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.

Network123.128.0.0/9

Usable hosts8,388,606

Subnet mask255.128.0.0

Addresses8,388,608

Network address: 123.128.0.0
Broadcast address: 123.255.255.255
First usable: 123.128.0.1
Last usable: 123.255.255.254
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 7B800000 · Integer 2071986176 to 2080374783
Reverse DNS zones: 128.123.in-addr.arpa
129.123.in-addr.arpa
130.123.in-addr.arpa
131.123.in-addr.arpa
132.123.in-addr.arpa
133.123.in-addr.arpa
134.123.in-addr.arpa
135.123.in-addr.arpa
136.123.in-addr.arpa
137.123.in-addr.arpa
138.123.in-addr.arpa
139.123.in-addr.arpa
140.123.in-addr.arpa
141.123.in-addr.arpa
142.123.in-addr.arpa
143.123.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
Address	`01111011.10000000.00000000.00000000`	`123.128.0.0`
Subnet mask	`11111111.10000000.00000000.00000000`	`255.128.0.0`
Network	`01111011.10000000.00000000.00000000`	`123.128.0.0`
Broadcast	`01111011.11111111.11111111.11111111`	`123.255.255.255`

Split into smaller subnets/20

/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)

123.128.0.0/9 makes 2,048 subnets of /20; the first 256 are listed.

Subnets
#	Subnet	Usable hosts range	Broadcast	Hosts
1	`123.128.0.0/20`	`123.128.0.1` to `123.128.15.254`	123.128.15.255	4,094
2	`123.128.16.0/20`	`123.128.16.1` to `123.128.31.254`	123.128.31.255	4,094
3	`123.128.32.0/20`	`123.128.32.1` to `123.128.47.254`	123.128.47.255	4,094
4	`123.128.48.0/20`	`123.128.48.1` to `123.128.63.254`	123.128.63.255	4,094
5	`123.128.64.0/20`	`123.128.64.1` to `123.128.79.254`	123.128.79.255	4,094
6	`123.128.80.0/20`	`123.128.80.1` to `123.128.95.254`	123.128.95.255	4,094
7	`123.128.96.0/20`	`123.128.96.1` to `123.128.111.254`	123.128.111.255	4,094
8	`123.128.112.0/20`	`123.128.112.1` to `123.128.127.254`	123.128.127.255	4,094
9	`123.128.128.0/20`	`123.128.128.1` to `123.128.143.254`	123.128.143.255	4,094
10	`123.128.144.0/20`	`123.128.144.1` to `123.128.159.254`	123.128.159.255	4,094
11	`123.128.160.0/20`	`123.128.160.1` to `123.128.175.254`	123.128.175.255	4,094
12	`123.128.176.0/20`	`123.128.176.1` to `123.128.191.254`	123.128.191.255	4,094
13	`123.128.192.0/20`	`123.128.192.1` to `123.128.207.254`	123.128.207.255	4,094
14	`123.128.208.0/20`	`123.128.208.1` to `123.128.223.254`	123.128.223.255	4,094
15	`123.128.224.0/20`	`123.128.224.1` to `123.128.239.254`	123.128.239.255	4,094
16	`123.128.240.0/20`	`123.128.240.1` to `123.128.255.254`	123.128.255.255	4,094
17	`123.129.0.0/20`	`123.129.0.1` to `123.129.15.254`	123.129.15.255	4,094
18	`123.129.16.0/20`	`123.129.16.1` to `123.129.31.254`	123.129.31.255	4,094
19	`123.129.32.0/20`	`123.129.32.1` to `123.129.47.254`	123.129.47.255	4,094
20	`123.129.48.0/20`	`123.129.48.1` to `123.129.63.254`	123.129.63.255	4,094
21	`123.129.64.0/20`	`123.129.64.1` to `123.129.79.254`	123.129.79.255	4,094
22	`123.129.80.0/20`	`123.129.80.1` to `123.129.95.254`	123.129.95.255	4,094
23	`123.129.96.0/20`	`123.129.96.1` to `123.129.111.254`	123.129.111.255	4,094
24	`123.129.112.0/20`	`123.129.112.1` to `123.129.127.254`	123.129.127.255	4,094
25	`123.129.128.0/20`	`123.129.128.1` to `123.129.143.254`	123.129.143.255	4,094
26	`123.129.144.0/20`	`123.129.144.1` to `123.129.159.254`	123.129.159.255	4,094
27	`123.129.160.0/20`	`123.129.160.1` to `123.129.175.254`	123.129.175.255	4,094
28	`123.129.176.0/20`	`123.129.176.1` to `123.129.191.254`	123.129.191.255	4,094
29	`123.129.192.0/20`	`123.129.192.1` to `123.129.207.254`	123.129.207.255	4,094
30	`123.129.208.0/20`	`123.129.208.1` to `123.129.223.254`	123.129.223.255	4,094
31	`123.129.224.0/20`	`123.129.224.1` to `123.129.239.254`	123.129.239.255	4,094
32	`123.129.240.0/20`	`123.129.240.1` to `123.129.255.254`	123.129.255.255	4,094
33	`123.130.0.0/20`	`123.130.0.1` to `123.130.15.254`	123.130.15.255	4,094
34	`123.130.16.0/20`	`123.130.16.1` to `123.130.31.254`	123.130.31.255	4,094
35	`123.130.32.0/20`	`123.130.32.1` to `123.130.47.254`	123.130.47.255	4,094
36	`123.130.48.0/20`	`123.130.48.1` to `123.130.63.254`	123.130.63.255	4,094
37	`123.130.64.0/20`	`123.130.64.1` to `123.130.79.254`	123.130.79.255	4,094
38	`123.130.80.0/20`	`123.130.80.1` to `123.130.95.254`	123.130.95.255	4,094
39	`123.130.96.0/20`	`123.130.96.1` to `123.130.111.254`	123.130.111.255	4,094
40	`123.130.112.0/20`	`123.130.112.1` to `123.130.127.254`	123.130.127.255	4,094
41	`123.130.128.0/20`	`123.130.128.1` to `123.130.143.254`	123.130.143.255	4,094
42	`123.130.144.0/20`	`123.130.144.1` to `123.130.159.254`	123.130.159.255	4,094
43	`123.130.160.0/20`	`123.130.160.1` to `123.130.175.254`	123.130.175.255	4,094
44	`123.130.176.0/20`	`123.130.176.1` to `123.130.191.254`	123.130.191.255	4,094
45	`123.130.192.0/20`	`123.130.192.1` to `123.130.207.254`	123.130.207.255	4,094
46	`123.130.208.0/20`	`123.130.208.1` to `123.130.223.254`	123.130.223.255	4,094
47	`123.130.224.0/20`	`123.130.224.1` to `123.130.239.254`	123.130.239.255	4,094
48	`123.130.240.0/20`	`123.130.240.1` to `123.130.255.254`	123.130.255.255	4,094
49	`123.131.0.0/20`	`123.131.0.1` to `123.131.15.254`	123.131.15.255	4,094
50	`123.131.16.0/20`	`123.131.16.1` to `123.131.31.254`	123.131.31.255	4,094
51	`123.131.32.0/20`	`123.131.32.1` to `123.131.47.254`	123.131.47.255	4,094
52	`123.131.48.0/20`	`123.131.48.1` to `123.131.63.254`	123.131.63.255	4,094
53	`123.131.64.0/20`	`123.131.64.1` to `123.131.79.254`	123.131.79.255	4,094
54	`123.131.80.0/20`	`123.131.80.1` to `123.131.95.254`	123.131.95.255	4,094
55	`123.131.96.0/20`	`123.131.96.1` to `123.131.111.254`	123.131.111.255	4,094
56	`123.131.112.0/20`	`123.131.112.1` to `123.131.127.254`	123.131.127.255	4,094
57	`123.131.128.0/20`	`123.131.128.1` to `123.131.143.254`	123.131.143.255	4,094
58	`123.131.144.0/20`	`123.131.144.1` to `123.131.159.254`	123.131.159.255	4,094
59	`123.131.160.0/20`	`123.131.160.1` to `123.131.175.254`	123.131.175.255	4,094
60	`123.131.176.0/20`	`123.131.176.1` to `123.131.191.254`	123.131.191.255	4,094
61	`123.131.192.0/20`	`123.131.192.1` to `123.131.207.254`	123.131.207.255	4,094
62	`123.131.208.0/20`	`123.131.208.1` to `123.131.223.254`	123.131.223.255	4,094
63	`123.131.224.0/20`	`123.131.224.1` to `123.131.239.254`	123.131.239.255	4,094
64	`123.131.240.0/20`	`123.131.240.1` to `123.131.255.254`	123.131.255.255	4,094
65	`123.132.0.0/20`	`123.132.0.1` to `123.132.15.254`	123.132.15.255	4,094
66	`123.132.16.0/20`	`123.132.16.1` to `123.132.31.254`	123.132.31.255	4,094
67	`123.132.32.0/20`	`123.132.32.1` to `123.132.47.254`	123.132.47.255	4,094
68	`123.132.48.0/20`	`123.132.48.1` to `123.132.63.254`	123.132.63.255	4,094
69	`123.132.64.0/20`	`123.132.64.1` to `123.132.79.254`	123.132.79.255	4,094
70	`123.132.80.0/20`	`123.132.80.1` to `123.132.95.254`	123.132.95.255	4,094
71	`123.132.96.0/20`	`123.132.96.1` to `123.132.111.254`	123.132.111.255	4,094
72	`123.132.112.0/20`	`123.132.112.1` to `123.132.127.254`	123.132.127.255	4,094
73	`123.132.128.0/20`	`123.132.128.1` to `123.132.143.254`	123.132.143.255	4,094
74	`123.132.144.0/20`	`123.132.144.1` to `123.132.159.254`	123.132.159.255	4,094
75	`123.132.160.0/20`	`123.132.160.1` to `123.132.175.254`	123.132.175.255	4,094
76	`123.132.176.0/20`	`123.132.176.1` to `123.132.191.254`	123.132.191.255	4,094
77	`123.132.192.0/20`	`123.132.192.1` to `123.132.207.254`	123.132.207.255	4,094
78	`123.132.208.0/20`	`123.132.208.1` to `123.132.223.254`	123.132.223.255	4,094
79	`123.132.224.0/20`	`123.132.224.1` to `123.132.239.254`	123.132.239.255	4,094
80	`123.132.240.0/20`	`123.132.240.1` to `123.132.255.254`	123.132.255.255	4,094
81	`123.133.0.0/20`	`123.133.0.1` to `123.133.15.254`	123.133.15.255	4,094
82	`123.133.16.0/20`	`123.133.16.1` to `123.133.31.254`	123.133.31.255	4,094
83	`123.133.32.0/20`	`123.133.32.1` to `123.133.47.254`	123.133.47.255	4,094
84	`123.133.48.0/20`	`123.133.48.1` to `123.133.63.254`	123.133.63.255	4,094
85	`123.133.64.0/20`	`123.133.64.1` to `123.133.79.254`	123.133.79.255	4,094
86	`123.133.80.0/20`	`123.133.80.1` to `123.133.95.254`	123.133.95.255	4,094
87	`123.133.96.0/20`	`123.133.96.1` to `123.133.111.254`	123.133.111.255	4,094
88	`123.133.112.0/20`	`123.133.112.1` to `123.133.127.254`	123.133.127.255	4,094
89	`123.133.128.0/20`	`123.133.128.1` to `123.133.143.254`	123.133.143.255	4,094
90	`123.133.144.0/20`	`123.133.144.1` to `123.133.159.254`	123.133.159.255	4,094
91	`123.133.160.0/20`	`123.133.160.1` to `123.133.175.254`	123.133.175.255	4,094
92	`123.133.176.0/20`	`123.133.176.1` to `123.133.191.254`	123.133.191.255	4,094
93	`123.133.192.0/20`	`123.133.192.1` to `123.133.207.254`	123.133.207.255	4,094
94	`123.133.208.0/20`	`123.133.208.1` to `123.133.223.254`	123.133.223.255	4,094
95	`123.133.224.0/20`	`123.133.224.1` to `123.133.239.254`	123.133.239.255	4,094
96	`123.133.240.0/20`	`123.133.240.1` to `123.133.255.254`	123.133.255.255	4,094
97	`123.134.0.0/20`	`123.134.0.1` to `123.134.15.254`	123.134.15.255	4,094
98	`123.134.16.0/20`	`123.134.16.1` to `123.134.31.254`	123.134.31.255	4,094
99	`123.134.32.0/20`	`123.134.32.1` to `123.134.47.254`	123.134.47.255	4,094
100	`123.134.48.0/20`	`123.134.48.1` to `123.134.63.254`	123.134.63.255	4,094
101	`123.134.64.0/20`	`123.134.64.1` to `123.134.79.254`	123.134.79.255	4,094
102	`123.134.80.0/20`	`123.134.80.1` to `123.134.95.254`	123.134.95.255	4,094
103	`123.134.96.0/20`	`123.134.96.1` to `123.134.111.254`	123.134.111.255	4,094
104	`123.134.112.0/20`	`123.134.112.1` to `123.134.127.254`	123.134.127.255	4,094
105	`123.134.128.0/20`	`123.134.128.1` to `123.134.143.254`	123.134.143.255	4,094
106	`123.134.144.0/20`	`123.134.144.1` to `123.134.159.254`	123.134.159.255	4,094
107	`123.134.160.0/20`	`123.134.160.1` to `123.134.175.254`	123.134.175.255	4,094
108	`123.134.176.0/20`	`123.134.176.1` to `123.134.191.254`	123.134.191.255	4,094
109	`123.134.192.0/20`	`123.134.192.1` to `123.134.207.254`	123.134.207.255	4,094
110	`123.134.208.0/20`	`123.134.208.1` to `123.134.223.254`	123.134.223.255	4,094
111	`123.134.224.0/20`	`123.134.224.1` to `123.134.239.254`	123.134.239.255	4,094
112	`123.134.240.0/20`	`123.134.240.1` to `123.134.255.254`	123.134.255.255	4,094
113	`123.135.0.0/20`	`123.135.0.1` to `123.135.15.254`	123.135.15.255	4,094
114	`123.135.16.0/20`	`123.135.16.1` to `123.135.31.254`	123.135.31.255	4,094
115	`123.135.32.0/20`	`123.135.32.1` to `123.135.47.254`	123.135.47.255	4,094
116	`123.135.48.0/20`	`123.135.48.1` to `123.135.63.254`	123.135.63.255	4,094
117	`123.135.64.0/20`	`123.135.64.1` to `123.135.79.254`	123.135.79.255	4,094
118	`123.135.80.0/20`	`123.135.80.1` to `123.135.95.254`	123.135.95.255	4,094
119	`123.135.96.0/20`	`123.135.96.1` to `123.135.111.254`	123.135.111.255	4,094
120	`123.135.112.0/20`	`123.135.112.1` to `123.135.127.254`	123.135.127.255	4,094
121	`123.135.128.0/20`	`123.135.128.1` to `123.135.143.254`	123.135.143.255	4,094
122	`123.135.144.0/20`	`123.135.144.1` to `123.135.159.254`	123.135.159.255	4,094
123	`123.135.160.0/20`	`123.135.160.1` to `123.135.175.254`	123.135.175.255	4,094
124	`123.135.176.0/20`	`123.135.176.1` to `123.135.191.254`	123.135.191.255	4,094
125	`123.135.192.0/20`	`123.135.192.1` to `123.135.207.254`	123.135.207.255	4,094
126	`123.135.208.0/20`	`123.135.208.1` to `123.135.223.254`	123.135.223.255	4,094
127	`123.135.224.0/20`	`123.135.224.1` to `123.135.239.254`	123.135.239.255	4,094
128	`123.135.240.0/20`	`123.135.240.1` to `123.135.255.254`	123.135.255.255	4,094
129	`123.136.0.0/20`	`123.136.0.1` to `123.136.15.254`	123.136.15.255	4,094
130	`123.136.16.0/20`	`123.136.16.1` to `123.136.31.254`	123.136.31.255	4,094
131	`123.136.32.0/20`	`123.136.32.1` to `123.136.47.254`	123.136.47.255	4,094
132	`123.136.48.0/20`	`123.136.48.1` to `123.136.63.254`	123.136.63.255	4,094
133	`123.136.64.0/20`	`123.136.64.1` to `123.136.79.254`	123.136.79.255	4,094
134	`123.136.80.0/20`	`123.136.80.1` to `123.136.95.254`	123.136.95.255	4,094
135	`123.136.96.0/20`	`123.136.96.1` to `123.136.111.254`	123.136.111.255	4,094
136	`123.136.112.0/20`	`123.136.112.1` to `123.136.127.254`	123.136.127.255	4,094
137	`123.136.128.0/20`	`123.136.128.1` to `123.136.143.254`	123.136.143.255	4,094
138	`123.136.144.0/20`	`123.136.144.1` to `123.136.159.254`	123.136.159.255	4,094
139	`123.136.160.0/20`	`123.136.160.1` to `123.136.175.254`	123.136.175.255	4,094
140	`123.136.176.0/20`	`123.136.176.1` to `123.136.191.254`	123.136.191.255	4,094
141	`123.136.192.0/20`	`123.136.192.1` to `123.136.207.254`	123.136.207.255	4,094
142	`123.136.208.0/20`	`123.136.208.1` to `123.136.223.254`	123.136.223.255	4,094
143	`123.136.224.0/20`	`123.136.224.1` to `123.136.239.254`	123.136.239.255	4,094
144	`123.136.240.0/20`	`123.136.240.1` to `123.136.255.254`	123.136.255.255	4,094
145	`123.137.0.0/20`	`123.137.0.1` to `123.137.15.254`	123.137.15.255	4,094
146	`123.137.16.0/20`	`123.137.16.1` to `123.137.31.254`	123.137.31.255	4,094
147	`123.137.32.0/20`	`123.137.32.1` to `123.137.47.254`	123.137.47.255	4,094
148	`123.137.48.0/20`	`123.137.48.1` to `123.137.63.254`	123.137.63.255	4,094
149	`123.137.64.0/20`	`123.137.64.1` to `123.137.79.254`	123.137.79.255	4,094
150	`123.137.80.0/20`	`123.137.80.1` to `123.137.95.254`	123.137.95.255	4,094
151	`123.137.96.0/20`	`123.137.96.1` to `123.137.111.254`	123.137.111.255	4,094
152	`123.137.112.0/20`	`123.137.112.1` to `123.137.127.254`	123.137.127.255	4,094
153	`123.137.128.0/20`	`123.137.128.1` to `123.137.143.254`	123.137.143.255	4,094
154	`123.137.144.0/20`	`123.137.144.1` to `123.137.159.254`	123.137.159.255	4,094
155	`123.137.160.0/20`	`123.137.160.1` to `123.137.175.254`	123.137.175.255	4,094
156	`123.137.176.0/20`	`123.137.176.1` to `123.137.191.254`	123.137.191.255	4,094
157	`123.137.192.0/20`	`123.137.192.1` to `123.137.207.254`	123.137.207.255	4,094
158	`123.137.208.0/20`	`123.137.208.1` to `123.137.223.254`	123.137.223.255	4,094
159	`123.137.224.0/20`	`123.137.224.1` to `123.137.239.254`	123.137.239.255	4,094
160	`123.137.240.0/20`	`123.137.240.1` to `123.137.255.254`	123.137.255.255	4,094
161	`123.138.0.0/20`	`123.138.0.1` to `123.138.15.254`	123.138.15.255	4,094
162	`123.138.16.0/20`	`123.138.16.1` to `123.138.31.254`	123.138.31.255	4,094
163	`123.138.32.0/20`	`123.138.32.1` to `123.138.47.254`	123.138.47.255	4,094
164	`123.138.48.0/20`	`123.138.48.1` to `123.138.63.254`	123.138.63.255	4,094
165	`123.138.64.0/20`	`123.138.64.1` to `123.138.79.254`	123.138.79.255	4,094
166	`123.138.80.0/20`	`123.138.80.1` to `123.138.95.254`	123.138.95.255	4,094
167	`123.138.96.0/20`	`123.138.96.1` to `123.138.111.254`	123.138.111.255	4,094
168	`123.138.112.0/20`	`123.138.112.1` to `123.138.127.254`	123.138.127.255	4,094
169	`123.138.128.0/20`	`123.138.128.1` to `123.138.143.254`	123.138.143.255	4,094
170	`123.138.144.0/20`	`123.138.144.1` to `123.138.159.254`	123.138.159.255	4,094
171	`123.138.160.0/20`	`123.138.160.1` to `123.138.175.254`	123.138.175.255	4,094
172	`123.138.176.0/20`	`123.138.176.1` to `123.138.191.254`	123.138.191.255	4,094
173	`123.138.192.0/20`	`123.138.192.1` to `123.138.207.254`	123.138.207.255	4,094
174	`123.138.208.0/20`	`123.138.208.1` to `123.138.223.254`	123.138.223.255	4,094
175	`123.138.224.0/20`	`123.138.224.1` to `123.138.239.254`	123.138.239.255	4,094
176	`123.138.240.0/20`	`123.138.240.1` to `123.138.255.254`	123.138.255.255	4,094
177	`123.139.0.0/20`	`123.139.0.1` to `123.139.15.254`	123.139.15.255	4,094
178	`123.139.16.0/20`	`123.139.16.1` to `123.139.31.254`	123.139.31.255	4,094
179	`123.139.32.0/20`	`123.139.32.1` to `123.139.47.254`	123.139.47.255	4,094
180	`123.139.48.0/20`	`123.139.48.1` to `123.139.63.254`	123.139.63.255	4,094
181	`123.139.64.0/20`	`123.139.64.1` to `123.139.79.254`	123.139.79.255	4,094
182	`123.139.80.0/20`	`123.139.80.1` to `123.139.95.254`	123.139.95.255	4,094
183	`123.139.96.0/20`	`123.139.96.1` to `123.139.111.254`	123.139.111.255	4,094
184	`123.139.112.0/20`	`123.139.112.1` to `123.139.127.254`	123.139.127.255	4,094
185	`123.139.128.0/20`	`123.139.128.1` to `123.139.143.254`	123.139.143.255	4,094
186	`123.139.144.0/20`	`123.139.144.1` to `123.139.159.254`	123.139.159.255	4,094
187	`123.139.160.0/20`	`123.139.160.1` to `123.139.175.254`	123.139.175.255	4,094
188	`123.139.176.0/20`	`123.139.176.1` to `123.139.191.254`	123.139.191.255	4,094
189	`123.139.192.0/20`	`123.139.192.1` to `123.139.207.254`	123.139.207.255	4,094
190	`123.139.208.0/20`	`123.139.208.1` to `123.139.223.254`	123.139.223.255	4,094
191	`123.139.224.0/20`	`123.139.224.1` to `123.139.239.254`	123.139.239.255	4,094
192	`123.139.240.0/20`	`123.139.240.1` to `123.139.255.254`	123.139.255.255	4,094
193	`123.140.0.0/20`	`123.140.0.1` to `123.140.15.254`	123.140.15.255	4,094
194	`123.140.16.0/20`	`123.140.16.1` to `123.140.31.254`	123.140.31.255	4,094
195	`123.140.32.0/20`	`123.140.32.1` to `123.140.47.254`	123.140.47.255	4,094
196	`123.140.48.0/20`	`123.140.48.1` to `123.140.63.254`	123.140.63.255	4,094
197	`123.140.64.0/20`	`123.140.64.1` to `123.140.79.254`	123.140.79.255	4,094
198	`123.140.80.0/20`	`123.140.80.1` to `123.140.95.254`	123.140.95.255	4,094
199	`123.140.96.0/20`	`123.140.96.1` to `123.140.111.254`	123.140.111.255	4,094
200	`123.140.112.0/20`	`123.140.112.1` to `123.140.127.254`	123.140.127.255	4,094
201	`123.140.128.0/20`	`123.140.128.1` to `123.140.143.254`	123.140.143.255	4,094
202	`123.140.144.0/20`	`123.140.144.1` to `123.140.159.254`	123.140.159.255	4,094
203	`123.140.160.0/20`	`123.140.160.1` to `123.140.175.254`	123.140.175.255	4,094
204	`123.140.176.0/20`	`123.140.176.1` to `123.140.191.254`	123.140.191.255	4,094
205	`123.140.192.0/20`	`123.140.192.1` to `123.140.207.254`	123.140.207.255	4,094
206	`123.140.208.0/20`	`123.140.208.1` to `123.140.223.254`	123.140.223.255	4,094
207	`123.140.224.0/20`	`123.140.224.1` to `123.140.239.254`	123.140.239.255	4,094
208	`123.140.240.0/20`	`123.140.240.1` to `123.140.255.254`	123.140.255.255	4,094
209	`123.141.0.0/20`	`123.141.0.1` to `123.141.15.254`	123.141.15.255	4,094
210	`123.141.16.0/20`	`123.141.16.1` to `123.141.31.254`	123.141.31.255	4,094
211	`123.141.32.0/20`	`123.141.32.1` to `123.141.47.254`	123.141.47.255	4,094
212	`123.141.48.0/20`	`123.141.48.1` to `123.141.63.254`	123.141.63.255	4,094
213	`123.141.64.0/20`	`123.141.64.1` to `123.141.79.254`	123.141.79.255	4,094
214	`123.141.80.0/20`	`123.141.80.1` to `123.141.95.254`	123.141.95.255	4,094
215	`123.141.96.0/20`	`123.141.96.1` to `123.141.111.254`	123.141.111.255	4,094
216	`123.141.112.0/20`	`123.141.112.1` to `123.141.127.254`	123.141.127.255	4,094
217	`123.141.128.0/20`	`123.141.128.1` to `123.141.143.254`	123.141.143.255	4,094
218	`123.141.144.0/20`	`123.141.144.1` to `123.141.159.254`	123.141.159.255	4,094
219	`123.141.160.0/20`	`123.141.160.1` to `123.141.175.254`	123.141.175.255	4,094
220	`123.141.176.0/20`	`123.141.176.1` to `123.141.191.254`	123.141.191.255	4,094
221	`123.141.192.0/20`	`123.141.192.1` to `123.141.207.254`	123.141.207.255	4,094
222	`123.141.208.0/20`	`123.141.208.1` to `123.141.223.254`	123.141.223.255	4,094
223	`123.141.224.0/20`	`123.141.224.1` to `123.141.239.254`	123.141.239.255	4,094
224	`123.141.240.0/20`	`123.141.240.1` to `123.141.255.254`	123.141.255.255	4,094
225	`123.142.0.0/20`	`123.142.0.1` to `123.142.15.254`	123.142.15.255	4,094
226	`123.142.16.0/20`	`123.142.16.1` to `123.142.31.254`	123.142.31.255	4,094
227	`123.142.32.0/20`	`123.142.32.1` to `123.142.47.254`	123.142.47.255	4,094
228	`123.142.48.0/20`	`123.142.48.1` to `123.142.63.254`	123.142.63.255	4,094
229	`123.142.64.0/20`	`123.142.64.1` to `123.142.79.254`	123.142.79.255	4,094
230	`123.142.80.0/20`	`123.142.80.1` to `123.142.95.254`	123.142.95.255	4,094
231	`123.142.96.0/20`	`123.142.96.1` to `123.142.111.254`	123.142.111.255	4,094
232	`123.142.112.0/20`	`123.142.112.1` to `123.142.127.254`	123.142.127.255	4,094
233	`123.142.128.0/20`	`123.142.128.1` to `123.142.143.254`	123.142.143.255	4,094
234	`123.142.144.0/20`	`123.142.144.1` to `123.142.159.254`	123.142.159.255	4,094
235	`123.142.160.0/20`	`123.142.160.1` to `123.142.175.254`	123.142.175.255	4,094
236	`123.142.176.0/20`	`123.142.176.1` to `123.142.191.254`	123.142.191.255	4,094
237	`123.142.192.0/20`	`123.142.192.1` to `123.142.207.254`	123.142.207.255	4,094
238	`123.142.208.0/20`	`123.142.208.1` to `123.142.223.254`	123.142.223.255	4,094
239	`123.142.224.0/20`	`123.142.224.1` to `123.142.239.254`	123.142.239.255	4,094
240	`123.142.240.0/20`	`123.142.240.1` to `123.142.255.254`	123.142.255.255	4,094
241	`123.143.0.0/20`	`123.143.0.1` to `123.143.15.254`	123.143.15.255	4,094
242	`123.143.16.0/20`	`123.143.16.1` to `123.143.31.254`	123.143.31.255	4,094
243	`123.143.32.0/20`	`123.143.32.1` to `123.143.47.254`	123.143.47.255	4,094
244	`123.143.48.0/20`	`123.143.48.1` to `123.143.63.254`	123.143.63.255	4,094
245	`123.143.64.0/20`	`123.143.64.1` to `123.143.79.254`	123.143.79.255	4,094
246	`123.143.80.0/20`	`123.143.80.1` to `123.143.95.254`	123.143.95.255	4,094
247	`123.143.96.0/20`	`123.143.96.1` to `123.143.111.254`	123.143.111.255	4,094
248	`123.143.112.0/20`	`123.143.112.1` to `123.143.127.254`	123.143.127.255	4,094
249	`123.143.128.0/20`	`123.143.128.1` to `123.143.143.254`	123.143.143.255	4,094
250	`123.143.144.0/20`	`123.143.144.1` to `123.143.159.254`	123.143.159.255	4,094
251	`123.143.160.0/20`	`123.143.160.1` to `123.143.175.254`	123.143.175.255	4,094
252	`123.143.176.0/20`	`123.143.176.1` to `123.143.191.254`	123.143.191.255	4,094
253	`123.143.192.0/20`	`123.143.192.1` to `123.143.207.254`	123.143.207.255	4,094
254	`123.143.208.0/20`	`123.143.208.1` to `123.143.223.254`	123.143.223.255	4,094
255	`123.143.224.0/20`	`123.143.224.1` to `123.143.239.254`	123.143.239.255	4,094
256	`123.143.240.0/20`	`123.143.240.1` to `123.143.255.254`	123.143.255.255	4,094

IPv4 CIDR reference (/0 to /32)

IPv4 prefix lengths
Prefix	Subnet mask	Wildcard	Addresses	Usable hosts	Size	Typical use
/0	0.0.0.0	255.255.255.255	4,294,967,296	4,294,967,294	16,777,216 × /24
/1	128.0.0.0	127.255.255.255	2,147,483,648	2,147,483,646	8,388,608 × /24
/2	192.0.0.0	63.255.255.255	1,073,741,824	1,073,741,822	4,194,304 × /24
/3	224.0.0.0	31.255.255.255	536,870,912	536,870,910	2,097,152 × /24
/4	240.0.0.0	15.255.255.255	268,435,456	268,435,454	1,048,576 × /24
/5	248.0.0.0	7.255.255.255	134,217,728	134,217,726	524,288 × /24
/6	252.0.0.0	3.255.255.255	67,108,864	67,108,862	262,144 × /24
/7	254.0.0.0	1.255.255.255	33,554,432	33,554,430	131,072 × /24
/8	255.0.0.0	0.255.255.255	16,777,216	16,777,214	65,536 × /24	Old class A; 10.0.0.0/8
/9	255.128.0.0	0.127.255.255	8,388,608	8,388,606	32,768 × /24
/10	255.192.0.0	0.63.255.255	4,194,304	4,194,302	16,384 × /24
/11	255.224.0.0	0.31.255.255	2,097,152	2,097,150	8,192 × /24
/12	255.240.0.0	0.15.255.255	1,048,576	1,048,574	4,096 × /24	172.16.0.0/12
/13	255.248.0.0	0.7.255.255	524,288	524,286	2,048 × /24
/14	255.252.0.0	0.3.255.255	262,144	262,142	1,024 × /24
/15	255.254.0.0	0.1.255.255	131,072	131,070	512 × /24
/16	255.255.0.0	0.0.255.255	65,536	65,534	256 × /24	Old class B; 192.168.0.0/16
/17	255.255.128.0	0.0.127.255	32,768	32,766	128 × /24
/18	255.255.192.0	0.0.63.255	16,384	16,382	64 × /24
/19	255.255.224.0	0.0.31.255	8,192	8,190	32 × /24
/20	255.255.240.0	0.0.15.255	4,096	4,094	16 × /24
/21	255.255.248.0	0.0.7.255	2,048	2,046	8 × /24
/22	255.255.252.0	0.0.3.255	1,024	1,022	4 × /24	Large office or guest Wi-Fi (1,022 hosts)
/23	255.255.254.0	0.0.1.255	512	510	2 × /24	Larger office LAN (510 hosts)
/24	255.255.255.0	0.0.0.255	256	254	1 × /24	Typical office LAN (old class C)
/25	255.255.255.128	0.0.0.127	128	126	1/2 of a /24	Smaller LAN or VLAN
/26	255.255.255.192	0.0.0.63	64	62	1/4 of a /24	Smaller LAN or VLAN
/27	255.255.255.224	0.0.0.31	32	30	1/8 of a /24	Small VLAN, phones, cameras
/28	255.255.255.240	0.0.0.15	16	14	1/16 of a /24	Small VLAN, phones, cameras
/29	255.255.255.248	0.0.0.7	8	6	1/32 of a /24	Small fixed public block (5 usable)
/30	255.255.255.252	0.0.0.3	4	2	1/64 of a /24	Point-to-point (old style)
/31	255.255.255.254	0.0.0.1	2	2	1/128 of a /24	Point-to-point link (RFC 3021)
/32	255.255.255.255	0.0.0.0	1	1	1/256 of a /24	One host

IPv6 prefix reference

IPv6 prefix lengths
Prefix	Addresses	/64 LANs	/48 sites	Nibble	Typical use
/3	42,535,295,865,117,307,932,921,825,928,971,026,432 (2^125)	2,305,843,009,213,693,952	35,184,372,088,832	No	All global unicast (2000::/3)
/16	5,192,296,858,534,827,628,530,496,329,220,096 (2^112)	281,474,976,710,656	4,294,967,296	Yes
/20	324,518,553,658,426,726,783,156,020,576,256 (2^108)	17,592,186,044,416	268,435,456	Yes	Large provider allocation (RIPE minimum for some)
/29	633,825,300,114,114,700,748,351,602,688 (2^99)	34,359,738,368	524,288	No	RIPE allocation to a provider (often)
/32	79,228,162,514,264,337,593,543,950,336 (2^96)	4,294,967,296	65,536	Yes	Provider allocation (RIPE default)
/36	4,951,760,157,141,521,099,596,496,896 (2^92)	268,435,456	4,096	Yes
/40	309,485,009,821,345,068,724,781,056 (2^88)	16,777,216	256	Yes
/44	19,342,813,113,834,066,795,298,816 (2^84)	1,048,576	16	Yes
/48	1,208,925,819,614,629,174,706,176 (2^80)	65,536	1	Yes	One site or organisation (RIPE PI / assignment)
/52	75,557,863,725,914,323,419,136 (2^76)	4,096		Yes
/56	4,722,366,482,869,645,213,696 (2^72)	256		Yes	Small site or home (common provider assignment)
/60	295,147,905,179,352,825,856 (2^68)	16		Yes	Some home broadband (16 LANs)
/64	18,446,744,073,709,551,616 (2^64)	1		Yes	One LAN or VLAN (needed for SLAAC)
/72	72,057,594,037,927,936 (2^56)	1/256 of a /64		Yes
/80	281,474,976,710,656 (2^48)	1/65,536 of a /64		Yes
/96	4,294,967,296	1/4,294,967,296 of a /64		Yes	Embeds an IPv4 address (NAT64)
/112	65,536	1/281,474,976,710,656 of a /64		Yes
/120	256	1/72,057,594,037,927,936 of a /64		Yes
/124	16	1/1,152,921,504,606,846,976 of a /64		Yes
/126	4	1/4,611,686,018,427,387,904 of a /64		No
/127	2	1/9,223,372,036,854,775,808 of a /64		No	Point-to-point link (RFC 6164)
/128	1	1/18,446,744,073,709,551,616 of a /64		Yes	One host or loopback

Private and special ranges

IPv4

Special-purpose ranges
Range	Name	What it is
`255.255.255.255/32`	Limited broadcast	Every host on the local network
`0.0.0.0/8`	This network	Not routed; 0.0.0.0 means "any address" in settings
`10.0.0.0/8`	Private (RFC 1918)	Office and home networks; not routed on the internet
`100.64.0.0/10`	Shared address space (CGNAT)	Used by providers behind carrier-grade NAT (RFC 6598)
`127.0.0.0/8`	Loopback	This computer
`169.254.0.0/16`	Link-local (APIPA)	Self-assigned when no DHCP server answers
`172.16.0.0/12`	Private (RFC 1918)	Office and home networks; not routed on the internet
`192.0.0.0/24`	IETF protocol assignments	Special uses such as DS-Lite
`192.0.2.0/24`	Documentation (TEST-NET-1)	For examples; never used on a network
`192.88.99.0/24`	6to4 relay (deprecated)	Formerly anycast for 6to4
`192.168.0.0/16`	Private (RFC 1918)	Office and home networks; not routed on the internet
`198.18.0.0/15`	Benchmarking	Network equipment testing (RFC 2544)
`198.51.100.0/24`	Documentation (TEST-NET-2)	For examples; never used on a network
`203.0.113.0/24`	Documentation (TEST-NET-3)	For examples; never used on a network
`224.0.0.0/4`	Multicast	One-to-many traffic, such as IPTV and routing protocols
`240.0.0.0/4`	Reserved	Future use; not usable on most systems

IPv6

Special-purpose ranges
Range	Name	What it is
`::/128`	Unspecified	No address; :: means "any address" in settings
`::1/128`	Loopback	This computer
`::ffff:0:0/96`	IPv4-mapped	An IPv4 address written as IPv6
`64:ff9b::/96`	NAT64	IPv4 addresses reached through a NAT64 gateway
`100::/64`	Discard only	Traffic sent here is dropped (RFC 6666)
`2001:db8::/32`	Documentation	For examples; never used on a network
`2001::/32`	Teredo	IPv6 tunnelled over IPv4 UDP
`2002::/16`	6to4	IPv6 tunnelled over IPv4 (largely retired)
`3fff::/20`	Documentation	For examples (RFC 9637)
`fc00::/7`	Unique local (ULA)	Private IPv6, like RFC 1918; usually fd00::/8
`fe80::/10`	Link-local	Every IPv6 interface has one; not routed
`ff00::/8`	Multicast	One-to-many traffic; replaces broadcast
`2000::/3`	Global unicast	Public 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.

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IP subnet calculator

IPv4 CIDR reference (/0 to /32)

IPv6 prefix reference

Private and special ranges

IPv4

IPv6

About this tool

Common questions

IPv4 CIDR reference (/0 to /32)

IPv6 prefix reference

Private and special ranges

IPv4

IPv6

Common questions

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