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/116
Addresses4,096
/64 networksPart of one
Network
2c19:dd:d9:dd:c25:c25:b003:b000/116
First address
2c19:dd:d9:dd:c25:c25:b003:b000
Last address
2c19:dd:d9:dd:c25:c25:b003:bfff
Addresses
4,096
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
2c19:00dd:00d9:00dd:0c25:0c25:b003:b000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
b.3.0.0.b.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/124
/117 (2)/118 (4)/119 (8)/120 (16)/124 (256)/127 (2,048)/128 (4,096)

2c19:dd:d9:dd:c25:c25:b003:b000/116 makes 256 subnets of /124.

Subnets
#SubnetLast address
12c19:dd:d9:dd:c25:c25:b003:b000/1242c19:dd:d9:dd:c25:c25:b003:b00f
22c19:dd:d9:dd:c25:c25:b003:b010/1242c19:dd:d9:dd:c25:c25:b003:b01f
32c19:dd:d9:dd:c25:c25:b003:b020/1242c19:dd:d9:dd:c25:c25:b003:b02f
42c19:dd:d9:dd:c25:c25:b003:b030/1242c19:dd:d9:dd:c25:c25:b003:b03f
52c19:dd:d9:dd:c25:c25:b003:b040/1242c19:dd:d9:dd:c25:c25:b003:b04f
62c19:dd:d9:dd:c25:c25:b003:b050/1242c19:dd:d9:dd:c25:c25:b003:b05f
72c19:dd:d9:dd:c25:c25:b003:b060/1242c19:dd:d9:dd:c25:c25:b003:b06f
82c19:dd:d9:dd:c25:c25:b003:b070/1242c19:dd:d9:dd:c25:c25:b003:b07f
92c19:dd:d9:dd:c25:c25:b003:b080/1242c19:dd:d9:dd:c25:c25:b003:b08f
102c19:dd:d9:dd:c25:c25:b003:b090/1242c19:dd:d9:dd:c25:c25:b003:b09f
112c19:dd:d9:dd:c25:c25:b003:b0a0/1242c19:dd:d9:dd:c25:c25:b003:b0af
122c19:dd:d9:dd:c25:c25:b003:b0b0/1242c19:dd:d9:dd:c25:c25:b003:b0bf
132c19:dd:d9:dd:c25:c25:b003:b0c0/1242c19:dd:d9:dd:c25:c25:b003:b0cf
142c19:dd:d9:dd:c25:c25:b003:b0d0/1242c19:dd:d9:dd:c25:c25:b003:b0df
152c19:dd:d9:dd:c25:c25:b003:b0e0/1242c19:dd:d9:dd:c25:c25:b003:b0ef
162c19:dd:d9:dd:c25:c25:b003:b0f0/1242c19:dd:d9:dd:c25:c25:b003:b0ff
172c19:dd:d9:dd:c25:c25:b003:b100/1242c19:dd:d9:dd:c25:c25:b003:b10f
182c19:dd:d9:dd:c25:c25:b003:b110/1242c19:dd:d9:dd:c25:c25:b003:b11f
192c19:dd:d9:dd:c25:c25:b003:b120/1242c19:dd:d9:dd:c25:c25:b003:b12f
202c19:dd:d9:dd:c25:c25:b003:b130/1242c19:dd:d9:dd:c25:c25:b003:b13f
212c19:dd:d9:dd:c25:c25:b003:b140/1242c19:dd:d9:dd:c25:c25:b003:b14f
222c19:dd:d9:dd:c25:c25:b003:b150/1242c19:dd:d9:dd:c25:c25:b003:b15f
232c19:dd:d9:dd:c25:c25:b003:b160/1242c19:dd:d9:dd:c25:c25:b003:b16f
242c19:dd:d9:dd:c25:c25:b003:b170/1242c19:dd:d9:dd:c25:c25:b003:b17f
252c19:dd:d9:dd:c25:c25:b003:b180/1242c19:dd:d9:dd:c25:c25:b003:b18f
262c19:dd:d9:dd:c25:c25:b003:b190/1242c19:dd:d9:dd:c25:c25:b003:b19f
272c19:dd:d9:dd:c25:c25:b003:b1a0/1242c19:dd:d9:dd:c25:c25:b003:b1af
282c19:dd:d9:dd:c25:c25:b003:b1b0/1242c19:dd:d9:dd:c25:c25:b003:b1bf
292c19:dd:d9:dd:c25:c25:b003:b1c0/1242c19:dd:d9:dd:c25:c25:b003:b1cf
302c19:dd:d9:dd:c25:c25:b003:b1d0/1242c19:dd:d9:dd:c25:c25:b003:b1df
312c19:dd:d9:dd:c25:c25:b003:b1e0/1242c19:dd:d9:dd:c25:c25:b003:b1ef
322c19:dd:d9:dd:c25:c25:b003:b1f0/1242c19:dd:d9:dd:c25:c25:b003:b1ff
332c19:dd:d9:dd:c25:c25:b003:b200/1242c19:dd:d9:dd:c25:c25:b003:b20f
342c19:dd:d9:dd:c25:c25:b003:b210/1242c19:dd:d9:dd:c25:c25:b003:b21f
352c19:dd:d9:dd:c25:c25:b003:b220/1242c19:dd:d9:dd:c25:c25:b003:b22f
362c19:dd:d9:dd:c25:c25:b003:b230/1242c19:dd:d9:dd:c25:c25:b003:b23f
372c19:dd:d9:dd:c25:c25:b003:b240/1242c19:dd:d9:dd:c25:c25:b003:b24f
382c19:dd:d9:dd:c25:c25:b003:b250/1242c19:dd:d9:dd:c25:c25:b003:b25f
392c19:dd:d9:dd:c25:c25:b003:b260/1242c19:dd:d9:dd:c25:c25:b003:b26f
402c19:dd:d9:dd:c25:c25:b003:b270/1242c19:dd:d9:dd:c25:c25:b003:b27f
412c19:dd:d9:dd:c25:c25:b003:b280/1242c19:dd:d9:dd:c25:c25:b003:b28f
422c19:dd:d9:dd:c25:c25:b003:b290/1242c19:dd:d9:dd:c25:c25:b003:b29f
432c19:dd:d9:dd:c25:c25:b003:b2a0/1242c19:dd:d9:dd:c25:c25:b003:b2af
442c19:dd:d9:dd:c25:c25:b003:b2b0/1242c19:dd:d9:dd:c25:c25:b003:b2bf
452c19:dd:d9:dd:c25:c25:b003:b2c0/1242c19:dd:d9:dd:c25:c25:b003:b2cf
462c19:dd:d9:dd:c25:c25:b003:b2d0/1242c19:dd:d9:dd:c25:c25:b003:b2df
472c19:dd:d9:dd:c25:c25:b003:b2e0/1242c19:dd:d9:dd:c25:c25:b003:b2ef
482c19:dd:d9:dd:c25:c25:b003:b2f0/1242c19:dd:d9:dd:c25:c25:b003:b2ff
492c19:dd:d9:dd:c25:c25:b003:b300/1242c19:dd:d9:dd:c25:c25:b003:b30f
502c19:dd:d9:dd:c25:c25:b003:b310/1242c19:dd:d9:dd:c25:c25:b003:b31f
512c19:dd:d9:dd:c25:c25:b003:b320/1242c19:dd:d9:dd:c25:c25:b003:b32f
522c19:dd:d9:dd:c25:c25:b003:b330/1242c19:dd:d9:dd:c25:c25:b003:b33f
532c19:dd:d9:dd:c25:c25:b003:b340/1242c19:dd:d9:dd:c25:c25:b003:b34f
542c19:dd:d9:dd:c25:c25:b003:b350/1242c19:dd:d9:dd:c25:c25:b003:b35f
552c19:dd:d9:dd:c25:c25:b003:b360/1242c19:dd:d9:dd:c25:c25:b003:b36f
562c19:dd:d9:dd:c25:c25:b003:b370/1242c19:dd:d9:dd:c25:c25:b003:b37f
572c19:dd:d9:dd:c25:c25:b003:b380/1242c19:dd:d9:dd:c25:c25:b003:b38f
582c19:dd:d9:dd:c25:c25:b003:b390/1242c19:dd:d9:dd:c25:c25:b003:b39f
592c19:dd:d9:dd:c25:c25:b003:b3a0/1242c19:dd:d9:dd:c25:c25:b003:b3af
602c19:dd:d9:dd:c25:c25:b003:b3b0/1242c19:dd:d9:dd:c25:c25:b003:b3bf
612c19:dd:d9:dd:c25:c25:b003:b3c0/1242c19:dd:d9:dd:c25:c25:b003:b3cf
622c19:dd:d9:dd:c25:c25:b003:b3d0/1242c19:dd:d9:dd:c25:c25:b003:b3df
632c19:dd:d9:dd:c25:c25:b003:b3e0/1242c19:dd:d9:dd:c25:c25:b003:b3ef
642c19:dd:d9:dd:c25:c25:b003:b3f0/1242c19:dd:d9:dd:c25:c25:b003:b3ff
652c19:dd:d9:dd:c25:c25:b003:b400/1242c19:dd:d9:dd:c25:c25:b003:b40f
662c19:dd:d9:dd:c25:c25:b003:b410/1242c19:dd:d9:dd:c25:c25:b003:b41f
672c19:dd:d9:dd:c25:c25:b003:b420/1242c19:dd:d9:dd:c25:c25:b003:b42f
682c19:dd:d9:dd:c25:c25:b003:b430/1242c19:dd:d9:dd:c25:c25:b003:b43f
692c19:dd:d9:dd:c25:c25:b003:b440/1242c19:dd:d9:dd:c25:c25:b003:b44f
702c19:dd:d9:dd:c25:c25:b003:b450/1242c19:dd:d9:dd:c25:c25:b003:b45f
712c19:dd:d9:dd:c25:c25:b003:b460/1242c19:dd:d9:dd:c25:c25:b003:b46f
722c19:dd:d9:dd:c25:c25:b003:b470/1242c19:dd:d9:dd:c25:c25:b003:b47f
732c19:dd:d9:dd:c25:c25:b003:b480/1242c19:dd:d9:dd:c25:c25:b003:b48f
742c19:dd:d9:dd:c25:c25:b003:b490/1242c19:dd:d9:dd:c25:c25:b003:b49f
752c19:dd:d9:dd:c25:c25:b003:b4a0/1242c19:dd:d9:dd:c25:c25:b003:b4af
762c19:dd:d9:dd:c25:c25:b003:b4b0/1242c19:dd:d9:dd:c25:c25:b003:b4bf
772c19:dd:d9:dd:c25:c25:b003:b4c0/1242c19:dd:d9:dd:c25:c25:b003:b4cf
782c19:dd:d9:dd:c25:c25:b003:b4d0/1242c19:dd:d9:dd:c25:c25:b003:b4df
792c19:dd:d9:dd:c25:c25:b003:b4e0/1242c19:dd:d9:dd:c25:c25:b003:b4ef
802c19:dd:d9:dd:c25:c25:b003:b4f0/1242c19:dd:d9:dd:c25:c25:b003:b4ff
812c19:dd:d9:dd:c25:c25:b003:b500/1242c19:dd:d9:dd:c25:c25:b003:b50f
822c19:dd:d9:dd:c25:c25:b003:b510/1242c19:dd:d9:dd:c25:c25:b003:b51f
832c19:dd:d9:dd:c25:c25:b003:b520/1242c19:dd:d9:dd:c25:c25:b003:b52f
842c19:dd:d9:dd:c25:c25:b003:b530/1242c19:dd:d9:dd:c25:c25:b003:b53f
852c19:dd:d9:dd:c25:c25:b003:b540/1242c19:dd:d9:dd:c25:c25:b003:b54f
862c19:dd:d9:dd:c25:c25:b003:b550/1242c19:dd:d9:dd:c25:c25:b003:b55f
872c19:dd:d9:dd:c25:c25:b003:b560/1242c19:dd:d9:dd:c25:c25:b003:b56f
882c19:dd:d9:dd:c25:c25:b003:b570/1242c19:dd:d9:dd:c25:c25:b003:b57f
892c19:dd:d9:dd:c25:c25:b003:b580/1242c19:dd:d9:dd:c25:c25:b003:b58f
902c19:dd:d9:dd:c25:c25:b003:b590/1242c19:dd:d9:dd:c25:c25:b003:b59f
912c19:dd:d9:dd:c25:c25:b003:b5a0/1242c19:dd:d9:dd:c25:c25:b003:b5af
922c19:dd:d9:dd:c25:c25:b003:b5b0/1242c19:dd:d9:dd:c25:c25:b003:b5bf
932c19:dd:d9:dd:c25:c25:b003:b5c0/1242c19:dd:d9:dd:c25:c25:b003:b5cf
942c19:dd:d9:dd:c25:c25:b003:b5d0/1242c19:dd:d9:dd:c25:c25:b003:b5df
952c19:dd:d9:dd:c25:c25:b003:b5e0/1242c19:dd:d9:dd:c25:c25:b003:b5ef
962c19:dd:d9:dd:c25:c25:b003:b5f0/1242c19:dd:d9:dd:c25:c25:b003:b5ff
972c19:dd:d9:dd:c25:c25:b003:b600/1242c19:dd:d9:dd:c25:c25:b003:b60f
982c19:dd:d9:dd:c25:c25:b003:b610/1242c19:dd:d9:dd:c25:c25:b003:b61f
992c19:dd:d9:dd:c25:c25:b003:b620/1242c19:dd:d9:dd:c25:c25:b003:b62f
1002c19:dd:d9:dd:c25:c25:b003:b630/1242c19:dd:d9:dd:c25:c25:b003:b63f
1012c19:dd:d9:dd:c25:c25:b003:b640/1242c19:dd:d9:dd:c25:c25:b003:b64f
1022c19:dd:d9:dd:c25:c25:b003:b650/1242c19:dd:d9:dd:c25:c25:b003:b65f
1032c19:dd:d9:dd:c25:c25:b003:b660/1242c19:dd:d9:dd:c25:c25:b003:b66f
1042c19:dd:d9:dd:c25:c25:b003:b670/1242c19:dd:d9:dd:c25:c25:b003:b67f
1052c19:dd:d9:dd:c25:c25:b003:b680/1242c19:dd:d9:dd:c25:c25:b003:b68f
1062c19:dd:d9:dd:c25:c25:b003:b690/1242c19:dd:d9:dd:c25:c25:b003:b69f
1072c19:dd:d9:dd:c25:c25:b003:b6a0/1242c19:dd:d9:dd:c25:c25:b003:b6af
1082c19:dd:d9:dd:c25:c25:b003:b6b0/1242c19:dd:d9:dd:c25:c25:b003:b6bf
1092c19:dd:d9:dd:c25:c25:b003:b6c0/1242c19:dd:d9:dd:c25:c25:b003:b6cf
1102c19:dd:d9:dd:c25:c25:b003:b6d0/1242c19:dd:d9:dd:c25:c25:b003:b6df
1112c19:dd:d9:dd:c25:c25:b003:b6e0/1242c19:dd:d9:dd:c25:c25:b003:b6ef
1122c19:dd:d9:dd:c25:c25:b003:b6f0/1242c19:dd:d9:dd:c25:c25:b003:b6ff
1132c19:dd:d9:dd:c25:c25:b003:b700/1242c19:dd:d9:dd:c25:c25:b003:b70f
1142c19:dd:d9:dd:c25:c25:b003:b710/1242c19:dd:d9:dd:c25:c25:b003:b71f
1152c19:dd:d9:dd:c25:c25:b003:b720/1242c19:dd:d9:dd:c25:c25:b003:b72f
1162c19:dd:d9:dd:c25:c25:b003:b730/1242c19:dd:d9:dd:c25:c25:b003:b73f
1172c19:dd:d9:dd:c25:c25:b003:b740/1242c19:dd:d9:dd:c25:c25:b003:b74f
1182c19:dd:d9:dd:c25:c25:b003:b750/1242c19:dd:d9:dd:c25:c25:b003:b75f
1192c19:dd:d9:dd:c25:c25:b003:b760/1242c19:dd:d9:dd:c25:c25:b003:b76f
1202c19:dd:d9:dd:c25:c25:b003:b770/1242c19:dd:d9:dd:c25:c25:b003:b77f
1212c19:dd:d9:dd:c25:c25:b003:b780/1242c19:dd:d9:dd:c25:c25:b003:b78f
1222c19:dd:d9:dd:c25:c25:b003:b790/1242c19:dd:d9:dd:c25:c25:b003:b79f
1232c19:dd:d9:dd:c25:c25:b003:b7a0/1242c19:dd:d9:dd:c25:c25:b003:b7af
1242c19:dd:d9:dd:c25:c25:b003:b7b0/1242c19:dd:d9:dd:c25:c25:b003:b7bf
1252c19:dd:d9:dd:c25:c25:b003:b7c0/1242c19:dd:d9:dd:c25:c25:b003:b7cf
1262c19:dd:d9:dd:c25:c25:b003:b7d0/1242c19:dd:d9:dd:c25:c25:b003:b7df
1272c19:dd:d9:dd:c25:c25:b003:b7e0/1242c19:dd:d9:dd:c25:c25:b003:b7ef
1282c19:dd:d9:dd:c25:c25:b003:b7f0/1242c19:dd:d9:dd:c25:c25:b003:b7ff
1292c19:dd:d9:dd:c25:c25:b003:b800/1242c19:dd:d9:dd:c25:c25:b003:b80f
1302c19:dd:d9:dd:c25:c25:b003:b810/1242c19:dd:d9:dd:c25:c25:b003:b81f
1312c19:dd:d9:dd:c25:c25:b003:b820/1242c19:dd:d9:dd:c25:c25:b003:b82f
1322c19:dd:d9:dd:c25:c25:b003:b830/1242c19:dd:d9:dd:c25:c25:b003:b83f
1332c19:dd:d9:dd:c25:c25:b003:b840/1242c19:dd:d9:dd:c25:c25:b003:b84f
1342c19:dd:d9:dd:c25:c25:b003:b850/1242c19:dd:d9:dd:c25:c25:b003:b85f
1352c19:dd:d9:dd:c25:c25:b003:b860/1242c19:dd:d9:dd:c25:c25:b003:b86f
1362c19:dd:d9:dd:c25:c25:b003:b870/1242c19:dd:d9:dd:c25:c25:b003:b87f
1372c19:dd:d9:dd:c25:c25:b003:b880/1242c19:dd:d9:dd:c25:c25:b003:b88f
1382c19:dd:d9:dd:c25:c25:b003:b890/1242c19:dd:d9:dd:c25:c25:b003:b89f
1392c19:dd:d9:dd:c25:c25:b003:b8a0/1242c19:dd:d9:dd:c25:c25:b003:b8af
1402c19:dd:d9:dd:c25:c25:b003:b8b0/1242c19:dd:d9:dd:c25:c25:b003:b8bf
1412c19:dd:d9:dd:c25:c25:b003:b8c0/1242c19:dd:d9:dd:c25:c25:b003:b8cf
1422c19:dd:d9:dd:c25:c25:b003:b8d0/1242c19:dd:d9:dd:c25:c25:b003:b8df
1432c19:dd:d9:dd:c25:c25:b003:b8e0/1242c19:dd:d9:dd:c25:c25:b003:b8ef
1442c19:dd:d9:dd:c25:c25:b003:b8f0/1242c19:dd:d9:dd:c25:c25:b003:b8ff
1452c19:dd:d9:dd:c25:c25:b003:b900/1242c19:dd:d9:dd:c25:c25:b003:b90f
1462c19:dd:d9:dd:c25:c25:b003:b910/1242c19:dd:d9:dd:c25:c25:b003:b91f
1472c19:dd:d9:dd:c25:c25:b003:b920/1242c19:dd:d9:dd:c25:c25:b003:b92f
1482c19:dd:d9:dd:c25:c25:b003:b930/1242c19:dd:d9:dd:c25:c25:b003:b93f
1492c19:dd:d9:dd:c25:c25:b003:b940/1242c19:dd:d9:dd:c25:c25:b003:b94f
1502c19:dd:d9:dd:c25:c25:b003:b950/1242c19:dd:d9:dd:c25:c25:b003:b95f
1512c19:dd:d9:dd:c25:c25:b003:b960/1242c19:dd:d9:dd:c25:c25:b003:b96f
1522c19:dd:d9:dd:c25:c25:b003:b970/1242c19:dd:d9:dd:c25:c25:b003:b97f
1532c19:dd:d9:dd:c25:c25:b003:b980/1242c19:dd:d9:dd:c25:c25:b003:b98f
1542c19:dd:d9:dd:c25:c25:b003:b990/1242c19:dd:d9:dd:c25:c25:b003:b99f
1552c19:dd:d9:dd:c25:c25:b003:b9a0/1242c19:dd:d9:dd:c25:c25:b003:b9af
1562c19:dd:d9:dd:c25:c25:b003:b9b0/1242c19:dd:d9:dd:c25:c25:b003:b9bf
1572c19:dd:d9:dd:c25:c25:b003:b9c0/1242c19:dd:d9:dd:c25:c25:b003:b9cf
1582c19:dd:d9:dd:c25:c25:b003:b9d0/1242c19:dd:d9:dd:c25:c25:b003:b9df
1592c19:dd:d9:dd:c25:c25:b003:b9e0/1242c19:dd:d9:dd:c25:c25:b003:b9ef
1602c19:dd:d9:dd:c25:c25:b003:b9f0/1242c19:dd:d9:dd:c25:c25:b003:b9ff
1612c19:dd:d9:dd:c25:c25:b003:ba00/1242c19:dd:d9:dd:c25:c25:b003:ba0f
1622c19:dd:d9:dd:c25:c25:b003:ba10/1242c19:dd:d9:dd:c25:c25:b003:ba1f
1632c19:dd:d9:dd:c25:c25:b003:ba20/1242c19:dd:d9:dd:c25:c25:b003:ba2f
1642c19:dd:d9:dd:c25:c25:b003:ba30/1242c19:dd:d9:dd:c25:c25:b003:ba3f
1652c19:dd:d9:dd:c25:c25:b003:ba40/1242c19:dd:d9:dd:c25:c25:b003:ba4f
1662c19:dd:d9:dd:c25:c25:b003:ba50/1242c19:dd:d9:dd:c25:c25:b003:ba5f
1672c19:dd:d9:dd:c25:c25:b003:ba60/1242c19:dd:d9:dd:c25:c25:b003:ba6f
1682c19:dd:d9:dd:c25:c25:b003:ba70/1242c19:dd:d9:dd:c25:c25:b003:ba7f
1692c19:dd:d9:dd:c25:c25:b003:ba80/1242c19:dd:d9:dd:c25:c25:b003:ba8f
1702c19:dd:d9:dd:c25:c25:b003:ba90/1242c19:dd:d9:dd:c25:c25:b003:ba9f
1712c19:dd:d9:dd:c25:c25:b003:baa0/1242c19:dd:d9:dd:c25:c25:b003:baaf
1722c19:dd:d9:dd:c25:c25:b003:bab0/1242c19:dd:d9:dd:c25:c25:b003:babf
1732c19:dd:d9:dd:c25:c25:b003:bac0/1242c19:dd:d9:dd:c25:c25:b003:bacf
1742c19:dd:d9:dd:c25:c25:b003:bad0/1242c19:dd:d9:dd:c25:c25:b003:badf
1752c19:dd:d9:dd:c25:c25:b003:bae0/1242c19:dd:d9:dd:c25:c25:b003:baef
1762c19:dd:d9:dd:c25:c25:b003:baf0/1242c19:dd:d9:dd:c25:c25:b003:baff
1772c19:dd:d9:dd:c25:c25:b003:bb00/1242c19:dd:d9:dd:c25:c25:b003:bb0f
1782c19:dd:d9:dd:c25:c25:b003:bb10/1242c19:dd:d9:dd:c25:c25:b003:bb1f
1792c19:dd:d9:dd:c25:c25:b003:bb20/1242c19:dd:d9:dd:c25:c25:b003:bb2f
1802c19:dd:d9:dd:c25:c25:b003:bb30/1242c19:dd:d9:dd:c25:c25:b003:bb3f
1812c19:dd:d9:dd:c25:c25:b003:bb40/1242c19:dd:d9:dd:c25:c25:b003:bb4f
1822c19:dd:d9:dd:c25:c25:b003:bb50/1242c19:dd:d9:dd:c25:c25:b003:bb5f
1832c19:dd:d9:dd:c25:c25:b003:bb60/1242c19:dd:d9:dd:c25:c25:b003:bb6f
1842c19:dd:d9:dd:c25:c25:b003:bb70/1242c19:dd:d9:dd:c25:c25:b003:bb7f
1852c19:dd:d9:dd:c25:c25:b003:bb80/1242c19:dd:d9:dd:c25:c25:b003:bb8f
1862c19:dd:d9:dd:c25:c25:b003:bb90/1242c19:dd:d9:dd:c25:c25:b003:bb9f
1872c19:dd:d9:dd:c25:c25:b003:bba0/1242c19:dd:d9:dd:c25:c25:b003:bbaf
1882c19:dd:d9:dd:c25:c25:b003:bbb0/1242c19:dd:d9:dd:c25:c25:b003:bbbf
1892c19:dd:d9:dd:c25:c25:b003:bbc0/1242c19:dd:d9:dd:c25:c25:b003:bbcf
1902c19:dd:d9:dd:c25:c25:b003:bbd0/1242c19:dd:d9:dd:c25:c25:b003:bbdf
1912c19:dd:d9:dd:c25:c25:b003:bbe0/1242c19:dd:d9:dd:c25:c25:b003:bbef
1922c19:dd:d9:dd:c25:c25:b003:bbf0/1242c19:dd:d9:dd:c25:c25:b003:bbff
1932c19:dd:d9:dd:c25:c25:b003:bc00/1242c19:dd:d9:dd:c25:c25:b003:bc0f
1942c19:dd:d9:dd:c25:c25:b003:bc10/1242c19:dd:d9:dd:c25:c25:b003:bc1f
1952c19:dd:d9:dd:c25:c25:b003:bc20/1242c19:dd:d9:dd:c25:c25:b003:bc2f
1962c19:dd:d9:dd:c25:c25:b003:bc30/1242c19:dd:d9:dd:c25:c25:b003:bc3f
1972c19:dd:d9:dd:c25:c25:b003:bc40/1242c19:dd:d9:dd:c25:c25:b003:bc4f
1982c19:dd:d9:dd:c25:c25:b003:bc50/1242c19:dd:d9:dd:c25:c25:b003:bc5f
1992c19:dd:d9:dd:c25:c25:b003:bc60/1242c19:dd:d9:dd:c25:c25:b003:bc6f
2002c19:dd:d9:dd:c25:c25:b003:bc70/1242c19:dd:d9:dd:c25:c25:b003:bc7f
2012c19:dd:d9:dd:c25:c25:b003:bc80/1242c19:dd:d9:dd:c25:c25:b003:bc8f
2022c19:dd:d9:dd:c25:c25:b003:bc90/1242c19:dd:d9:dd:c25:c25:b003:bc9f
2032c19:dd:d9:dd:c25:c25:b003:bca0/1242c19:dd:d9:dd:c25:c25:b003:bcaf
2042c19:dd:d9:dd:c25:c25:b003:bcb0/1242c19:dd:d9:dd:c25:c25:b003:bcbf
2052c19:dd:d9:dd:c25:c25:b003:bcc0/1242c19:dd:d9:dd:c25:c25:b003:bccf
2062c19:dd:d9:dd:c25:c25:b003:bcd0/1242c19:dd:d9:dd:c25:c25:b003:bcdf
2072c19:dd:d9:dd:c25:c25:b003:bce0/1242c19:dd:d9:dd:c25:c25:b003:bcef
2082c19:dd:d9:dd:c25:c25:b003:bcf0/1242c19:dd:d9:dd:c25:c25:b003:bcff
2092c19:dd:d9:dd:c25:c25:b003:bd00/1242c19:dd:d9:dd:c25:c25:b003:bd0f
2102c19:dd:d9:dd:c25:c25:b003:bd10/1242c19:dd:d9:dd:c25:c25:b003:bd1f
2112c19:dd:d9:dd:c25:c25:b003:bd20/1242c19:dd:d9:dd:c25:c25:b003:bd2f
2122c19:dd:d9:dd:c25:c25:b003:bd30/1242c19:dd:d9:dd:c25:c25:b003:bd3f
2132c19:dd:d9:dd:c25:c25:b003:bd40/1242c19:dd:d9:dd:c25:c25:b003:bd4f
2142c19:dd:d9:dd:c25:c25:b003:bd50/1242c19:dd:d9:dd:c25:c25:b003:bd5f
2152c19:dd:d9:dd:c25:c25:b003:bd60/1242c19:dd:d9:dd:c25:c25:b003:bd6f
2162c19:dd:d9:dd:c25:c25:b003:bd70/1242c19:dd:d9:dd:c25:c25:b003:bd7f
2172c19:dd:d9:dd:c25:c25:b003:bd80/1242c19:dd:d9:dd:c25:c25:b003:bd8f
2182c19:dd:d9:dd:c25:c25:b003:bd90/1242c19:dd:d9:dd:c25:c25:b003:bd9f
2192c19:dd:d9:dd:c25:c25:b003:bda0/1242c19:dd:d9:dd:c25:c25:b003:bdaf
2202c19:dd:d9:dd:c25:c25:b003:bdb0/1242c19:dd:d9:dd:c25:c25:b003:bdbf
2212c19:dd:d9:dd:c25:c25:b003:bdc0/1242c19:dd:d9:dd:c25:c25:b003:bdcf
2222c19:dd:d9:dd:c25:c25:b003:bdd0/1242c19:dd:d9:dd:c25:c25:b003:bddf
2232c19:dd:d9:dd:c25:c25:b003:bde0/1242c19:dd:d9:dd:c25:c25:b003:bdef
2242c19:dd:d9:dd:c25:c25:b003:bdf0/1242c19:dd:d9:dd:c25:c25:b003:bdff
2252c19:dd:d9:dd:c25:c25:b003:be00/1242c19:dd:d9:dd:c25:c25:b003:be0f
2262c19:dd:d9:dd:c25:c25:b003:be10/1242c19:dd:d9:dd:c25:c25:b003:be1f
2272c19:dd:d9:dd:c25:c25:b003:be20/1242c19:dd:d9:dd:c25:c25:b003:be2f
2282c19:dd:d9:dd:c25:c25:b003:be30/1242c19:dd:d9:dd:c25:c25:b003:be3f
2292c19:dd:d9:dd:c25:c25:b003:be40/1242c19:dd:d9:dd:c25:c25:b003:be4f
2302c19:dd:d9:dd:c25:c25:b003:be50/1242c19:dd:d9:dd:c25:c25:b003:be5f
2312c19:dd:d9:dd:c25:c25:b003:be60/1242c19:dd:d9:dd:c25:c25:b003:be6f
2322c19:dd:d9:dd:c25:c25:b003:be70/1242c19:dd:d9:dd:c25:c25:b003:be7f
2332c19:dd:d9:dd:c25:c25:b003:be80/1242c19:dd:d9:dd:c25:c25:b003:be8f
2342c19:dd:d9:dd:c25:c25:b003:be90/1242c19:dd:d9:dd:c25:c25:b003:be9f
2352c19:dd:d9:dd:c25:c25:b003:bea0/1242c19:dd:d9:dd:c25:c25:b003:beaf
2362c19:dd:d9:dd:c25:c25:b003:beb0/1242c19:dd:d9:dd:c25:c25:b003:bebf
2372c19:dd:d9:dd:c25:c25:b003:bec0/1242c19:dd:d9:dd:c25:c25:b003:becf
2382c19:dd:d9:dd:c25:c25:b003:bed0/1242c19:dd:d9:dd:c25:c25:b003:bedf
2392c19:dd:d9:dd:c25:c25:b003:bee0/1242c19:dd:d9:dd:c25:c25:b003:beef
2402c19:dd:d9:dd:c25:c25:b003:bef0/1242c19:dd:d9:dd:c25:c25:b003:beff
2412c19:dd:d9:dd:c25:c25:b003:bf00/1242c19:dd:d9:dd:c25:c25:b003:bf0f
2422c19:dd:d9:dd:c25:c25:b003:bf10/1242c19:dd:d9:dd:c25:c25:b003:bf1f
2432c19:dd:d9:dd:c25:c25:b003:bf20/1242c19:dd:d9:dd:c25:c25:b003:bf2f
2442c19:dd:d9:dd:c25:c25:b003:bf30/1242c19:dd:d9:dd:c25:c25:b003:bf3f
2452c19:dd:d9:dd:c25:c25:b003:bf40/1242c19:dd:d9:dd:c25:c25:b003:bf4f
2462c19:dd:d9:dd:c25:c25:b003:bf50/1242c19:dd:d9:dd:c25:c25:b003:bf5f
2472c19:dd:d9:dd:c25:c25:b003:bf60/1242c19:dd:d9:dd:c25:c25:b003:bf6f
2482c19:dd:d9:dd:c25:c25:b003:bf70/1242c19:dd:d9:dd:c25:c25:b003:bf7f
2492c19:dd:d9:dd:c25:c25:b003:bf80/1242c19:dd:d9:dd:c25:c25:b003:bf8f
2502c19:dd:d9:dd:c25:c25:b003:bf90/1242c19:dd:d9:dd:c25:c25:b003:bf9f
2512c19:dd:d9:dd:c25:c25:b003:bfa0/1242c19:dd:d9:dd:c25:c25:b003:bfaf
2522c19:dd:d9:dd:c25:c25:b003:bfb0/1242c19:dd:d9:dd:c25:c25:b003:bfbf
2532c19:dd:d9:dd:c25:c25:b003:bfc0/1242c19:dd:d9:dd:c25:c25:b003:bfcf
2542c19:dd:d9:dd:c25:c25:b003:bfd0/1242c19:dd:d9:dd:c25:c25:b003:bfdf
2552c19:dd:d9:dd:c25:c25:b003:bfe0/1242c19:dd:d9:dd:c25:c25:b003:bfef
2562c19:dd:d9:dd:c25:c25:b003:bff0/1242c19:dd:d9:dd:c25:c25:b003:bfff

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.