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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.

Network172.0.0.0/6
Usable hosts67,108,862
Subnet mask252.0.0.0
Addresses67,108,864
Network address
172.0.0.0
Broadcast address
175.255.255.255
First usable
172.0.0.1
Last usable
175.255.255.254
Usable hosts
67,108,862 (67,108,864 less the network and broadcast addresses)
Subnet mask
252.0.0.0
Wildcard mask
3.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/6
Type
Public public
Old class
B (default /16)
As numbers
Hex AC000000 · Integer 2885681152 to 2952790015
Reverse DNS zones
172.in-addr.arpa
173.in-addr.arpa
174.in-addr.arpa
175.in-addr.arpa
/6 is not on a 8-bit boundary, so it takes 4 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10101100.00000000.00000000.00000000172.0.0.0
Subnet mask11111100.00000000.00000000.00000000252.0.0.0
Network10101100.00000000.00000000.00000000172.0.0.0
Broadcast10101111.11111111.11111111.11111111175.255.255.255
Split into smaller subnets/17
/7 (2)/8 (4)/9 (8)/10 (16)/11 (32)/12 (64)/13 (128)/14 (256)/15 (512)/16 (1,024)/17 (2,048)/18 (4,096)

172.0.0.0/6 makes 2,048 subnets of /17; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1172.0.0.0/17172.0.0.1 to 172.0.127.254172.0.127.25532,766
2172.0.128.0/17172.0.128.1 to 172.0.255.254172.0.255.25532,766
3172.1.0.0/17172.1.0.1 to 172.1.127.254172.1.127.25532,766
4172.1.128.0/17172.1.128.1 to 172.1.255.254172.1.255.25532,766
5172.2.0.0/17172.2.0.1 to 172.2.127.254172.2.127.25532,766
6172.2.128.0/17172.2.128.1 to 172.2.255.254172.2.255.25532,766
7172.3.0.0/17172.3.0.1 to 172.3.127.254172.3.127.25532,766
8172.3.128.0/17172.3.128.1 to 172.3.255.254172.3.255.25532,766
9172.4.0.0/17172.4.0.1 to 172.4.127.254172.4.127.25532,766
10172.4.128.0/17172.4.128.1 to 172.4.255.254172.4.255.25532,766
11172.5.0.0/17172.5.0.1 to 172.5.127.254172.5.127.25532,766
12172.5.128.0/17172.5.128.1 to 172.5.255.254172.5.255.25532,766
13172.6.0.0/17172.6.0.1 to 172.6.127.254172.6.127.25532,766
14172.6.128.0/17172.6.128.1 to 172.6.255.254172.6.255.25532,766
15172.7.0.0/17172.7.0.1 to 172.7.127.254172.7.127.25532,766
16172.7.128.0/17172.7.128.1 to 172.7.255.254172.7.255.25532,766
17172.8.0.0/17172.8.0.1 to 172.8.127.254172.8.127.25532,766
18172.8.128.0/17172.8.128.1 to 172.8.255.254172.8.255.25532,766
19172.9.0.0/17172.9.0.1 to 172.9.127.254172.9.127.25532,766
20172.9.128.0/17172.9.128.1 to 172.9.255.254172.9.255.25532,766
21172.10.0.0/17172.10.0.1 to 172.10.127.254172.10.127.25532,766
22172.10.128.0/17172.10.128.1 to 172.10.255.254172.10.255.25532,766
23172.11.0.0/17172.11.0.1 to 172.11.127.254172.11.127.25532,766
24172.11.128.0/17172.11.128.1 to 172.11.255.254172.11.255.25532,766
25172.12.0.0/17172.12.0.1 to 172.12.127.254172.12.127.25532,766
26172.12.128.0/17172.12.128.1 to 172.12.255.254172.12.255.25532,766
27172.13.0.0/17172.13.0.1 to 172.13.127.254172.13.127.25532,766
28172.13.128.0/17172.13.128.1 to 172.13.255.254172.13.255.25532,766
29172.14.0.0/17172.14.0.1 to 172.14.127.254172.14.127.25532,766
30172.14.128.0/17172.14.128.1 to 172.14.255.254172.14.255.25532,766
31172.15.0.0/17172.15.0.1 to 172.15.127.254172.15.127.25532,766
32172.15.128.0/17172.15.128.1 to 172.15.255.254172.15.255.25532,766
33172.16.0.0/17172.16.0.1 to 172.16.127.254172.16.127.25532,766
34172.16.128.0/17172.16.128.1 to 172.16.255.254172.16.255.25532,766
35172.17.0.0/17172.17.0.1 to 172.17.127.254172.17.127.25532,766
36172.17.128.0/17172.17.128.1 to 172.17.255.254172.17.255.25532,766
37172.18.0.0/17172.18.0.1 to 172.18.127.254172.18.127.25532,766
38172.18.128.0/17172.18.128.1 to 172.18.255.254172.18.255.25532,766
39172.19.0.0/17172.19.0.1 to 172.19.127.254172.19.127.25532,766
40172.19.128.0/17172.19.128.1 to 172.19.255.254172.19.255.25532,766
41172.20.0.0/17172.20.0.1 to 172.20.127.254172.20.127.25532,766
42172.20.128.0/17172.20.128.1 to 172.20.255.254172.20.255.25532,766
43172.21.0.0/17172.21.0.1 to 172.21.127.254172.21.127.25532,766
44172.21.128.0/17172.21.128.1 to 172.21.255.254172.21.255.25532,766
45172.22.0.0/17172.22.0.1 to 172.22.127.254172.22.127.25532,766
46172.22.128.0/17172.22.128.1 to 172.22.255.254172.22.255.25532,766
47172.23.0.0/17172.23.0.1 to 172.23.127.254172.23.127.25532,766
48172.23.128.0/17172.23.128.1 to 172.23.255.254172.23.255.25532,766
49172.24.0.0/17172.24.0.1 to 172.24.127.254172.24.127.25532,766
50172.24.128.0/17172.24.128.1 to 172.24.255.254172.24.255.25532,766
51172.25.0.0/17172.25.0.1 to 172.25.127.254172.25.127.25532,766
52172.25.128.0/17172.25.128.1 to 172.25.255.254172.25.255.25532,766
53172.26.0.0/17172.26.0.1 to 172.26.127.254172.26.127.25532,766
54172.26.128.0/17172.26.128.1 to 172.26.255.254172.26.255.25532,766
55172.27.0.0/17172.27.0.1 to 172.27.127.254172.27.127.25532,766
56172.27.128.0/17172.27.128.1 to 172.27.255.254172.27.255.25532,766
57172.28.0.0/17172.28.0.1 to 172.28.127.254172.28.127.25532,766
58172.28.128.0/17172.28.128.1 to 172.28.255.254172.28.255.25532,766
59172.29.0.0/17172.29.0.1 to 172.29.127.254172.29.127.25532,766
60172.29.128.0/17172.29.128.1 to 172.29.255.254172.29.255.25532,766
61172.30.0.0/17172.30.0.1 to 172.30.127.254172.30.127.25532,766
62172.30.128.0/17172.30.128.1 to 172.30.255.254172.30.255.25532,766
63172.31.0.0/17172.31.0.1 to 172.31.127.254172.31.127.25532,766
64172.31.128.0/17172.31.128.1 to 172.31.255.254172.31.255.25532,766
65172.32.0.0/17172.32.0.1 to 172.32.127.254172.32.127.25532,766
66172.32.128.0/17172.32.128.1 to 172.32.255.254172.32.255.25532,766
67172.33.0.0/17172.33.0.1 to 172.33.127.254172.33.127.25532,766
68172.33.128.0/17172.33.128.1 to 172.33.255.254172.33.255.25532,766
69172.34.0.0/17172.34.0.1 to 172.34.127.254172.34.127.25532,766
70172.34.128.0/17172.34.128.1 to 172.34.255.254172.34.255.25532,766
71172.35.0.0/17172.35.0.1 to 172.35.127.254172.35.127.25532,766
72172.35.128.0/17172.35.128.1 to 172.35.255.254172.35.255.25532,766
73172.36.0.0/17172.36.0.1 to 172.36.127.254172.36.127.25532,766
74172.36.128.0/17172.36.128.1 to 172.36.255.254172.36.255.25532,766
75172.37.0.0/17172.37.0.1 to 172.37.127.254172.37.127.25532,766
76172.37.128.0/17172.37.128.1 to 172.37.255.254172.37.255.25532,766
77172.38.0.0/17172.38.0.1 to 172.38.127.254172.38.127.25532,766
78172.38.128.0/17172.38.128.1 to 172.38.255.254172.38.255.25532,766
79172.39.0.0/17172.39.0.1 to 172.39.127.254172.39.127.25532,766
80172.39.128.0/17172.39.128.1 to 172.39.255.254172.39.255.25532,766
81172.40.0.0/17172.40.0.1 to 172.40.127.254172.40.127.25532,766
82172.40.128.0/17172.40.128.1 to 172.40.255.254172.40.255.25532,766
83172.41.0.0/17172.41.0.1 to 172.41.127.254172.41.127.25532,766
84172.41.128.0/17172.41.128.1 to 172.41.255.254172.41.255.25532,766
85172.42.0.0/17172.42.0.1 to 172.42.127.254172.42.127.25532,766
86172.42.128.0/17172.42.128.1 to 172.42.255.254172.42.255.25532,766
87172.43.0.0/17172.43.0.1 to 172.43.127.254172.43.127.25532,766
88172.43.128.0/17172.43.128.1 to 172.43.255.254172.43.255.25532,766
89172.44.0.0/17172.44.0.1 to 172.44.127.254172.44.127.25532,766
90172.44.128.0/17172.44.128.1 to 172.44.255.254172.44.255.25532,766
91172.45.0.0/17172.45.0.1 to 172.45.127.254172.45.127.25532,766
92172.45.128.0/17172.45.128.1 to 172.45.255.254172.45.255.25532,766
93172.46.0.0/17172.46.0.1 to 172.46.127.254172.46.127.25532,766
94172.46.128.0/17172.46.128.1 to 172.46.255.254172.46.255.25532,766
95172.47.0.0/17172.47.0.1 to 172.47.127.254172.47.127.25532,766
96172.47.128.0/17172.47.128.1 to 172.47.255.254172.47.255.25532,766
97172.48.0.0/17172.48.0.1 to 172.48.127.254172.48.127.25532,766
98172.48.128.0/17172.48.128.1 to 172.48.255.254172.48.255.25532,766
99172.49.0.0/17172.49.0.1 to 172.49.127.254172.49.127.25532,766
100172.49.128.0/17172.49.128.1 to 172.49.255.254172.49.255.25532,766
101172.50.0.0/17172.50.0.1 to 172.50.127.254172.50.127.25532,766
102172.50.128.0/17172.50.128.1 to 172.50.255.254172.50.255.25532,766
103172.51.0.0/17172.51.0.1 to 172.51.127.254172.51.127.25532,766
104172.51.128.0/17172.51.128.1 to 172.51.255.254172.51.255.25532,766
105172.52.0.0/17172.52.0.1 to 172.52.127.254172.52.127.25532,766
106172.52.128.0/17172.52.128.1 to 172.52.255.254172.52.255.25532,766
107172.53.0.0/17172.53.0.1 to 172.53.127.254172.53.127.25532,766
108172.53.128.0/17172.53.128.1 to 172.53.255.254172.53.255.25532,766
109172.54.0.0/17172.54.0.1 to 172.54.127.254172.54.127.25532,766
110172.54.128.0/17172.54.128.1 to 172.54.255.254172.54.255.25532,766
111172.55.0.0/17172.55.0.1 to 172.55.127.254172.55.127.25532,766
112172.55.128.0/17172.55.128.1 to 172.55.255.254172.55.255.25532,766
113172.56.0.0/17172.56.0.1 to 172.56.127.254172.56.127.25532,766
114172.56.128.0/17172.56.128.1 to 172.56.255.254172.56.255.25532,766
115172.57.0.0/17172.57.0.1 to 172.57.127.254172.57.127.25532,766
116172.57.128.0/17172.57.128.1 to 172.57.255.254172.57.255.25532,766
117172.58.0.0/17172.58.0.1 to 172.58.127.254172.58.127.25532,766
118172.58.128.0/17172.58.128.1 to 172.58.255.254172.58.255.25532,766
119172.59.0.0/17172.59.0.1 to 172.59.127.254172.59.127.25532,766
120172.59.128.0/17172.59.128.1 to 172.59.255.254172.59.255.25532,766
121172.60.0.0/17172.60.0.1 to 172.60.127.254172.60.127.25532,766
122172.60.128.0/17172.60.128.1 to 172.60.255.254172.60.255.25532,766
123172.61.0.0/17172.61.0.1 to 172.61.127.254172.61.127.25532,766
124172.61.128.0/17172.61.128.1 to 172.61.255.254172.61.255.25532,766
125172.62.0.0/17172.62.0.1 to 172.62.127.254172.62.127.25532,766
126172.62.128.0/17172.62.128.1 to 172.62.255.254172.62.255.25532,766
127172.63.0.0/17172.63.0.1 to 172.63.127.254172.63.127.25532,766
128172.63.128.0/17172.63.128.1 to 172.63.255.254172.63.255.25532,766
129172.64.0.0/17172.64.0.1 to 172.64.127.254172.64.127.25532,766
130172.64.128.0/17172.64.128.1 to 172.64.255.254172.64.255.25532,766
131172.65.0.0/17172.65.0.1 to 172.65.127.254172.65.127.25532,766
132172.65.128.0/17172.65.128.1 to 172.65.255.254172.65.255.25532,766
133172.66.0.0/17172.66.0.1 to 172.66.127.254172.66.127.25532,766
134172.66.128.0/17172.66.128.1 to 172.66.255.254172.66.255.25532,766
135172.67.0.0/17172.67.0.1 to 172.67.127.254172.67.127.25532,766
136172.67.128.0/17172.67.128.1 to 172.67.255.254172.67.255.25532,766
137172.68.0.0/17172.68.0.1 to 172.68.127.254172.68.127.25532,766
138172.68.128.0/17172.68.128.1 to 172.68.255.254172.68.255.25532,766
139172.69.0.0/17172.69.0.1 to 172.69.127.254172.69.127.25532,766
140172.69.128.0/17172.69.128.1 to 172.69.255.254172.69.255.25532,766
141172.70.0.0/17172.70.0.1 to 172.70.127.254172.70.127.25532,766
142172.70.128.0/17172.70.128.1 to 172.70.255.254172.70.255.25532,766
143172.71.0.0/17172.71.0.1 to 172.71.127.254172.71.127.25532,766
144172.71.128.0/17172.71.128.1 to 172.71.255.254172.71.255.25532,766
145172.72.0.0/17172.72.0.1 to 172.72.127.254172.72.127.25532,766
146172.72.128.0/17172.72.128.1 to 172.72.255.254172.72.255.25532,766
147172.73.0.0/17172.73.0.1 to 172.73.127.254172.73.127.25532,766
148172.73.128.0/17172.73.128.1 to 172.73.255.254172.73.255.25532,766
149172.74.0.0/17172.74.0.1 to 172.74.127.254172.74.127.25532,766
150172.74.128.0/17172.74.128.1 to 172.74.255.254172.74.255.25532,766
151172.75.0.0/17172.75.0.1 to 172.75.127.254172.75.127.25532,766
152172.75.128.0/17172.75.128.1 to 172.75.255.254172.75.255.25532,766
153172.76.0.0/17172.76.0.1 to 172.76.127.254172.76.127.25532,766
154172.76.128.0/17172.76.128.1 to 172.76.255.254172.76.255.25532,766
155172.77.0.0/17172.77.0.1 to 172.77.127.254172.77.127.25532,766
156172.77.128.0/17172.77.128.1 to 172.77.255.254172.77.255.25532,766
157172.78.0.0/17172.78.0.1 to 172.78.127.254172.78.127.25532,766
158172.78.128.0/17172.78.128.1 to 172.78.255.254172.78.255.25532,766
159172.79.0.0/17172.79.0.1 to 172.79.127.254172.79.127.25532,766
160172.79.128.0/17172.79.128.1 to 172.79.255.254172.79.255.25532,766
161172.80.0.0/17172.80.0.1 to 172.80.127.254172.80.127.25532,766
162172.80.128.0/17172.80.128.1 to 172.80.255.254172.80.255.25532,766
163172.81.0.0/17172.81.0.1 to 172.81.127.254172.81.127.25532,766
164172.81.128.0/17172.81.128.1 to 172.81.255.254172.81.255.25532,766
165172.82.0.0/17172.82.0.1 to 172.82.127.254172.82.127.25532,766
166172.82.128.0/17172.82.128.1 to 172.82.255.254172.82.255.25532,766
167172.83.0.0/17172.83.0.1 to 172.83.127.254172.83.127.25532,766
168172.83.128.0/17172.83.128.1 to 172.83.255.254172.83.255.25532,766
169172.84.0.0/17172.84.0.1 to 172.84.127.254172.84.127.25532,766
170172.84.128.0/17172.84.128.1 to 172.84.255.254172.84.255.25532,766
171172.85.0.0/17172.85.0.1 to 172.85.127.254172.85.127.25532,766
172172.85.128.0/17172.85.128.1 to 172.85.255.254172.85.255.25532,766
173172.86.0.0/17172.86.0.1 to 172.86.127.254172.86.127.25532,766
174172.86.128.0/17172.86.128.1 to 172.86.255.254172.86.255.25532,766
175172.87.0.0/17172.87.0.1 to 172.87.127.254172.87.127.25532,766
176172.87.128.0/17172.87.128.1 to 172.87.255.254172.87.255.25532,766
177172.88.0.0/17172.88.0.1 to 172.88.127.254172.88.127.25532,766
178172.88.128.0/17172.88.128.1 to 172.88.255.254172.88.255.25532,766
179172.89.0.0/17172.89.0.1 to 172.89.127.254172.89.127.25532,766
180172.89.128.0/17172.89.128.1 to 172.89.255.254172.89.255.25532,766
181172.90.0.0/17172.90.0.1 to 172.90.127.254172.90.127.25532,766
182172.90.128.0/17172.90.128.1 to 172.90.255.254172.90.255.25532,766
183172.91.0.0/17172.91.0.1 to 172.91.127.254172.91.127.25532,766
184172.91.128.0/17172.91.128.1 to 172.91.255.254172.91.255.25532,766
185172.92.0.0/17172.92.0.1 to 172.92.127.254172.92.127.25532,766
186172.92.128.0/17172.92.128.1 to 172.92.255.254172.92.255.25532,766
187172.93.0.0/17172.93.0.1 to 172.93.127.254172.93.127.25532,766
188172.93.128.0/17172.93.128.1 to 172.93.255.254172.93.255.25532,766
189172.94.0.0/17172.94.0.1 to 172.94.127.254172.94.127.25532,766
190172.94.128.0/17172.94.128.1 to 172.94.255.254172.94.255.25532,766
191172.95.0.0/17172.95.0.1 to 172.95.127.254172.95.127.25532,766
192172.95.128.0/17172.95.128.1 to 172.95.255.254172.95.255.25532,766
193172.96.0.0/17172.96.0.1 to 172.96.127.254172.96.127.25532,766
194172.96.128.0/17172.96.128.1 to 172.96.255.254172.96.255.25532,766
195172.97.0.0/17172.97.0.1 to 172.97.127.254172.97.127.25532,766
196172.97.128.0/17172.97.128.1 to 172.97.255.254172.97.255.25532,766
197172.98.0.0/17172.98.0.1 to 172.98.127.254172.98.127.25532,766
198172.98.128.0/17172.98.128.1 to 172.98.255.254172.98.255.25532,766
199172.99.0.0/17172.99.0.1 to 172.99.127.254172.99.127.25532,766
200172.99.128.0/17172.99.128.1 to 172.99.255.254172.99.255.25532,766
201172.100.0.0/17172.100.0.1 to 172.100.127.254172.100.127.25532,766
202172.100.128.0/17172.100.128.1 to 172.100.255.254172.100.255.25532,766
203172.101.0.0/17172.101.0.1 to 172.101.127.254172.101.127.25532,766
204172.101.128.0/17172.101.128.1 to 172.101.255.254172.101.255.25532,766
205172.102.0.0/17172.102.0.1 to 172.102.127.254172.102.127.25532,766
206172.102.128.0/17172.102.128.1 to 172.102.255.254172.102.255.25532,766
207172.103.0.0/17172.103.0.1 to 172.103.127.254172.103.127.25532,766
208172.103.128.0/17172.103.128.1 to 172.103.255.254172.103.255.25532,766
209172.104.0.0/17172.104.0.1 to 172.104.127.254172.104.127.25532,766
210172.104.128.0/17172.104.128.1 to 172.104.255.254172.104.255.25532,766
211172.105.0.0/17172.105.0.1 to 172.105.127.254172.105.127.25532,766
212172.105.128.0/17172.105.128.1 to 172.105.255.254172.105.255.25532,766
213172.106.0.0/17172.106.0.1 to 172.106.127.254172.106.127.25532,766
214172.106.128.0/17172.106.128.1 to 172.106.255.254172.106.255.25532,766
215172.107.0.0/17172.107.0.1 to 172.107.127.254172.107.127.25532,766
216172.107.128.0/17172.107.128.1 to 172.107.255.254172.107.255.25532,766
217172.108.0.0/17172.108.0.1 to 172.108.127.254172.108.127.25532,766
218172.108.128.0/17172.108.128.1 to 172.108.255.254172.108.255.25532,766
219172.109.0.0/17172.109.0.1 to 172.109.127.254172.109.127.25532,766
220172.109.128.0/17172.109.128.1 to 172.109.255.254172.109.255.25532,766
221172.110.0.0/17172.110.0.1 to 172.110.127.254172.110.127.25532,766
222172.110.128.0/17172.110.128.1 to 172.110.255.254172.110.255.25532,766
223172.111.0.0/17172.111.0.1 to 172.111.127.254172.111.127.25532,766
224172.111.128.0/17172.111.128.1 to 172.111.255.254172.111.255.25532,766
225172.112.0.0/17172.112.0.1 to 172.112.127.254172.112.127.25532,766
226172.112.128.0/17172.112.128.1 to 172.112.255.254172.112.255.25532,766
227172.113.0.0/17172.113.0.1 to 172.113.127.254172.113.127.25532,766
228172.113.128.0/17172.113.128.1 to 172.113.255.254172.113.255.25532,766
229172.114.0.0/17172.114.0.1 to 172.114.127.254172.114.127.25532,766
230172.114.128.0/17172.114.128.1 to 172.114.255.254172.114.255.25532,766
231172.115.0.0/17172.115.0.1 to 172.115.127.254172.115.127.25532,766
232172.115.128.0/17172.115.128.1 to 172.115.255.254172.115.255.25532,766
233172.116.0.0/17172.116.0.1 to 172.116.127.254172.116.127.25532,766
234172.116.128.0/17172.116.128.1 to 172.116.255.254172.116.255.25532,766
235172.117.0.0/17172.117.0.1 to 172.117.127.254172.117.127.25532,766
236172.117.128.0/17172.117.128.1 to 172.117.255.254172.117.255.25532,766
237172.118.0.0/17172.118.0.1 to 172.118.127.254172.118.127.25532,766
238172.118.128.0/17172.118.128.1 to 172.118.255.254172.118.255.25532,766
239172.119.0.0/17172.119.0.1 to 172.119.127.254172.119.127.25532,766
240172.119.128.0/17172.119.128.1 to 172.119.255.254172.119.255.25532,766
241172.120.0.0/17172.120.0.1 to 172.120.127.254172.120.127.25532,766
242172.120.128.0/17172.120.128.1 to 172.120.255.254172.120.255.25532,766
243172.121.0.0/17172.121.0.1 to 172.121.127.254172.121.127.25532,766
244172.121.128.0/17172.121.128.1 to 172.121.255.254172.121.255.25532,766
245172.122.0.0/17172.122.0.1 to 172.122.127.254172.122.127.25532,766
246172.122.128.0/17172.122.128.1 to 172.122.255.254172.122.255.25532,766
247172.123.0.0/17172.123.0.1 to 172.123.127.254172.123.127.25532,766
248172.123.128.0/17172.123.128.1 to 172.123.255.254172.123.255.25532,766
249172.124.0.0/17172.124.0.1 to 172.124.127.254172.124.127.25532,766
250172.124.128.0/17172.124.128.1 to 172.124.255.254172.124.255.25532,766
251172.125.0.0/17172.125.0.1 to 172.125.127.254172.125.127.25532,766
252172.125.128.0/17172.125.128.1 to 172.125.255.254172.125.255.25532,766
253172.126.0.0/17172.126.0.1 to 172.126.127.254172.126.127.25532,766
254172.126.128.0/17172.126.128.1 to 172.126.255.254172.126.255.25532,766
255172.127.0.0/17172.127.0.1 to 172.127.127.254172.127.127.25532,766
256172.127.128.0/17172.127.128.1 to 172.127.255.254172.127.255.25532,766

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.