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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.

Network177.78.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
177.78.0.0
Broadcast address
177.78.127.255
First usable
177.78.0.1
Last usable
177.78.127.254
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 B14E0000 · Integer 2974679040 to 2974711807
Reverse DNS zones
0.78.177.in-addr.arpa
1.78.177.in-addr.arpa
2.78.177.in-addr.arpa
3.78.177.in-addr.arpa
4.78.177.in-addr.arpa
5.78.177.in-addr.arpa
6.78.177.in-addr.arpa
7.78.177.in-addr.arpa
8.78.177.in-addr.arpa
9.78.177.in-addr.arpa
10.78.177.in-addr.arpa
11.78.177.in-addr.arpa
12.78.177.in-addr.arpa
13.78.177.in-addr.arpa
14.78.177.in-addr.arpa
15.78.177.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
Address10110001.01001110.00000000.00000000177.78.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network10110001.01001110.00000000.00000000177.78.0.0
Broadcast10110001.01001110.01111111.11111111177.78.127.255
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)

177.78.0.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1177.78.0.0/24177.78.0.1 to 177.78.0.254177.78.0.255254
2177.78.1.0/24177.78.1.1 to 177.78.1.254177.78.1.255254
3177.78.2.0/24177.78.2.1 to 177.78.2.254177.78.2.255254
4177.78.3.0/24177.78.3.1 to 177.78.3.254177.78.3.255254
5177.78.4.0/24177.78.4.1 to 177.78.4.254177.78.4.255254
6177.78.5.0/24177.78.5.1 to 177.78.5.254177.78.5.255254
7177.78.6.0/24177.78.6.1 to 177.78.6.254177.78.6.255254
8177.78.7.0/24177.78.7.1 to 177.78.7.254177.78.7.255254
9177.78.8.0/24177.78.8.1 to 177.78.8.254177.78.8.255254
10177.78.9.0/24177.78.9.1 to 177.78.9.254177.78.9.255254
11177.78.10.0/24177.78.10.1 to 177.78.10.254177.78.10.255254
12177.78.11.0/24177.78.11.1 to 177.78.11.254177.78.11.255254
13177.78.12.0/24177.78.12.1 to 177.78.12.254177.78.12.255254
14177.78.13.0/24177.78.13.1 to 177.78.13.254177.78.13.255254
15177.78.14.0/24177.78.14.1 to 177.78.14.254177.78.14.255254
16177.78.15.0/24177.78.15.1 to 177.78.15.254177.78.15.255254
17177.78.16.0/24177.78.16.1 to 177.78.16.254177.78.16.255254
18177.78.17.0/24177.78.17.1 to 177.78.17.254177.78.17.255254
19177.78.18.0/24177.78.18.1 to 177.78.18.254177.78.18.255254
20177.78.19.0/24177.78.19.1 to 177.78.19.254177.78.19.255254
21177.78.20.0/24177.78.20.1 to 177.78.20.254177.78.20.255254
22177.78.21.0/24177.78.21.1 to 177.78.21.254177.78.21.255254
23177.78.22.0/24177.78.22.1 to 177.78.22.254177.78.22.255254
24177.78.23.0/24177.78.23.1 to 177.78.23.254177.78.23.255254
25177.78.24.0/24177.78.24.1 to 177.78.24.254177.78.24.255254
26177.78.25.0/24177.78.25.1 to 177.78.25.254177.78.25.255254
27177.78.26.0/24177.78.26.1 to 177.78.26.254177.78.26.255254
28177.78.27.0/24177.78.27.1 to 177.78.27.254177.78.27.255254
29177.78.28.0/24177.78.28.1 to 177.78.28.254177.78.28.255254
30177.78.29.0/24177.78.29.1 to 177.78.29.254177.78.29.255254
31177.78.30.0/24177.78.30.1 to 177.78.30.254177.78.30.255254
32177.78.31.0/24177.78.31.1 to 177.78.31.254177.78.31.255254
33177.78.32.0/24177.78.32.1 to 177.78.32.254177.78.32.255254
34177.78.33.0/24177.78.33.1 to 177.78.33.254177.78.33.255254
35177.78.34.0/24177.78.34.1 to 177.78.34.254177.78.34.255254
36177.78.35.0/24177.78.35.1 to 177.78.35.254177.78.35.255254
37177.78.36.0/24177.78.36.1 to 177.78.36.254177.78.36.255254
38177.78.37.0/24177.78.37.1 to 177.78.37.254177.78.37.255254
39177.78.38.0/24177.78.38.1 to 177.78.38.254177.78.38.255254
40177.78.39.0/24177.78.39.1 to 177.78.39.254177.78.39.255254
41177.78.40.0/24177.78.40.1 to 177.78.40.254177.78.40.255254
42177.78.41.0/24177.78.41.1 to 177.78.41.254177.78.41.255254
43177.78.42.0/24177.78.42.1 to 177.78.42.254177.78.42.255254
44177.78.43.0/24177.78.43.1 to 177.78.43.254177.78.43.255254
45177.78.44.0/24177.78.44.1 to 177.78.44.254177.78.44.255254
46177.78.45.0/24177.78.45.1 to 177.78.45.254177.78.45.255254
47177.78.46.0/24177.78.46.1 to 177.78.46.254177.78.46.255254
48177.78.47.0/24177.78.47.1 to 177.78.47.254177.78.47.255254
49177.78.48.0/24177.78.48.1 to 177.78.48.254177.78.48.255254
50177.78.49.0/24177.78.49.1 to 177.78.49.254177.78.49.255254
51177.78.50.0/24177.78.50.1 to 177.78.50.254177.78.50.255254
52177.78.51.0/24177.78.51.1 to 177.78.51.254177.78.51.255254
53177.78.52.0/24177.78.52.1 to 177.78.52.254177.78.52.255254
54177.78.53.0/24177.78.53.1 to 177.78.53.254177.78.53.255254
55177.78.54.0/24177.78.54.1 to 177.78.54.254177.78.54.255254
56177.78.55.0/24177.78.55.1 to 177.78.55.254177.78.55.255254
57177.78.56.0/24177.78.56.1 to 177.78.56.254177.78.56.255254
58177.78.57.0/24177.78.57.1 to 177.78.57.254177.78.57.255254
59177.78.58.0/24177.78.58.1 to 177.78.58.254177.78.58.255254
60177.78.59.0/24177.78.59.1 to 177.78.59.254177.78.59.255254
61177.78.60.0/24177.78.60.1 to 177.78.60.254177.78.60.255254
62177.78.61.0/24177.78.61.1 to 177.78.61.254177.78.61.255254
63177.78.62.0/24177.78.62.1 to 177.78.62.254177.78.62.255254
64177.78.63.0/24177.78.63.1 to 177.78.63.254177.78.63.255254
65177.78.64.0/24177.78.64.1 to 177.78.64.254177.78.64.255254
66177.78.65.0/24177.78.65.1 to 177.78.65.254177.78.65.255254
67177.78.66.0/24177.78.66.1 to 177.78.66.254177.78.66.255254
68177.78.67.0/24177.78.67.1 to 177.78.67.254177.78.67.255254
69177.78.68.0/24177.78.68.1 to 177.78.68.254177.78.68.255254
70177.78.69.0/24177.78.69.1 to 177.78.69.254177.78.69.255254
71177.78.70.0/24177.78.70.1 to 177.78.70.254177.78.70.255254
72177.78.71.0/24177.78.71.1 to 177.78.71.254177.78.71.255254
73177.78.72.0/24177.78.72.1 to 177.78.72.254177.78.72.255254
74177.78.73.0/24177.78.73.1 to 177.78.73.254177.78.73.255254
75177.78.74.0/24177.78.74.1 to 177.78.74.254177.78.74.255254
76177.78.75.0/24177.78.75.1 to 177.78.75.254177.78.75.255254
77177.78.76.0/24177.78.76.1 to 177.78.76.254177.78.76.255254
78177.78.77.0/24177.78.77.1 to 177.78.77.254177.78.77.255254
79177.78.78.0/24177.78.78.1 to 177.78.78.254177.78.78.255254
80177.78.79.0/24177.78.79.1 to 177.78.79.254177.78.79.255254
81177.78.80.0/24177.78.80.1 to 177.78.80.254177.78.80.255254
82177.78.81.0/24177.78.81.1 to 177.78.81.254177.78.81.255254
83177.78.82.0/24177.78.82.1 to 177.78.82.254177.78.82.255254
84177.78.83.0/24177.78.83.1 to 177.78.83.254177.78.83.255254
85177.78.84.0/24177.78.84.1 to 177.78.84.254177.78.84.255254
86177.78.85.0/24177.78.85.1 to 177.78.85.254177.78.85.255254
87177.78.86.0/24177.78.86.1 to 177.78.86.254177.78.86.255254
88177.78.87.0/24177.78.87.1 to 177.78.87.254177.78.87.255254
89177.78.88.0/24177.78.88.1 to 177.78.88.254177.78.88.255254
90177.78.89.0/24177.78.89.1 to 177.78.89.254177.78.89.255254
91177.78.90.0/24177.78.90.1 to 177.78.90.254177.78.90.255254
92177.78.91.0/24177.78.91.1 to 177.78.91.254177.78.91.255254
93177.78.92.0/24177.78.92.1 to 177.78.92.254177.78.92.255254
94177.78.93.0/24177.78.93.1 to 177.78.93.254177.78.93.255254
95177.78.94.0/24177.78.94.1 to 177.78.94.254177.78.94.255254
96177.78.95.0/24177.78.95.1 to 177.78.95.254177.78.95.255254
97177.78.96.0/24177.78.96.1 to 177.78.96.254177.78.96.255254
98177.78.97.0/24177.78.97.1 to 177.78.97.254177.78.97.255254
99177.78.98.0/24177.78.98.1 to 177.78.98.254177.78.98.255254
100177.78.99.0/24177.78.99.1 to 177.78.99.254177.78.99.255254
101177.78.100.0/24177.78.100.1 to 177.78.100.254177.78.100.255254
102177.78.101.0/24177.78.101.1 to 177.78.101.254177.78.101.255254
103177.78.102.0/24177.78.102.1 to 177.78.102.254177.78.102.255254
104177.78.103.0/24177.78.103.1 to 177.78.103.254177.78.103.255254
105177.78.104.0/24177.78.104.1 to 177.78.104.254177.78.104.255254
106177.78.105.0/24177.78.105.1 to 177.78.105.254177.78.105.255254
107177.78.106.0/24177.78.106.1 to 177.78.106.254177.78.106.255254
108177.78.107.0/24177.78.107.1 to 177.78.107.254177.78.107.255254
109177.78.108.0/24177.78.108.1 to 177.78.108.254177.78.108.255254
110177.78.109.0/24177.78.109.1 to 177.78.109.254177.78.109.255254
111177.78.110.0/24177.78.110.1 to 177.78.110.254177.78.110.255254
112177.78.111.0/24177.78.111.1 to 177.78.111.254177.78.111.255254
113177.78.112.0/24177.78.112.1 to 177.78.112.254177.78.112.255254
114177.78.113.0/24177.78.113.1 to 177.78.113.254177.78.113.255254
115177.78.114.0/24177.78.114.1 to 177.78.114.254177.78.114.255254
116177.78.115.0/24177.78.115.1 to 177.78.115.254177.78.115.255254
117177.78.116.0/24177.78.116.1 to 177.78.116.254177.78.116.255254
118177.78.117.0/24177.78.117.1 to 177.78.117.254177.78.117.255254
119177.78.118.0/24177.78.118.1 to 177.78.118.254177.78.118.255254
120177.78.119.0/24177.78.119.1 to 177.78.119.254177.78.119.255254
121177.78.120.0/24177.78.120.1 to 177.78.120.254177.78.120.255254
122177.78.121.0/24177.78.121.1 to 177.78.121.254177.78.121.255254
123177.78.122.0/24177.78.122.1 to 177.78.122.254177.78.122.255254
124177.78.123.0/24177.78.123.1 to 177.78.123.254177.78.123.255254
125177.78.124.0/24177.78.124.1 to 177.78.124.254177.78.124.255254
126177.78.125.0/24177.78.125.1 to 177.78.125.254177.78.125.255254
127177.78.126.0/24177.78.126.1 to 177.78.126.254177.78.126.255254
128177.78.127.0/24177.78.127.1 to 177.78.127.254177.78.127.255254

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.