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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.

Network121.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
121.0.0.0
Broadcast address
121.127.255.255
First usable
121.0.0.1
Last usable
121.127.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Public public
Old class
A (default /8)
As numbers
Hex 79000000 · Integer 2030043136 to 2038431743
Reverse DNS zones
0.121.in-addr.arpa
1.121.in-addr.arpa
2.121.in-addr.arpa
3.121.in-addr.arpa
4.121.in-addr.arpa
5.121.in-addr.arpa
6.121.in-addr.arpa
7.121.in-addr.arpa
8.121.in-addr.arpa
9.121.in-addr.arpa
10.121.in-addr.arpa
11.121.in-addr.arpa
12.121.in-addr.arpa
13.121.in-addr.arpa
14.121.in-addr.arpa
15.121.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01111001.00000000.00000000.00000000121.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network01111001.00000000.00000000.00000000121.0.0.0
Broadcast01111001.01111111.11111111.11111111121.127.255.255
Split into smaller subnets/17
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

121.0.0.0/9 makes 256 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1121.0.0.0/17121.0.0.1 to 121.0.127.254121.0.127.25532,766
2121.0.128.0/17121.0.128.1 to 121.0.255.254121.0.255.25532,766
3121.1.0.0/17121.1.0.1 to 121.1.127.254121.1.127.25532,766
4121.1.128.0/17121.1.128.1 to 121.1.255.254121.1.255.25532,766
5121.2.0.0/17121.2.0.1 to 121.2.127.254121.2.127.25532,766
6121.2.128.0/17121.2.128.1 to 121.2.255.254121.2.255.25532,766
7121.3.0.0/17121.3.0.1 to 121.3.127.254121.3.127.25532,766
8121.3.128.0/17121.3.128.1 to 121.3.255.254121.3.255.25532,766
9121.4.0.0/17121.4.0.1 to 121.4.127.254121.4.127.25532,766
10121.4.128.0/17121.4.128.1 to 121.4.255.254121.4.255.25532,766
11121.5.0.0/17121.5.0.1 to 121.5.127.254121.5.127.25532,766
12121.5.128.0/17121.5.128.1 to 121.5.255.254121.5.255.25532,766
13121.6.0.0/17121.6.0.1 to 121.6.127.254121.6.127.25532,766
14121.6.128.0/17121.6.128.1 to 121.6.255.254121.6.255.25532,766
15121.7.0.0/17121.7.0.1 to 121.7.127.254121.7.127.25532,766
16121.7.128.0/17121.7.128.1 to 121.7.255.254121.7.255.25532,766
17121.8.0.0/17121.8.0.1 to 121.8.127.254121.8.127.25532,766
18121.8.128.0/17121.8.128.1 to 121.8.255.254121.8.255.25532,766
19121.9.0.0/17121.9.0.1 to 121.9.127.254121.9.127.25532,766
20121.9.128.0/17121.9.128.1 to 121.9.255.254121.9.255.25532,766
21121.10.0.0/17121.10.0.1 to 121.10.127.254121.10.127.25532,766
22121.10.128.0/17121.10.128.1 to 121.10.255.254121.10.255.25532,766
23121.11.0.0/17121.11.0.1 to 121.11.127.254121.11.127.25532,766
24121.11.128.0/17121.11.128.1 to 121.11.255.254121.11.255.25532,766
25121.12.0.0/17121.12.0.1 to 121.12.127.254121.12.127.25532,766
26121.12.128.0/17121.12.128.1 to 121.12.255.254121.12.255.25532,766
27121.13.0.0/17121.13.0.1 to 121.13.127.254121.13.127.25532,766
28121.13.128.0/17121.13.128.1 to 121.13.255.254121.13.255.25532,766
29121.14.0.0/17121.14.0.1 to 121.14.127.254121.14.127.25532,766
30121.14.128.0/17121.14.128.1 to 121.14.255.254121.14.255.25532,766
31121.15.0.0/17121.15.0.1 to 121.15.127.254121.15.127.25532,766
32121.15.128.0/17121.15.128.1 to 121.15.255.254121.15.255.25532,766
33121.16.0.0/17121.16.0.1 to 121.16.127.254121.16.127.25532,766
34121.16.128.0/17121.16.128.1 to 121.16.255.254121.16.255.25532,766
35121.17.0.0/17121.17.0.1 to 121.17.127.254121.17.127.25532,766
36121.17.128.0/17121.17.128.1 to 121.17.255.254121.17.255.25532,766
37121.18.0.0/17121.18.0.1 to 121.18.127.254121.18.127.25532,766
38121.18.128.0/17121.18.128.1 to 121.18.255.254121.18.255.25532,766
39121.19.0.0/17121.19.0.1 to 121.19.127.254121.19.127.25532,766
40121.19.128.0/17121.19.128.1 to 121.19.255.254121.19.255.25532,766
41121.20.0.0/17121.20.0.1 to 121.20.127.254121.20.127.25532,766
42121.20.128.0/17121.20.128.1 to 121.20.255.254121.20.255.25532,766
43121.21.0.0/17121.21.0.1 to 121.21.127.254121.21.127.25532,766
44121.21.128.0/17121.21.128.1 to 121.21.255.254121.21.255.25532,766
45121.22.0.0/17121.22.0.1 to 121.22.127.254121.22.127.25532,766
46121.22.128.0/17121.22.128.1 to 121.22.255.254121.22.255.25532,766
47121.23.0.0/17121.23.0.1 to 121.23.127.254121.23.127.25532,766
48121.23.128.0/17121.23.128.1 to 121.23.255.254121.23.255.25532,766
49121.24.0.0/17121.24.0.1 to 121.24.127.254121.24.127.25532,766
50121.24.128.0/17121.24.128.1 to 121.24.255.254121.24.255.25532,766
51121.25.0.0/17121.25.0.1 to 121.25.127.254121.25.127.25532,766
52121.25.128.0/17121.25.128.1 to 121.25.255.254121.25.255.25532,766
53121.26.0.0/17121.26.0.1 to 121.26.127.254121.26.127.25532,766
54121.26.128.0/17121.26.128.1 to 121.26.255.254121.26.255.25532,766
55121.27.0.0/17121.27.0.1 to 121.27.127.254121.27.127.25532,766
56121.27.128.0/17121.27.128.1 to 121.27.255.254121.27.255.25532,766
57121.28.0.0/17121.28.0.1 to 121.28.127.254121.28.127.25532,766
58121.28.128.0/17121.28.128.1 to 121.28.255.254121.28.255.25532,766
59121.29.0.0/17121.29.0.1 to 121.29.127.254121.29.127.25532,766
60121.29.128.0/17121.29.128.1 to 121.29.255.254121.29.255.25532,766
61121.30.0.0/17121.30.0.1 to 121.30.127.254121.30.127.25532,766
62121.30.128.0/17121.30.128.1 to 121.30.255.254121.30.255.25532,766
63121.31.0.0/17121.31.0.1 to 121.31.127.254121.31.127.25532,766
64121.31.128.0/17121.31.128.1 to 121.31.255.254121.31.255.25532,766
65121.32.0.0/17121.32.0.1 to 121.32.127.254121.32.127.25532,766
66121.32.128.0/17121.32.128.1 to 121.32.255.254121.32.255.25532,766
67121.33.0.0/17121.33.0.1 to 121.33.127.254121.33.127.25532,766
68121.33.128.0/17121.33.128.1 to 121.33.255.254121.33.255.25532,766
69121.34.0.0/17121.34.0.1 to 121.34.127.254121.34.127.25532,766
70121.34.128.0/17121.34.128.1 to 121.34.255.254121.34.255.25532,766
71121.35.0.0/17121.35.0.1 to 121.35.127.254121.35.127.25532,766
72121.35.128.0/17121.35.128.1 to 121.35.255.254121.35.255.25532,766
73121.36.0.0/17121.36.0.1 to 121.36.127.254121.36.127.25532,766
74121.36.128.0/17121.36.128.1 to 121.36.255.254121.36.255.25532,766
75121.37.0.0/17121.37.0.1 to 121.37.127.254121.37.127.25532,766
76121.37.128.0/17121.37.128.1 to 121.37.255.254121.37.255.25532,766
77121.38.0.0/17121.38.0.1 to 121.38.127.254121.38.127.25532,766
78121.38.128.0/17121.38.128.1 to 121.38.255.254121.38.255.25532,766
79121.39.0.0/17121.39.0.1 to 121.39.127.254121.39.127.25532,766
80121.39.128.0/17121.39.128.1 to 121.39.255.254121.39.255.25532,766
81121.40.0.0/17121.40.0.1 to 121.40.127.254121.40.127.25532,766
82121.40.128.0/17121.40.128.1 to 121.40.255.254121.40.255.25532,766
83121.41.0.0/17121.41.0.1 to 121.41.127.254121.41.127.25532,766
84121.41.128.0/17121.41.128.1 to 121.41.255.254121.41.255.25532,766
85121.42.0.0/17121.42.0.1 to 121.42.127.254121.42.127.25532,766
86121.42.128.0/17121.42.128.1 to 121.42.255.254121.42.255.25532,766
87121.43.0.0/17121.43.0.1 to 121.43.127.254121.43.127.25532,766
88121.43.128.0/17121.43.128.1 to 121.43.255.254121.43.255.25532,766
89121.44.0.0/17121.44.0.1 to 121.44.127.254121.44.127.25532,766
90121.44.128.0/17121.44.128.1 to 121.44.255.254121.44.255.25532,766
91121.45.0.0/17121.45.0.1 to 121.45.127.254121.45.127.25532,766
92121.45.128.0/17121.45.128.1 to 121.45.255.254121.45.255.25532,766
93121.46.0.0/17121.46.0.1 to 121.46.127.254121.46.127.25532,766
94121.46.128.0/17121.46.128.1 to 121.46.255.254121.46.255.25532,766
95121.47.0.0/17121.47.0.1 to 121.47.127.254121.47.127.25532,766
96121.47.128.0/17121.47.128.1 to 121.47.255.254121.47.255.25532,766
97121.48.0.0/17121.48.0.1 to 121.48.127.254121.48.127.25532,766
98121.48.128.0/17121.48.128.1 to 121.48.255.254121.48.255.25532,766
99121.49.0.0/17121.49.0.1 to 121.49.127.254121.49.127.25532,766
100121.49.128.0/17121.49.128.1 to 121.49.255.254121.49.255.25532,766
101121.50.0.0/17121.50.0.1 to 121.50.127.254121.50.127.25532,766
102121.50.128.0/17121.50.128.1 to 121.50.255.254121.50.255.25532,766
103121.51.0.0/17121.51.0.1 to 121.51.127.254121.51.127.25532,766
104121.51.128.0/17121.51.128.1 to 121.51.255.254121.51.255.25532,766
105121.52.0.0/17121.52.0.1 to 121.52.127.254121.52.127.25532,766
106121.52.128.0/17121.52.128.1 to 121.52.255.254121.52.255.25532,766
107121.53.0.0/17121.53.0.1 to 121.53.127.254121.53.127.25532,766
108121.53.128.0/17121.53.128.1 to 121.53.255.254121.53.255.25532,766
109121.54.0.0/17121.54.0.1 to 121.54.127.254121.54.127.25532,766
110121.54.128.0/17121.54.128.1 to 121.54.255.254121.54.255.25532,766
111121.55.0.0/17121.55.0.1 to 121.55.127.254121.55.127.25532,766
112121.55.128.0/17121.55.128.1 to 121.55.255.254121.55.255.25532,766
113121.56.0.0/17121.56.0.1 to 121.56.127.254121.56.127.25532,766
114121.56.128.0/17121.56.128.1 to 121.56.255.254121.56.255.25532,766
115121.57.0.0/17121.57.0.1 to 121.57.127.254121.57.127.25532,766
116121.57.128.0/17121.57.128.1 to 121.57.255.254121.57.255.25532,766
117121.58.0.0/17121.58.0.1 to 121.58.127.254121.58.127.25532,766
118121.58.128.0/17121.58.128.1 to 121.58.255.254121.58.255.25532,766
119121.59.0.0/17121.59.0.1 to 121.59.127.254121.59.127.25532,766
120121.59.128.0/17121.59.128.1 to 121.59.255.254121.59.255.25532,766
121121.60.0.0/17121.60.0.1 to 121.60.127.254121.60.127.25532,766
122121.60.128.0/17121.60.128.1 to 121.60.255.254121.60.255.25532,766
123121.61.0.0/17121.61.0.1 to 121.61.127.254121.61.127.25532,766
124121.61.128.0/17121.61.128.1 to 121.61.255.254121.61.255.25532,766
125121.62.0.0/17121.62.0.1 to 121.62.127.254121.62.127.25532,766
126121.62.128.0/17121.62.128.1 to 121.62.255.254121.62.255.25532,766
127121.63.0.0/17121.63.0.1 to 121.63.127.254121.63.127.25532,766
128121.63.128.0/17121.63.128.1 to 121.63.255.254121.63.255.25532,766
129121.64.0.0/17121.64.0.1 to 121.64.127.254121.64.127.25532,766
130121.64.128.0/17121.64.128.1 to 121.64.255.254121.64.255.25532,766
131121.65.0.0/17121.65.0.1 to 121.65.127.254121.65.127.25532,766
132121.65.128.0/17121.65.128.1 to 121.65.255.254121.65.255.25532,766
133121.66.0.0/17121.66.0.1 to 121.66.127.254121.66.127.25532,766
134121.66.128.0/17121.66.128.1 to 121.66.255.254121.66.255.25532,766
135121.67.0.0/17121.67.0.1 to 121.67.127.254121.67.127.25532,766
136121.67.128.0/17121.67.128.1 to 121.67.255.254121.67.255.25532,766
137121.68.0.0/17121.68.0.1 to 121.68.127.254121.68.127.25532,766
138121.68.128.0/17121.68.128.1 to 121.68.255.254121.68.255.25532,766
139121.69.0.0/17121.69.0.1 to 121.69.127.254121.69.127.25532,766
140121.69.128.0/17121.69.128.1 to 121.69.255.254121.69.255.25532,766
141121.70.0.0/17121.70.0.1 to 121.70.127.254121.70.127.25532,766
142121.70.128.0/17121.70.128.1 to 121.70.255.254121.70.255.25532,766
143121.71.0.0/17121.71.0.1 to 121.71.127.254121.71.127.25532,766
144121.71.128.0/17121.71.128.1 to 121.71.255.254121.71.255.25532,766
145121.72.0.0/17121.72.0.1 to 121.72.127.254121.72.127.25532,766
146121.72.128.0/17121.72.128.1 to 121.72.255.254121.72.255.25532,766
147121.73.0.0/17121.73.0.1 to 121.73.127.254121.73.127.25532,766
148121.73.128.0/17121.73.128.1 to 121.73.255.254121.73.255.25532,766
149121.74.0.0/17121.74.0.1 to 121.74.127.254121.74.127.25532,766
150121.74.128.0/17121.74.128.1 to 121.74.255.254121.74.255.25532,766
151121.75.0.0/17121.75.0.1 to 121.75.127.254121.75.127.25532,766
152121.75.128.0/17121.75.128.1 to 121.75.255.254121.75.255.25532,766
153121.76.0.0/17121.76.0.1 to 121.76.127.254121.76.127.25532,766
154121.76.128.0/17121.76.128.1 to 121.76.255.254121.76.255.25532,766
155121.77.0.0/17121.77.0.1 to 121.77.127.254121.77.127.25532,766
156121.77.128.0/17121.77.128.1 to 121.77.255.254121.77.255.25532,766
157121.78.0.0/17121.78.0.1 to 121.78.127.254121.78.127.25532,766
158121.78.128.0/17121.78.128.1 to 121.78.255.254121.78.255.25532,766
159121.79.0.0/17121.79.0.1 to 121.79.127.254121.79.127.25532,766
160121.79.128.0/17121.79.128.1 to 121.79.255.254121.79.255.25532,766
161121.80.0.0/17121.80.0.1 to 121.80.127.254121.80.127.25532,766
162121.80.128.0/17121.80.128.1 to 121.80.255.254121.80.255.25532,766
163121.81.0.0/17121.81.0.1 to 121.81.127.254121.81.127.25532,766
164121.81.128.0/17121.81.128.1 to 121.81.255.254121.81.255.25532,766
165121.82.0.0/17121.82.0.1 to 121.82.127.254121.82.127.25532,766
166121.82.128.0/17121.82.128.1 to 121.82.255.254121.82.255.25532,766
167121.83.0.0/17121.83.0.1 to 121.83.127.254121.83.127.25532,766
168121.83.128.0/17121.83.128.1 to 121.83.255.254121.83.255.25532,766
169121.84.0.0/17121.84.0.1 to 121.84.127.254121.84.127.25532,766
170121.84.128.0/17121.84.128.1 to 121.84.255.254121.84.255.25532,766
171121.85.0.0/17121.85.0.1 to 121.85.127.254121.85.127.25532,766
172121.85.128.0/17121.85.128.1 to 121.85.255.254121.85.255.25532,766
173121.86.0.0/17121.86.0.1 to 121.86.127.254121.86.127.25532,766
174121.86.128.0/17121.86.128.1 to 121.86.255.254121.86.255.25532,766
175121.87.0.0/17121.87.0.1 to 121.87.127.254121.87.127.25532,766
176121.87.128.0/17121.87.128.1 to 121.87.255.254121.87.255.25532,766
177121.88.0.0/17121.88.0.1 to 121.88.127.254121.88.127.25532,766
178121.88.128.0/17121.88.128.1 to 121.88.255.254121.88.255.25532,766
179121.89.0.0/17121.89.0.1 to 121.89.127.254121.89.127.25532,766
180121.89.128.0/17121.89.128.1 to 121.89.255.254121.89.255.25532,766
181121.90.0.0/17121.90.0.1 to 121.90.127.254121.90.127.25532,766
182121.90.128.0/17121.90.128.1 to 121.90.255.254121.90.255.25532,766
183121.91.0.0/17121.91.0.1 to 121.91.127.254121.91.127.25532,766
184121.91.128.0/17121.91.128.1 to 121.91.255.254121.91.255.25532,766
185121.92.0.0/17121.92.0.1 to 121.92.127.254121.92.127.25532,766
186121.92.128.0/17121.92.128.1 to 121.92.255.254121.92.255.25532,766
187121.93.0.0/17121.93.0.1 to 121.93.127.254121.93.127.25532,766
188121.93.128.0/17121.93.128.1 to 121.93.255.254121.93.255.25532,766
189121.94.0.0/17121.94.0.1 to 121.94.127.254121.94.127.25532,766
190121.94.128.0/17121.94.128.1 to 121.94.255.254121.94.255.25532,766
191121.95.0.0/17121.95.0.1 to 121.95.127.254121.95.127.25532,766
192121.95.128.0/17121.95.128.1 to 121.95.255.254121.95.255.25532,766
193121.96.0.0/17121.96.0.1 to 121.96.127.254121.96.127.25532,766
194121.96.128.0/17121.96.128.1 to 121.96.255.254121.96.255.25532,766
195121.97.0.0/17121.97.0.1 to 121.97.127.254121.97.127.25532,766
196121.97.128.0/17121.97.128.1 to 121.97.255.254121.97.255.25532,766
197121.98.0.0/17121.98.0.1 to 121.98.127.254121.98.127.25532,766
198121.98.128.0/17121.98.128.1 to 121.98.255.254121.98.255.25532,766
199121.99.0.0/17121.99.0.1 to 121.99.127.254121.99.127.25532,766
200121.99.128.0/17121.99.128.1 to 121.99.255.254121.99.255.25532,766
201121.100.0.0/17121.100.0.1 to 121.100.127.254121.100.127.25532,766
202121.100.128.0/17121.100.128.1 to 121.100.255.254121.100.255.25532,766
203121.101.0.0/17121.101.0.1 to 121.101.127.254121.101.127.25532,766
204121.101.128.0/17121.101.128.1 to 121.101.255.254121.101.255.25532,766
205121.102.0.0/17121.102.0.1 to 121.102.127.254121.102.127.25532,766
206121.102.128.0/17121.102.128.1 to 121.102.255.254121.102.255.25532,766
207121.103.0.0/17121.103.0.1 to 121.103.127.254121.103.127.25532,766
208121.103.128.0/17121.103.128.1 to 121.103.255.254121.103.255.25532,766
209121.104.0.0/17121.104.0.1 to 121.104.127.254121.104.127.25532,766
210121.104.128.0/17121.104.128.1 to 121.104.255.254121.104.255.25532,766
211121.105.0.0/17121.105.0.1 to 121.105.127.254121.105.127.25532,766
212121.105.128.0/17121.105.128.1 to 121.105.255.254121.105.255.25532,766
213121.106.0.0/17121.106.0.1 to 121.106.127.254121.106.127.25532,766
214121.106.128.0/17121.106.128.1 to 121.106.255.254121.106.255.25532,766
215121.107.0.0/17121.107.0.1 to 121.107.127.254121.107.127.25532,766
216121.107.128.0/17121.107.128.1 to 121.107.255.254121.107.255.25532,766
217121.108.0.0/17121.108.0.1 to 121.108.127.254121.108.127.25532,766
218121.108.128.0/17121.108.128.1 to 121.108.255.254121.108.255.25532,766
219121.109.0.0/17121.109.0.1 to 121.109.127.254121.109.127.25532,766
220121.109.128.0/17121.109.128.1 to 121.109.255.254121.109.255.25532,766
221121.110.0.0/17121.110.0.1 to 121.110.127.254121.110.127.25532,766
222121.110.128.0/17121.110.128.1 to 121.110.255.254121.110.255.25532,766
223121.111.0.0/17121.111.0.1 to 121.111.127.254121.111.127.25532,766
224121.111.128.0/17121.111.128.1 to 121.111.255.254121.111.255.25532,766
225121.112.0.0/17121.112.0.1 to 121.112.127.254121.112.127.25532,766
226121.112.128.0/17121.112.128.1 to 121.112.255.254121.112.255.25532,766
227121.113.0.0/17121.113.0.1 to 121.113.127.254121.113.127.25532,766
228121.113.128.0/17121.113.128.1 to 121.113.255.254121.113.255.25532,766
229121.114.0.0/17121.114.0.1 to 121.114.127.254121.114.127.25532,766
230121.114.128.0/17121.114.128.1 to 121.114.255.254121.114.255.25532,766
231121.115.0.0/17121.115.0.1 to 121.115.127.254121.115.127.25532,766
232121.115.128.0/17121.115.128.1 to 121.115.255.254121.115.255.25532,766
233121.116.0.0/17121.116.0.1 to 121.116.127.254121.116.127.25532,766
234121.116.128.0/17121.116.128.1 to 121.116.255.254121.116.255.25532,766
235121.117.0.0/17121.117.0.1 to 121.117.127.254121.117.127.25532,766
236121.117.128.0/17121.117.128.1 to 121.117.255.254121.117.255.25532,766
237121.118.0.0/17121.118.0.1 to 121.118.127.254121.118.127.25532,766
238121.118.128.0/17121.118.128.1 to 121.118.255.254121.118.255.25532,766
239121.119.0.0/17121.119.0.1 to 121.119.127.254121.119.127.25532,766
240121.119.128.0/17121.119.128.1 to 121.119.255.254121.119.255.25532,766
241121.120.0.0/17121.120.0.1 to 121.120.127.254121.120.127.25532,766
242121.120.128.0/17121.120.128.1 to 121.120.255.254121.120.255.25532,766
243121.121.0.0/17121.121.0.1 to 121.121.127.254121.121.127.25532,766
244121.121.128.0/17121.121.128.1 to 121.121.255.254121.121.255.25532,766
245121.122.0.0/17121.122.0.1 to 121.122.127.254121.122.127.25532,766
246121.122.128.0/17121.122.128.1 to 121.122.255.254121.122.255.25532,766
247121.123.0.0/17121.123.0.1 to 121.123.127.254121.123.127.25532,766
248121.123.128.0/17121.123.128.1 to 121.123.255.254121.123.255.25532,766
249121.124.0.0/17121.124.0.1 to 121.124.127.254121.124.127.25532,766
250121.124.128.0/17121.124.128.1 to 121.124.255.254121.124.255.25532,766
251121.125.0.0/17121.125.0.1 to 121.125.127.254121.125.127.25532,766
252121.125.128.0/17121.125.128.1 to 121.125.255.254121.125.255.25532,766
253121.126.0.0/17121.126.0.1 to 121.126.127.254121.126.127.25532,766
254121.126.128.0/17121.126.128.1 to 121.126.255.254121.126.255.25532,766
255121.127.0.0/17121.127.0.1 to 121.127.127.254121.127.127.25532,766
256121.127.128.0/17121.127.128.1 to 121.127.255.254121.127.255.25532,766

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.