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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.

Network235.128.0.0/11
Usable hosts2,097,150
Subnet mask255.224.0.0
Addresses2,097,152
Network address
235.128.0.0
Broadcast address
235.159.255.255
First usable
235.128.0.1
Last usable
235.159.255.254
Usable hosts
2,097,150 (2,097,152 less the network and broadcast addresses)
Subnet mask
255.224.0.0
Wildcard mask
0.31.255.255 (Cisco ACLs, OSPF)
Prefix length
/11
Type
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex EB800000 · Integer 3951034368 to 3953131519
Reverse DNS zones
128.235.in-addr.arpa
129.235.in-addr.arpa
130.235.in-addr.arpa
131.235.in-addr.arpa
132.235.in-addr.arpa
133.235.in-addr.arpa
134.235.in-addr.arpa
135.235.in-addr.arpa
136.235.in-addr.arpa
137.235.in-addr.arpa
138.235.in-addr.arpa
139.235.in-addr.arpa
140.235.in-addr.arpa
141.235.in-addr.arpa
142.235.in-addr.arpa
143.235.in-addr.arpa
and 16 more
/11 is not on a 8-bit boundary, so it takes 32 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11101011.10000000.00000000.00000000235.128.0.0
Subnet mask11111111.11100000.00000000.00000000255.224.0.0
Network11101011.10000000.00000000.00000000235.128.0.0
Broadcast11101011.10011111.11111111.11111111235.159.255.255
Split into smaller subnets/17
/12 (2)/13 (4)/14 (8)/15 (16)/16 (32)/17 (64)/18 (128)/19 (256)/20 (512)/21 (1,024)/22 (2,048)/23 (4,096)

235.128.0.0/11 makes 64 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1235.128.0.0/17235.128.0.1 to 235.128.127.254235.128.127.25532,766
2235.128.128.0/17235.128.128.1 to 235.128.255.254235.128.255.25532,766
3235.129.0.0/17235.129.0.1 to 235.129.127.254235.129.127.25532,766
4235.129.128.0/17235.129.128.1 to 235.129.255.254235.129.255.25532,766
5235.130.0.0/17235.130.0.1 to 235.130.127.254235.130.127.25532,766
6235.130.128.0/17235.130.128.1 to 235.130.255.254235.130.255.25532,766
7235.131.0.0/17235.131.0.1 to 235.131.127.254235.131.127.25532,766
8235.131.128.0/17235.131.128.1 to 235.131.255.254235.131.255.25532,766
9235.132.0.0/17235.132.0.1 to 235.132.127.254235.132.127.25532,766
10235.132.128.0/17235.132.128.1 to 235.132.255.254235.132.255.25532,766
11235.133.0.0/17235.133.0.1 to 235.133.127.254235.133.127.25532,766
12235.133.128.0/17235.133.128.1 to 235.133.255.254235.133.255.25532,766
13235.134.0.0/17235.134.0.1 to 235.134.127.254235.134.127.25532,766
14235.134.128.0/17235.134.128.1 to 235.134.255.254235.134.255.25532,766
15235.135.0.0/17235.135.0.1 to 235.135.127.254235.135.127.25532,766
16235.135.128.0/17235.135.128.1 to 235.135.255.254235.135.255.25532,766
17235.136.0.0/17235.136.0.1 to 235.136.127.254235.136.127.25532,766
18235.136.128.0/17235.136.128.1 to 235.136.255.254235.136.255.25532,766
19235.137.0.0/17235.137.0.1 to 235.137.127.254235.137.127.25532,766
20235.137.128.0/17235.137.128.1 to 235.137.255.254235.137.255.25532,766
21235.138.0.0/17235.138.0.1 to 235.138.127.254235.138.127.25532,766
22235.138.128.0/17235.138.128.1 to 235.138.255.254235.138.255.25532,766
23235.139.0.0/17235.139.0.1 to 235.139.127.254235.139.127.25532,766
24235.139.128.0/17235.139.128.1 to 235.139.255.254235.139.255.25532,766
25235.140.0.0/17235.140.0.1 to 235.140.127.254235.140.127.25532,766
26235.140.128.0/17235.140.128.1 to 235.140.255.254235.140.255.25532,766
27235.141.0.0/17235.141.0.1 to 235.141.127.254235.141.127.25532,766
28235.141.128.0/17235.141.128.1 to 235.141.255.254235.141.255.25532,766
29235.142.0.0/17235.142.0.1 to 235.142.127.254235.142.127.25532,766
30235.142.128.0/17235.142.128.1 to 235.142.255.254235.142.255.25532,766
31235.143.0.0/17235.143.0.1 to 235.143.127.254235.143.127.25532,766
32235.143.128.0/17235.143.128.1 to 235.143.255.254235.143.255.25532,766
33235.144.0.0/17235.144.0.1 to 235.144.127.254235.144.127.25532,766
34235.144.128.0/17235.144.128.1 to 235.144.255.254235.144.255.25532,766
35235.145.0.0/17235.145.0.1 to 235.145.127.254235.145.127.25532,766
36235.145.128.0/17235.145.128.1 to 235.145.255.254235.145.255.25532,766
37235.146.0.0/17235.146.0.1 to 235.146.127.254235.146.127.25532,766
38235.146.128.0/17235.146.128.1 to 235.146.255.254235.146.255.25532,766
39235.147.0.0/17235.147.0.1 to 235.147.127.254235.147.127.25532,766
40235.147.128.0/17235.147.128.1 to 235.147.255.254235.147.255.25532,766
41235.148.0.0/17235.148.0.1 to 235.148.127.254235.148.127.25532,766
42235.148.128.0/17235.148.128.1 to 235.148.255.254235.148.255.25532,766
43235.149.0.0/17235.149.0.1 to 235.149.127.254235.149.127.25532,766
44235.149.128.0/17235.149.128.1 to 235.149.255.254235.149.255.25532,766
45235.150.0.0/17235.150.0.1 to 235.150.127.254235.150.127.25532,766
46235.150.128.0/17235.150.128.1 to 235.150.255.254235.150.255.25532,766
47235.151.0.0/17235.151.0.1 to 235.151.127.254235.151.127.25532,766
48235.151.128.0/17235.151.128.1 to 235.151.255.254235.151.255.25532,766
49235.152.0.0/17235.152.0.1 to 235.152.127.254235.152.127.25532,766
50235.152.128.0/17235.152.128.1 to 235.152.255.254235.152.255.25532,766
51235.153.0.0/17235.153.0.1 to 235.153.127.254235.153.127.25532,766
52235.153.128.0/17235.153.128.1 to 235.153.255.254235.153.255.25532,766
53235.154.0.0/17235.154.0.1 to 235.154.127.254235.154.127.25532,766
54235.154.128.0/17235.154.128.1 to 235.154.255.254235.154.255.25532,766
55235.155.0.0/17235.155.0.1 to 235.155.127.254235.155.127.25532,766
56235.155.128.0/17235.155.128.1 to 235.155.255.254235.155.255.25532,766
57235.156.0.0/17235.156.0.1 to 235.156.127.254235.156.127.25532,766
58235.156.128.0/17235.156.128.1 to 235.156.255.254235.156.255.25532,766
59235.157.0.0/17235.157.0.1 to 235.157.127.254235.157.127.25532,766
60235.157.128.0/17235.157.128.1 to 235.157.255.254235.157.255.25532,766
61235.158.0.0/17235.158.0.1 to 235.158.127.254235.158.127.25532,766
62235.158.128.0/17235.158.128.1 to 235.158.255.254235.158.255.25532,766
63235.159.0.0/17235.159.0.1 to 235.159.127.254235.159.127.25532,766
64235.159.128.0/17235.159.128.1 to 235.159.255.254235.159.255.25532,766

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.