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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.

Network191.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
191.0.0.0
Broadcast address
191.255.255.255
First usable
191.0.0.1
Last usable
191.255.255.254
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
B (default /16)
As numbers
Hex BF000000 · Integer 3204448256 to 3221225471
Reverse DNS zone
191.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10111111..00000000.00000000.00000000191.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network10111111..00000000.00000000.00000000191.0.0.0
Broadcast10111111..11111111.11111111.11111111191.255.255.255
Split into smaller subnets/17
/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)

191.0.0.0/8 makes 512 subnets of /17; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1191.0.0.0/17191.0.0.1 to 191.0.127.254191.0.127.25532,766
2191.0.128.0/17191.0.128.1 to 191.0.255.254191.0.255.25532,766
3191.1.0.0/17191.1.0.1 to 191.1.127.254191.1.127.25532,766
4191.1.128.0/17191.1.128.1 to 191.1.255.254191.1.255.25532,766
5191.2.0.0/17191.2.0.1 to 191.2.127.254191.2.127.25532,766
6191.2.128.0/17191.2.128.1 to 191.2.255.254191.2.255.25532,766
7191.3.0.0/17191.3.0.1 to 191.3.127.254191.3.127.25532,766
8191.3.128.0/17191.3.128.1 to 191.3.255.254191.3.255.25532,766
9191.4.0.0/17191.4.0.1 to 191.4.127.254191.4.127.25532,766
10191.4.128.0/17191.4.128.1 to 191.4.255.254191.4.255.25532,766
11191.5.0.0/17191.5.0.1 to 191.5.127.254191.5.127.25532,766
12191.5.128.0/17191.5.128.1 to 191.5.255.254191.5.255.25532,766
13191.6.0.0/17191.6.0.1 to 191.6.127.254191.6.127.25532,766
14191.6.128.0/17191.6.128.1 to 191.6.255.254191.6.255.25532,766
15191.7.0.0/17191.7.0.1 to 191.7.127.254191.7.127.25532,766
16191.7.128.0/17191.7.128.1 to 191.7.255.254191.7.255.25532,766
17191.8.0.0/17191.8.0.1 to 191.8.127.254191.8.127.25532,766
18191.8.128.0/17191.8.128.1 to 191.8.255.254191.8.255.25532,766
19191.9.0.0/17191.9.0.1 to 191.9.127.254191.9.127.25532,766
20191.9.128.0/17191.9.128.1 to 191.9.255.254191.9.255.25532,766
21191.10.0.0/17191.10.0.1 to 191.10.127.254191.10.127.25532,766
22191.10.128.0/17191.10.128.1 to 191.10.255.254191.10.255.25532,766
23191.11.0.0/17191.11.0.1 to 191.11.127.254191.11.127.25532,766
24191.11.128.0/17191.11.128.1 to 191.11.255.254191.11.255.25532,766
25191.12.0.0/17191.12.0.1 to 191.12.127.254191.12.127.25532,766
26191.12.128.0/17191.12.128.1 to 191.12.255.254191.12.255.25532,766
27191.13.0.0/17191.13.0.1 to 191.13.127.254191.13.127.25532,766
28191.13.128.0/17191.13.128.1 to 191.13.255.254191.13.255.25532,766
29191.14.0.0/17191.14.0.1 to 191.14.127.254191.14.127.25532,766
30191.14.128.0/17191.14.128.1 to 191.14.255.254191.14.255.25532,766
31191.15.0.0/17191.15.0.1 to 191.15.127.254191.15.127.25532,766
32191.15.128.0/17191.15.128.1 to 191.15.255.254191.15.255.25532,766
33191.16.0.0/17191.16.0.1 to 191.16.127.254191.16.127.25532,766
34191.16.128.0/17191.16.128.1 to 191.16.255.254191.16.255.25532,766
35191.17.0.0/17191.17.0.1 to 191.17.127.254191.17.127.25532,766
36191.17.128.0/17191.17.128.1 to 191.17.255.254191.17.255.25532,766
37191.18.0.0/17191.18.0.1 to 191.18.127.254191.18.127.25532,766
38191.18.128.0/17191.18.128.1 to 191.18.255.254191.18.255.25532,766
39191.19.0.0/17191.19.0.1 to 191.19.127.254191.19.127.25532,766
40191.19.128.0/17191.19.128.1 to 191.19.255.254191.19.255.25532,766
41191.20.0.0/17191.20.0.1 to 191.20.127.254191.20.127.25532,766
42191.20.128.0/17191.20.128.1 to 191.20.255.254191.20.255.25532,766
43191.21.0.0/17191.21.0.1 to 191.21.127.254191.21.127.25532,766
44191.21.128.0/17191.21.128.1 to 191.21.255.254191.21.255.25532,766
45191.22.0.0/17191.22.0.1 to 191.22.127.254191.22.127.25532,766
46191.22.128.0/17191.22.128.1 to 191.22.255.254191.22.255.25532,766
47191.23.0.0/17191.23.0.1 to 191.23.127.254191.23.127.25532,766
48191.23.128.0/17191.23.128.1 to 191.23.255.254191.23.255.25532,766
49191.24.0.0/17191.24.0.1 to 191.24.127.254191.24.127.25532,766
50191.24.128.0/17191.24.128.1 to 191.24.255.254191.24.255.25532,766
51191.25.0.0/17191.25.0.1 to 191.25.127.254191.25.127.25532,766
52191.25.128.0/17191.25.128.1 to 191.25.255.254191.25.255.25532,766
53191.26.0.0/17191.26.0.1 to 191.26.127.254191.26.127.25532,766
54191.26.128.0/17191.26.128.1 to 191.26.255.254191.26.255.25532,766
55191.27.0.0/17191.27.0.1 to 191.27.127.254191.27.127.25532,766
56191.27.128.0/17191.27.128.1 to 191.27.255.254191.27.255.25532,766
57191.28.0.0/17191.28.0.1 to 191.28.127.254191.28.127.25532,766
58191.28.128.0/17191.28.128.1 to 191.28.255.254191.28.255.25532,766
59191.29.0.0/17191.29.0.1 to 191.29.127.254191.29.127.25532,766
60191.29.128.0/17191.29.128.1 to 191.29.255.254191.29.255.25532,766
61191.30.0.0/17191.30.0.1 to 191.30.127.254191.30.127.25532,766
62191.30.128.0/17191.30.128.1 to 191.30.255.254191.30.255.25532,766
63191.31.0.0/17191.31.0.1 to 191.31.127.254191.31.127.25532,766
64191.31.128.0/17191.31.128.1 to 191.31.255.254191.31.255.25532,766
65191.32.0.0/17191.32.0.1 to 191.32.127.254191.32.127.25532,766
66191.32.128.0/17191.32.128.1 to 191.32.255.254191.32.255.25532,766
67191.33.0.0/17191.33.0.1 to 191.33.127.254191.33.127.25532,766
68191.33.128.0/17191.33.128.1 to 191.33.255.254191.33.255.25532,766
69191.34.0.0/17191.34.0.1 to 191.34.127.254191.34.127.25532,766
70191.34.128.0/17191.34.128.1 to 191.34.255.254191.34.255.25532,766
71191.35.0.0/17191.35.0.1 to 191.35.127.254191.35.127.25532,766
72191.35.128.0/17191.35.128.1 to 191.35.255.254191.35.255.25532,766
73191.36.0.0/17191.36.0.1 to 191.36.127.254191.36.127.25532,766
74191.36.128.0/17191.36.128.1 to 191.36.255.254191.36.255.25532,766
75191.37.0.0/17191.37.0.1 to 191.37.127.254191.37.127.25532,766
76191.37.128.0/17191.37.128.1 to 191.37.255.254191.37.255.25532,766
77191.38.0.0/17191.38.0.1 to 191.38.127.254191.38.127.25532,766
78191.38.128.0/17191.38.128.1 to 191.38.255.254191.38.255.25532,766
79191.39.0.0/17191.39.0.1 to 191.39.127.254191.39.127.25532,766
80191.39.128.0/17191.39.128.1 to 191.39.255.254191.39.255.25532,766
81191.40.0.0/17191.40.0.1 to 191.40.127.254191.40.127.25532,766
82191.40.128.0/17191.40.128.1 to 191.40.255.254191.40.255.25532,766
83191.41.0.0/17191.41.0.1 to 191.41.127.254191.41.127.25532,766
84191.41.128.0/17191.41.128.1 to 191.41.255.254191.41.255.25532,766
85191.42.0.0/17191.42.0.1 to 191.42.127.254191.42.127.25532,766
86191.42.128.0/17191.42.128.1 to 191.42.255.254191.42.255.25532,766
87191.43.0.0/17191.43.0.1 to 191.43.127.254191.43.127.25532,766
88191.43.128.0/17191.43.128.1 to 191.43.255.254191.43.255.25532,766
89191.44.0.0/17191.44.0.1 to 191.44.127.254191.44.127.25532,766
90191.44.128.0/17191.44.128.1 to 191.44.255.254191.44.255.25532,766
91191.45.0.0/17191.45.0.1 to 191.45.127.254191.45.127.25532,766
92191.45.128.0/17191.45.128.1 to 191.45.255.254191.45.255.25532,766
93191.46.0.0/17191.46.0.1 to 191.46.127.254191.46.127.25532,766
94191.46.128.0/17191.46.128.1 to 191.46.255.254191.46.255.25532,766
95191.47.0.0/17191.47.0.1 to 191.47.127.254191.47.127.25532,766
96191.47.128.0/17191.47.128.1 to 191.47.255.254191.47.255.25532,766
97191.48.0.0/17191.48.0.1 to 191.48.127.254191.48.127.25532,766
98191.48.128.0/17191.48.128.1 to 191.48.255.254191.48.255.25532,766
99191.49.0.0/17191.49.0.1 to 191.49.127.254191.49.127.25532,766
100191.49.128.0/17191.49.128.1 to 191.49.255.254191.49.255.25532,766
101191.50.0.0/17191.50.0.1 to 191.50.127.254191.50.127.25532,766
102191.50.128.0/17191.50.128.1 to 191.50.255.254191.50.255.25532,766
103191.51.0.0/17191.51.0.1 to 191.51.127.254191.51.127.25532,766
104191.51.128.0/17191.51.128.1 to 191.51.255.254191.51.255.25532,766
105191.52.0.0/17191.52.0.1 to 191.52.127.254191.52.127.25532,766
106191.52.128.0/17191.52.128.1 to 191.52.255.254191.52.255.25532,766
107191.53.0.0/17191.53.0.1 to 191.53.127.254191.53.127.25532,766
108191.53.128.0/17191.53.128.1 to 191.53.255.254191.53.255.25532,766
109191.54.0.0/17191.54.0.1 to 191.54.127.254191.54.127.25532,766
110191.54.128.0/17191.54.128.1 to 191.54.255.254191.54.255.25532,766
111191.55.0.0/17191.55.0.1 to 191.55.127.254191.55.127.25532,766
112191.55.128.0/17191.55.128.1 to 191.55.255.254191.55.255.25532,766
113191.56.0.0/17191.56.0.1 to 191.56.127.254191.56.127.25532,766
114191.56.128.0/17191.56.128.1 to 191.56.255.254191.56.255.25532,766
115191.57.0.0/17191.57.0.1 to 191.57.127.254191.57.127.25532,766
116191.57.128.0/17191.57.128.1 to 191.57.255.254191.57.255.25532,766
117191.58.0.0/17191.58.0.1 to 191.58.127.254191.58.127.25532,766
118191.58.128.0/17191.58.128.1 to 191.58.255.254191.58.255.25532,766
119191.59.0.0/17191.59.0.1 to 191.59.127.254191.59.127.25532,766
120191.59.128.0/17191.59.128.1 to 191.59.255.254191.59.255.25532,766
121191.60.0.0/17191.60.0.1 to 191.60.127.254191.60.127.25532,766
122191.60.128.0/17191.60.128.1 to 191.60.255.254191.60.255.25532,766
123191.61.0.0/17191.61.0.1 to 191.61.127.254191.61.127.25532,766
124191.61.128.0/17191.61.128.1 to 191.61.255.254191.61.255.25532,766
125191.62.0.0/17191.62.0.1 to 191.62.127.254191.62.127.25532,766
126191.62.128.0/17191.62.128.1 to 191.62.255.254191.62.255.25532,766
127191.63.0.0/17191.63.0.1 to 191.63.127.254191.63.127.25532,766
128191.63.128.0/17191.63.128.1 to 191.63.255.254191.63.255.25532,766
129191.64.0.0/17191.64.0.1 to 191.64.127.254191.64.127.25532,766
130191.64.128.0/17191.64.128.1 to 191.64.255.254191.64.255.25532,766
131191.65.0.0/17191.65.0.1 to 191.65.127.254191.65.127.25532,766
132191.65.128.0/17191.65.128.1 to 191.65.255.254191.65.255.25532,766
133191.66.0.0/17191.66.0.1 to 191.66.127.254191.66.127.25532,766
134191.66.128.0/17191.66.128.1 to 191.66.255.254191.66.255.25532,766
135191.67.0.0/17191.67.0.1 to 191.67.127.254191.67.127.25532,766
136191.67.128.0/17191.67.128.1 to 191.67.255.254191.67.255.25532,766
137191.68.0.0/17191.68.0.1 to 191.68.127.254191.68.127.25532,766
138191.68.128.0/17191.68.128.1 to 191.68.255.254191.68.255.25532,766
139191.69.0.0/17191.69.0.1 to 191.69.127.254191.69.127.25532,766
140191.69.128.0/17191.69.128.1 to 191.69.255.254191.69.255.25532,766
141191.70.0.0/17191.70.0.1 to 191.70.127.254191.70.127.25532,766
142191.70.128.0/17191.70.128.1 to 191.70.255.254191.70.255.25532,766
143191.71.0.0/17191.71.0.1 to 191.71.127.254191.71.127.25532,766
144191.71.128.0/17191.71.128.1 to 191.71.255.254191.71.255.25532,766
145191.72.0.0/17191.72.0.1 to 191.72.127.254191.72.127.25532,766
146191.72.128.0/17191.72.128.1 to 191.72.255.254191.72.255.25532,766
147191.73.0.0/17191.73.0.1 to 191.73.127.254191.73.127.25532,766
148191.73.128.0/17191.73.128.1 to 191.73.255.254191.73.255.25532,766
149191.74.0.0/17191.74.0.1 to 191.74.127.254191.74.127.25532,766
150191.74.128.0/17191.74.128.1 to 191.74.255.254191.74.255.25532,766
151191.75.0.0/17191.75.0.1 to 191.75.127.254191.75.127.25532,766
152191.75.128.0/17191.75.128.1 to 191.75.255.254191.75.255.25532,766
153191.76.0.0/17191.76.0.1 to 191.76.127.254191.76.127.25532,766
154191.76.128.0/17191.76.128.1 to 191.76.255.254191.76.255.25532,766
155191.77.0.0/17191.77.0.1 to 191.77.127.254191.77.127.25532,766
156191.77.128.0/17191.77.128.1 to 191.77.255.254191.77.255.25532,766
157191.78.0.0/17191.78.0.1 to 191.78.127.254191.78.127.25532,766
158191.78.128.0/17191.78.128.1 to 191.78.255.254191.78.255.25532,766
159191.79.0.0/17191.79.0.1 to 191.79.127.254191.79.127.25532,766
160191.79.128.0/17191.79.128.1 to 191.79.255.254191.79.255.25532,766
161191.80.0.0/17191.80.0.1 to 191.80.127.254191.80.127.25532,766
162191.80.128.0/17191.80.128.1 to 191.80.255.254191.80.255.25532,766
163191.81.0.0/17191.81.0.1 to 191.81.127.254191.81.127.25532,766
164191.81.128.0/17191.81.128.1 to 191.81.255.254191.81.255.25532,766
165191.82.0.0/17191.82.0.1 to 191.82.127.254191.82.127.25532,766
166191.82.128.0/17191.82.128.1 to 191.82.255.254191.82.255.25532,766
167191.83.0.0/17191.83.0.1 to 191.83.127.254191.83.127.25532,766
168191.83.128.0/17191.83.128.1 to 191.83.255.254191.83.255.25532,766
169191.84.0.0/17191.84.0.1 to 191.84.127.254191.84.127.25532,766
170191.84.128.0/17191.84.128.1 to 191.84.255.254191.84.255.25532,766
171191.85.0.0/17191.85.0.1 to 191.85.127.254191.85.127.25532,766
172191.85.128.0/17191.85.128.1 to 191.85.255.254191.85.255.25532,766
173191.86.0.0/17191.86.0.1 to 191.86.127.254191.86.127.25532,766
174191.86.128.0/17191.86.128.1 to 191.86.255.254191.86.255.25532,766
175191.87.0.0/17191.87.0.1 to 191.87.127.254191.87.127.25532,766
176191.87.128.0/17191.87.128.1 to 191.87.255.254191.87.255.25532,766
177191.88.0.0/17191.88.0.1 to 191.88.127.254191.88.127.25532,766
178191.88.128.0/17191.88.128.1 to 191.88.255.254191.88.255.25532,766
179191.89.0.0/17191.89.0.1 to 191.89.127.254191.89.127.25532,766
180191.89.128.0/17191.89.128.1 to 191.89.255.254191.89.255.25532,766
181191.90.0.0/17191.90.0.1 to 191.90.127.254191.90.127.25532,766
182191.90.128.0/17191.90.128.1 to 191.90.255.254191.90.255.25532,766
183191.91.0.0/17191.91.0.1 to 191.91.127.254191.91.127.25532,766
184191.91.128.0/17191.91.128.1 to 191.91.255.254191.91.255.25532,766
185191.92.0.0/17191.92.0.1 to 191.92.127.254191.92.127.25532,766
186191.92.128.0/17191.92.128.1 to 191.92.255.254191.92.255.25532,766
187191.93.0.0/17191.93.0.1 to 191.93.127.254191.93.127.25532,766
188191.93.128.0/17191.93.128.1 to 191.93.255.254191.93.255.25532,766
189191.94.0.0/17191.94.0.1 to 191.94.127.254191.94.127.25532,766
190191.94.128.0/17191.94.128.1 to 191.94.255.254191.94.255.25532,766
191191.95.0.0/17191.95.0.1 to 191.95.127.254191.95.127.25532,766
192191.95.128.0/17191.95.128.1 to 191.95.255.254191.95.255.25532,766
193191.96.0.0/17191.96.0.1 to 191.96.127.254191.96.127.25532,766
194191.96.128.0/17191.96.128.1 to 191.96.255.254191.96.255.25532,766
195191.97.0.0/17191.97.0.1 to 191.97.127.254191.97.127.25532,766
196191.97.128.0/17191.97.128.1 to 191.97.255.254191.97.255.25532,766
197191.98.0.0/17191.98.0.1 to 191.98.127.254191.98.127.25532,766
198191.98.128.0/17191.98.128.1 to 191.98.255.254191.98.255.25532,766
199191.99.0.0/17191.99.0.1 to 191.99.127.254191.99.127.25532,766
200191.99.128.0/17191.99.128.1 to 191.99.255.254191.99.255.25532,766
201191.100.0.0/17191.100.0.1 to 191.100.127.254191.100.127.25532,766
202191.100.128.0/17191.100.128.1 to 191.100.255.254191.100.255.25532,766
203191.101.0.0/17191.101.0.1 to 191.101.127.254191.101.127.25532,766
204191.101.128.0/17191.101.128.1 to 191.101.255.254191.101.255.25532,766
205191.102.0.0/17191.102.0.1 to 191.102.127.254191.102.127.25532,766
206191.102.128.0/17191.102.128.1 to 191.102.255.254191.102.255.25532,766
207191.103.0.0/17191.103.0.1 to 191.103.127.254191.103.127.25532,766
208191.103.128.0/17191.103.128.1 to 191.103.255.254191.103.255.25532,766
209191.104.0.0/17191.104.0.1 to 191.104.127.254191.104.127.25532,766
210191.104.128.0/17191.104.128.1 to 191.104.255.254191.104.255.25532,766
211191.105.0.0/17191.105.0.1 to 191.105.127.254191.105.127.25532,766
212191.105.128.0/17191.105.128.1 to 191.105.255.254191.105.255.25532,766
213191.106.0.0/17191.106.0.1 to 191.106.127.254191.106.127.25532,766
214191.106.128.0/17191.106.128.1 to 191.106.255.254191.106.255.25532,766
215191.107.0.0/17191.107.0.1 to 191.107.127.254191.107.127.25532,766
216191.107.128.0/17191.107.128.1 to 191.107.255.254191.107.255.25532,766
217191.108.0.0/17191.108.0.1 to 191.108.127.254191.108.127.25532,766
218191.108.128.0/17191.108.128.1 to 191.108.255.254191.108.255.25532,766
219191.109.0.0/17191.109.0.1 to 191.109.127.254191.109.127.25532,766
220191.109.128.0/17191.109.128.1 to 191.109.255.254191.109.255.25532,766
221191.110.0.0/17191.110.0.1 to 191.110.127.254191.110.127.25532,766
222191.110.128.0/17191.110.128.1 to 191.110.255.254191.110.255.25532,766
223191.111.0.0/17191.111.0.1 to 191.111.127.254191.111.127.25532,766
224191.111.128.0/17191.111.128.1 to 191.111.255.254191.111.255.25532,766
225191.112.0.0/17191.112.0.1 to 191.112.127.254191.112.127.25532,766
226191.112.128.0/17191.112.128.1 to 191.112.255.254191.112.255.25532,766
227191.113.0.0/17191.113.0.1 to 191.113.127.254191.113.127.25532,766
228191.113.128.0/17191.113.128.1 to 191.113.255.254191.113.255.25532,766
229191.114.0.0/17191.114.0.1 to 191.114.127.254191.114.127.25532,766
230191.114.128.0/17191.114.128.1 to 191.114.255.254191.114.255.25532,766
231191.115.0.0/17191.115.0.1 to 191.115.127.254191.115.127.25532,766
232191.115.128.0/17191.115.128.1 to 191.115.255.254191.115.255.25532,766
233191.116.0.0/17191.116.0.1 to 191.116.127.254191.116.127.25532,766
234191.116.128.0/17191.116.128.1 to 191.116.255.254191.116.255.25532,766
235191.117.0.0/17191.117.0.1 to 191.117.127.254191.117.127.25532,766
236191.117.128.0/17191.117.128.1 to 191.117.255.254191.117.255.25532,766
237191.118.0.0/17191.118.0.1 to 191.118.127.254191.118.127.25532,766
238191.118.128.0/17191.118.128.1 to 191.118.255.254191.118.255.25532,766
239191.119.0.0/17191.119.0.1 to 191.119.127.254191.119.127.25532,766
240191.119.128.0/17191.119.128.1 to 191.119.255.254191.119.255.25532,766
241191.120.0.0/17191.120.0.1 to 191.120.127.254191.120.127.25532,766
242191.120.128.0/17191.120.128.1 to 191.120.255.254191.120.255.25532,766
243191.121.0.0/17191.121.0.1 to 191.121.127.254191.121.127.25532,766
244191.121.128.0/17191.121.128.1 to 191.121.255.254191.121.255.25532,766
245191.122.0.0/17191.122.0.1 to 191.122.127.254191.122.127.25532,766
246191.122.128.0/17191.122.128.1 to 191.122.255.254191.122.255.25532,766
247191.123.0.0/17191.123.0.1 to 191.123.127.254191.123.127.25532,766
248191.123.128.0/17191.123.128.1 to 191.123.255.254191.123.255.25532,766
249191.124.0.0/17191.124.0.1 to 191.124.127.254191.124.127.25532,766
250191.124.128.0/17191.124.128.1 to 191.124.255.254191.124.255.25532,766
251191.125.0.0/17191.125.0.1 to 191.125.127.254191.125.127.25532,766
252191.125.128.0/17191.125.128.1 to 191.125.255.254191.125.255.25532,766
253191.126.0.0/17191.126.0.1 to 191.126.127.254191.126.127.25532,766
254191.126.128.0/17191.126.128.1 to 191.126.255.254191.126.255.25532,766
255191.127.0.0/17191.127.0.1 to 191.127.127.254191.127.127.25532,766
256191.127.128.0/17191.127.128.1 to 191.127.255.254191.127.255.25532,766

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.