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.

Network61.0.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
61.0.0.0
Broadcast address
61.63.255.255
First usable
61.0.0.1
Last usable
61.63.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Public public
Old class
A (default /8)
As numbers
Hex 3D000000 · Integer 1023410176 to 1027604479
Reverse DNS zones
0.61.in-addr.arpa
1.61.in-addr.arpa
2.61.in-addr.arpa
3.61.in-addr.arpa
4.61.in-addr.arpa
5.61.in-addr.arpa
6.61.in-addr.arpa
7.61.in-addr.arpa
8.61.in-addr.arpa
9.61.in-addr.arpa
10.61.in-addr.arpa
11.61.in-addr.arpa
12.61.in-addr.arpa
13.61.in-addr.arpa
14.61.in-addr.arpa
15.61.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00111101.00000000.00000000.0000000061.0.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network00111101.00000000.00000000.0000000061.0.0.0
Broadcast00111101.00111111.11111111.1111111161.63.255.255
Split into smaller subnets/20
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

61.0.0.0/10 makes 1,024 subnets of /20; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
161.0.0.0/2061.0.0.1 to 61.0.15.25461.0.15.2554,094
261.0.16.0/2061.0.16.1 to 61.0.31.25461.0.31.2554,094
361.0.32.0/2061.0.32.1 to 61.0.47.25461.0.47.2554,094
461.0.48.0/2061.0.48.1 to 61.0.63.25461.0.63.2554,094
561.0.64.0/2061.0.64.1 to 61.0.79.25461.0.79.2554,094
661.0.80.0/2061.0.80.1 to 61.0.95.25461.0.95.2554,094
761.0.96.0/2061.0.96.1 to 61.0.111.25461.0.111.2554,094
861.0.112.0/2061.0.112.1 to 61.0.127.25461.0.127.2554,094
961.0.128.0/2061.0.128.1 to 61.0.143.25461.0.143.2554,094
1061.0.144.0/2061.0.144.1 to 61.0.159.25461.0.159.2554,094
1161.0.160.0/2061.0.160.1 to 61.0.175.25461.0.175.2554,094
1261.0.176.0/2061.0.176.1 to 61.0.191.25461.0.191.2554,094
1361.0.192.0/2061.0.192.1 to 61.0.207.25461.0.207.2554,094
1461.0.208.0/2061.0.208.1 to 61.0.223.25461.0.223.2554,094
1561.0.224.0/2061.0.224.1 to 61.0.239.25461.0.239.2554,094
1661.0.240.0/2061.0.240.1 to 61.0.255.25461.0.255.2554,094
1761.1.0.0/2061.1.0.1 to 61.1.15.25461.1.15.2554,094
1861.1.16.0/2061.1.16.1 to 61.1.31.25461.1.31.2554,094
1961.1.32.0/2061.1.32.1 to 61.1.47.25461.1.47.2554,094
2061.1.48.0/2061.1.48.1 to 61.1.63.25461.1.63.2554,094
2161.1.64.0/2061.1.64.1 to 61.1.79.25461.1.79.2554,094
2261.1.80.0/2061.1.80.1 to 61.1.95.25461.1.95.2554,094
2361.1.96.0/2061.1.96.1 to 61.1.111.25461.1.111.2554,094
2461.1.112.0/2061.1.112.1 to 61.1.127.25461.1.127.2554,094
2561.1.128.0/2061.1.128.1 to 61.1.143.25461.1.143.2554,094
2661.1.144.0/2061.1.144.1 to 61.1.159.25461.1.159.2554,094
2761.1.160.0/2061.1.160.1 to 61.1.175.25461.1.175.2554,094
2861.1.176.0/2061.1.176.1 to 61.1.191.25461.1.191.2554,094
2961.1.192.0/2061.1.192.1 to 61.1.207.25461.1.207.2554,094
3061.1.208.0/2061.1.208.1 to 61.1.223.25461.1.223.2554,094
3161.1.224.0/2061.1.224.1 to 61.1.239.25461.1.239.2554,094
3261.1.240.0/2061.1.240.1 to 61.1.255.25461.1.255.2554,094
3361.2.0.0/2061.2.0.1 to 61.2.15.25461.2.15.2554,094
3461.2.16.0/2061.2.16.1 to 61.2.31.25461.2.31.2554,094
3561.2.32.0/2061.2.32.1 to 61.2.47.25461.2.47.2554,094
3661.2.48.0/2061.2.48.1 to 61.2.63.25461.2.63.2554,094
3761.2.64.0/2061.2.64.1 to 61.2.79.25461.2.79.2554,094
3861.2.80.0/2061.2.80.1 to 61.2.95.25461.2.95.2554,094
3961.2.96.0/2061.2.96.1 to 61.2.111.25461.2.111.2554,094
4061.2.112.0/2061.2.112.1 to 61.2.127.25461.2.127.2554,094
4161.2.128.0/2061.2.128.1 to 61.2.143.25461.2.143.2554,094
4261.2.144.0/2061.2.144.1 to 61.2.159.25461.2.159.2554,094
4361.2.160.0/2061.2.160.1 to 61.2.175.25461.2.175.2554,094
4461.2.176.0/2061.2.176.1 to 61.2.191.25461.2.191.2554,094
4561.2.192.0/2061.2.192.1 to 61.2.207.25461.2.207.2554,094
4661.2.208.0/2061.2.208.1 to 61.2.223.25461.2.223.2554,094
4761.2.224.0/2061.2.224.1 to 61.2.239.25461.2.239.2554,094
4861.2.240.0/2061.2.240.1 to 61.2.255.25461.2.255.2554,094
4961.3.0.0/2061.3.0.1 to 61.3.15.25461.3.15.2554,094
5061.3.16.0/2061.3.16.1 to 61.3.31.25461.3.31.2554,094
5161.3.32.0/2061.3.32.1 to 61.3.47.25461.3.47.2554,094
5261.3.48.0/2061.3.48.1 to 61.3.63.25461.3.63.2554,094
5361.3.64.0/2061.3.64.1 to 61.3.79.25461.3.79.2554,094
5461.3.80.0/2061.3.80.1 to 61.3.95.25461.3.95.2554,094
5561.3.96.0/2061.3.96.1 to 61.3.111.25461.3.111.2554,094
5661.3.112.0/2061.3.112.1 to 61.3.127.25461.3.127.2554,094
5761.3.128.0/2061.3.128.1 to 61.3.143.25461.3.143.2554,094
5861.3.144.0/2061.3.144.1 to 61.3.159.25461.3.159.2554,094
5961.3.160.0/2061.3.160.1 to 61.3.175.25461.3.175.2554,094
6061.3.176.0/2061.3.176.1 to 61.3.191.25461.3.191.2554,094
6161.3.192.0/2061.3.192.1 to 61.3.207.25461.3.207.2554,094
6261.3.208.0/2061.3.208.1 to 61.3.223.25461.3.223.2554,094
6361.3.224.0/2061.3.224.1 to 61.3.239.25461.3.239.2554,094
6461.3.240.0/2061.3.240.1 to 61.3.255.25461.3.255.2554,094
6561.4.0.0/2061.4.0.1 to 61.4.15.25461.4.15.2554,094
6661.4.16.0/2061.4.16.1 to 61.4.31.25461.4.31.2554,094
6761.4.32.0/2061.4.32.1 to 61.4.47.25461.4.47.2554,094
6861.4.48.0/2061.4.48.1 to 61.4.63.25461.4.63.2554,094
6961.4.64.0/2061.4.64.1 to 61.4.79.25461.4.79.2554,094
7061.4.80.0/2061.4.80.1 to 61.4.95.25461.4.95.2554,094
7161.4.96.0/2061.4.96.1 to 61.4.111.25461.4.111.2554,094
7261.4.112.0/2061.4.112.1 to 61.4.127.25461.4.127.2554,094
7361.4.128.0/2061.4.128.1 to 61.4.143.25461.4.143.2554,094
7461.4.144.0/2061.4.144.1 to 61.4.159.25461.4.159.2554,094
7561.4.160.0/2061.4.160.1 to 61.4.175.25461.4.175.2554,094
7661.4.176.0/2061.4.176.1 to 61.4.191.25461.4.191.2554,094
7761.4.192.0/2061.4.192.1 to 61.4.207.25461.4.207.2554,094
7861.4.208.0/2061.4.208.1 to 61.4.223.25461.4.223.2554,094
7961.4.224.0/2061.4.224.1 to 61.4.239.25461.4.239.2554,094
8061.4.240.0/2061.4.240.1 to 61.4.255.25461.4.255.2554,094
8161.5.0.0/2061.5.0.1 to 61.5.15.25461.5.15.2554,094
8261.5.16.0/2061.5.16.1 to 61.5.31.25461.5.31.2554,094
8361.5.32.0/2061.5.32.1 to 61.5.47.25461.5.47.2554,094
8461.5.48.0/2061.5.48.1 to 61.5.63.25461.5.63.2554,094
8561.5.64.0/2061.5.64.1 to 61.5.79.25461.5.79.2554,094
8661.5.80.0/2061.5.80.1 to 61.5.95.25461.5.95.2554,094
8761.5.96.0/2061.5.96.1 to 61.5.111.25461.5.111.2554,094
8861.5.112.0/2061.5.112.1 to 61.5.127.25461.5.127.2554,094
8961.5.128.0/2061.5.128.1 to 61.5.143.25461.5.143.2554,094
9061.5.144.0/2061.5.144.1 to 61.5.159.25461.5.159.2554,094
9161.5.160.0/2061.5.160.1 to 61.5.175.25461.5.175.2554,094
9261.5.176.0/2061.5.176.1 to 61.5.191.25461.5.191.2554,094
9361.5.192.0/2061.5.192.1 to 61.5.207.25461.5.207.2554,094
9461.5.208.0/2061.5.208.1 to 61.5.223.25461.5.223.2554,094
9561.5.224.0/2061.5.224.1 to 61.5.239.25461.5.239.2554,094
9661.5.240.0/2061.5.240.1 to 61.5.255.25461.5.255.2554,094
9761.6.0.0/2061.6.0.1 to 61.6.15.25461.6.15.2554,094
9861.6.16.0/2061.6.16.1 to 61.6.31.25461.6.31.2554,094
9961.6.32.0/2061.6.32.1 to 61.6.47.25461.6.47.2554,094
10061.6.48.0/2061.6.48.1 to 61.6.63.25461.6.63.2554,094
10161.6.64.0/2061.6.64.1 to 61.6.79.25461.6.79.2554,094
10261.6.80.0/2061.6.80.1 to 61.6.95.25461.6.95.2554,094
10361.6.96.0/2061.6.96.1 to 61.6.111.25461.6.111.2554,094
10461.6.112.0/2061.6.112.1 to 61.6.127.25461.6.127.2554,094
10561.6.128.0/2061.6.128.1 to 61.6.143.25461.6.143.2554,094
10661.6.144.0/2061.6.144.1 to 61.6.159.25461.6.159.2554,094
10761.6.160.0/2061.6.160.1 to 61.6.175.25461.6.175.2554,094
10861.6.176.0/2061.6.176.1 to 61.6.191.25461.6.191.2554,094
10961.6.192.0/2061.6.192.1 to 61.6.207.25461.6.207.2554,094
11061.6.208.0/2061.6.208.1 to 61.6.223.25461.6.223.2554,094
11161.6.224.0/2061.6.224.1 to 61.6.239.25461.6.239.2554,094
11261.6.240.0/2061.6.240.1 to 61.6.255.25461.6.255.2554,094
11361.7.0.0/2061.7.0.1 to 61.7.15.25461.7.15.2554,094
11461.7.16.0/2061.7.16.1 to 61.7.31.25461.7.31.2554,094
11561.7.32.0/2061.7.32.1 to 61.7.47.25461.7.47.2554,094
11661.7.48.0/2061.7.48.1 to 61.7.63.25461.7.63.2554,094
11761.7.64.0/2061.7.64.1 to 61.7.79.25461.7.79.2554,094
11861.7.80.0/2061.7.80.1 to 61.7.95.25461.7.95.2554,094
11961.7.96.0/2061.7.96.1 to 61.7.111.25461.7.111.2554,094
12061.7.112.0/2061.7.112.1 to 61.7.127.25461.7.127.2554,094
12161.7.128.0/2061.7.128.1 to 61.7.143.25461.7.143.2554,094
12261.7.144.0/2061.7.144.1 to 61.7.159.25461.7.159.2554,094
12361.7.160.0/2061.7.160.1 to 61.7.175.25461.7.175.2554,094
12461.7.176.0/2061.7.176.1 to 61.7.191.25461.7.191.2554,094
12561.7.192.0/2061.7.192.1 to 61.7.207.25461.7.207.2554,094
12661.7.208.0/2061.7.208.1 to 61.7.223.25461.7.223.2554,094
12761.7.224.0/2061.7.224.1 to 61.7.239.25461.7.239.2554,094
12861.7.240.0/2061.7.240.1 to 61.7.255.25461.7.255.2554,094
12961.8.0.0/2061.8.0.1 to 61.8.15.25461.8.15.2554,094
13061.8.16.0/2061.8.16.1 to 61.8.31.25461.8.31.2554,094
13161.8.32.0/2061.8.32.1 to 61.8.47.25461.8.47.2554,094
13261.8.48.0/2061.8.48.1 to 61.8.63.25461.8.63.2554,094
13361.8.64.0/2061.8.64.1 to 61.8.79.25461.8.79.2554,094
13461.8.80.0/2061.8.80.1 to 61.8.95.25461.8.95.2554,094
13561.8.96.0/2061.8.96.1 to 61.8.111.25461.8.111.2554,094
13661.8.112.0/2061.8.112.1 to 61.8.127.25461.8.127.2554,094
13761.8.128.0/2061.8.128.1 to 61.8.143.25461.8.143.2554,094
13861.8.144.0/2061.8.144.1 to 61.8.159.25461.8.159.2554,094
13961.8.160.0/2061.8.160.1 to 61.8.175.25461.8.175.2554,094
14061.8.176.0/2061.8.176.1 to 61.8.191.25461.8.191.2554,094
14161.8.192.0/2061.8.192.1 to 61.8.207.25461.8.207.2554,094
14261.8.208.0/2061.8.208.1 to 61.8.223.25461.8.223.2554,094
14361.8.224.0/2061.8.224.1 to 61.8.239.25461.8.239.2554,094
14461.8.240.0/2061.8.240.1 to 61.8.255.25461.8.255.2554,094
14561.9.0.0/2061.9.0.1 to 61.9.15.25461.9.15.2554,094
14661.9.16.0/2061.9.16.1 to 61.9.31.25461.9.31.2554,094
14761.9.32.0/2061.9.32.1 to 61.9.47.25461.9.47.2554,094
14861.9.48.0/2061.9.48.1 to 61.9.63.25461.9.63.2554,094
14961.9.64.0/2061.9.64.1 to 61.9.79.25461.9.79.2554,094
15061.9.80.0/2061.9.80.1 to 61.9.95.25461.9.95.2554,094
15161.9.96.0/2061.9.96.1 to 61.9.111.25461.9.111.2554,094
15261.9.112.0/2061.9.112.1 to 61.9.127.25461.9.127.2554,094
15361.9.128.0/2061.9.128.1 to 61.9.143.25461.9.143.2554,094
15461.9.144.0/2061.9.144.1 to 61.9.159.25461.9.159.2554,094
15561.9.160.0/2061.9.160.1 to 61.9.175.25461.9.175.2554,094
15661.9.176.0/2061.9.176.1 to 61.9.191.25461.9.191.2554,094
15761.9.192.0/2061.9.192.1 to 61.9.207.25461.9.207.2554,094
15861.9.208.0/2061.9.208.1 to 61.9.223.25461.9.223.2554,094
15961.9.224.0/2061.9.224.1 to 61.9.239.25461.9.239.2554,094
16061.9.240.0/2061.9.240.1 to 61.9.255.25461.9.255.2554,094
16161.10.0.0/2061.10.0.1 to 61.10.15.25461.10.15.2554,094
16261.10.16.0/2061.10.16.1 to 61.10.31.25461.10.31.2554,094
16361.10.32.0/2061.10.32.1 to 61.10.47.25461.10.47.2554,094
16461.10.48.0/2061.10.48.1 to 61.10.63.25461.10.63.2554,094
16561.10.64.0/2061.10.64.1 to 61.10.79.25461.10.79.2554,094
16661.10.80.0/2061.10.80.1 to 61.10.95.25461.10.95.2554,094
16761.10.96.0/2061.10.96.1 to 61.10.111.25461.10.111.2554,094
16861.10.112.0/2061.10.112.1 to 61.10.127.25461.10.127.2554,094
16961.10.128.0/2061.10.128.1 to 61.10.143.25461.10.143.2554,094
17061.10.144.0/2061.10.144.1 to 61.10.159.25461.10.159.2554,094
17161.10.160.0/2061.10.160.1 to 61.10.175.25461.10.175.2554,094
17261.10.176.0/2061.10.176.1 to 61.10.191.25461.10.191.2554,094
17361.10.192.0/2061.10.192.1 to 61.10.207.25461.10.207.2554,094
17461.10.208.0/2061.10.208.1 to 61.10.223.25461.10.223.2554,094
17561.10.224.0/2061.10.224.1 to 61.10.239.25461.10.239.2554,094
17661.10.240.0/2061.10.240.1 to 61.10.255.25461.10.255.2554,094
17761.11.0.0/2061.11.0.1 to 61.11.15.25461.11.15.2554,094
17861.11.16.0/2061.11.16.1 to 61.11.31.25461.11.31.2554,094
17961.11.32.0/2061.11.32.1 to 61.11.47.25461.11.47.2554,094
18061.11.48.0/2061.11.48.1 to 61.11.63.25461.11.63.2554,094
18161.11.64.0/2061.11.64.1 to 61.11.79.25461.11.79.2554,094
18261.11.80.0/2061.11.80.1 to 61.11.95.25461.11.95.2554,094
18361.11.96.0/2061.11.96.1 to 61.11.111.25461.11.111.2554,094
18461.11.112.0/2061.11.112.1 to 61.11.127.25461.11.127.2554,094
18561.11.128.0/2061.11.128.1 to 61.11.143.25461.11.143.2554,094
18661.11.144.0/2061.11.144.1 to 61.11.159.25461.11.159.2554,094
18761.11.160.0/2061.11.160.1 to 61.11.175.25461.11.175.2554,094
18861.11.176.0/2061.11.176.1 to 61.11.191.25461.11.191.2554,094
18961.11.192.0/2061.11.192.1 to 61.11.207.25461.11.207.2554,094
19061.11.208.0/2061.11.208.1 to 61.11.223.25461.11.223.2554,094
19161.11.224.0/2061.11.224.1 to 61.11.239.25461.11.239.2554,094
19261.11.240.0/2061.11.240.1 to 61.11.255.25461.11.255.2554,094
19361.12.0.0/2061.12.0.1 to 61.12.15.25461.12.15.2554,094
19461.12.16.0/2061.12.16.1 to 61.12.31.25461.12.31.2554,094
19561.12.32.0/2061.12.32.1 to 61.12.47.25461.12.47.2554,094
19661.12.48.0/2061.12.48.1 to 61.12.63.25461.12.63.2554,094
19761.12.64.0/2061.12.64.1 to 61.12.79.25461.12.79.2554,094
19861.12.80.0/2061.12.80.1 to 61.12.95.25461.12.95.2554,094
19961.12.96.0/2061.12.96.1 to 61.12.111.25461.12.111.2554,094
20061.12.112.0/2061.12.112.1 to 61.12.127.25461.12.127.2554,094
20161.12.128.0/2061.12.128.1 to 61.12.143.25461.12.143.2554,094
20261.12.144.0/2061.12.144.1 to 61.12.159.25461.12.159.2554,094
20361.12.160.0/2061.12.160.1 to 61.12.175.25461.12.175.2554,094
20461.12.176.0/2061.12.176.1 to 61.12.191.25461.12.191.2554,094
20561.12.192.0/2061.12.192.1 to 61.12.207.25461.12.207.2554,094
20661.12.208.0/2061.12.208.1 to 61.12.223.25461.12.223.2554,094
20761.12.224.0/2061.12.224.1 to 61.12.239.25461.12.239.2554,094
20861.12.240.0/2061.12.240.1 to 61.12.255.25461.12.255.2554,094
20961.13.0.0/2061.13.0.1 to 61.13.15.25461.13.15.2554,094
21061.13.16.0/2061.13.16.1 to 61.13.31.25461.13.31.2554,094
21161.13.32.0/2061.13.32.1 to 61.13.47.25461.13.47.2554,094
21261.13.48.0/2061.13.48.1 to 61.13.63.25461.13.63.2554,094
21361.13.64.0/2061.13.64.1 to 61.13.79.25461.13.79.2554,094
21461.13.80.0/2061.13.80.1 to 61.13.95.25461.13.95.2554,094
21561.13.96.0/2061.13.96.1 to 61.13.111.25461.13.111.2554,094
21661.13.112.0/2061.13.112.1 to 61.13.127.25461.13.127.2554,094
21761.13.128.0/2061.13.128.1 to 61.13.143.25461.13.143.2554,094
21861.13.144.0/2061.13.144.1 to 61.13.159.25461.13.159.2554,094
21961.13.160.0/2061.13.160.1 to 61.13.175.25461.13.175.2554,094
22061.13.176.0/2061.13.176.1 to 61.13.191.25461.13.191.2554,094
22161.13.192.0/2061.13.192.1 to 61.13.207.25461.13.207.2554,094
22261.13.208.0/2061.13.208.1 to 61.13.223.25461.13.223.2554,094
22361.13.224.0/2061.13.224.1 to 61.13.239.25461.13.239.2554,094
22461.13.240.0/2061.13.240.1 to 61.13.255.25461.13.255.2554,094
22561.14.0.0/2061.14.0.1 to 61.14.15.25461.14.15.2554,094
22661.14.16.0/2061.14.16.1 to 61.14.31.25461.14.31.2554,094
22761.14.32.0/2061.14.32.1 to 61.14.47.25461.14.47.2554,094
22861.14.48.0/2061.14.48.1 to 61.14.63.25461.14.63.2554,094
22961.14.64.0/2061.14.64.1 to 61.14.79.25461.14.79.2554,094
23061.14.80.0/2061.14.80.1 to 61.14.95.25461.14.95.2554,094
23161.14.96.0/2061.14.96.1 to 61.14.111.25461.14.111.2554,094
23261.14.112.0/2061.14.112.1 to 61.14.127.25461.14.127.2554,094
23361.14.128.0/2061.14.128.1 to 61.14.143.25461.14.143.2554,094
23461.14.144.0/2061.14.144.1 to 61.14.159.25461.14.159.2554,094
23561.14.160.0/2061.14.160.1 to 61.14.175.25461.14.175.2554,094
23661.14.176.0/2061.14.176.1 to 61.14.191.25461.14.191.2554,094
23761.14.192.0/2061.14.192.1 to 61.14.207.25461.14.207.2554,094
23861.14.208.0/2061.14.208.1 to 61.14.223.25461.14.223.2554,094
23961.14.224.0/2061.14.224.1 to 61.14.239.25461.14.239.2554,094
24061.14.240.0/2061.14.240.1 to 61.14.255.25461.14.255.2554,094
24161.15.0.0/2061.15.0.1 to 61.15.15.25461.15.15.2554,094
24261.15.16.0/2061.15.16.1 to 61.15.31.25461.15.31.2554,094
24361.15.32.0/2061.15.32.1 to 61.15.47.25461.15.47.2554,094
24461.15.48.0/2061.15.48.1 to 61.15.63.25461.15.63.2554,094
24561.15.64.0/2061.15.64.1 to 61.15.79.25461.15.79.2554,094
24661.15.80.0/2061.15.80.1 to 61.15.95.25461.15.95.2554,094
24761.15.96.0/2061.15.96.1 to 61.15.111.25461.15.111.2554,094
24861.15.112.0/2061.15.112.1 to 61.15.127.25461.15.127.2554,094
24961.15.128.0/2061.15.128.1 to 61.15.143.25461.15.143.2554,094
25061.15.144.0/2061.15.144.1 to 61.15.159.25461.15.159.2554,094
25161.15.160.0/2061.15.160.1 to 61.15.175.25461.15.175.2554,094
25261.15.176.0/2061.15.176.1 to 61.15.191.25461.15.191.2554,094
25361.15.192.0/2061.15.192.1 to 61.15.207.25461.15.207.2554,094
25461.15.208.0/2061.15.208.1 to 61.15.223.25461.15.223.2554,094
25561.15.224.0/2061.15.224.1 to 61.15.239.25461.15.239.2554,094
25661.15.240.0/2061.15.240.1 to 61.15.255.25461.15.255.2554,094

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.