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.

Prefix/16
Addresses2^112
/64 networks2^48
Network
20c7::/16
First address
20c7::
Last address
20c7:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
5,192,296,858,534,827,628,530,496,329,220,096 (2^112)
/64 networks (LANs)
281,474,976,710,656 (2^48)
Full form
20c7:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
7.c.0.2.ip6.arpa
Split into smaller subnets/32
/17 (2)/18 (4)/19 (8)/20 (16)/24 (256)/28 (4,096)/32 (65,536)

20c7::/16 makes 65,536 subnets of /32; the first 256 are listed.

Subnets
#SubnetLast address
120c7::/3220c7:0:ffff:ffff:ffff:ffff:ffff:ffff
220c7:1::/3220c7:1:ffff:ffff:ffff:ffff:ffff:ffff
320c7:2::/3220c7:2:ffff:ffff:ffff:ffff:ffff:ffff
420c7:3::/3220c7:3:ffff:ffff:ffff:ffff:ffff:ffff
520c7:4::/3220c7:4:ffff:ffff:ffff:ffff:ffff:ffff
620c7:5::/3220c7:5:ffff:ffff:ffff:ffff:ffff:ffff
720c7:6::/3220c7:6:ffff:ffff:ffff:ffff:ffff:ffff
820c7:7::/3220c7:7:ffff:ffff:ffff:ffff:ffff:ffff
920c7:8::/3220c7:8:ffff:ffff:ffff:ffff:ffff:ffff
1020c7:9::/3220c7:9:ffff:ffff:ffff:ffff:ffff:ffff
1120c7:a::/3220c7:a:ffff:ffff:ffff:ffff:ffff:ffff
1220c7:b::/3220c7:b:ffff:ffff:ffff:ffff:ffff:ffff
1320c7:c::/3220c7:c:ffff:ffff:ffff:ffff:ffff:ffff
1420c7:d::/3220c7:d:ffff:ffff:ffff:ffff:ffff:ffff
1520c7:e::/3220c7:e:ffff:ffff:ffff:ffff:ffff:ffff
1620c7:f::/3220c7:f:ffff:ffff:ffff:ffff:ffff:ffff
1720c7:10::/3220c7:10:ffff:ffff:ffff:ffff:ffff:ffff
1820c7:11::/3220c7:11:ffff:ffff:ffff:ffff:ffff:ffff
1920c7:12::/3220c7:12:ffff:ffff:ffff:ffff:ffff:ffff
2020c7:13::/3220c7:13:ffff:ffff:ffff:ffff:ffff:ffff
2120c7:14::/3220c7:14:ffff:ffff:ffff:ffff:ffff:ffff
2220c7:15::/3220c7:15:ffff:ffff:ffff:ffff:ffff:ffff
2320c7:16::/3220c7:16:ffff:ffff:ffff:ffff:ffff:ffff
2420c7:17::/3220c7:17:ffff:ffff:ffff:ffff:ffff:ffff
2520c7:18::/3220c7:18:ffff:ffff:ffff:ffff:ffff:ffff
2620c7:19::/3220c7:19:ffff:ffff:ffff:ffff:ffff:ffff
2720c7:1a::/3220c7:1a:ffff:ffff:ffff:ffff:ffff:ffff
2820c7:1b::/3220c7:1b:ffff:ffff:ffff:ffff:ffff:ffff
2920c7:1c::/3220c7:1c:ffff:ffff:ffff:ffff:ffff:ffff
3020c7:1d::/3220c7:1d:ffff:ffff:ffff:ffff:ffff:ffff
3120c7:1e::/3220c7:1e:ffff:ffff:ffff:ffff:ffff:ffff
3220c7:1f::/3220c7:1f:ffff:ffff:ffff:ffff:ffff:ffff
3320c7:20::/3220c7:20:ffff:ffff:ffff:ffff:ffff:ffff
3420c7:21::/3220c7:21:ffff:ffff:ffff:ffff:ffff:ffff
3520c7:22::/3220c7:22:ffff:ffff:ffff:ffff:ffff:ffff
3620c7:23::/3220c7:23:ffff:ffff:ffff:ffff:ffff:ffff
3720c7:24::/3220c7:24:ffff:ffff:ffff:ffff:ffff:ffff
3820c7:25::/3220c7:25:ffff:ffff:ffff:ffff:ffff:ffff
3920c7:26::/3220c7:26:ffff:ffff:ffff:ffff:ffff:ffff
4020c7:27::/3220c7:27:ffff:ffff:ffff:ffff:ffff:ffff
4120c7:28::/3220c7:28:ffff:ffff:ffff:ffff:ffff:ffff
4220c7:29::/3220c7:29:ffff:ffff:ffff:ffff:ffff:ffff
4320c7:2a::/3220c7:2a:ffff:ffff:ffff:ffff:ffff:ffff
4420c7:2b::/3220c7:2b:ffff:ffff:ffff:ffff:ffff:ffff
4520c7:2c::/3220c7:2c:ffff:ffff:ffff:ffff:ffff:ffff
4620c7:2d::/3220c7:2d:ffff:ffff:ffff:ffff:ffff:ffff
4720c7:2e::/3220c7:2e:ffff:ffff:ffff:ffff:ffff:ffff
4820c7:2f::/3220c7:2f:ffff:ffff:ffff:ffff:ffff:ffff
4920c7:30::/3220c7:30:ffff:ffff:ffff:ffff:ffff:ffff
5020c7:31::/3220c7:31:ffff:ffff:ffff:ffff:ffff:ffff
5120c7:32::/3220c7:32:ffff:ffff:ffff:ffff:ffff:ffff
5220c7:33::/3220c7:33:ffff:ffff:ffff:ffff:ffff:ffff
5320c7:34::/3220c7:34:ffff:ffff:ffff:ffff:ffff:ffff
5420c7:35::/3220c7:35:ffff:ffff:ffff:ffff:ffff:ffff
5520c7:36::/3220c7:36:ffff:ffff:ffff:ffff:ffff:ffff
5620c7:37::/3220c7:37:ffff:ffff:ffff:ffff:ffff:ffff
5720c7:38::/3220c7:38:ffff:ffff:ffff:ffff:ffff:ffff
5820c7:39::/3220c7:39:ffff:ffff:ffff:ffff:ffff:ffff
5920c7:3a::/3220c7:3a:ffff:ffff:ffff:ffff:ffff:ffff
6020c7:3b::/3220c7:3b:ffff:ffff:ffff:ffff:ffff:ffff
6120c7:3c::/3220c7:3c:ffff:ffff:ffff:ffff:ffff:ffff
6220c7:3d::/3220c7:3d:ffff:ffff:ffff:ffff:ffff:ffff
6320c7:3e::/3220c7:3e:ffff:ffff:ffff:ffff:ffff:ffff
6420c7:3f::/3220c7:3f:ffff:ffff:ffff:ffff:ffff:ffff
6520c7:40::/3220c7:40:ffff:ffff:ffff:ffff:ffff:ffff
6620c7:41::/3220c7:41:ffff:ffff:ffff:ffff:ffff:ffff
6720c7:42::/3220c7:42:ffff:ffff:ffff:ffff:ffff:ffff
6820c7:43::/3220c7:43:ffff:ffff:ffff:ffff:ffff:ffff
6920c7:44::/3220c7:44:ffff:ffff:ffff:ffff:ffff:ffff
7020c7:45::/3220c7:45:ffff:ffff:ffff:ffff:ffff:ffff
7120c7:46::/3220c7:46:ffff:ffff:ffff:ffff:ffff:ffff
7220c7:47::/3220c7:47:ffff:ffff:ffff:ffff:ffff:ffff
7320c7:48::/3220c7:48:ffff:ffff:ffff:ffff:ffff:ffff
7420c7:49::/3220c7:49:ffff:ffff:ffff:ffff:ffff:ffff
7520c7:4a::/3220c7:4a:ffff:ffff:ffff:ffff:ffff:ffff
7620c7:4b::/3220c7:4b:ffff:ffff:ffff:ffff:ffff:ffff
7720c7:4c::/3220c7:4c:ffff:ffff:ffff:ffff:ffff:ffff
7820c7:4d::/3220c7:4d:ffff:ffff:ffff:ffff:ffff:ffff
7920c7:4e::/3220c7:4e:ffff:ffff:ffff:ffff:ffff:ffff
8020c7:4f::/3220c7:4f:ffff:ffff:ffff:ffff:ffff:ffff
8120c7:50::/3220c7:50:ffff:ffff:ffff:ffff:ffff:ffff
8220c7:51::/3220c7:51:ffff:ffff:ffff:ffff:ffff:ffff
8320c7:52::/3220c7:52:ffff:ffff:ffff:ffff:ffff:ffff
8420c7:53::/3220c7:53:ffff:ffff:ffff:ffff:ffff:ffff
8520c7:54::/3220c7:54:ffff:ffff:ffff:ffff:ffff:ffff
8620c7:55::/3220c7:55:ffff:ffff:ffff:ffff:ffff:ffff
8720c7:56::/3220c7:56:ffff:ffff:ffff:ffff:ffff:ffff
8820c7:57::/3220c7:57:ffff:ffff:ffff:ffff:ffff:ffff
8920c7:58::/3220c7:58:ffff:ffff:ffff:ffff:ffff:ffff
9020c7:59::/3220c7:59:ffff:ffff:ffff:ffff:ffff:ffff
9120c7:5a::/3220c7:5a:ffff:ffff:ffff:ffff:ffff:ffff
9220c7:5b::/3220c7:5b:ffff:ffff:ffff:ffff:ffff:ffff
9320c7:5c::/3220c7:5c:ffff:ffff:ffff:ffff:ffff:ffff
9420c7:5d::/3220c7:5d:ffff:ffff:ffff:ffff:ffff:ffff
9520c7:5e::/3220c7:5e:ffff:ffff:ffff:ffff:ffff:ffff
9620c7:5f::/3220c7:5f:ffff:ffff:ffff:ffff:ffff:ffff
9720c7:60::/3220c7:60:ffff:ffff:ffff:ffff:ffff:ffff
9820c7:61::/3220c7:61:ffff:ffff:ffff:ffff:ffff:ffff
9920c7:62::/3220c7:62:ffff:ffff:ffff:ffff:ffff:ffff
10020c7:63::/3220c7:63:ffff:ffff:ffff:ffff:ffff:ffff
10120c7:64::/3220c7:64:ffff:ffff:ffff:ffff:ffff:ffff
10220c7:65::/3220c7:65:ffff:ffff:ffff:ffff:ffff:ffff
10320c7:66::/3220c7:66:ffff:ffff:ffff:ffff:ffff:ffff
10420c7:67::/3220c7:67:ffff:ffff:ffff:ffff:ffff:ffff
10520c7:68::/3220c7:68:ffff:ffff:ffff:ffff:ffff:ffff
10620c7:69::/3220c7:69:ffff:ffff:ffff:ffff:ffff:ffff
10720c7:6a::/3220c7:6a:ffff:ffff:ffff:ffff:ffff:ffff
10820c7:6b::/3220c7:6b:ffff:ffff:ffff:ffff:ffff:ffff
10920c7:6c::/3220c7:6c:ffff:ffff:ffff:ffff:ffff:ffff
11020c7:6d::/3220c7:6d:ffff:ffff:ffff:ffff:ffff:ffff
11120c7:6e::/3220c7:6e:ffff:ffff:ffff:ffff:ffff:ffff
11220c7:6f::/3220c7:6f:ffff:ffff:ffff:ffff:ffff:ffff
11320c7:70::/3220c7:70:ffff:ffff:ffff:ffff:ffff:ffff
11420c7:71::/3220c7:71:ffff:ffff:ffff:ffff:ffff:ffff
11520c7:72::/3220c7:72:ffff:ffff:ffff:ffff:ffff:ffff
11620c7:73::/3220c7:73:ffff:ffff:ffff:ffff:ffff:ffff
11720c7:74::/3220c7:74:ffff:ffff:ffff:ffff:ffff:ffff
11820c7:75::/3220c7:75:ffff:ffff:ffff:ffff:ffff:ffff
11920c7:76::/3220c7:76:ffff:ffff:ffff:ffff:ffff:ffff
12020c7:77::/3220c7:77:ffff:ffff:ffff:ffff:ffff:ffff
12120c7:78::/3220c7:78:ffff:ffff:ffff:ffff:ffff:ffff
12220c7:79::/3220c7:79:ffff:ffff:ffff:ffff:ffff:ffff
12320c7:7a::/3220c7:7a:ffff:ffff:ffff:ffff:ffff:ffff
12420c7:7b::/3220c7:7b:ffff:ffff:ffff:ffff:ffff:ffff
12520c7:7c::/3220c7:7c:ffff:ffff:ffff:ffff:ffff:ffff
12620c7:7d::/3220c7:7d:ffff:ffff:ffff:ffff:ffff:ffff
12720c7:7e::/3220c7:7e:ffff:ffff:ffff:ffff:ffff:ffff
12820c7:7f::/3220c7:7f:ffff:ffff:ffff:ffff:ffff:ffff
12920c7:80::/3220c7:80:ffff:ffff:ffff:ffff:ffff:ffff
13020c7:81::/3220c7:81:ffff:ffff:ffff:ffff:ffff:ffff
13120c7:82::/3220c7:82:ffff:ffff:ffff:ffff:ffff:ffff
13220c7:83::/3220c7:83:ffff:ffff:ffff:ffff:ffff:ffff
13320c7:84::/3220c7:84:ffff:ffff:ffff:ffff:ffff:ffff
13420c7:85::/3220c7:85:ffff:ffff:ffff:ffff:ffff:ffff
13520c7:86::/3220c7:86:ffff:ffff:ffff:ffff:ffff:ffff
13620c7:87::/3220c7:87:ffff:ffff:ffff:ffff:ffff:ffff
13720c7:88::/3220c7:88:ffff:ffff:ffff:ffff:ffff:ffff
13820c7:89::/3220c7:89:ffff:ffff:ffff:ffff:ffff:ffff
13920c7:8a::/3220c7:8a:ffff:ffff:ffff:ffff:ffff:ffff
14020c7:8b::/3220c7:8b:ffff:ffff:ffff:ffff:ffff:ffff
14120c7:8c::/3220c7:8c:ffff:ffff:ffff:ffff:ffff:ffff
14220c7:8d::/3220c7:8d:ffff:ffff:ffff:ffff:ffff:ffff
14320c7:8e::/3220c7:8e:ffff:ffff:ffff:ffff:ffff:ffff
14420c7:8f::/3220c7:8f:ffff:ffff:ffff:ffff:ffff:ffff
14520c7:90::/3220c7:90:ffff:ffff:ffff:ffff:ffff:ffff
14620c7:91::/3220c7:91:ffff:ffff:ffff:ffff:ffff:ffff
14720c7:92::/3220c7:92:ffff:ffff:ffff:ffff:ffff:ffff
14820c7:93::/3220c7:93:ffff:ffff:ffff:ffff:ffff:ffff
14920c7:94::/3220c7:94:ffff:ffff:ffff:ffff:ffff:ffff
15020c7:95::/3220c7:95:ffff:ffff:ffff:ffff:ffff:ffff
15120c7:96::/3220c7:96:ffff:ffff:ffff:ffff:ffff:ffff
15220c7:97::/3220c7:97:ffff:ffff:ffff:ffff:ffff:ffff
15320c7:98::/3220c7:98:ffff:ffff:ffff:ffff:ffff:ffff
15420c7:99::/3220c7:99:ffff:ffff:ffff:ffff:ffff:ffff
15520c7:9a::/3220c7:9a:ffff:ffff:ffff:ffff:ffff:ffff
15620c7:9b::/3220c7:9b:ffff:ffff:ffff:ffff:ffff:ffff
15720c7:9c::/3220c7:9c:ffff:ffff:ffff:ffff:ffff:ffff
15820c7:9d::/3220c7:9d:ffff:ffff:ffff:ffff:ffff:ffff
15920c7:9e::/3220c7:9e:ffff:ffff:ffff:ffff:ffff:ffff
16020c7:9f::/3220c7:9f:ffff:ffff:ffff:ffff:ffff:ffff
16120c7:a0::/3220c7:a0:ffff:ffff:ffff:ffff:ffff:ffff
16220c7:a1::/3220c7:a1:ffff:ffff:ffff:ffff:ffff:ffff
16320c7:a2::/3220c7:a2:ffff:ffff:ffff:ffff:ffff:ffff
16420c7:a3::/3220c7:a3:ffff:ffff:ffff:ffff:ffff:ffff
16520c7:a4::/3220c7:a4:ffff:ffff:ffff:ffff:ffff:ffff
16620c7:a5::/3220c7:a5:ffff:ffff:ffff:ffff:ffff:ffff
16720c7:a6::/3220c7:a6:ffff:ffff:ffff:ffff:ffff:ffff
16820c7:a7::/3220c7:a7:ffff:ffff:ffff:ffff:ffff:ffff
16920c7:a8::/3220c7:a8:ffff:ffff:ffff:ffff:ffff:ffff
17020c7:a9::/3220c7:a9:ffff:ffff:ffff:ffff:ffff:ffff
17120c7:aa::/3220c7:aa:ffff:ffff:ffff:ffff:ffff:ffff
17220c7:ab::/3220c7:ab:ffff:ffff:ffff:ffff:ffff:ffff
17320c7:ac::/3220c7:ac:ffff:ffff:ffff:ffff:ffff:ffff
17420c7:ad::/3220c7:ad:ffff:ffff:ffff:ffff:ffff:ffff
17520c7:ae::/3220c7:ae:ffff:ffff:ffff:ffff:ffff:ffff
17620c7:af::/3220c7:af:ffff:ffff:ffff:ffff:ffff:ffff
17720c7:b0::/3220c7:b0:ffff:ffff:ffff:ffff:ffff:ffff
17820c7:b1::/3220c7:b1:ffff:ffff:ffff:ffff:ffff:ffff
17920c7:b2::/3220c7:b2:ffff:ffff:ffff:ffff:ffff:ffff
18020c7:b3::/3220c7:b3:ffff:ffff:ffff:ffff:ffff:ffff
18120c7:b4::/3220c7:b4:ffff:ffff:ffff:ffff:ffff:ffff
18220c7:b5::/3220c7:b5:ffff:ffff:ffff:ffff:ffff:ffff
18320c7:b6::/3220c7:b6:ffff:ffff:ffff:ffff:ffff:ffff
18420c7:b7::/3220c7:b7:ffff:ffff:ffff:ffff:ffff:ffff
18520c7:b8::/3220c7:b8:ffff:ffff:ffff:ffff:ffff:ffff
18620c7:b9::/3220c7:b9:ffff:ffff:ffff:ffff:ffff:ffff
18720c7:ba::/3220c7:ba:ffff:ffff:ffff:ffff:ffff:ffff
18820c7:bb::/3220c7:bb:ffff:ffff:ffff:ffff:ffff:ffff
18920c7:bc::/3220c7:bc:ffff:ffff:ffff:ffff:ffff:ffff
19020c7:bd::/3220c7:bd:ffff:ffff:ffff:ffff:ffff:ffff
19120c7:be::/3220c7:be:ffff:ffff:ffff:ffff:ffff:ffff
19220c7:bf::/3220c7:bf:ffff:ffff:ffff:ffff:ffff:ffff
19320c7:c0::/3220c7:c0:ffff:ffff:ffff:ffff:ffff:ffff
19420c7:c1::/3220c7:c1:ffff:ffff:ffff:ffff:ffff:ffff
19520c7:c2::/3220c7:c2:ffff:ffff:ffff:ffff:ffff:ffff
19620c7:c3::/3220c7:c3:ffff:ffff:ffff:ffff:ffff:ffff
19720c7:c4::/3220c7:c4:ffff:ffff:ffff:ffff:ffff:ffff
19820c7:c5::/3220c7:c5:ffff:ffff:ffff:ffff:ffff:ffff
19920c7:c6::/3220c7:c6:ffff:ffff:ffff:ffff:ffff:ffff
20020c7:c7::/3220c7:c7:ffff:ffff:ffff:ffff:ffff:ffff
20120c7:c8::/3220c7:c8:ffff:ffff:ffff:ffff:ffff:ffff
20220c7:c9::/3220c7:c9:ffff:ffff:ffff:ffff:ffff:ffff
20320c7:ca::/3220c7:ca:ffff:ffff:ffff:ffff:ffff:ffff
20420c7:cb::/3220c7:cb:ffff:ffff:ffff:ffff:ffff:ffff
20520c7:cc::/3220c7:cc:ffff:ffff:ffff:ffff:ffff:ffff
20620c7:cd::/3220c7:cd:ffff:ffff:ffff:ffff:ffff:ffff
20720c7:ce::/3220c7:ce:ffff:ffff:ffff:ffff:ffff:ffff
20820c7:cf::/3220c7:cf:ffff:ffff:ffff:ffff:ffff:ffff
20920c7:d0::/3220c7:d0:ffff:ffff:ffff:ffff:ffff:ffff
21020c7:d1::/3220c7:d1:ffff:ffff:ffff:ffff:ffff:ffff
21120c7:d2::/3220c7:d2:ffff:ffff:ffff:ffff:ffff:ffff
21220c7:d3::/3220c7:d3:ffff:ffff:ffff:ffff:ffff:ffff
21320c7:d4::/3220c7:d4:ffff:ffff:ffff:ffff:ffff:ffff
21420c7:d5::/3220c7:d5:ffff:ffff:ffff:ffff:ffff:ffff
21520c7:d6::/3220c7:d6:ffff:ffff:ffff:ffff:ffff:ffff
21620c7:d7::/3220c7:d7:ffff:ffff:ffff:ffff:ffff:ffff
21720c7:d8::/3220c7:d8:ffff:ffff:ffff:ffff:ffff:ffff
21820c7:d9::/3220c7:d9:ffff:ffff:ffff:ffff:ffff:ffff
21920c7:da::/3220c7:da:ffff:ffff:ffff:ffff:ffff:ffff
22020c7:db::/3220c7:db:ffff:ffff:ffff:ffff:ffff:ffff
22120c7:dc::/3220c7:dc:ffff:ffff:ffff:ffff:ffff:ffff
22220c7:dd::/3220c7:dd:ffff:ffff:ffff:ffff:ffff:ffff
22320c7:de::/3220c7:de:ffff:ffff:ffff:ffff:ffff:ffff
22420c7:df::/3220c7:df:ffff:ffff:ffff:ffff:ffff:ffff
22520c7:e0::/3220c7:e0:ffff:ffff:ffff:ffff:ffff:ffff
22620c7:e1::/3220c7:e1:ffff:ffff:ffff:ffff:ffff:ffff
22720c7:e2::/3220c7:e2:ffff:ffff:ffff:ffff:ffff:ffff
22820c7:e3::/3220c7:e3:ffff:ffff:ffff:ffff:ffff:ffff
22920c7:e4::/3220c7:e4:ffff:ffff:ffff:ffff:ffff:ffff
23020c7:e5::/3220c7:e5:ffff:ffff:ffff:ffff:ffff:ffff
23120c7:e6::/3220c7:e6:ffff:ffff:ffff:ffff:ffff:ffff
23220c7:e7::/3220c7:e7:ffff:ffff:ffff:ffff:ffff:ffff
23320c7:e8::/3220c7:e8:ffff:ffff:ffff:ffff:ffff:ffff
23420c7:e9::/3220c7:e9:ffff:ffff:ffff:ffff:ffff:ffff
23520c7:ea::/3220c7:ea:ffff:ffff:ffff:ffff:ffff:ffff
23620c7:eb::/3220c7:eb:ffff:ffff:ffff:ffff:ffff:ffff
23720c7:ec::/3220c7:ec:ffff:ffff:ffff:ffff:ffff:ffff
23820c7:ed::/3220c7:ed:ffff:ffff:ffff:ffff:ffff:ffff
23920c7:ee::/3220c7:ee:ffff:ffff:ffff:ffff:ffff:ffff
24020c7:ef::/3220c7:ef:ffff:ffff:ffff:ffff:ffff:ffff
24120c7:f0::/3220c7:f0:ffff:ffff:ffff:ffff:ffff:ffff
24220c7:f1::/3220c7:f1:ffff:ffff:ffff:ffff:ffff:ffff
24320c7:f2::/3220c7:f2:ffff:ffff:ffff:ffff:ffff:ffff
24420c7:f3::/3220c7:f3:ffff:ffff:ffff:ffff:ffff:ffff
24520c7:f4::/3220c7:f4:ffff:ffff:ffff:ffff:ffff:ffff
24620c7:f5::/3220c7:f5:ffff:ffff:ffff:ffff:ffff:ffff
24720c7:f6::/3220c7:f6:ffff:ffff:ffff:ffff:ffff:ffff
24820c7:f7::/3220c7:f7:ffff:ffff:ffff:ffff:ffff:ffff
24920c7:f8::/3220c7:f8:ffff:ffff:ffff:ffff:ffff:ffff
25020c7:f9::/3220c7:f9:ffff:ffff:ffff:ffff:ffff:ffff
25120c7:fa::/3220c7:fa:ffff:ffff:ffff:ffff:ffff:ffff
25220c7:fb::/3220c7:fb:ffff:ffff:ffff:ffff:ffff:ffff
25320c7:fc::/3220c7:fc:ffff:ffff:ffff:ffff:ffff:ffff
25420c7:fd::/3220c7:fd:ffff:ffff:ffff:ffff:ffff:ffff
25520c7:fe::/3220c7:fe:ffff:ffff:ffff:ffff:ffff:ffff
25620c7:ff::/3220c7:ff:ffff:ffff:ffff:ffff:ffff:ffff

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.