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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/12
Addresses2^116
/64 networks2^52
Network
21a0::/12
First address
21a0::
Last address
21af:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
83,076,749,736,557,242,056,487,941,267,521,536 (2^116)
/64 networks (LANs)
4,503,599,627,370,496 (2^52)
Full form
21a0:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
a.1.2.ip6.arpa
Split into smaller subnets/28
/13 (2)/14 (4)/15 (8)/16 (16)/20 (256)/24 (4,096)/28 (65,536)

21a0::/12 makes 65,536 subnets of /28; the first 256 are listed.

Subnets
#SubnetLast address
121a0::/2821a0:f:ffff:ffff:ffff:ffff:ffff:ffff
221a0:10::/2821a0:1f:ffff:ffff:ffff:ffff:ffff:ffff
321a0:20::/2821a0:2f:ffff:ffff:ffff:ffff:ffff:ffff
421a0:30::/2821a0:3f:ffff:ffff:ffff:ffff:ffff:ffff
521a0:40::/2821a0:4f:ffff:ffff:ffff:ffff:ffff:ffff
621a0:50::/2821a0:5f:ffff:ffff:ffff:ffff:ffff:ffff
721a0:60::/2821a0:6f:ffff:ffff:ffff:ffff:ffff:ffff
821a0:70::/2821a0:7f:ffff:ffff:ffff:ffff:ffff:ffff
921a0:80::/2821a0:8f:ffff:ffff:ffff:ffff:ffff:ffff
1021a0:90::/2821a0:9f:ffff:ffff:ffff:ffff:ffff:ffff
1121a0:a0::/2821a0:af:ffff:ffff:ffff:ffff:ffff:ffff
1221a0:b0::/2821a0:bf:ffff:ffff:ffff:ffff:ffff:ffff
1321a0:c0::/2821a0:cf:ffff:ffff:ffff:ffff:ffff:ffff
1421a0:d0::/2821a0:df:ffff:ffff:ffff:ffff:ffff:ffff
1521a0:e0::/2821a0:ef:ffff:ffff:ffff:ffff:ffff:ffff
1621a0:f0::/2821a0:ff:ffff:ffff:ffff:ffff:ffff:ffff
1721a0:100::/2821a0:10f:ffff:ffff:ffff:ffff:ffff:ffff
1821a0:110::/2821a0:11f:ffff:ffff:ffff:ffff:ffff:ffff
1921a0:120::/2821a0:12f:ffff:ffff:ffff:ffff:ffff:ffff
2021a0:130::/2821a0:13f:ffff:ffff:ffff:ffff:ffff:ffff
2121a0:140::/2821a0:14f:ffff:ffff:ffff:ffff:ffff:ffff
2221a0:150::/2821a0:15f:ffff:ffff:ffff:ffff:ffff:ffff
2321a0:160::/2821a0:16f:ffff:ffff:ffff:ffff:ffff:ffff
2421a0:170::/2821a0:17f:ffff:ffff:ffff:ffff:ffff:ffff
2521a0:180::/2821a0:18f:ffff:ffff:ffff:ffff:ffff:ffff
2621a0:190::/2821a0:19f:ffff:ffff:ffff:ffff:ffff:ffff
2721a0:1a0::/2821a0:1af:ffff:ffff:ffff:ffff:ffff:ffff
2821a0:1b0::/2821a0:1bf:ffff:ffff:ffff:ffff:ffff:ffff
2921a0:1c0::/2821a0:1cf:ffff:ffff:ffff:ffff:ffff:ffff
3021a0:1d0::/2821a0:1df:ffff:ffff:ffff:ffff:ffff:ffff
3121a0:1e0::/2821a0:1ef:ffff:ffff:ffff:ffff:ffff:ffff
3221a0:1f0::/2821a0:1ff:ffff:ffff:ffff:ffff:ffff:ffff
3321a0:200::/2821a0:20f:ffff:ffff:ffff:ffff:ffff:ffff
3421a0:210::/2821a0:21f:ffff:ffff:ffff:ffff:ffff:ffff
3521a0:220::/2821a0:22f:ffff:ffff:ffff:ffff:ffff:ffff
3621a0:230::/2821a0:23f:ffff:ffff:ffff:ffff:ffff:ffff
3721a0:240::/2821a0:24f:ffff:ffff:ffff:ffff:ffff:ffff
3821a0:250::/2821a0:25f:ffff:ffff:ffff:ffff:ffff:ffff
3921a0:260::/2821a0:26f:ffff:ffff:ffff:ffff:ffff:ffff
4021a0:270::/2821a0:27f:ffff:ffff:ffff:ffff:ffff:ffff
4121a0:280::/2821a0:28f:ffff:ffff:ffff:ffff:ffff:ffff
4221a0:290::/2821a0:29f:ffff:ffff:ffff:ffff:ffff:ffff
4321a0:2a0::/2821a0:2af:ffff:ffff:ffff:ffff:ffff:ffff
4421a0:2b0::/2821a0:2bf:ffff:ffff:ffff:ffff:ffff:ffff
4521a0:2c0::/2821a0:2cf:ffff:ffff:ffff:ffff:ffff:ffff
4621a0:2d0::/2821a0:2df:ffff:ffff:ffff:ffff:ffff:ffff
4721a0:2e0::/2821a0:2ef:ffff:ffff:ffff:ffff:ffff:ffff
4821a0:2f0::/2821a0:2ff:ffff:ffff:ffff:ffff:ffff:ffff
4921a0:300::/2821a0:30f:ffff:ffff:ffff:ffff:ffff:ffff
5021a0:310::/2821a0:31f:ffff:ffff:ffff:ffff:ffff:ffff
5121a0:320::/2821a0:32f:ffff:ffff:ffff:ffff:ffff:ffff
5221a0:330::/2821a0:33f:ffff:ffff:ffff:ffff:ffff:ffff
5321a0:340::/2821a0:34f:ffff:ffff:ffff:ffff:ffff:ffff
5421a0:350::/2821a0:35f:ffff:ffff:ffff:ffff:ffff:ffff
5521a0:360::/2821a0:36f:ffff:ffff:ffff:ffff:ffff:ffff
5621a0:370::/2821a0:37f:ffff:ffff:ffff:ffff:ffff:ffff
5721a0:380::/2821a0:38f:ffff:ffff:ffff:ffff:ffff:ffff
5821a0:390::/2821a0:39f:ffff:ffff:ffff:ffff:ffff:ffff
5921a0:3a0::/2821a0:3af:ffff:ffff:ffff:ffff:ffff:ffff
6021a0:3b0::/2821a0:3bf:ffff:ffff:ffff:ffff:ffff:ffff
6121a0:3c0::/2821a0:3cf:ffff:ffff:ffff:ffff:ffff:ffff
6221a0:3d0::/2821a0:3df:ffff:ffff:ffff:ffff:ffff:ffff
6321a0:3e0::/2821a0:3ef:ffff:ffff:ffff:ffff:ffff:ffff
6421a0:3f0::/2821a0:3ff:ffff:ffff:ffff:ffff:ffff:ffff
6521a0:400::/2821a0:40f:ffff:ffff:ffff:ffff:ffff:ffff
6621a0:410::/2821a0:41f:ffff:ffff:ffff:ffff:ffff:ffff
6721a0:420::/2821a0:42f:ffff:ffff:ffff:ffff:ffff:ffff
6821a0:430::/2821a0:43f:ffff:ffff:ffff:ffff:ffff:ffff
6921a0:440::/2821a0:44f:ffff:ffff:ffff:ffff:ffff:ffff
7021a0:450::/2821a0:45f:ffff:ffff:ffff:ffff:ffff:ffff
7121a0:460::/2821a0:46f:ffff:ffff:ffff:ffff:ffff:ffff
7221a0:470::/2821a0:47f:ffff:ffff:ffff:ffff:ffff:ffff
7321a0:480::/2821a0:48f:ffff:ffff:ffff:ffff:ffff:ffff
7421a0:490::/2821a0:49f:ffff:ffff:ffff:ffff:ffff:ffff
7521a0:4a0::/2821a0:4af:ffff:ffff:ffff:ffff:ffff:ffff
7621a0:4b0::/2821a0:4bf:ffff:ffff:ffff:ffff:ffff:ffff
7721a0:4c0::/2821a0:4cf:ffff:ffff:ffff:ffff:ffff:ffff
7821a0:4d0::/2821a0:4df:ffff:ffff:ffff:ffff:ffff:ffff
7921a0:4e0::/2821a0:4ef:ffff:ffff:ffff:ffff:ffff:ffff
8021a0:4f0::/2821a0:4ff:ffff:ffff:ffff:ffff:ffff:ffff
8121a0:500::/2821a0:50f:ffff:ffff:ffff:ffff:ffff:ffff
8221a0:510::/2821a0:51f:ffff:ffff:ffff:ffff:ffff:ffff
8321a0:520::/2821a0:52f:ffff:ffff:ffff:ffff:ffff:ffff
8421a0:530::/2821a0:53f:ffff:ffff:ffff:ffff:ffff:ffff
8521a0:540::/2821a0:54f:ffff:ffff:ffff:ffff:ffff:ffff
8621a0:550::/2821a0:55f:ffff:ffff:ffff:ffff:ffff:ffff
8721a0:560::/2821a0:56f:ffff:ffff:ffff:ffff:ffff:ffff
8821a0:570::/2821a0:57f:ffff:ffff:ffff:ffff:ffff:ffff
8921a0:580::/2821a0:58f:ffff:ffff:ffff:ffff:ffff:ffff
9021a0:590::/2821a0:59f:ffff:ffff:ffff:ffff:ffff:ffff
9121a0:5a0::/2821a0:5af:ffff:ffff:ffff:ffff:ffff:ffff
9221a0:5b0::/2821a0:5bf:ffff:ffff:ffff:ffff:ffff:ffff
9321a0:5c0::/2821a0:5cf:ffff:ffff:ffff:ffff:ffff:ffff
9421a0:5d0::/2821a0:5df:ffff:ffff:ffff:ffff:ffff:ffff
9521a0:5e0::/2821a0:5ef:ffff:ffff:ffff:ffff:ffff:ffff
9621a0:5f0::/2821a0:5ff:ffff:ffff:ffff:ffff:ffff:ffff
9721a0:600::/2821a0:60f:ffff:ffff:ffff:ffff:ffff:ffff
9821a0:610::/2821a0:61f:ffff:ffff:ffff:ffff:ffff:ffff
9921a0:620::/2821a0:62f:ffff:ffff:ffff:ffff:ffff:ffff
10021a0:630::/2821a0:63f:ffff:ffff:ffff:ffff:ffff:ffff
10121a0:640::/2821a0:64f:ffff:ffff:ffff:ffff:ffff:ffff
10221a0:650::/2821a0:65f:ffff:ffff:ffff:ffff:ffff:ffff
10321a0:660::/2821a0:66f:ffff:ffff:ffff:ffff:ffff:ffff
10421a0:670::/2821a0:67f:ffff:ffff:ffff:ffff:ffff:ffff
10521a0:680::/2821a0:68f:ffff:ffff:ffff:ffff:ffff:ffff
10621a0:690::/2821a0:69f:ffff:ffff:ffff:ffff:ffff:ffff
10721a0:6a0::/2821a0:6af:ffff:ffff:ffff:ffff:ffff:ffff
10821a0:6b0::/2821a0:6bf:ffff:ffff:ffff:ffff:ffff:ffff
10921a0:6c0::/2821a0:6cf:ffff:ffff:ffff:ffff:ffff:ffff
11021a0:6d0::/2821a0:6df:ffff:ffff:ffff:ffff:ffff:ffff
11121a0:6e0::/2821a0:6ef:ffff:ffff:ffff:ffff:ffff:ffff
11221a0:6f0::/2821a0:6ff:ffff:ffff:ffff:ffff:ffff:ffff
11321a0:700::/2821a0:70f:ffff:ffff:ffff:ffff:ffff:ffff
11421a0:710::/2821a0:71f:ffff:ffff:ffff:ffff:ffff:ffff
11521a0:720::/2821a0:72f:ffff:ffff:ffff:ffff:ffff:ffff
11621a0:730::/2821a0:73f:ffff:ffff:ffff:ffff:ffff:ffff
11721a0:740::/2821a0:74f:ffff:ffff:ffff:ffff:ffff:ffff
11821a0:750::/2821a0:75f:ffff:ffff:ffff:ffff:ffff:ffff
11921a0:760::/2821a0:76f:ffff:ffff:ffff:ffff:ffff:ffff
12021a0:770::/2821a0:77f:ffff:ffff:ffff:ffff:ffff:ffff
12121a0:780::/2821a0:78f:ffff:ffff:ffff:ffff:ffff:ffff
12221a0:790::/2821a0:79f:ffff:ffff:ffff:ffff:ffff:ffff
12321a0:7a0::/2821a0:7af:ffff:ffff:ffff:ffff:ffff:ffff
12421a0:7b0::/2821a0:7bf:ffff:ffff:ffff:ffff:ffff:ffff
12521a0:7c0::/2821a0:7cf:ffff:ffff:ffff:ffff:ffff:ffff
12621a0:7d0::/2821a0:7df:ffff:ffff:ffff:ffff:ffff:ffff
12721a0:7e0::/2821a0:7ef:ffff:ffff:ffff:ffff:ffff:ffff
12821a0:7f0::/2821a0:7ff:ffff:ffff:ffff:ffff:ffff:ffff
12921a0:800::/2821a0:80f:ffff:ffff:ffff:ffff:ffff:ffff
13021a0:810::/2821a0:81f:ffff:ffff:ffff:ffff:ffff:ffff
13121a0:820::/2821a0:82f:ffff:ffff:ffff:ffff:ffff:ffff
13221a0:830::/2821a0:83f:ffff:ffff:ffff:ffff:ffff:ffff
13321a0:840::/2821a0:84f:ffff:ffff:ffff:ffff:ffff:ffff
13421a0:850::/2821a0:85f:ffff:ffff:ffff:ffff:ffff:ffff
13521a0:860::/2821a0:86f:ffff:ffff:ffff:ffff:ffff:ffff
13621a0:870::/2821a0:87f:ffff:ffff:ffff:ffff:ffff:ffff
13721a0:880::/2821a0:88f:ffff:ffff:ffff:ffff:ffff:ffff
13821a0:890::/2821a0:89f:ffff:ffff:ffff:ffff:ffff:ffff
13921a0:8a0::/2821a0:8af:ffff:ffff:ffff:ffff:ffff:ffff
14021a0:8b0::/2821a0:8bf:ffff:ffff:ffff:ffff:ffff:ffff
14121a0:8c0::/2821a0:8cf:ffff:ffff:ffff:ffff:ffff:ffff
14221a0:8d0::/2821a0:8df:ffff:ffff:ffff:ffff:ffff:ffff
14321a0:8e0::/2821a0:8ef:ffff:ffff:ffff:ffff:ffff:ffff
14421a0:8f0::/2821a0:8ff:ffff:ffff:ffff:ffff:ffff:ffff
14521a0:900::/2821a0:90f:ffff:ffff:ffff:ffff:ffff:ffff
14621a0:910::/2821a0:91f:ffff:ffff:ffff:ffff:ffff:ffff
14721a0:920::/2821a0:92f:ffff:ffff:ffff:ffff:ffff:ffff
14821a0:930::/2821a0:93f:ffff:ffff:ffff:ffff:ffff:ffff
14921a0:940::/2821a0:94f:ffff:ffff:ffff:ffff:ffff:ffff
15021a0:950::/2821a0:95f:ffff:ffff:ffff:ffff:ffff:ffff
15121a0:960::/2821a0:96f:ffff:ffff:ffff:ffff:ffff:ffff
15221a0:970::/2821a0:97f:ffff:ffff:ffff:ffff:ffff:ffff
15321a0:980::/2821a0:98f:ffff:ffff:ffff:ffff:ffff:ffff
15421a0:990::/2821a0:99f:ffff:ffff:ffff:ffff:ffff:ffff
15521a0:9a0::/2821a0:9af:ffff:ffff:ffff:ffff:ffff:ffff
15621a0:9b0::/2821a0:9bf:ffff:ffff:ffff:ffff:ffff:ffff
15721a0:9c0::/2821a0:9cf:ffff:ffff:ffff:ffff:ffff:ffff
15821a0:9d0::/2821a0:9df:ffff:ffff:ffff:ffff:ffff:ffff
15921a0:9e0::/2821a0:9ef:ffff:ffff:ffff:ffff:ffff:ffff
16021a0:9f0::/2821a0:9ff:ffff:ffff:ffff:ffff:ffff:ffff
16121a0:a00::/2821a0:a0f:ffff:ffff:ffff:ffff:ffff:ffff
16221a0:a10::/2821a0:a1f:ffff:ffff:ffff:ffff:ffff:ffff
16321a0:a20::/2821a0:a2f:ffff:ffff:ffff:ffff:ffff:ffff
16421a0:a30::/2821a0:a3f:ffff:ffff:ffff:ffff:ffff:ffff
16521a0:a40::/2821a0:a4f:ffff:ffff:ffff:ffff:ffff:ffff
16621a0:a50::/2821a0:a5f:ffff:ffff:ffff:ffff:ffff:ffff
16721a0:a60::/2821a0:a6f:ffff:ffff:ffff:ffff:ffff:ffff
16821a0:a70::/2821a0:a7f:ffff:ffff:ffff:ffff:ffff:ffff
16921a0:a80::/2821a0:a8f:ffff:ffff:ffff:ffff:ffff:ffff
17021a0:a90::/2821a0:a9f:ffff:ffff:ffff:ffff:ffff:ffff
17121a0:aa0::/2821a0:aaf:ffff:ffff:ffff:ffff:ffff:ffff
17221a0:ab0::/2821a0:abf:ffff:ffff:ffff:ffff:ffff:ffff
17321a0:ac0::/2821a0:acf:ffff:ffff:ffff:ffff:ffff:ffff
17421a0:ad0::/2821a0:adf:ffff:ffff:ffff:ffff:ffff:ffff
17521a0:ae0::/2821a0:aef:ffff:ffff:ffff:ffff:ffff:ffff
17621a0:af0::/2821a0:aff:ffff:ffff:ffff:ffff:ffff:ffff
17721a0:b00::/2821a0:b0f:ffff:ffff:ffff:ffff:ffff:ffff
17821a0:b10::/2821a0:b1f:ffff:ffff:ffff:ffff:ffff:ffff
17921a0:b20::/2821a0:b2f:ffff:ffff:ffff:ffff:ffff:ffff
18021a0:b30::/2821a0:b3f:ffff:ffff:ffff:ffff:ffff:ffff
18121a0:b40::/2821a0:b4f:ffff:ffff:ffff:ffff:ffff:ffff
18221a0:b50::/2821a0:b5f:ffff:ffff:ffff:ffff:ffff:ffff
18321a0:b60::/2821a0:b6f:ffff:ffff:ffff:ffff:ffff:ffff
18421a0:b70::/2821a0:b7f:ffff:ffff:ffff:ffff:ffff:ffff
18521a0:b80::/2821a0:b8f:ffff:ffff:ffff:ffff:ffff:ffff
18621a0:b90::/2821a0:b9f:ffff:ffff:ffff:ffff:ffff:ffff
18721a0:ba0::/2821a0:baf:ffff:ffff:ffff:ffff:ffff:ffff
18821a0:bb0::/2821a0:bbf:ffff:ffff:ffff:ffff:ffff:ffff
18921a0:bc0::/2821a0:bcf:ffff:ffff:ffff:ffff:ffff:ffff
19021a0:bd0::/2821a0:bdf:ffff:ffff:ffff:ffff:ffff:ffff
19121a0:be0::/2821a0:bef:ffff:ffff:ffff:ffff:ffff:ffff
19221a0:bf0::/2821a0:bff:ffff:ffff:ffff:ffff:ffff:ffff
19321a0:c00::/2821a0:c0f:ffff:ffff:ffff:ffff:ffff:ffff
19421a0:c10::/2821a0:c1f:ffff:ffff:ffff:ffff:ffff:ffff
19521a0:c20::/2821a0:c2f:ffff:ffff:ffff:ffff:ffff:ffff
19621a0:c30::/2821a0:c3f:ffff:ffff:ffff:ffff:ffff:ffff
19721a0:c40::/2821a0:c4f:ffff:ffff:ffff:ffff:ffff:ffff
19821a0:c50::/2821a0:c5f:ffff:ffff:ffff:ffff:ffff:ffff
19921a0:c60::/2821a0:c6f:ffff:ffff:ffff:ffff:ffff:ffff
20021a0:c70::/2821a0:c7f:ffff:ffff:ffff:ffff:ffff:ffff
20121a0:c80::/2821a0:c8f:ffff:ffff:ffff:ffff:ffff:ffff
20221a0:c90::/2821a0:c9f:ffff:ffff:ffff:ffff:ffff:ffff
20321a0:ca0::/2821a0:caf:ffff:ffff:ffff:ffff:ffff:ffff
20421a0:cb0::/2821a0:cbf:ffff:ffff:ffff:ffff:ffff:ffff
20521a0:cc0::/2821a0:ccf:ffff:ffff:ffff:ffff:ffff:ffff
20621a0:cd0::/2821a0:cdf:ffff:ffff:ffff:ffff:ffff:ffff
20721a0:ce0::/2821a0:cef:ffff:ffff:ffff:ffff:ffff:ffff
20821a0:cf0::/2821a0:cff:ffff:ffff:ffff:ffff:ffff:ffff
20921a0:d00::/2821a0:d0f:ffff:ffff:ffff:ffff:ffff:ffff
21021a0:d10::/2821a0:d1f:ffff:ffff:ffff:ffff:ffff:ffff
21121a0:d20::/2821a0:d2f:ffff:ffff:ffff:ffff:ffff:ffff
21221a0:d30::/2821a0:d3f:ffff:ffff:ffff:ffff:ffff:ffff
21321a0:d40::/2821a0:d4f:ffff:ffff:ffff:ffff:ffff:ffff
21421a0:d50::/2821a0:d5f:ffff:ffff:ffff:ffff:ffff:ffff
21521a0:d60::/2821a0:d6f:ffff:ffff:ffff:ffff:ffff:ffff
21621a0:d70::/2821a0:d7f:ffff:ffff:ffff:ffff:ffff:ffff
21721a0:d80::/2821a0:d8f:ffff:ffff:ffff:ffff:ffff:ffff
21821a0:d90::/2821a0:d9f:ffff:ffff:ffff:ffff:ffff:ffff
21921a0:da0::/2821a0:daf:ffff:ffff:ffff:ffff:ffff:ffff
22021a0:db0::/2821a0:dbf:ffff:ffff:ffff:ffff:ffff:ffff
22121a0:dc0::/2821a0:dcf:ffff:ffff:ffff:ffff:ffff:ffff
22221a0:dd0::/2821a0:ddf:ffff:ffff:ffff:ffff:ffff:ffff
22321a0:de0::/2821a0:def:ffff:ffff:ffff:ffff:ffff:ffff
22421a0:df0::/2821a0:dff:ffff:ffff:ffff:ffff:ffff:ffff
22521a0:e00::/2821a0:e0f:ffff:ffff:ffff:ffff:ffff:ffff
22621a0:e10::/2821a0:e1f:ffff:ffff:ffff:ffff:ffff:ffff
22721a0:e20::/2821a0:e2f:ffff:ffff:ffff:ffff:ffff:ffff
22821a0:e30::/2821a0:e3f:ffff:ffff:ffff:ffff:ffff:ffff
22921a0:e40::/2821a0:e4f:ffff:ffff:ffff:ffff:ffff:ffff
23021a0:e50::/2821a0:e5f:ffff:ffff:ffff:ffff:ffff:ffff
23121a0:e60::/2821a0:e6f:ffff:ffff:ffff:ffff:ffff:ffff
23221a0:e70::/2821a0:e7f:ffff:ffff:ffff:ffff:ffff:ffff
23321a0:e80::/2821a0:e8f:ffff:ffff:ffff:ffff:ffff:ffff
23421a0:e90::/2821a0:e9f:ffff:ffff:ffff:ffff:ffff:ffff
23521a0:ea0::/2821a0:eaf:ffff:ffff:ffff:ffff:ffff:ffff
23621a0:eb0::/2821a0:ebf:ffff:ffff:ffff:ffff:ffff:ffff
23721a0:ec0::/2821a0:ecf:ffff:ffff:ffff:ffff:ffff:ffff
23821a0:ed0::/2821a0:edf:ffff:ffff:ffff:ffff:ffff:ffff
23921a0:ee0::/2821a0:eef:ffff:ffff:ffff:ffff:ffff:ffff
24021a0:ef0::/2821a0:eff:ffff:ffff:ffff:ffff:ffff:ffff
24121a0:f00::/2821a0:f0f:ffff:ffff:ffff:ffff:ffff:ffff
24221a0:f10::/2821a0:f1f:ffff:ffff:ffff:ffff:ffff:ffff
24321a0:f20::/2821a0:f2f:ffff:ffff:ffff:ffff:ffff:ffff
24421a0:f30::/2821a0:f3f:ffff:ffff:ffff:ffff:ffff:ffff
24521a0:f40::/2821a0:f4f:ffff:ffff:ffff:ffff:ffff:ffff
24621a0:f50::/2821a0:f5f:ffff:ffff:ffff:ffff:ffff:ffff
24721a0:f60::/2821a0:f6f:ffff:ffff:ffff:ffff:ffff:ffff
24821a0:f70::/2821a0:f7f:ffff:ffff:ffff:ffff:ffff:ffff
24921a0:f80::/2821a0:f8f:ffff:ffff:ffff:ffff:ffff:ffff
25021a0:f90::/2821a0:f9f:ffff:ffff:ffff:ffff:ffff:ffff
25121a0:fa0::/2821a0:faf:ffff:ffff:ffff:ffff:ffff:ffff
25221a0:fb0::/2821a0:fbf:ffff:ffff:ffff:ffff:ffff:ffff
25321a0:fc0::/2821a0:fcf:ffff:ffff:ffff:ffff:ffff:ffff
25421a0:fd0::/2821a0:fdf:ffff:ffff:ffff:ffff:ffff:ffff
25521a0:fe0::/2821a0:fef:ffff:ffff:ffff:ffff:ffff:ffff
25621a0:ff0::/2821a0: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.