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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/120
Addresses256
/64 networksPart of one
Network
2001:db8::c400/120
First address
2001:db8::c400
Last address
2001:db8::c4ff
Addresses
256
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
2001:0db8:0000:0000:0000:0000:0000:c400
Type
Documentation 2001:db8::/32
For examples; never used on a network
Reverse DNS zone
4.c.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
Split into smaller subnets/128
/121 (2)/122 (4)/123 (8)/124 (16)/127 (128)/128 (256)

2001:db8::c400/120 makes 256 subnets of /128.

Subnets
#SubnetLast address
12001:db8::c400/1282001:db8::c400
22001:db8::c401/1282001:db8::c401
32001:db8::c402/1282001:db8::c402
42001:db8::c403/1282001:db8::c403
52001:db8::c404/1282001:db8::c404
62001:db8::c405/1282001:db8::c405
72001:db8::c406/1282001:db8::c406
82001:db8::c407/1282001:db8::c407
92001:db8::c408/1282001:db8::c408
102001:db8::c409/1282001:db8::c409
112001:db8::c40a/1282001:db8::c40a
122001:db8::c40b/1282001:db8::c40b
132001:db8::c40c/1282001:db8::c40c
142001:db8::c40d/1282001:db8::c40d
152001:db8::c40e/1282001:db8::c40e
162001:db8::c40f/1282001:db8::c40f
172001:db8::c410/1282001:db8::c410
182001:db8::c411/1282001:db8::c411
192001:db8::c412/1282001:db8::c412
202001:db8::c413/1282001:db8::c413
212001:db8::c414/1282001:db8::c414
222001:db8::c415/1282001:db8::c415
232001:db8::c416/1282001:db8::c416
242001:db8::c417/1282001:db8::c417
252001:db8::c418/1282001:db8::c418
262001:db8::c419/1282001:db8::c419
272001:db8::c41a/1282001:db8::c41a
282001:db8::c41b/1282001:db8::c41b
292001:db8::c41c/1282001:db8::c41c
302001:db8::c41d/1282001:db8::c41d
312001:db8::c41e/1282001:db8::c41e
322001:db8::c41f/1282001:db8::c41f
332001:db8::c420/1282001:db8::c420
342001:db8::c421/1282001:db8::c421
352001:db8::c422/1282001:db8::c422
362001:db8::c423/1282001:db8::c423
372001:db8::c424/1282001:db8::c424
382001:db8::c425/1282001:db8::c425
392001:db8::c426/1282001:db8::c426
402001:db8::c427/1282001:db8::c427
412001:db8::c428/1282001:db8::c428
422001:db8::c429/1282001:db8::c429
432001:db8::c42a/1282001:db8::c42a
442001:db8::c42b/1282001:db8::c42b
452001:db8::c42c/1282001:db8::c42c
462001:db8::c42d/1282001:db8::c42d
472001:db8::c42e/1282001:db8::c42e
482001:db8::c42f/1282001:db8::c42f
492001:db8::c430/1282001:db8::c430
502001:db8::c431/1282001:db8::c431
512001:db8::c432/1282001:db8::c432
522001:db8::c433/1282001:db8::c433
532001:db8::c434/1282001:db8::c434
542001:db8::c435/1282001:db8::c435
552001:db8::c436/1282001:db8::c436
562001:db8::c437/1282001:db8::c437
572001:db8::c438/1282001:db8::c438
582001:db8::c439/1282001:db8::c439
592001:db8::c43a/1282001:db8::c43a
602001:db8::c43b/1282001:db8::c43b
612001:db8::c43c/1282001:db8::c43c
622001:db8::c43d/1282001:db8::c43d
632001:db8::c43e/1282001:db8::c43e
642001:db8::c43f/1282001:db8::c43f
652001:db8::c440/1282001:db8::c440
662001:db8::c441/1282001:db8::c441
672001:db8::c442/1282001:db8::c442
682001:db8::c443/1282001:db8::c443
692001:db8::c444/1282001:db8::c444
702001:db8::c445/1282001:db8::c445
712001:db8::c446/1282001:db8::c446
722001:db8::c447/1282001:db8::c447
732001:db8::c448/1282001:db8::c448
742001:db8::c449/1282001:db8::c449
752001:db8::c44a/1282001:db8::c44a
762001:db8::c44b/1282001:db8::c44b
772001:db8::c44c/1282001:db8::c44c
782001:db8::c44d/1282001:db8::c44d
792001:db8::c44e/1282001:db8::c44e
802001:db8::c44f/1282001:db8::c44f
812001:db8::c450/1282001:db8::c450
822001:db8::c451/1282001:db8::c451
832001:db8::c452/1282001:db8::c452
842001:db8::c453/1282001:db8::c453
852001:db8::c454/1282001:db8::c454
862001:db8::c455/1282001:db8::c455
872001:db8::c456/1282001:db8::c456
882001:db8::c457/1282001:db8::c457
892001:db8::c458/1282001:db8::c458
902001:db8::c459/1282001:db8::c459
912001:db8::c45a/1282001:db8::c45a
922001:db8::c45b/1282001:db8::c45b
932001:db8::c45c/1282001:db8::c45c
942001:db8::c45d/1282001:db8::c45d
952001:db8::c45e/1282001:db8::c45e
962001:db8::c45f/1282001:db8::c45f
972001:db8::c460/1282001:db8::c460
982001:db8::c461/1282001:db8::c461
992001:db8::c462/1282001:db8::c462
1002001:db8::c463/1282001:db8::c463
1012001:db8::c464/1282001:db8::c464
1022001:db8::c465/1282001:db8::c465
1032001:db8::c466/1282001:db8::c466
1042001:db8::c467/1282001:db8::c467
1052001:db8::c468/1282001:db8::c468
1062001:db8::c469/1282001:db8::c469
1072001:db8::c46a/1282001:db8::c46a
1082001:db8::c46b/1282001:db8::c46b
1092001:db8::c46c/1282001:db8::c46c
1102001:db8::c46d/1282001:db8::c46d
1112001:db8::c46e/1282001:db8::c46e
1122001:db8::c46f/1282001:db8::c46f
1132001:db8::c470/1282001:db8::c470
1142001:db8::c471/1282001:db8::c471
1152001:db8::c472/1282001:db8::c472
1162001:db8::c473/1282001:db8::c473
1172001:db8::c474/1282001:db8::c474
1182001:db8::c475/1282001:db8::c475
1192001:db8::c476/1282001:db8::c476
1202001:db8::c477/1282001:db8::c477
1212001:db8::c478/1282001:db8::c478
1222001:db8::c479/1282001:db8::c479
1232001:db8::c47a/1282001:db8::c47a
1242001:db8::c47b/1282001:db8::c47b
1252001:db8::c47c/1282001:db8::c47c
1262001:db8::c47d/1282001:db8::c47d
1272001:db8::c47e/1282001:db8::c47e
1282001:db8::c47f/1282001:db8::c47f
1292001:db8::c480/1282001:db8::c480
1302001:db8::c481/1282001:db8::c481
1312001:db8::c482/1282001:db8::c482
1322001:db8::c483/1282001:db8::c483
1332001:db8::c484/1282001:db8::c484
1342001:db8::c485/1282001:db8::c485
1352001:db8::c486/1282001:db8::c486
1362001:db8::c487/1282001:db8::c487
1372001:db8::c488/1282001:db8::c488
1382001:db8::c489/1282001:db8::c489
1392001:db8::c48a/1282001:db8::c48a
1402001:db8::c48b/1282001:db8::c48b
1412001:db8::c48c/1282001:db8::c48c
1422001:db8::c48d/1282001:db8::c48d
1432001:db8::c48e/1282001:db8::c48e
1442001:db8::c48f/1282001:db8::c48f
1452001:db8::c490/1282001:db8::c490
1462001:db8::c491/1282001:db8::c491
1472001:db8::c492/1282001:db8::c492
1482001:db8::c493/1282001:db8::c493
1492001:db8::c494/1282001:db8::c494
1502001:db8::c495/1282001:db8::c495
1512001:db8::c496/1282001:db8::c496
1522001:db8::c497/1282001:db8::c497
1532001:db8::c498/1282001:db8::c498
1542001:db8::c499/1282001:db8::c499
1552001:db8::c49a/1282001:db8::c49a
1562001:db8::c49b/1282001:db8::c49b
1572001:db8::c49c/1282001:db8::c49c
1582001:db8::c49d/1282001:db8::c49d
1592001:db8::c49e/1282001:db8::c49e
1602001:db8::c49f/1282001:db8::c49f
1612001:db8::c4a0/1282001:db8::c4a0
1622001:db8::c4a1/1282001:db8::c4a1
1632001:db8::c4a2/1282001:db8::c4a2
1642001:db8::c4a3/1282001:db8::c4a3
1652001:db8::c4a4/1282001:db8::c4a4
1662001:db8::c4a5/1282001:db8::c4a5
1672001:db8::c4a6/1282001:db8::c4a6
1682001:db8::c4a7/1282001:db8::c4a7
1692001:db8::c4a8/1282001:db8::c4a8
1702001:db8::c4a9/1282001:db8::c4a9
1712001:db8::c4aa/1282001:db8::c4aa
1722001:db8::c4ab/1282001:db8::c4ab
1732001:db8::c4ac/1282001:db8::c4ac
1742001:db8::c4ad/1282001:db8::c4ad
1752001:db8::c4ae/1282001:db8::c4ae
1762001:db8::c4af/1282001:db8::c4af
1772001:db8::c4b0/1282001:db8::c4b0
1782001:db8::c4b1/1282001:db8::c4b1
1792001:db8::c4b2/1282001:db8::c4b2
1802001:db8::c4b3/1282001:db8::c4b3
1812001:db8::c4b4/1282001:db8::c4b4
1822001:db8::c4b5/1282001:db8::c4b5
1832001:db8::c4b6/1282001:db8::c4b6
1842001:db8::c4b7/1282001:db8::c4b7
1852001:db8::c4b8/1282001:db8::c4b8
1862001:db8::c4b9/1282001:db8::c4b9
1872001:db8::c4ba/1282001:db8::c4ba
1882001:db8::c4bb/1282001:db8::c4bb
1892001:db8::c4bc/1282001:db8::c4bc
1902001:db8::c4bd/1282001:db8::c4bd
1912001:db8::c4be/1282001:db8::c4be
1922001:db8::c4bf/1282001:db8::c4bf
1932001:db8::c4c0/1282001:db8::c4c0
1942001:db8::c4c1/1282001:db8::c4c1
1952001:db8::c4c2/1282001:db8::c4c2
1962001:db8::c4c3/1282001:db8::c4c3
1972001:db8::c4c4/1282001:db8::c4c4
1982001:db8::c4c5/1282001:db8::c4c5
1992001:db8::c4c6/1282001:db8::c4c6
2002001:db8::c4c7/1282001:db8::c4c7
2012001:db8::c4c8/1282001:db8::c4c8
2022001:db8::c4c9/1282001:db8::c4c9
2032001:db8::c4ca/1282001:db8::c4ca
2042001:db8::c4cb/1282001:db8::c4cb
2052001:db8::c4cc/1282001:db8::c4cc
2062001:db8::c4cd/1282001:db8::c4cd
2072001:db8::c4ce/1282001:db8::c4ce
2082001:db8::c4cf/1282001:db8::c4cf
2092001:db8::c4d0/1282001:db8::c4d0
2102001:db8::c4d1/1282001:db8::c4d1
2112001:db8::c4d2/1282001:db8::c4d2
2122001:db8::c4d3/1282001:db8::c4d3
2132001:db8::c4d4/1282001:db8::c4d4
2142001:db8::c4d5/1282001:db8::c4d5
2152001:db8::c4d6/1282001:db8::c4d6
2162001:db8::c4d7/1282001:db8::c4d7
2172001:db8::c4d8/1282001:db8::c4d8
2182001:db8::c4d9/1282001:db8::c4d9
2192001:db8::c4da/1282001:db8::c4da
2202001:db8::c4db/1282001:db8::c4db
2212001:db8::c4dc/1282001:db8::c4dc
2222001:db8::c4dd/1282001:db8::c4dd
2232001:db8::c4de/1282001:db8::c4de
2242001:db8::c4df/1282001:db8::c4df
2252001:db8::c4e0/1282001:db8::c4e0
2262001:db8::c4e1/1282001:db8::c4e1
2272001:db8::c4e2/1282001:db8::c4e2
2282001:db8::c4e3/1282001:db8::c4e3
2292001:db8::c4e4/1282001:db8::c4e4
2302001:db8::c4e5/1282001:db8::c4e5
2312001:db8::c4e6/1282001:db8::c4e6
2322001:db8::c4e7/1282001:db8::c4e7
2332001:db8::c4e8/1282001:db8::c4e8
2342001:db8::c4e9/1282001:db8::c4e9
2352001:db8::c4ea/1282001:db8::c4ea
2362001:db8::c4eb/1282001:db8::c4eb
2372001:db8::c4ec/1282001:db8::c4ec
2382001:db8::c4ed/1282001:db8::c4ed
2392001:db8::c4ee/1282001:db8::c4ee
2402001:db8::c4ef/1282001:db8::c4ef
2412001:db8::c4f0/1282001:db8::c4f0
2422001:db8::c4f1/1282001:db8::c4f1
2432001:db8::c4f2/1282001:db8::c4f2
2442001:db8::c4f3/1282001:db8::c4f3
2452001:db8::c4f4/1282001:db8::c4f4
2462001:db8::c4f5/1282001:db8::c4f5
2472001:db8::c4f6/1282001:db8::c4f6
2482001:db8::c4f7/1282001:db8::c4f7
2492001:db8::c4f8/1282001:db8::c4f8
2502001:db8::c4f9/1282001:db8::c4f9
2512001:db8::c4fa/1282001:db8::c4fa
2522001:db8::c4fb/1282001:db8::c4fb
2532001:db8::c4fc/1282001:db8::c4fc
2542001:db8::c4fd/1282001:db8::c4fd
2552001:db8::c4fe/1282001:db8::c4fe
2562001:db8::c4ff/1282001:db8::c4ff

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.