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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.

Network108.0.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
108.0.0.0
Broadcast address
108.0.127.255
First usable
108.0.0.1
Last usable
108.0.127.254
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
A (default /8)
As numbers
Hex 6C000000 · Integer 1811939328 to 1811972095
Reverse DNS zones
0.0.108.in-addr.arpa
1.0.108.in-addr.arpa
2.0.108.in-addr.arpa
3.0.108.in-addr.arpa
4.0.108.in-addr.arpa
5.0.108.in-addr.arpa
6.0.108.in-addr.arpa
7.0.108.in-addr.arpa
8.0.108.in-addr.arpa
9.0.108.in-addr.arpa
10.0.108.in-addr.arpa
11.0.108.in-addr.arpa
12.0.108.in-addr.arpa
13.0.108.in-addr.arpa
14.0.108.in-addr.arpa
15.0.108.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
Address01101100.00000000.00000000.00000000108.0.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network01101100.00000000.00000000.00000000108.0.0.0
Broadcast01101100.00000000.01111111.11111111108.0.127.255
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)

108.0.0.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1108.0.0.0/24108.0.0.1 to 108.0.0.254108.0.0.255254
2108.0.1.0/24108.0.1.1 to 108.0.1.254108.0.1.255254
3108.0.2.0/24108.0.2.1 to 108.0.2.254108.0.2.255254
4108.0.3.0/24108.0.3.1 to 108.0.3.254108.0.3.255254
5108.0.4.0/24108.0.4.1 to 108.0.4.254108.0.4.255254
6108.0.5.0/24108.0.5.1 to 108.0.5.254108.0.5.255254
7108.0.6.0/24108.0.6.1 to 108.0.6.254108.0.6.255254
8108.0.7.0/24108.0.7.1 to 108.0.7.254108.0.7.255254
9108.0.8.0/24108.0.8.1 to 108.0.8.254108.0.8.255254
10108.0.9.0/24108.0.9.1 to 108.0.9.254108.0.9.255254
11108.0.10.0/24108.0.10.1 to 108.0.10.254108.0.10.255254
12108.0.11.0/24108.0.11.1 to 108.0.11.254108.0.11.255254
13108.0.12.0/24108.0.12.1 to 108.0.12.254108.0.12.255254
14108.0.13.0/24108.0.13.1 to 108.0.13.254108.0.13.255254
15108.0.14.0/24108.0.14.1 to 108.0.14.254108.0.14.255254
16108.0.15.0/24108.0.15.1 to 108.0.15.254108.0.15.255254
17108.0.16.0/24108.0.16.1 to 108.0.16.254108.0.16.255254
18108.0.17.0/24108.0.17.1 to 108.0.17.254108.0.17.255254
19108.0.18.0/24108.0.18.1 to 108.0.18.254108.0.18.255254
20108.0.19.0/24108.0.19.1 to 108.0.19.254108.0.19.255254
21108.0.20.0/24108.0.20.1 to 108.0.20.254108.0.20.255254
22108.0.21.0/24108.0.21.1 to 108.0.21.254108.0.21.255254
23108.0.22.0/24108.0.22.1 to 108.0.22.254108.0.22.255254
24108.0.23.0/24108.0.23.1 to 108.0.23.254108.0.23.255254
25108.0.24.0/24108.0.24.1 to 108.0.24.254108.0.24.255254
26108.0.25.0/24108.0.25.1 to 108.0.25.254108.0.25.255254
27108.0.26.0/24108.0.26.1 to 108.0.26.254108.0.26.255254
28108.0.27.0/24108.0.27.1 to 108.0.27.254108.0.27.255254
29108.0.28.0/24108.0.28.1 to 108.0.28.254108.0.28.255254
30108.0.29.0/24108.0.29.1 to 108.0.29.254108.0.29.255254
31108.0.30.0/24108.0.30.1 to 108.0.30.254108.0.30.255254
32108.0.31.0/24108.0.31.1 to 108.0.31.254108.0.31.255254
33108.0.32.0/24108.0.32.1 to 108.0.32.254108.0.32.255254
34108.0.33.0/24108.0.33.1 to 108.0.33.254108.0.33.255254
35108.0.34.0/24108.0.34.1 to 108.0.34.254108.0.34.255254
36108.0.35.0/24108.0.35.1 to 108.0.35.254108.0.35.255254
37108.0.36.0/24108.0.36.1 to 108.0.36.254108.0.36.255254
38108.0.37.0/24108.0.37.1 to 108.0.37.254108.0.37.255254
39108.0.38.0/24108.0.38.1 to 108.0.38.254108.0.38.255254
40108.0.39.0/24108.0.39.1 to 108.0.39.254108.0.39.255254
41108.0.40.0/24108.0.40.1 to 108.0.40.254108.0.40.255254
42108.0.41.0/24108.0.41.1 to 108.0.41.254108.0.41.255254
43108.0.42.0/24108.0.42.1 to 108.0.42.254108.0.42.255254
44108.0.43.0/24108.0.43.1 to 108.0.43.254108.0.43.255254
45108.0.44.0/24108.0.44.1 to 108.0.44.254108.0.44.255254
46108.0.45.0/24108.0.45.1 to 108.0.45.254108.0.45.255254
47108.0.46.0/24108.0.46.1 to 108.0.46.254108.0.46.255254
48108.0.47.0/24108.0.47.1 to 108.0.47.254108.0.47.255254
49108.0.48.0/24108.0.48.1 to 108.0.48.254108.0.48.255254
50108.0.49.0/24108.0.49.1 to 108.0.49.254108.0.49.255254
51108.0.50.0/24108.0.50.1 to 108.0.50.254108.0.50.255254
52108.0.51.0/24108.0.51.1 to 108.0.51.254108.0.51.255254
53108.0.52.0/24108.0.52.1 to 108.0.52.254108.0.52.255254
54108.0.53.0/24108.0.53.1 to 108.0.53.254108.0.53.255254
55108.0.54.0/24108.0.54.1 to 108.0.54.254108.0.54.255254
56108.0.55.0/24108.0.55.1 to 108.0.55.254108.0.55.255254
57108.0.56.0/24108.0.56.1 to 108.0.56.254108.0.56.255254
58108.0.57.0/24108.0.57.1 to 108.0.57.254108.0.57.255254
59108.0.58.0/24108.0.58.1 to 108.0.58.254108.0.58.255254
60108.0.59.0/24108.0.59.1 to 108.0.59.254108.0.59.255254
61108.0.60.0/24108.0.60.1 to 108.0.60.254108.0.60.255254
62108.0.61.0/24108.0.61.1 to 108.0.61.254108.0.61.255254
63108.0.62.0/24108.0.62.1 to 108.0.62.254108.0.62.255254
64108.0.63.0/24108.0.63.1 to 108.0.63.254108.0.63.255254
65108.0.64.0/24108.0.64.1 to 108.0.64.254108.0.64.255254
66108.0.65.0/24108.0.65.1 to 108.0.65.254108.0.65.255254
67108.0.66.0/24108.0.66.1 to 108.0.66.254108.0.66.255254
68108.0.67.0/24108.0.67.1 to 108.0.67.254108.0.67.255254
69108.0.68.0/24108.0.68.1 to 108.0.68.254108.0.68.255254
70108.0.69.0/24108.0.69.1 to 108.0.69.254108.0.69.255254
71108.0.70.0/24108.0.70.1 to 108.0.70.254108.0.70.255254
72108.0.71.0/24108.0.71.1 to 108.0.71.254108.0.71.255254
73108.0.72.0/24108.0.72.1 to 108.0.72.254108.0.72.255254
74108.0.73.0/24108.0.73.1 to 108.0.73.254108.0.73.255254
75108.0.74.0/24108.0.74.1 to 108.0.74.254108.0.74.255254
76108.0.75.0/24108.0.75.1 to 108.0.75.254108.0.75.255254
77108.0.76.0/24108.0.76.1 to 108.0.76.254108.0.76.255254
78108.0.77.0/24108.0.77.1 to 108.0.77.254108.0.77.255254
79108.0.78.0/24108.0.78.1 to 108.0.78.254108.0.78.255254
80108.0.79.0/24108.0.79.1 to 108.0.79.254108.0.79.255254
81108.0.80.0/24108.0.80.1 to 108.0.80.254108.0.80.255254
82108.0.81.0/24108.0.81.1 to 108.0.81.254108.0.81.255254
83108.0.82.0/24108.0.82.1 to 108.0.82.254108.0.82.255254
84108.0.83.0/24108.0.83.1 to 108.0.83.254108.0.83.255254
85108.0.84.0/24108.0.84.1 to 108.0.84.254108.0.84.255254
86108.0.85.0/24108.0.85.1 to 108.0.85.254108.0.85.255254
87108.0.86.0/24108.0.86.1 to 108.0.86.254108.0.86.255254
88108.0.87.0/24108.0.87.1 to 108.0.87.254108.0.87.255254
89108.0.88.0/24108.0.88.1 to 108.0.88.254108.0.88.255254
90108.0.89.0/24108.0.89.1 to 108.0.89.254108.0.89.255254
91108.0.90.0/24108.0.90.1 to 108.0.90.254108.0.90.255254
92108.0.91.0/24108.0.91.1 to 108.0.91.254108.0.91.255254
93108.0.92.0/24108.0.92.1 to 108.0.92.254108.0.92.255254
94108.0.93.0/24108.0.93.1 to 108.0.93.254108.0.93.255254
95108.0.94.0/24108.0.94.1 to 108.0.94.254108.0.94.255254
96108.0.95.0/24108.0.95.1 to 108.0.95.254108.0.95.255254
97108.0.96.0/24108.0.96.1 to 108.0.96.254108.0.96.255254
98108.0.97.0/24108.0.97.1 to 108.0.97.254108.0.97.255254
99108.0.98.0/24108.0.98.1 to 108.0.98.254108.0.98.255254
100108.0.99.0/24108.0.99.1 to 108.0.99.254108.0.99.255254
101108.0.100.0/24108.0.100.1 to 108.0.100.254108.0.100.255254
102108.0.101.0/24108.0.101.1 to 108.0.101.254108.0.101.255254
103108.0.102.0/24108.0.102.1 to 108.0.102.254108.0.102.255254
104108.0.103.0/24108.0.103.1 to 108.0.103.254108.0.103.255254
105108.0.104.0/24108.0.104.1 to 108.0.104.254108.0.104.255254
106108.0.105.0/24108.0.105.1 to 108.0.105.254108.0.105.255254
107108.0.106.0/24108.0.106.1 to 108.0.106.254108.0.106.255254
108108.0.107.0/24108.0.107.1 to 108.0.107.254108.0.107.255254
109108.0.108.0/24108.0.108.1 to 108.0.108.254108.0.108.255254
110108.0.109.0/24108.0.109.1 to 108.0.109.254108.0.109.255254
111108.0.110.0/24108.0.110.1 to 108.0.110.254108.0.110.255254
112108.0.111.0/24108.0.111.1 to 108.0.111.254108.0.111.255254
113108.0.112.0/24108.0.112.1 to 108.0.112.254108.0.112.255254
114108.0.113.0/24108.0.113.1 to 108.0.113.254108.0.113.255254
115108.0.114.0/24108.0.114.1 to 108.0.114.254108.0.114.255254
116108.0.115.0/24108.0.115.1 to 108.0.115.254108.0.115.255254
117108.0.116.0/24108.0.116.1 to 108.0.116.254108.0.116.255254
118108.0.117.0/24108.0.117.1 to 108.0.117.254108.0.117.255254
119108.0.118.0/24108.0.118.1 to 108.0.118.254108.0.118.255254
120108.0.119.0/24108.0.119.1 to 108.0.119.254108.0.119.255254
121108.0.120.0/24108.0.120.1 to 108.0.120.254108.0.120.255254
122108.0.121.0/24108.0.121.1 to 108.0.121.254108.0.121.255254
123108.0.122.0/24108.0.122.1 to 108.0.122.254108.0.122.255254
124108.0.123.0/24108.0.123.1 to 108.0.123.254108.0.123.255254
125108.0.124.0/24108.0.124.1 to 108.0.124.254108.0.124.255254
126108.0.125.0/24108.0.125.1 to 108.0.125.254108.0.125.255254
127108.0.126.0/24108.0.126.1 to 108.0.126.254108.0.126.255254
128108.0.127.0/24108.0.127.1 to 108.0.127.254108.0.127.255254

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.