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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.

Network234.167.176.0/21
Usable hosts2,046
Subnet mask255.255.248.0
Addresses2,048
Network address
234.167.176.0
Broadcast address
234.167.183.255
First usable
234.167.176.1
Last usable
234.167.183.254
Usable hosts
2,046 (2,048 less the network and broadcast addresses)
Subnet mask
255.255.248.0
Wildcard mask
0.0.7.255 (Cisco ACLs, OSPF)
Prefix length
/21
Type
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex EAA7B000 · Integer 3936858112 to 3936860159
Reverse DNS zones
176.167.234.in-addr.arpa
177.167.234.in-addr.arpa
178.167.234.in-addr.arpa
179.167.234.in-addr.arpa
180.167.234.in-addr.arpa
181.167.234.in-addr.arpa
182.167.234.in-addr.arpa
183.167.234.in-addr.arpa
/21 is not on a 8-bit boundary, so it takes 8 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11101010.10100111.10110000.00000000234.167.176.0
Subnet mask11111111.11111111.11111000.00000000255.255.248.0
Network11101010.10100111.10110000.00000000234.167.176.0
Broadcast11101010.10100111.10110111.11111111234.167.183.255
Split into smaller subnets/28
/22 (2)/23 (4)/24 (8)/25 (16)/26 (32)/27 (64)/28 (128)/29 (256)/30 (512)/31 (1,024)/32 (2,048)

234.167.176.0/21 makes 128 subnets of /28.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1234.167.176.0/28234.167.176.1 to 234.167.176.14234.167.176.1514
2234.167.176.16/28234.167.176.17 to 234.167.176.30234.167.176.3114
3234.167.176.32/28234.167.176.33 to 234.167.176.46234.167.176.4714
4234.167.176.48/28234.167.176.49 to 234.167.176.62234.167.176.6314
5234.167.176.64/28234.167.176.65 to 234.167.176.78234.167.176.7914
6234.167.176.80/28234.167.176.81 to 234.167.176.94234.167.176.9514
7234.167.176.96/28234.167.176.97 to 234.167.176.110234.167.176.11114
8234.167.176.112/28234.167.176.113 to 234.167.176.126234.167.176.12714
9234.167.176.128/28234.167.176.129 to 234.167.176.142234.167.176.14314
10234.167.176.144/28234.167.176.145 to 234.167.176.158234.167.176.15914
11234.167.176.160/28234.167.176.161 to 234.167.176.174234.167.176.17514
12234.167.176.176/28234.167.176.177 to 234.167.176.190234.167.176.19114
13234.167.176.192/28234.167.176.193 to 234.167.176.206234.167.176.20714
14234.167.176.208/28234.167.176.209 to 234.167.176.222234.167.176.22314
15234.167.176.224/28234.167.176.225 to 234.167.176.238234.167.176.23914
16234.167.176.240/28234.167.176.241 to 234.167.176.254234.167.176.25514
17234.167.177.0/28234.167.177.1 to 234.167.177.14234.167.177.1514
18234.167.177.16/28234.167.177.17 to 234.167.177.30234.167.177.3114
19234.167.177.32/28234.167.177.33 to 234.167.177.46234.167.177.4714
20234.167.177.48/28234.167.177.49 to 234.167.177.62234.167.177.6314
21234.167.177.64/28234.167.177.65 to 234.167.177.78234.167.177.7914
22234.167.177.80/28234.167.177.81 to 234.167.177.94234.167.177.9514
23234.167.177.96/28234.167.177.97 to 234.167.177.110234.167.177.11114
24234.167.177.112/28234.167.177.113 to 234.167.177.126234.167.177.12714
25234.167.177.128/28234.167.177.129 to 234.167.177.142234.167.177.14314
26234.167.177.144/28234.167.177.145 to 234.167.177.158234.167.177.15914
27234.167.177.160/28234.167.177.161 to 234.167.177.174234.167.177.17514
28234.167.177.176/28234.167.177.177 to 234.167.177.190234.167.177.19114
29234.167.177.192/28234.167.177.193 to 234.167.177.206234.167.177.20714
30234.167.177.208/28234.167.177.209 to 234.167.177.222234.167.177.22314
31234.167.177.224/28234.167.177.225 to 234.167.177.238234.167.177.23914
32234.167.177.240/28234.167.177.241 to 234.167.177.254234.167.177.25514
33234.167.178.0/28234.167.178.1 to 234.167.178.14234.167.178.1514
34234.167.178.16/28234.167.178.17 to 234.167.178.30234.167.178.3114
35234.167.178.32/28234.167.178.33 to 234.167.178.46234.167.178.4714
36234.167.178.48/28234.167.178.49 to 234.167.178.62234.167.178.6314
37234.167.178.64/28234.167.178.65 to 234.167.178.78234.167.178.7914
38234.167.178.80/28234.167.178.81 to 234.167.178.94234.167.178.9514
39234.167.178.96/28234.167.178.97 to 234.167.178.110234.167.178.11114
40234.167.178.112/28234.167.178.113 to 234.167.178.126234.167.178.12714
41234.167.178.128/28234.167.178.129 to 234.167.178.142234.167.178.14314
42234.167.178.144/28234.167.178.145 to 234.167.178.158234.167.178.15914
43234.167.178.160/28234.167.178.161 to 234.167.178.174234.167.178.17514
44234.167.178.176/28234.167.178.177 to 234.167.178.190234.167.178.19114
45234.167.178.192/28234.167.178.193 to 234.167.178.206234.167.178.20714
46234.167.178.208/28234.167.178.209 to 234.167.178.222234.167.178.22314
47234.167.178.224/28234.167.178.225 to 234.167.178.238234.167.178.23914
48234.167.178.240/28234.167.178.241 to 234.167.178.254234.167.178.25514
49234.167.179.0/28234.167.179.1 to 234.167.179.14234.167.179.1514
50234.167.179.16/28234.167.179.17 to 234.167.179.30234.167.179.3114
51234.167.179.32/28234.167.179.33 to 234.167.179.46234.167.179.4714
52234.167.179.48/28234.167.179.49 to 234.167.179.62234.167.179.6314
53234.167.179.64/28234.167.179.65 to 234.167.179.78234.167.179.7914
54234.167.179.80/28234.167.179.81 to 234.167.179.94234.167.179.9514
55234.167.179.96/28234.167.179.97 to 234.167.179.110234.167.179.11114
56234.167.179.112/28234.167.179.113 to 234.167.179.126234.167.179.12714
57234.167.179.128/28234.167.179.129 to 234.167.179.142234.167.179.14314
58234.167.179.144/28234.167.179.145 to 234.167.179.158234.167.179.15914
59234.167.179.160/28234.167.179.161 to 234.167.179.174234.167.179.17514
60234.167.179.176/28234.167.179.177 to 234.167.179.190234.167.179.19114
61234.167.179.192/28234.167.179.193 to 234.167.179.206234.167.179.20714
62234.167.179.208/28234.167.179.209 to 234.167.179.222234.167.179.22314
63234.167.179.224/28234.167.179.225 to 234.167.179.238234.167.179.23914
64234.167.179.240/28234.167.179.241 to 234.167.179.254234.167.179.25514
65234.167.180.0/28234.167.180.1 to 234.167.180.14234.167.180.1514
66234.167.180.16/28234.167.180.17 to 234.167.180.30234.167.180.3114
67234.167.180.32/28234.167.180.33 to 234.167.180.46234.167.180.4714
68234.167.180.48/28234.167.180.49 to 234.167.180.62234.167.180.6314
69234.167.180.64/28234.167.180.65 to 234.167.180.78234.167.180.7914
70234.167.180.80/28234.167.180.81 to 234.167.180.94234.167.180.9514
71234.167.180.96/28234.167.180.97 to 234.167.180.110234.167.180.11114
72234.167.180.112/28234.167.180.113 to 234.167.180.126234.167.180.12714
73234.167.180.128/28234.167.180.129 to 234.167.180.142234.167.180.14314
74234.167.180.144/28234.167.180.145 to 234.167.180.158234.167.180.15914
75234.167.180.160/28234.167.180.161 to 234.167.180.174234.167.180.17514
76234.167.180.176/28234.167.180.177 to 234.167.180.190234.167.180.19114
77234.167.180.192/28234.167.180.193 to 234.167.180.206234.167.180.20714
78234.167.180.208/28234.167.180.209 to 234.167.180.222234.167.180.22314
79234.167.180.224/28234.167.180.225 to 234.167.180.238234.167.180.23914
80234.167.180.240/28234.167.180.241 to 234.167.180.254234.167.180.25514
81234.167.181.0/28234.167.181.1 to 234.167.181.14234.167.181.1514
82234.167.181.16/28234.167.181.17 to 234.167.181.30234.167.181.3114
83234.167.181.32/28234.167.181.33 to 234.167.181.46234.167.181.4714
84234.167.181.48/28234.167.181.49 to 234.167.181.62234.167.181.6314
85234.167.181.64/28234.167.181.65 to 234.167.181.78234.167.181.7914
86234.167.181.80/28234.167.181.81 to 234.167.181.94234.167.181.9514
87234.167.181.96/28234.167.181.97 to 234.167.181.110234.167.181.11114
88234.167.181.112/28234.167.181.113 to 234.167.181.126234.167.181.12714
89234.167.181.128/28234.167.181.129 to 234.167.181.142234.167.181.14314
90234.167.181.144/28234.167.181.145 to 234.167.181.158234.167.181.15914
91234.167.181.160/28234.167.181.161 to 234.167.181.174234.167.181.17514
92234.167.181.176/28234.167.181.177 to 234.167.181.190234.167.181.19114
93234.167.181.192/28234.167.181.193 to 234.167.181.206234.167.181.20714
94234.167.181.208/28234.167.181.209 to 234.167.181.222234.167.181.22314
95234.167.181.224/28234.167.181.225 to 234.167.181.238234.167.181.23914
96234.167.181.240/28234.167.181.241 to 234.167.181.254234.167.181.25514
97234.167.182.0/28234.167.182.1 to 234.167.182.14234.167.182.1514
98234.167.182.16/28234.167.182.17 to 234.167.182.30234.167.182.3114
99234.167.182.32/28234.167.182.33 to 234.167.182.46234.167.182.4714
100234.167.182.48/28234.167.182.49 to 234.167.182.62234.167.182.6314
101234.167.182.64/28234.167.182.65 to 234.167.182.78234.167.182.7914
102234.167.182.80/28234.167.182.81 to 234.167.182.94234.167.182.9514
103234.167.182.96/28234.167.182.97 to 234.167.182.110234.167.182.11114
104234.167.182.112/28234.167.182.113 to 234.167.182.126234.167.182.12714
105234.167.182.128/28234.167.182.129 to 234.167.182.142234.167.182.14314
106234.167.182.144/28234.167.182.145 to 234.167.182.158234.167.182.15914
107234.167.182.160/28234.167.182.161 to 234.167.182.174234.167.182.17514
108234.167.182.176/28234.167.182.177 to 234.167.182.190234.167.182.19114
109234.167.182.192/28234.167.182.193 to 234.167.182.206234.167.182.20714
110234.167.182.208/28234.167.182.209 to 234.167.182.222234.167.182.22314
111234.167.182.224/28234.167.182.225 to 234.167.182.238234.167.182.23914
112234.167.182.240/28234.167.182.241 to 234.167.182.254234.167.182.25514
113234.167.183.0/28234.167.183.1 to 234.167.183.14234.167.183.1514
114234.167.183.16/28234.167.183.17 to 234.167.183.30234.167.183.3114
115234.167.183.32/28234.167.183.33 to 234.167.183.46234.167.183.4714
116234.167.183.48/28234.167.183.49 to 234.167.183.62234.167.183.6314
117234.167.183.64/28234.167.183.65 to 234.167.183.78234.167.183.7914
118234.167.183.80/28234.167.183.81 to 234.167.183.94234.167.183.9514
119234.167.183.96/28234.167.183.97 to 234.167.183.110234.167.183.11114
120234.167.183.112/28234.167.183.113 to 234.167.183.126234.167.183.12714
121234.167.183.128/28234.167.183.129 to 234.167.183.142234.167.183.14314
122234.167.183.144/28234.167.183.145 to 234.167.183.158234.167.183.15914
123234.167.183.160/28234.167.183.161 to 234.167.183.174234.167.183.17514
124234.167.183.176/28234.167.183.177 to 234.167.183.190234.167.183.19114
125234.167.183.192/28234.167.183.193 to 234.167.183.206234.167.183.20714
126234.167.183.208/28234.167.183.209 to 234.167.183.222234.167.183.22314
127234.167.183.224/28234.167.183.225 to 234.167.183.238234.167.183.23914
128234.167.183.240/28234.167.183.241 to 234.167.183.254234.167.183.25514

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.