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.

Network19.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
19.0.0.0
Broadcast address
19.127.255.255
First usable
19.0.0.1
Last usable
19.127.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Public public
Old class
A (default /8)
As numbers
Hex 13000000 · Integer 318767104 to 327155711
Reverse DNS zones
0.19.in-addr.arpa
1.19.in-addr.arpa
2.19.in-addr.arpa
3.19.in-addr.arpa
4.19.in-addr.arpa
5.19.in-addr.arpa
6.19.in-addr.arpa
7.19.in-addr.arpa
8.19.in-addr.arpa
9.19.in-addr.arpa
10.19.in-addr.arpa
11.19.in-addr.arpa
12.19.in-addr.arpa
13.19.in-addr.arpa
14.19.in-addr.arpa
15.19.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00010011.00000000.00000000.0000000019.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network00010011.00000000.00000000.0000000019.0.0.0
Broadcast00010011.01111111.11111111.1111111119.127.255.255
Split into smaller subnets/17
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

19.0.0.0/9 makes 256 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
119.0.0.0/1719.0.0.1 to 19.0.127.25419.0.127.25532,766
219.0.128.0/1719.0.128.1 to 19.0.255.25419.0.255.25532,766
319.1.0.0/1719.1.0.1 to 19.1.127.25419.1.127.25532,766
419.1.128.0/1719.1.128.1 to 19.1.255.25419.1.255.25532,766
519.2.0.0/1719.2.0.1 to 19.2.127.25419.2.127.25532,766
619.2.128.0/1719.2.128.1 to 19.2.255.25419.2.255.25532,766
719.3.0.0/1719.3.0.1 to 19.3.127.25419.3.127.25532,766
819.3.128.0/1719.3.128.1 to 19.3.255.25419.3.255.25532,766
919.4.0.0/1719.4.0.1 to 19.4.127.25419.4.127.25532,766
1019.4.128.0/1719.4.128.1 to 19.4.255.25419.4.255.25532,766
1119.5.0.0/1719.5.0.1 to 19.5.127.25419.5.127.25532,766
1219.5.128.0/1719.5.128.1 to 19.5.255.25419.5.255.25532,766
1319.6.0.0/1719.6.0.1 to 19.6.127.25419.6.127.25532,766
1419.6.128.0/1719.6.128.1 to 19.6.255.25419.6.255.25532,766
1519.7.0.0/1719.7.0.1 to 19.7.127.25419.7.127.25532,766
1619.7.128.0/1719.7.128.1 to 19.7.255.25419.7.255.25532,766
1719.8.0.0/1719.8.0.1 to 19.8.127.25419.8.127.25532,766
1819.8.128.0/1719.8.128.1 to 19.8.255.25419.8.255.25532,766
1919.9.0.0/1719.9.0.1 to 19.9.127.25419.9.127.25532,766
2019.9.128.0/1719.9.128.1 to 19.9.255.25419.9.255.25532,766
2119.10.0.0/1719.10.0.1 to 19.10.127.25419.10.127.25532,766
2219.10.128.0/1719.10.128.1 to 19.10.255.25419.10.255.25532,766
2319.11.0.0/1719.11.0.1 to 19.11.127.25419.11.127.25532,766
2419.11.128.0/1719.11.128.1 to 19.11.255.25419.11.255.25532,766
2519.12.0.0/1719.12.0.1 to 19.12.127.25419.12.127.25532,766
2619.12.128.0/1719.12.128.1 to 19.12.255.25419.12.255.25532,766
2719.13.0.0/1719.13.0.1 to 19.13.127.25419.13.127.25532,766
2819.13.128.0/1719.13.128.1 to 19.13.255.25419.13.255.25532,766
2919.14.0.0/1719.14.0.1 to 19.14.127.25419.14.127.25532,766
3019.14.128.0/1719.14.128.1 to 19.14.255.25419.14.255.25532,766
3119.15.0.0/1719.15.0.1 to 19.15.127.25419.15.127.25532,766
3219.15.128.0/1719.15.128.1 to 19.15.255.25419.15.255.25532,766
3319.16.0.0/1719.16.0.1 to 19.16.127.25419.16.127.25532,766
3419.16.128.0/1719.16.128.1 to 19.16.255.25419.16.255.25532,766
3519.17.0.0/1719.17.0.1 to 19.17.127.25419.17.127.25532,766
3619.17.128.0/1719.17.128.1 to 19.17.255.25419.17.255.25532,766
3719.18.0.0/1719.18.0.1 to 19.18.127.25419.18.127.25532,766
3819.18.128.0/1719.18.128.1 to 19.18.255.25419.18.255.25532,766
3919.19.0.0/1719.19.0.1 to 19.19.127.25419.19.127.25532,766
4019.19.128.0/1719.19.128.1 to 19.19.255.25419.19.255.25532,766
4119.20.0.0/1719.20.0.1 to 19.20.127.25419.20.127.25532,766
4219.20.128.0/1719.20.128.1 to 19.20.255.25419.20.255.25532,766
4319.21.0.0/1719.21.0.1 to 19.21.127.25419.21.127.25532,766
4419.21.128.0/1719.21.128.1 to 19.21.255.25419.21.255.25532,766
4519.22.0.0/1719.22.0.1 to 19.22.127.25419.22.127.25532,766
4619.22.128.0/1719.22.128.1 to 19.22.255.25419.22.255.25532,766
4719.23.0.0/1719.23.0.1 to 19.23.127.25419.23.127.25532,766
4819.23.128.0/1719.23.128.1 to 19.23.255.25419.23.255.25532,766
4919.24.0.0/1719.24.0.1 to 19.24.127.25419.24.127.25532,766
5019.24.128.0/1719.24.128.1 to 19.24.255.25419.24.255.25532,766
5119.25.0.0/1719.25.0.1 to 19.25.127.25419.25.127.25532,766
5219.25.128.0/1719.25.128.1 to 19.25.255.25419.25.255.25532,766
5319.26.0.0/1719.26.0.1 to 19.26.127.25419.26.127.25532,766
5419.26.128.0/1719.26.128.1 to 19.26.255.25419.26.255.25532,766
5519.27.0.0/1719.27.0.1 to 19.27.127.25419.27.127.25532,766
5619.27.128.0/1719.27.128.1 to 19.27.255.25419.27.255.25532,766
5719.28.0.0/1719.28.0.1 to 19.28.127.25419.28.127.25532,766
5819.28.128.0/1719.28.128.1 to 19.28.255.25419.28.255.25532,766
5919.29.0.0/1719.29.0.1 to 19.29.127.25419.29.127.25532,766
6019.29.128.0/1719.29.128.1 to 19.29.255.25419.29.255.25532,766
6119.30.0.0/1719.30.0.1 to 19.30.127.25419.30.127.25532,766
6219.30.128.0/1719.30.128.1 to 19.30.255.25419.30.255.25532,766
6319.31.0.0/1719.31.0.1 to 19.31.127.25419.31.127.25532,766
6419.31.128.0/1719.31.128.1 to 19.31.255.25419.31.255.25532,766
6519.32.0.0/1719.32.0.1 to 19.32.127.25419.32.127.25532,766
6619.32.128.0/1719.32.128.1 to 19.32.255.25419.32.255.25532,766
6719.33.0.0/1719.33.0.1 to 19.33.127.25419.33.127.25532,766
6819.33.128.0/1719.33.128.1 to 19.33.255.25419.33.255.25532,766
6919.34.0.0/1719.34.0.1 to 19.34.127.25419.34.127.25532,766
7019.34.128.0/1719.34.128.1 to 19.34.255.25419.34.255.25532,766
7119.35.0.0/1719.35.0.1 to 19.35.127.25419.35.127.25532,766
7219.35.128.0/1719.35.128.1 to 19.35.255.25419.35.255.25532,766
7319.36.0.0/1719.36.0.1 to 19.36.127.25419.36.127.25532,766
7419.36.128.0/1719.36.128.1 to 19.36.255.25419.36.255.25532,766
7519.37.0.0/1719.37.0.1 to 19.37.127.25419.37.127.25532,766
7619.37.128.0/1719.37.128.1 to 19.37.255.25419.37.255.25532,766
7719.38.0.0/1719.38.0.1 to 19.38.127.25419.38.127.25532,766
7819.38.128.0/1719.38.128.1 to 19.38.255.25419.38.255.25532,766
7919.39.0.0/1719.39.0.1 to 19.39.127.25419.39.127.25532,766
8019.39.128.0/1719.39.128.1 to 19.39.255.25419.39.255.25532,766
8119.40.0.0/1719.40.0.1 to 19.40.127.25419.40.127.25532,766
8219.40.128.0/1719.40.128.1 to 19.40.255.25419.40.255.25532,766
8319.41.0.0/1719.41.0.1 to 19.41.127.25419.41.127.25532,766
8419.41.128.0/1719.41.128.1 to 19.41.255.25419.41.255.25532,766
8519.42.0.0/1719.42.0.1 to 19.42.127.25419.42.127.25532,766
8619.42.128.0/1719.42.128.1 to 19.42.255.25419.42.255.25532,766
8719.43.0.0/1719.43.0.1 to 19.43.127.25419.43.127.25532,766
8819.43.128.0/1719.43.128.1 to 19.43.255.25419.43.255.25532,766
8919.44.0.0/1719.44.0.1 to 19.44.127.25419.44.127.25532,766
9019.44.128.0/1719.44.128.1 to 19.44.255.25419.44.255.25532,766
9119.45.0.0/1719.45.0.1 to 19.45.127.25419.45.127.25532,766
9219.45.128.0/1719.45.128.1 to 19.45.255.25419.45.255.25532,766
9319.46.0.0/1719.46.0.1 to 19.46.127.25419.46.127.25532,766
9419.46.128.0/1719.46.128.1 to 19.46.255.25419.46.255.25532,766
9519.47.0.0/1719.47.0.1 to 19.47.127.25419.47.127.25532,766
9619.47.128.0/1719.47.128.1 to 19.47.255.25419.47.255.25532,766
9719.48.0.0/1719.48.0.1 to 19.48.127.25419.48.127.25532,766
9819.48.128.0/1719.48.128.1 to 19.48.255.25419.48.255.25532,766
9919.49.0.0/1719.49.0.1 to 19.49.127.25419.49.127.25532,766
10019.49.128.0/1719.49.128.1 to 19.49.255.25419.49.255.25532,766
10119.50.0.0/1719.50.0.1 to 19.50.127.25419.50.127.25532,766
10219.50.128.0/1719.50.128.1 to 19.50.255.25419.50.255.25532,766
10319.51.0.0/1719.51.0.1 to 19.51.127.25419.51.127.25532,766
10419.51.128.0/1719.51.128.1 to 19.51.255.25419.51.255.25532,766
10519.52.0.0/1719.52.0.1 to 19.52.127.25419.52.127.25532,766
10619.52.128.0/1719.52.128.1 to 19.52.255.25419.52.255.25532,766
10719.53.0.0/1719.53.0.1 to 19.53.127.25419.53.127.25532,766
10819.53.128.0/1719.53.128.1 to 19.53.255.25419.53.255.25532,766
10919.54.0.0/1719.54.0.1 to 19.54.127.25419.54.127.25532,766
11019.54.128.0/1719.54.128.1 to 19.54.255.25419.54.255.25532,766
11119.55.0.0/1719.55.0.1 to 19.55.127.25419.55.127.25532,766
11219.55.128.0/1719.55.128.1 to 19.55.255.25419.55.255.25532,766
11319.56.0.0/1719.56.0.1 to 19.56.127.25419.56.127.25532,766
11419.56.128.0/1719.56.128.1 to 19.56.255.25419.56.255.25532,766
11519.57.0.0/1719.57.0.1 to 19.57.127.25419.57.127.25532,766
11619.57.128.0/1719.57.128.1 to 19.57.255.25419.57.255.25532,766
11719.58.0.0/1719.58.0.1 to 19.58.127.25419.58.127.25532,766
11819.58.128.0/1719.58.128.1 to 19.58.255.25419.58.255.25532,766
11919.59.0.0/1719.59.0.1 to 19.59.127.25419.59.127.25532,766
12019.59.128.0/1719.59.128.1 to 19.59.255.25419.59.255.25532,766
12119.60.0.0/1719.60.0.1 to 19.60.127.25419.60.127.25532,766
12219.60.128.0/1719.60.128.1 to 19.60.255.25419.60.255.25532,766
12319.61.0.0/1719.61.0.1 to 19.61.127.25419.61.127.25532,766
12419.61.128.0/1719.61.128.1 to 19.61.255.25419.61.255.25532,766
12519.62.0.0/1719.62.0.1 to 19.62.127.25419.62.127.25532,766
12619.62.128.0/1719.62.128.1 to 19.62.255.25419.62.255.25532,766
12719.63.0.0/1719.63.0.1 to 19.63.127.25419.63.127.25532,766
12819.63.128.0/1719.63.128.1 to 19.63.255.25419.63.255.25532,766
12919.64.0.0/1719.64.0.1 to 19.64.127.25419.64.127.25532,766
13019.64.128.0/1719.64.128.1 to 19.64.255.25419.64.255.25532,766
13119.65.0.0/1719.65.0.1 to 19.65.127.25419.65.127.25532,766
13219.65.128.0/1719.65.128.1 to 19.65.255.25419.65.255.25532,766
13319.66.0.0/1719.66.0.1 to 19.66.127.25419.66.127.25532,766
13419.66.128.0/1719.66.128.1 to 19.66.255.25419.66.255.25532,766
13519.67.0.0/1719.67.0.1 to 19.67.127.25419.67.127.25532,766
13619.67.128.0/1719.67.128.1 to 19.67.255.25419.67.255.25532,766
13719.68.0.0/1719.68.0.1 to 19.68.127.25419.68.127.25532,766
13819.68.128.0/1719.68.128.1 to 19.68.255.25419.68.255.25532,766
13919.69.0.0/1719.69.0.1 to 19.69.127.25419.69.127.25532,766
14019.69.128.0/1719.69.128.1 to 19.69.255.25419.69.255.25532,766
14119.70.0.0/1719.70.0.1 to 19.70.127.25419.70.127.25532,766
14219.70.128.0/1719.70.128.1 to 19.70.255.25419.70.255.25532,766
14319.71.0.0/1719.71.0.1 to 19.71.127.25419.71.127.25532,766
14419.71.128.0/1719.71.128.1 to 19.71.255.25419.71.255.25532,766
14519.72.0.0/1719.72.0.1 to 19.72.127.25419.72.127.25532,766
14619.72.128.0/1719.72.128.1 to 19.72.255.25419.72.255.25532,766
14719.73.0.0/1719.73.0.1 to 19.73.127.25419.73.127.25532,766
14819.73.128.0/1719.73.128.1 to 19.73.255.25419.73.255.25532,766
14919.74.0.0/1719.74.0.1 to 19.74.127.25419.74.127.25532,766
15019.74.128.0/1719.74.128.1 to 19.74.255.25419.74.255.25532,766
15119.75.0.0/1719.75.0.1 to 19.75.127.25419.75.127.25532,766
15219.75.128.0/1719.75.128.1 to 19.75.255.25419.75.255.25532,766
15319.76.0.0/1719.76.0.1 to 19.76.127.25419.76.127.25532,766
15419.76.128.0/1719.76.128.1 to 19.76.255.25419.76.255.25532,766
15519.77.0.0/1719.77.0.1 to 19.77.127.25419.77.127.25532,766
15619.77.128.0/1719.77.128.1 to 19.77.255.25419.77.255.25532,766
15719.78.0.0/1719.78.0.1 to 19.78.127.25419.78.127.25532,766
15819.78.128.0/1719.78.128.1 to 19.78.255.25419.78.255.25532,766
15919.79.0.0/1719.79.0.1 to 19.79.127.25419.79.127.25532,766
16019.79.128.0/1719.79.128.1 to 19.79.255.25419.79.255.25532,766
16119.80.0.0/1719.80.0.1 to 19.80.127.25419.80.127.25532,766
16219.80.128.0/1719.80.128.1 to 19.80.255.25419.80.255.25532,766
16319.81.0.0/1719.81.0.1 to 19.81.127.25419.81.127.25532,766
16419.81.128.0/1719.81.128.1 to 19.81.255.25419.81.255.25532,766
16519.82.0.0/1719.82.0.1 to 19.82.127.25419.82.127.25532,766
16619.82.128.0/1719.82.128.1 to 19.82.255.25419.82.255.25532,766
16719.83.0.0/1719.83.0.1 to 19.83.127.25419.83.127.25532,766
16819.83.128.0/1719.83.128.1 to 19.83.255.25419.83.255.25532,766
16919.84.0.0/1719.84.0.1 to 19.84.127.25419.84.127.25532,766
17019.84.128.0/1719.84.128.1 to 19.84.255.25419.84.255.25532,766
17119.85.0.0/1719.85.0.1 to 19.85.127.25419.85.127.25532,766
17219.85.128.0/1719.85.128.1 to 19.85.255.25419.85.255.25532,766
17319.86.0.0/1719.86.0.1 to 19.86.127.25419.86.127.25532,766
17419.86.128.0/1719.86.128.1 to 19.86.255.25419.86.255.25532,766
17519.87.0.0/1719.87.0.1 to 19.87.127.25419.87.127.25532,766
17619.87.128.0/1719.87.128.1 to 19.87.255.25419.87.255.25532,766
17719.88.0.0/1719.88.0.1 to 19.88.127.25419.88.127.25532,766
17819.88.128.0/1719.88.128.1 to 19.88.255.25419.88.255.25532,766
17919.89.0.0/1719.89.0.1 to 19.89.127.25419.89.127.25532,766
18019.89.128.0/1719.89.128.1 to 19.89.255.25419.89.255.25532,766
18119.90.0.0/1719.90.0.1 to 19.90.127.25419.90.127.25532,766
18219.90.128.0/1719.90.128.1 to 19.90.255.25419.90.255.25532,766
18319.91.0.0/1719.91.0.1 to 19.91.127.25419.91.127.25532,766
18419.91.128.0/1719.91.128.1 to 19.91.255.25419.91.255.25532,766
18519.92.0.0/1719.92.0.1 to 19.92.127.25419.92.127.25532,766
18619.92.128.0/1719.92.128.1 to 19.92.255.25419.92.255.25532,766
18719.93.0.0/1719.93.0.1 to 19.93.127.25419.93.127.25532,766
18819.93.128.0/1719.93.128.1 to 19.93.255.25419.93.255.25532,766
18919.94.0.0/1719.94.0.1 to 19.94.127.25419.94.127.25532,766
19019.94.128.0/1719.94.128.1 to 19.94.255.25419.94.255.25532,766
19119.95.0.0/1719.95.0.1 to 19.95.127.25419.95.127.25532,766
19219.95.128.0/1719.95.128.1 to 19.95.255.25419.95.255.25532,766
19319.96.0.0/1719.96.0.1 to 19.96.127.25419.96.127.25532,766
19419.96.128.0/1719.96.128.1 to 19.96.255.25419.96.255.25532,766
19519.97.0.0/1719.97.0.1 to 19.97.127.25419.97.127.25532,766
19619.97.128.0/1719.97.128.1 to 19.97.255.25419.97.255.25532,766
19719.98.0.0/1719.98.0.1 to 19.98.127.25419.98.127.25532,766
19819.98.128.0/1719.98.128.1 to 19.98.255.25419.98.255.25532,766
19919.99.0.0/1719.99.0.1 to 19.99.127.25419.99.127.25532,766
20019.99.128.0/1719.99.128.1 to 19.99.255.25419.99.255.25532,766
20119.100.0.0/1719.100.0.1 to 19.100.127.25419.100.127.25532,766
20219.100.128.0/1719.100.128.1 to 19.100.255.25419.100.255.25532,766
20319.101.0.0/1719.101.0.1 to 19.101.127.25419.101.127.25532,766
20419.101.128.0/1719.101.128.1 to 19.101.255.25419.101.255.25532,766
20519.102.0.0/1719.102.0.1 to 19.102.127.25419.102.127.25532,766
20619.102.128.0/1719.102.128.1 to 19.102.255.25419.102.255.25532,766
20719.103.0.0/1719.103.0.1 to 19.103.127.25419.103.127.25532,766
20819.103.128.0/1719.103.128.1 to 19.103.255.25419.103.255.25532,766
20919.104.0.0/1719.104.0.1 to 19.104.127.25419.104.127.25532,766
21019.104.128.0/1719.104.128.1 to 19.104.255.25419.104.255.25532,766
21119.105.0.0/1719.105.0.1 to 19.105.127.25419.105.127.25532,766
21219.105.128.0/1719.105.128.1 to 19.105.255.25419.105.255.25532,766
21319.106.0.0/1719.106.0.1 to 19.106.127.25419.106.127.25532,766
21419.106.128.0/1719.106.128.1 to 19.106.255.25419.106.255.25532,766
21519.107.0.0/1719.107.0.1 to 19.107.127.25419.107.127.25532,766
21619.107.128.0/1719.107.128.1 to 19.107.255.25419.107.255.25532,766
21719.108.0.0/1719.108.0.1 to 19.108.127.25419.108.127.25532,766
21819.108.128.0/1719.108.128.1 to 19.108.255.25419.108.255.25532,766
21919.109.0.0/1719.109.0.1 to 19.109.127.25419.109.127.25532,766
22019.109.128.0/1719.109.128.1 to 19.109.255.25419.109.255.25532,766
22119.110.0.0/1719.110.0.1 to 19.110.127.25419.110.127.25532,766
22219.110.128.0/1719.110.128.1 to 19.110.255.25419.110.255.25532,766
22319.111.0.0/1719.111.0.1 to 19.111.127.25419.111.127.25532,766
22419.111.128.0/1719.111.128.1 to 19.111.255.25419.111.255.25532,766
22519.112.0.0/1719.112.0.1 to 19.112.127.25419.112.127.25532,766
22619.112.128.0/1719.112.128.1 to 19.112.255.25419.112.255.25532,766
22719.113.0.0/1719.113.0.1 to 19.113.127.25419.113.127.25532,766
22819.113.128.0/1719.113.128.1 to 19.113.255.25419.113.255.25532,766
22919.114.0.0/1719.114.0.1 to 19.114.127.25419.114.127.25532,766
23019.114.128.0/1719.114.128.1 to 19.114.255.25419.114.255.25532,766
23119.115.0.0/1719.115.0.1 to 19.115.127.25419.115.127.25532,766
23219.115.128.0/1719.115.128.1 to 19.115.255.25419.115.255.25532,766
23319.116.0.0/1719.116.0.1 to 19.116.127.25419.116.127.25532,766
23419.116.128.0/1719.116.128.1 to 19.116.255.25419.116.255.25532,766
23519.117.0.0/1719.117.0.1 to 19.117.127.25419.117.127.25532,766
23619.117.128.0/1719.117.128.1 to 19.117.255.25419.117.255.25532,766
23719.118.0.0/1719.118.0.1 to 19.118.127.25419.118.127.25532,766
23819.118.128.0/1719.118.128.1 to 19.118.255.25419.118.255.25532,766
23919.119.0.0/1719.119.0.1 to 19.119.127.25419.119.127.25532,766
24019.119.128.0/1719.119.128.1 to 19.119.255.25419.119.255.25532,766
24119.120.0.0/1719.120.0.1 to 19.120.127.25419.120.127.25532,766
24219.120.128.0/1719.120.128.1 to 19.120.255.25419.120.255.25532,766
24319.121.0.0/1719.121.0.1 to 19.121.127.25419.121.127.25532,766
24419.121.128.0/1719.121.128.1 to 19.121.255.25419.121.255.25532,766
24519.122.0.0/1719.122.0.1 to 19.122.127.25419.122.127.25532,766
24619.122.128.0/1719.122.128.1 to 19.122.255.25419.122.255.25532,766
24719.123.0.0/1719.123.0.1 to 19.123.127.25419.123.127.25532,766
24819.123.128.0/1719.123.128.1 to 19.123.255.25419.123.255.25532,766
24919.124.0.0/1719.124.0.1 to 19.124.127.25419.124.127.25532,766
25019.124.128.0/1719.124.128.1 to 19.124.255.25419.124.255.25532,766
25119.125.0.0/1719.125.0.1 to 19.125.127.25419.125.127.25532,766
25219.125.128.0/1719.125.128.1 to 19.125.255.25419.125.255.25532,766
25319.126.0.0/1719.126.0.1 to 19.126.127.25419.126.127.25532,766
25419.126.128.0/1719.126.128.1 to 19.126.255.25419.126.255.25532,766
25519.127.0.0/1719.127.0.1 to 19.127.127.25419.127.127.25532,766
25619.127.128.0/1719.127.128.1 to 19.127.255.25419.127.255.25532,766

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.