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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/19
/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 1,024 subnets of /19; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1121.0.0.0/19121.0.0.1 to 121.0.31.254121.0.31.2558,190
2121.0.32.0/19121.0.32.1 to 121.0.63.254121.0.63.2558,190
3121.0.64.0/19121.0.64.1 to 121.0.95.254121.0.95.2558,190
4121.0.96.0/19121.0.96.1 to 121.0.127.254121.0.127.2558,190
5121.0.128.0/19121.0.128.1 to 121.0.159.254121.0.159.2558,190
6121.0.160.0/19121.0.160.1 to 121.0.191.254121.0.191.2558,190
7121.0.192.0/19121.0.192.1 to 121.0.223.254121.0.223.2558,190
8121.0.224.0/19121.0.224.1 to 121.0.255.254121.0.255.2558,190
9121.1.0.0/19121.1.0.1 to 121.1.31.254121.1.31.2558,190
10121.1.32.0/19121.1.32.1 to 121.1.63.254121.1.63.2558,190
11121.1.64.0/19121.1.64.1 to 121.1.95.254121.1.95.2558,190
12121.1.96.0/19121.1.96.1 to 121.1.127.254121.1.127.2558,190
13121.1.128.0/19121.1.128.1 to 121.1.159.254121.1.159.2558,190
14121.1.160.0/19121.1.160.1 to 121.1.191.254121.1.191.2558,190
15121.1.192.0/19121.1.192.1 to 121.1.223.254121.1.223.2558,190
16121.1.224.0/19121.1.224.1 to 121.1.255.254121.1.255.2558,190
17121.2.0.0/19121.2.0.1 to 121.2.31.254121.2.31.2558,190
18121.2.32.0/19121.2.32.1 to 121.2.63.254121.2.63.2558,190
19121.2.64.0/19121.2.64.1 to 121.2.95.254121.2.95.2558,190
20121.2.96.0/19121.2.96.1 to 121.2.127.254121.2.127.2558,190
21121.2.128.0/19121.2.128.1 to 121.2.159.254121.2.159.2558,190
22121.2.160.0/19121.2.160.1 to 121.2.191.254121.2.191.2558,190
23121.2.192.0/19121.2.192.1 to 121.2.223.254121.2.223.2558,190
24121.2.224.0/19121.2.224.1 to 121.2.255.254121.2.255.2558,190
25121.3.0.0/19121.3.0.1 to 121.3.31.254121.3.31.2558,190
26121.3.32.0/19121.3.32.1 to 121.3.63.254121.3.63.2558,190
27121.3.64.0/19121.3.64.1 to 121.3.95.254121.3.95.2558,190
28121.3.96.0/19121.3.96.1 to 121.3.127.254121.3.127.2558,190
29121.3.128.0/19121.3.128.1 to 121.3.159.254121.3.159.2558,190
30121.3.160.0/19121.3.160.1 to 121.3.191.254121.3.191.2558,190
31121.3.192.0/19121.3.192.1 to 121.3.223.254121.3.223.2558,190
32121.3.224.0/19121.3.224.1 to 121.3.255.254121.3.255.2558,190
33121.4.0.0/19121.4.0.1 to 121.4.31.254121.4.31.2558,190
34121.4.32.0/19121.4.32.1 to 121.4.63.254121.4.63.2558,190
35121.4.64.0/19121.4.64.1 to 121.4.95.254121.4.95.2558,190
36121.4.96.0/19121.4.96.1 to 121.4.127.254121.4.127.2558,190
37121.4.128.0/19121.4.128.1 to 121.4.159.254121.4.159.2558,190
38121.4.160.0/19121.4.160.1 to 121.4.191.254121.4.191.2558,190
39121.4.192.0/19121.4.192.1 to 121.4.223.254121.4.223.2558,190
40121.4.224.0/19121.4.224.1 to 121.4.255.254121.4.255.2558,190
41121.5.0.0/19121.5.0.1 to 121.5.31.254121.5.31.2558,190
42121.5.32.0/19121.5.32.1 to 121.5.63.254121.5.63.2558,190
43121.5.64.0/19121.5.64.1 to 121.5.95.254121.5.95.2558,190
44121.5.96.0/19121.5.96.1 to 121.5.127.254121.5.127.2558,190
45121.5.128.0/19121.5.128.1 to 121.5.159.254121.5.159.2558,190
46121.5.160.0/19121.5.160.1 to 121.5.191.254121.5.191.2558,190
47121.5.192.0/19121.5.192.1 to 121.5.223.254121.5.223.2558,190
48121.5.224.0/19121.5.224.1 to 121.5.255.254121.5.255.2558,190
49121.6.0.0/19121.6.0.1 to 121.6.31.254121.6.31.2558,190
50121.6.32.0/19121.6.32.1 to 121.6.63.254121.6.63.2558,190
51121.6.64.0/19121.6.64.1 to 121.6.95.254121.6.95.2558,190
52121.6.96.0/19121.6.96.1 to 121.6.127.254121.6.127.2558,190
53121.6.128.0/19121.6.128.1 to 121.6.159.254121.6.159.2558,190
54121.6.160.0/19121.6.160.1 to 121.6.191.254121.6.191.2558,190
55121.6.192.0/19121.6.192.1 to 121.6.223.254121.6.223.2558,190
56121.6.224.0/19121.6.224.1 to 121.6.255.254121.6.255.2558,190
57121.7.0.0/19121.7.0.1 to 121.7.31.254121.7.31.2558,190
58121.7.32.0/19121.7.32.1 to 121.7.63.254121.7.63.2558,190
59121.7.64.0/19121.7.64.1 to 121.7.95.254121.7.95.2558,190
60121.7.96.0/19121.7.96.1 to 121.7.127.254121.7.127.2558,190
61121.7.128.0/19121.7.128.1 to 121.7.159.254121.7.159.2558,190
62121.7.160.0/19121.7.160.1 to 121.7.191.254121.7.191.2558,190
63121.7.192.0/19121.7.192.1 to 121.7.223.254121.7.223.2558,190
64121.7.224.0/19121.7.224.1 to 121.7.255.254121.7.255.2558,190
65121.8.0.0/19121.8.0.1 to 121.8.31.254121.8.31.2558,190
66121.8.32.0/19121.8.32.1 to 121.8.63.254121.8.63.2558,190
67121.8.64.0/19121.8.64.1 to 121.8.95.254121.8.95.2558,190
68121.8.96.0/19121.8.96.1 to 121.8.127.254121.8.127.2558,190
69121.8.128.0/19121.8.128.1 to 121.8.159.254121.8.159.2558,190
70121.8.160.0/19121.8.160.1 to 121.8.191.254121.8.191.2558,190
71121.8.192.0/19121.8.192.1 to 121.8.223.254121.8.223.2558,190
72121.8.224.0/19121.8.224.1 to 121.8.255.254121.8.255.2558,190
73121.9.0.0/19121.9.0.1 to 121.9.31.254121.9.31.2558,190
74121.9.32.0/19121.9.32.1 to 121.9.63.254121.9.63.2558,190
75121.9.64.0/19121.9.64.1 to 121.9.95.254121.9.95.2558,190
76121.9.96.0/19121.9.96.1 to 121.9.127.254121.9.127.2558,190
77121.9.128.0/19121.9.128.1 to 121.9.159.254121.9.159.2558,190
78121.9.160.0/19121.9.160.1 to 121.9.191.254121.9.191.2558,190
79121.9.192.0/19121.9.192.1 to 121.9.223.254121.9.223.2558,190
80121.9.224.0/19121.9.224.1 to 121.9.255.254121.9.255.2558,190
81121.10.0.0/19121.10.0.1 to 121.10.31.254121.10.31.2558,190
82121.10.32.0/19121.10.32.1 to 121.10.63.254121.10.63.2558,190
83121.10.64.0/19121.10.64.1 to 121.10.95.254121.10.95.2558,190
84121.10.96.0/19121.10.96.1 to 121.10.127.254121.10.127.2558,190
85121.10.128.0/19121.10.128.1 to 121.10.159.254121.10.159.2558,190
86121.10.160.0/19121.10.160.1 to 121.10.191.254121.10.191.2558,190
87121.10.192.0/19121.10.192.1 to 121.10.223.254121.10.223.2558,190
88121.10.224.0/19121.10.224.1 to 121.10.255.254121.10.255.2558,190
89121.11.0.0/19121.11.0.1 to 121.11.31.254121.11.31.2558,190
90121.11.32.0/19121.11.32.1 to 121.11.63.254121.11.63.2558,190
91121.11.64.0/19121.11.64.1 to 121.11.95.254121.11.95.2558,190
92121.11.96.0/19121.11.96.1 to 121.11.127.254121.11.127.2558,190
93121.11.128.0/19121.11.128.1 to 121.11.159.254121.11.159.2558,190
94121.11.160.0/19121.11.160.1 to 121.11.191.254121.11.191.2558,190
95121.11.192.0/19121.11.192.1 to 121.11.223.254121.11.223.2558,190
96121.11.224.0/19121.11.224.1 to 121.11.255.254121.11.255.2558,190
97121.12.0.0/19121.12.0.1 to 121.12.31.254121.12.31.2558,190
98121.12.32.0/19121.12.32.1 to 121.12.63.254121.12.63.2558,190
99121.12.64.0/19121.12.64.1 to 121.12.95.254121.12.95.2558,190
100121.12.96.0/19121.12.96.1 to 121.12.127.254121.12.127.2558,190
101121.12.128.0/19121.12.128.1 to 121.12.159.254121.12.159.2558,190
102121.12.160.0/19121.12.160.1 to 121.12.191.254121.12.191.2558,190
103121.12.192.0/19121.12.192.1 to 121.12.223.254121.12.223.2558,190
104121.12.224.0/19121.12.224.1 to 121.12.255.254121.12.255.2558,190
105121.13.0.0/19121.13.0.1 to 121.13.31.254121.13.31.2558,190
106121.13.32.0/19121.13.32.1 to 121.13.63.254121.13.63.2558,190
107121.13.64.0/19121.13.64.1 to 121.13.95.254121.13.95.2558,190
108121.13.96.0/19121.13.96.1 to 121.13.127.254121.13.127.2558,190
109121.13.128.0/19121.13.128.1 to 121.13.159.254121.13.159.2558,190
110121.13.160.0/19121.13.160.1 to 121.13.191.254121.13.191.2558,190
111121.13.192.0/19121.13.192.1 to 121.13.223.254121.13.223.2558,190
112121.13.224.0/19121.13.224.1 to 121.13.255.254121.13.255.2558,190
113121.14.0.0/19121.14.0.1 to 121.14.31.254121.14.31.2558,190
114121.14.32.0/19121.14.32.1 to 121.14.63.254121.14.63.2558,190
115121.14.64.0/19121.14.64.1 to 121.14.95.254121.14.95.2558,190
116121.14.96.0/19121.14.96.1 to 121.14.127.254121.14.127.2558,190
117121.14.128.0/19121.14.128.1 to 121.14.159.254121.14.159.2558,190
118121.14.160.0/19121.14.160.1 to 121.14.191.254121.14.191.2558,190
119121.14.192.0/19121.14.192.1 to 121.14.223.254121.14.223.2558,190
120121.14.224.0/19121.14.224.1 to 121.14.255.254121.14.255.2558,190
121121.15.0.0/19121.15.0.1 to 121.15.31.254121.15.31.2558,190
122121.15.32.0/19121.15.32.1 to 121.15.63.254121.15.63.2558,190
123121.15.64.0/19121.15.64.1 to 121.15.95.254121.15.95.2558,190
124121.15.96.0/19121.15.96.1 to 121.15.127.254121.15.127.2558,190
125121.15.128.0/19121.15.128.1 to 121.15.159.254121.15.159.2558,190
126121.15.160.0/19121.15.160.1 to 121.15.191.254121.15.191.2558,190
127121.15.192.0/19121.15.192.1 to 121.15.223.254121.15.223.2558,190
128121.15.224.0/19121.15.224.1 to 121.15.255.254121.15.255.2558,190
129121.16.0.0/19121.16.0.1 to 121.16.31.254121.16.31.2558,190
130121.16.32.0/19121.16.32.1 to 121.16.63.254121.16.63.2558,190
131121.16.64.0/19121.16.64.1 to 121.16.95.254121.16.95.2558,190
132121.16.96.0/19121.16.96.1 to 121.16.127.254121.16.127.2558,190
133121.16.128.0/19121.16.128.1 to 121.16.159.254121.16.159.2558,190
134121.16.160.0/19121.16.160.1 to 121.16.191.254121.16.191.2558,190
135121.16.192.0/19121.16.192.1 to 121.16.223.254121.16.223.2558,190
136121.16.224.0/19121.16.224.1 to 121.16.255.254121.16.255.2558,190
137121.17.0.0/19121.17.0.1 to 121.17.31.254121.17.31.2558,190
138121.17.32.0/19121.17.32.1 to 121.17.63.254121.17.63.2558,190
139121.17.64.0/19121.17.64.1 to 121.17.95.254121.17.95.2558,190
140121.17.96.0/19121.17.96.1 to 121.17.127.254121.17.127.2558,190
141121.17.128.0/19121.17.128.1 to 121.17.159.254121.17.159.2558,190
142121.17.160.0/19121.17.160.1 to 121.17.191.254121.17.191.2558,190
143121.17.192.0/19121.17.192.1 to 121.17.223.254121.17.223.2558,190
144121.17.224.0/19121.17.224.1 to 121.17.255.254121.17.255.2558,190
145121.18.0.0/19121.18.0.1 to 121.18.31.254121.18.31.2558,190
146121.18.32.0/19121.18.32.1 to 121.18.63.254121.18.63.2558,190
147121.18.64.0/19121.18.64.1 to 121.18.95.254121.18.95.2558,190
148121.18.96.0/19121.18.96.1 to 121.18.127.254121.18.127.2558,190
149121.18.128.0/19121.18.128.1 to 121.18.159.254121.18.159.2558,190
150121.18.160.0/19121.18.160.1 to 121.18.191.254121.18.191.2558,190
151121.18.192.0/19121.18.192.1 to 121.18.223.254121.18.223.2558,190
152121.18.224.0/19121.18.224.1 to 121.18.255.254121.18.255.2558,190
153121.19.0.0/19121.19.0.1 to 121.19.31.254121.19.31.2558,190
154121.19.32.0/19121.19.32.1 to 121.19.63.254121.19.63.2558,190
155121.19.64.0/19121.19.64.1 to 121.19.95.254121.19.95.2558,190
156121.19.96.0/19121.19.96.1 to 121.19.127.254121.19.127.2558,190
157121.19.128.0/19121.19.128.1 to 121.19.159.254121.19.159.2558,190
158121.19.160.0/19121.19.160.1 to 121.19.191.254121.19.191.2558,190
159121.19.192.0/19121.19.192.1 to 121.19.223.254121.19.223.2558,190
160121.19.224.0/19121.19.224.1 to 121.19.255.254121.19.255.2558,190
161121.20.0.0/19121.20.0.1 to 121.20.31.254121.20.31.2558,190
162121.20.32.0/19121.20.32.1 to 121.20.63.254121.20.63.2558,190
163121.20.64.0/19121.20.64.1 to 121.20.95.254121.20.95.2558,190
164121.20.96.0/19121.20.96.1 to 121.20.127.254121.20.127.2558,190
165121.20.128.0/19121.20.128.1 to 121.20.159.254121.20.159.2558,190
166121.20.160.0/19121.20.160.1 to 121.20.191.254121.20.191.2558,190
167121.20.192.0/19121.20.192.1 to 121.20.223.254121.20.223.2558,190
168121.20.224.0/19121.20.224.1 to 121.20.255.254121.20.255.2558,190
169121.21.0.0/19121.21.0.1 to 121.21.31.254121.21.31.2558,190
170121.21.32.0/19121.21.32.1 to 121.21.63.254121.21.63.2558,190
171121.21.64.0/19121.21.64.1 to 121.21.95.254121.21.95.2558,190
172121.21.96.0/19121.21.96.1 to 121.21.127.254121.21.127.2558,190
173121.21.128.0/19121.21.128.1 to 121.21.159.254121.21.159.2558,190
174121.21.160.0/19121.21.160.1 to 121.21.191.254121.21.191.2558,190
175121.21.192.0/19121.21.192.1 to 121.21.223.254121.21.223.2558,190
176121.21.224.0/19121.21.224.1 to 121.21.255.254121.21.255.2558,190
177121.22.0.0/19121.22.0.1 to 121.22.31.254121.22.31.2558,190
178121.22.32.0/19121.22.32.1 to 121.22.63.254121.22.63.2558,190
179121.22.64.0/19121.22.64.1 to 121.22.95.254121.22.95.2558,190
180121.22.96.0/19121.22.96.1 to 121.22.127.254121.22.127.2558,190
181121.22.128.0/19121.22.128.1 to 121.22.159.254121.22.159.2558,190
182121.22.160.0/19121.22.160.1 to 121.22.191.254121.22.191.2558,190
183121.22.192.0/19121.22.192.1 to 121.22.223.254121.22.223.2558,190
184121.22.224.0/19121.22.224.1 to 121.22.255.254121.22.255.2558,190
185121.23.0.0/19121.23.0.1 to 121.23.31.254121.23.31.2558,190
186121.23.32.0/19121.23.32.1 to 121.23.63.254121.23.63.2558,190
187121.23.64.0/19121.23.64.1 to 121.23.95.254121.23.95.2558,190
188121.23.96.0/19121.23.96.1 to 121.23.127.254121.23.127.2558,190
189121.23.128.0/19121.23.128.1 to 121.23.159.254121.23.159.2558,190
190121.23.160.0/19121.23.160.1 to 121.23.191.254121.23.191.2558,190
191121.23.192.0/19121.23.192.1 to 121.23.223.254121.23.223.2558,190
192121.23.224.0/19121.23.224.1 to 121.23.255.254121.23.255.2558,190
193121.24.0.0/19121.24.0.1 to 121.24.31.254121.24.31.2558,190
194121.24.32.0/19121.24.32.1 to 121.24.63.254121.24.63.2558,190
195121.24.64.0/19121.24.64.1 to 121.24.95.254121.24.95.2558,190
196121.24.96.0/19121.24.96.1 to 121.24.127.254121.24.127.2558,190
197121.24.128.0/19121.24.128.1 to 121.24.159.254121.24.159.2558,190
198121.24.160.0/19121.24.160.1 to 121.24.191.254121.24.191.2558,190
199121.24.192.0/19121.24.192.1 to 121.24.223.254121.24.223.2558,190
200121.24.224.0/19121.24.224.1 to 121.24.255.254121.24.255.2558,190
201121.25.0.0/19121.25.0.1 to 121.25.31.254121.25.31.2558,190
202121.25.32.0/19121.25.32.1 to 121.25.63.254121.25.63.2558,190
203121.25.64.0/19121.25.64.1 to 121.25.95.254121.25.95.2558,190
204121.25.96.0/19121.25.96.1 to 121.25.127.254121.25.127.2558,190
205121.25.128.0/19121.25.128.1 to 121.25.159.254121.25.159.2558,190
206121.25.160.0/19121.25.160.1 to 121.25.191.254121.25.191.2558,190
207121.25.192.0/19121.25.192.1 to 121.25.223.254121.25.223.2558,190
208121.25.224.0/19121.25.224.1 to 121.25.255.254121.25.255.2558,190
209121.26.0.0/19121.26.0.1 to 121.26.31.254121.26.31.2558,190
210121.26.32.0/19121.26.32.1 to 121.26.63.254121.26.63.2558,190
211121.26.64.0/19121.26.64.1 to 121.26.95.254121.26.95.2558,190
212121.26.96.0/19121.26.96.1 to 121.26.127.254121.26.127.2558,190
213121.26.128.0/19121.26.128.1 to 121.26.159.254121.26.159.2558,190
214121.26.160.0/19121.26.160.1 to 121.26.191.254121.26.191.2558,190
215121.26.192.0/19121.26.192.1 to 121.26.223.254121.26.223.2558,190
216121.26.224.0/19121.26.224.1 to 121.26.255.254121.26.255.2558,190
217121.27.0.0/19121.27.0.1 to 121.27.31.254121.27.31.2558,190
218121.27.32.0/19121.27.32.1 to 121.27.63.254121.27.63.2558,190
219121.27.64.0/19121.27.64.1 to 121.27.95.254121.27.95.2558,190
220121.27.96.0/19121.27.96.1 to 121.27.127.254121.27.127.2558,190
221121.27.128.0/19121.27.128.1 to 121.27.159.254121.27.159.2558,190
222121.27.160.0/19121.27.160.1 to 121.27.191.254121.27.191.2558,190
223121.27.192.0/19121.27.192.1 to 121.27.223.254121.27.223.2558,190
224121.27.224.0/19121.27.224.1 to 121.27.255.254121.27.255.2558,190
225121.28.0.0/19121.28.0.1 to 121.28.31.254121.28.31.2558,190
226121.28.32.0/19121.28.32.1 to 121.28.63.254121.28.63.2558,190
227121.28.64.0/19121.28.64.1 to 121.28.95.254121.28.95.2558,190
228121.28.96.0/19121.28.96.1 to 121.28.127.254121.28.127.2558,190
229121.28.128.0/19121.28.128.1 to 121.28.159.254121.28.159.2558,190
230121.28.160.0/19121.28.160.1 to 121.28.191.254121.28.191.2558,190
231121.28.192.0/19121.28.192.1 to 121.28.223.254121.28.223.2558,190
232121.28.224.0/19121.28.224.1 to 121.28.255.254121.28.255.2558,190
233121.29.0.0/19121.29.0.1 to 121.29.31.254121.29.31.2558,190
234121.29.32.0/19121.29.32.1 to 121.29.63.254121.29.63.2558,190
235121.29.64.0/19121.29.64.1 to 121.29.95.254121.29.95.2558,190
236121.29.96.0/19121.29.96.1 to 121.29.127.254121.29.127.2558,190
237121.29.128.0/19121.29.128.1 to 121.29.159.254121.29.159.2558,190
238121.29.160.0/19121.29.160.1 to 121.29.191.254121.29.191.2558,190
239121.29.192.0/19121.29.192.1 to 121.29.223.254121.29.223.2558,190
240121.29.224.0/19121.29.224.1 to 121.29.255.254121.29.255.2558,190
241121.30.0.0/19121.30.0.1 to 121.30.31.254121.30.31.2558,190
242121.30.32.0/19121.30.32.1 to 121.30.63.254121.30.63.2558,190
243121.30.64.0/19121.30.64.1 to 121.30.95.254121.30.95.2558,190
244121.30.96.0/19121.30.96.1 to 121.30.127.254121.30.127.2558,190
245121.30.128.0/19121.30.128.1 to 121.30.159.254121.30.159.2558,190
246121.30.160.0/19121.30.160.1 to 121.30.191.254121.30.191.2558,190
247121.30.192.0/19121.30.192.1 to 121.30.223.254121.30.223.2558,190
248121.30.224.0/19121.30.224.1 to 121.30.255.254121.30.255.2558,190
249121.31.0.0/19121.31.0.1 to 121.31.31.254121.31.31.2558,190
250121.31.32.0/19121.31.32.1 to 121.31.63.254121.31.63.2558,190
251121.31.64.0/19121.31.64.1 to 121.31.95.254121.31.95.2558,190
252121.31.96.0/19121.31.96.1 to 121.31.127.254121.31.127.2558,190
253121.31.128.0/19121.31.128.1 to 121.31.159.254121.31.159.2558,190
254121.31.160.0/19121.31.160.1 to 121.31.191.254121.31.191.2558,190
255121.31.192.0/19121.31.192.1 to 121.31.223.254121.31.223.2558,190
256121.31.224.0/19121.31.224.1 to 121.31.255.254121.31.255.2558,190

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.