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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.

Network253.3.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
253.3.0.0
Broadcast address
253.3.127.255
First usable
253.3.0.1
Last usable
253.3.127.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex FD030000 · Integer 4244832256 to 4244865023
Reverse DNS zones
0.3.253.in-addr.arpa
1.3.253.in-addr.arpa
2.3.253.in-addr.arpa
3.3.253.in-addr.arpa
4.3.253.in-addr.arpa
5.3.253.in-addr.arpa
6.3.253.in-addr.arpa
7.3.253.in-addr.arpa
8.3.253.in-addr.arpa
9.3.253.in-addr.arpa
10.3.253.in-addr.arpa
11.3.253.in-addr.arpa
12.3.253.in-addr.arpa
13.3.253.in-addr.arpa
14.3.253.in-addr.arpa
15.3.253.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
Address11111101.00000011.00000000.00000000253.3.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network11111101.00000011.00000000.00000000253.3.0.0
Broadcast11111101.00000011.01111111.11111111253.3.127.255
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)

253.3.0.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1253.3.0.0/24253.3.0.1 to 253.3.0.254253.3.0.255254
2253.3.1.0/24253.3.1.1 to 253.3.1.254253.3.1.255254
3253.3.2.0/24253.3.2.1 to 253.3.2.254253.3.2.255254
4253.3.3.0/24253.3.3.1 to 253.3.3.254253.3.3.255254
5253.3.4.0/24253.3.4.1 to 253.3.4.254253.3.4.255254
6253.3.5.0/24253.3.5.1 to 253.3.5.254253.3.5.255254
7253.3.6.0/24253.3.6.1 to 253.3.6.254253.3.6.255254
8253.3.7.0/24253.3.7.1 to 253.3.7.254253.3.7.255254
9253.3.8.0/24253.3.8.1 to 253.3.8.254253.3.8.255254
10253.3.9.0/24253.3.9.1 to 253.3.9.254253.3.9.255254
11253.3.10.0/24253.3.10.1 to 253.3.10.254253.3.10.255254
12253.3.11.0/24253.3.11.1 to 253.3.11.254253.3.11.255254
13253.3.12.0/24253.3.12.1 to 253.3.12.254253.3.12.255254
14253.3.13.0/24253.3.13.1 to 253.3.13.254253.3.13.255254
15253.3.14.0/24253.3.14.1 to 253.3.14.254253.3.14.255254
16253.3.15.0/24253.3.15.1 to 253.3.15.254253.3.15.255254
17253.3.16.0/24253.3.16.1 to 253.3.16.254253.3.16.255254
18253.3.17.0/24253.3.17.1 to 253.3.17.254253.3.17.255254
19253.3.18.0/24253.3.18.1 to 253.3.18.254253.3.18.255254
20253.3.19.0/24253.3.19.1 to 253.3.19.254253.3.19.255254
21253.3.20.0/24253.3.20.1 to 253.3.20.254253.3.20.255254
22253.3.21.0/24253.3.21.1 to 253.3.21.254253.3.21.255254
23253.3.22.0/24253.3.22.1 to 253.3.22.254253.3.22.255254
24253.3.23.0/24253.3.23.1 to 253.3.23.254253.3.23.255254
25253.3.24.0/24253.3.24.1 to 253.3.24.254253.3.24.255254
26253.3.25.0/24253.3.25.1 to 253.3.25.254253.3.25.255254
27253.3.26.0/24253.3.26.1 to 253.3.26.254253.3.26.255254
28253.3.27.0/24253.3.27.1 to 253.3.27.254253.3.27.255254
29253.3.28.0/24253.3.28.1 to 253.3.28.254253.3.28.255254
30253.3.29.0/24253.3.29.1 to 253.3.29.254253.3.29.255254
31253.3.30.0/24253.3.30.1 to 253.3.30.254253.3.30.255254
32253.3.31.0/24253.3.31.1 to 253.3.31.254253.3.31.255254
33253.3.32.0/24253.3.32.1 to 253.3.32.254253.3.32.255254
34253.3.33.0/24253.3.33.1 to 253.3.33.254253.3.33.255254
35253.3.34.0/24253.3.34.1 to 253.3.34.254253.3.34.255254
36253.3.35.0/24253.3.35.1 to 253.3.35.254253.3.35.255254
37253.3.36.0/24253.3.36.1 to 253.3.36.254253.3.36.255254
38253.3.37.0/24253.3.37.1 to 253.3.37.254253.3.37.255254
39253.3.38.0/24253.3.38.1 to 253.3.38.254253.3.38.255254
40253.3.39.0/24253.3.39.1 to 253.3.39.254253.3.39.255254
41253.3.40.0/24253.3.40.1 to 253.3.40.254253.3.40.255254
42253.3.41.0/24253.3.41.1 to 253.3.41.254253.3.41.255254
43253.3.42.0/24253.3.42.1 to 253.3.42.254253.3.42.255254
44253.3.43.0/24253.3.43.1 to 253.3.43.254253.3.43.255254
45253.3.44.0/24253.3.44.1 to 253.3.44.254253.3.44.255254
46253.3.45.0/24253.3.45.1 to 253.3.45.254253.3.45.255254
47253.3.46.0/24253.3.46.1 to 253.3.46.254253.3.46.255254
48253.3.47.0/24253.3.47.1 to 253.3.47.254253.3.47.255254
49253.3.48.0/24253.3.48.1 to 253.3.48.254253.3.48.255254
50253.3.49.0/24253.3.49.1 to 253.3.49.254253.3.49.255254
51253.3.50.0/24253.3.50.1 to 253.3.50.254253.3.50.255254
52253.3.51.0/24253.3.51.1 to 253.3.51.254253.3.51.255254
53253.3.52.0/24253.3.52.1 to 253.3.52.254253.3.52.255254
54253.3.53.0/24253.3.53.1 to 253.3.53.254253.3.53.255254
55253.3.54.0/24253.3.54.1 to 253.3.54.254253.3.54.255254
56253.3.55.0/24253.3.55.1 to 253.3.55.254253.3.55.255254
57253.3.56.0/24253.3.56.1 to 253.3.56.254253.3.56.255254
58253.3.57.0/24253.3.57.1 to 253.3.57.254253.3.57.255254
59253.3.58.0/24253.3.58.1 to 253.3.58.254253.3.58.255254
60253.3.59.0/24253.3.59.1 to 253.3.59.254253.3.59.255254
61253.3.60.0/24253.3.60.1 to 253.3.60.254253.3.60.255254
62253.3.61.0/24253.3.61.1 to 253.3.61.254253.3.61.255254
63253.3.62.0/24253.3.62.1 to 253.3.62.254253.3.62.255254
64253.3.63.0/24253.3.63.1 to 253.3.63.254253.3.63.255254
65253.3.64.0/24253.3.64.1 to 253.3.64.254253.3.64.255254
66253.3.65.0/24253.3.65.1 to 253.3.65.254253.3.65.255254
67253.3.66.0/24253.3.66.1 to 253.3.66.254253.3.66.255254
68253.3.67.0/24253.3.67.1 to 253.3.67.254253.3.67.255254
69253.3.68.0/24253.3.68.1 to 253.3.68.254253.3.68.255254
70253.3.69.0/24253.3.69.1 to 253.3.69.254253.3.69.255254
71253.3.70.0/24253.3.70.1 to 253.3.70.254253.3.70.255254
72253.3.71.0/24253.3.71.1 to 253.3.71.254253.3.71.255254
73253.3.72.0/24253.3.72.1 to 253.3.72.254253.3.72.255254
74253.3.73.0/24253.3.73.1 to 253.3.73.254253.3.73.255254
75253.3.74.0/24253.3.74.1 to 253.3.74.254253.3.74.255254
76253.3.75.0/24253.3.75.1 to 253.3.75.254253.3.75.255254
77253.3.76.0/24253.3.76.1 to 253.3.76.254253.3.76.255254
78253.3.77.0/24253.3.77.1 to 253.3.77.254253.3.77.255254
79253.3.78.0/24253.3.78.1 to 253.3.78.254253.3.78.255254
80253.3.79.0/24253.3.79.1 to 253.3.79.254253.3.79.255254
81253.3.80.0/24253.3.80.1 to 253.3.80.254253.3.80.255254
82253.3.81.0/24253.3.81.1 to 253.3.81.254253.3.81.255254
83253.3.82.0/24253.3.82.1 to 253.3.82.254253.3.82.255254
84253.3.83.0/24253.3.83.1 to 253.3.83.254253.3.83.255254
85253.3.84.0/24253.3.84.1 to 253.3.84.254253.3.84.255254
86253.3.85.0/24253.3.85.1 to 253.3.85.254253.3.85.255254
87253.3.86.0/24253.3.86.1 to 253.3.86.254253.3.86.255254
88253.3.87.0/24253.3.87.1 to 253.3.87.254253.3.87.255254
89253.3.88.0/24253.3.88.1 to 253.3.88.254253.3.88.255254
90253.3.89.0/24253.3.89.1 to 253.3.89.254253.3.89.255254
91253.3.90.0/24253.3.90.1 to 253.3.90.254253.3.90.255254
92253.3.91.0/24253.3.91.1 to 253.3.91.254253.3.91.255254
93253.3.92.0/24253.3.92.1 to 253.3.92.254253.3.92.255254
94253.3.93.0/24253.3.93.1 to 253.3.93.254253.3.93.255254
95253.3.94.0/24253.3.94.1 to 253.3.94.254253.3.94.255254
96253.3.95.0/24253.3.95.1 to 253.3.95.254253.3.95.255254
97253.3.96.0/24253.3.96.1 to 253.3.96.254253.3.96.255254
98253.3.97.0/24253.3.97.1 to 253.3.97.254253.3.97.255254
99253.3.98.0/24253.3.98.1 to 253.3.98.254253.3.98.255254
100253.3.99.0/24253.3.99.1 to 253.3.99.254253.3.99.255254
101253.3.100.0/24253.3.100.1 to 253.3.100.254253.3.100.255254
102253.3.101.0/24253.3.101.1 to 253.3.101.254253.3.101.255254
103253.3.102.0/24253.3.102.1 to 253.3.102.254253.3.102.255254
104253.3.103.0/24253.3.103.1 to 253.3.103.254253.3.103.255254
105253.3.104.0/24253.3.104.1 to 253.3.104.254253.3.104.255254
106253.3.105.0/24253.3.105.1 to 253.3.105.254253.3.105.255254
107253.3.106.0/24253.3.106.1 to 253.3.106.254253.3.106.255254
108253.3.107.0/24253.3.107.1 to 253.3.107.254253.3.107.255254
109253.3.108.0/24253.3.108.1 to 253.3.108.254253.3.108.255254
110253.3.109.0/24253.3.109.1 to 253.3.109.254253.3.109.255254
111253.3.110.0/24253.3.110.1 to 253.3.110.254253.3.110.255254
112253.3.111.0/24253.3.111.1 to 253.3.111.254253.3.111.255254
113253.3.112.0/24253.3.112.1 to 253.3.112.254253.3.112.255254
114253.3.113.0/24253.3.113.1 to 253.3.113.254253.3.113.255254
115253.3.114.0/24253.3.114.1 to 253.3.114.254253.3.114.255254
116253.3.115.0/24253.3.115.1 to 253.3.115.254253.3.115.255254
117253.3.116.0/24253.3.116.1 to 253.3.116.254253.3.116.255254
118253.3.117.0/24253.3.117.1 to 253.3.117.254253.3.117.255254
119253.3.118.0/24253.3.118.1 to 253.3.118.254253.3.118.255254
120253.3.119.0/24253.3.119.1 to 253.3.119.254253.3.119.255254
121253.3.120.0/24253.3.120.1 to 253.3.120.254253.3.120.255254
122253.3.121.0/24253.3.121.1 to 253.3.121.254253.3.121.255254
123253.3.122.0/24253.3.122.1 to 253.3.122.254253.3.122.255254
124253.3.123.0/24253.3.123.1 to 253.3.123.254253.3.123.255254
125253.3.124.0/24253.3.124.1 to 253.3.124.254253.3.124.255254
126253.3.125.0/24253.3.125.1 to 253.3.125.254253.3.125.255254
127253.3.126.0/24253.3.126.1 to 253.3.126.254253.3.126.255254
128253.3.127.0/24253.3.127.1 to 253.3.127.254253.3.127.255254

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.