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:ddc:c00a:f00a:c00a:30ec:0/112
First address
2c19:dd:ddc:c00a:f00a:c00a:30ec:0
Last address
2c19:dd:ddc:c00a:f00a:c00a:30ec:ffff
Addresses
65,536
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
2c19:00dd:0ddc:c00a:f00a:c00a:30ec:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
c.e.0.3.a.0.0.c.a.0.0.f.a.0.0.c.c.d.d.0.d.d.0.0.9.1.c.2.ip6.arpa
Split into smaller subnets/124
/113 (2)/114 (4)/115 (8)/116 (16)/120 (256)/124 (4,096)/127 (32,768)/128 (65,536)

2c19:dd:ddc:c00a:f00a:c00a:30ec:0/112 makes 4,096 subnets of /124; the first 256 are listed.

Subnets
#SubnetLast address
12c19:dd:ddc:c00a:f00a:c00a:30ec:0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:f
22c19:dd:ddc:c00a:f00a:c00a:30ec:10/1242c19:dd:ddc:c00a:f00a:c00a:30ec:1f
32c19:dd:ddc:c00a:f00a:c00a:30ec:20/1242c19:dd:ddc:c00a:f00a:c00a:30ec:2f
42c19:dd:ddc:c00a:f00a:c00a:30ec:30/1242c19:dd:ddc:c00a:f00a:c00a:30ec:3f
52c19:dd:ddc:c00a:f00a:c00a:30ec:40/1242c19:dd:ddc:c00a:f00a:c00a:30ec:4f
62c19:dd:ddc:c00a:f00a:c00a:30ec:50/1242c19:dd:ddc:c00a:f00a:c00a:30ec:5f
72c19:dd:ddc:c00a:f00a:c00a:30ec:60/1242c19:dd:ddc:c00a:f00a:c00a:30ec:6f
82c19:dd:ddc:c00a:f00a:c00a:30ec:70/1242c19:dd:ddc:c00a:f00a:c00a:30ec:7f
92c19:dd:ddc:c00a:f00a:c00a:30ec:80/1242c19:dd:ddc:c00a:f00a:c00a:30ec:8f
102c19:dd:ddc:c00a:f00a:c00a:30ec:90/1242c19:dd:ddc:c00a:f00a:c00a:30ec:9f
112c19:dd:ddc:c00a:f00a:c00a:30ec:a0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:af
122c19:dd:ddc:c00a:f00a:c00a:30ec:b0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:bf
132c19:dd:ddc:c00a:f00a:c00a:30ec:c0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:cf
142c19:dd:ddc:c00a:f00a:c00a:30ec:d0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:df
152c19:dd:ddc:c00a:f00a:c00a:30ec:e0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:ef
162c19:dd:ddc:c00a:f00a:c00a:30ec:f0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:ff
172c19:dd:ddc:c00a:f00a:c00a:30ec:100/1242c19:dd:ddc:c00a:f00a:c00a:30ec:10f
182c19:dd:ddc:c00a:f00a:c00a:30ec:110/1242c19:dd:ddc:c00a:f00a:c00a:30ec:11f
192c19:dd:ddc:c00a:f00a:c00a:30ec:120/1242c19:dd:ddc:c00a:f00a:c00a:30ec:12f
202c19:dd:ddc:c00a:f00a:c00a:30ec:130/1242c19:dd:ddc:c00a:f00a:c00a:30ec:13f
212c19:dd:ddc:c00a:f00a:c00a:30ec:140/1242c19:dd:ddc:c00a:f00a:c00a:30ec:14f
222c19:dd:ddc:c00a:f00a:c00a:30ec:150/1242c19:dd:ddc:c00a:f00a:c00a:30ec:15f
232c19:dd:ddc:c00a:f00a:c00a:30ec:160/1242c19:dd:ddc:c00a:f00a:c00a:30ec:16f
242c19:dd:ddc:c00a:f00a:c00a:30ec:170/1242c19:dd:ddc:c00a:f00a:c00a:30ec:17f
252c19:dd:ddc:c00a:f00a:c00a:30ec:180/1242c19:dd:ddc:c00a:f00a:c00a:30ec:18f
262c19:dd:ddc:c00a:f00a:c00a:30ec:190/1242c19:dd:ddc:c00a:f00a:c00a:30ec:19f
272c19:dd:ddc:c00a:f00a:c00a:30ec:1a0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:1af
282c19:dd:ddc:c00a:f00a:c00a:30ec:1b0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:1bf
292c19:dd:ddc:c00a:f00a:c00a:30ec:1c0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:1cf
302c19:dd:ddc:c00a:f00a:c00a:30ec:1d0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:1df
312c19:dd:ddc:c00a:f00a:c00a:30ec:1e0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:1ef
322c19:dd:ddc:c00a:f00a:c00a:30ec:1f0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:1ff
332c19:dd:ddc:c00a:f00a:c00a:30ec:200/1242c19:dd:ddc:c00a:f00a:c00a:30ec:20f
342c19:dd:ddc:c00a:f00a:c00a:30ec:210/1242c19:dd:ddc:c00a:f00a:c00a:30ec:21f
352c19:dd:ddc:c00a:f00a:c00a:30ec:220/1242c19:dd:ddc:c00a:f00a:c00a:30ec:22f
362c19:dd:ddc:c00a:f00a:c00a:30ec:230/1242c19:dd:ddc:c00a:f00a:c00a:30ec:23f
372c19:dd:ddc:c00a:f00a:c00a:30ec:240/1242c19:dd:ddc:c00a:f00a:c00a:30ec:24f
382c19:dd:ddc:c00a:f00a:c00a:30ec:250/1242c19:dd:ddc:c00a:f00a:c00a:30ec:25f
392c19:dd:ddc:c00a:f00a:c00a:30ec:260/1242c19:dd:ddc:c00a:f00a:c00a:30ec:26f
402c19:dd:ddc:c00a:f00a:c00a:30ec:270/1242c19:dd:ddc:c00a:f00a:c00a:30ec:27f
412c19:dd:ddc:c00a:f00a:c00a:30ec:280/1242c19:dd:ddc:c00a:f00a:c00a:30ec:28f
422c19:dd:ddc:c00a:f00a:c00a:30ec:290/1242c19:dd:ddc:c00a:f00a:c00a:30ec:29f
432c19:dd:ddc:c00a:f00a:c00a:30ec:2a0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:2af
442c19:dd:ddc:c00a:f00a:c00a:30ec:2b0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:2bf
452c19:dd:ddc:c00a:f00a:c00a:30ec:2c0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:2cf
462c19:dd:ddc:c00a:f00a:c00a:30ec:2d0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:2df
472c19:dd:ddc:c00a:f00a:c00a:30ec:2e0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:2ef
482c19:dd:ddc:c00a:f00a:c00a:30ec:2f0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:2ff
492c19:dd:ddc:c00a:f00a:c00a:30ec:300/1242c19:dd:ddc:c00a:f00a:c00a:30ec:30f
502c19:dd:ddc:c00a:f00a:c00a:30ec:310/1242c19:dd:ddc:c00a:f00a:c00a:30ec:31f
512c19:dd:ddc:c00a:f00a:c00a:30ec:320/1242c19:dd:ddc:c00a:f00a:c00a:30ec:32f
522c19:dd:ddc:c00a:f00a:c00a:30ec:330/1242c19:dd:ddc:c00a:f00a:c00a:30ec:33f
532c19:dd:ddc:c00a:f00a:c00a:30ec:340/1242c19:dd:ddc:c00a:f00a:c00a:30ec:34f
542c19:dd:ddc:c00a:f00a:c00a:30ec:350/1242c19:dd:ddc:c00a:f00a:c00a:30ec:35f
552c19:dd:ddc:c00a:f00a:c00a:30ec:360/1242c19:dd:ddc:c00a:f00a:c00a:30ec:36f
562c19:dd:ddc:c00a:f00a:c00a:30ec:370/1242c19:dd:ddc:c00a:f00a:c00a:30ec:37f
572c19:dd:ddc:c00a:f00a:c00a:30ec:380/1242c19:dd:ddc:c00a:f00a:c00a:30ec:38f
582c19:dd:ddc:c00a:f00a:c00a:30ec:390/1242c19:dd:ddc:c00a:f00a:c00a:30ec:39f
592c19:dd:ddc:c00a:f00a:c00a:30ec:3a0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:3af
602c19:dd:ddc:c00a:f00a:c00a:30ec:3b0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:3bf
612c19:dd:ddc:c00a:f00a:c00a:30ec:3c0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:3cf
622c19:dd:ddc:c00a:f00a:c00a:30ec:3d0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:3df
632c19:dd:ddc:c00a:f00a:c00a:30ec:3e0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:3ef
642c19:dd:ddc:c00a:f00a:c00a:30ec:3f0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:3ff
652c19:dd:ddc:c00a:f00a:c00a:30ec:400/1242c19:dd:ddc:c00a:f00a:c00a:30ec:40f
662c19:dd:ddc:c00a:f00a:c00a:30ec:410/1242c19:dd:ddc:c00a:f00a:c00a:30ec:41f
672c19:dd:ddc:c00a:f00a:c00a:30ec:420/1242c19:dd:ddc:c00a:f00a:c00a:30ec:42f
682c19:dd:ddc:c00a:f00a:c00a:30ec:430/1242c19:dd:ddc:c00a:f00a:c00a:30ec:43f
692c19:dd:ddc:c00a:f00a:c00a:30ec:440/1242c19:dd:ddc:c00a:f00a:c00a:30ec:44f
702c19:dd:ddc:c00a:f00a:c00a:30ec:450/1242c19:dd:ddc:c00a:f00a:c00a:30ec:45f
712c19:dd:ddc:c00a:f00a:c00a:30ec:460/1242c19:dd:ddc:c00a:f00a:c00a:30ec:46f
722c19:dd:ddc:c00a:f00a:c00a:30ec:470/1242c19:dd:ddc:c00a:f00a:c00a:30ec:47f
732c19:dd:ddc:c00a:f00a:c00a:30ec:480/1242c19:dd:ddc:c00a:f00a:c00a:30ec:48f
742c19:dd:ddc:c00a:f00a:c00a:30ec:490/1242c19:dd:ddc:c00a:f00a:c00a:30ec:49f
752c19:dd:ddc:c00a:f00a:c00a:30ec:4a0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:4af
762c19:dd:ddc:c00a:f00a:c00a:30ec:4b0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:4bf
772c19:dd:ddc:c00a:f00a:c00a:30ec:4c0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:4cf
782c19:dd:ddc:c00a:f00a:c00a:30ec:4d0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:4df
792c19:dd:ddc:c00a:f00a:c00a:30ec:4e0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:4ef
802c19:dd:ddc:c00a:f00a:c00a:30ec:4f0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:4ff
812c19:dd:ddc:c00a:f00a:c00a:30ec:500/1242c19:dd:ddc:c00a:f00a:c00a:30ec:50f
822c19:dd:ddc:c00a:f00a:c00a:30ec:510/1242c19:dd:ddc:c00a:f00a:c00a:30ec:51f
832c19:dd:ddc:c00a:f00a:c00a:30ec:520/1242c19:dd:ddc:c00a:f00a:c00a:30ec:52f
842c19:dd:ddc:c00a:f00a:c00a:30ec:530/1242c19:dd:ddc:c00a:f00a:c00a:30ec:53f
852c19:dd:ddc:c00a:f00a:c00a:30ec:540/1242c19:dd:ddc:c00a:f00a:c00a:30ec:54f
862c19:dd:ddc:c00a:f00a:c00a:30ec:550/1242c19:dd:ddc:c00a:f00a:c00a:30ec:55f
872c19:dd:ddc:c00a:f00a:c00a:30ec:560/1242c19:dd:ddc:c00a:f00a:c00a:30ec:56f
882c19:dd:ddc:c00a:f00a:c00a:30ec:570/1242c19:dd:ddc:c00a:f00a:c00a:30ec:57f
892c19:dd:ddc:c00a:f00a:c00a:30ec:580/1242c19:dd:ddc:c00a:f00a:c00a:30ec:58f
902c19:dd:ddc:c00a:f00a:c00a:30ec:590/1242c19:dd:ddc:c00a:f00a:c00a:30ec:59f
912c19:dd:ddc:c00a:f00a:c00a:30ec:5a0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:5af
922c19:dd:ddc:c00a:f00a:c00a:30ec:5b0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:5bf
932c19:dd:ddc:c00a:f00a:c00a:30ec:5c0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:5cf
942c19:dd:ddc:c00a:f00a:c00a:30ec:5d0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:5df
952c19:dd:ddc:c00a:f00a:c00a:30ec:5e0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:5ef
962c19:dd:ddc:c00a:f00a:c00a:30ec:5f0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:5ff
972c19:dd:ddc:c00a:f00a:c00a:30ec:600/1242c19:dd:ddc:c00a:f00a:c00a:30ec:60f
982c19:dd:ddc:c00a:f00a:c00a:30ec:610/1242c19:dd:ddc:c00a:f00a:c00a:30ec:61f
992c19:dd:ddc:c00a:f00a:c00a:30ec:620/1242c19:dd:ddc:c00a:f00a:c00a:30ec:62f
1002c19:dd:ddc:c00a:f00a:c00a:30ec:630/1242c19:dd:ddc:c00a:f00a:c00a:30ec:63f
1012c19:dd:ddc:c00a:f00a:c00a:30ec:640/1242c19:dd:ddc:c00a:f00a:c00a:30ec:64f
1022c19:dd:ddc:c00a:f00a:c00a:30ec:650/1242c19:dd:ddc:c00a:f00a:c00a:30ec:65f
1032c19:dd:ddc:c00a:f00a:c00a:30ec:660/1242c19:dd:ddc:c00a:f00a:c00a:30ec:66f
1042c19:dd:ddc:c00a:f00a:c00a:30ec:670/1242c19:dd:ddc:c00a:f00a:c00a:30ec:67f
1052c19:dd:ddc:c00a:f00a:c00a:30ec:680/1242c19:dd:ddc:c00a:f00a:c00a:30ec:68f
1062c19:dd:ddc:c00a:f00a:c00a:30ec:690/1242c19:dd:ddc:c00a:f00a:c00a:30ec:69f
1072c19:dd:ddc:c00a:f00a:c00a:30ec:6a0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:6af
1082c19:dd:ddc:c00a:f00a:c00a:30ec:6b0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:6bf
1092c19:dd:ddc:c00a:f00a:c00a:30ec:6c0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:6cf
1102c19:dd:ddc:c00a:f00a:c00a:30ec:6d0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:6df
1112c19:dd:ddc:c00a:f00a:c00a:30ec:6e0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:6ef
1122c19:dd:ddc:c00a:f00a:c00a:30ec:6f0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:6ff
1132c19:dd:ddc:c00a:f00a:c00a:30ec:700/1242c19:dd:ddc:c00a:f00a:c00a:30ec:70f
1142c19:dd:ddc:c00a:f00a:c00a:30ec:710/1242c19:dd:ddc:c00a:f00a:c00a:30ec:71f
1152c19:dd:ddc:c00a:f00a:c00a:30ec:720/1242c19:dd:ddc:c00a:f00a:c00a:30ec:72f
1162c19:dd:ddc:c00a:f00a:c00a:30ec:730/1242c19:dd:ddc:c00a:f00a:c00a:30ec:73f
1172c19:dd:ddc:c00a:f00a:c00a:30ec:740/1242c19:dd:ddc:c00a:f00a:c00a:30ec:74f
1182c19:dd:ddc:c00a:f00a:c00a:30ec:750/1242c19:dd:ddc:c00a:f00a:c00a:30ec:75f
1192c19:dd:ddc:c00a:f00a:c00a:30ec:760/1242c19:dd:ddc:c00a:f00a:c00a:30ec:76f
1202c19:dd:ddc:c00a:f00a:c00a:30ec:770/1242c19:dd:ddc:c00a:f00a:c00a:30ec:77f
1212c19:dd:ddc:c00a:f00a:c00a:30ec:780/1242c19:dd:ddc:c00a:f00a:c00a:30ec:78f
1222c19:dd:ddc:c00a:f00a:c00a:30ec:790/1242c19:dd:ddc:c00a:f00a:c00a:30ec:79f
1232c19:dd:ddc:c00a:f00a:c00a:30ec:7a0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:7af
1242c19:dd:ddc:c00a:f00a:c00a:30ec:7b0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:7bf
1252c19:dd:ddc:c00a:f00a:c00a:30ec:7c0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:7cf
1262c19:dd:ddc:c00a:f00a:c00a:30ec:7d0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:7df
1272c19:dd:ddc:c00a:f00a:c00a:30ec:7e0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:7ef
1282c19:dd:ddc:c00a:f00a:c00a:30ec:7f0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:7ff
1292c19:dd:ddc:c00a:f00a:c00a:30ec:800/1242c19:dd:ddc:c00a:f00a:c00a:30ec:80f
1302c19:dd:ddc:c00a:f00a:c00a:30ec:810/1242c19:dd:ddc:c00a:f00a:c00a:30ec:81f
1312c19:dd:ddc:c00a:f00a:c00a:30ec:820/1242c19:dd:ddc:c00a:f00a:c00a:30ec:82f
1322c19:dd:ddc:c00a:f00a:c00a:30ec:830/1242c19:dd:ddc:c00a:f00a:c00a:30ec:83f
1332c19:dd:ddc:c00a:f00a:c00a:30ec:840/1242c19:dd:ddc:c00a:f00a:c00a:30ec:84f
1342c19:dd:ddc:c00a:f00a:c00a:30ec:850/1242c19:dd:ddc:c00a:f00a:c00a:30ec:85f
1352c19:dd:ddc:c00a:f00a:c00a:30ec:860/1242c19:dd:ddc:c00a:f00a:c00a:30ec:86f
1362c19:dd:ddc:c00a:f00a:c00a:30ec:870/1242c19:dd:ddc:c00a:f00a:c00a:30ec:87f
1372c19:dd:ddc:c00a:f00a:c00a:30ec:880/1242c19:dd:ddc:c00a:f00a:c00a:30ec:88f
1382c19:dd:ddc:c00a:f00a:c00a:30ec:890/1242c19:dd:ddc:c00a:f00a:c00a:30ec:89f
1392c19:dd:ddc:c00a:f00a:c00a:30ec:8a0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:8af
1402c19:dd:ddc:c00a:f00a:c00a:30ec:8b0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:8bf
1412c19:dd:ddc:c00a:f00a:c00a:30ec:8c0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:8cf
1422c19:dd:ddc:c00a:f00a:c00a:30ec:8d0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:8df
1432c19:dd:ddc:c00a:f00a:c00a:30ec:8e0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:8ef
1442c19:dd:ddc:c00a:f00a:c00a:30ec:8f0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:8ff
1452c19:dd:ddc:c00a:f00a:c00a:30ec:900/1242c19:dd:ddc:c00a:f00a:c00a:30ec:90f
1462c19:dd:ddc:c00a:f00a:c00a:30ec:910/1242c19:dd:ddc:c00a:f00a:c00a:30ec:91f
1472c19:dd:ddc:c00a:f00a:c00a:30ec:920/1242c19:dd:ddc:c00a:f00a:c00a:30ec:92f
1482c19:dd:ddc:c00a:f00a:c00a:30ec:930/1242c19:dd:ddc:c00a:f00a:c00a:30ec:93f
1492c19:dd:ddc:c00a:f00a:c00a:30ec:940/1242c19:dd:ddc:c00a:f00a:c00a:30ec:94f
1502c19:dd:ddc:c00a:f00a:c00a:30ec:950/1242c19:dd:ddc:c00a:f00a:c00a:30ec:95f
1512c19:dd:ddc:c00a:f00a:c00a:30ec:960/1242c19:dd:ddc:c00a:f00a:c00a:30ec:96f
1522c19:dd:ddc:c00a:f00a:c00a:30ec:970/1242c19:dd:ddc:c00a:f00a:c00a:30ec:97f
1532c19:dd:ddc:c00a:f00a:c00a:30ec:980/1242c19:dd:ddc:c00a:f00a:c00a:30ec:98f
1542c19:dd:ddc:c00a:f00a:c00a:30ec:990/1242c19:dd:ddc:c00a:f00a:c00a:30ec:99f
1552c19:dd:ddc:c00a:f00a:c00a:30ec:9a0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:9af
1562c19:dd:ddc:c00a:f00a:c00a:30ec:9b0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:9bf
1572c19:dd:ddc:c00a:f00a:c00a:30ec:9c0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:9cf
1582c19:dd:ddc:c00a:f00a:c00a:30ec:9d0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:9df
1592c19:dd:ddc:c00a:f00a:c00a:30ec:9e0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:9ef
1602c19:dd:ddc:c00a:f00a:c00a:30ec:9f0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:9ff
1612c19:dd:ddc:c00a:f00a:c00a:30ec:a00/1242c19:dd:ddc:c00a:f00a:c00a:30ec:a0f
1622c19:dd:ddc:c00a:f00a:c00a:30ec:a10/1242c19:dd:ddc:c00a:f00a:c00a:30ec:a1f
1632c19:dd:ddc:c00a:f00a:c00a:30ec:a20/1242c19:dd:ddc:c00a:f00a:c00a:30ec:a2f
1642c19:dd:ddc:c00a:f00a:c00a:30ec:a30/1242c19:dd:ddc:c00a:f00a:c00a:30ec:a3f
1652c19:dd:ddc:c00a:f00a:c00a:30ec:a40/1242c19:dd:ddc:c00a:f00a:c00a:30ec:a4f
1662c19:dd:ddc:c00a:f00a:c00a:30ec:a50/1242c19:dd:ddc:c00a:f00a:c00a:30ec:a5f
1672c19:dd:ddc:c00a:f00a:c00a:30ec:a60/1242c19:dd:ddc:c00a:f00a:c00a:30ec:a6f
1682c19:dd:ddc:c00a:f00a:c00a:30ec:a70/1242c19:dd:ddc:c00a:f00a:c00a:30ec:a7f
1692c19:dd:ddc:c00a:f00a:c00a:30ec:a80/1242c19:dd:ddc:c00a:f00a:c00a:30ec:a8f
1702c19:dd:ddc:c00a:f00a:c00a:30ec:a90/1242c19:dd:ddc:c00a:f00a:c00a:30ec:a9f
1712c19:dd:ddc:c00a:f00a:c00a:30ec:aa0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:aaf
1722c19:dd:ddc:c00a:f00a:c00a:30ec:ab0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:abf
1732c19:dd:ddc:c00a:f00a:c00a:30ec:ac0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:acf
1742c19:dd:ddc:c00a:f00a:c00a:30ec:ad0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:adf
1752c19:dd:ddc:c00a:f00a:c00a:30ec:ae0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:aef
1762c19:dd:ddc:c00a:f00a:c00a:30ec:af0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:aff
1772c19:dd:ddc:c00a:f00a:c00a:30ec:b00/1242c19:dd:ddc:c00a:f00a:c00a:30ec:b0f
1782c19:dd:ddc:c00a:f00a:c00a:30ec:b10/1242c19:dd:ddc:c00a:f00a:c00a:30ec:b1f
1792c19:dd:ddc:c00a:f00a:c00a:30ec:b20/1242c19:dd:ddc:c00a:f00a:c00a:30ec:b2f
1802c19:dd:ddc:c00a:f00a:c00a:30ec:b30/1242c19:dd:ddc:c00a:f00a:c00a:30ec:b3f
1812c19:dd:ddc:c00a:f00a:c00a:30ec:b40/1242c19:dd:ddc:c00a:f00a:c00a:30ec:b4f
1822c19:dd:ddc:c00a:f00a:c00a:30ec:b50/1242c19:dd:ddc:c00a:f00a:c00a:30ec:b5f
1832c19:dd:ddc:c00a:f00a:c00a:30ec:b60/1242c19:dd:ddc:c00a:f00a:c00a:30ec:b6f
1842c19:dd:ddc:c00a:f00a:c00a:30ec:b70/1242c19:dd:ddc:c00a:f00a:c00a:30ec:b7f
1852c19:dd:ddc:c00a:f00a:c00a:30ec:b80/1242c19:dd:ddc:c00a:f00a:c00a:30ec:b8f
1862c19:dd:ddc:c00a:f00a:c00a:30ec:b90/1242c19:dd:ddc:c00a:f00a:c00a:30ec:b9f
1872c19:dd:ddc:c00a:f00a:c00a:30ec:ba0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:baf
1882c19:dd:ddc:c00a:f00a:c00a:30ec:bb0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:bbf
1892c19:dd:ddc:c00a:f00a:c00a:30ec:bc0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:bcf
1902c19:dd:ddc:c00a:f00a:c00a:30ec:bd0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:bdf
1912c19:dd:ddc:c00a:f00a:c00a:30ec:be0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:bef
1922c19:dd:ddc:c00a:f00a:c00a:30ec:bf0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:bff
1932c19:dd:ddc:c00a:f00a:c00a:30ec:c00/1242c19:dd:ddc:c00a:f00a:c00a:30ec:c0f
1942c19:dd:ddc:c00a:f00a:c00a:30ec:c10/1242c19:dd:ddc:c00a:f00a:c00a:30ec:c1f
1952c19:dd:ddc:c00a:f00a:c00a:30ec:c20/1242c19:dd:ddc:c00a:f00a:c00a:30ec:c2f
1962c19:dd:ddc:c00a:f00a:c00a:30ec:c30/1242c19:dd:ddc:c00a:f00a:c00a:30ec:c3f
1972c19:dd:ddc:c00a:f00a:c00a:30ec:c40/1242c19:dd:ddc:c00a:f00a:c00a:30ec:c4f
1982c19:dd:ddc:c00a:f00a:c00a:30ec:c50/1242c19:dd:ddc:c00a:f00a:c00a:30ec:c5f
1992c19:dd:ddc:c00a:f00a:c00a:30ec:c60/1242c19:dd:ddc:c00a:f00a:c00a:30ec:c6f
2002c19:dd:ddc:c00a:f00a:c00a:30ec:c70/1242c19:dd:ddc:c00a:f00a:c00a:30ec:c7f
2012c19:dd:ddc:c00a:f00a:c00a:30ec:c80/1242c19:dd:ddc:c00a:f00a:c00a:30ec:c8f
2022c19:dd:ddc:c00a:f00a:c00a:30ec:c90/1242c19:dd:ddc:c00a:f00a:c00a:30ec:c9f
2032c19:dd:ddc:c00a:f00a:c00a:30ec:ca0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:caf
2042c19:dd:ddc:c00a:f00a:c00a:30ec:cb0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:cbf
2052c19:dd:ddc:c00a:f00a:c00a:30ec:cc0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:ccf
2062c19:dd:ddc:c00a:f00a:c00a:30ec:cd0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:cdf
2072c19:dd:ddc:c00a:f00a:c00a:30ec:ce0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:cef
2082c19:dd:ddc:c00a:f00a:c00a:30ec:cf0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:cff
2092c19:dd:ddc:c00a:f00a:c00a:30ec:d00/1242c19:dd:ddc:c00a:f00a:c00a:30ec:d0f
2102c19:dd:ddc:c00a:f00a:c00a:30ec:d10/1242c19:dd:ddc:c00a:f00a:c00a:30ec:d1f
2112c19:dd:ddc:c00a:f00a:c00a:30ec:d20/1242c19:dd:ddc:c00a:f00a:c00a:30ec:d2f
2122c19:dd:ddc:c00a:f00a:c00a:30ec:d30/1242c19:dd:ddc:c00a:f00a:c00a:30ec:d3f
2132c19:dd:ddc:c00a:f00a:c00a:30ec:d40/1242c19:dd:ddc:c00a:f00a:c00a:30ec:d4f
2142c19:dd:ddc:c00a:f00a:c00a:30ec:d50/1242c19:dd:ddc:c00a:f00a:c00a:30ec:d5f
2152c19:dd:ddc:c00a:f00a:c00a:30ec:d60/1242c19:dd:ddc:c00a:f00a:c00a:30ec:d6f
2162c19:dd:ddc:c00a:f00a:c00a:30ec:d70/1242c19:dd:ddc:c00a:f00a:c00a:30ec:d7f
2172c19:dd:ddc:c00a:f00a:c00a:30ec:d80/1242c19:dd:ddc:c00a:f00a:c00a:30ec:d8f
2182c19:dd:ddc:c00a:f00a:c00a:30ec:d90/1242c19:dd:ddc:c00a:f00a:c00a:30ec:d9f
2192c19:dd:ddc:c00a:f00a:c00a:30ec:da0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:daf
2202c19:dd:ddc:c00a:f00a:c00a:30ec:db0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:dbf
2212c19:dd:ddc:c00a:f00a:c00a:30ec:dc0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:dcf
2222c19:dd:ddc:c00a:f00a:c00a:30ec:dd0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:ddf
2232c19:dd:ddc:c00a:f00a:c00a:30ec:de0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:def
2242c19:dd:ddc:c00a:f00a:c00a:30ec:df0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:dff
2252c19:dd:ddc:c00a:f00a:c00a:30ec:e00/1242c19:dd:ddc:c00a:f00a:c00a:30ec:e0f
2262c19:dd:ddc:c00a:f00a:c00a:30ec:e10/1242c19:dd:ddc:c00a:f00a:c00a:30ec:e1f
2272c19:dd:ddc:c00a:f00a:c00a:30ec:e20/1242c19:dd:ddc:c00a:f00a:c00a:30ec:e2f
2282c19:dd:ddc:c00a:f00a:c00a:30ec:e30/1242c19:dd:ddc:c00a:f00a:c00a:30ec:e3f
2292c19:dd:ddc:c00a:f00a:c00a:30ec:e40/1242c19:dd:ddc:c00a:f00a:c00a:30ec:e4f
2302c19:dd:ddc:c00a:f00a:c00a:30ec:e50/1242c19:dd:ddc:c00a:f00a:c00a:30ec:e5f
2312c19:dd:ddc:c00a:f00a:c00a:30ec:e60/1242c19:dd:ddc:c00a:f00a:c00a:30ec:e6f
2322c19:dd:ddc:c00a:f00a:c00a:30ec:e70/1242c19:dd:ddc:c00a:f00a:c00a:30ec:e7f
2332c19:dd:ddc:c00a:f00a:c00a:30ec:e80/1242c19:dd:ddc:c00a:f00a:c00a:30ec:e8f
2342c19:dd:ddc:c00a:f00a:c00a:30ec:e90/1242c19:dd:ddc:c00a:f00a:c00a:30ec:e9f
2352c19:dd:ddc:c00a:f00a:c00a:30ec:ea0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:eaf
2362c19:dd:ddc:c00a:f00a:c00a:30ec:eb0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:ebf
2372c19:dd:ddc:c00a:f00a:c00a:30ec:ec0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:ecf
2382c19:dd:ddc:c00a:f00a:c00a:30ec:ed0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:edf
2392c19:dd:ddc:c00a:f00a:c00a:30ec:ee0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:eef
2402c19:dd:ddc:c00a:f00a:c00a:30ec:ef0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:eff
2412c19:dd:ddc:c00a:f00a:c00a:30ec:f00/1242c19:dd:ddc:c00a:f00a:c00a:30ec:f0f
2422c19:dd:ddc:c00a:f00a:c00a:30ec:f10/1242c19:dd:ddc:c00a:f00a:c00a:30ec:f1f
2432c19:dd:ddc:c00a:f00a:c00a:30ec:f20/1242c19:dd:ddc:c00a:f00a:c00a:30ec:f2f
2442c19:dd:ddc:c00a:f00a:c00a:30ec:f30/1242c19:dd:ddc:c00a:f00a:c00a:30ec:f3f
2452c19:dd:ddc:c00a:f00a:c00a:30ec:f40/1242c19:dd:ddc:c00a:f00a:c00a:30ec:f4f
2462c19:dd:ddc:c00a:f00a:c00a:30ec:f50/1242c19:dd:ddc:c00a:f00a:c00a:30ec:f5f
2472c19:dd:ddc:c00a:f00a:c00a:30ec:f60/1242c19:dd:ddc:c00a:f00a:c00a:30ec:f6f
2482c19:dd:ddc:c00a:f00a:c00a:30ec:f70/1242c19:dd:ddc:c00a:f00a:c00a:30ec:f7f
2492c19:dd:ddc:c00a:f00a:c00a:30ec:f80/1242c19:dd:ddc:c00a:f00a:c00a:30ec:f8f
2502c19:dd:ddc:c00a:f00a:c00a:30ec:f90/1242c19:dd:ddc:c00a:f00a:c00a:30ec:f9f
2512c19:dd:ddc:c00a:f00a:c00a:30ec:fa0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:faf
2522c19:dd:ddc:c00a:f00a:c00a:30ec:fb0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:fbf
2532c19:dd:ddc:c00a:f00a:c00a:30ec:fc0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:fcf
2542c19:dd:ddc:c00a:f00a:c00a:30ec:fd0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:fdf
2552c19:dd:ddc:c00a:f00a:c00a:30ec:fe0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:fef
2562c19:dd:ddc:c00a:f00a:c00a:30ec:ff0/1242c19:dd:ddc:c00a:f00a:c00a:30ec:fff

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.