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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.

Network18.97.210.0/23
Usable hosts510
Subnet mask255.255.254.0
Addresses512
Network address
18.97.210.0
Broadcast address
18.97.211.255
First usable
18.97.210.1
Last usable
18.97.211.254
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 1261D200 · Integer 308400640 to 308401151
Reverse DNS zones
210.97.18.in-addr.arpa
211.97.18.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
Address00010010.01100001.11010010.0000000018.97.210.0
Subnet mask11111111.11111111.11111110.00000000255.255.254.0
Network00010010.01100001.11010010.0000000018.97.210.0
Broadcast00010010.01100001.11010011.1111111118.97.211.255
Split into smaller subnets/30
/24 (2)/25 (4)/26 (8)/27 (16)/28 (32)/29 (64)/30 (128)/31 (256)/32 (512)

18.97.210.0/23 makes 128 subnets of /30.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
118.97.210.0/3018.97.210.1 to 18.97.210.218.97.210.32
218.97.210.4/3018.97.210.5 to 18.97.210.618.97.210.72
318.97.210.8/3018.97.210.9 to 18.97.210.1018.97.210.112
418.97.210.12/3018.97.210.13 to 18.97.210.1418.97.210.152
518.97.210.16/3018.97.210.17 to 18.97.210.1818.97.210.192
618.97.210.20/3018.97.210.21 to 18.97.210.2218.97.210.232
718.97.210.24/3018.97.210.25 to 18.97.210.2618.97.210.272
818.97.210.28/3018.97.210.29 to 18.97.210.3018.97.210.312
918.97.210.32/3018.97.210.33 to 18.97.210.3418.97.210.352
1018.97.210.36/3018.97.210.37 to 18.97.210.3818.97.210.392
1118.97.210.40/3018.97.210.41 to 18.97.210.4218.97.210.432
1218.97.210.44/3018.97.210.45 to 18.97.210.4618.97.210.472
1318.97.210.48/3018.97.210.49 to 18.97.210.5018.97.210.512
1418.97.210.52/3018.97.210.53 to 18.97.210.5418.97.210.552
1518.97.210.56/3018.97.210.57 to 18.97.210.5818.97.210.592
1618.97.210.60/3018.97.210.61 to 18.97.210.6218.97.210.632
1718.97.210.64/3018.97.210.65 to 18.97.210.6618.97.210.672
1818.97.210.68/3018.97.210.69 to 18.97.210.7018.97.210.712
1918.97.210.72/3018.97.210.73 to 18.97.210.7418.97.210.752
2018.97.210.76/3018.97.210.77 to 18.97.210.7818.97.210.792
2118.97.210.80/3018.97.210.81 to 18.97.210.8218.97.210.832
2218.97.210.84/3018.97.210.85 to 18.97.210.8618.97.210.872
2318.97.210.88/3018.97.210.89 to 18.97.210.9018.97.210.912
2418.97.210.92/3018.97.210.93 to 18.97.210.9418.97.210.952
2518.97.210.96/3018.97.210.97 to 18.97.210.9818.97.210.992
2618.97.210.100/3018.97.210.101 to 18.97.210.10218.97.210.1032
2718.97.210.104/3018.97.210.105 to 18.97.210.10618.97.210.1072
2818.97.210.108/3018.97.210.109 to 18.97.210.11018.97.210.1112
2918.97.210.112/3018.97.210.113 to 18.97.210.11418.97.210.1152
3018.97.210.116/3018.97.210.117 to 18.97.210.11818.97.210.1192
3118.97.210.120/3018.97.210.121 to 18.97.210.12218.97.210.1232
3218.97.210.124/3018.97.210.125 to 18.97.210.12618.97.210.1272
3318.97.210.128/3018.97.210.129 to 18.97.210.13018.97.210.1312
3418.97.210.132/3018.97.210.133 to 18.97.210.13418.97.210.1352
3518.97.210.136/3018.97.210.137 to 18.97.210.13818.97.210.1392
3618.97.210.140/3018.97.210.141 to 18.97.210.14218.97.210.1432
3718.97.210.144/3018.97.210.145 to 18.97.210.14618.97.210.1472
3818.97.210.148/3018.97.210.149 to 18.97.210.15018.97.210.1512
3918.97.210.152/3018.97.210.153 to 18.97.210.15418.97.210.1552
4018.97.210.156/3018.97.210.157 to 18.97.210.15818.97.210.1592
4118.97.210.160/3018.97.210.161 to 18.97.210.16218.97.210.1632
4218.97.210.164/3018.97.210.165 to 18.97.210.16618.97.210.1672
4318.97.210.168/3018.97.210.169 to 18.97.210.17018.97.210.1712
4418.97.210.172/3018.97.210.173 to 18.97.210.17418.97.210.1752
4518.97.210.176/3018.97.210.177 to 18.97.210.17818.97.210.1792
4618.97.210.180/3018.97.210.181 to 18.97.210.18218.97.210.1832
4718.97.210.184/3018.97.210.185 to 18.97.210.18618.97.210.1872
4818.97.210.188/3018.97.210.189 to 18.97.210.19018.97.210.1912
4918.97.210.192/3018.97.210.193 to 18.97.210.19418.97.210.1952
5018.97.210.196/3018.97.210.197 to 18.97.210.19818.97.210.1992
5118.97.210.200/3018.97.210.201 to 18.97.210.20218.97.210.2032
5218.97.210.204/3018.97.210.205 to 18.97.210.20618.97.210.2072
5318.97.210.208/3018.97.210.209 to 18.97.210.21018.97.210.2112
5418.97.210.212/3018.97.210.213 to 18.97.210.21418.97.210.2152
5518.97.210.216/3018.97.210.217 to 18.97.210.21818.97.210.2192
5618.97.210.220/3018.97.210.221 to 18.97.210.22218.97.210.2232
5718.97.210.224/3018.97.210.225 to 18.97.210.22618.97.210.2272
5818.97.210.228/3018.97.210.229 to 18.97.210.23018.97.210.2312
5918.97.210.232/3018.97.210.233 to 18.97.210.23418.97.210.2352
6018.97.210.236/3018.97.210.237 to 18.97.210.23818.97.210.2392
6118.97.210.240/3018.97.210.241 to 18.97.210.24218.97.210.2432
6218.97.210.244/3018.97.210.245 to 18.97.210.24618.97.210.2472
6318.97.210.248/3018.97.210.249 to 18.97.210.25018.97.210.2512
6418.97.210.252/3018.97.210.253 to 18.97.210.25418.97.210.2552
6518.97.211.0/3018.97.211.1 to 18.97.211.218.97.211.32
6618.97.211.4/3018.97.211.5 to 18.97.211.618.97.211.72
6718.97.211.8/3018.97.211.9 to 18.97.211.1018.97.211.112
6818.97.211.12/3018.97.211.13 to 18.97.211.1418.97.211.152
6918.97.211.16/3018.97.211.17 to 18.97.211.1818.97.211.192
7018.97.211.20/3018.97.211.21 to 18.97.211.2218.97.211.232
7118.97.211.24/3018.97.211.25 to 18.97.211.2618.97.211.272
7218.97.211.28/3018.97.211.29 to 18.97.211.3018.97.211.312
7318.97.211.32/3018.97.211.33 to 18.97.211.3418.97.211.352
7418.97.211.36/3018.97.211.37 to 18.97.211.3818.97.211.392
7518.97.211.40/3018.97.211.41 to 18.97.211.4218.97.211.432
7618.97.211.44/3018.97.211.45 to 18.97.211.4618.97.211.472
7718.97.211.48/3018.97.211.49 to 18.97.211.5018.97.211.512
7818.97.211.52/3018.97.211.53 to 18.97.211.5418.97.211.552
7918.97.211.56/3018.97.211.57 to 18.97.211.5818.97.211.592
8018.97.211.60/3018.97.211.61 to 18.97.211.6218.97.211.632
8118.97.211.64/3018.97.211.65 to 18.97.211.6618.97.211.672
8218.97.211.68/3018.97.211.69 to 18.97.211.7018.97.211.712
8318.97.211.72/3018.97.211.73 to 18.97.211.7418.97.211.752
8418.97.211.76/3018.97.211.77 to 18.97.211.7818.97.211.792
8518.97.211.80/3018.97.211.81 to 18.97.211.8218.97.211.832
8618.97.211.84/3018.97.211.85 to 18.97.211.8618.97.211.872
8718.97.211.88/3018.97.211.89 to 18.97.211.9018.97.211.912
8818.97.211.92/3018.97.211.93 to 18.97.211.9418.97.211.952
8918.97.211.96/3018.97.211.97 to 18.97.211.9818.97.211.992
9018.97.211.100/3018.97.211.101 to 18.97.211.10218.97.211.1032
9118.97.211.104/3018.97.211.105 to 18.97.211.10618.97.211.1072
9218.97.211.108/3018.97.211.109 to 18.97.211.11018.97.211.1112
9318.97.211.112/3018.97.211.113 to 18.97.211.11418.97.211.1152
9418.97.211.116/3018.97.211.117 to 18.97.211.11818.97.211.1192
9518.97.211.120/3018.97.211.121 to 18.97.211.12218.97.211.1232
9618.97.211.124/3018.97.211.125 to 18.97.211.12618.97.211.1272
9718.97.211.128/3018.97.211.129 to 18.97.211.13018.97.211.1312
9818.97.211.132/3018.97.211.133 to 18.97.211.13418.97.211.1352
9918.97.211.136/3018.97.211.137 to 18.97.211.13818.97.211.1392
10018.97.211.140/3018.97.211.141 to 18.97.211.14218.97.211.1432
10118.97.211.144/3018.97.211.145 to 18.97.211.14618.97.211.1472
10218.97.211.148/3018.97.211.149 to 18.97.211.15018.97.211.1512
10318.97.211.152/3018.97.211.153 to 18.97.211.15418.97.211.1552
10418.97.211.156/3018.97.211.157 to 18.97.211.15818.97.211.1592
10518.97.211.160/3018.97.211.161 to 18.97.211.16218.97.211.1632
10618.97.211.164/3018.97.211.165 to 18.97.211.16618.97.211.1672
10718.97.211.168/3018.97.211.169 to 18.97.211.17018.97.211.1712
10818.97.211.172/3018.97.211.173 to 18.97.211.17418.97.211.1752
10918.97.211.176/3018.97.211.177 to 18.97.211.17818.97.211.1792
11018.97.211.180/3018.97.211.181 to 18.97.211.18218.97.211.1832
11118.97.211.184/3018.97.211.185 to 18.97.211.18618.97.211.1872
11218.97.211.188/3018.97.211.189 to 18.97.211.19018.97.211.1912
11318.97.211.192/3018.97.211.193 to 18.97.211.19418.97.211.1952
11418.97.211.196/3018.97.211.197 to 18.97.211.19818.97.211.1992
11518.97.211.200/3018.97.211.201 to 18.97.211.20218.97.211.2032
11618.97.211.204/3018.97.211.205 to 18.97.211.20618.97.211.2072
11718.97.211.208/3018.97.211.209 to 18.97.211.21018.97.211.2112
11818.97.211.212/3018.97.211.213 to 18.97.211.21418.97.211.2152
11918.97.211.216/3018.97.211.217 to 18.97.211.21818.97.211.2192
12018.97.211.220/3018.97.211.221 to 18.97.211.22218.97.211.2232
12118.97.211.224/3018.97.211.225 to 18.97.211.22618.97.211.2272
12218.97.211.228/3018.97.211.229 to 18.97.211.23018.97.211.2312
12318.97.211.232/3018.97.211.233 to 18.97.211.23418.97.211.2352
12418.97.211.236/3018.97.211.237 to 18.97.211.23818.97.211.2392
12518.97.211.240/3018.97.211.241 to 18.97.211.24218.97.211.2432
12618.97.211.244/3018.97.211.245 to 18.97.211.24618.97.211.2472
12718.97.211.248/3018.97.211.249 to 18.97.211.25018.97.211.2512
12818.97.211.252/3018.97.211.253 to 18.97.211.25418.97.211.2552

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.