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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.

Network162.78.128.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
162.78.128.0
Broadcast address
162.78.255.255
First usable
162.78.128.1
Last usable
162.78.255.254
Usable hosts
32,766 (32,768 less the network and broadcast addresses)
Subnet mask
255.255.128.0
Wildcard mask
0.0.127.255 (Cisco ACLs, OSPF)
Prefix length
/17
Type
Public public
Old class
B (default /16)
As numbers
Hex A24E8000 · Integer 2723053568 to 2723086335
Reverse DNS zones
128.78.162.in-addr.arpa
129.78.162.in-addr.arpa
130.78.162.in-addr.arpa
131.78.162.in-addr.arpa
132.78.162.in-addr.arpa
133.78.162.in-addr.arpa
134.78.162.in-addr.arpa
135.78.162.in-addr.arpa
136.78.162.in-addr.arpa
137.78.162.in-addr.arpa
138.78.162.in-addr.arpa
139.78.162.in-addr.arpa
140.78.162.in-addr.arpa
141.78.162.in-addr.arpa
142.78.162.in-addr.arpa
143.78.162.in-addr.arpa
and 112 more
/17 is not on a 8-bit boundary, so it takes 128 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100010.01001110.10000000.00000000162.78.128.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network10100010.01001110.10000000.00000000162.78.128.0
Broadcast10100010.01001110.11111111.11111111162.78.255.255
Split into smaller subnets/24
/18 (2)/19 (4)/20 (8)/21 (16)/22 (32)/23 (64)/24 (128)/25 (256)/26 (512)/27 (1,024)/28 (2,048)/29 (4,096)

162.78.128.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1162.78.128.0/24162.78.128.1 to 162.78.128.254162.78.128.255254
2162.78.129.0/24162.78.129.1 to 162.78.129.254162.78.129.255254
3162.78.130.0/24162.78.130.1 to 162.78.130.254162.78.130.255254
4162.78.131.0/24162.78.131.1 to 162.78.131.254162.78.131.255254
5162.78.132.0/24162.78.132.1 to 162.78.132.254162.78.132.255254
6162.78.133.0/24162.78.133.1 to 162.78.133.254162.78.133.255254
7162.78.134.0/24162.78.134.1 to 162.78.134.254162.78.134.255254
8162.78.135.0/24162.78.135.1 to 162.78.135.254162.78.135.255254
9162.78.136.0/24162.78.136.1 to 162.78.136.254162.78.136.255254
10162.78.137.0/24162.78.137.1 to 162.78.137.254162.78.137.255254
11162.78.138.0/24162.78.138.1 to 162.78.138.254162.78.138.255254
12162.78.139.0/24162.78.139.1 to 162.78.139.254162.78.139.255254
13162.78.140.0/24162.78.140.1 to 162.78.140.254162.78.140.255254
14162.78.141.0/24162.78.141.1 to 162.78.141.254162.78.141.255254
15162.78.142.0/24162.78.142.1 to 162.78.142.254162.78.142.255254
16162.78.143.0/24162.78.143.1 to 162.78.143.254162.78.143.255254
17162.78.144.0/24162.78.144.1 to 162.78.144.254162.78.144.255254
18162.78.145.0/24162.78.145.1 to 162.78.145.254162.78.145.255254
19162.78.146.0/24162.78.146.1 to 162.78.146.254162.78.146.255254
20162.78.147.0/24162.78.147.1 to 162.78.147.254162.78.147.255254
21162.78.148.0/24162.78.148.1 to 162.78.148.254162.78.148.255254
22162.78.149.0/24162.78.149.1 to 162.78.149.254162.78.149.255254
23162.78.150.0/24162.78.150.1 to 162.78.150.254162.78.150.255254
24162.78.151.0/24162.78.151.1 to 162.78.151.254162.78.151.255254
25162.78.152.0/24162.78.152.1 to 162.78.152.254162.78.152.255254
26162.78.153.0/24162.78.153.1 to 162.78.153.254162.78.153.255254
27162.78.154.0/24162.78.154.1 to 162.78.154.254162.78.154.255254
28162.78.155.0/24162.78.155.1 to 162.78.155.254162.78.155.255254
29162.78.156.0/24162.78.156.1 to 162.78.156.254162.78.156.255254
30162.78.157.0/24162.78.157.1 to 162.78.157.254162.78.157.255254
31162.78.158.0/24162.78.158.1 to 162.78.158.254162.78.158.255254
32162.78.159.0/24162.78.159.1 to 162.78.159.254162.78.159.255254
33162.78.160.0/24162.78.160.1 to 162.78.160.254162.78.160.255254
34162.78.161.0/24162.78.161.1 to 162.78.161.254162.78.161.255254
35162.78.162.0/24162.78.162.1 to 162.78.162.254162.78.162.255254
36162.78.163.0/24162.78.163.1 to 162.78.163.254162.78.163.255254
37162.78.164.0/24162.78.164.1 to 162.78.164.254162.78.164.255254
38162.78.165.0/24162.78.165.1 to 162.78.165.254162.78.165.255254
39162.78.166.0/24162.78.166.1 to 162.78.166.254162.78.166.255254
40162.78.167.0/24162.78.167.1 to 162.78.167.254162.78.167.255254
41162.78.168.0/24162.78.168.1 to 162.78.168.254162.78.168.255254
42162.78.169.0/24162.78.169.1 to 162.78.169.254162.78.169.255254
43162.78.170.0/24162.78.170.1 to 162.78.170.254162.78.170.255254
44162.78.171.0/24162.78.171.1 to 162.78.171.254162.78.171.255254
45162.78.172.0/24162.78.172.1 to 162.78.172.254162.78.172.255254
46162.78.173.0/24162.78.173.1 to 162.78.173.254162.78.173.255254
47162.78.174.0/24162.78.174.1 to 162.78.174.254162.78.174.255254
48162.78.175.0/24162.78.175.1 to 162.78.175.254162.78.175.255254
49162.78.176.0/24162.78.176.1 to 162.78.176.254162.78.176.255254
50162.78.177.0/24162.78.177.1 to 162.78.177.254162.78.177.255254
51162.78.178.0/24162.78.178.1 to 162.78.178.254162.78.178.255254
52162.78.179.0/24162.78.179.1 to 162.78.179.254162.78.179.255254
53162.78.180.0/24162.78.180.1 to 162.78.180.254162.78.180.255254
54162.78.181.0/24162.78.181.1 to 162.78.181.254162.78.181.255254
55162.78.182.0/24162.78.182.1 to 162.78.182.254162.78.182.255254
56162.78.183.0/24162.78.183.1 to 162.78.183.254162.78.183.255254
57162.78.184.0/24162.78.184.1 to 162.78.184.254162.78.184.255254
58162.78.185.0/24162.78.185.1 to 162.78.185.254162.78.185.255254
59162.78.186.0/24162.78.186.1 to 162.78.186.254162.78.186.255254
60162.78.187.0/24162.78.187.1 to 162.78.187.254162.78.187.255254
61162.78.188.0/24162.78.188.1 to 162.78.188.254162.78.188.255254
62162.78.189.0/24162.78.189.1 to 162.78.189.254162.78.189.255254
63162.78.190.0/24162.78.190.1 to 162.78.190.254162.78.190.255254
64162.78.191.0/24162.78.191.1 to 162.78.191.254162.78.191.255254
65162.78.192.0/24162.78.192.1 to 162.78.192.254162.78.192.255254
66162.78.193.0/24162.78.193.1 to 162.78.193.254162.78.193.255254
67162.78.194.0/24162.78.194.1 to 162.78.194.254162.78.194.255254
68162.78.195.0/24162.78.195.1 to 162.78.195.254162.78.195.255254
69162.78.196.0/24162.78.196.1 to 162.78.196.254162.78.196.255254
70162.78.197.0/24162.78.197.1 to 162.78.197.254162.78.197.255254
71162.78.198.0/24162.78.198.1 to 162.78.198.254162.78.198.255254
72162.78.199.0/24162.78.199.1 to 162.78.199.254162.78.199.255254
73162.78.200.0/24162.78.200.1 to 162.78.200.254162.78.200.255254
74162.78.201.0/24162.78.201.1 to 162.78.201.254162.78.201.255254
75162.78.202.0/24162.78.202.1 to 162.78.202.254162.78.202.255254
76162.78.203.0/24162.78.203.1 to 162.78.203.254162.78.203.255254
77162.78.204.0/24162.78.204.1 to 162.78.204.254162.78.204.255254
78162.78.205.0/24162.78.205.1 to 162.78.205.254162.78.205.255254
79162.78.206.0/24162.78.206.1 to 162.78.206.254162.78.206.255254
80162.78.207.0/24162.78.207.1 to 162.78.207.254162.78.207.255254
81162.78.208.0/24162.78.208.1 to 162.78.208.254162.78.208.255254
82162.78.209.0/24162.78.209.1 to 162.78.209.254162.78.209.255254
83162.78.210.0/24162.78.210.1 to 162.78.210.254162.78.210.255254
84162.78.211.0/24162.78.211.1 to 162.78.211.254162.78.211.255254
85162.78.212.0/24162.78.212.1 to 162.78.212.254162.78.212.255254
86162.78.213.0/24162.78.213.1 to 162.78.213.254162.78.213.255254
87162.78.214.0/24162.78.214.1 to 162.78.214.254162.78.214.255254
88162.78.215.0/24162.78.215.1 to 162.78.215.254162.78.215.255254
89162.78.216.0/24162.78.216.1 to 162.78.216.254162.78.216.255254
90162.78.217.0/24162.78.217.1 to 162.78.217.254162.78.217.255254
91162.78.218.0/24162.78.218.1 to 162.78.218.254162.78.218.255254
92162.78.219.0/24162.78.219.1 to 162.78.219.254162.78.219.255254
93162.78.220.0/24162.78.220.1 to 162.78.220.254162.78.220.255254
94162.78.221.0/24162.78.221.1 to 162.78.221.254162.78.221.255254
95162.78.222.0/24162.78.222.1 to 162.78.222.254162.78.222.255254
96162.78.223.0/24162.78.223.1 to 162.78.223.254162.78.223.255254
97162.78.224.0/24162.78.224.1 to 162.78.224.254162.78.224.255254
98162.78.225.0/24162.78.225.1 to 162.78.225.254162.78.225.255254
99162.78.226.0/24162.78.226.1 to 162.78.226.254162.78.226.255254
100162.78.227.0/24162.78.227.1 to 162.78.227.254162.78.227.255254
101162.78.228.0/24162.78.228.1 to 162.78.228.254162.78.228.255254
102162.78.229.0/24162.78.229.1 to 162.78.229.254162.78.229.255254
103162.78.230.0/24162.78.230.1 to 162.78.230.254162.78.230.255254
104162.78.231.0/24162.78.231.1 to 162.78.231.254162.78.231.255254
105162.78.232.0/24162.78.232.1 to 162.78.232.254162.78.232.255254
106162.78.233.0/24162.78.233.1 to 162.78.233.254162.78.233.255254
107162.78.234.0/24162.78.234.1 to 162.78.234.254162.78.234.255254
108162.78.235.0/24162.78.235.1 to 162.78.235.254162.78.235.255254
109162.78.236.0/24162.78.236.1 to 162.78.236.254162.78.236.255254
110162.78.237.0/24162.78.237.1 to 162.78.237.254162.78.237.255254
111162.78.238.0/24162.78.238.1 to 162.78.238.254162.78.238.255254
112162.78.239.0/24162.78.239.1 to 162.78.239.254162.78.239.255254
113162.78.240.0/24162.78.240.1 to 162.78.240.254162.78.240.255254
114162.78.241.0/24162.78.241.1 to 162.78.241.254162.78.241.255254
115162.78.242.0/24162.78.242.1 to 162.78.242.254162.78.242.255254
116162.78.243.0/24162.78.243.1 to 162.78.243.254162.78.243.255254
117162.78.244.0/24162.78.244.1 to 162.78.244.254162.78.244.255254
118162.78.245.0/24162.78.245.1 to 162.78.245.254162.78.245.255254
119162.78.246.0/24162.78.246.1 to 162.78.246.254162.78.246.255254
120162.78.247.0/24162.78.247.1 to 162.78.247.254162.78.247.255254
121162.78.248.0/24162.78.248.1 to 162.78.248.254162.78.248.255254
122162.78.249.0/24162.78.249.1 to 162.78.249.254162.78.249.255254
123162.78.250.0/24162.78.250.1 to 162.78.250.254162.78.250.255254
124162.78.251.0/24162.78.251.1 to 162.78.251.254162.78.251.255254
125162.78.252.0/24162.78.252.1 to 162.78.252.254162.78.252.255254
126162.78.253.0/24162.78.253.1 to 162.78.253.254162.78.253.255254
127162.78.254.0/24162.78.254.1 to 162.78.254.254162.78.254.255254
128162.78.255.0/24162.78.255.1 to 162.78.255.254162.78.255.255254

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.