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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.

Network205.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
205.0.0.0
Broadcast address
205.255.255.255
First usable
205.0.0.1
Last usable
205.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Public public
Old class
C (default /24)
As numbers
Hex CD000000 · Integer 3439329280 to 3456106495
Reverse DNS zone
205.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11001101..00000000.00000000.00000000205.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network11001101..00000000.00000000.00000000205.0.0.0
Broadcast11001101..11111111.11111111.11111111205.255.255.255
Split into smaller subnets/19
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

205.0.0.0/8 makes 2,048 subnets of /19; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1205.0.0.0/19205.0.0.1 to 205.0.31.254205.0.31.2558,190
2205.0.32.0/19205.0.32.1 to 205.0.63.254205.0.63.2558,190
3205.0.64.0/19205.0.64.1 to 205.0.95.254205.0.95.2558,190
4205.0.96.0/19205.0.96.1 to 205.0.127.254205.0.127.2558,190
5205.0.128.0/19205.0.128.1 to 205.0.159.254205.0.159.2558,190
6205.0.160.0/19205.0.160.1 to 205.0.191.254205.0.191.2558,190
7205.0.192.0/19205.0.192.1 to 205.0.223.254205.0.223.2558,190
8205.0.224.0/19205.0.224.1 to 205.0.255.254205.0.255.2558,190
9205.1.0.0/19205.1.0.1 to 205.1.31.254205.1.31.2558,190
10205.1.32.0/19205.1.32.1 to 205.1.63.254205.1.63.2558,190
11205.1.64.0/19205.1.64.1 to 205.1.95.254205.1.95.2558,190
12205.1.96.0/19205.1.96.1 to 205.1.127.254205.1.127.2558,190
13205.1.128.0/19205.1.128.1 to 205.1.159.254205.1.159.2558,190
14205.1.160.0/19205.1.160.1 to 205.1.191.254205.1.191.2558,190
15205.1.192.0/19205.1.192.1 to 205.1.223.254205.1.223.2558,190
16205.1.224.0/19205.1.224.1 to 205.1.255.254205.1.255.2558,190
17205.2.0.0/19205.2.0.1 to 205.2.31.254205.2.31.2558,190
18205.2.32.0/19205.2.32.1 to 205.2.63.254205.2.63.2558,190
19205.2.64.0/19205.2.64.1 to 205.2.95.254205.2.95.2558,190
20205.2.96.0/19205.2.96.1 to 205.2.127.254205.2.127.2558,190
21205.2.128.0/19205.2.128.1 to 205.2.159.254205.2.159.2558,190
22205.2.160.0/19205.2.160.1 to 205.2.191.254205.2.191.2558,190
23205.2.192.0/19205.2.192.1 to 205.2.223.254205.2.223.2558,190
24205.2.224.0/19205.2.224.1 to 205.2.255.254205.2.255.2558,190
25205.3.0.0/19205.3.0.1 to 205.3.31.254205.3.31.2558,190
26205.3.32.0/19205.3.32.1 to 205.3.63.254205.3.63.2558,190
27205.3.64.0/19205.3.64.1 to 205.3.95.254205.3.95.2558,190
28205.3.96.0/19205.3.96.1 to 205.3.127.254205.3.127.2558,190
29205.3.128.0/19205.3.128.1 to 205.3.159.254205.3.159.2558,190
30205.3.160.0/19205.3.160.1 to 205.3.191.254205.3.191.2558,190
31205.3.192.0/19205.3.192.1 to 205.3.223.254205.3.223.2558,190
32205.3.224.0/19205.3.224.1 to 205.3.255.254205.3.255.2558,190
33205.4.0.0/19205.4.0.1 to 205.4.31.254205.4.31.2558,190
34205.4.32.0/19205.4.32.1 to 205.4.63.254205.4.63.2558,190
35205.4.64.0/19205.4.64.1 to 205.4.95.254205.4.95.2558,190
36205.4.96.0/19205.4.96.1 to 205.4.127.254205.4.127.2558,190
37205.4.128.0/19205.4.128.1 to 205.4.159.254205.4.159.2558,190
38205.4.160.0/19205.4.160.1 to 205.4.191.254205.4.191.2558,190
39205.4.192.0/19205.4.192.1 to 205.4.223.254205.4.223.2558,190
40205.4.224.0/19205.4.224.1 to 205.4.255.254205.4.255.2558,190
41205.5.0.0/19205.5.0.1 to 205.5.31.254205.5.31.2558,190
42205.5.32.0/19205.5.32.1 to 205.5.63.254205.5.63.2558,190
43205.5.64.0/19205.5.64.1 to 205.5.95.254205.5.95.2558,190
44205.5.96.0/19205.5.96.1 to 205.5.127.254205.5.127.2558,190
45205.5.128.0/19205.5.128.1 to 205.5.159.254205.5.159.2558,190
46205.5.160.0/19205.5.160.1 to 205.5.191.254205.5.191.2558,190
47205.5.192.0/19205.5.192.1 to 205.5.223.254205.5.223.2558,190
48205.5.224.0/19205.5.224.1 to 205.5.255.254205.5.255.2558,190
49205.6.0.0/19205.6.0.1 to 205.6.31.254205.6.31.2558,190
50205.6.32.0/19205.6.32.1 to 205.6.63.254205.6.63.2558,190
51205.6.64.0/19205.6.64.1 to 205.6.95.254205.6.95.2558,190
52205.6.96.0/19205.6.96.1 to 205.6.127.254205.6.127.2558,190
53205.6.128.0/19205.6.128.1 to 205.6.159.254205.6.159.2558,190
54205.6.160.0/19205.6.160.1 to 205.6.191.254205.6.191.2558,190
55205.6.192.0/19205.6.192.1 to 205.6.223.254205.6.223.2558,190
56205.6.224.0/19205.6.224.1 to 205.6.255.254205.6.255.2558,190
57205.7.0.0/19205.7.0.1 to 205.7.31.254205.7.31.2558,190
58205.7.32.0/19205.7.32.1 to 205.7.63.254205.7.63.2558,190
59205.7.64.0/19205.7.64.1 to 205.7.95.254205.7.95.2558,190
60205.7.96.0/19205.7.96.1 to 205.7.127.254205.7.127.2558,190
61205.7.128.0/19205.7.128.1 to 205.7.159.254205.7.159.2558,190
62205.7.160.0/19205.7.160.1 to 205.7.191.254205.7.191.2558,190
63205.7.192.0/19205.7.192.1 to 205.7.223.254205.7.223.2558,190
64205.7.224.0/19205.7.224.1 to 205.7.255.254205.7.255.2558,190
65205.8.0.0/19205.8.0.1 to 205.8.31.254205.8.31.2558,190
66205.8.32.0/19205.8.32.1 to 205.8.63.254205.8.63.2558,190
67205.8.64.0/19205.8.64.1 to 205.8.95.254205.8.95.2558,190
68205.8.96.0/19205.8.96.1 to 205.8.127.254205.8.127.2558,190
69205.8.128.0/19205.8.128.1 to 205.8.159.254205.8.159.2558,190
70205.8.160.0/19205.8.160.1 to 205.8.191.254205.8.191.2558,190
71205.8.192.0/19205.8.192.1 to 205.8.223.254205.8.223.2558,190
72205.8.224.0/19205.8.224.1 to 205.8.255.254205.8.255.2558,190
73205.9.0.0/19205.9.0.1 to 205.9.31.254205.9.31.2558,190
74205.9.32.0/19205.9.32.1 to 205.9.63.254205.9.63.2558,190
75205.9.64.0/19205.9.64.1 to 205.9.95.254205.9.95.2558,190
76205.9.96.0/19205.9.96.1 to 205.9.127.254205.9.127.2558,190
77205.9.128.0/19205.9.128.1 to 205.9.159.254205.9.159.2558,190
78205.9.160.0/19205.9.160.1 to 205.9.191.254205.9.191.2558,190
79205.9.192.0/19205.9.192.1 to 205.9.223.254205.9.223.2558,190
80205.9.224.0/19205.9.224.1 to 205.9.255.254205.9.255.2558,190
81205.10.0.0/19205.10.0.1 to 205.10.31.254205.10.31.2558,190
82205.10.32.0/19205.10.32.1 to 205.10.63.254205.10.63.2558,190
83205.10.64.0/19205.10.64.1 to 205.10.95.254205.10.95.2558,190
84205.10.96.0/19205.10.96.1 to 205.10.127.254205.10.127.2558,190
85205.10.128.0/19205.10.128.1 to 205.10.159.254205.10.159.2558,190
86205.10.160.0/19205.10.160.1 to 205.10.191.254205.10.191.2558,190
87205.10.192.0/19205.10.192.1 to 205.10.223.254205.10.223.2558,190
88205.10.224.0/19205.10.224.1 to 205.10.255.254205.10.255.2558,190
89205.11.0.0/19205.11.0.1 to 205.11.31.254205.11.31.2558,190
90205.11.32.0/19205.11.32.1 to 205.11.63.254205.11.63.2558,190
91205.11.64.0/19205.11.64.1 to 205.11.95.254205.11.95.2558,190
92205.11.96.0/19205.11.96.1 to 205.11.127.254205.11.127.2558,190
93205.11.128.0/19205.11.128.1 to 205.11.159.254205.11.159.2558,190
94205.11.160.0/19205.11.160.1 to 205.11.191.254205.11.191.2558,190
95205.11.192.0/19205.11.192.1 to 205.11.223.254205.11.223.2558,190
96205.11.224.0/19205.11.224.1 to 205.11.255.254205.11.255.2558,190
97205.12.0.0/19205.12.0.1 to 205.12.31.254205.12.31.2558,190
98205.12.32.0/19205.12.32.1 to 205.12.63.254205.12.63.2558,190
99205.12.64.0/19205.12.64.1 to 205.12.95.254205.12.95.2558,190
100205.12.96.0/19205.12.96.1 to 205.12.127.254205.12.127.2558,190
101205.12.128.0/19205.12.128.1 to 205.12.159.254205.12.159.2558,190
102205.12.160.0/19205.12.160.1 to 205.12.191.254205.12.191.2558,190
103205.12.192.0/19205.12.192.1 to 205.12.223.254205.12.223.2558,190
104205.12.224.0/19205.12.224.1 to 205.12.255.254205.12.255.2558,190
105205.13.0.0/19205.13.0.1 to 205.13.31.254205.13.31.2558,190
106205.13.32.0/19205.13.32.1 to 205.13.63.254205.13.63.2558,190
107205.13.64.0/19205.13.64.1 to 205.13.95.254205.13.95.2558,190
108205.13.96.0/19205.13.96.1 to 205.13.127.254205.13.127.2558,190
109205.13.128.0/19205.13.128.1 to 205.13.159.254205.13.159.2558,190
110205.13.160.0/19205.13.160.1 to 205.13.191.254205.13.191.2558,190
111205.13.192.0/19205.13.192.1 to 205.13.223.254205.13.223.2558,190
112205.13.224.0/19205.13.224.1 to 205.13.255.254205.13.255.2558,190
113205.14.0.0/19205.14.0.1 to 205.14.31.254205.14.31.2558,190
114205.14.32.0/19205.14.32.1 to 205.14.63.254205.14.63.2558,190
115205.14.64.0/19205.14.64.1 to 205.14.95.254205.14.95.2558,190
116205.14.96.0/19205.14.96.1 to 205.14.127.254205.14.127.2558,190
117205.14.128.0/19205.14.128.1 to 205.14.159.254205.14.159.2558,190
118205.14.160.0/19205.14.160.1 to 205.14.191.254205.14.191.2558,190
119205.14.192.0/19205.14.192.1 to 205.14.223.254205.14.223.2558,190
120205.14.224.0/19205.14.224.1 to 205.14.255.254205.14.255.2558,190
121205.15.0.0/19205.15.0.1 to 205.15.31.254205.15.31.2558,190
122205.15.32.0/19205.15.32.1 to 205.15.63.254205.15.63.2558,190
123205.15.64.0/19205.15.64.1 to 205.15.95.254205.15.95.2558,190
124205.15.96.0/19205.15.96.1 to 205.15.127.254205.15.127.2558,190
125205.15.128.0/19205.15.128.1 to 205.15.159.254205.15.159.2558,190
126205.15.160.0/19205.15.160.1 to 205.15.191.254205.15.191.2558,190
127205.15.192.0/19205.15.192.1 to 205.15.223.254205.15.223.2558,190
128205.15.224.0/19205.15.224.1 to 205.15.255.254205.15.255.2558,190
129205.16.0.0/19205.16.0.1 to 205.16.31.254205.16.31.2558,190
130205.16.32.0/19205.16.32.1 to 205.16.63.254205.16.63.2558,190
131205.16.64.0/19205.16.64.1 to 205.16.95.254205.16.95.2558,190
132205.16.96.0/19205.16.96.1 to 205.16.127.254205.16.127.2558,190
133205.16.128.0/19205.16.128.1 to 205.16.159.254205.16.159.2558,190
134205.16.160.0/19205.16.160.1 to 205.16.191.254205.16.191.2558,190
135205.16.192.0/19205.16.192.1 to 205.16.223.254205.16.223.2558,190
136205.16.224.0/19205.16.224.1 to 205.16.255.254205.16.255.2558,190
137205.17.0.0/19205.17.0.1 to 205.17.31.254205.17.31.2558,190
138205.17.32.0/19205.17.32.1 to 205.17.63.254205.17.63.2558,190
139205.17.64.0/19205.17.64.1 to 205.17.95.254205.17.95.2558,190
140205.17.96.0/19205.17.96.1 to 205.17.127.254205.17.127.2558,190
141205.17.128.0/19205.17.128.1 to 205.17.159.254205.17.159.2558,190
142205.17.160.0/19205.17.160.1 to 205.17.191.254205.17.191.2558,190
143205.17.192.0/19205.17.192.1 to 205.17.223.254205.17.223.2558,190
144205.17.224.0/19205.17.224.1 to 205.17.255.254205.17.255.2558,190
145205.18.0.0/19205.18.0.1 to 205.18.31.254205.18.31.2558,190
146205.18.32.0/19205.18.32.1 to 205.18.63.254205.18.63.2558,190
147205.18.64.0/19205.18.64.1 to 205.18.95.254205.18.95.2558,190
148205.18.96.0/19205.18.96.1 to 205.18.127.254205.18.127.2558,190
149205.18.128.0/19205.18.128.1 to 205.18.159.254205.18.159.2558,190
150205.18.160.0/19205.18.160.1 to 205.18.191.254205.18.191.2558,190
151205.18.192.0/19205.18.192.1 to 205.18.223.254205.18.223.2558,190
152205.18.224.0/19205.18.224.1 to 205.18.255.254205.18.255.2558,190
153205.19.0.0/19205.19.0.1 to 205.19.31.254205.19.31.2558,190
154205.19.32.0/19205.19.32.1 to 205.19.63.254205.19.63.2558,190
155205.19.64.0/19205.19.64.1 to 205.19.95.254205.19.95.2558,190
156205.19.96.0/19205.19.96.1 to 205.19.127.254205.19.127.2558,190
157205.19.128.0/19205.19.128.1 to 205.19.159.254205.19.159.2558,190
158205.19.160.0/19205.19.160.1 to 205.19.191.254205.19.191.2558,190
159205.19.192.0/19205.19.192.1 to 205.19.223.254205.19.223.2558,190
160205.19.224.0/19205.19.224.1 to 205.19.255.254205.19.255.2558,190
161205.20.0.0/19205.20.0.1 to 205.20.31.254205.20.31.2558,190
162205.20.32.0/19205.20.32.1 to 205.20.63.254205.20.63.2558,190
163205.20.64.0/19205.20.64.1 to 205.20.95.254205.20.95.2558,190
164205.20.96.0/19205.20.96.1 to 205.20.127.254205.20.127.2558,190
165205.20.128.0/19205.20.128.1 to 205.20.159.254205.20.159.2558,190
166205.20.160.0/19205.20.160.1 to 205.20.191.254205.20.191.2558,190
167205.20.192.0/19205.20.192.1 to 205.20.223.254205.20.223.2558,190
168205.20.224.0/19205.20.224.1 to 205.20.255.254205.20.255.2558,190
169205.21.0.0/19205.21.0.1 to 205.21.31.254205.21.31.2558,190
170205.21.32.0/19205.21.32.1 to 205.21.63.254205.21.63.2558,190
171205.21.64.0/19205.21.64.1 to 205.21.95.254205.21.95.2558,190
172205.21.96.0/19205.21.96.1 to 205.21.127.254205.21.127.2558,190
173205.21.128.0/19205.21.128.1 to 205.21.159.254205.21.159.2558,190
174205.21.160.0/19205.21.160.1 to 205.21.191.254205.21.191.2558,190
175205.21.192.0/19205.21.192.1 to 205.21.223.254205.21.223.2558,190
176205.21.224.0/19205.21.224.1 to 205.21.255.254205.21.255.2558,190
177205.22.0.0/19205.22.0.1 to 205.22.31.254205.22.31.2558,190
178205.22.32.0/19205.22.32.1 to 205.22.63.254205.22.63.2558,190
179205.22.64.0/19205.22.64.1 to 205.22.95.254205.22.95.2558,190
180205.22.96.0/19205.22.96.1 to 205.22.127.254205.22.127.2558,190
181205.22.128.0/19205.22.128.1 to 205.22.159.254205.22.159.2558,190
182205.22.160.0/19205.22.160.1 to 205.22.191.254205.22.191.2558,190
183205.22.192.0/19205.22.192.1 to 205.22.223.254205.22.223.2558,190
184205.22.224.0/19205.22.224.1 to 205.22.255.254205.22.255.2558,190
185205.23.0.0/19205.23.0.1 to 205.23.31.254205.23.31.2558,190
186205.23.32.0/19205.23.32.1 to 205.23.63.254205.23.63.2558,190
187205.23.64.0/19205.23.64.1 to 205.23.95.254205.23.95.2558,190
188205.23.96.0/19205.23.96.1 to 205.23.127.254205.23.127.2558,190
189205.23.128.0/19205.23.128.1 to 205.23.159.254205.23.159.2558,190
190205.23.160.0/19205.23.160.1 to 205.23.191.254205.23.191.2558,190
191205.23.192.0/19205.23.192.1 to 205.23.223.254205.23.223.2558,190
192205.23.224.0/19205.23.224.1 to 205.23.255.254205.23.255.2558,190
193205.24.0.0/19205.24.0.1 to 205.24.31.254205.24.31.2558,190
194205.24.32.0/19205.24.32.1 to 205.24.63.254205.24.63.2558,190
195205.24.64.0/19205.24.64.1 to 205.24.95.254205.24.95.2558,190
196205.24.96.0/19205.24.96.1 to 205.24.127.254205.24.127.2558,190
197205.24.128.0/19205.24.128.1 to 205.24.159.254205.24.159.2558,190
198205.24.160.0/19205.24.160.1 to 205.24.191.254205.24.191.2558,190
199205.24.192.0/19205.24.192.1 to 205.24.223.254205.24.223.2558,190
200205.24.224.0/19205.24.224.1 to 205.24.255.254205.24.255.2558,190
201205.25.0.0/19205.25.0.1 to 205.25.31.254205.25.31.2558,190
202205.25.32.0/19205.25.32.1 to 205.25.63.254205.25.63.2558,190
203205.25.64.0/19205.25.64.1 to 205.25.95.254205.25.95.2558,190
204205.25.96.0/19205.25.96.1 to 205.25.127.254205.25.127.2558,190
205205.25.128.0/19205.25.128.1 to 205.25.159.254205.25.159.2558,190
206205.25.160.0/19205.25.160.1 to 205.25.191.254205.25.191.2558,190
207205.25.192.0/19205.25.192.1 to 205.25.223.254205.25.223.2558,190
208205.25.224.0/19205.25.224.1 to 205.25.255.254205.25.255.2558,190
209205.26.0.0/19205.26.0.1 to 205.26.31.254205.26.31.2558,190
210205.26.32.0/19205.26.32.1 to 205.26.63.254205.26.63.2558,190
211205.26.64.0/19205.26.64.1 to 205.26.95.254205.26.95.2558,190
212205.26.96.0/19205.26.96.1 to 205.26.127.254205.26.127.2558,190
213205.26.128.0/19205.26.128.1 to 205.26.159.254205.26.159.2558,190
214205.26.160.0/19205.26.160.1 to 205.26.191.254205.26.191.2558,190
215205.26.192.0/19205.26.192.1 to 205.26.223.254205.26.223.2558,190
216205.26.224.0/19205.26.224.1 to 205.26.255.254205.26.255.2558,190
217205.27.0.0/19205.27.0.1 to 205.27.31.254205.27.31.2558,190
218205.27.32.0/19205.27.32.1 to 205.27.63.254205.27.63.2558,190
219205.27.64.0/19205.27.64.1 to 205.27.95.254205.27.95.2558,190
220205.27.96.0/19205.27.96.1 to 205.27.127.254205.27.127.2558,190
221205.27.128.0/19205.27.128.1 to 205.27.159.254205.27.159.2558,190
222205.27.160.0/19205.27.160.1 to 205.27.191.254205.27.191.2558,190
223205.27.192.0/19205.27.192.1 to 205.27.223.254205.27.223.2558,190
224205.27.224.0/19205.27.224.1 to 205.27.255.254205.27.255.2558,190
225205.28.0.0/19205.28.0.1 to 205.28.31.254205.28.31.2558,190
226205.28.32.0/19205.28.32.1 to 205.28.63.254205.28.63.2558,190
227205.28.64.0/19205.28.64.1 to 205.28.95.254205.28.95.2558,190
228205.28.96.0/19205.28.96.1 to 205.28.127.254205.28.127.2558,190
229205.28.128.0/19205.28.128.1 to 205.28.159.254205.28.159.2558,190
230205.28.160.0/19205.28.160.1 to 205.28.191.254205.28.191.2558,190
231205.28.192.0/19205.28.192.1 to 205.28.223.254205.28.223.2558,190
232205.28.224.0/19205.28.224.1 to 205.28.255.254205.28.255.2558,190
233205.29.0.0/19205.29.0.1 to 205.29.31.254205.29.31.2558,190
234205.29.32.0/19205.29.32.1 to 205.29.63.254205.29.63.2558,190
235205.29.64.0/19205.29.64.1 to 205.29.95.254205.29.95.2558,190
236205.29.96.0/19205.29.96.1 to 205.29.127.254205.29.127.2558,190
237205.29.128.0/19205.29.128.1 to 205.29.159.254205.29.159.2558,190
238205.29.160.0/19205.29.160.1 to 205.29.191.254205.29.191.2558,190
239205.29.192.0/19205.29.192.1 to 205.29.223.254205.29.223.2558,190
240205.29.224.0/19205.29.224.1 to 205.29.255.254205.29.255.2558,190
241205.30.0.0/19205.30.0.1 to 205.30.31.254205.30.31.2558,190
242205.30.32.0/19205.30.32.1 to 205.30.63.254205.30.63.2558,190
243205.30.64.0/19205.30.64.1 to 205.30.95.254205.30.95.2558,190
244205.30.96.0/19205.30.96.1 to 205.30.127.254205.30.127.2558,190
245205.30.128.0/19205.30.128.1 to 205.30.159.254205.30.159.2558,190
246205.30.160.0/19205.30.160.1 to 205.30.191.254205.30.191.2558,190
247205.30.192.0/19205.30.192.1 to 205.30.223.254205.30.223.2558,190
248205.30.224.0/19205.30.224.1 to 205.30.255.254205.30.255.2558,190
249205.31.0.0/19205.31.0.1 to 205.31.31.254205.31.31.2558,190
250205.31.32.0/19205.31.32.1 to 205.31.63.254205.31.63.2558,190
251205.31.64.0/19205.31.64.1 to 205.31.95.254205.31.95.2558,190
252205.31.96.0/19205.31.96.1 to 205.31.127.254205.31.127.2558,190
253205.31.128.0/19205.31.128.1 to 205.31.159.254205.31.159.2558,190
254205.31.160.0/19205.31.160.1 to 205.31.191.254205.31.191.2558,190
255205.31.192.0/19205.31.192.1 to 205.31.223.254205.31.223.2558,190
256205.31.224.0/19205.31.224.1 to 205.31.255.254205.31.255.2558,190

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.