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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/18
/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 512 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1121.0.0.0/18121.0.0.1 to 121.0.63.254121.0.63.25516,382
2121.0.64.0/18121.0.64.1 to 121.0.127.254121.0.127.25516,382
3121.0.128.0/18121.0.128.1 to 121.0.191.254121.0.191.25516,382
4121.0.192.0/18121.0.192.1 to 121.0.255.254121.0.255.25516,382
5121.1.0.0/18121.1.0.1 to 121.1.63.254121.1.63.25516,382
6121.1.64.0/18121.1.64.1 to 121.1.127.254121.1.127.25516,382
7121.1.128.0/18121.1.128.1 to 121.1.191.254121.1.191.25516,382
8121.1.192.0/18121.1.192.1 to 121.1.255.254121.1.255.25516,382
9121.2.0.0/18121.2.0.1 to 121.2.63.254121.2.63.25516,382
10121.2.64.0/18121.2.64.1 to 121.2.127.254121.2.127.25516,382
11121.2.128.0/18121.2.128.1 to 121.2.191.254121.2.191.25516,382
12121.2.192.0/18121.2.192.1 to 121.2.255.254121.2.255.25516,382
13121.3.0.0/18121.3.0.1 to 121.3.63.254121.3.63.25516,382
14121.3.64.0/18121.3.64.1 to 121.3.127.254121.3.127.25516,382
15121.3.128.0/18121.3.128.1 to 121.3.191.254121.3.191.25516,382
16121.3.192.0/18121.3.192.1 to 121.3.255.254121.3.255.25516,382
17121.4.0.0/18121.4.0.1 to 121.4.63.254121.4.63.25516,382
18121.4.64.0/18121.4.64.1 to 121.4.127.254121.4.127.25516,382
19121.4.128.0/18121.4.128.1 to 121.4.191.254121.4.191.25516,382
20121.4.192.0/18121.4.192.1 to 121.4.255.254121.4.255.25516,382
21121.5.0.0/18121.5.0.1 to 121.5.63.254121.5.63.25516,382
22121.5.64.0/18121.5.64.1 to 121.5.127.254121.5.127.25516,382
23121.5.128.0/18121.5.128.1 to 121.5.191.254121.5.191.25516,382
24121.5.192.0/18121.5.192.1 to 121.5.255.254121.5.255.25516,382
25121.6.0.0/18121.6.0.1 to 121.6.63.254121.6.63.25516,382
26121.6.64.0/18121.6.64.1 to 121.6.127.254121.6.127.25516,382
27121.6.128.0/18121.6.128.1 to 121.6.191.254121.6.191.25516,382
28121.6.192.0/18121.6.192.1 to 121.6.255.254121.6.255.25516,382
29121.7.0.0/18121.7.0.1 to 121.7.63.254121.7.63.25516,382
30121.7.64.0/18121.7.64.1 to 121.7.127.254121.7.127.25516,382
31121.7.128.0/18121.7.128.1 to 121.7.191.254121.7.191.25516,382
32121.7.192.0/18121.7.192.1 to 121.7.255.254121.7.255.25516,382
33121.8.0.0/18121.8.0.1 to 121.8.63.254121.8.63.25516,382
34121.8.64.0/18121.8.64.1 to 121.8.127.254121.8.127.25516,382
35121.8.128.0/18121.8.128.1 to 121.8.191.254121.8.191.25516,382
36121.8.192.0/18121.8.192.1 to 121.8.255.254121.8.255.25516,382
37121.9.0.0/18121.9.0.1 to 121.9.63.254121.9.63.25516,382
38121.9.64.0/18121.9.64.1 to 121.9.127.254121.9.127.25516,382
39121.9.128.0/18121.9.128.1 to 121.9.191.254121.9.191.25516,382
40121.9.192.0/18121.9.192.1 to 121.9.255.254121.9.255.25516,382
41121.10.0.0/18121.10.0.1 to 121.10.63.254121.10.63.25516,382
42121.10.64.0/18121.10.64.1 to 121.10.127.254121.10.127.25516,382
43121.10.128.0/18121.10.128.1 to 121.10.191.254121.10.191.25516,382
44121.10.192.0/18121.10.192.1 to 121.10.255.254121.10.255.25516,382
45121.11.0.0/18121.11.0.1 to 121.11.63.254121.11.63.25516,382
46121.11.64.0/18121.11.64.1 to 121.11.127.254121.11.127.25516,382
47121.11.128.0/18121.11.128.1 to 121.11.191.254121.11.191.25516,382
48121.11.192.0/18121.11.192.1 to 121.11.255.254121.11.255.25516,382
49121.12.0.0/18121.12.0.1 to 121.12.63.254121.12.63.25516,382
50121.12.64.0/18121.12.64.1 to 121.12.127.254121.12.127.25516,382
51121.12.128.0/18121.12.128.1 to 121.12.191.254121.12.191.25516,382
52121.12.192.0/18121.12.192.1 to 121.12.255.254121.12.255.25516,382
53121.13.0.0/18121.13.0.1 to 121.13.63.254121.13.63.25516,382
54121.13.64.0/18121.13.64.1 to 121.13.127.254121.13.127.25516,382
55121.13.128.0/18121.13.128.1 to 121.13.191.254121.13.191.25516,382
56121.13.192.0/18121.13.192.1 to 121.13.255.254121.13.255.25516,382
57121.14.0.0/18121.14.0.1 to 121.14.63.254121.14.63.25516,382
58121.14.64.0/18121.14.64.1 to 121.14.127.254121.14.127.25516,382
59121.14.128.0/18121.14.128.1 to 121.14.191.254121.14.191.25516,382
60121.14.192.0/18121.14.192.1 to 121.14.255.254121.14.255.25516,382
61121.15.0.0/18121.15.0.1 to 121.15.63.254121.15.63.25516,382
62121.15.64.0/18121.15.64.1 to 121.15.127.254121.15.127.25516,382
63121.15.128.0/18121.15.128.1 to 121.15.191.254121.15.191.25516,382
64121.15.192.0/18121.15.192.1 to 121.15.255.254121.15.255.25516,382
65121.16.0.0/18121.16.0.1 to 121.16.63.254121.16.63.25516,382
66121.16.64.0/18121.16.64.1 to 121.16.127.254121.16.127.25516,382
67121.16.128.0/18121.16.128.1 to 121.16.191.254121.16.191.25516,382
68121.16.192.0/18121.16.192.1 to 121.16.255.254121.16.255.25516,382
69121.17.0.0/18121.17.0.1 to 121.17.63.254121.17.63.25516,382
70121.17.64.0/18121.17.64.1 to 121.17.127.254121.17.127.25516,382
71121.17.128.0/18121.17.128.1 to 121.17.191.254121.17.191.25516,382
72121.17.192.0/18121.17.192.1 to 121.17.255.254121.17.255.25516,382
73121.18.0.0/18121.18.0.1 to 121.18.63.254121.18.63.25516,382
74121.18.64.0/18121.18.64.1 to 121.18.127.254121.18.127.25516,382
75121.18.128.0/18121.18.128.1 to 121.18.191.254121.18.191.25516,382
76121.18.192.0/18121.18.192.1 to 121.18.255.254121.18.255.25516,382
77121.19.0.0/18121.19.0.1 to 121.19.63.254121.19.63.25516,382
78121.19.64.0/18121.19.64.1 to 121.19.127.254121.19.127.25516,382
79121.19.128.0/18121.19.128.1 to 121.19.191.254121.19.191.25516,382
80121.19.192.0/18121.19.192.1 to 121.19.255.254121.19.255.25516,382
81121.20.0.0/18121.20.0.1 to 121.20.63.254121.20.63.25516,382
82121.20.64.0/18121.20.64.1 to 121.20.127.254121.20.127.25516,382
83121.20.128.0/18121.20.128.1 to 121.20.191.254121.20.191.25516,382
84121.20.192.0/18121.20.192.1 to 121.20.255.254121.20.255.25516,382
85121.21.0.0/18121.21.0.1 to 121.21.63.254121.21.63.25516,382
86121.21.64.0/18121.21.64.1 to 121.21.127.254121.21.127.25516,382
87121.21.128.0/18121.21.128.1 to 121.21.191.254121.21.191.25516,382
88121.21.192.0/18121.21.192.1 to 121.21.255.254121.21.255.25516,382
89121.22.0.0/18121.22.0.1 to 121.22.63.254121.22.63.25516,382
90121.22.64.0/18121.22.64.1 to 121.22.127.254121.22.127.25516,382
91121.22.128.0/18121.22.128.1 to 121.22.191.254121.22.191.25516,382
92121.22.192.0/18121.22.192.1 to 121.22.255.254121.22.255.25516,382
93121.23.0.0/18121.23.0.1 to 121.23.63.254121.23.63.25516,382
94121.23.64.0/18121.23.64.1 to 121.23.127.254121.23.127.25516,382
95121.23.128.0/18121.23.128.1 to 121.23.191.254121.23.191.25516,382
96121.23.192.0/18121.23.192.1 to 121.23.255.254121.23.255.25516,382
97121.24.0.0/18121.24.0.1 to 121.24.63.254121.24.63.25516,382
98121.24.64.0/18121.24.64.1 to 121.24.127.254121.24.127.25516,382
99121.24.128.0/18121.24.128.1 to 121.24.191.254121.24.191.25516,382
100121.24.192.0/18121.24.192.1 to 121.24.255.254121.24.255.25516,382
101121.25.0.0/18121.25.0.1 to 121.25.63.254121.25.63.25516,382
102121.25.64.0/18121.25.64.1 to 121.25.127.254121.25.127.25516,382
103121.25.128.0/18121.25.128.1 to 121.25.191.254121.25.191.25516,382
104121.25.192.0/18121.25.192.1 to 121.25.255.254121.25.255.25516,382
105121.26.0.0/18121.26.0.1 to 121.26.63.254121.26.63.25516,382
106121.26.64.0/18121.26.64.1 to 121.26.127.254121.26.127.25516,382
107121.26.128.0/18121.26.128.1 to 121.26.191.254121.26.191.25516,382
108121.26.192.0/18121.26.192.1 to 121.26.255.254121.26.255.25516,382
109121.27.0.0/18121.27.0.1 to 121.27.63.254121.27.63.25516,382
110121.27.64.0/18121.27.64.1 to 121.27.127.254121.27.127.25516,382
111121.27.128.0/18121.27.128.1 to 121.27.191.254121.27.191.25516,382
112121.27.192.0/18121.27.192.1 to 121.27.255.254121.27.255.25516,382
113121.28.0.0/18121.28.0.1 to 121.28.63.254121.28.63.25516,382
114121.28.64.0/18121.28.64.1 to 121.28.127.254121.28.127.25516,382
115121.28.128.0/18121.28.128.1 to 121.28.191.254121.28.191.25516,382
116121.28.192.0/18121.28.192.1 to 121.28.255.254121.28.255.25516,382
117121.29.0.0/18121.29.0.1 to 121.29.63.254121.29.63.25516,382
118121.29.64.0/18121.29.64.1 to 121.29.127.254121.29.127.25516,382
119121.29.128.0/18121.29.128.1 to 121.29.191.254121.29.191.25516,382
120121.29.192.0/18121.29.192.1 to 121.29.255.254121.29.255.25516,382
121121.30.0.0/18121.30.0.1 to 121.30.63.254121.30.63.25516,382
122121.30.64.0/18121.30.64.1 to 121.30.127.254121.30.127.25516,382
123121.30.128.0/18121.30.128.1 to 121.30.191.254121.30.191.25516,382
124121.30.192.0/18121.30.192.1 to 121.30.255.254121.30.255.25516,382
125121.31.0.0/18121.31.0.1 to 121.31.63.254121.31.63.25516,382
126121.31.64.0/18121.31.64.1 to 121.31.127.254121.31.127.25516,382
127121.31.128.0/18121.31.128.1 to 121.31.191.254121.31.191.25516,382
128121.31.192.0/18121.31.192.1 to 121.31.255.254121.31.255.25516,382
129121.32.0.0/18121.32.0.1 to 121.32.63.254121.32.63.25516,382
130121.32.64.0/18121.32.64.1 to 121.32.127.254121.32.127.25516,382
131121.32.128.0/18121.32.128.1 to 121.32.191.254121.32.191.25516,382
132121.32.192.0/18121.32.192.1 to 121.32.255.254121.32.255.25516,382
133121.33.0.0/18121.33.0.1 to 121.33.63.254121.33.63.25516,382
134121.33.64.0/18121.33.64.1 to 121.33.127.254121.33.127.25516,382
135121.33.128.0/18121.33.128.1 to 121.33.191.254121.33.191.25516,382
136121.33.192.0/18121.33.192.1 to 121.33.255.254121.33.255.25516,382
137121.34.0.0/18121.34.0.1 to 121.34.63.254121.34.63.25516,382
138121.34.64.0/18121.34.64.1 to 121.34.127.254121.34.127.25516,382
139121.34.128.0/18121.34.128.1 to 121.34.191.254121.34.191.25516,382
140121.34.192.0/18121.34.192.1 to 121.34.255.254121.34.255.25516,382
141121.35.0.0/18121.35.0.1 to 121.35.63.254121.35.63.25516,382
142121.35.64.0/18121.35.64.1 to 121.35.127.254121.35.127.25516,382
143121.35.128.0/18121.35.128.1 to 121.35.191.254121.35.191.25516,382
144121.35.192.0/18121.35.192.1 to 121.35.255.254121.35.255.25516,382
145121.36.0.0/18121.36.0.1 to 121.36.63.254121.36.63.25516,382
146121.36.64.0/18121.36.64.1 to 121.36.127.254121.36.127.25516,382
147121.36.128.0/18121.36.128.1 to 121.36.191.254121.36.191.25516,382
148121.36.192.0/18121.36.192.1 to 121.36.255.254121.36.255.25516,382
149121.37.0.0/18121.37.0.1 to 121.37.63.254121.37.63.25516,382
150121.37.64.0/18121.37.64.1 to 121.37.127.254121.37.127.25516,382
151121.37.128.0/18121.37.128.1 to 121.37.191.254121.37.191.25516,382
152121.37.192.0/18121.37.192.1 to 121.37.255.254121.37.255.25516,382
153121.38.0.0/18121.38.0.1 to 121.38.63.254121.38.63.25516,382
154121.38.64.0/18121.38.64.1 to 121.38.127.254121.38.127.25516,382
155121.38.128.0/18121.38.128.1 to 121.38.191.254121.38.191.25516,382
156121.38.192.0/18121.38.192.1 to 121.38.255.254121.38.255.25516,382
157121.39.0.0/18121.39.0.1 to 121.39.63.254121.39.63.25516,382
158121.39.64.0/18121.39.64.1 to 121.39.127.254121.39.127.25516,382
159121.39.128.0/18121.39.128.1 to 121.39.191.254121.39.191.25516,382
160121.39.192.0/18121.39.192.1 to 121.39.255.254121.39.255.25516,382
161121.40.0.0/18121.40.0.1 to 121.40.63.254121.40.63.25516,382
162121.40.64.0/18121.40.64.1 to 121.40.127.254121.40.127.25516,382
163121.40.128.0/18121.40.128.1 to 121.40.191.254121.40.191.25516,382
164121.40.192.0/18121.40.192.1 to 121.40.255.254121.40.255.25516,382
165121.41.0.0/18121.41.0.1 to 121.41.63.254121.41.63.25516,382
166121.41.64.0/18121.41.64.1 to 121.41.127.254121.41.127.25516,382
167121.41.128.0/18121.41.128.1 to 121.41.191.254121.41.191.25516,382
168121.41.192.0/18121.41.192.1 to 121.41.255.254121.41.255.25516,382
169121.42.0.0/18121.42.0.1 to 121.42.63.254121.42.63.25516,382
170121.42.64.0/18121.42.64.1 to 121.42.127.254121.42.127.25516,382
171121.42.128.0/18121.42.128.1 to 121.42.191.254121.42.191.25516,382
172121.42.192.0/18121.42.192.1 to 121.42.255.254121.42.255.25516,382
173121.43.0.0/18121.43.0.1 to 121.43.63.254121.43.63.25516,382
174121.43.64.0/18121.43.64.1 to 121.43.127.254121.43.127.25516,382
175121.43.128.0/18121.43.128.1 to 121.43.191.254121.43.191.25516,382
176121.43.192.0/18121.43.192.1 to 121.43.255.254121.43.255.25516,382
177121.44.0.0/18121.44.0.1 to 121.44.63.254121.44.63.25516,382
178121.44.64.0/18121.44.64.1 to 121.44.127.254121.44.127.25516,382
179121.44.128.0/18121.44.128.1 to 121.44.191.254121.44.191.25516,382
180121.44.192.0/18121.44.192.1 to 121.44.255.254121.44.255.25516,382
181121.45.0.0/18121.45.0.1 to 121.45.63.254121.45.63.25516,382
182121.45.64.0/18121.45.64.1 to 121.45.127.254121.45.127.25516,382
183121.45.128.0/18121.45.128.1 to 121.45.191.254121.45.191.25516,382
184121.45.192.0/18121.45.192.1 to 121.45.255.254121.45.255.25516,382
185121.46.0.0/18121.46.0.1 to 121.46.63.254121.46.63.25516,382
186121.46.64.0/18121.46.64.1 to 121.46.127.254121.46.127.25516,382
187121.46.128.0/18121.46.128.1 to 121.46.191.254121.46.191.25516,382
188121.46.192.0/18121.46.192.1 to 121.46.255.254121.46.255.25516,382
189121.47.0.0/18121.47.0.1 to 121.47.63.254121.47.63.25516,382
190121.47.64.0/18121.47.64.1 to 121.47.127.254121.47.127.25516,382
191121.47.128.0/18121.47.128.1 to 121.47.191.254121.47.191.25516,382
192121.47.192.0/18121.47.192.1 to 121.47.255.254121.47.255.25516,382
193121.48.0.0/18121.48.0.1 to 121.48.63.254121.48.63.25516,382
194121.48.64.0/18121.48.64.1 to 121.48.127.254121.48.127.25516,382
195121.48.128.0/18121.48.128.1 to 121.48.191.254121.48.191.25516,382
196121.48.192.0/18121.48.192.1 to 121.48.255.254121.48.255.25516,382
197121.49.0.0/18121.49.0.1 to 121.49.63.254121.49.63.25516,382
198121.49.64.0/18121.49.64.1 to 121.49.127.254121.49.127.25516,382
199121.49.128.0/18121.49.128.1 to 121.49.191.254121.49.191.25516,382
200121.49.192.0/18121.49.192.1 to 121.49.255.254121.49.255.25516,382
201121.50.0.0/18121.50.0.1 to 121.50.63.254121.50.63.25516,382
202121.50.64.0/18121.50.64.1 to 121.50.127.254121.50.127.25516,382
203121.50.128.0/18121.50.128.1 to 121.50.191.254121.50.191.25516,382
204121.50.192.0/18121.50.192.1 to 121.50.255.254121.50.255.25516,382
205121.51.0.0/18121.51.0.1 to 121.51.63.254121.51.63.25516,382
206121.51.64.0/18121.51.64.1 to 121.51.127.254121.51.127.25516,382
207121.51.128.0/18121.51.128.1 to 121.51.191.254121.51.191.25516,382
208121.51.192.0/18121.51.192.1 to 121.51.255.254121.51.255.25516,382
209121.52.0.0/18121.52.0.1 to 121.52.63.254121.52.63.25516,382
210121.52.64.0/18121.52.64.1 to 121.52.127.254121.52.127.25516,382
211121.52.128.0/18121.52.128.1 to 121.52.191.254121.52.191.25516,382
212121.52.192.0/18121.52.192.1 to 121.52.255.254121.52.255.25516,382
213121.53.0.0/18121.53.0.1 to 121.53.63.254121.53.63.25516,382
214121.53.64.0/18121.53.64.1 to 121.53.127.254121.53.127.25516,382
215121.53.128.0/18121.53.128.1 to 121.53.191.254121.53.191.25516,382
216121.53.192.0/18121.53.192.1 to 121.53.255.254121.53.255.25516,382
217121.54.0.0/18121.54.0.1 to 121.54.63.254121.54.63.25516,382
218121.54.64.0/18121.54.64.1 to 121.54.127.254121.54.127.25516,382
219121.54.128.0/18121.54.128.1 to 121.54.191.254121.54.191.25516,382
220121.54.192.0/18121.54.192.1 to 121.54.255.254121.54.255.25516,382
221121.55.0.0/18121.55.0.1 to 121.55.63.254121.55.63.25516,382
222121.55.64.0/18121.55.64.1 to 121.55.127.254121.55.127.25516,382
223121.55.128.0/18121.55.128.1 to 121.55.191.254121.55.191.25516,382
224121.55.192.0/18121.55.192.1 to 121.55.255.254121.55.255.25516,382
225121.56.0.0/18121.56.0.1 to 121.56.63.254121.56.63.25516,382
226121.56.64.0/18121.56.64.1 to 121.56.127.254121.56.127.25516,382
227121.56.128.0/18121.56.128.1 to 121.56.191.254121.56.191.25516,382
228121.56.192.0/18121.56.192.1 to 121.56.255.254121.56.255.25516,382
229121.57.0.0/18121.57.0.1 to 121.57.63.254121.57.63.25516,382
230121.57.64.0/18121.57.64.1 to 121.57.127.254121.57.127.25516,382
231121.57.128.0/18121.57.128.1 to 121.57.191.254121.57.191.25516,382
232121.57.192.0/18121.57.192.1 to 121.57.255.254121.57.255.25516,382
233121.58.0.0/18121.58.0.1 to 121.58.63.254121.58.63.25516,382
234121.58.64.0/18121.58.64.1 to 121.58.127.254121.58.127.25516,382
235121.58.128.0/18121.58.128.1 to 121.58.191.254121.58.191.25516,382
236121.58.192.0/18121.58.192.1 to 121.58.255.254121.58.255.25516,382
237121.59.0.0/18121.59.0.1 to 121.59.63.254121.59.63.25516,382
238121.59.64.0/18121.59.64.1 to 121.59.127.254121.59.127.25516,382
239121.59.128.0/18121.59.128.1 to 121.59.191.254121.59.191.25516,382
240121.59.192.0/18121.59.192.1 to 121.59.255.254121.59.255.25516,382
241121.60.0.0/18121.60.0.1 to 121.60.63.254121.60.63.25516,382
242121.60.64.0/18121.60.64.1 to 121.60.127.254121.60.127.25516,382
243121.60.128.0/18121.60.128.1 to 121.60.191.254121.60.191.25516,382
244121.60.192.0/18121.60.192.1 to 121.60.255.254121.60.255.25516,382
245121.61.0.0/18121.61.0.1 to 121.61.63.254121.61.63.25516,382
246121.61.64.0/18121.61.64.1 to 121.61.127.254121.61.127.25516,382
247121.61.128.0/18121.61.128.1 to 121.61.191.254121.61.191.25516,382
248121.61.192.0/18121.61.192.1 to 121.61.255.254121.61.255.25516,382
249121.62.0.0/18121.62.0.1 to 121.62.63.254121.62.63.25516,382
250121.62.64.0/18121.62.64.1 to 121.62.127.254121.62.127.25516,382
251121.62.128.0/18121.62.128.1 to 121.62.191.254121.62.191.25516,382
252121.62.192.0/18121.62.192.1 to 121.62.255.254121.62.255.25516,382
253121.63.0.0/18121.63.0.1 to 121.63.63.254121.63.63.25516,382
254121.63.64.0/18121.63.64.1 to 121.63.127.254121.63.127.25516,382
255121.63.128.0/18121.63.128.1 to 121.63.191.254121.63.191.25516,382
256121.63.192.0/18121.63.192.1 to 121.63.255.254121.63.255.25516,382

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.