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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.

Network36.2.6.0/23
Usable hosts510
Subnet mask255.255.254.0
Addresses512
Network address
36.2.6.0
Broadcast address
36.2.7.255
First usable
36.2.6.1
Last usable
36.2.7.254
Usable hosts
510 (512 less the network and broadcast addresses)
Subnet mask
255.255.254.0
Wildcard mask
0.0.1.255 (Cisco ACLs, OSPF)
Prefix length
/23
Type
Public public
Old class
A (default /8)
As numbers
Hex 24020600 · Integer 604112384 to 604112895
Reverse DNS zones
6.2.36.in-addr.arpa
7.2.36.in-addr.arpa
/23 is not on a 8-bit boundary, so it takes 2 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00100100.00000010.00000110.0000000036.2.6.0
Subnet mask11111111.11111111.11111110.00000000255.255.254.0
Network00100100.00000010.00000110.0000000036.2.6.0
Broadcast00100100.00000010.00000111.1111111136.2.7.255
Split into smaller subnets/29
/24 (2)/25 (4)/26 (8)/27 (16)/28 (32)/29 (64)/30 (128)/31 (256)/32 (512)

36.2.6.0/23 makes 64 subnets of /29.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
136.2.6.0/2936.2.6.1 to 36.2.6.636.2.6.76
236.2.6.8/2936.2.6.9 to 36.2.6.1436.2.6.156
336.2.6.16/2936.2.6.17 to 36.2.6.2236.2.6.236
436.2.6.24/2936.2.6.25 to 36.2.6.3036.2.6.316
536.2.6.32/2936.2.6.33 to 36.2.6.3836.2.6.396
636.2.6.40/2936.2.6.41 to 36.2.6.4636.2.6.476
736.2.6.48/2936.2.6.49 to 36.2.6.5436.2.6.556
836.2.6.56/2936.2.6.57 to 36.2.6.6236.2.6.636
936.2.6.64/2936.2.6.65 to 36.2.6.7036.2.6.716
1036.2.6.72/2936.2.6.73 to 36.2.6.7836.2.6.796
1136.2.6.80/2936.2.6.81 to 36.2.6.8636.2.6.876
1236.2.6.88/2936.2.6.89 to 36.2.6.9436.2.6.956
1336.2.6.96/2936.2.6.97 to 36.2.6.10236.2.6.1036
1436.2.6.104/2936.2.6.105 to 36.2.6.11036.2.6.1116
1536.2.6.112/2936.2.6.113 to 36.2.6.11836.2.6.1196
1636.2.6.120/2936.2.6.121 to 36.2.6.12636.2.6.1276
1736.2.6.128/2936.2.6.129 to 36.2.6.13436.2.6.1356
1836.2.6.136/2936.2.6.137 to 36.2.6.14236.2.6.1436
1936.2.6.144/2936.2.6.145 to 36.2.6.15036.2.6.1516
2036.2.6.152/2936.2.6.153 to 36.2.6.15836.2.6.1596
2136.2.6.160/2936.2.6.161 to 36.2.6.16636.2.6.1676
2236.2.6.168/2936.2.6.169 to 36.2.6.17436.2.6.1756
2336.2.6.176/2936.2.6.177 to 36.2.6.18236.2.6.1836
2436.2.6.184/2936.2.6.185 to 36.2.6.19036.2.6.1916
2536.2.6.192/2936.2.6.193 to 36.2.6.19836.2.6.1996
2636.2.6.200/2936.2.6.201 to 36.2.6.20636.2.6.2076
2736.2.6.208/2936.2.6.209 to 36.2.6.21436.2.6.2156
2836.2.6.216/2936.2.6.217 to 36.2.6.22236.2.6.2236
2936.2.6.224/2936.2.6.225 to 36.2.6.23036.2.6.2316
3036.2.6.232/2936.2.6.233 to 36.2.6.23836.2.6.2396
3136.2.6.240/2936.2.6.241 to 36.2.6.24636.2.6.2476
3236.2.6.248/2936.2.6.249 to 36.2.6.25436.2.6.2556
3336.2.7.0/2936.2.7.1 to 36.2.7.636.2.7.76
3436.2.7.8/2936.2.7.9 to 36.2.7.1436.2.7.156
3536.2.7.16/2936.2.7.17 to 36.2.7.2236.2.7.236
3636.2.7.24/2936.2.7.25 to 36.2.7.3036.2.7.316
3736.2.7.32/2936.2.7.33 to 36.2.7.3836.2.7.396
3836.2.7.40/2936.2.7.41 to 36.2.7.4636.2.7.476
3936.2.7.48/2936.2.7.49 to 36.2.7.5436.2.7.556
4036.2.7.56/2936.2.7.57 to 36.2.7.6236.2.7.636
4136.2.7.64/2936.2.7.65 to 36.2.7.7036.2.7.716
4236.2.7.72/2936.2.7.73 to 36.2.7.7836.2.7.796
4336.2.7.80/2936.2.7.81 to 36.2.7.8636.2.7.876
4436.2.7.88/2936.2.7.89 to 36.2.7.9436.2.7.956
4536.2.7.96/2936.2.7.97 to 36.2.7.10236.2.7.1036
4636.2.7.104/2936.2.7.105 to 36.2.7.11036.2.7.1116
4736.2.7.112/2936.2.7.113 to 36.2.7.11836.2.7.1196
4836.2.7.120/2936.2.7.121 to 36.2.7.12636.2.7.1276
4936.2.7.128/2936.2.7.129 to 36.2.7.13436.2.7.1356
5036.2.7.136/2936.2.7.137 to 36.2.7.14236.2.7.1436
5136.2.7.144/2936.2.7.145 to 36.2.7.15036.2.7.1516
5236.2.7.152/2936.2.7.153 to 36.2.7.15836.2.7.1596
5336.2.7.160/2936.2.7.161 to 36.2.7.16636.2.7.1676
5436.2.7.168/2936.2.7.169 to 36.2.7.17436.2.7.1756
5536.2.7.176/2936.2.7.177 to 36.2.7.18236.2.7.1836
5636.2.7.184/2936.2.7.185 to 36.2.7.19036.2.7.1916
5736.2.7.192/2936.2.7.193 to 36.2.7.19836.2.7.1996
5836.2.7.200/2936.2.7.201 to 36.2.7.20636.2.7.2076
5936.2.7.208/2936.2.7.209 to 36.2.7.21436.2.7.2156
6036.2.7.216/2936.2.7.217 to 36.2.7.22236.2.7.2236
6136.2.7.224/2936.2.7.225 to 36.2.7.23036.2.7.2316
6236.2.7.232/2936.2.7.233 to 36.2.7.23836.2.7.2396
6336.2.7.240/2936.2.7.241 to 36.2.7.24636.2.7.2476
6436.2.7.248/2936.2.7.249 to 36.2.7.25436.2.7.2556

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.