.96.129.255510
6623.96.130.0/2323.96.130.1 to 23.96.131.25423.96.131.255510
6723.96.132.0/2323.96.132.1 to 23.96.133.25423.96.133.255510
6823.96.134.0/2323.96.134.1 to 23.96.135.25423.96.135.255510
6923.96.136.0/2323.96.136.1 to 23.96.137.25423.96.137.255510
7023.96.138.0/2323.96.138.1 to 23.96.139.25423.96.139.255510
7123.96.140.0/2323.96.140.1 to 23.96.141.25423.96.141.255510
7223.96.142.0/2323.96.142.1 to 23.96.143.25423.96.143.255510
7323.96.144.0/2323.96.144.1 to 23.96.145.25423.96.145.255510
7423.96.146.0/2323.96.146.1 to 23.96.147.25423.96.147.255510
7523.96.148.0/2323.96.148.1 to 23.96.149.25423.96.149.255510
7623.96.150.0/2323.96.150.1 to 23.96.151.25423.96.151.255510
7723.96.152.0/2323.96.152.1 to 23.96.153.25423.96.153.255510
7823.96.154.0/2323.96.154.1 to 23.96.155.25423.96.155.255510
7923.96.156.0/2323.96.156.1 to 23.96.157.25423.96.157.255510
8023.96.158.0/2323.96.158.1 to 23.96.159.25423.96.159.255510
8123.96.160.0/2323.96.160.1 to 23.96.161.25423.96.161.255510
8223.96.162.0/2323.96.162.1 to 23.96.163.25423.96.163.255510
8323.96.164.0/2323.96.164.1 to 23.96.165.25423.96.165.255510
8423.96.166.0/2323.96.166.1 to 23.96.167.25423.96.167.255510
8523.96.168.0/2323.96.168.1 to 23.96.169.25423.96.169.255510
8623.96.170.0/2323.96.170.1 to 23.96.171.25423.96.171.255510
8723.96.172.0/2323.96.172.1 to 23.96.173.25423.96.173.255510
8823.96.174.0/2323.96.174.1 to 23.96.175.25423.96.175.255510
8923.96.176.0/2323.96.176.1 to 23.96.177.25423.96.177.255510
9023.96.178.0/2323.96.178.1 to 23.96.179.25423.96.179.255510
9123.96.180.0/2323.96.180.1 to 23.96.181.25423.96.181.255510
9223.96.182.0/2323.96.182.1 to 23.96.183.25423.96.183.255510
9323.96.184.0/2323.96.184.1 to 23.96.185.25423.96.185.255510
9423.96.186.0/2323.96.186.1 to 23.96.187.25423.96.187.255510
9523.96.188.0/2323.96.188.1 to 23.96.189.25423.96.189.255510
9623.96.190.0/2323.96.190.1 to 23.96.191.25423.96.191.255510
9723.96.192.0/2323.96.192.1 to 23.96.193.25423.96.193.255510
9823.96.194.0/2323.96.194.1 to 23.96.195.25423.96.195.255510
9923.96.196.0/2323.96.196.1 to 23.96.197.25423.96.197.255510
10023.96.198.0/2323.96.198.1 to 23.96.199.25423.96.199.255510
10123.96.200.0/2323.96.200.1 to 23.96.201.25423.96.201.255510
10223.96.202.0/2323.96.202.1 to 23.96.203.25423.96.203.255510
10323.96.204.0/2323.96.204.1 to 23.96.205.25423.96.205.255510
10423.96.206.0/2323.96.206.1 to 23.96.207.25423.96.207.255510
10523.96.208.0/2323.96.208.1 to 23.96.209.25423.96.209.255510
10623.96.210.0/2323.96.210.1 to 23.96.211.25423.96.211.255510
10723.96.212.0/2323.96.212.1 to 23.96.213.25423.96.213.255510
10823.96.214.0/2323.96.214.1 to 23.96.215.25423.96.215.255510
10923.96.216.0/2323.96.216.1 to 23.96.217.25423.96.217.255510
11023.96.218.0/2323.96.218.1 to 23.96.219.25423.96.219.255510
11123.96.220.0/2323.96.220.1 to 23.96.221.25423.96.221.255510
11223.96.222.0/2323.96.222.1 to 23.96.223.25423.96.223.255510
11323.96.224.0/2323.96.224.1 to 23.96.225.25423.96.225.255510
11423.96.226.0/2323.96.226.1 to 23.96.227.25423.96.227.255510
11523.96.228.0/2323.96.228.1 to 23.96.229.25423.96.229.255510
11623.96.230.0/2323.96.230.1 to 23.96.231.25423.96.231.255510
11723.96.232.0/2323.96.232.1 to 23.96.233.25423.96.233.255510
11823.96.234.0/2323.96.234.1 to 23.96.235.25423.96.235.255510
11923.96.236.0/2323.96.236.1 to 23.96.237.25423.96.237.255510
12023.96.238.0/2323.96.238.1 to 23.96.239.25423.96.239.255510
12123.96.240.0/2323.96.240.1 to 23.96.241.25423.96.241.255510
12223.96.242.0/2323.96.242.1 to 23.96.243.25423.96.243.255510
12323.96.244.0/2323.96.244.1 to 23.96.245.25423.96.245.255510
12423.96.246.0/2323.96.246.1 to 23.96.247.25423.96.247.255510
12523.96.248.0/2323.96.248.1 to 23.96.249.25423.96.249.255510
12623.96.250.0/2323.96.250.1 to 23.96.251.25423.96.251.255510
12723.96.252.0/2323.96.252.1 to 23.96.253.25423.96.253.255510
12823.96.254.0/2323.96.254.1 to 23.96.255.25423.96.255.255510
12923.97.0.0/2323.97.0.1 to 23.97.1.25423.97.1.255510
13023.97.2.0/2323.97.2.1 to 23.97.3.25423.97.3.255510
13123.97.4.0/2323.97.4.1 to 23.97.5.25423.97.5.255510
13223.97.6.0/2323.97.6.1 to 23.97.7.25423.97.7.255510
13323.97.8.0/2323.97.8.1 to 23.97.9.25423.97.9.255510
13423.97.10.0/2323.97.10.1 to 23.97.11.25423.97.11.255510
13523.97.12.0/2323.97.12.1 to 23.97.13.25423.97.13.255510
13623.97.14.0/2323.97.14.1 to 23.97.15.25423.97.15.255510
13723.97.16.0/2323.97.16.1 to 23.97.17.25423.97.17.255510
13823.97.18.0/2323.97.18.1 to 23.97.19.25423.97.19.255510
13923.97.20.0/2323.97.20.1 to 23.97.21.25423.97.21.255510
14023.97.22.0/2323.97.22.1 to 23.97.23.25423.97.23.255510
14123.97.24.0/2323.97.24.1 to 23.97.25.25423.97.25.255510
14223.97.26.0/2323.97.26.1 to 23.97.27.25423.97.27.255510
14323.97.28.0/2323.97.28.1 to 23.97.29.25423.97.29.255510
14423.97.30.0/2323.97.30.1 to 23.97.31.25423.97.31.255510
14523.97.32.0/2323.97.32.1 to 23.97.33.25423.97.33.255510
14623.97.34.0/2323.97.34.1 to 23.97.35.25423.97.35.255510
14723.97.36.0/2323.97.36.1 to 23.97.37.25423.97.37.255510
14823.97.38.0/2323.97.38.1 to 23.97.39.25423.97.39.255510
14923.97.40.0/2323.97.40.1 to 23.97.41.25423.97.41.255510
15023.97.42.0/2323.97.42.1 to 23.97.43.25423.97.43.255510
15123.97.44.0/2323.97.44.1 to 23.97.45.25423.97.45.255510
15223.97.46.0/2323.97.46.1 to 23.97.47.25423.97.47.255510
15323.97.48.0/2323.97.48.1 to 23.97.49.25423.97.49.255510
15423.97.50.0/2323.97.50.1 to 23.97.51.25423.97.51.255510
15523.97.52.0/2323.97.52.1 to 23.97.53.25423.97.53.255510
15623.97.54.0/2323.97.54.1 to 23.97.55.25423.97.55.255510
15723.97.56.0/2323.97.56.1 to 23.97.57.25423.97.57.255510
15823.97.58.0/2323.97.58.1 to 23.97.59.25423.97.59.255510
15923.97.60.0/2323.97.60.1 to 23.97.61.25423.97.61.255510
16023.97.62.0/2323.97.62.1 to 23.97.63.25423.97.63.255510
16123.97.64.0/2323.97.64.1 to 23.97.65.25423.97.65.255510
16223.97.66.0/2323.97.66.1 to 23.97.67.25423.97.67.255510
16323.97.68.0/2323.97.68.1 to 23.97.69.25423.97.69.255510
16423.97.70.0/2323.97.70.1 to 23.97.71.25423.97.71.255510
16523.97.72.0/2323.97.72.1 to 23.97.73.25423.97.73.255510
16623.97.74.0/2323.97.74.1 to 23.97.75.25423.97.75.255510
16723.97.76.0/2323.97.76.1 to 23.97.77.25423.97.77.255510
16823.97.78.0/2323.97.78.1 to 23.97.79.25423.97.79.255510
16923.97.80.0/2323.97.80.1 to 23.97.81.25423.97.81.255510
17023.97.82.0/2323.97.82.1 to 23.97.83.25423.97.83.255510
17123.97.84.0/2323.97.84.1 to 23.97.85.25423.97.85.255510
17223.97.86.0/2323.97.86.1 to 23.97.87.25423.97.87.255510
17323.97.88.0/2323.97.88.1 to 23.97.89.25423.97.89.255510
17423.97.90.0/2323.97.90.1 to 23.97.91.25423.97.91.255510
17523.97.92.0/2323.97.92.1 to 23.97.93.25423.97.93.255510
17623.97.94.0/2323.97.94.1 to 23.97.95.25423.97.95.255510
17723.97.96.0/2323.97.96.1 to 23.97.97.25423.97.97.255510
17823.97.98.0/2323.97.98.1 to 23.97.99.25423.97.99.255510
17923.97.100.0/2323.97.100.1 to 23.97.101.25423.97.101.255510
18023.97.102.0/2323.97.102.1 to 23.97.103.25423.97.103.255510
18123.97.104.0/2323.97.104.1 to 23.97.105.25423.97.105.255510
18223.97.106.0/2323.97.106.1 to 23.97.107.25423.97.107.255510
18323.97.108.0/2323.97.108.1 to 23.97.109.25423.97.109.255510
18423.97.110.0/2323.97.110.1 to 23.97.111.25423.97.111.255510
18523.97.112.0/2323.97.112.1 to 23.97.113.25423.97.113.255510
18623.97.114.0/2323.97.114.1 to 23.97.115.25423.97.115.255510
18723.97.116.0/2323.97.116.1 to 23.97.117.25423.97.117.255510
18823.97.118.0/2323.97.118.1 to 23.97.119.25423.97.119.255510
18923.97.120.0/2323.97.120.1 to 23.97.121.25423.97.121.255510
19023.97.122.0/2323.97.122.1 to 23.97.123.25423.97.123.255510
19123.97.124.0/2323.97.124.1 to 23.97.125.25423.97.125.255510
19223.97.126.0/2323.97.126.1 to 23.97.127.25423.97.127.255510
19323.97.128.0/2323.97.128.1 to 23.97.129.25423.97.129.255510
19423.97.130.0/2323.97.130.1 to 23.97.131.25423.97.131.255510
19523.97.132.0/2323.97.132.1 to 23.97.133.25423.97.133.255510
19623.97.134.0/2323.97.134.1 to 23.97.135.25423.97.135.255510
19723.97.136.0/2323.97.136.1 to 23.97.137.25423.97.137.255510
19823.97.138.0/2323.97.138.1 to 23.97.139.25423.97.139.255510
19923.97.140.0/2323.97.140.1 to 23.97.141.25423.97.141.255510
20023.97.142.0/2323.97.142.1 to 23.97.143.25423.97.143.255510
20123.97.144.0/2323.97.144.1 to 23.97.145.25423.97.145.255510
20223.97.146.0/2323.97.146.1 to 23.97.147.25423.97.147.255510
20323.97.148.0/2323.97.148.1 to 23.97.149.25423.97.149.255510
20423.97.150.0/2323.97.150.1 to 23.97.151.25423.97.151.255510
20523.97.152.0/2323.97.152.1 to 23.97.153.25423.97.153.255510
20623.97.154.0/2323.97.154.1 to 23.97.155.25423.97.155.255510
20723.97.156.0/2323.97.156.1 to 23.97.157.25423.97.157.255510
20823.97.158.0/2323.97.158.1 to 23.97.159.25423.97.159.255510
20923.97.160.0/2323.97.160.1 to 23.97.161.25423.97.161.255510
21023.97.162.0/2323.97.162.1 to 23.97.163.25423.97.163.255510
21123.97.164.0/2323.97.164.1 to 23.97.165.25423.97.165.255510
21223.97.166.0/2323.97.166.1 to 23.97.167.25423.97.167.255510
21323.97.168.0/2323.97.168.1 to 23.97.169.25423.97.169.255510
21423.97.170.0/2323.97.170.1 to 23.97.171.25423.97.171.255510
21523.97.172.0/2323.97.172.1 to 23.97.173.25423.97.173.255510
21623.97.174.0/2323.97.174.1 to 23.97.175.25423.97.175.255510
21723.97.176.0/2323.97.176.1 to 23.97.177.25423.97.177.255510
21823.97.178.0/2323.97.178.1 to 23.97.179.25423.97.179.255510
21923.97.180.0/2323.97.180.1 to 23.97.181.25423.97.181.255510
22023.97.182.0/2323.97.182.1 to 23.97.183.25423.97.183.255510
22123.97.184.0/2323.97.184.1 to 23.97.185.25423.97.185.255510
22223.97.186.0/2323.97.186.1 to 23.97.187.25423.97.187.255510
22323.97.188.0/2323.97.188.1 to 23.97.189.25423.97.189.255510
22423.97.190.0/2323.97.190.1 to 23.97.191.25423.97.191.255510
22523.97.192.0/2323.97.192.1 to 23.97.193.25423.97.193.255510
22623.97.194.0/2323.97.194.1 to 23.97.195.25423.97.195.255510
22723.97.196.0/2323.97.196.1 to 23.97.197.25423.97.197.255510
22823.97.198.0/2323.97.198.1 to 23.97.199.25423.97.199.255510
22923.97.200.0/2323.97.200.1 to 23.97.201.25423.97.201.255510
23023.97.202.0/2323.97.202.1 to 23.97.203.25423.97.203.255510
23123.97.204.0/2323.97.204.1 to 23.97.205.25423.97.205.255510
23223.97.206.0/2323.97.206.1 to 23.97.207.25423.97.207.255510
23323.97.208.0/2323.97.208.1 to 23.97.209.25423.97.209.255510
23423.97.210.0/2323.97.210.1 to 23.97.211.25423.97.211.255510
23523.97.212.0/2323.97.212.1 to 23.97.213.25423.97.213.255510
23623.97.214.0/2323.97.214.1 to 23.97.215.25423.97.215.255510
23723.97.216.0/2323.97.216.1 to 23.97.217.25423.97.217.255510
23823.97.218.0/2323.97.218.1 to 23.97.219.25423.97.219.255510
23923.97.220.0/2323.97.220.1 to 23.97.221.25423.97.221.255510
24023.97.222.0/2323.97.222.1 to 23.97.223.25423.97.223.255510
24123.97.224.0/2323.97.224.1 to 23.97.225.25423.97.225.255510
24223.97.226.0/2323.97.226.1 to 23.97.227.25423.97.227.255510
24323.97.228.0/2323.97.228.1 to 23.97.229.25423.97.229.255510
24423.97.230.0/2323.97.230.1 to 23.97.231.25423.97.231.255510
24523.97.232.0/2323.97.232.1 to 23.97.233.25423.97.233.255510
24623.97.234.0/2323.97.234.1 to 23.97.235.25423.97.235.255510
24723.97.236.0/2323.97.236.1 to 23.97.237.25423.97.237.255510
24823.97.238.0/2323.97.238.1 to 23.97.239.25423.97.239.255510
24923.97.240.0/2323.97.240.1 to 23.97.241.25423.97.241.255510
25023.97.242.0/2323.97.242.1 to 23.97.243.25423.97.243.255510
25123.97.244.0/2323.97.244.1 to 23.97.245.25423.97.245.255510
25223.97.246.0/2323.97.246.1 to 23.97.247.25423.97.247.255510
25323.97.248.0/2323.97.248.1 to 23.97.249.25423.97.249.255510
25423.97.250.0/2323.97.250.1 to 23.97.251.25423.97.251.255510
25523.97.252.0/2323.97.252.1 to 23.97.253.25423.97.253.255510
25623.97.254.0/2323.97.254.1 to 23.97.255.25423.97.255.255510

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.