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/36
Addresses2^92
/64 networks268,435,456
Network
3fff:a::/36
First address
3fff:a::
Last address
3fff:a:fff:ffff:ffff:ffff:ffff:ffff
Addresses
4,951,760,157,141,521,099,596,496,896 (2^92)
/64 networks (LANs)
268,435,456
Full form
3fff:000a:0000:0000:0000:0000:0000:0000
Type
Documentation 3fff::/20
For examples (RFC 9637)
Reverse DNS zone
0.a.0.0.0.f.f.f.3.ip6.arpa
Split into smaller subnets/44
/37 (2)/38 (4)/39 (8)/40 (16)/44 (256)/48 (4,096)/52 (65,536)

3fff:a::/36 makes 256 subnets of /44.

Subnets
#SubnetLast address
13fff:a::/443fff:a:f:ffff:ffff:ffff:ffff:ffff
23fff:a:10::/443fff:a:1f:ffff:ffff:ffff:ffff:ffff
33fff:a:20::/443fff:a:2f:ffff:ffff:ffff:ffff:ffff
43fff:a:30::/443fff:a:3f:ffff:ffff:ffff:ffff:ffff
53fff:a:40::/443fff:a:4f:ffff:ffff:ffff:ffff:ffff
63fff:a:50::/443fff:a:5f:ffff:ffff:ffff:ffff:ffff
73fff:a:60::/443fff:a:6f:ffff:ffff:ffff:ffff:ffff
83fff:a:70::/443fff:a:7f:ffff:ffff:ffff:ffff:ffff
93fff:a:80::/443fff:a:8f:ffff:ffff:ffff:ffff:ffff
103fff:a:90::/443fff:a:9f:ffff:ffff:ffff:ffff:ffff
113fff:a:a0::/443fff:a:af:ffff:ffff:ffff:ffff:ffff
123fff:a:b0::/443fff:a:bf:ffff:ffff:ffff:ffff:ffff
133fff:a:c0::/443fff:a:cf:ffff:ffff:ffff:ffff:ffff
143fff:a:d0::/443fff:a:df:ffff:ffff:ffff:ffff:ffff
153fff:a:e0::/443fff:a:ef:ffff:ffff:ffff:ffff:ffff
163fff:a:f0::/443fff:a:ff:ffff:ffff:ffff:ffff:ffff
173fff:a:100::/443fff:a:10f:ffff:ffff:ffff:ffff:ffff
183fff:a:110::/443fff:a:11f:ffff:ffff:ffff:ffff:ffff
193fff:a:120::/443fff:a:12f:ffff:ffff:ffff:ffff:ffff
203fff:a:130::/443fff:a:13f:ffff:ffff:ffff:ffff:ffff
213fff:a:140::/443fff:a:14f:ffff:ffff:ffff:ffff:ffff
223fff:a:150::/443fff:a:15f:ffff:ffff:ffff:ffff:ffff
233fff:a:160::/443fff:a:16f:ffff:ffff:ffff:ffff:ffff
243fff:a:170::/443fff:a:17f:ffff:ffff:ffff:ffff:ffff
253fff:a:180::/443fff:a:18f:ffff:ffff:ffff:ffff:ffff
263fff:a:190::/443fff:a:19f:ffff:ffff:ffff:ffff:ffff
273fff:a:1a0::/443fff:a:1af:ffff:ffff:ffff:ffff:ffff
283fff:a:1b0::/443fff:a:1bf:ffff:ffff:ffff:ffff:ffff
293fff:a:1c0::/443fff:a:1cf:ffff:ffff:ffff:ffff:ffff
303fff:a:1d0::/443fff:a:1df:ffff:ffff:ffff:ffff:ffff
313fff:a:1e0::/443fff:a:1ef:ffff:ffff:ffff:ffff:ffff
323fff:a:1f0::/443fff:a:1ff:ffff:ffff:ffff:ffff:ffff
333fff:a:200::/443fff:a:20f:ffff:ffff:ffff:ffff:ffff
343fff:a:210::/443fff:a:21f:ffff:ffff:ffff:ffff:ffff
353fff:a:220::/443fff:a:22f:ffff:ffff:ffff:ffff:ffff
363fff:a:230::/443fff:a:23f:ffff:ffff:ffff:ffff:ffff
373fff:a:240::/443fff:a:24f:ffff:ffff:ffff:ffff:ffff
383fff:a:250::/443fff:a:25f:ffff:ffff:ffff:ffff:ffff
393fff:a:260::/443fff:a:26f:ffff:ffff:ffff:ffff:ffff
403fff:a:270::/443fff:a:27f:ffff:ffff:ffff:ffff:ffff
413fff:a:280::/443fff:a:28f:ffff:ffff:ffff:ffff:ffff
423fff:a:290::/443fff:a:29f:ffff:ffff:ffff:ffff:ffff
433fff:a:2a0::/443fff:a:2af:ffff:ffff:ffff:ffff:ffff
443fff:a:2b0::/443fff:a:2bf:ffff:ffff:ffff:ffff:ffff
453fff:a:2c0::/443fff:a:2cf:ffff:ffff:ffff:ffff:ffff
463fff:a:2d0::/443fff:a:2df:ffff:ffff:ffff:ffff:ffff
473fff:a:2e0::/443fff:a:2ef:ffff:ffff:ffff:ffff:ffff
483fff:a:2f0::/443fff:a:2ff:ffff:ffff:ffff:ffff:ffff
493fff:a:300::/443fff:a:30f:ffff:ffff:ffff:ffff:ffff
503fff:a:310::/443fff:a:31f:ffff:ffff:ffff:ffff:ffff
513fff:a:320::/443fff:a:32f:ffff:ffff:ffff:ffff:ffff
523fff:a:330::/443fff:a:33f:ffff:ffff:ffff:ffff:ffff
533fff:a:340::/443fff:a:34f:ffff:ffff:ffff:ffff:ffff
543fff:a:350::/443fff:a:35f:ffff:ffff:ffff:ffff:ffff
553fff:a:360::/443fff:a:36f:ffff:ffff:ffff:ffff:ffff
563fff:a:370::/443fff:a:37f:ffff:ffff:ffff:ffff:ffff
573fff:a:380::/443fff:a:38f:ffff:ffff:ffff:ffff:ffff
583fff:a:390::/443fff:a:39f:ffff:ffff:ffff:ffff:ffff
593fff:a:3a0::/443fff:a:3af:ffff:ffff:ffff:ffff:ffff
603fff:a:3b0::/443fff:a:3bf:ffff:ffff:ffff:ffff:ffff
613fff:a:3c0::/443fff:a:3cf:ffff:ffff:ffff:ffff:ffff
623fff:a:3d0::/443fff:a:3df:ffff:ffff:ffff:ffff:ffff
633fff:a:3e0::/443fff:a:3ef:ffff:ffff:ffff:ffff:ffff
643fff:a:3f0::/443fff:a:3ff:ffff:ffff:ffff:ffff:ffff
653fff:a:400::/443fff:a:40f:ffff:ffff:ffff:ffff:ffff
663fff:a:410::/443fff:a:41f:ffff:ffff:ffff:ffff:ffff
673fff:a:420::/443fff:a:42f:ffff:ffff:ffff:ffff:ffff
683fff:a:430::/443fff:a:43f:ffff:ffff:ffff:ffff:ffff
693fff:a:440::/443fff:a:44f:ffff:ffff:ffff:ffff:ffff
703fff:a:450::/443fff:a:45f:ffff:ffff:ffff:ffff:ffff
713fff:a:460::/443fff:a:46f:ffff:ffff:ffff:ffff:ffff
723fff:a:470::/443fff:a:47f:ffff:ffff:ffff:ffff:ffff
733fff:a:480::/443fff:a:48f:ffff:ffff:ffff:ffff:ffff
743fff:a:490::/443fff:a:49f:ffff:ffff:ffff:ffff:ffff
753fff:a:4a0::/443fff:a:4af:ffff:ffff:ffff:ffff:ffff
763fff:a:4b0::/443fff:a:4bf:ffff:ffff:ffff:ffff:ffff
773fff:a:4c0::/443fff:a:4cf:ffff:ffff:ffff:ffff:ffff
783fff:a:4d0::/443fff:a:4df:ffff:ffff:ffff:ffff:ffff
793fff:a:4e0::/443fff:a:4ef:ffff:ffff:ffff:ffff:ffff
803fff:a:4f0::/443fff:a:4ff:ffff:ffff:ffff:ffff:ffff
813fff:a:500::/443fff:a:50f:ffff:ffff:ffff:ffff:ffff
823fff:a:510::/443fff:a:51f:ffff:ffff:ffff:ffff:ffff
833fff:a:520::/443fff:a:52f:ffff:ffff:ffff:ffff:ffff
843fff:a:530::/443fff:a:53f:ffff:ffff:ffff:ffff:ffff
853fff:a:540::/443fff:a:54f:ffff:ffff:ffff:ffff:ffff
863fff:a:550::/443fff:a:55f:ffff:ffff:ffff:ffff:ffff
873fff:a:560::/443fff:a:56f:ffff:ffff:ffff:ffff:ffff
883fff:a:570::/443fff:a:57f:ffff:ffff:ffff:ffff:ffff
893fff:a:580::/443fff:a:58f:ffff:ffff:ffff:ffff:ffff
903fff:a:590::/443fff:a:59f:ffff:ffff:ffff:ffff:ffff
913fff:a:5a0::/443fff:a:5af:ffff:ffff:ffff:ffff:ffff
923fff:a:5b0::/443fff:a:5bf:ffff:ffff:ffff:ffff:ffff
933fff:a:5c0::/443fff:a:5cf:ffff:ffff:ffff:ffff:ffff
943fff:a:5d0::/443fff:a:5df:ffff:ffff:ffff:ffff:ffff
953fff:a:5e0::/443fff:a:5ef:ffff:ffff:ffff:ffff:ffff
963fff:a:5f0::/443fff:a:5ff:ffff:ffff:ffff:ffff:ffff
973fff:a:600::/443fff:a:60f:ffff:ffff:ffff:ffff:ffff
983fff:a:610::/443fff:a:61f:ffff:ffff:ffff:ffff:ffff
993fff:a:620::/443fff:a:62f:ffff:ffff:ffff:ffff:ffff
1003fff:a:630::/443fff:a:63f:ffff:ffff:ffff:ffff:ffff
1013fff:a:640::/443fff:a:64f:ffff:ffff:ffff:ffff:ffff
1023fff:a:650::/443fff:a:65f:ffff:ffff:ffff:ffff:ffff
1033fff:a:660::/443fff:a:66f:ffff:ffff:ffff:ffff:ffff
1043fff:a:670::/443fff:a:67f:ffff:ffff:ffff:ffff:ffff
1053fff:a:680::/443fff:a:68f:ffff:ffff:ffff:ffff:ffff
1063fff:a:690::/443fff:a:69f:ffff:ffff:ffff:ffff:ffff
1073fff:a:6a0::/443fff:a:6af:ffff:ffff:ffff:ffff:ffff
1083fff:a:6b0::/443fff:a:6bf:ffff:ffff:ffff:ffff:ffff
1093fff:a:6c0::/443fff:a:6cf:ffff:ffff:ffff:ffff:ffff
1103fff:a:6d0::/443fff:a:6df:ffff:ffff:ffff:ffff:ffff
1113fff:a:6e0::/443fff:a:6ef:ffff:ffff:ffff:ffff:ffff
1123fff:a:6f0::/443fff:a:6ff:ffff:ffff:ffff:ffff:ffff
1133fff:a:700::/443fff:a:70f:ffff:ffff:ffff:ffff:ffff
1143fff:a:710::/443fff:a:71f:ffff:ffff:ffff:ffff:ffff
1153fff:a:720::/443fff:a:72f:ffff:ffff:ffff:ffff:ffff
1163fff:a:730::/443fff:a:73f:ffff:ffff:ffff:ffff:ffff
1173fff:a:740::/443fff:a:74f:ffff:ffff:ffff:ffff:ffff
1183fff:a:750::/443fff:a:75f:ffff:ffff:ffff:ffff:ffff
1193fff:a:760::/443fff:a:76f:ffff:ffff:ffff:ffff:ffff
1203fff:a:770::/443fff:a:77f:ffff:ffff:ffff:ffff:ffff
1213fff:a:780::/443fff:a:78f:ffff:ffff:ffff:ffff:ffff
1223fff:a:790::/443fff:a:79f:ffff:ffff:ffff:ffff:ffff
1233fff:a:7a0::/443fff:a:7af:ffff:ffff:ffff:ffff:ffff
1243fff:a:7b0::/443fff:a:7bf:ffff:ffff:ffff:ffff:ffff
1253fff:a:7c0::/443fff:a:7cf:ffff:ffff:ffff:ffff:ffff
1263fff:a:7d0::/443fff:a:7df:ffff:ffff:ffff:ffff:ffff
1273fff:a:7e0::/443fff:a:7ef:ffff:ffff:ffff:ffff:ffff
1283fff:a:7f0::/443fff:a:7ff:ffff:ffff:ffff:ffff:ffff
1293fff:a:800::/443fff:a:80f:ffff:ffff:ffff:ffff:ffff
1303fff:a:810::/443fff:a:81f:ffff:ffff:ffff:ffff:ffff
1313fff:a:820::/443fff:a:82f:ffff:ffff:ffff:ffff:ffff
1323fff:a:830::/443fff:a:83f:ffff:ffff:ffff:ffff:ffff
1333fff:a:840::/443fff:a:84f:ffff:ffff:ffff:ffff:ffff
1343fff:a:850::/443fff:a:85f:ffff:ffff:ffff:ffff:ffff
1353fff:a:860::/443fff:a:86f:ffff:ffff:ffff:ffff:ffff
1363fff:a:870::/443fff:a:87f:ffff:ffff:ffff:ffff:ffff
1373fff:a:880::/443fff:a:88f:ffff:ffff:ffff:ffff:ffff
1383fff:a:890::/443fff:a:89f:ffff:ffff:ffff:ffff:ffff
1393fff:a:8a0::/443fff:a:8af:ffff:ffff:ffff:ffff:ffff
1403fff:a:8b0::/443fff:a:8bf:ffff:ffff:ffff:ffff:ffff
1413fff:a:8c0::/443fff:a:8cf:ffff:ffff:ffff:ffff:ffff
1423fff:a:8d0::/443fff:a:8df:ffff:ffff:ffff:ffff:ffff
1433fff:a:8e0::/443fff:a:8ef:ffff:ffff:ffff:ffff:ffff
1443fff:a:8f0::/443fff:a:8ff:ffff:ffff:ffff:ffff:ffff
1453fff:a:900::/443fff:a:90f:ffff:ffff:ffff:ffff:ffff
1463fff:a:910::/443fff:a:91f:ffff:ffff:ffff:ffff:ffff
1473fff:a:920::/443fff:a:92f:ffff:ffff:ffff:ffff:ffff
1483fff:a:930::/443fff:a:93f:ffff:ffff:ffff:ffff:ffff
1493fff:a:940::/443fff:a:94f:ffff:ffff:ffff:ffff:ffff
1503fff:a:950::/443fff:a:95f:ffff:ffff:ffff:ffff:ffff
1513fff:a:960::/443fff:a:96f:ffff:ffff:ffff:ffff:ffff
1523fff:a:970::/443fff:a:97f:ffff:ffff:ffff:ffff:ffff
1533fff:a:980::/443fff:a:98f:ffff:ffff:ffff:ffff:ffff
1543fff:a:990::/443fff:a:99f:ffff:ffff:ffff:ffff:ffff
1553fff:a:9a0::/443fff:a:9af:ffff:ffff:ffff:ffff:ffff
1563fff:a:9b0::/443fff:a:9bf:ffff:ffff:ffff:ffff:ffff
1573fff:a:9c0::/443fff:a:9cf:ffff:ffff:ffff:ffff:ffff
1583fff:a:9d0::/443fff:a:9df:ffff:ffff:ffff:ffff:ffff
1593fff:a:9e0::/443fff:a:9ef:ffff:ffff:ffff:ffff:ffff
1603fff:a:9f0::/443fff:a:9ff:ffff:ffff:ffff:ffff:ffff
1613fff:a:a00::/443fff:a:a0f:ffff:ffff:ffff:ffff:ffff
1623fff:a:a10::/443fff:a:a1f:ffff:ffff:ffff:ffff:ffff
1633fff:a:a20::/443fff:a:a2f:ffff:ffff:ffff:ffff:ffff
1643fff:a:a30::/443fff:a:a3f:ffff:ffff:ffff:ffff:ffff
1653fff:a:a40::/443fff:a:a4f:ffff:ffff:ffff:ffff:ffff
1663fff:a:a50::/443fff:a:a5f:ffff:ffff:ffff:ffff:ffff
1673fff:a:a60::/443fff:a:a6f:ffff:ffff:ffff:ffff:ffff
1683fff:a:a70::/443fff:a:a7f:ffff:ffff:ffff:ffff:ffff
1693fff:a:a80::/443fff:a:a8f:ffff:ffff:ffff:ffff:ffff
1703fff:a:a90::/443fff:a:a9f:ffff:ffff:ffff:ffff:ffff
1713fff:a:aa0::/443fff:a:aaf:ffff:ffff:ffff:ffff:ffff
1723fff:a:ab0::/443fff:a:abf:ffff:ffff:ffff:ffff:ffff
1733fff:a:ac0::/443fff:a:acf:ffff:ffff:ffff:ffff:ffff
1743fff:a:ad0::/443fff:a:adf:ffff:ffff:ffff:ffff:ffff
1753fff:a:ae0::/443fff:a:aef:ffff:ffff:ffff:ffff:ffff
1763fff:a:af0::/443fff:a:aff:ffff:ffff:ffff:ffff:ffff
1773fff:a:b00::/443fff:a:b0f:ffff:ffff:ffff:ffff:ffff
1783fff:a:b10::/443fff:a:b1f:ffff:ffff:ffff:ffff:ffff
1793fff:a:b20::/443fff:a:b2f:ffff:ffff:ffff:ffff:ffff
1803fff:a:b30::/443fff:a:b3f:ffff:ffff:ffff:ffff:ffff
1813fff:a:b40::/443fff:a:b4f:ffff:ffff:ffff:ffff:ffff
1823fff:a:b50::/443fff:a:b5f:ffff:ffff:ffff:ffff:ffff
1833fff:a:b60::/443fff:a:b6f:ffff:ffff:ffff:ffff:ffff
1843fff:a:b70::/443fff:a:b7f:ffff:ffff:ffff:ffff:ffff
1853fff:a:b80::/443fff:a:b8f:ffff:ffff:ffff:ffff:ffff
1863fff:a:b90::/443fff:a:b9f:ffff:ffff:ffff:ffff:ffff
1873fff:a:ba0::/443fff:a:baf:ffff:ffff:ffff:ffff:ffff
1883fff:a:bb0::/443fff:a:bbf:ffff:ffff:ffff:ffff:ffff
1893fff:a:bc0::/443fff:a:bcf:ffff:ffff:ffff:ffff:ffff
1903fff:a:bd0::/443fff:a:bdf:ffff:ffff:ffff:ffff:ffff
1913fff:a:be0::/443fff:a:bef:ffff:ffff:ffff:ffff:ffff
1923fff:a:bf0::/443fff:a:bff:ffff:ffff:ffff:ffff:ffff
1933fff:a:c00::/443fff:a:c0f:ffff:ffff:ffff:ffff:ffff
1943fff:a:c10::/443fff:a:c1f:ffff:ffff:ffff:ffff:ffff
1953fff:a:c20::/443fff:a:c2f:ffff:ffff:ffff:ffff:ffff
1963fff:a:c30::/443fff:a:c3f:ffff:ffff:ffff:ffff:ffff
1973fff:a:c40::/443fff:a:c4f:ffff:ffff:ffff:ffff:ffff
1983fff:a:c50::/443fff:a:c5f:ffff:ffff:ffff:ffff:ffff
1993fff:a:c60::/443fff:a:c6f:ffff:ffff:ffff:ffff:ffff
2003fff:a:c70::/443fff:a:c7f:ffff:ffff:ffff:ffff:ffff
2013fff:a:c80::/443fff:a:c8f:ffff:ffff:ffff:ffff:ffff
2023fff:a:c90::/443fff:a:c9f:ffff:ffff:ffff:ffff:ffff
2033fff:a:ca0::/443fff:a:caf:ffff:ffff:ffff:ffff:ffff
2043fff:a:cb0::/443fff:a:cbf:ffff:ffff:ffff:ffff:ffff
2053fff:a:cc0::/443fff:a:ccf:ffff:ffff:ffff:ffff:ffff
2063fff:a:cd0::/443fff:a:cdf:ffff:ffff:ffff:ffff:ffff
2073fff:a:ce0::/443fff:a:cef:ffff:ffff:ffff:ffff:ffff
2083fff:a:cf0::/443fff:a:cff:ffff:ffff:ffff:ffff:ffff
2093fff:a:d00::/443fff:a:d0f:ffff:ffff:ffff:ffff:ffff
2103fff:a:d10::/443fff:a:d1f:ffff:ffff:ffff:ffff:ffff
2113fff:a:d20::/443fff:a:d2f:ffff:ffff:ffff:ffff:ffff
2123fff:a:d30::/443fff:a:d3f:ffff:ffff:ffff:ffff:ffff
2133fff:a:d40::/443fff:a:d4f:ffff:ffff:ffff:ffff:ffff
2143fff:a:d50::/443fff:a:d5f:ffff:ffff:ffff:ffff:ffff
2153fff:a:d60::/443fff:a:d6f:ffff:ffff:ffff:ffff:ffff
2163fff:a:d70::/443fff:a:d7f:ffff:ffff:ffff:ffff:ffff
2173fff:a:d80::/443fff:a:d8f:ffff:ffff:ffff:ffff:ffff
2183fff:a:d90::/443fff:a:d9f:ffff:ffff:ffff:ffff:ffff
2193fff:a:da0::/443fff:a:daf:ffff:ffff:ffff:ffff:ffff
2203fff:a:db0::/443fff:a:dbf:ffff:ffff:ffff:ffff:ffff
2213fff:a:dc0::/443fff:a:dcf:ffff:ffff:ffff:ffff:ffff
2223fff:a:dd0::/443fff:a:ddf:ffff:ffff:ffff:ffff:ffff
2233fff:a:de0::/443fff:a:def:ffff:ffff:ffff:ffff:ffff
2243fff:a:df0::/443fff:a:dff:ffff:ffff:ffff:ffff:ffff
2253fff:a:e00::/443fff:a:e0f:ffff:ffff:ffff:ffff:ffff
2263fff:a:e10::/443fff:a:e1f:ffff:ffff:ffff:ffff:ffff
2273fff:a:e20::/443fff:a:e2f:ffff:ffff:ffff:ffff:ffff
2283fff:a:e30::/443fff:a:e3f:ffff:ffff:ffff:ffff:ffff
2293fff:a:e40::/443fff:a:e4f:ffff:ffff:ffff:ffff:ffff
2303fff:a:e50::/443fff:a:e5f:ffff:ffff:ffff:ffff:ffff
2313fff:a:e60::/443fff:a:e6f:ffff:ffff:ffff:ffff:ffff
2323fff:a:e70::/443fff:a:e7f:ffff:ffff:ffff:ffff:ffff
2333fff:a:e80::/443fff:a:e8f:ffff:ffff:ffff:ffff:ffff
2343fff:a:e90::/443fff:a:e9f:ffff:ffff:ffff:ffff:ffff
2353fff:a:ea0::/443fff:a:eaf:ffff:ffff:ffff:ffff:ffff
2363fff:a:eb0::/443fff:a:ebf:ffff:ffff:ffff:ffff:ffff
2373fff:a:ec0::/443fff:a:ecf:ffff:ffff:ffff:ffff:ffff
2383fff:a:ed0::/443fff:a:edf:ffff:ffff:ffff:ffff:ffff
2393fff:a:ee0::/443fff:a:eef:ffff:ffff:ffff:ffff:ffff
2403fff:a:ef0::/443fff:a:eff:ffff:ffff:ffff:ffff:ffff
2413fff:a:f00::/443fff:a:f0f:ffff:ffff:ffff:ffff:ffff
2423fff:a:f10::/443fff:a:f1f:ffff:ffff:ffff:ffff:ffff
2433fff:a:f20::/443fff:a:f2f:ffff:ffff:ffff:ffff:ffff
2443fff:a:f30::/443fff:a:f3f:ffff:ffff:ffff:ffff:ffff
2453fff:a:f40::/443fff:a:f4f:ffff:ffff:ffff:ffff:ffff
2463fff:a:f50::/443fff:a:f5f:ffff:ffff:ffff:ffff:ffff
2473fff:a:f60::/443fff:a:f6f:ffff:ffff:ffff:ffff:ffff
2483fff:a:f70::/443fff:a:f7f:ffff:ffff:ffff:ffff:ffff
2493fff:a:f80::/443fff:a:f8f:ffff:ffff:ffff:ffff:ffff
2503fff:a:f90::/443fff:a:f9f:ffff:ffff:ffff:ffff:ffff
2513fff:a:fa0::/443fff:a:faf:ffff:ffff:ffff:ffff:ffff
2523fff:a:fb0::/443fff:a:fbf:ffff:ffff:ffff:ffff:ffff
2533fff:a:fc0::/443fff:a:fcf:ffff:ffff:ffff:ffff:ffff
2543fff:a:fd0::/443fff:a:fdf:ffff:ffff:ffff:ffff:ffff
2553fff:a:fe0::/443fff:a:fef:ffff:ffff:ffff:ffff:ffff
2563fff:a:ff0::/443fff:a:fff: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.