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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.

Network198.19.128.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
198.19.128.0
Broadcast address
198.19.255.255
First usable
198.19.128.1
Last usable
198.19.255.254
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
Benchmarking 198.18.0.0/15
Network equipment testing (RFC 2544)
Old class
C (default /24)
As numbers
Hex C6138000 · Integer 3323166720 to 3323199487
Reverse DNS zones
128.19.198.in-addr.arpa
129.19.198.in-addr.arpa
130.19.198.in-addr.arpa
131.19.198.in-addr.arpa
132.19.198.in-addr.arpa
133.19.198.in-addr.arpa
134.19.198.in-addr.arpa
135.19.198.in-addr.arpa
136.19.198.in-addr.arpa
137.19.198.in-addr.arpa
138.19.198.in-addr.arpa
139.19.198.in-addr.arpa
140.19.198.in-addr.arpa
141.19.198.in-addr.arpa
142.19.198.in-addr.arpa
143.19.198.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
Address11000110.00010011.10000000.00000000198.19.128.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network11000110.00010011.10000000.00000000198.19.128.0
Broadcast11000110.00010011.11111111.11111111198.19.255.255
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)

198.19.128.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1198.19.128.0/24198.19.128.1 to 198.19.128.254198.19.128.255254
2198.19.129.0/24198.19.129.1 to 198.19.129.254198.19.129.255254
3198.19.130.0/24198.19.130.1 to 198.19.130.254198.19.130.255254
4198.19.131.0/24198.19.131.1 to 198.19.131.254198.19.131.255254
5198.19.132.0/24198.19.132.1 to 198.19.132.254198.19.132.255254
6198.19.133.0/24198.19.133.1 to 198.19.133.254198.19.133.255254
7198.19.134.0/24198.19.134.1 to 198.19.134.254198.19.134.255254
8198.19.135.0/24198.19.135.1 to 198.19.135.254198.19.135.255254
9198.19.136.0/24198.19.136.1 to 198.19.136.254198.19.136.255254
10198.19.137.0/24198.19.137.1 to 198.19.137.254198.19.137.255254
11198.19.138.0/24198.19.138.1 to 198.19.138.254198.19.138.255254
12198.19.139.0/24198.19.139.1 to 198.19.139.254198.19.139.255254
13198.19.140.0/24198.19.140.1 to 198.19.140.254198.19.140.255254
14198.19.141.0/24198.19.141.1 to 198.19.141.254198.19.141.255254
15198.19.142.0/24198.19.142.1 to 198.19.142.254198.19.142.255254
16198.19.143.0/24198.19.143.1 to 198.19.143.254198.19.143.255254
17198.19.144.0/24198.19.144.1 to 198.19.144.254198.19.144.255254
18198.19.145.0/24198.19.145.1 to 198.19.145.254198.19.145.255254
19198.19.146.0/24198.19.146.1 to 198.19.146.254198.19.146.255254
20198.19.147.0/24198.19.147.1 to 198.19.147.254198.19.147.255254
21198.19.148.0/24198.19.148.1 to 198.19.148.254198.19.148.255254
22198.19.149.0/24198.19.149.1 to 198.19.149.254198.19.149.255254
23198.19.150.0/24198.19.150.1 to 198.19.150.254198.19.150.255254
24198.19.151.0/24198.19.151.1 to 198.19.151.254198.19.151.255254
25198.19.152.0/24198.19.152.1 to 198.19.152.254198.19.152.255254
26198.19.153.0/24198.19.153.1 to 198.19.153.254198.19.153.255254
27198.19.154.0/24198.19.154.1 to 198.19.154.254198.19.154.255254
28198.19.155.0/24198.19.155.1 to 198.19.155.254198.19.155.255254
29198.19.156.0/24198.19.156.1 to 198.19.156.254198.19.156.255254
30198.19.157.0/24198.19.157.1 to 198.19.157.254198.19.157.255254
31198.19.158.0/24198.19.158.1 to 198.19.158.254198.19.158.255254
32198.19.159.0/24198.19.159.1 to 198.19.159.254198.19.159.255254
33198.19.160.0/24198.19.160.1 to 198.19.160.254198.19.160.255254
34198.19.161.0/24198.19.161.1 to 198.19.161.254198.19.161.255254
35198.19.162.0/24198.19.162.1 to 198.19.162.254198.19.162.255254
36198.19.163.0/24198.19.163.1 to 198.19.163.254198.19.163.255254
37198.19.164.0/24198.19.164.1 to 198.19.164.254198.19.164.255254
38198.19.165.0/24198.19.165.1 to 198.19.165.254198.19.165.255254
39198.19.166.0/24198.19.166.1 to 198.19.166.254198.19.166.255254
40198.19.167.0/24198.19.167.1 to 198.19.167.254198.19.167.255254
41198.19.168.0/24198.19.168.1 to 198.19.168.254198.19.168.255254
42198.19.169.0/24198.19.169.1 to 198.19.169.254198.19.169.255254
43198.19.170.0/24198.19.170.1 to 198.19.170.254198.19.170.255254
44198.19.171.0/24198.19.171.1 to 198.19.171.254198.19.171.255254
45198.19.172.0/24198.19.172.1 to 198.19.172.254198.19.172.255254
46198.19.173.0/24198.19.173.1 to 198.19.173.254198.19.173.255254
47198.19.174.0/24198.19.174.1 to 198.19.174.254198.19.174.255254
48198.19.175.0/24198.19.175.1 to 198.19.175.254198.19.175.255254
49198.19.176.0/24198.19.176.1 to 198.19.176.254198.19.176.255254
50198.19.177.0/24198.19.177.1 to 198.19.177.254198.19.177.255254
51198.19.178.0/24198.19.178.1 to 198.19.178.254198.19.178.255254
52198.19.179.0/24198.19.179.1 to 198.19.179.254198.19.179.255254
53198.19.180.0/24198.19.180.1 to 198.19.180.254198.19.180.255254
54198.19.181.0/24198.19.181.1 to 198.19.181.254198.19.181.255254
55198.19.182.0/24198.19.182.1 to 198.19.182.254198.19.182.255254
56198.19.183.0/24198.19.183.1 to 198.19.183.254198.19.183.255254
57198.19.184.0/24198.19.184.1 to 198.19.184.254198.19.184.255254
58198.19.185.0/24198.19.185.1 to 198.19.185.254198.19.185.255254
59198.19.186.0/24198.19.186.1 to 198.19.186.254198.19.186.255254
60198.19.187.0/24198.19.187.1 to 198.19.187.254198.19.187.255254
61198.19.188.0/24198.19.188.1 to 198.19.188.254198.19.188.255254
62198.19.189.0/24198.19.189.1 to 198.19.189.254198.19.189.255254
63198.19.190.0/24198.19.190.1 to 198.19.190.254198.19.190.255254
64198.19.191.0/24198.19.191.1 to 198.19.191.254198.19.191.255254
65198.19.192.0/24198.19.192.1 to 198.19.192.254198.19.192.255254
66198.19.193.0/24198.19.193.1 to 198.19.193.254198.19.193.255254
67198.19.194.0/24198.19.194.1 to 198.19.194.254198.19.194.255254
68198.19.195.0/24198.19.195.1 to 198.19.195.254198.19.195.255254
69198.19.196.0/24198.19.196.1 to 198.19.196.254198.19.196.255254
70198.19.197.0/24198.19.197.1 to 198.19.197.254198.19.197.255254
71198.19.198.0/24198.19.198.1 to 198.19.198.254198.19.198.255254
72198.19.199.0/24198.19.199.1 to 198.19.199.254198.19.199.255254
73198.19.200.0/24198.19.200.1 to 198.19.200.254198.19.200.255254
74198.19.201.0/24198.19.201.1 to 198.19.201.254198.19.201.255254
75198.19.202.0/24198.19.202.1 to 198.19.202.254198.19.202.255254
76198.19.203.0/24198.19.203.1 to 198.19.203.254198.19.203.255254
77198.19.204.0/24198.19.204.1 to 198.19.204.254198.19.204.255254
78198.19.205.0/24198.19.205.1 to 198.19.205.254198.19.205.255254
79198.19.206.0/24198.19.206.1 to 198.19.206.254198.19.206.255254
80198.19.207.0/24198.19.207.1 to 198.19.207.254198.19.207.255254
81198.19.208.0/24198.19.208.1 to 198.19.208.254198.19.208.255254
82198.19.209.0/24198.19.209.1 to 198.19.209.254198.19.209.255254
83198.19.210.0/24198.19.210.1 to 198.19.210.254198.19.210.255254
84198.19.211.0/24198.19.211.1 to 198.19.211.254198.19.211.255254
85198.19.212.0/24198.19.212.1 to 198.19.212.254198.19.212.255254
86198.19.213.0/24198.19.213.1 to 198.19.213.254198.19.213.255254
87198.19.214.0/24198.19.214.1 to 198.19.214.254198.19.214.255254
88198.19.215.0/24198.19.215.1 to 198.19.215.254198.19.215.255254
89198.19.216.0/24198.19.216.1 to 198.19.216.254198.19.216.255254
90198.19.217.0/24198.19.217.1 to 198.19.217.254198.19.217.255254
91198.19.218.0/24198.19.218.1 to 198.19.218.254198.19.218.255254
92198.19.219.0/24198.19.219.1 to 198.19.219.254198.19.219.255254
93198.19.220.0/24198.19.220.1 to 198.19.220.254198.19.220.255254
94198.19.221.0/24198.19.221.1 to 198.19.221.254198.19.221.255254
95198.19.222.0/24198.19.222.1 to 198.19.222.254198.19.222.255254
96198.19.223.0/24198.19.223.1 to 198.19.223.254198.19.223.255254
97198.19.224.0/24198.19.224.1 to 198.19.224.254198.19.224.255254
98198.19.225.0/24198.19.225.1 to 198.19.225.254198.19.225.255254
99198.19.226.0/24198.19.226.1 to 198.19.226.254198.19.226.255254
100198.19.227.0/24198.19.227.1 to 198.19.227.254198.19.227.255254
101198.19.228.0/24198.19.228.1 to 198.19.228.254198.19.228.255254
102198.19.229.0/24198.19.229.1 to 198.19.229.254198.19.229.255254
103198.19.230.0/24198.19.230.1 to 198.19.230.254198.19.230.255254
104198.19.231.0/24198.19.231.1 to 198.19.231.254198.19.231.255254
105198.19.232.0/24198.19.232.1 to 198.19.232.254198.19.232.255254
106198.19.233.0/24198.19.233.1 to 198.19.233.254198.19.233.255254
107198.19.234.0/24198.19.234.1 to 198.19.234.254198.19.234.255254
108198.19.235.0/24198.19.235.1 to 198.19.235.254198.19.235.255254
109198.19.236.0/24198.19.236.1 to 198.19.236.254198.19.236.255254
110198.19.237.0/24198.19.237.1 to 198.19.237.254198.19.237.255254
111198.19.238.0/24198.19.238.1 to 198.19.238.254198.19.238.255254
112198.19.239.0/24198.19.239.1 to 198.19.239.254198.19.239.255254
113198.19.240.0/24198.19.240.1 to 198.19.240.254198.19.240.255254
114198.19.241.0/24198.19.241.1 to 198.19.241.254198.19.241.255254
115198.19.242.0/24198.19.242.1 to 198.19.242.254198.19.242.255254
116198.19.243.0/24198.19.243.1 to 198.19.243.254198.19.243.255254
117198.19.244.0/24198.19.244.1 to 198.19.244.254198.19.244.255254
118198.19.245.0/24198.19.245.1 to 198.19.245.254198.19.245.255254
119198.19.246.0/24198.19.246.1 to 198.19.246.254198.19.246.255254
120198.19.247.0/24198.19.247.1 to 198.19.247.254198.19.247.255254
121198.19.248.0/24198.19.248.1 to 198.19.248.254198.19.248.255254
122198.19.249.0/24198.19.249.1 to 198.19.249.254198.19.249.255254
123198.19.250.0/24198.19.250.1 to 198.19.250.254198.19.250.255254
124198.19.251.0/24198.19.251.1 to 198.19.251.254198.19.251.255254
125198.19.252.0/24198.19.252.1 to 198.19.252.254198.19.252.255254
126198.19.253.0/24198.19.253.1 to 198.19.253.254198.19.253.255254
127198.19.254.0/24198.19.254.1 to 198.19.254.254198.19.254.255254
128198.19.255.0/24198.19.255.1 to 198.19.255.254198.19.255.255254

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.