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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.

Network236.0.78.0/23
Usable hosts510
Subnet mask255.255.254.0
Addresses512
Network address
236.0.78.0
Broadcast address
236.0.79.255
First usable
236.0.78.1
Last usable
236.0.79.254
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
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex EC004E00 · Integer 3959442944 to 3959443455
Reverse DNS zones
78.0.236.in-addr.arpa
79.0.236.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
Address11101100.00000000.01001110.00000000236.0.78.0
Subnet mask11111111.11111111.11111110.00000000255.255.254.0
Network11101100.00000000.01001110.00000000236.0.78.0
Broadcast11101100.00000000.01001111.11111111236.0.79.255
Split into smaller subnets/30
/24 (2)/25 (4)/26 (8)/27 (16)/28 (32)/29 (64)/30 (128)/31 (256)/32 (512)

236.0.78.0/23 makes 128 subnets of /30.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1236.0.78.0/30236.0.78.1 to 236.0.78.2236.0.78.32
2236.0.78.4/30236.0.78.5 to 236.0.78.6236.0.78.72
3236.0.78.8/30236.0.78.9 to 236.0.78.10236.0.78.112
4236.0.78.12/30236.0.78.13 to 236.0.78.14236.0.78.152
5236.0.78.16/30236.0.78.17 to 236.0.78.18236.0.78.192
6236.0.78.20/30236.0.78.21 to 236.0.78.22236.0.78.232
7236.0.78.24/30236.0.78.25 to 236.0.78.26236.0.78.272
8236.0.78.28/30236.0.78.29 to 236.0.78.30236.0.78.312
9236.0.78.32/30236.0.78.33 to 236.0.78.34236.0.78.352
10236.0.78.36/30236.0.78.37 to 236.0.78.38236.0.78.392
11236.0.78.40/30236.0.78.41 to 236.0.78.42236.0.78.432
12236.0.78.44/30236.0.78.45 to 236.0.78.46236.0.78.472
13236.0.78.48/30236.0.78.49 to 236.0.78.50236.0.78.512
14236.0.78.52/30236.0.78.53 to 236.0.78.54236.0.78.552
15236.0.78.56/30236.0.78.57 to 236.0.78.58236.0.78.592
16236.0.78.60/30236.0.78.61 to 236.0.78.62236.0.78.632
17236.0.78.64/30236.0.78.65 to 236.0.78.66236.0.78.672
18236.0.78.68/30236.0.78.69 to 236.0.78.70236.0.78.712
19236.0.78.72/30236.0.78.73 to 236.0.78.74236.0.78.752
20236.0.78.76/30236.0.78.77 to 236.0.78.78236.0.78.792
21236.0.78.80/30236.0.78.81 to 236.0.78.82236.0.78.832
22236.0.78.84/30236.0.78.85 to 236.0.78.86236.0.78.872
23236.0.78.88/30236.0.78.89 to 236.0.78.90236.0.78.912
24236.0.78.92/30236.0.78.93 to 236.0.78.94236.0.78.952
25236.0.78.96/30236.0.78.97 to 236.0.78.98236.0.78.992
26236.0.78.100/30236.0.78.101 to 236.0.78.102236.0.78.1032
27236.0.78.104/30236.0.78.105 to 236.0.78.106236.0.78.1072
28236.0.78.108/30236.0.78.109 to 236.0.78.110236.0.78.1112
29236.0.78.112/30236.0.78.113 to 236.0.78.114236.0.78.1152
30236.0.78.116/30236.0.78.117 to 236.0.78.118236.0.78.1192
31236.0.78.120/30236.0.78.121 to 236.0.78.122236.0.78.1232
32236.0.78.124/30236.0.78.125 to 236.0.78.126236.0.78.1272
33236.0.78.128/30236.0.78.129 to 236.0.78.130236.0.78.1312
34236.0.78.132/30236.0.78.133 to 236.0.78.134236.0.78.1352
35236.0.78.136/30236.0.78.137 to 236.0.78.138236.0.78.1392
36236.0.78.140/30236.0.78.141 to 236.0.78.142236.0.78.1432
37236.0.78.144/30236.0.78.145 to 236.0.78.146236.0.78.1472
38236.0.78.148/30236.0.78.149 to 236.0.78.150236.0.78.1512
39236.0.78.152/30236.0.78.153 to 236.0.78.154236.0.78.1552
40236.0.78.156/30236.0.78.157 to 236.0.78.158236.0.78.1592
41236.0.78.160/30236.0.78.161 to 236.0.78.162236.0.78.1632
42236.0.78.164/30236.0.78.165 to 236.0.78.166236.0.78.1672
43236.0.78.168/30236.0.78.169 to 236.0.78.170236.0.78.1712
44236.0.78.172/30236.0.78.173 to 236.0.78.174236.0.78.1752
45236.0.78.176/30236.0.78.177 to 236.0.78.178236.0.78.1792
46236.0.78.180/30236.0.78.181 to 236.0.78.182236.0.78.1832
47236.0.78.184/30236.0.78.185 to 236.0.78.186236.0.78.1872
48236.0.78.188/30236.0.78.189 to 236.0.78.190236.0.78.1912
49236.0.78.192/30236.0.78.193 to 236.0.78.194236.0.78.1952
50236.0.78.196/30236.0.78.197 to 236.0.78.198236.0.78.1992
51236.0.78.200/30236.0.78.201 to 236.0.78.202236.0.78.2032
52236.0.78.204/30236.0.78.205 to 236.0.78.206236.0.78.2072
53236.0.78.208/30236.0.78.209 to 236.0.78.210236.0.78.2112
54236.0.78.212/30236.0.78.213 to 236.0.78.214236.0.78.2152
55236.0.78.216/30236.0.78.217 to 236.0.78.218236.0.78.2192
56236.0.78.220/30236.0.78.221 to 236.0.78.222236.0.78.2232
57236.0.78.224/30236.0.78.225 to 236.0.78.226236.0.78.2272
58236.0.78.228/30236.0.78.229 to 236.0.78.230236.0.78.2312
59236.0.78.232/30236.0.78.233 to 236.0.78.234236.0.78.2352
60236.0.78.236/30236.0.78.237 to 236.0.78.238236.0.78.2392
61236.0.78.240/30236.0.78.241 to 236.0.78.242236.0.78.2432
62236.0.78.244/30236.0.78.245 to 236.0.78.246236.0.78.2472
63236.0.78.248/30236.0.78.249 to 236.0.78.250236.0.78.2512
64236.0.78.252/30236.0.78.253 to 236.0.78.254236.0.78.2552
65236.0.79.0/30236.0.79.1 to 236.0.79.2236.0.79.32
66236.0.79.4/30236.0.79.5 to 236.0.79.6236.0.79.72
67236.0.79.8/30236.0.79.9 to 236.0.79.10236.0.79.112
68236.0.79.12/30236.0.79.13 to 236.0.79.14236.0.79.152
69236.0.79.16/30236.0.79.17 to 236.0.79.18236.0.79.192
70236.0.79.20/30236.0.79.21 to 236.0.79.22236.0.79.232
71236.0.79.24/30236.0.79.25 to 236.0.79.26236.0.79.272
72236.0.79.28/30236.0.79.29 to 236.0.79.30236.0.79.312
73236.0.79.32/30236.0.79.33 to 236.0.79.34236.0.79.352
74236.0.79.36/30236.0.79.37 to 236.0.79.38236.0.79.392
75236.0.79.40/30236.0.79.41 to 236.0.79.42236.0.79.432
76236.0.79.44/30236.0.79.45 to 236.0.79.46236.0.79.472
77236.0.79.48/30236.0.79.49 to 236.0.79.50236.0.79.512
78236.0.79.52/30236.0.79.53 to 236.0.79.54236.0.79.552
79236.0.79.56/30236.0.79.57 to 236.0.79.58236.0.79.592
80236.0.79.60/30236.0.79.61 to 236.0.79.62236.0.79.632
81236.0.79.64/30236.0.79.65 to 236.0.79.66236.0.79.672
82236.0.79.68/30236.0.79.69 to 236.0.79.70236.0.79.712
83236.0.79.72/30236.0.79.73 to 236.0.79.74236.0.79.752
84236.0.79.76/30236.0.79.77 to 236.0.79.78236.0.79.792
85236.0.79.80/30236.0.79.81 to 236.0.79.82236.0.79.832
86236.0.79.84/30236.0.79.85 to 236.0.79.86236.0.79.872
87236.0.79.88/30236.0.79.89 to 236.0.79.90236.0.79.912
88236.0.79.92/30236.0.79.93 to 236.0.79.94236.0.79.952
89236.0.79.96/30236.0.79.97 to 236.0.79.98236.0.79.992
90236.0.79.100/30236.0.79.101 to 236.0.79.102236.0.79.1032
91236.0.79.104/30236.0.79.105 to 236.0.79.106236.0.79.1072
92236.0.79.108/30236.0.79.109 to 236.0.79.110236.0.79.1112
93236.0.79.112/30236.0.79.113 to 236.0.79.114236.0.79.1152
94236.0.79.116/30236.0.79.117 to 236.0.79.118236.0.79.1192
95236.0.79.120/30236.0.79.121 to 236.0.79.122236.0.79.1232
96236.0.79.124/30236.0.79.125 to 236.0.79.126236.0.79.1272
97236.0.79.128/30236.0.79.129 to 236.0.79.130236.0.79.1312
98236.0.79.132/30236.0.79.133 to 236.0.79.134236.0.79.1352
99236.0.79.136/30236.0.79.137 to 236.0.79.138236.0.79.1392
100236.0.79.140/30236.0.79.141 to 236.0.79.142236.0.79.1432
101236.0.79.144/30236.0.79.145 to 236.0.79.146236.0.79.1472
102236.0.79.148/30236.0.79.149 to 236.0.79.150236.0.79.1512
103236.0.79.152/30236.0.79.153 to 236.0.79.154236.0.79.1552
104236.0.79.156/30236.0.79.157 to 236.0.79.158236.0.79.1592
105236.0.79.160/30236.0.79.161 to 236.0.79.162236.0.79.1632
106236.0.79.164/30236.0.79.165 to 236.0.79.166236.0.79.1672
107236.0.79.168/30236.0.79.169 to 236.0.79.170236.0.79.1712
108236.0.79.172/30236.0.79.173 to 236.0.79.174236.0.79.1752
109236.0.79.176/30236.0.79.177 to 236.0.79.178236.0.79.1792
110236.0.79.180/30236.0.79.181 to 236.0.79.182236.0.79.1832
111236.0.79.184/30236.0.79.185 to 236.0.79.186236.0.79.1872
112236.0.79.188/30236.0.79.189 to 236.0.79.190236.0.79.1912
113236.0.79.192/30236.0.79.193 to 236.0.79.194236.0.79.1952
114236.0.79.196/30236.0.79.197 to 236.0.79.198236.0.79.1992
115236.0.79.200/30236.0.79.201 to 236.0.79.202236.0.79.2032
116236.0.79.204/30236.0.79.205 to 236.0.79.206236.0.79.2072
117236.0.79.208/30236.0.79.209 to 236.0.79.210236.0.79.2112
118236.0.79.212/30236.0.79.213 to 236.0.79.214236.0.79.2152
119236.0.79.216/30236.0.79.217 to 236.0.79.218236.0.79.2192
120236.0.79.220/30236.0.79.221 to 236.0.79.222236.0.79.2232
121236.0.79.224/30236.0.79.225 to 236.0.79.226236.0.79.2272
122236.0.79.228/30236.0.79.229 to 236.0.79.230236.0.79.2312
123236.0.79.232/30236.0.79.233 to 236.0.79.234236.0.79.2352
124236.0.79.236/30236.0.79.237 to 236.0.79.238236.0.79.2392
125236.0.79.240/30236.0.79.241 to 236.0.79.242236.0.79.2432
126236.0.79.244/30236.0.79.245 to 236.0.79.246236.0.79.2472
127236.0.79.248/30236.0.79.249 to 236.0.79.250236.0.79.2512
128236.0.79.252/30236.0.79.253 to 236.0.79.254236.0.79.2552

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.