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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.

Network217.99.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
217.99.0.0
Broadcast address
217.99.255.255
First usable
217.99.0.1
Last usable
217.99.255.254
Usable hosts
65,534 (65,536 less the network and broadcast addresses)
Subnet mask
255.255.0.0
Wildcard mask
0.0.255.255 (Cisco ACLs, OSPF)
Prefix length
/16
Type
Public public
Old class
C (default /24)
As numbers
Hex D9630000 · Integer 3647143936 to 3647209471
Reverse DNS zone
99.217.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11011001.01100011..00000000.00000000217.99.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network11011001.01100011..00000000.00000000217.99.0.0
Broadcast11011001.01100011..11111111.11111111217.99.255.255
Split into smaller subnets/23
/17 (2)/18 (4)/19 (8)/20 (16)/21 (32)/22 (64)/23 (128)/24 (256)/25 (512)/26 (1,024)/27 (2,048)/28 (4,096)

217.99.0.0/16 makes 128 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1217.99.0.0/23217.99.0.1 to 217.99.1.254217.99.1.255510
2217.99.2.0/23217.99.2.1 to 217.99.3.254217.99.3.255510
3217.99.4.0/23217.99.4.1 to 217.99.5.254217.99.5.255510
4217.99.6.0/23217.99.6.1 to 217.99.7.254217.99.7.255510
5217.99.8.0/23217.99.8.1 to 217.99.9.254217.99.9.255510
6217.99.10.0/23217.99.10.1 to 217.99.11.254217.99.11.255510
7217.99.12.0/23217.99.12.1 to 217.99.13.254217.99.13.255510
8217.99.14.0/23217.99.14.1 to 217.99.15.254217.99.15.255510
9217.99.16.0/23217.99.16.1 to 217.99.17.254217.99.17.255510
10217.99.18.0/23217.99.18.1 to 217.99.19.254217.99.19.255510
11217.99.20.0/23217.99.20.1 to 217.99.21.254217.99.21.255510
12217.99.22.0/23217.99.22.1 to 217.99.23.254217.99.23.255510
13217.99.24.0/23217.99.24.1 to 217.99.25.254217.99.25.255510
14217.99.26.0/23217.99.26.1 to 217.99.27.254217.99.27.255510
15217.99.28.0/23217.99.28.1 to 217.99.29.254217.99.29.255510
16217.99.30.0/23217.99.30.1 to 217.99.31.254217.99.31.255510
17217.99.32.0/23217.99.32.1 to 217.99.33.254217.99.33.255510
18217.99.34.0/23217.99.34.1 to 217.99.35.254217.99.35.255510
19217.99.36.0/23217.99.36.1 to 217.99.37.254217.99.37.255510
20217.99.38.0/23217.99.38.1 to 217.99.39.254217.99.39.255510
21217.99.40.0/23217.99.40.1 to 217.99.41.254217.99.41.255510
22217.99.42.0/23217.99.42.1 to 217.99.43.254217.99.43.255510
23217.99.44.0/23217.99.44.1 to 217.99.45.254217.99.45.255510
24217.99.46.0/23217.99.46.1 to 217.99.47.254217.99.47.255510
25217.99.48.0/23217.99.48.1 to 217.99.49.254217.99.49.255510
26217.99.50.0/23217.99.50.1 to 217.99.51.254217.99.51.255510
27217.99.52.0/23217.99.52.1 to 217.99.53.254217.99.53.255510
28217.99.54.0/23217.99.54.1 to 217.99.55.254217.99.55.255510
29217.99.56.0/23217.99.56.1 to 217.99.57.254217.99.57.255510
30217.99.58.0/23217.99.58.1 to 217.99.59.254217.99.59.255510
31217.99.60.0/23217.99.60.1 to 217.99.61.254217.99.61.255510
32217.99.62.0/23217.99.62.1 to 217.99.63.254217.99.63.255510
33217.99.64.0/23217.99.64.1 to 217.99.65.254217.99.65.255510
34217.99.66.0/23217.99.66.1 to 217.99.67.254217.99.67.255510
35217.99.68.0/23217.99.68.1 to 217.99.69.254217.99.69.255510
36217.99.70.0/23217.99.70.1 to 217.99.71.254217.99.71.255510
37217.99.72.0/23217.99.72.1 to 217.99.73.254217.99.73.255510
38217.99.74.0/23217.99.74.1 to 217.99.75.254217.99.75.255510
39217.99.76.0/23217.99.76.1 to 217.99.77.254217.99.77.255510
40217.99.78.0/23217.99.78.1 to 217.99.79.254217.99.79.255510
41217.99.80.0/23217.99.80.1 to 217.99.81.254217.99.81.255510
42217.99.82.0/23217.99.82.1 to 217.99.83.254217.99.83.255510
43217.99.84.0/23217.99.84.1 to 217.99.85.254217.99.85.255510
44217.99.86.0/23217.99.86.1 to 217.99.87.254217.99.87.255510
45217.99.88.0/23217.99.88.1 to 217.99.89.254217.99.89.255510
46217.99.90.0/23217.99.90.1 to 217.99.91.254217.99.91.255510
47217.99.92.0/23217.99.92.1 to 217.99.93.254217.99.93.255510
48217.99.94.0/23217.99.94.1 to 217.99.95.254217.99.95.255510
49217.99.96.0/23217.99.96.1 to 217.99.97.254217.99.97.255510
50217.99.98.0/23217.99.98.1 to 217.99.99.254217.99.99.255510
51217.99.100.0/23217.99.100.1 to 217.99.101.254217.99.101.255510
52217.99.102.0/23217.99.102.1 to 217.99.103.254217.99.103.255510
53217.99.104.0/23217.99.104.1 to 217.99.105.254217.99.105.255510
54217.99.106.0/23217.99.106.1 to 217.99.107.254217.99.107.255510
55217.99.108.0/23217.99.108.1 to 217.99.109.254217.99.109.255510
56217.99.110.0/23217.99.110.1 to 217.99.111.254217.99.111.255510
57217.99.112.0/23217.99.112.1 to 217.99.113.254217.99.113.255510
58217.99.114.0/23217.99.114.1 to 217.99.115.254217.99.115.255510
59217.99.116.0/23217.99.116.1 to 217.99.117.254217.99.117.255510
60217.99.118.0/23217.99.118.1 to 217.99.119.254217.99.119.255510
61217.99.120.0/23217.99.120.1 to 217.99.121.254217.99.121.255510
62217.99.122.0/23217.99.122.1 to 217.99.123.254217.99.123.255510
63217.99.124.0/23217.99.124.1 to 217.99.125.254217.99.125.255510
64217.99.126.0/23217.99.126.1 to 217.99.127.254217.99.127.255510
65217.99.128.0/23217.99.128.1 to 217.99.129.254217.99.129.255510
66217.99.130.0/23217.99.130.1 to 217.99.131.254217.99.131.255510
67217.99.132.0/23217.99.132.1 to 217.99.133.254217.99.133.255510
68217.99.134.0/23217.99.134.1 to 217.99.135.254217.99.135.255510
69217.99.136.0/23217.99.136.1 to 217.99.137.254217.99.137.255510
70217.99.138.0/23217.99.138.1 to 217.99.139.254217.99.139.255510
71217.99.140.0/23217.99.140.1 to 217.99.141.254217.99.141.255510
72217.99.142.0/23217.99.142.1 to 217.99.143.254217.99.143.255510
73217.99.144.0/23217.99.144.1 to 217.99.145.254217.99.145.255510
74217.99.146.0/23217.99.146.1 to 217.99.147.254217.99.147.255510
75217.99.148.0/23217.99.148.1 to 217.99.149.254217.99.149.255510
76217.99.150.0/23217.99.150.1 to 217.99.151.254217.99.151.255510
77217.99.152.0/23217.99.152.1 to 217.99.153.254217.99.153.255510
78217.99.154.0/23217.99.154.1 to 217.99.155.254217.99.155.255510
79217.99.156.0/23217.99.156.1 to 217.99.157.254217.99.157.255510
80217.99.158.0/23217.99.158.1 to 217.99.159.254217.99.159.255510
81217.99.160.0/23217.99.160.1 to 217.99.161.254217.99.161.255510
82217.99.162.0/23217.99.162.1 to 217.99.163.254217.99.163.255510
83217.99.164.0/23217.99.164.1 to 217.99.165.254217.99.165.255510
84217.99.166.0/23217.99.166.1 to 217.99.167.254217.99.167.255510
85217.99.168.0/23217.99.168.1 to 217.99.169.254217.99.169.255510
86217.99.170.0/23217.99.170.1 to 217.99.171.254217.99.171.255510
87217.99.172.0/23217.99.172.1 to 217.99.173.254217.99.173.255510
88217.99.174.0/23217.99.174.1 to 217.99.175.254217.99.175.255510
89217.99.176.0/23217.99.176.1 to 217.99.177.254217.99.177.255510
90217.99.178.0/23217.99.178.1 to 217.99.179.254217.99.179.255510
91217.99.180.0/23217.99.180.1 to 217.99.181.254217.99.181.255510
92217.99.182.0/23217.99.182.1 to 217.99.183.254217.99.183.255510
93217.99.184.0/23217.99.184.1 to 217.99.185.254217.99.185.255510
94217.99.186.0/23217.99.186.1 to 217.99.187.254217.99.187.255510
95217.99.188.0/23217.99.188.1 to 217.99.189.254217.99.189.255510
96217.99.190.0/23217.99.190.1 to 217.99.191.254217.99.191.255510
97217.99.192.0/23217.99.192.1 to 217.99.193.254217.99.193.255510
98217.99.194.0/23217.99.194.1 to 217.99.195.254217.99.195.255510
99217.99.196.0/23217.99.196.1 to 217.99.197.254217.99.197.255510
100217.99.198.0/23217.99.198.1 to 217.99.199.254217.99.199.255510
101217.99.200.0/23217.99.200.1 to 217.99.201.254217.99.201.255510
102217.99.202.0/23217.99.202.1 to 217.99.203.254217.99.203.255510
103217.99.204.0/23217.99.204.1 to 217.99.205.254217.99.205.255510
104217.99.206.0/23217.99.206.1 to 217.99.207.254217.99.207.255510
105217.99.208.0/23217.99.208.1 to 217.99.209.254217.99.209.255510
106217.99.210.0/23217.99.210.1 to 217.99.211.254217.99.211.255510
107217.99.212.0/23217.99.212.1 to 217.99.213.254217.99.213.255510
108217.99.214.0/23217.99.214.1 to 217.99.215.254217.99.215.255510
109217.99.216.0/23217.99.216.1 to 217.99.217.254217.99.217.255510
110217.99.218.0/23217.99.218.1 to 217.99.219.254217.99.219.255510
111217.99.220.0/23217.99.220.1 to 217.99.221.254217.99.221.255510
112217.99.222.0/23217.99.222.1 to 217.99.223.254217.99.223.255510
113217.99.224.0/23217.99.224.1 to 217.99.225.254217.99.225.255510
114217.99.226.0/23217.99.226.1 to 217.99.227.254217.99.227.255510
115217.99.228.0/23217.99.228.1 to 217.99.229.254217.99.229.255510
116217.99.230.0/23217.99.230.1 to 217.99.231.254217.99.231.255510
117217.99.232.0/23217.99.232.1 to 217.99.233.254217.99.233.255510
118217.99.234.0/23217.99.234.1 to 217.99.235.254217.99.235.255510
119217.99.236.0/23217.99.236.1 to 217.99.237.254217.99.237.255510
120217.99.238.0/23217.99.238.1 to 217.99.239.254217.99.239.255510
121217.99.240.0/23217.99.240.1 to 217.99.241.254217.99.241.255510
122217.99.242.0/23217.99.242.1 to 217.99.243.254217.99.243.255510
123217.99.244.0/23217.99.244.1 to 217.99.245.254217.99.245.255510
124217.99.246.0/23217.99.246.1 to 217.99.247.254217.99.247.255510
125217.99.248.0/23217.99.248.1 to 217.99.249.254217.99.249.255510
126217.99.250.0/23217.99.250.1 to 217.99.251.254217.99.251.255510
127217.99.252.0/23217.99.252.1 to 217.99.253.254217.99.253.255510
128217.99.254.0/23217.99.254.1 to 217.99.255.254217.99.255.255510

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.