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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.

Network68.76.128.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
68.76.128.0
Broadcast address
68.76.255.255
First usable
68.76.128.1
Last usable
68.76.255.254
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
A (default /8)
As numbers
Hex 444C8000 · Integer 1145864192 to 1145896959
Reverse DNS zones
128.76.68.in-addr.arpa
129.76.68.in-addr.arpa
130.76.68.in-addr.arpa
131.76.68.in-addr.arpa
132.76.68.in-addr.arpa
133.76.68.in-addr.arpa
134.76.68.in-addr.arpa
135.76.68.in-addr.arpa
136.76.68.in-addr.arpa
137.76.68.in-addr.arpa
138.76.68.in-addr.arpa
139.76.68.in-addr.arpa
140.76.68.in-addr.arpa
141.76.68.in-addr.arpa
142.76.68.in-addr.arpa
143.76.68.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
Address01000100.01001100.10000000.0000000068.76.128.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network01000100.01001100.10000000.0000000068.76.128.0
Broadcast01000100.01001100.11111111.1111111168.76.255.255
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)

68.76.128.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
168.76.128.0/2468.76.128.1 to 68.76.128.25468.76.128.255254
268.76.129.0/2468.76.129.1 to 68.76.129.25468.76.129.255254
368.76.130.0/2468.76.130.1 to 68.76.130.25468.76.130.255254
468.76.131.0/2468.76.131.1 to 68.76.131.25468.76.131.255254
568.76.132.0/2468.76.132.1 to 68.76.132.25468.76.132.255254
668.76.133.0/2468.76.133.1 to 68.76.133.25468.76.133.255254
768.76.134.0/2468.76.134.1 to 68.76.134.25468.76.134.255254
868.76.135.0/2468.76.135.1 to 68.76.135.25468.76.135.255254
968.76.136.0/2468.76.136.1 to 68.76.136.25468.76.136.255254
1068.76.137.0/2468.76.137.1 to 68.76.137.25468.76.137.255254
1168.76.138.0/2468.76.138.1 to 68.76.138.25468.76.138.255254
1268.76.139.0/2468.76.139.1 to 68.76.139.25468.76.139.255254
1368.76.140.0/2468.76.140.1 to 68.76.140.25468.76.140.255254
1468.76.141.0/2468.76.141.1 to 68.76.141.25468.76.141.255254
1568.76.142.0/2468.76.142.1 to 68.76.142.25468.76.142.255254
1668.76.143.0/2468.76.143.1 to 68.76.143.25468.76.143.255254
1768.76.144.0/2468.76.144.1 to 68.76.144.25468.76.144.255254
1868.76.145.0/2468.76.145.1 to 68.76.145.25468.76.145.255254
1968.76.146.0/2468.76.146.1 to 68.76.146.25468.76.146.255254
2068.76.147.0/2468.76.147.1 to 68.76.147.25468.76.147.255254
2168.76.148.0/2468.76.148.1 to 68.76.148.25468.76.148.255254
2268.76.149.0/2468.76.149.1 to 68.76.149.25468.76.149.255254
2368.76.150.0/2468.76.150.1 to 68.76.150.25468.76.150.255254
2468.76.151.0/2468.76.151.1 to 68.76.151.25468.76.151.255254
2568.76.152.0/2468.76.152.1 to 68.76.152.25468.76.152.255254
2668.76.153.0/2468.76.153.1 to 68.76.153.25468.76.153.255254
2768.76.154.0/2468.76.154.1 to 68.76.154.25468.76.154.255254
2868.76.155.0/2468.76.155.1 to 68.76.155.25468.76.155.255254
2968.76.156.0/2468.76.156.1 to 68.76.156.25468.76.156.255254
3068.76.157.0/2468.76.157.1 to 68.76.157.25468.76.157.255254
3168.76.158.0/2468.76.158.1 to 68.76.158.25468.76.158.255254
3268.76.159.0/2468.76.159.1 to 68.76.159.25468.76.159.255254
3368.76.160.0/2468.76.160.1 to 68.76.160.25468.76.160.255254
3468.76.161.0/2468.76.161.1 to 68.76.161.25468.76.161.255254
3568.76.162.0/2468.76.162.1 to 68.76.162.25468.76.162.255254
3668.76.163.0/2468.76.163.1 to 68.76.163.25468.76.163.255254
3768.76.164.0/2468.76.164.1 to 68.76.164.25468.76.164.255254
3868.76.165.0/2468.76.165.1 to 68.76.165.25468.76.165.255254
3968.76.166.0/2468.76.166.1 to 68.76.166.25468.76.166.255254
4068.76.167.0/2468.76.167.1 to 68.76.167.25468.76.167.255254
4168.76.168.0/2468.76.168.1 to 68.76.168.25468.76.168.255254
4268.76.169.0/2468.76.169.1 to 68.76.169.25468.76.169.255254
4368.76.170.0/2468.76.170.1 to 68.76.170.25468.76.170.255254
4468.76.171.0/2468.76.171.1 to 68.76.171.25468.76.171.255254
4568.76.172.0/2468.76.172.1 to 68.76.172.25468.76.172.255254
4668.76.173.0/2468.76.173.1 to 68.76.173.25468.76.173.255254
4768.76.174.0/2468.76.174.1 to 68.76.174.25468.76.174.255254
4868.76.175.0/2468.76.175.1 to 68.76.175.25468.76.175.255254
4968.76.176.0/2468.76.176.1 to 68.76.176.25468.76.176.255254
5068.76.177.0/2468.76.177.1 to 68.76.177.25468.76.177.255254
5168.76.178.0/2468.76.178.1 to 68.76.178.25468.76.178.255254
5268.76.179.0/2468.76.179.1 to 68.76.179.25468.76.179.255254
5368.76.180.0/2468.76.180.1 to 68.76.180.25468.76.180.255254
5468.76.181.0/2468.76.181.1 to 68.76.181.25468.76.181.255254
5568.76.182.0/2468.76.182.1 to 68.76.182.25468.76.182.255254
5668.76.183.0/2468.76.183.1 to 68.76.183.25468.76.183.255254
5768.76.184.0/2468.76.184.1 to 68.76.184.25468.76.184.255254
5868.76.185.0/2468.76.185.1 to 68.76.185.25468.76.185.255254
5968.76.186.0/2468.76.186.1 to 68.76.186.25468.76.186.255254
6068.76.187.0/2468.76.187.1 to 68.76.187.25468.76.187.255254
6168.76.188.0/2468.76.188.1 to 68.76.188.25468.76.188.255254
6268.76.189.0/2468.76.189.1 to 68.76.189.25468.76.189.255254
6368.76.190.0/2468.76.190.1 to 68.76.190.25468.76.190.255254
6468.76.191.0/2468.76.191.1 to 68.76.191.25468.76.191.255254
6568.76.192.0/2468.76.192.1 to 68.76.192.25468.76.192.255254
6668.76.193.0/2468.76.193.1 to 68.76.193.25468.76.193.255254
6768.76.194.0/2468.76.194.1 to 68.76.194.25468.76.194.255254
6868.76.195.0/2468.76.195.1 to 68.76.195.25468.76.195.255254
6968.76.196.0/2468.76.196.1 to 68.76.196.25468.76.196.255254
7068.76.197.0/2468.76.197.1 to 68.76.197.25468.76.197.255254
7168.76.198.0/2468.76.198.1 to 68.76.198.25468.76.198.255254
7268.76.199.0/2468.76.199.1 to 68.76.199.25468.76.199.255254
7368.76.200.0/2468.76.200.1 to 68.76.200.25468.76.200.255254
7468.76.201.0/2468.76.201.1 to 68.76.201.25468.76.201.255254
7568.76.202.0/2468.76.202.1 to 68.76.202.25468.76.202.255254
7668.76.203.0/2468.76.203.1 to 68.76.203.25468.76.203.255254
7768.76.204.0/2468.76.204.1 to 68.76.204.25468.76.204.255254
7868.76.205.0/2468.76.205.1 to 68.76.205.25468.76.205.255254
7968.76.206.0/2468.76.206.1 to 68.76.206.25468.76.206.255254
8068.76.207.0/2468.76.207.1 to 68.76.207.25468.76.207.255254
8168.76.208.0/2468.76.208.1 to 68.76.208.25468.76.208.255254
8268.76.209.0/2468.76.209.1 to 68.76.209.25468.76.209.255254
8368.76.210.0/2468.76.210.1 to 68.76.210.25468.76.210.255254
8468.76.211.0/2468.76.211.1 to 68.76.211.25468.76.211.255254
8568.76.212.0/2468.76.212.1 to 68.76.212.25468.76.212.255254
8668.76.213.0/2468.76.213.1 to 68.76.213.25468.76.213.255254
8768.76.214.0/2468.76.214.1 to 68.76.214.25468.76.214.255254
8868.76.215.0/2468.76.215.1 to 68.76.215.25468.76.215.255254
8968.76.216.0/2468.76.216.1 to 68.76.216.25468.76.216.255254
9068.76.217.0/2468.76.217.1 to 68.76.217.25468.76.217.255254
9168.76.218.0/2468.76.218.1 to 68.76.218.25468.76.218.255254
9268.76.219.0/2468.76.219.1 to 68.76.219.25468.76.219.255254
9368.76.220.0/2468.76.220.1 to 68.76.220.25468.76.220.255254
9468.76.221.0/2468.76.221.1 to 68.76.221.25468.76.221.255254
9568.76.222.0/2468.76.222.1 to 68.76.222.25468.76.222.255254
9668.76.223.0/2468.76.223.1 to 68.76.223.25468.76.223.255254
9768.76.224.0/2468.76.224.1 to 68.76.224.25468.76.224.255254
9868.76.225.0/2468.76.225.1 to 68.76.225.25468.76.225.255254
9968.76.226.0/2468.76.226.1 to 68.76.226.25468.76.226.255254
10068.76.227.0/2468.76.227.1 to 68.76.227.25468.76.227.255254
10168.76.228.0/2468.76.228.1 to 68.76.228.25468.76.228.255254
10268.76.229.0/2468.76.229.1 to 68.76.229.25468.76.229.255254
10368.76.230.0/2468.76.230.1 to 68.76.230.25468.76.230.255254
10468.76.231.0/2468.76.231.1 to 68.76.231.25468.76.231.255254
10568.76.232.0/2468.76.232.1 to 68.76.232.25468.76.232.255254
10668.76.233.0/2468.76.233.1 to 68.76.233.25468.76.233.255254
10768.76.234.0/2468.76.234.1 to 68.76.234.25468.76.234.255254
10868.76.235.0/2468.76.235.1 to 68.76.235.25468.76.235.255254
10968.76.236.0/2468.76.236.1 to 68.76.236.25468.76.236.255254
11068.76.237.0/2468.76.237.1 to 68.76.237.25468.76.237.255254
11168.76.238.0/2468.76.238.1 to 68.76.238.25468.76.238.255254
11268.76.239.0/2468.76.239.1 to 68.76.239.25468.76.239.255254
11368.76.240.0/2468.76.240.1 to 68.76.240.25468.76.240.255254
11468.76.241.0/2468.76.241.1 to 68.76.241.25468.76.241.255254
11568.76.242.0/2468.76.242.1 to 68.76.242.25468.76.242.255254
11668.76.243.0/2468.76.243.1 to 68.76.243.25468.76.243.255254
11768.76.244.0/2468.76.244.1 to 68.76.244.25468.76.244.255254
11868.76.245.0/2468.76.245.1 to 68.76.245.25468.76.245.255254
11968.76.246.0/2468.76.246.1 to 68.76.246.25468.76.246.255254
12068.76.247.0/2468.76.247.1 to 68.76.247.25468.76.247.255254
12168.76.248.0/2468.76.248.1 to 68.76.248.25468.76.248.255254
12268.76.249.0/2468.76.249.1 to 68.76.249.25468.76.249.255254
12368.76.250.0/2468.76.250.1 to 68.76.250.25468.76.250.255254
12468.76.251.0/2468.76.251.1 to 68.76.251.25468.76.251.255254
12568.76.252.0/2468.76.252.1 to 68.76.252.25468.76.252.255254
12668.76.253.0/2468.76.253.1 to 68.76.253.25468.76.253.255254
12768.76.254.0/2468.76.254.1 to 68.76.254.25468.76.254.255254
12868.76.255.0/2468.76.255.1 to 68.76.255.25468.76.255.255254

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.