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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.

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IP subnet calculator

Type an address with its prefix or mask to see the network, its usable range and masks. Split it into smaller subnets, or look up any prefix in the reference tables.

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

2cbb::/16 makes 4,096 subnets of /28; the first 256 are listed.

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

IPv4 CIDR reference (/0 to /32)

IPv4 prefix lengths
PrefixSubnet maskWildcardAddressesUsable hostsSizeTypical use
/00.0.0.0255.255.255.2554,294,967,2964,294,967,29416,777,216 × /24
/1128.0.0.0127.255.255.2552,147,483,6482,147,483,6468,388,608 × /24
/2192.0.0.063.255.255.2551,073,741,8241,073,741,8224,194,304 × /24
/3224.0.0.031.255.255.255536,870,912536,870,9102,097,152 × /24
/4240.0.0.015.255.255.255268,435,456268,435,4541,048,576 × /24
/5248.0.0.07.255.255.255134,217,728134,217,726524,288 × /24
/6252.0.0.03.255.255.25567,108,86467,108,862262,144 × /24
/7254.0.0.01.255.255.25533,554,43233,554,430131,072 × /24
/8255.0.0.00.255.255.25516,777,21616,777,21465,536 × /24Old class A; 10.0.0.0/8
/9255.128.0.00.127.255.2558,388,6088,388,60632,768 × /24
/10255.192.0.00.63.255.2554,194,3044,194,30216,384 × /24
/11255.224.0.00.31.255.2552,097,1522,097,1508,192 × /24
/12255.240.0.00.15.255.2551,048,5761,048,5744,096 × /24172.16.0.0/12
/13255.248.0.00.7.255.255524,288524,2862,048 × /24
/14255.252.0.00.3.255.255262,144262,1421,024 × /24
/15255.254.0.00.1.255.255131,072131,070512 × /24
/16255.255.0.00.0.255.25565,53665,534256 × /24Old class B; 192.168.0.0/16
/17255.255.128.00.0.127.25532,76832,766128 × /24
/18255.255.192.00.0.63.25516,38416,38264 × /24
/19255.255.224.00.0.31.2558,1928,19032 × /24
/20255.255.240.00.0.15.2554,0964,09416 × /24
/21255.255.248.00.0.7.2552,0482,0468 × /24
/22255.255.252.00.0.3.2551,0241,0224 × /24Large office or guest Wi-Fi (1,022 hosts)
/23255.255.254.00.0.1.2555125102 × /24Larger office LAN (510 hosts)
/24255.255.255.00.0.0.2552562541 × /24Typical office LAN (old class C)
/25255.255.255.1280.0.0.1271281261/2 of a /24Smaller LAN or VLAN
/26255.255.255.1920.0.0.6364621/4 of a /24Smaller LAN or VLAN
/27255.255.255.2240.0.0.3132301/8 of a /24Small VLAN, phones, cameras
/28255.255.255.2400.0.0.1516141/16 of a /24Small VLAN, phones, cameras
/29255.255.255.2480.0.0.7861/32 of a /24Small fixed public block (5 usable)
/30255.255.255.2520.0.0.3421/64 of a /24Point-to-point (old style)
/31255.255.255.2540.0.0.1221/128 of a /24Point-to-point link (RFC 3021)
/32255.255.255.2550.0.0.0111/256 of a /24One host

IPv6 prefix reference

IPv6 prefix lengths
PrefixAddresses/64 LANs/48 sitesNibbleTypical use
/342,535,295,865,117,307,932,921,825,928,971,026,432 (2^125)2,305,843,009,213,693,95235,184,372,088,832NoAll global unicast (2000::/3)
/165,192,296,858,534,827,628,530,496,329,220,096 (2^112)281,474,976,710,6564,294,967,296Yes
/20324,518,553,658,426,726,783,156,020,576,256 (2^108)17,592,186,044,416268,435,456YesLarge provider allocation (RIPE minimum for some)
/29633,825,300,114,114,700,748,351,602,688 (2^99)34,359,738,368524,288NoRIPE allocation to a provider (often)
/3279,228,162,514,264,337,593,543,950,336 (2^96)4,294,967,29665,536YesProvider allocation (RIPE default)
/364,951,760,157,141,521,099,596,496,896 (2^92)268,435,4564,096Yes
/40309,485,009,821,345,068,724,781,056 (2^88)16,777,216256Yes
/4419,342,813,113,834,066,795,298,816 (2^84)1,048,57616Yes
/481,208,925,819,614,629,174,706,176 (2^80)65,5361YesOne site or organisation (RIPE PI / assignment)
/5275,557,863,725,914,323,419,136 (2^76)4,096Yes
/564,722,366,482,869,645,213,696 (2^72)256YesSmall site or home (common provider assignment)
/60295,147,905,179,352,825,856 (2^68)16YesSome home broadband (16 LANs)
/6418,446,744,073,709,551,616 (2^64)1YesOne LAN or VLAN (needed for SLAAC)
/7272,057,594,037,927,936 (2^56)1/256 of a /64Yes
/80281,474,976,710,656 (2^48)1/65,536 of a /64Yes
/964,294,967,2961/4,294,967,296 of a /64YesEmbeds an IPv4 address (NAT64)
/11265,5361/281,474,976,710,656 of a /64Yes
/1202561/72,057,594,037,927,936 of a /64Yes
/124161/1,152,921,504,606,846,976 of a /64Yes
/12641/4,611,686,018,427,387,904 of a /64No
/12721/9,223,372,036,854,775,808 of a /64NoPoint-to-point link (RFC 6164)
/12811/18,446,744,073,709,551,616 of a /64YesOne host or loopback

Private and special ranges

IPv4

Special-purpose ranges
RangeNameWhat it is
255.255.255.255/32Limited broadcastEvery host on the local network
0.0.0.0/8This networkNot routed; 0.0.0.0 means "any address" in settings
10.0.0.0/8Private (RFC 1918)Office and home networks; not routed on the internet
100.64.0.0/10Shared address space (CGNAT)Used by providers behind carrier-grade NAT (RFC 6598)
127.0.0.0/8LoopbackThis computer
169.254.0.0/16Link-local (APIPA)Self-assigned when no DHCP server answers
172.16.0.0/12Private (RFC 1918)Office and home networks; not routed on the internet
192.0.0.0/24IETF protocol assignmentsSpecial uses such as DS-Lite
192.0.2.0/24Documentation (TEST-NET-1)For examples; never used on a network
192.88.99.0/246to4 relay (deprecated)Formerly anycast for 6to4
192.168.0.0/16Private (RFC 1918)Office and home networks; not routed on the internet
198.18.0.0/15BenchmarkingNetwork equipment testing (RFC 2544)
198.51.100.0/24Documentation (TEST-NET-2)For examples; never used on a network
203.0.113.0/24Documentation (TEST-NET-3)For examples; never used on a network
224.0.0.0/4MulticastOne-to-many traffic, such as IPTV and routing protocols
240.0.0.0/4ReservedFuture use; not usable on most systems

IPv6

Special-purpose ranges
RangeNameWhat it is
::/128UnspecifiedNo address; :: means "any address" in settings
::1/128LoopbackThis computer
::ffff:0:0/96IPv4-mappedAn IPv4 address written as IPv6
64:ff9b::/96NAT64IPv4 addresses reached through a NAT64 gateway
100::/64Discard onlyTraffic sent here is dropped (RFC 6666)
2001:db8::/32DocumentationFor examples; never used on a network
2001::/32TeredoIPv6 tunnelled over IPv4 UDP
2002::/166to4IPv6 tunnelled over IPv4 (largely retired)
3fff::/20DocumentationFor examples (RFC 9637)
fc00::/7Unique local (ULA)Private IPv6, like RFC 1918; usually fd00::/8
fe80::/10Link-localEvery IPv6 interface has one; not routed
ff00::/8MulticastOne-to-many traffic; replaces broadcast
2000::/3Global unicastPublic internet addresses

About this tool

A network is written as an address and a prefix length, such as 192.168.1.0/24: the first 24 bits name the network and the rest number the devices on it. The calculator works out where the network starts and ends, how many devices it holds, its subnet and wildcard masks, and the reverse DNS zone to ask your provider for.

It also splits a network into equal smaller ones (one per VLAN or site), turns a range of addresses into the fewest CIDR blocks for a firewall rule, and lists every IPv4 prefix length and the common IPv6 ones in reference tables.

Common questions

Why are two addresses lost in every IPv4 subnet?

The first address names the network and the last is the broadcast address, so a /24 has 256 addresses but 254 for devices. A /31 (a link between two routers) and a /32 (one host) are the exceptions.

What size of IPv6 network should a LAN use?

Always /64. Devices pick their own address within it (SLAAC), which needs the full 64 bits. A site usually gets a /48 or /56 from its provider, which holds 65,536 or 256 LANs.

What is a wildcard mask?

The subnet mask turned inside out: 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF use it to say which bits must match.

Which ranges can I use inside an office?

IPv4: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. IPv6: unique local addresses from fd00::/8, though most networks use the public prefix from their provider.