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/112
Addresses65,536
/64 networksPart of one
Network
2c19:dd:d9:dd:c25:c25:c4bb:0/112
First address
2c19:dd:d9:dd:c25:c25:c4bb:0
Last address
2c19:dd:d9:dd:c25:c25:c4bb:ffff
Addresses
65,536
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
2c19:00dd:00d9:00dd:0c25:0c25:c4bb:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
b.b.4.c.5.2.c.0.5.2.c.0.d.d.0.0.9.d.0.0.d.d.0.0.9.1.c.2.ip6.arpa
Split into smaller subnets/120
/113 (2)/114 (4)/115 (8)/116 (16)/120 (256)/124 (4,096)/127 (32,768)/128 (65,536)

2c19:dd:d9:dd:c25:c25:c4bb:0/112 makes 256 subnets of /120.

Subnets
#SubnetLast address
12c19:dd:d9:dd:c25:c25:c4bb:0/1202c19:dd:d9:dd:c25:c25:c4bb:ff
22c19:dd:d9:dd:c25:c25:c4bb:100/1202c19:dd:d9:dd:c25:c25:c4bb:1ff
32c19:dd:d9:dd:c25:c25:c4bb:200/1202c19:dd:d9:dd:c25:c25:c4bb:2ff
42c19:dd:d9:dd:c25:c25:c4bb:300/1202c19:dd:d9:dd:c25:c25:c4bb:3ff
52c19:dd:d9:dd:c25:c25:c4bb:400/1202c19:dd:d9:dd:c25:c25:c4bb:4ff
62c19:dd:d9:dd:c25:c25:c4bb:500/1202c19:dd:d9:dd:c25:c25:c4bb:5ff
72c19:dd:d9:dd:c25:c25:c4bb:600/1202c19:dd:d9:dd:c25:c25:c4bb:6ff
82c19:dd:d9:dd:c25:c25:c4bb:700/1202c19:dd:d9:dd:c25:c25:c4bb:7ff
92c19:dd:d9:dd:c25:c25:c4bb:800/1202c19:dd:d9:dd:c25:c25:c4bb:8ff
102c19:dd:d9:dd:c25:c25:c4bb:900/1202c19:dd:d9:dd:c25:c25:c4bb:9ff
112c19:dd:d9:dd:c25:c25:c4bb:a00/1202c19:dd:d9:dd:c25:c25:c4bb:aff
122c19:dd:d9:dd:c25:c25:c4bb:b00/1202c19:dd:d9:dd:c25:c25:c4bb:bff
132c19:dd:d9:dd:c25:c25:c4bb:c00/1202c19:dd:d9:dd:c25:c25:c4bb:cff
142c19:dd:d9:dd:c25:c25:c4bb:d00/1202c19:dd:d9:dd:c25:c25:c4bb:dff
152c19:dd:d9:dd:c25:c25:c4bb:e00/1202c19:dd:d9:dd:c25:c25:c4bb:eff
162c19:dd:d9:dd:c25:c25:c4bb:f00/1202c19:dd:d9:dd:c25:c25:c4bb:fff
172c19:dd:d9:dd:c25:c25:c4bb:1000/1202c19:dd:d9:dd:c25:c25:c4bb:10ff
182c19:dd:d9:dd:c25:c25:c4bb:1100/1202c19:dd:d9:dd:c25:c25:c4bb:11ff
192c19:dd:d9:dd:c25:c25:c4bb:1200/1202c19:dd:d9:dd:c25:c25:c4bb:12ff
202c19:dd:d9:dd:c25:c25:c4bb:1300/1202c19:dd:d9:dd:c25:c25:c4bb:13ff
212c19:dd:d9:dd:c25:c25:c4bb:1400/1202c19:dd:d9:dd:c25:c25:c4bb:14ff
222c19:dd:d9:dd:c25:c25:c4bb:1500/1202c19:dd:d9:dd:c25:c25:c4bb:15ff
232c19:dd:d9:dd:c25:c25:c4bb:1600/1202c19:dd:d9:dd:c25:c25:c4bb:16ff
242c19:dd:d9:dd:c25:c25:c4bb:1700/1202c19:dd:d9:dd:c25:c25:c4bb:17ff
252c19:dd:d9:dd:c25:c25:c4bb:1800/1202c19:dd:d9:dd:c25:c25:c4bb:18ff
262c19:dd:d9:dd:c25:c25:c4bb:1900/1202c19:dd:d9:dd:c25:c25:c4bb:19ff
272c19:dd:d9:dd:c25:c25:c4bb:1a00/1202c19:dd:d9:dd:c25:c25:c4bb:1aff
282c19:dd:d9:dd:c25:c25:c4bb:1b00/1202c19:dd:d9:dd:c25:c25:c4bb:1bff
292c19:dd:d9:dd:c25:c25:c4bb:1c00/1202c19:dd:d9:dd:c25:c25:c4bb:1cff
302c19:dd:d9:dd:c25:c25:c4bb:1d00/1202c19:dd:d9:dd:c25:c25:c4bb:1dff
312c19:dd:d9:dd:c25:c25:c4bb:1e00/1202c19:dd:d9:dd:c25:c25:c4bb:1eff
322c19:dd:d9:dd:c25:c25:c4bb:1f00/1202c19:dd:d9:dd:c25:c25:c4bb:1fff
332c19:dd:d9:dd:c25:c25:c4bb:2000/1202c19:dd:d9:dd:c25:c25:c4bb:20ff
342c19:dd:d9:dd:c25:c25:c4bb:2100/1202c19:dd:d9:dd:c25:c25:c4bb:21ff
352c19:dd:d9:dd:c25:c25:c4bb:2200/1202c19:dd:d9:dd:c25:c25:c4bb:22ff
362c19:dd:d9:dd:c25:c25:c4bb:2300/1202c19:dd:d9:dd:c25:c25:c4bb:23ff
372c19:dd:d9:dd:c25:c25:c4bb:2400/1202c19:dd:d9:dd:c25:c25:c4bb:24ff
382c19:dd:d9:dd:c25:c25:c4bb:2500/1202c19:dd:d9:dd:c25:c25:c4bb:25ff
392c19:dd:d9:dd:c25:c25:c4bb:2600/1202c19:dd:d9:dd:c25:c25:c4bb:26ff
402c19:dd:d9:dd:c25:c25:c4bb:2700/1202c19:dd:d9:dd:c25:c25:c4bb:27ff
412c19:dd:d9:dd:c25:c25:c4bb:2800/1202c19:dd:d9:dd:c25:c25:c4bb:28ff
422c19:dd:d9:dd:c25:c25:c4bb:2900/1202c19:dd:d9:dd:c25:c25:c4bb:29ff
432c19:dd:d9:dd:c25:c25:c4bb:2a00/1202c19:dd:d9:dd:c25:c25:c4bb:2aff
442c19:dd:d9:dd:c25:c25:c4bb:2b00/1202c19:dd:d9:dd:c25:c25:c4bb:2bff
452c19:dd:d9:dd:c25:c25:c4bb:2c00/1202c19:dd:d9:dd:c25:c25:c4bb:2cff
462c19:dd:d9:dd:c25:c25:c4bb:2d00/1202c19:dd:d9:dd:c25:c25:c4bb:2dff
472c19:dd:d9:dd:c25:c25:c4bb:2e00/1202c19:dd:d9:dd:c25:c25:c4bb:2eff
482c19:dd:d9:dd:c25:c25:c4bb:2f00/1202c19:dd:d9:dd:c25:c25:c4bb:2fff
492c19:dd:d9:dd:c25:c25:c4bb:3000/1202c19:dd:d9:dd:c25:c25:c4bb:30ff
502c19:dd:d9:dd:c25:c25:c4bb:3100/1202c19:dd:d9:dd:c25:c25:c4bb:31ff
512c19:dd:d9:dd:c25:c25:c4bb:3200/1202c19:dd:d9:dd:c25:c25:c4bb:32ff
522c19:dd:d9:dd:c25:c25:c4bb:3300/1202c19:dd:d9:dd:c25:c25:c4bb:33ff
532c19:dd:d9:dd:c25:c25:c4bb:3400/1202c19:dd:d9:dd:c25:c25:c4bb:34ff
542c19:dd:d9:dd:c25:c25:c4bb:3500/1202c19:dd:d9:dd:c25:c25:c4bb:35ff
552c19:dd:d9:dd:c25:c25:c4bb:3600/1202c19:dd:d9:dd:c25:c25:c4bb:36ff
562c19:dd:d9:dd:c25:c25:c4bb:3700/1202c19:dd:d9:dd:c25:c25:c4bb:37ff
572c19:dd:d9:dd:c25:c25:c4bb:3800/1202c19:dd:d9:dd:c25:c25:c4bb:38ff
582c19:dd:d9:dd:c25:c25:c4bb:3900/1202c19:dd:d9:dd:c25:c25:c4bb:39ff
592c19:dd:d9:dd:c25:c25:c4bb:3a00/1202c19:dd:d9:dd:c25:c25:c4bb:3aff
602c19:dd:d9:dd:c25:c25:c4bb:3b00/1202c19:dd:d9:dd:c25:c25:c4bb:3bff
612c19:dd:d9:dd:c25:c25:c4bb:3c00/1202c19:dd:d9:dd:c25:c25:c4bb:3cff
622c19:dd:d9:dd:c25:c25:c4bb:3d00/1202c19:dd:d9:dd:c25:c25:c4bb:3dff
632c19:dd:d9:dd:c25:c25:c4bb:3e00/1202c19:dd:d9:dd:c25:c25:c4bb:3eff
642c19:dd:d9:dd:c25:c25:c4bb:3f00/1202c19:dd:d9:dd:c25:c25:c4bb:3fff
652c19:dd:d9:dd:c25:c25:c4bb:4000/1202c19:dd:d9:dd:c25:c25:c4bb:40ff
662c19:dd:d9:dd:c25:c25:c4bb:4100/1202c19:dd:d9:dd:c25:c25:c4bb:41ff
672c19:dd:d9:dd:c25:c25:c4bb:4200/1202c19:dd:d9:dd:c25:c25:c4bb:42ff
682c19:dd:d9:dd:c25:c25:c4bb:4300/1202c19:dd:d9:dd:c25:c25:c4bb:43ff
692c19:dd:d9:dd:c25:c25:c4bb:4400/1202c19:dd:d9:dd:c25:c25:c4bb:44ff
702c19:dd:d9:dd:c25:c25:c4bb:4500/1202c19:dd:d9:dd:c25:c25:c4bb:45ff
712c19:dd:d9:dd:c25:c25:c4bb:4600/1202c19:dd:d9:dd:c25:c25:c4bb:46ff
722c19:dd:d9:dd:c25:c25:c4bb:4700/1202c19:dd:d9:dd:c25:c25:c4bb:47ff
732c19:dd:d9:dd:c25:c25:c4bb:4800/1202c19:dd:d9:dd:c25:c25:c4bb:48ff
742c19:dd:d9:dd:c25:c25:c4bb:4900/1202c19:dd:d9:dd:c25:c25:c4bb:49ff
752c19:dd:d9:dd:c25:c25:c4bb:4a00/1202c19:dd:d9:dd:c25:c25:c4bb:4aff
762c19:dd:d9:dd:c25:c25:c4bb:4b00/1202c19:dd:d9:dd:c25:c25:c4bb:4bff
772c19:dd:d9:dd:c25:c25:c4bb:4c00/1202c19:dd:d9:dd:c25:c25:c4bb:4cff
782c19:dd:d9:dd:c25:c25:c4bb:4d00/1202c19:dd:d9:dd:c25:c25:c4bb:4dff
792c19:dd:d9:dd:c25:c25:c4bb:4e00/1202c19:dd:d9:dd:c25:c25:c4bb:4eff
802c19:dd:d9:dd:c25:c25:c4bb:4f00/1202c19:dd:d9:dd:c25:c25:c4bb:4fff
812c19:dd:d9:dd:c25:c25:c4bb:5000/1202c19:dd:d9:dd:c25:c25:c4bb:50ff
822c19:dd:d9:dd:c25:c25:c4bb:5100/1202c19:dd:d9:dd:c25:c25:c4bb:51ff
832c19:dd:d9:dd:c25:c25:c4bb:5200/1202c19:dd:d9:dd:c25:c25:c4bb:52ff
842c19:dd:d9:dd:c25:c25:c4bb:5300/1202c19:dd:d9:dd:c25:c25:c4bb:53ff
852c19:dd:d9:dd:c25:c25:c4bb:5400/1202c19:dd:d9:dd:c25:c25:c4bb:54ff
862c19:dd:d9:dd:c25:c25:c4bb:5500/1202c19:dd:d9:dd:c25:c25:c4bb:55ff
872c19:dd:d9:dd:c25:c25:c4bb:5600/1202c19:dd:d9:dd:c25:c25:c4bb:56ff
882c19:dd:d9:dd:c25:c25:c4bb:5700/1202c19:dd:d9:dd:c25:c25:c4bb:57ff
892c19:dd:d9:dd:c25:c25:c4bb:5800/1202c19:dd:d9:dd:c25:c25:c4bb:58ff
902c19:dd:d9:dd:c25:c25:c4bb:5900/1202c19:dd:d9:dd:c25:c25:c4bb:59ff
912c19:dd:d9:dd:c25:c25:c4bb:5a00/1202c19:dd:d9:dd:c25:c25:c4bb:5aff
922c19:dd:d9:dd:c25:c25:c4bb:5b00/1202c19:dd:d9:dd:c25:c25:c4bb:5bff
932c19:dd:d9:dd:c25:c25:c4bb:5c00/1202c19:dd:d9:dd:c25:c25:c4bb:5cff
942c19:dd:d9:dd:c25:c25:c4bb:5d00/1202c19:dd:d9:dd:c25:c25:c4bb:5dff
952c19:dd:d9:dd:c25:c25:c4bb:5e00/1202c19:dd:d9:dd:c25:c25:c4bb:5eff
962c19:dd:d9:dd:c25:c25:c4bb:5f00/1202c19:dd:d9:dd:c25:c25:c4bb:5fff
972c19:dd:d9:dd:c25:c25:c4bb:6000/1202c19:dd:d9:dd:c25:c25:c4bb:60ff
982c19:dd:d9:dd:c25:c25:c4bb:6100/1202c19:dd:d9:dd:c25:c25:c4bb:61ff
992c19:dd:d9:dd:c25:c25:c4bb:6200/1202c19:dd:d9:dd:c25:c25:c4bb:62ff
1002c19:dd:d9:dd:c25:c25:c4bb:6300/1202c19:dd:d9:dd:c25:c25:c4bb:63ff
1012c19:dd:d9:dd:c25:c25:c4bb:6400/1202c19:dd:d9:dd:c25:c25:c4bb:64ff
1022c19:dd:d9:dd:c25:c25:c4bb:6500/1202c19:dd:d9:dd:c25:c25:c4bb:65ff
1032c19:dd:d9:dd:c25:c25:c4bb:6600/1202c19:dd:d9:dd:c25:c25:c4bb:66ff
1042c19:dd:d9:dd:c25:c25:c4bb:6700/1202c19:dd:d9:dd:c25:c25:c4bb:67ff
1052c19:dd:d9:dd:c25:c25:c4bb:6800/1202c19:dd:d9:dd:c25:c25:c4bb:68ff
1062c19:dd:d9:dd:c25:c25:c4bb:6900/1202c19:dd:d9:dd:c25:c25:c4bb:69ff
1072c19:dd:d9:dd:c25:c25:c4bb:6a00/1202c19:dd:d9:dd:c25:c25:c4bb:6aff
1082c19:dd:d9:dd:c25:c25:c4bb:6b00/1202c19:dd:d9:dd:c25:c25:c4bb:6bff
1092c19:dd:d9:dd:c25:c25:c4bb:6c00/1202c19:dd:d9:dd:c25:c25:c4bb:6cff
1102c19:dd:d9:dd:c25:c25:c4bb:6d00/1202c19:dd:d9:dd:c25:c25:c4bb:6dff
1112c19:dd:d9:dd:c25:c25:c4bb:6e00/1202c19:dd:d9:dd:c25:c25:c4bb:6eff
1122c19:dd:d9:dd:c25:c25:c4bb:6f00/1202c19:dd:d9:dd:c25:c25:c4bb:6fff
1132c19:dd:d9:dd:c25:c25:c4bb:7000/1202c19:dd:d9:dd:c25:c25:c4bb:70ff
1142c19:dd:d9:dd:c25:c25:c4bb:7100/1202c19:dd:d9:dd:c25:c25:c4bb:71ff
1152c19:dd:d9:dd:c25:c25:c4bb:7200/1202c19:dd:d9:dd:c25:c25:c4bb:72ff
1162c19:dd:d9:dd:c25:c25:c4bb:7300/1202c19:dd:d9:dd:c25:c25:c4bb:73ff
1172c19:dd:d9:dd:c25:c25:c4bb:7400/1202c19:dd:d9:dd:c25:c25:c4bb:74ff
1182c19:dd:d9:dd:c25:c25:c4bb:7500/1202c19:dd:d9:dd:c25:c25:c4bb:75ff
1192c19:dd:d9:dd:c25:c25:c4bb:7600/1202c19:dd:d9:dd:c25:c25:c4bb:76ff
1202c19:dd:d9:dd:c25:c25:c4bb:7700/1202c19:dd:d9:dd:c25:c25:c4bb:77ff
1212c19:dd:d9:dd:c25:c25:c4bb:7800/1202c19:dd:d9:dd:c25:c25:c4bb:78ff
1222c19:dd:d9:dd:c25:c25:c4bb:7900/1202c19:dd:d9:dd:c25:c25:c4bb:79ff
1232c19:dd:d9:dd:c25:c25:c4bb:7a00/1202c19:dd:d9:dd:c25:c25:c4bb:7aff
1242c19:dd:d9:dd:c25:c25:c4bb:7b00/1202c19:dd:d9:dd:c25:c25:c4bb:7bff
1252c19:dd:d9:dd:c25:c25:c4bb:7c00/1202c19:dd:d9:dd:c25:c25:c4bb:7cff
1262c19:dd:d9:dd:c25:c25:c4bb:7d00/1202c19:dd:d9:dd:c25:c25:c4bb:7dff
1272c19:dd:d9:dd:c25:c25:c4bb:7e00/1202c19:dd:d9:dd:c25:c25:c4bb:7eff
1282c19:dd:d9:dd:c25:c25:c4bb:7f00/1202c19:dd:d9:dd:c25:c25:c4bb:7fff
1292c19:dd:d9:dd:c25:c25:c4bb:8000/1202c19:dd:d9:dd:c25:c25:c4bb:80ff
1302c19:dd:d9:dd:c25:c25:c4bb:8100/1202c19:dd:d9:dd:c25:c25:c4bb:81ff
1312c19:dd:d9:dd:c25:c25:c4bb:8200/1202c19:dd:d9:dd:c25:c25:c4bb:82ff
1322c19:dd:d9:dd:c25:c25:c4bb:8300/1202c19:dd:d9:dd:c25:c25:c4bb:83ff
1332c19:dd:d9:dd:c25:c25:c4bb:8400/1202c19:dd:d9:dd:c25:c25:c4bb:84ff
1342c19:dd:d9:dd:c25:c25:c4bb:8500/1202c19:dd:d9:dd:c25:c25:c4bb:85ff
1352c19:dd:d9:dd:c25:c25:c4bb:8600/1202c19:dd:d9:dd:c25:c25:c4bb:86ff
1362c19:dd:d9:dd:c25:c25:c4bb:8700/1202c19:dd:d9:dd:c25:c25:c4bb:87ff
1372c19:dd:d9:dd:c25:c25:c4bb:8800/1202c19:dd:d9:dd:c25:c25:c4bb:88ff
1382c19:dd:d9:dd:c25:c25:c4bb:8900/1202c19:dd:d9:dd:c25:c25:c4bb:89ff
1392c19:dd:d9:dd:c25:c25:c4bb:8a00/1202c19:dd:d9:dd:c25:c25:c4bb:8aff
1402c19:dd:d9:dd:c25:c25:c4bb:8b00/1202c19:dd:d9:dd:c25:c25:c4bb:8bff
1412c19:dd:d9:dd:c25:c25:c4bb:8c00/1202c19:dd:d9:dd:c25:c25:c4bb:8cff
1422c19:dd:d9:dd:c25:c25:c4bb:8d00/1202c19:dd:d9:dd:c25:c25:c4bb:8dff
1432c19:dd:d9:dd:c25:c25:c4bb:8e00/1202c19:dd:d9:dd:c25:c25:c4bb:8eff
1442c19:dd:d9:dd:c25:c25:c4bb:8f00/1202c19:dd:d9:dd:c25:c25:c4bb:8fff
1452c19:dd:d9:dd:c25:c25:c4bb:9000/1202c19:dd:d9:dd:c25:c25:c4bb:90ff
1462c19:dd:d9:dd:c25:c25:c4bb:9100/1202c19:dd:d9:dd:c25:c25:c4bb:91ff
1472c19:dd:d9:dd:c25:c25:c4bb:9200/1202c19:dd:d9:dd:c25:c25:c4bb:92ff
1482c19:dd:d9:dd:c25:c25:c4bb:9300/1202c19:dd:d9:dd:c25:c25:c4bb:93ff
1492c19:dd:d9:dd:c25:c25:c4bb:9400/1202c19:dd:d9:dd:c25:c25:c4bb:94ff
1502c19:dd:d9:dd:c25:c25:c4bb:9500/1202c19:dd:d9:dd:c25:c25:c4bb:95ff
1512c19:dd:d9:dd:c25:c25:c4bb:9600/1202c19:dd:d9:dd:c25:c25:c4bb:96ff
1522c19:dd:d9:dd:c25:c25:c4bb:9700/1202c19:dd:d9:dd:c25:c25:c4bb:97ff
1532c19:dd:d9:dd:c25:c25:c4bb:9800/1202c19:dd:d9:dd:c25:c25:c4bb:98ff
1542c19:dd:d9:dd:c25:c25:c4bb:9900/1202c19:dd:d9:dd:c25:c25:c4bb:99ff
1552c19:dd:d9:dd:c25:c25:c4bb:9a00/1202c19:dd:d9:dd:c25:c25:c4bb:9aff
1562c19:dd:d9:dd:c25:c25:c4bb:9b00/1202c19:dd:d9:dd:c25:c25:c4bb:9bff
1572c19:dd:d9:dd:c25:c25:c4bb:9c00/1202c19:dd:d9:dd:c25:c25:c4bb:9cff
1582c19:dd:d9:dd:c25:c25:c4bb:9d00/1202c19:dd:d9:dd:c25:c25:c4bb:9dff
1592c19:dd:d9:dd:c25:c25:c4bb:9e00/1202c19:dd:d9:dd:c25:c25:c4bb:9eff
1602c19:dd:d9:dd:c25:c25:c4bb:9f00/1202c19:dd:d9:dd:c25:c25:c4bb:9fff
1612c19:dd:d9:dd:c25:c25:c4bb:a000/1202c19:dd:d9:dd:c25:c25:c4bb:a0ff
1622c19:dd:d9:dd:c25:c25:c4bb:a100/1202c19:dd:d9:dd:c25:c25:c4bb:a1ff
1632c19:dd:d9:dd:c25:c25:c4bb:a200/1202c19:dd:d9:dd:c25:c25:c4bb:a2ff
1642c19:dd:d9:dd:c25:c25:c4bb:a300/1202c19:dd:d9:dd:c25:c25:c4bb:a3ff
1652c19:dd:d9:dd:c25:c25:c4bb:a400/1202c19:dd:d9:dd:c25:c25:c4bb:a4ff
1662c19:dd:d9:dd:c25:c25:c4bb:a500/1202c19:dd:d9:dd:c25:c25:c4bb:a5ff
1672c19:dd:d9:dd:c25:c25:c4bb:a600/1202c19:dd:d9:dd:c25:c25:c4bb:a6ff
1682c19:dd:d9:dd:c25:c25:c4bb:a700/1202c19:dd:d9:dd:c25:c25:c4bb:a7ff
1692c19:dd:d9:dd:c25:c25:c4bb:a800/1202c19:dd:d9:dd:c25:c25:c4bb:a8ff
1702c19:dd:d9:dd:c25:c25:c4bb:a900/1202c19:dd:d9:dd:c25:c25:c4bb:a9ff
1712c19:dd:d9:dd:c25:c25:c4bb:aa00/1202c19:dd:d9:dd:c25:c25:c4bb:aaff
1722c19:dd:d9:dd:c25:c25:c4bb:ab00/1202c19:dd:d9:dd:c25:c25:c4bb:abff
1732c19:dd:d9:dd:c25:c25:c4bb:ac00/1202c19:dd:d9:dd:c25:c25:c4bb:acff
1742c19:dd:d9:dd:c25:c25:c4bb:ad00/1202c19:dd:d9:dd:c25:c25:c4bb:adff
1752c19:dd:d9:dd:c25:c25:c4bb:ae00/1202c19:dd:d9:dd:c25:c25:c4bb:aeff
1762c19:dd:d9:dd:c25:c25:c4bb:af00/1202c19:dd:d9:dd:c25:c25:c4bb:afff
1772c19:dd:d9:dd:c25:c25:c4bb:b000/1202c19:dd:d9:dd:c25:c25:c4bb:b0ff
1782c19:dd:d9:dd:c25:c25:c4bb:b100/1202c19:dd:d9:dd:c25:c25:c4bb:b1ff
1792c19:dd:d9:dd:c25:c25:c4bb:b200/1202c19:dd:d9:dd:c25:c25:c4bb:b2ff
1802c19:dd:d9:dd:c25:c25:c4bb:b300/1202c19:dd:d9:dd:c25:c25:c4bb:b3ff
1812c19:dd:d9:dd:c25:c25:c4bb:b400/1202c19:dd:d9:dd:c25:c25:c4bb:b4ff
1822c19:dd:d9:dd:c25:c25:c4bb:b500/1202c19:dd:d9:dd:c25:c25:c4bb:b5ff
1832c19:dd:d9:dd:c25:c25:c4bb:b600/1202c19:dd:d9:dd:c25:c25:c4bb:b6ff
1842c19:dd:d9:dd:c25:c25:c4bb:b700/1202c19:dd:d9:dd:c25:c25:c4bb:b7ff
1852c19:dd:d9:dd:c25:c25:c4bb:b800/1202c19:dd:d9:dd:c25:c25:c4bb:b8ff
1862c19:dd:d9:dd:c25:c25:c4bb:b900/1202c19:dd:d9:dd:c25:c25:c4bb:b9ff
1872c19:dd:d9:dd:c25:c25:c4bb:ba00/1202c19:dd:d9:dd:c25:c25:c4bb:baff
1882c19:dd:d9:dd:c25:c25:c4bb:bb00/1202c19:dd:d9:dd:c25:c25:c4bb:bbff
1892c19:dd:d9:dd:c25:c25:c4bb:bc00/1202c19:dd:d9:dd:c25:c25:c4bb:bcff
1902c19:dd:d9:dd:c25:c25:c4bb:bd00/1202c19:dd:d9:dd:c25:c25:c4bb:bdff
1912c19:dd:d9:dd:c25:c25:c4bb:be00/1202c19:dd:d9:dd:c25:c25:c4bb:beff
1922c19:dd:d9:dd:c25:c25:c4bb:bf00/1202c19:dd:d9:dd:c25:c25:c4bb:bfff
1932c19:dd:d9:dd:c25:c25:c4bb:c000/1202c19:dd:d9:dd:c25:c25:c4bb:c0ff
1942c19:dd:d9:dd:c25:c25:c4bb:c100/1202c19:dd:d9:dd:c25:c25:c4bb:c1ff
1952c19:dd:d9:dd:c25:c25:c4bb:c200/1202c19:dd:d9:dd:c25:c25:c4bb:c2ff
1962c19:dd:d9:dd:c25:c25:c4bb:c300/1202c19:dd:d9:dd:c25:c25:c4bb:c3ff
1972c19:dd:d9:dd:c25:c25:c4bb:c400/1202c19:dd:d9:dd:c25:c25:c4bb:c4ff
1982c19:dd:d9:dd:c25:c25:c4bb:c500/1202c19:dd:d9:dd:c25:c25:c4bb:c5ff
1992c19:dd:d9:dd:c25:c25:c4bb:c600/1202c19:dd:d9:dd:c25:c25:c4bb:c6ff
2002c19:dd:d9:dd:c25:c25:c4bb:c700/1202c19:dd:d9:dd:c25:c25:c4bb:c7ff
2012c19:dd:d9:dd:c25:c25:c4bb:c800/1202c19:dd:d9:dd:c25:c25:c4bb:c8ff
2022c19:dd:d9:dd:c25:c25:c4bb:c900/1202c19:dd:d9:dd:c25:c25:c4bb:c9ff
2032c19:dd:d9:dd:c25:c25:c4bb:ca00/1202c19:dd:d9:dd:c25:c25:c4bb:caff
2042c19:dd:d9:dd:c25:c25:c4bb:cb00/1202c19:dd:d9:dd:c25:c25:c4bb:cbff
2052c19:dd:d9:dd:c25:c25:c4bb:cc00/1202c19:dd:d9:dd:c25:c25:c4bb:ccff
2062c19:dd:d9:dd:c25:c25:c4bb:cd00/1202c19:dd:d9:dd:c25:c25:c4bb:cdff
2072c19:dd:d9:dd:c25:c25:c4bb:ce00/1202c19:dd:d9:dd:c25:c25:c4bb:ceff
2082c19:dd:d9:dd:c25:c25:c4bb:cf00/1202c19:dd:d9:dd:c25:c25:c4bb:cfff
2092c19:dd:d9:dd:c25:c25:c4bb:d000/1202c19:dd:d9:dd:c25:c25:c4bb:d0ff
2102c19:dd:d9:dd:c25:c25:c4bb:d100/1202c19:dd:d9:dd:c25:c25:c4bb:d1ff
2112c19:dd:d9:dd:c25:c25:c4bb:d200/1202c19:dd:d9:dd:c25:c25:c4bb:d2ff
2122c19:dd:d9:dd:c25:c25:c4bb:d300/1202c19:dd:d9:dd:c25:c25:c4bb:d3ff
2132c19:dd:d9:dd:c25:c25:c4bb:d400/1202c19:dd:d9:dd:c25:c25:c4bb:d4ff
2142c19:dd:d9:dd:c25:c25:c4bb:d500/1202c19:dd:d9:dd:c25:c25:c4bb:d5ff
2152c19:dd:d9:dd:c25:c25:c4bb:d600/1202c19:dd:d9:dd:c25:c25:c4bb:d6ff
2162c19:dd:d9:dd:c25:c25:c4bb:d700/1202c19:dd:d9:dd:c25:c25:c4bb:d7ff
2172c19:dd:d9:dd:c25:c25:c4bb:d800/1202c19:dd:d9:dd:c25:c25:c4bb:d8ff
2182c19:dd:d9:dd:c25:c25:c4bb:d900/1202c19:dd:d9:dd:c25:c25:c4bb:d9ff
2192c19:dd:d9:dd:c25:c25:c4bb:da00/1202c19:dd:d9:dd:c25:c25:c4bb:daff
2202c19:dd:d9:dd:c25:c25:c4bb:db00/1202c19:dd:d9:dd:c25:c25:c4bb:dbff
2212c19:dd:d9:dd:c25:c25:c4bb:dc00/1202c19:dd:d9:dd:c25:c25:c4bb:dcff
2222c19:dd:d9:dd:c25:c25:c4bb:dd00/1202c19:dd:d9:dd:c25:c25:c4bb:ddff
2232c19:dd:d9:dd:c25:c25:c4bb:de00/1202c19:dd:d9:dd:c25:c25:c4bb:deff
2242c19:dd:d9:dd:c25:c25:c4bb:df00/1202c19:dd:d9:dd:c25:c25:c4bb:dfff
2252c19:dd:d9:dd:c25:c25:c4bb:e000/1202c19:dd:d9:dd:c25:c25:c4bb:e0ff
2262c19:dd:d9:dd:c25:c25:c4bb:e100/1202c19:dd:d9:dd:c25:c25:c4bb:e1ff
2272c19:dd:d9:dd:c25:c25:c4bb:e200/1202c19:dd:d9:dd:c25:c25:c4bb:e2ff
2282c19:dd:d9:dd:c25:c25:c4bb:e300/1202c19:dd:d9:dd:c25:c25:c4bb:e3ff
2292c19:dd:d9:dd:c25:c25:c4bb:e400/1202c19:dd:d9:dd:c25:c25:c4bb:e4ff
2302c19:dd:d9:dd:c25:c25:c4bb:e500/1202c19:dd:d9:dd:c25:c25:c4bb:e5ff
2312c19:dd:d9:dd:c25:c25:c4bb:e600/1202c19:dd:d9:dd:c25:c25:c4bb:e6ff
2322c19:dd:d9:dd:c25:c25:c4bb:e700/1202c19:dd:d9:dd:c25:c25:c4bb:e7ff
2332c19:dd:d9:dd:c25:c25:c4bb:e800/1202c19:dd:d9:dd:c25:c25:c4bb:e8ff
2342c19:dd:d9:dd:c25:c25:c4bb:e900/1202c19:dd:d9:dd:c25:c25:c4bb:e9ff
2352c19:dd:d9:dd:c25:c25:c4bb:ea00/1202c19:dd:d9:dd:c25:c25:c4bb:eaff
2362c19:dd:d9:dd:c25:c25:c4bb:eb00/1202c19:dd:d9:dd:c25:c25:c4bb:ebff
2372c19:dd:d9:dd:c25:c25:c4bb:ec00/1202c19:dd:d9:dd:c25:c25:c4bb:ecff
2382c19:dd:d9:dd:c25:c25:c4bb:ed00/1202c19:dd:d9:dd:c25:c25:c4bb:edff
2392c19:dd:d9:dd:c25:c25:c4bb:ee00/1202c19:dd:d9:dd:c25:c25:c4bb:eeff
2402c19:dd:d9:dd:c25:c25:c4bb:ef00/1202c19:dd:d9:dd:c25:c25:c4bb:efff
2412c19:dd:d9:dd:c25:c25:c4bb:f000/1202c19:dd:d9:dd:c25:c25:c4bb:f0ff
2422c19:dd:d9:dd:c25:c25:c4bb:f100/1202c19:dd:d9:dd:c25:c25:c4bb:f1ff
2432c19:dd:d9:dd:c25:c25:c4bb:f200/1202c19:dd:d9:dd:c25:c25:c4bb:f2ff
2442c19:dd:d9:dd:c25:c25:c4bb:f300/1202c19:dd:d9:dd:c25:c25:c4bb:f3ff
2452c19:dd:d9:dd:c25:c25:c4bb:f400/1202c19:dd:d9:dd:c25:c25:c4bb:f4ff
2462c19:dd:d9:dd:c25:c25:c4bb:f500/1202c19:dd:d9:dd:c25:c25:c4bb:f5ff
2472c19:dd:d9:dd:c25:c25:c4bb:f600/1202c19:dd:d9:dd:c25:c25:c4bb:f6ff
2482c19:dd:d9:dd:c25:c25:c4bb:f700/1202c19:dd:d9:dd:c25:c25:c4bb:f7ff
2492c19:dd:d9:dd:c25:c25:c4bb:f800/1202c19:dd:d9:dd:c25:c25:c4bb:f8ff
2502c19:dd:d9:dd:c25:c25:c4bb:f900/1202c19:dd:d9:dd:c25:c25:c4bb:f9ff
2512c19:dd:d9:dd:c25:c25:c4bb:fa00/1202c19:dd:d9:dd:c25:c25:c4bb:faff
2522c19:dd:d9:dd:c25:c25:c4bb:fb00/1202c19:dd:d9:dd:c25:c25:c4bb:fbff
2532c19:dd:d9:dd:c25:c25:c4bb:fc00/1202c19:dd:d9:dd:c25:c25:c4bb:fcff
2542c19:dd:d9:dd:c25:c25:c4bb:fd00/1202c19:dd:d9:dd:c25:c25:c4bb:fdff
2552c19:dd:d9:dd:c25:c25:c4bb:fe00/1202c19:dd:d9:dd:c25:c25:c4bb:feff
2562c19:dd:d9:dd:c25:c25:c4bb:ff00/1202c19:dd:d9:dd:c25:c25:c4bb: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.