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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.

Network191.72.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
191.72.0.0
Broadcast address
191.72.127.255
First usable
191.72.0.1
Last usable
191.72.127.254
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
B (default /16)
As numbers
Hex BF480000 · Integer 3209166848 to 3209199615
Reverse DNS zones
0.72.191.in-addr.arpa
1.72.191.in-addr.arpa
2.72.191.in-addr.arpa
3.72.191.in-addr.arpa
4.72.191.in-addr.arpa
5.72.191.in-addr.arpa
6.72.191.in-addr.arpa
7.72.191.in-addr.arpa
8.72.191.in-addr.arpa
9.72.191.in-addr.arpa
10.72.191.in-addr.arpa
11.72.191.in-addr.arpa
12.72.191.in-addr.arpa
13.72.191.in-addr.arpa
14.72.191.in-addr.arpa
15.72.191.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
Address10111111.01001000.00000000.00000000191.72.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network10111111.01001000.00000000.00000000191.72.0.0
Broadcast10111111.01001000.01111111.11111111191.72.127.255
Split into smaller subnets/27
/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)

191.72.0.0/17 makes 1,024 subnets of /27; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1191.72.0.0/27191.72.0.1 to 191.72.0.30191.72.0.3130
2191.72.0.32/27191.72.0.33 to 191.72.0.62191.72.0.6330
3191.72.0.64/27191.72.0.65 to 191.72.0.94191.72.0.9530
4191.72.0.96/27191.72.0.97 to 191.72.0.126191.72.0.12730
5191.72.0.128/27191.72.0.129 to 191.72.0.158191.72.0.15930
6191.72.0.160/27191.72.0.161 to 191.72.0.190191.72.0.19130
7191.72.0.192/27191.72.0.193 to 191.72.0.222191.72.0.22330
8191.72.0.224/27191.72.0.225 to 191.72.0.254191.72.0.25530
9191.72.1.0/27191.72.1.1 to 191.72.1.30191.72.1.3130
10191.72.1.32/27191.72.1.33 to 191.72.1.62191.72.1.6330
11191.72.1.64/27191.72.1.65 to 191.72.1.94191.72.1.9530
12191.72.1.96/27191.72.1.97 to 191.72.1.126191.72.1.12730
13191.72.1.128/27191.72.1.129 to 191.72.1.158191.72.1.15930
14191.72.1.160/27191.72.1.161 to 191.72.1.190191.72.1.19130
15191.72.1.192/27191.72.1.193 to 191.72.1.222191.72.1.22330
16191.72.1.224/27191.72.1.225 to 191.72.1.254191.72.1.25530
17191.72.2.0/27191.72.2.1 to 191.72.2.30191.72.2.3130
18191.72.2.32/27191.72.2.33 to 191.72.2.62191.72.2.6330
19191.72.2.64/27191.72.2.65 to 191.72.2.94191.72.2.9530
20191.72.2.96/27191.72.2.97 to 191.72.2.126191.72.2.12730
21191.72.2.128/27191.72.2.129 to 191.72.2.158191.72.2.15930
22191.72.2.160/27191.72.2.161 to 191.72.2.190191.72.2.19130
23191.72.2.192/27191.72.2.193 to 191.72.2.222191.72.2.22330
24191.72.2.224/27191.72.2.225 to 191.72.2.254191.72.2.25530
25191.72.3.0/27191.72.3.1 to 191.72.3.30191.72.3.3130
26191.72.3.32/27191.72.3.33 to 191.72.3.62191.72.3.6330
27191.72.3.64/27191.72.3.65 to 191.72.3.94191.72.3.9530
28191.72.3.96/27191.72.3.97 to 191.72.3.126191.72.3.12730
29191.72.3.128/27191.72.3.129 to 191.72.3.158191.72.3.15930
30191.72.3.160/27191.72.3.161 to 191.72.3.190191.72.3.19130
31191.72.3.192/27191.72.3.193 to 191.72.3.222191.72.3.22330
32191.72.3.224/27191.72.3.225 to 191.72.3.254191.72.3.25530
33191.72.4.0/27191.72.4.1 to 191.72.4.30191.72.4.3130
34191.72.4.32/27191.72.4.33 to 191.72.4.62191.72.4.6330
35191.72.4.64/27191.72.4.65 to 191.72.4.94191.72.4.9530
36191.72.4.96/27191.72.4.97 to 191.72.4.126191.72.4.12730
37191.72.4.128/27191.72.4.129 to 191.72.4.158191.72.4.15930
38191.72.4.160/27191.72.4.161 to 191.72.4.190191.72.4.19130
39191.72.4.192/27191.72.4.193 to 191.72.4.222191.72.4.22330
40191.72.4.224/27191.72.4.225 to 191.72.4.254191.72.4.25530
41191.72.5.0/27191.72.5.1 to 191.72.5.30191.72.5.3130
42191.72.5.32/27191.72.5.33 to 191.72.5.62191.72.5.6330
43191.72.5.64/27191.72.5.65 to 191.72.5.94191.72.5.9530
44191.72.5.96/27191.72.5.97 to 191.72.5.126191.72.5.12730
45191.72.5.128/27191.72.5.129 to 191.72.5.158191.72.5.15930
46191.72.5.160/27191.72.5.161 to 191.72.5.190191.72.5.19130
47191.72.5.192/27191.72.5.193 to 191.72.5.222191.72.5.22330
48191.72.5.224/27191.72.5.225 to 191.72.5.254191.72.5.25530
49191.72.6.0/27191.72.6.1 to 191.72.6.30191.72.6.3130
50191.72.6.32/27191.72.6.33 to 191.72.6.62191.72.6.6330
51191.72.6.64/27191.72.6.65 to 191.72.6.94191.72.6.9530
52191.72.6.96/27191.72.6.97 to 191.72.6.126191.72.6.12730
53191.72.6.128/27191.72.6.129 to 191.72.6.158191.72.6.15930
54191.72.6.160/27191.72.6.161 to 191.72.6.190191.72.6.19130
55191.72.6.192/27191.72.6.193 to 191.72.6.222191.72.6.22330
56191.72.6.224/27191.72.6.225 to 191.72.6.254191.72.6.25530
57191.72.7.0/27191.72.7.1 to 191.72.7.30191.72.7.3130
58191.72.7.32/27191.72.7.33 to 191.72.7.62191.72.7.6330
59191.72.7.64/27191.72.7.65 to 191.72.7.94191.72.7.9530
60191.72.7.96/27191.72.7.97 to 191.72.7.126191.72.7.12730
61191.72.7.128/27191.72.7.129 to 191.72.7.158191.72.7.15930
62191.72.7.160/27191.72.7.161 to 191.72.7.190191.72.7.19130
63191.72.7.192/27191.72.7.193 to 191.72.7.222191.72.7.22330
64191.72.7.224/27191.72.7.225 to 191.72.7.254191.72.7.25530
65191.72.8.0/27191.72.8.1 to 191.72.8.30191.72.8.3130
66191.72.8.32/27191.72.8.33 to 191.72.8.62191.72.8.6330
67191.72.8.64/27191.72.8.65 to 191.72.8.94191.72.8.9530
68191.72.8.96/27191.72.8.97 to 191.72.8.126191.72.8.12730
69191.72.8.128/27191.72.8.129 to 191.72.8.158191.72.8.15930
70191.72.8.160/27191.72.8.161 to 191.72.8.190191.72.8.19130
71191.72.8.192/27191.72.8.193 to 191.72.8.222191.72.8.22330
72191.72.8.224/27191.72.8.225 to 191.72.8.254191.72.8.25530
73191.72.9.0/27191.72.9.1 to 191.72.9.30191.72.9.3130
74191.72.9.32/27191.72.9.33 to 191.72.9.62191.72.9.6330
75191.72.9.64/27191.72.9.65 to 191.72.9.94191.72.9.9530
76191.72.9.96/27191.72.9.97 to 191.72.9.126191.72.9.12730
77191.72.9.128/27191.72.9.129 to 191.72.9.158191.72.9.15930
78191.72.9.160/27191.72.9.161 to 191.72.9.190191.72.9.19130
79191.72.9.192/27191.72.9.193 to 191.72.9.222191.72.9.22330
80191.72.9.224/27191.72.9.225 to 191.72.9.254191.72.9.25530
81191.72.10.0/27191.72.10.1 to 191.72.10.30191.72.10.3130
82191.72.10.32/27191.72.10.33 to 191.72.10.62191.72.10.6330
83191.72.10.64/27191.72.10.65 to 191.72.10.94191.72.10.9530
84191.72.10.96/27191.72.10.97 to 191.72.10.126191.72.10.12730
85191.72.10.128/27191.72.10.129 to 191.72.10.158191.72.10.15930
86191.72.10.160/27191.72.10.161 to 191.72.10.190191.72.10.19130
87191.72.10.192/27191.72.10.193 to 191.72.10.222191.72.10.22330
88191.72.10.224/27191.72.10.225 to 191.72.10.254191.72.10.25530
89191.72.11.0/27191.72.11.1 to 191.72.11.30191.72.11.3130
90191.72.11.32/27191.72.11.33 to 191.72.11.62191.72.11.6330
91191.72.11.64/27191.72.11.65 to 191.72.11.94191.72.11.9530
92191.72.11.96/27191.72.11.97 to 191.72.11.126191.72.11.12730
93191.72.11.128/27191.72.11.129 to 191.72.11.158191.72.11.15930
94191.72.11.160/27191.72.11.161 to 191.72.11.190191.72.11.19130
95191.72.11.192/27191.72.11.193 to 191.72.11.222191.72.11.22330
96191.72.11.224/27191.72.11.225 to 191.72.11.254191.72.11.25530
97191.72.12.0/27191.72.12.1 to 191.72.12.30191.72.12.3130
98191.72.12.32/27191.72.12.33 to 191.72.12.62191.72.12.6330
99191.72.12.64/27191.72.12.65 to 191.72.12.94191.72.12.9530
100191.72.12.96/27191.72.12.97 to 191.72.12.126191.72.12.12730
101191.72.12.128/27191.72.12.129 to 191.72.12.158191.72.12.15930
102191.72.12.160/27191.72.12.161 to 191.72.12.190191.72.12.19130
103191.72.12.192/27191.72.12.193 to 191.72.12.222191.72.12.22330
104191.72.12.224/27191.72.12.225 to 191.72.12.254191.72.12.25530
105191.72.13.0/27191.72.13.1 to 191.72.13.30191.72.13.3130
106191.72.13.32/27191.72.13.33 to 191.72.13.62191.72.13.6330
107191.72.13.64/27191.72.13.65 to 191.72.13.94191.72.13.9530
108191.72.13.96/27191.72.13.97 to 191.72.13.126191.72.13.12730
109191.72.13.128/27191.72.13.129 to 191.72.13.158191.72.13.15930
110191.72.13.160/27191.72.13.161 to 191.72.13.190191.72.13.19130
111191.72.13.192/27191.72.13.193 to 191.72.13.222191.72.13.22330
112191.72.13.224/27191.72.13.225 to 191.72.13.254191.72.13.25530
113191.72.14.0/27191.72.14.1 to 191.72.14.30191.72.14.3130
114191.72.14.32/27191.72.14.33 to 191.72.14.62191.72.14.6330
115191.72.14.64/27191.72.14.65 to 191.72.14.94191.72.14.9530
116191.72.14.96/27191.72.14.97 to 191.72.14.126191.72.14.12730
117191.72.14.128/27191.72.14.129 to 191.72.14.158191.72.14.15930
118191.72.14.160/27191.72.14.161 to 191.72.14.190191.72.14.19130
119191.72.14.192/27191.72.14.193 to 191.72.14.222191.72.14.22330
120191.72.14.224/27191.72.14.225 to 191.72.14.254191.72.14.25530
121191.72.15.0/27191.72.15.1 to 191.72.15.30191.72.15.3130
122191.72.15.32/27191.72.15.33 to 191.72.15.62191.72.15.6330
123191.72.15.64/27191.72.15.65 to 191.72.15.94191.72.15.9530
124191.72.15.96/27191.72.15.97 to 191.72.15.126191.72.15.12730
125191.72.15.128/27191.72.15.129 to 191.72.15.158191.72.15.15930
126191.72.15.160/27191.72.15.161 to 191.72.15.190191.72.15.19130
127191.72.15.192/27191.72.15.193 to 191.72.15.222191.72.15.22330
128191.72.15.224/27191.72.15.225 to 191.72.15.254191.72.15.25530
129191.72.16.0/27191.72.16.1 to 191.72.16.30191.72.16.3130
130191.72.16.32/27191.72.16.33 to 191.72.16.62191.72.16.6330
131191.72.16.64/27191.72.16.65 to 191.72.16.94191.72.16.9530
132191.72.16.96/27191.72.16.97 to 191.72.16.126191.72.16.12730
133191.72.16.128/27191.72.16.129 to 191.72.16.158191.72.16.15930
134191.72.16.160/27191.72.16.161 to 191.72.16.190191.72.16.19130
135191.72.16.192/27191.72.16.193 to 191.72.16.222191.72.16.22330
136191.72.16.224/27191.72.16.225 to 191.72.16.254191.72.16.25530
137191.72.17.0/27191.72.17.1 to 191.72.17.30191.72.17.3130
138191.72.17.32/27191.72.17.33 to 191.72.17.62191.72.17.6330
139191.72.17.64/27191.72.17.65 to 191.72.17.94191.72.17.9530
140191.72.17.96/27191.72.17.97 to 191.72.17.126191.72.17.12730
141191.72.17.128/27191.72.17.129 to 191.72.17.158191.72.17.15930
142191.72.17.160/27191.72.17.161 to 191.72.17.190191.72.17.19130
143191.72.17.192/27191.72.17.193 to 191.72.17.222191.72.17.22330
144191.72.17.224/27191.72.17.225 to 191.72.17.254191.72.17.25530
145191.72.18.0/27191.72.18.1 to 191.72.18.30191.72.18.3130
146191.72.18.32/27191.72.18.33 to 191.72.18.62191.72.18.6330
147191.72.18.64/27191.72.18.65 to 191.72.18.94191.72.18.9530
148191.72.18.96/27191.72.18.97 to 191.72.18.126191.72.18.12730
149191.72.18.128/27191.72.18.129 to 191.72.18.158191.72.18.15930
150191.72.18.160/27191.72.18.161 to 191.72.18.190191.72.18.19130
151191.72.18.192/27191.72.18.193 to 191.72.18.222191.72.18.22330
152191.72.18.224/27191.72.18.225 to 191.72.18.254191.72.18.25530
153191.72.19.0/27191.72.19.1 to 191.72.19.30191.72.19.3130
154191.72.19.32/27191.72.19.33 to 191.72.19.62191.72.19.6330
155191.72.19.64/27191.72.19.65 to 191.72.19.94191.72.19.9530
156191.72.19.96/27191.72.19.97 to 191.72.19.126191.72.19.12730
157191.72.19.128/27191.72.19.129 to 191.72.19.158191.72.19.15930
158191.72.19.160/27191.72.19.161 to 191.72.19.190191.72.19.19130
159191.72.19.192/27191.72.19.193 to 191.72.19.222191.72.19.22330
160191.72.19.224/27191.72.19.225 to 191.72.19.254191.72.19.25530
161191.72.20.0/27191.72.20.1 to 191.72.20.30191.72.20.3130
162191.72.20.32/27191.72.20.33 to 191.72.20.62191.72.20.6330
163191.72.20.64/27191.72.20.65 to 191.72.20.94191.72.20.9530
164191.72.20.96/27191.72.20.97 to 191.72.20.126191.72.20.12730
165191.72.20.128/27191.72.20.129 to 191.72.20.158191.72.20.15930
166191.72.20.160/27191.72.20.161 to 191.72.20.190191.72.20.19130
167191.72.20.192/27191.72.20.193 to 191.72.20.222191.72.20.22330
168191.72.20.224/27191.72.20.225 to 191.72.20.254191.72.20.25530
169191.72.21.0/27191.72.21.1 to 191.72.21.30191.72.21.3130
170191.72.21.32/27191.72.21.33 to 191.72.21.62191.72.21.6330
171191.72.21.64/27191.72.21.65 to 191.72.21.94191.72.21.9530
172191.72.21.96/27191.72.21.97 to 191.72.21.126191.72.21.12730
173191.72.21.128/27191.72.21.129 to 191.72.21.158191.72.21.15930
174191.72.21.160/27191.72.21.161 to 191.72.21.190191.72.21.19130
175191.72.21.192/27191.72.21.193 to 191.72.21.222191.72.21.22330
176191.72.21.224/27191.72.21.225 to 191.72.21.254191.72.21.25530
177191.72.22.0/27191.72.22.1 to 191.72.22.30191.72.22.3130
178191.72.22.32/27191.72.22.33 to 191.72.22.62191.72.22.6330
179191.72.22.64/27191.72.22.65 to 191.72.22.94191.72.22.9530
180191.72.22.96/27191.72.22.97 to 191.72.22.126191.72.22.12730
181191.72.22.128/27191.72.22.129 to 191.72.22.158191.72.22.15930
182191.72.22.160/27191.72.22.161 to 191.72.22.190191.72.22.19130
183191.72.22.192/27191.72.22.193 to 191.72.22.222191.72.22.22330
184191.72.22.224/27191.72.22.225 to 191.72.22.254191.72.22.25530
185191.72.23.0/27191.72.23.1 to 191.72.23.30191.72.23.3130
186191.72.23.32/27191.72.23.33 to 191.72.23.62191.72.23.6330
187191.72.23.64/27191.72.23.65 to 191.72.23.94191.72.23.9530
188191.72.23.96/27191.72.23.97 to 191.72.23.126191.72.23.12730
189191.72.23.128/27191.72.23.129 to 191.72.23.158191.72.23.15930
190191.72.23.160/27191.72.23.161 to 191.72.23.190191.72.23.19130
191191.72.23.192/27191.72.23.193 to 191.72.23.222191.72.23.22330
192191.72.23.224/27191.72.23.225 to 191.72.23.254191.72.23.25530
193191.72.24.0/27191.72.24.1 to 191.72.24.30191.72.24.3130
194191.72.24.32/27191.72.24.33 to 191.72.24.62191.72.24.6330
195191.72.24.64/27191.72.24.65 to 191.72.24.94191.72.24.9530
196191.72.24.96/27191.72.24.97 to 191.72.24.126191.72.24.12730
197191.72.24.128/27191.72.24.129 to 191.72.24.158191.72.24.15930
198191.72.24.160/27191.72.24.161 to 191.72.24.190191.72.24.19130
199191.72.24.192/27191.72.24.193 to 191.72.24.222191.72.24.22330
200191.72.24.224/27191.72.24.225 to 191.72.24.254191.72.24.25530
201191.72.25.0/27191.72.25.1 to 191.72.25.30191.72.25.3130
202191.72.25.32/27191.72.25.33 to 191.72.25.62191.72.25.6330
203191.72.25.64/27191.72.25.65 to 191.72.25.94191.72.25.9530
204191.72.25.96/27191.72.25.97 to 191.72.25.126191.72.25.12730
205191.72.25.128/27191.72.25.129 to 191.72.25.158191.72.25.15930
206191.72.25.160/27191.72.25.161 to 191.72.25.190191.72.25.19130
207191.72.25.192/27191.72.25.193 to 191.72.25.222191.72.25.22330
208191.72.25.224/27191.72.25.225 to 191.72.25.254191.72.25.25530
209191.72.26.0/27191.72.26.1 to 191.72.26.30191.72.26.3130
210191.72.26.32/27191.72.26.33 to 191.72.26.62191.72.26.6330
211191.72.26.64/27191.72.26.65 to 191.72.26.94191.72.26.9530
212191.72.26.96/27191.72.26.97 to 191.72.26.126191.72.26.12730
213191.72.26.128/27191.72.26.129 to 191.72.26.158191.72.26.15930
214191.72.26.160/27191.72.26.161 to 191.72.26.190191.72.26.19130
215191.72.26.192/27191.72.26.193 to 191.72.26.222191.72.26.22330
216191.72.26.224/27191.72.26.225 to 191.72.26.254191.72.26.25530
217191.72.27.0/27191.72.27.1 to 191.72.27.30191.72.27.3130
218191.72.27.32/27191.72.27.33 to 191.72.27.62191.72.27.6330
219191.72.27.64/27191.72.27.65 to 191.72.27.94191.72.27.9530
220191.72.27.96/27191.72.27.97 to 191.72.27.126191.72.27.12730
221191.72.27.128/27191.72.27.129 to 191.72.27.158191.72.27.15930
222191.72.27.160/27191.72.27.161 to 191.72.27.190191.72.27.19130
223191.72.27.192/27191.72.27.193 to 191.72.27.222191.72.27.22330
224191.72.27.224/27191.72.27.225 to 191.72.27.254191.72.27.25530
225191.72.28.0/27191.72.28.1 to 191.72.28.30191.72.28.3130
226191.72.28.32/27191.72.28.33 to 191.72.28.62191.72.28.6330
227191.72.28.64/27191.72.28.65 to 191.72.28.94191.72.28.9530
228191.72.28.96/27191.72.28.97 to 191.72.28.126191.72.28.12730
229191.72.28.128/27191.72.28.129 to 191.72.28.158191.72.28.15930
230191.72.28.160/27191.72.28.161 to 191.72.28.190191.72.28.19130
231191.72.28.192/27191.72.28.193 to 191.72.28.222191.72.28.22330
232191.72.28.224/27191.72.28.225 to 191.72.28.254191.72.28.25530
233191.72.29.0/27191.72.29.1 to 191.72.29.30191.72.29.3130
234191.72.29.32/27191.72.29.33 to 191.72.29.62191.72.29.6330
235191.72.29.64/27191.72.29.65 to 191.72.29.94191.72.29.9530
236191.72.29.96/27191.72.29.97 to 191.72.29.126191.72.29.12730
237191.72.29.128/27191.72.29.129 to 191.72.29.158191.72.29.15930
238191.72.29.160/27191.72.29.161 to 191.72.29.190191.72.29.19130
239191.72.29.192/27191.72.29.193 to 191.72.29.222191.72.29.22330
240191.72.29.224/27191.72.29.225 to 191.72.29.254191.72.29.25530
241191.72.30.0/27191.72.30.1 to 191.72.30.30191.72.30.3130
242191.72.30.32/27191.72.30.33 to 191.72.30.62191.72.30.6330
243191.72.30.64/27191.72.30.65 to 191.72.30.94191.72.30.9530
244191.72.30.96/27191.72.30.97 to 191.72.30.126191.72.30.12730
245191.72.30.128/27191.72.30.129 to 191.72.30.158191.72.30.15930
246191.72.30.160/27191.72.30.161 to 191.72.30.190191.72.30.19130
247191.72.30.192/27191.72.30.193 to 191.72.30.222191.72.30.22330
248191.72.30.224/27191.72.30.225 to 191.72.30.254191.72.30.25530
249191.72.31.0/27191.72.31.1 to 191.72.31.30191.72.31.3130
250191.72.31.32/27191.72.31.33 to 191.72.31.62191.72.31.6330
251191.72.31.64/27191.72.31.65 to 191.72.31.94191.72.31.9530
252191.72.31.96/27191.72.31.97 to 191.72.31.126191.72.31.12730
253191.72.31.128/27191.72.31.129 to 191.72.31.158191.72.31.15930
254191.72.31.160/27191.72.31.161 to 191.72.31.190191.72.31.19130
255191.72.31.192/27191.72.31.193 to 191.72.31.222191.72.31.22330
256191.72.31.224/27191.72.31.225 to 191.72.31.254191.72.31.25530

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.