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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.

Network170.6.192.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
170.6.192.0
Broadcast address
170.6.207.255
First usable
170.6.192.1
Last usable
170.6.207.254
Usable hosts
4,094 (4,096 less the network and broadcast addresses)
Subnet mask
255.255.240.0
Wildcard mask
0.0.15.255 (Cisco ACLs, OSPF)
Prefix length
/20
Type
Public public
Old class
B (default /16)
As numbers
Hex AA06C000 · Integer 2852569088 to 2852573183
Reverse DNS zones
192.6.170.in-addr.arpa
193.6.170.in-addr.arpa
194.6.170.in-addr.arpa
195.6.170.in-addr.arpa
196.6.170.in-addr.arpa
197.6.170.in-addr.arpa
198.6.170.in-addr.arpa
199.6.170.in-addr.arpa
200.6.170.in-addr.arpa
201.6.170.in-addr.arpa
202.6.170.in-addr.arpa
203.6.170.in-addr.arpa
204.6.170.in-addr.arpa
205.6.170.in-addr.arpa
206.6.170.in-addr.arpa
207.6.170.in-addr.arpa
/20 is not on a 8-bit boundary, so it takes 16 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10101010.00000110.11000000.00000000170.6.192.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network10101010.00000110.11000000.00000000170.6.192.0
Broadcast10101010.00000110.11001111.11111111170.6.207.255
Split into smaller subnets/27
/21 (2)/22 (4)/23 (8)/24 (16)/25 (32)/26 (64)/27 (128)/28 (256)/29 (512)/30 (1,024)/31 (2,048)/32 (4,096)

170.6.192.0/20 makes 128 subnets of /27.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1170.6.192.0/27170.6.192.1 to 170.6.192.30170.6.192.3130
2170.6.192.32/27170.6.192.33 to 170.6.192.62170.6.192.6330
3170.6.192.64/27170.6.192.65 to 170.6.192.94170.6.192.9530
4170.6.192.96/27170.6.192.97 to 170.6.192.126170.6.192.12730
5170.6.192.128/27170.6.192.129 to 170.6.192.158170.6.192.15930
6170.6.192.160/27170.6.192.161 to 170.6.192.190170.6.192.19130
7170.6.192.192/27170.6.192.193 to 170.6.192.222170.6.192.22330
8170.6.192.224/27170.6.192.225 to 170.6.192.254170.6.192.25530
9170.6.193.0/27170.6.193.1 to 170.6.193.30170.6.193.3130
10170.6.193.32/27170.6.193.33 to 170.6.193.62170.6.193.6330
11170.6.193.64/27170.6.193.65 to 170.6.193.94170.6.193.9530
12170.6.193.96/27170.6.193.97 to 170.6.193.126170.6.193.12730
13170.6.193.128/27170.6.193.129 to 170.6.193.158170.6.193.15930
14170.6.193.160/27170.6.193.161 to 170.6.193.190170.6.193.19130
15170.6.193.192/27170.6.193.193 to 170.6.193.222170.6.193.22330
16170.6.193.224/27170.6.193.225 to 170.6.193.254170.6.193.25530
17170.6.194.0/27170.6.194.1 to 170.6.194.30170.6.194.3130
18170.6.194.32/27170.6.194.33 to 170.6.194.62170.6.194.6330
19170.6.194.64/27170.6.194.65 to 170.6.194.94170.6.194.9530
20170.6.194.96/27170.6.194.97 to 170.6.194.126170.6.194.12730
21170.6.194.128/27170.6.194.129 to 170.6.194.158170.6.194.15930
22170.6.194.160/27170.6.194.161 to 170.6.194.190170.6.194.19130
23170.6.194.192/27170.6.194.193 to 170.6.194.222170.6.194.22330
24170.6.194.224/27170.6.194.225 to 170.6.194.254170.6.194.25530
25170.6.195.0/27170.6.195.1 to 170.6.195.30170.6.195.3130
26170.6.195.32/27170.6.195.33 to 170.6.195.62170.6.195.6330
27170.6.195.64/27170.6.195.65 to 170.6.195.94170.6.195.9530
28170.6.195.96/27170.6.195.97 to 170.6.195.126170.6.195.12730
29170.6.195.128/27170.6.195.129 to 170.6.195.158170.6.195.15930
30170.6.195.160/27170.6.195.161 to 170.6.195.190170.6.195.19130
31170.6.195.192/27170.6.195.193 to 170.6.195.222170.6.195.22330
32170.6.195.224/27170.6.195.225 to 170.6.195.254170.6.195.25530
33170.6.196.0/27170.6.196.1 to 170.6.196.30170.6.196.3130
34170.6.196.32/27170.6.196.33 to 170.6.196.62170.6.196.6330
35170.6.196.64/27170.6.196.65 to 170.6.196.94170.6.196.9530
36170.6.196.96/27170.6.196.97 to 170.6.196.126170.6.196.12730
37170.6.196.128/27170.6.196.129 to 170.6.196.158170.6.196.15930
38170.6.196.160/27170.6.196.161 to 170.6.196.190170.6.196.19130
39170.6.196.192/27170.6.196.193 to 170.6.196.222170.6.196.22330
40170.6.196.224/27170.6.196.225 to 170.6.196.254170.6.196.25530
41170.6.197.0/27170.6.197.1 to 170.6.197.30170.6.197.3130
42170.6.197.32/27170.6.197.33 to 170.6.197.62170.6.197.6330
43170.6.197.64/27170.6.197.65 to 170.6.197.94170.6.197.9530
44170.6.197.96/27170.6.197.97 to 170.6.197.126170.6.197.12730
45170.6.197.128/27170.6.197.129 to 170.6.197.158170.6.197.15930
46170.6.197.160/27170.6.197.161 to 170.6.197.190170.6.197.19130
47170.6.197.192/27170.6.197.193 to 170.6.197.222170.6.197.22330
48170.6.197.224/27170.6.197.225 to 170.6.197.254170.6.197.25530
49170.6.198.0/27170.6.198.1 to 170.6.198.30170.6.198.3130
50170.6.198.32/27170.6.198.33 to 170.6.198.62170.6.198.6330
51170.6.198.64/27170.6.198.65 to 170.6.198.94170.6.198.9530
52170.6.198.96/27170.6.198.97 to 170.6.198.126170.6.198.12730
53170.6.198.128/27170.6.198.129 to 170.6.198.158170.6.198.15930
54170.6.198.160/27170.6.198.161 to 170.6.198.190170.6.198.19130
55170.6.198.192/27170.6.198.193 to 170.6.198.222170.6.198.22330
56170.6.198.224/27170.6.198.225 to 170.6.198.254170.6.198.25530
57170.6.199.0/27170.6.199.1 to 170.6.199.30170.6.199.3130
58170.6.199.32/27170.6.199.33 to 170.6.199.62170.6.199.6330
59170.6.199.64/27170.6.199.65 to 170.6.199.94170.6.199.9530
60170.6.199.96/27170.6.199.97 to 170.6.199.126170.6.199.12730
61170.6.199.128/27170.6.199.129 to 170.6.199.158170.6.199.15930
62170.6.199.160/27170.6.199.161 to 170.6.199.190170.6.199.19130
63170.6.199.192/27170.6.199.193 to 170.6.199.222170.6.199.22330
64170.6.199.224/27170.6.199.225 to 170.6.199.254170.6.199.25530
65170.6.200.0/27170.6.200.1 to 170.6.200.30170.6.200.3130
66170.6.200.32/27170.6.200.33 to 170.6.200.62170.6.200.6330
67170.6.200.64/27170.6.200.65 to 170.6.200.94170.6.200.9530
68170.6.200.96/27170.6.200.97 to 170.6.200.126170.6.200.12730
69170.6.200.128/27170.6.200.129 to 170.6.200.158170.6.200.15930
70170.6.200.160/27170.6.200.161 to 170.6.200.190170.6.200.19130
71170.6.200.192/27170.6.200.193 to 170.6.200.222170.6.200.22330
72170.6.200.224/27170.6.200.225 to 170.6.200.254170.6.200.25530
73170.6.201.0/27170.6.201.1 to 170.6.201.30170.6.201.3130
74170.6.201.32/27170.6.201.33 to 170.6.201.62170.6.201.6330
75170.6.201.64/27170.6.201.65 to 170.6.201.94170.6.201.9530
76170.6.201.96/27170.6.201.97 to 170.6.201.126170.6.201.12730
77170.6.201.128/27170.6.201.129 to 170.6.201.158170.6.201.15930
78170.6.201.160/27170.6.201.161 to 170.6.201.190170.6.201.19130
79170.6.201.192/27170.6.201.193 to 170.6.201.222170.6.201.22330
80170.6.201.224/27170.6.201.225 to 170.6.201.254170.6.201.25530
81170.6.202.0/27170.6.202.1 to 170.6.202.30170.6.202.3130
82170.6.202.32/27170.6.202.33 to 170.6.202.62170.6.202.6330
83170.6.202.64/27170.6.202.65 to 170.6.202.94170.6.202.9530
84170.6.202.96/27170.6.202.97 to 170.6.202.126170.6.202.12730
85170.6.202.128/27170.6.202.129 to 170.6.202.158170.6.202.15930
86170.6.202.160/27170.6.202.161 to 170.6.202.190170.6.202.19130
87170.6.202.192/27170.6.202.193 to 170.6.202.222170.6.202.22330
88170.6.202.224/27170.6.202.225 to 170.6.202.254170.6.202.25530
89170.6.203.0/27170.6.203.1 to 170.6.203.30170.6.203.3130
90170.6.203.32/27170.6.203.33 to 170.6.203.62170.6.203.6330
91170.6.203.64/27170.6.203.65 to 170.6.203.94170.6.203.9530
92170.6.203.96/27170.6.203.97 to 170.6.203.126170.6.203.12730
93170.6.203.128/27170.6.203.129 to 170.6.203.158170.6.203.15930
94170.6.203.160/27170.6.203.161 to 170.6.203.190170.6.203.19130
95170.6.203.192/27170.6.203.193 to 170.6.203.222170.6.203.22330
96170.6.203.224/27170.6.203.225 to 170.6.203.254170.6.203.25530
97170.6.204.0/27170.6.204.1 to 170.6.204.30170.6.204.3130
98170.6.204.32/27170.6.204.33 to 170.6.204.62170.6.204.6330
99170.6.204.64/27170.6.204.65 to 170.6.204.94170.6.204.9530
100170.6.204.96/27170.6.204.97 to 170.6.204.126170.6.204.12730
101170.6.204.128/27170.6.204.129 to 170.6.204.158170.6.204.15930
102170.6.204.160/27170.6.204.161 to 170.6.204.190170.6.204.19130
103170.6.204.192/27170.6.204.193 to 170.6.204.222170.6.204.22330
104170.6.204.224/27170.6.204.225 to 170.6.204.254170.6.204.25530
105170.6.205.0/27170.6.205.1 to 170.6.205.30170.6.205.3130
106170.6.205.32/27170.6.205.33 to 170.6.205.62170.6.205.6330
107170.6.205.64/27170.6.205.65 to 170.6.205.94170.6.205.9530
108170.6.205.96/27170.6.205.97 to 170.6.205.126170.6.205.12730
109170.6.205.128/27170.6.205.129 to 170.6.205.158170.6.205.15930
110170.6.205.160/27170.6.205.161 to 170.6.205.190170.6.205.19130
111170.6.205.192/27170.6.205.193 to 170.6.205.222170.6.205.22330
112170.6.205.224/27170.6.205.225 to 170.6.205.254170.6.205.25530
113170.6.206.0/27170.6.206.1 to 170.6.206.30170.6.206.3130
114170.6.206.32/27170.6.206.33 to 170.6.206.62170.6.206.6330
115170.6.206.64/27170.6.206.65 to 170.6.206.94170.6.206.9530
116170.6.206.96/27170.6.206.97 to 170.6.206.126170.6.206.12730
117170.6.206.128/27170.6.206.129 to 170.6.206.158170.6.206.15930
118170.6.206.160/27170.6.206.161 to 170.6.206.190170.6.206.19130
119170.6.206.192/27170.6.206.193 to 170.6.206.222170.6.206.22330
120170.6.206.224/27170.6.206.225 to 170.6.206.254170.6.206.25530
121170.6.207.0/27170.6.207.1 to 170.6.207.30170.6.207.3130
122170.6.207.32/27170.6.207.33 to 170.6.207.62170.6.207.6330
123170.6.207.64/27170.6.207.65 to 170.6.207.94170.6.207.9530
124170.6.207.96/27170.6.207.97 to 170.6.207.126170.6.207.12730
125170.6.207.128/27170.6.207.129 to 170.6.207.158170.6.207.15930
126170.6.207.160/27170.6.207.161 to 170.6.207.190170.6.207.19130
127170.6.207.192/27170.6.207.193 to 170.6.207.222170.6.207.22330
128170.6.207.224/27170.6.207.225 to 170.6.207.254170.6.207.25530

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.