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.

Network30.2.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
30.2.0.0
Broadcast address
30.3.255.255
First usable
30.2.0.1
Last usable
30.3.255.254
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 1E020000 · Integer 503447552 to 503578623
Reverse DNS zones
2.30.in-addr.arpa
3.30.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
Address00011110.00000010.00000000.0000000030.2.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network00011110.00000010.00000000.0000000030.2.0.0
Broadcast00011110.00000011.11111111.1111111130.3.255.255
Split into smaller subnets/23
/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)

30.2.0.0/15 makes 256 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
130.2.0.0/2330.2.0.1 to 30.2.1.25430.2.1.255510
230.2.2.0/2330.2.2.1 to 30.2.3.25430.2.3.255510
330.2.4.0/2330.2.4.1 to 30.2.5.25430.2.5.255510
430.2.6.0/2330.2.6.1 to 30.2.7.25430.2.7.255510
530.2.8.0/2330.2.8.1 to 30.2.9.25430.2.9.255510
630.2.10.0/2330.2.10.1 to 30.2.11.25430.2.11.255510
730.2.12.0/2330.2.12.1 to 30.2.13.25430.2.13.255510
830.2.14.0/2330.2.14.1 to 30.2.15.25430.2.15.255510
930.2.16.0/2330.2.16.1 to 30.2.17.25430.2.17.255510
1030.2.18.0/2330.2.18.1 to 30.2.19.25430.2.19.255510
1130.2.20.0/2330.2.20.1 to 30.2.21.25430.2.21.255510
1230.2.22.0/2330.2.22.1 to 30.2.23.25430.2.23.255510
1330.2.24.0/2330.2.24.1 to 30.2.25.25430.2.25.255510
1430.2.26.0/2330.2.26.1 to 30.2.27.25430.2.27.255510
1530.2.28.0/2330.2.28.1 to 30.2.29.25430.2.29.255510
1630.2.30.0/2330.2.30.1 to 30.2.31.25430.2.31.255510
1730.2.32.0/2330.2.32.1 to 30.2.33.25430.2.33.255510
1830.2.34.0/2330.2.34.1 to 30.2.35.25430.2.35.255510
1930.2.36.0/2330.2.36.1 to 30.2.37.25430.2.37.255510
2030.2.38.0/2330.2.38.1 to 30.2.39.25430.2.39.255510
2130.2.40.0/2330.2.40.1 to 30.2.41.25430.2.41.255510
2230.2.42.0/2330.2.42.1 to 30.2.43.25430.2.43.255510
2330.2.44.0/2330.2.44.1 to 30.2.45.25430.2.45.255510
2430.2.46.0/2330.2.46.1 to 30.2.47.25430.2.47.255510
2530.2.48.0/2330.2.48.1 to 30.2.49.25430.2.49.255510
2630.2.50.0/2330.2.50.1 to 30.2.51.25430.2.51.255510
2730.2.52.0/2330.2.52.1 to 30.2.53.25430.2.53.255510
2830.2.54.0/2330.2.54.1 to 30.2.55.25430.2.55.255510
2930.2.56.0/2330.2.56.1 to 30.2.57.25430.2.57.255510
3030.2.58.0/2330.2.58.1 to 30.2.59.25430.2.59.255510
3130.2.60.0/2330.2.60.1 to 30.2.61.25430.2.61.255510
3230.2.62.0/2330.2.62.1 to 30.2.63.25430.2.63.255510
3330.2.64.0/2330.2.64.1 to 30.2.65.25430.2.65.255510
3430.2.66.0/2330.2.66.1 to 30.2.67.25430.2.67.255510
3530.2.68.0/2330.2.68.1 to 30.2.69.25430.2.69.255510
3630.2.70.0/2330.2.70.1 to 30.2.71.25430.2.71.255510
3730.2.72.0/2330.2.72.1 to 30.2.73.25430.2.73.255510
3830.2.74.0/2330.2.74.1 to 30.2.75.25430.2.75.255510
3930.2.76.0/2330.2.76.1 to 30.2.77.25430.2.77.255510
4030.2.78.0/2330.2.78.1 to 30.2.79.25430.2.79.255510
4130.2.80.0/2330.2.80.1 to 30.2.81.25430.2.81.255510
4230.2.82.0/2330.2.82.1 to 30.2.83.25430.2.83.255510
4330.2.84.0/2330.2.84.1 to 30.2.85.25430.2.85.255510
4430.2.86.0/2330.2.86.1 to 30.2.87.25430.2.87.255510
4530.2.88.0/2330.2.88.1 to 30.2.89.25430.2.89.255510
4630.2.90.0/2330.2.90.1 to 30.2.91.25430.2.91.255510
4730.2.92.0/2330.2.92.1 to 30.2.93.25430.2.93.255510
4830.2.94.0/2330.2.94.1 to 30.2.95.25430.2.95.255510
4930.2.96.0/2330.2.96.1 to 30.2.97.25430.2.97.255510
5030.2.98.0/2330.2.98.1 to 30.2.99.25430.2.99.255510
5130.2.100.0/2330.2.100.1 to 30.2.101.25430.2.101.255510
5230.2.102.0/2330.2.102.1 to 30.2.103.25430.2.103.255510
5330.2.104.0/2330.2.104.1 to 30.2.105.25430.2.105.255510
5430.2.106.0/2330.2.106.1 to 30.2.107.25430.2.107.255510
5530.2.108.0/2330.2.108.1 to 30.2.109.25430.2.109.255510
5630.2.110.0/2330.2.110.1 to 30.2.111.25430.2.111.255510
5730.2.112.0/2330.2.112.1 to 30.2.113.25430.2.113.255510
5830.2.114.0/2330.2.114.1 to 30.2.115.25430.2.115.255510
5930.2.116.0/2330.2.116.1 to 30.2.117.25430.2.117.255510
6030.2.118.0/2330.2.118.1 to 30.2.119.25430.2.119.255510
6130.2.120.0/2330.2.120.1 to 30.2.121.25430.2.121.255510
6230.2.122.0/2330.2.122.1 to 30.2.123.25430.2.123.255510
6330.2.124.0/2330.2.124.1 to 30.2.125.25430.2.125.255510
6430.2.126.0/2330.2.126.1 to 30.2.127.25430.2.127.255510
6530.2.128.0/2330.2.128.1 to 30.2.129.25430.2.129.255510
6630.2.130.0/2330.2.130.1 to 30.2.131.25430.2.131.255510
6730.2.132.0/2330.2.132.1 to 30.2.133.25430.2.133.255510
6830.2.134.0/2330.2.134.1 to 30.2.135.25430.2.135.255510
6930.2.136.0/2330.2.136.1 to 30.2.137.25430.2.137.255510
7030.2.138.0/2330.2.138.1 to 30.2.139.25430.2.139.255510
7130.2.140.0/2330.2.140.1 to 30.2.141.25430.2.141.255510
7230.2.142.0/2330.2.142.1 to 30.2.143.25430.2.143.255510
7330.2.144.0/2330.2.144.1 to 30.2.145.25430.2.145.255510
7430.2.146.0/2330.2.146.1 to 30.2.147.25430.2.147.255510
7530.2.148.0/2330.2.148.1 to 30.2.149.25430.2.149.255510
7630.2.150.0/2330.2.150.1 to 30.2.151.25430.2.151.255510
7730.2.152.0/2330.2.152.1 to 30.2.153.25430.2.153.255510
7830.2.154.0/2330.2.154.1 to 30.2.155.25430.2.155.255510
7930.2.156.0/2330.2.156.1 to 30.2.157.25430.2.157.255510
8030.2.158.0/2330.2.158.1 to 30.2.159.25430.2.159.255510
8130.2.160.0/2330.2.160.1 to 30.2.161.25430.2.161.255510
8230.2.162.0/2330.2.162.1 to 30.2.163.25430.2.163.255510
8330.2.164.0/2330.2.164.1 to 30.2.165.25430.2.165.255510
8430.2.166.0/2330.2.166.1 to 30.2.167.25430.2.167.255510
8530.2.168.0/2330.2.168.1 to 30.2.169.25430.2.169.255510
8630.2.170.0/2330.2.170.1 to 30.2.171.25430.2.171.255510
8730.2.172.0/2330.2.172.1 to 30.2.173.25430.2.173.255510
8830.2.174.0/2330.2.174.1 to 30.2.175.25430.2.175.255510
8930.2.176.0/2330.2.176.1 to 30.2.177.25430.2.177.255510
9030.2.178.0/2330.2.178.1 to 30.2.179.25430.2.179.255510
9130.2.180.0/2330.2.180.1 to 30.2.181.25430.2.181.255510
9230.2.182.0/2330.2.182.1 to 30.2.183.25430.2.183.255510
9330.2.184.0/2330.2.184.1 to 30.2.185.25430.2.185.255510
9430.2.186.0/2330.2.186.1 to 30.2.187.25430.2.187.255510
9530.2.188.0/2330.2.188.1 to 30.2.189.25430.2.189.255510
9630.2.190.0/2330.2.190.1 to 30.2.191.25430.2.191.255510
9730.2.192.0/2330.2.192.1 to 30.2.193.25430.2.193.255510
9830.2.194.0/2330.2.194.1 to 30.2.195.25430.2.195.255510
9930.2.196.0/2330.2.196.1 to 30.2.197.25430.2.197.255510
10030.2.198.0/2330.2.198.1 to 30.2.199.25430.2.199.255510
10130.2.200.0/2330.2.200.1 to 30.2.201.25430.2.201.255510
10230.2.202.0/2330.2.202.1 to 30.2.203.25430.2.203.255510
10330.2.204.0/2330.2.204.1 to 30.2.205.25430.2.205.255510
10430.2.206.0/2330.2.206.1 to 30.2.207.25430.2.207.255510
10530.2.208.0/2330.2.208.1 to 30.2.209.25430.2.209.255510
10630.2.210.0/2330.2.210.1 to 30.2.211.25430.2.211.255510
10730.2.212.0/2330.2.212.1 to 30.2.213.25430.2.213.255510
10830.2.214.0/2330.2.214.1 to 30.2.215.25430.2.215.255510
10930.2.216.0/2330.2.216.1 to 30.2.217.25430.2.217.255510
11030.2.218.0/2330.2.218.1 to 30.2.219.25430.2.219.255510
11130.2.220.0/2330.2.220.1 to 30.2.221.25430.2.221.255510
11230.2.222.0/2330.2.222.1 to 30.2.223.25430.2.223.255510
11330.2.224.0/2330.2.224.1 to 30.2.225.25430.2.225.255510
11430.2.226.0/2330.2.226.1 to 30.2.227.25430.2.227.255510
11530.2.228.0/2330.2.228.1 to 30.2.229.25430.2.229.255510
11630.2.230.0/2330.2.230.1 to 30.2.231.25430.2.231.255510
11730.2.232.0/2330.2.232.1 to 30.2.233.25430.2.233.255510
11830.2.234.0/2330.2.234.1 to 30.2.235.25430.2.235.255510
11930.2.236.0/2330.2.236.1 to 30.2.237.25430.2.237.255510
12030.2.238.0/2330.2.238.1 to 30.2.239.25430.2.239.255510
12130.2.240.0/2330.2.240.1 to 30.2.241.25430.2.241.255510
12230.2.242.0/2330.2.242.1 to 30.2.243.25430.2.243.255510
12330.2.244.0/2330.2.244.1 to 30.2.245.25430.2.245.255510
12430.2.246.0/2330.2.246.1 to 30.2.247.25430.2.247.255510
12530.2.248.0/2330.2.248.1 to 30.2.249.25430.2.249.255510
12630.2.250.0/2330.2.250.1 to 30.2.251.25430.2.251.255510
12730.2.252.0/2330.2.252.1 to 30.2.253.25430.2.253.255510
12830.2.254.0/2330.2.254.1 to 30.2.255.25430.2.255.255510
12930.3.0.0/2330.3.0.1 to 30.3.1.25430.3.1.255510
13030.3.2.0/2330.3.2.1 to 30.3.3.25430.3.3.255510
13130.3.4.0/2330.3.4.1 to 30.3.5.25430.3.5.255510
13230.3.6.0/2330.3.6.1 to 30.3.7.25430.3.7.255510
13330.3.8.0/2330.3.8.1 to 30.3.9.25430.3.9.255510
13430.3.10.0/2330.3.10.1 to 30.3.11.25430.3.11.255510
13530.3.12.0/2330.3.12.1 to 30.3.13.25430.3.13.255510
13630.3.14.0/2330.3.14.1 to 30.3.15.25430.3.15.255510
13730.3.16.0/2330.3.16.1 to 30.3.17.25430.3.17.255510
13830.3.18.0/2330.3.18.1 to 30.3.19.25430.3.19.255510
13930.3.20.0/2330.3.20.1 to 30.3.21.25430.3.21.255510
14030.3.22.0/2330.3.22.1 to 30.3.23.25430.3.23.255510
14130.3.24.0/2330.3.24.1 to 30.3.25.25430.3.25.255510
14230.3.26.0/2330.3.26.1 to 30.3.27.25430.3.27.255510
14330.3.28.0/2330.3.28.1 to 30.3.29.25430.3.29.255510
14430.3.30.0/2330.3.30.1 to 30.3.31.25430.3.31.255510
14530.3.32.0/2330.3.32.1 to 30.3.33.25430.3.33.255510
14630.3.34.0/2330.3.34.1 to 30.3.35.25430.3.35.255510
14730.3.36.0/2330.3.36.1 to 30.3.37.25430.3.37.255510
14830.3.38.0/2330.3.38.1 to 30.3.39.25430.3.39.255510
14930.3.40.0/2330.3.40.1 to 30.3.41.25430.3.41.255510
15030.3.42.0/2330.3.42.1 to 30.3.43.25430.3.43.255510
15130.3.44.0/2330.3.44.1 to 30.3.45.25430.3.45.255510
15230.3.46.0/2330.3.46.1 to 30.3.47.25430.3.47.255510
15330.3.48.0/2330.3.48.1 to 30.3.49.25430.3.49.255510
15430.3.50.0/2330.3.50.1 to 30.3.51.25430.3.51.255510
15530.3.52.0/2330.3.52.1 to 30.3.53.25430.3.53.255510
15630.3.54.0/2330.3.54.1 to 30.3.55.25430.3.55.255510
15730.3.56.0/2330.3.56.1 to 30.3.57.25430.3.57.255510
15830.3.58.0/2330.3.58.1 to 30.3.59.25430.3.59.255510
15930.3.60.0/2330.3.60.1 to 30.3.61.25430.3.61.255510
16030.3.62.0/2330.3.62.1 to 30.3.63.25430.3.63.255510
16130.3.64.0/2330.3.64.1 to 30.3.65.25430.3.65.255510
16230.3.66.0/2330.3.66.1 to 30.3.67.25430.3.67.255510
16330.3.68.0/2330.3.68.1 to 30.3.69.25430.3.69.255510
16430.3.70.0/2330.3.70.1 to 30.3.71.25430.3.71.255510
16530.3.72.0/2330.3.72.1 to 30.3.73.25430.3.73.255510
16630.3.74.0/2330.3.74.1 to 30.3.75.25430.3.75.255510
16730.3.76.0/2330.3.76.1 to 30.3.77.25430.3.77.255510
16830.3.78.0/2330.3.78.1 to 30.3.79.25430.3.79.255510
16930.3.80.0/2330.3.80.1 to 30.3.81.25430.3.81.255510
17030.3.82.0/2330.3.82.1 to 30.3.83.25430.3.83.255510
17130.3.84.0/2330.3.84.1 to 30.3.85.25430.3.85.255510
17230.3.86.0/2330.3.86.1 to 30.3.87.25430.3.87.255510
17330.3.88.0/2330.3.88.1 to 30.3.89.25430.3.89.255510
17430.3.90.0/2330.3.90.1 to 30.3.91.25430.3.91.255510
17530.3.92.0/2330.3.92.1 to 30.3.93.25430.3.93.255510
17630.3.94.0/2330.3.94.1 to 30.3.95.25430.3.95.255510
17730.3.96.0/2330.3.96.1 to 30.3.97.25430.3.97.255510
17830.3.98.0/2330.3.98.1 to 30.3.99.25430.3.99.255510
17930.3.100.0/2330.3.100.1 to 30.3.101.25430.3.101.255510
18030.3.102.0/2330.3.102.1 to 30.3.103.25430.3.103.255510
18130.3.104.0/2330.3.104.1 to 30.3.105.25430.3.105.255510
18230.3.106.0/2330.3.106.1 to 30.3.107.25430.3.107.255510
18330.3.108.0/2330.3.108.1 to 30.3.109.25430.3.109.255510
18430.3.110.0/2330.3.110.1 to 30.3.111.25430.3.111.255510
18530.3.112.0/2330.3.112.1 to 30.3.113.25430.3.113.255510
18630.3.114.0/2330.3.114.1 to 30.3.115.25430.3.115.255510
18730.3.116.0/2330.3.116.1 to 30.3.117.25430.3.117.255510
18830.3.118.0/2330.3.118.1 to 30.3.119.25430.3.119.255510
18930.3.120.0/2330.3.120.1 to 30.3.121.25430.3.121.255510
19030.3.122.0/2330.3.122.1 to 30.3.123.25430.3.123.255510
19130.3.124.0/2330.3.124.1 to 30.3.125.25430.3.125.255510
19230.3.126.0/2330.3.126.1 to 30.3.127.25430.3.127.255510
19330.3.128.0/2330.3.128.1 to 30.3.129.25430.3.129.255510
19430.3.130.0/2330.3.130.1 to 30.3.131.25430.3.131.255510
19530.3.132.0/2330.3.132.1 to 30.3.133.25430.3.133.255510
19630.3.134.0/2330.3.134.1 to 30.3.135.25430.3.135.255510
19730.3.136.0/2330.3.136.1 to 30.3.137.25430.3.137.255510
19830.3.138.0/2330.3.138.1 to 30.3.139.25430.3.139.255510
19930.3.140.0/2330.3.140.1 to 30.3.141.25430.3.141.255510
20030.3.142.0/2330.3.142.1 to 30.3.143.25430.3.143.255510
20130.3.144.0/2330.3.144.1 to 30.3.145.25430.3.145.255510
20230.3.146.0/2330.3.146.1 to 30.3.147.25430.3.147.255510
20330.3.148.0/2330.3.148.1 to 30.3.149.25430.3.149.255510
20430.3.150.0/2330.3.150.1 to 30.3.151.25430.3.151.255510
20530.3.152.0/2330.3.152.1 to 30.3.153.25430.3.153.255510
20630.3.154.0/2330.3.154.1 to 30.3.155.25430.3.155.255510
20730.3.156.0/2330.3.156.1 to 30.3.157.25430.3.157.255510
20830.3.158.0/2330.3.158.1 to 30.3.159.25430.3.159.255510
20930.3.160.0/2330.3.160.1 to 30.3.161.25430.3.161.255510
21030.3.162.0/2330.3.162.1 to 30.3.163.25430.3.163.255510
21130.3.164.0/2330.3.164.1 to 30.3.165.25430.3.165.255510
21230.3.166.0/2330.3.166.1 to 30.3.167.25430.3.167.255510
21330.3.168.0/2330.3.168.1 to 30.3.169.25430.3.169.255510
21430.3.170.0/2330.3.170.1 to 30.3.171.25430.3.171.255510
21530.3.172.0/2330.3.172.1 to 30.3.173.25430.3.173.255510
21630.3.174.0/2330.3.174.1 to 30.3.175.25430.3.175.255510
21730.3.176.0/2330.3.176.1 to 30.3.177.25430.3.177.255510
21830.3.178.0/2330.3.178.1 to 30.3.179.25430.3.179.255510
21930.3.180.0/2330.3.180.1 to 30.3.181.25430.3.181.255510
22030.3.182.0/2330.3.182.1 to 30.3.183.25430.3.183.255510
22130.3.184.0/2330.3.184.1 to 30.3.185.25430.3.185.255510
22230.3.186.0/2330.3.186.1 to 30.3.187.25430.3.187.255510
22330.3.188.0/2330.3.188.1 to 30.3.189.25430.3.189.255510
22430.3.190.0/2330.3.190.1 to 30.3.191.25430.3.191.255510
22530.3.192.0/2330.3.192.1 to 30.3.193.25430.3.193.255510
22630.3.194.0/2330.3.194.1 to 30.3.195.25430.3.195.255510
22730.3.196.0/2330.3.196.1 to 30.3.197.25430.3.197.255510
22830.3.198.0/2330.3.198.1 to 30.3.199.25430.3.199.255510
22930.3.200.0/2330.3.200.1 to 30.3.201.25430.3.201.255510
23030.3.202.0/2330.3.202.1 to 30.3.203.25430.3.203.255510
23130.3.204.0/2330.3.204.1 to 30.3.205.25430.3.205.255510
23230.3.206.0/2330.3.206.1 to 30.3.207.25430.3.207.255510
23330.3.208.0/2330.3.208.1 to 30.3.209.25430.3.209.255510
23430.3.210.0/2330.3.210.1 to 30.3.211.25430.3.211.255510
23530.3.212.0/2330.3.212.1 to 30.3.213.25430.3.213.255510
23630.3.214.0/2330.3.214.1 to 30.3.215.25430.3.215.255510
23730.3.216.0/2330.3.216.1 to 30.3.217.25430.3.217.255510
23830.3.218.0/2330.3.218.1 to 30.3.219.25430.3.219.255510
23930.3.220.0/2330.3.220.1 to 30.3.221.25430.3.221.255510
24030.3.222.0/2330.3.222.1 to 30.3.223.25430.3.223.255510
24130.3.224.0/2330.3.224.1 to 30.3.225.25430.3.225.255510
24230.3.226.0/2330.3.226.1 to 30.3.227.25430.3.227.255510
24330.3.228.0/2330.3.228.1 to 30.3.229.25430.3.229.255510
24430.3.230.0/2330.3.230.1 to 30.3.231.25430.3.231.255510
24530.3.232.0/2330.3.232.1 to 30.3.233.25430.3.233.255510
24630.3.234.0/2330.3.234.1 to 30.3.235.25430.3.235.255510
24730.3.236.0/2330.3.236.1 to 30.3.237.25430.3.237.255510
24830.3.238.0/2330.3.238.1 to 30.3.239.25430.3.239.255510
24930.3.240.0/2330.3.240.1 to 30.3.241.25430.3.241.255510
25030.3.242.0/2330.3.242.1 to 30.3.243.25430.3.243.255510
25130.3.244.0/2330.3.244.1 to 30.3.245.25430.3.245.255510
25230.3.246.0/2330.3.246.1 to 30.3.247.25430.3.247.255510
25330.3.248.0/2330.3.248.1 to 30.3.249.25430.3.249.255510
25430.3.250.0/2330.3.250.1 to 30.3.251.25430.3.251.255510
25530.3.252.0/2330.3.252.1 to 30.3.253.25430.3.253.255510
25630.3.254.0/2330.3.254.1 to 30.3.255.25430.3.255.255510

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.