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/21

/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 4,096 subnets of /21; the first 256 are listed.

Subnets
#	Subnet	Usable hosts range	Broadcast	Hosts
1	`123.128.0.0/21`	`123.128.0.1` to `123.128.7.254`	123.128.7.255	2,046
2	`123.128.8.0/21`	`123.128.8.1` to `123.128.15.254`	123.128.15.255	2,046
3	`123.128.16.0/21`	`123.128.16.1` to `123.128.23.254`	123.128.23.255	2,046
4	`123.128.24.0/21`	`123.128.24.1` to `123.128.31.254`	123.128.31.255	2,046
5	`123.128.32.0/21`	`123.128.32.1` to `123.128.39.254`	123.128.39.255	2,046
6	`123.128.40.0/21`	`123.128.40.1` to `123.128.47.254`	123.128.47.255	2,046
7	`123.128.48.0/21`	`123.128.48.1` to `123.128.55.254`	123.128.55.255	2,046
8	`123.128.56.0/21`	`123.128.56.1` to `123.128.63.254`	123.128.63.255	2,046
9	`123.128.64.0/21`	`123.128.64.1` to `123.128.71.254`	123.128.71.255	2,046
10	`123.128.72.0/21`	`123.128.72.1` to `123.128.79.254`	123.128.79.255	2,046
11	`123.128.80.0/21`	`123.128.80.1` to `123.128.87.254`	123.128.87.255	2,046
12	`123.128.88.0/21`	`123.128.88.1` to `123.128.95.254`	123.128.95.255	2,046
13	`123.128.96.0/21`	`123.128.96.1` to `123.128.103.254`	123.128.103.255	2,046
14	`123.128.104.0/21`	`123.128.104.1` to `123.128.111.254`	123.128.111.255	2,046
15	`123.128.112.0/21`	`123.128.112.1` to `123.128.119.254`	123.128.119.255	2,046
16	`123.128.120.0/21`	`123.128.120.1` to `123.128.127.254`	123.128.127.255	2,046
17	`123.128.128.0/21`	`123.128.128.1` to `123.128.135.254`	123.128.135.255	2,046
18	`123.128.136.0/21`	`123.128.136.1` to `123.128.143.254`	123.128.143.255	2,046
19	`123.128.144.0/21`	`123.128.144.1` to `123.128.151.254`	123.128.151.255	2,046
20	`123.128.152.0/21`	`123.128.152.1` to `123.128.159.254`	123.128.159.255	2,046
21	`123.128.160.0/21`	`123.128.160.1` to `123.128.167.254`	123.128.167.255	2,046
22	`123.128.168.0/21`	`123.128.168.1` to `123.128.175.254`	123.128.175.255	2,046
23	`123.128.176.0/21`	`123.128.176.1` to `123.128.183.254`	123.128.183.255	2,046
24	`123.128.184.0/21`	`123.128.184.1` to `123.128.191.254`	123.128.191.255	2,046
25	`123.128.192.0/21`	`123.128.192.1` to `123.128.199.254`	123.128.199.255	2,046
26	`123.128.200.0/21`	`123.128.200.1` to `123.128.207.254`	123.128.207.255	2,046
27	`123.128.208.0/21`	`123.128.208.1` to `123.128.215.254`	123.128.215.255	2,046
28	`123.128.216.0/21`	`123.128.216.1` to `123.128.223.254`	123.128.223.255	2,046
29	`123.128.224.0/21`	`123.128.224.1` to `123.128.231.254`	123.128.231.255	2,046
30	`123.128.232.0/21`	`123.128.232.1` to `123.128.239.254`	123.128.239.255	2,046
31	`123.128.240.0/21`	`123.128.240.1` to `123.128.247.254`	123.128.247.255	2,046
32	`123.128.248.0/21`	`123.128.248.1` to `123.128.255.254`	123.128.255.255	2,046
33	`123.129.0.0/21`	`123.129.0.1` to `123.129.7.254`	123.129.7.255	2,046
34	`123.129.8.0/21`	`123.129.8.1` to `123.129.15.254`	123.129.15.255	2,046
35	`123.129.16.0/21`	`123.129.16.1` to `123.129.23.254`	123.129.23.255	2,046
36	`123.129.24.0/21`	`123.129.24.1` to `123.129.31.254`	123.129.31.255	2,046
37	`123.129.32.0/21`	`123.129.32.1` to `123.129.39.254`	123.129.39.255	2,046
38	`123.129.40.0/21`	`123.129.40.1` to `123.129.47.254`	123.129.47.255	2,046
39	`123.129.48.0/21`	`123.129.48.1` to `123.129.55.254`	123.129.55.255	2,046
40	`123.129.56.0/21`	`123.129.56.1` to `123.129.63.254`	123.129.63.255	2,046
41	`123.129.64.0/21`	`123.129.64.1` to `123.129.71.254`	123.129.71.255	2,046
42	`123.129.72.0/21`	`123.129.72.1` to `123.129.79.254`	123.129.79.255	2,046
43	`123.129.80.0/21`	`123.129.80.1` to `123.129.87.254`	123.129.87.255	2,046
44	`123.129.88.0/21`	`123.129.88.1` to `123.129.95.254`	123.129.95.255	2,046
45	`123.129.96.0/21`	`123.129.96.1` to `123.129.103.254`	123.129.103.255	2,046
46	`123.129.104.0/21`	`123.129.104.1` to `123.129.111.254`	123.129.111.255	2,046
47	`123.129.112.0/21`	`123.129.112.1` to `123.129.119.254`	123.129.119.255	2,046
48	`123.129.120.0/21`	`123.129.120.1` to `123.129.127.254`	123.129.127.255	2,046
49	`123.129.128.0/21`	`123.129.128.1` to `123.129.135.254`	123.129.135.255	2,046
50	`123.129.136.0/21`	`123.129.136.1` to `123.129.143.254`	123.129.143.255	2,046
51	`123.129.144.0/21`	`123.129.144.1` to `123.129.151.254`	123.129.151.255	2,046
52	`123.129.152.0/21`	`123.129.152.1` to `123.129.159.254`	123.129.159.255	2,046
53	`123.129.160.0/21`	`123.129.160.1` to `123.129.167.254`	123.129.167.255	2,046
54	`123.129.168.0/21`	`123.129.168.1` to `123.129.175.254`	123.129.175.255	2,046
55	`123.129.176.0/21`	`123.129.176.1` to `123.129.183.254`	123.129.183.255	2,046
56	`123.129.184.0/21`	`123.129.184.1` to `123.129.191.254`	123.129.191.255	2,046
57	`123.129.192.0/21`	`123.129.192.1` to `123.129.199.254`	123.129.199.255	2,046
58	`123.129.200.0/21`	`123.129.200.1` to `123.129.207.254`	123.129.207.255	2,046
59	`123.129.208.0/21`	`123.129.208.1` to `123.129.215.254`	123.129.215.255	2,046
60	`123.129.216.0/21`	`123.129.216.1` to `123.129.223.254`	123.129.223.255	2,046
61	`123.129.224.0/21`	`123.129.224.1` to `123.129.231.254`	123.129.231.255	2,046
62	`123.129.232.0/21`	`123.129.232.1` to `123.129.239.254`	123.129.239.255	2,046
63	`123.129.240.0/21`	`123.129.240.1` to `123.129.247.254`	123.129.247.255	2,046
64	`123.129.248.0/21`	`123.129.248.1` to `123.129.255.254`	123.129.255.255	2,046
65	`123.130.0.0/21`	`123.130.0.1` to `123.130.7.254`	123.130.7.255	2,046
66	`123.130.8.0/21`	`123.130.8.1` to `123.130.15.254`	123.130.15.255	2,046
67	`123.130.16.0/21`	`123.130.16.1` to `123.130.23.254`	123.130.23.255	2,046
68	`123.130.24.0/21`	`123.130.24.1` to `123.130.31.254`	123.130.31.255	2,046
69	`123.130.32.0/21`	`123.130.32.1` to `123.130.39.254`	123.130.39.255	2,046
70	`123.130.40.0/21`	`123.130.40.1` to `123.130.47.254`	123.130.47.255	2,046
71	`123.130.48.0/21`	`123.130.48.1` to `123.130.55.254`	123.130.55.255	2,046
72	`123.130.56.0/21`	`123.130.56.1` to `123.130.63.254`	123.130.63.255	2,046
73	`123.130.64.0/21`	`123.130.64.1` to `123.130.71.254`	123.130.71.255	2,046
74	`123.130.72.0/21`	`123.130.72.1` to `123.130.79.254`	123.130.79.255	2,046
75	`123.130.80.0/21`	`123.130.80.1` to `123.130.87.254`	123.130.87.255	2,046
76	`123.130.88.0/21`	`123.130.88.1` to `123.130.95.254`	123.130.95.255	2,046
77	`123.130.96.0/21`	`123.130.96.1` to `123.130.103.254`	123.130.103.255	2,046
78	`123.130.104.0/21`	`123.130.104.1` to `123.130.111.254`	123.130.111.255	2,046
79	`123.130.112.0/21`	`123.130.112.1` to `123.130.119.254`	123.130.119.255	2,046
80	`123.130.120.0/21`	`123.130.120.1` to `123.130.127.254`	123.130.127.255	2,046
81	`123.130.128.0/21`	`123.130.128.1` to `123.130.135.254`	123.130.135.255	2,046
82	`123.130.136.0/21`	`123.130.136.1` to `123.130.143.254`	123.130.143.255	2,046
83	`123.130.144.0/21`	`123.130.144.1` to `123.130.151.254`	123.130.151.255	2,046
84	`123.130.152.0/21`	`123.130.152.1` to `123.130.159.254`	123.130.159.255	2,046
85	`123.130.160.0/21`	`123.130.160.1` to `123.130.167.254`	123.130.167.255	2,046
86	`123.130.168.0/21`	`123.130.168.1` to `123.130.175.254`	123.130.175.255	2,046
87	`123.130.176.0/21`	`123.130.176.1` to `123.130.183.254`	123.130.183.255	2,046
88	`123.130.184.0/21`	`123.130.184.1` to `123.130.191.254`	123.130.191.255	2,046
89	`123.130.192.0/21`	`123.130.192.1` to `123.130.199.254`	123.130.199.255	2,046
90	`123.130.200.0/21`	`123.130.200.1` to `123.130.207.254`	123.130.207.255	2,046
91	`123.130.208.0/21`	`123.130.208.1` to `123.130.215.254`	123.130.215.255	2,046
92	`123.130.216.0/21`	`123.130.216.1` to `123.130.223.254`	123.130.223.255	2,046
93	`123.130.224.0/21`	`123.130.224.1` to `123.130.231.254`	123.130.231.255	2,046
94	`123.130.232.0/21`	`123.130.232.1` to `123.130.239.254`	123.130.239.255	2,046
95	`123.130.240.0/21`	`123.130.240.1` to `123.130.247.254`	123.130.247.255	2,046
96	`123.130.248.0/21`	`123.130.248.1` to `123.130.255.254`	123.130.255.255	2,046
97	`123.131.0.0/21`	`123.131.0.1` to `123.131.7.254`	123.131.7.255	2,046
98	`123.131.8.0/21`	`123.131.8.1` to `123.131.15.254`	123.131.15.255	2,046
99	`123.131.16.0/21`	`123.131.16.1` to `123.131.23.254`	123.131.23.255	2,046
100	`123.131.24.0/21`	`123.131.24.1` to `123.131.31.254`	123.131.31.255	2,046
101	`123.131.32.0/21`	`123.131.32.1` to `123.131.39.254`	123.131.39.255	2,046
102	`123.131.40.0/21`	`123.131.40.1` to `123.131.47.254`	123.131.47.255	2,046
103	`123.131.48.0/21`	`123.131.48.1` to `123.131.55.254`	123.131.55.255	2,046
104	`123.131.56.0/21`	`123.131.56.1` to `123.131.63.254`	123.131.63.255	2,046
105	`123.131.64.0/21`	`123.131.64.1` to `123.131.71.254`	123.131.71.255	2,046
106	`123.131.72.0/21`	`123.131.72.1` to `123.131.79.254`	123.131.79.255	2,046
107	`123.131.80.0/21`	`123.131.80.1` to `123.131.87.254`	123.131.87.255	2,046
108	`123.131.88.0/21`	`123.131.88.1` to `123.131.95.254`	123.131.95.255	2,046
109	`123.131.96.0/21`	`123.131.96.1` to `123.131.103.254`	123.131.103.255	2,046
110	`123.131.104.0/21`	`123.131.104.1` to `123.131.111.254`	123.131.111.255	2,046
111	`123.131.112.0/21`	`123.131.112.1` to `123.131.119.254`	123.131.119.255	2,046
112	`123.131.120.0/21`	`123.131.120.1` to `123.131.127.254`	123.131.127.255	2,046
113	`123.131.128.0/21`	`123.131.128.1` to `123.131.135.254`	123.131.135.255	2,046
114	`123.131.136.0/21`	`123.131.136.1` to `123.131.143.254`	123.131.143.255	2,046
115	`123.131.144.0/21`	`123.131.144.1` to `123.131.151.254`	123.131.151.255	2,046
116	`123.131.152.0/21`	`123.131.152.1` to `123.131.159.254`	123.131.159.255	2,046
117	`123.131.160.0/21`	`123.131.160.1` to `123.131.167.254`	123.131.167.255	2,046
118	`123.131.168.0/21`	`123.131.168.1` to `123.131.175.254`	123.131.175.255	2,046
119	`123.131.176.0/21`	`123.131.176.1` to `123.131.183.254`	123.131.183.255	2,046
120	`123.131.184.0/21`	`123.131.184.1` to `123.131.191.254`	123.131.191.255	2,046
121	`123.131.192.0/21`	`123.131.192.1` to `123.131.199.254`	123.131.199.255	2,046
122	`123.131.200.0/21`	`123.131.200.1` to `123.131.207.254`	123.131.207.255	2,046
123	`123.131.208.0/21`	`123.131.208.1` to `123.131.215.254`	123.131.215.255	2,046
124	`123.131.216.0/21`	`123.131.216.1` to `123.131.223.254`	123.131.223.255	2,046
125	`123.131.224.0/21`	`123.131.224.1` to `123.131.231.254`	123.131.231.255	2,046
126	`123.131.232.0/21`	`123.131.232.1` to `123.131.239.254`	123.131.239.255	2,046
127	`123.131.240.0/21`	`123.131.240.1` to `123.131.247.254`	123.131.247.255	2,046
128	`123.131.248.0/21`	`123.131.248.1` to `123.131.255.254`	123.131.255.255	2,046
129	`123.132.0.0/21`	`123.132.0.1` to `123.132.7.254`	123.132.7.255	2,046
130	`123.132.8.0/21`	`123.132.8.1` to `123.132.15.254`	123.132.15.255	2,046
131	`123.132.16.0/21`	`123.132.16.1` to `123.132.23.254`	123.132.23.255	2,046
132	`123.132.24.0/21`	`123.132.24.1` to `123.132.31.254`	123.132.31.255	2,046
133	`123.132.32.0/21`	`123.132.32.1` to `123.132.39.254`	123.132.39.255	2,046
134	`123.132.40.0/21`	`123.132.40.1` to `123.132.47.254`	123.132.47.255	2,046
135	`123.132.48.0/21`	`123.132.48.1` to `123.132.55.254`	123.132.55.255	2,046
136	`123.132.56.0/21`	`123.132.56.1` to `123.132.63.254`	123.132.63.255	2,046
137	`123.132.64.0/21`	`123.132.64.1` to `123.132.71.254`	123.132.71.255	2,046
138	`123.132.72.0/21`	`123.132.72.1` to `123.132.79.254`	123.132.79.255	2,046
139	`123.132.80.0/21`	`123.132.80.1` to `123.132.87.254`	123.132.87.255	2,046
140	`123.132.88.0/21`	`123.132.88.1` to `123.132.95.254`	123.132.95.255	2,046
141	`123.132.96.0/21`	`123.132.96.1` to `123.132.103.254`	123.132.103.255	2,046
142	`123.132.104.0/21`	`123.132.104.1` to `123.132.111.254`	123.132.111.255	2,046
143	`123.132.112.0/21`	`123.132.112.1` to `123.132.119.254`	123.132.119.255	2,046
144	`123.132.120.0/21`	`123.132.120.1` to `123.132.127.254`	123.132.127.255	2,046
145	`123.132.128.0/21`	`123.132.128.1` to `123.132.135.254`	123.132.135.255	2,046
146	`123.132.136.0/21`	`123.132.136.1` to `123.132.143.254`	123.132.143.255	2,046
147	`123.132.144.0/21`	`123.132.144.1` to `123.132.151.254`	123.132.151.255	2,046
148	`123.132.152.0/21`	`123.132.152.1` to `123.132.159.254`	123.132.159.255	2,046
149	`123.132.160.0/21`	`123.132.160.1` to `123.132.167.254`	123.132.167.255	2,046
150	`123.132.168.0/21`	`123.132.168.1` to `123.132.175.254`	123.132.175.255	2,046
151	`123.132.176.0/21`	`123.132.176.1` to `123.132.183.254`	123.132.183.255	2,046
152	`123.132.184.0/21`	`123.132.184.1` to `123.132.191.254`	123.132.191.255	2,046
153	`123.132.192.0/21`	`123.132.192.1` to `123.132.199.254`	123.132.199.255	2,046
154	`123.132.200.0/21`	`123.132.200.1` to `123.132.207.254`	123.132.207.255	2,046
155	`123.132.208.0/21`	`123.132.208.1` to `123.132.215.254`	123.132.215.255	2,046
156	`123.132.216.0/21`	`123.132.216.1` to `123.132.223.254`	123.132.223.255	2,046
157	`123.132.224.0/21`	`123.132.224.1` to `123.132.231.254`	123.132.231.255	2,046
158	`123.132.232.0/21`	`123.132.232.1` to `123.132.239.254`	123.132.239.255	2,046
159	`123.132.240.0/21`	`123.132.240.1` to `123.132.247.254`	123.132.247.255	2,046
160	`123.132.248.0/21`	`123.132.248.1` to `123.132.255.254`	123.132.255.255	2,046
161	`123.133.0.0/21`	`123.133.0.1` to `123.133.7.254`	123.133.7.255	2,046
162	`123.133.8.0/21`	`123.133.8.1` to `123.133.15.254`	123.133.15.255	2,046
163	`123.133.16.0/21`	`123.133.16.1` to `123.133.23.254`	123.133.23.255	2,046
164	`123.133.24.0/21`	`123.133.24.1` to `123.133.31.254`	123.133.31.255	2,046
165	`123.133.32.0/21`	`123.133.32.1` to `123.133.39.254`	123.133.39.255	2,046
166	`123.133.40.0/21`	`123.133.40.1` to `123.133.47.254`	123.133.47.255	2,046
167	`123.133.48.0/21`	`123.133.48.1` to `123.133.55.254`	123.133.55.255	2,046
168	`123.133.56.0/21`	`123.133.56.1` to `123.133.63.254`	123.133.63.255	2,046
169	`123.133.64.0/21`	`123.133.64.1` to `123.133.71.254`	123.133.71.255	2,046
170	`123.133.72.0/21`	`123.133.72.1` to `123.133.79.254`	123.133.79.255	2,046
171	`123.133.80.0/21`	`123.133.80.1` to `123.133.87.254`	123.133.87.255	2,046
172	`123.133.88.0/21`	`123.133.88.1` to `123.133.95.254`	123.133.95.255	2,046
173	`123.133.96.0/21`	`123.133.96.1` to `123.133.103.254`	123.133.103.255	2,046
174	`123.133.104.0/21`	`123.133.104.1` to `123.133.111.254`	123.133.111.255	2,046
175	`123.133.112.0/21`	`123.133.112.1` to `123.133.119.254`	123.133.119.255	2,046
176	`123.133.120.0/21`	`123.133.120.1` to `123.133.127.254`	123.133.127.255	2,046
177	`123.133.128.0/21`	`123.133.128.1` to `123.133.135.254`	123.133.135.255	2,046
178	`123.133.136.0/21`	`123.133.136.1` to `123.133.143.254`	123.133.143.255	2,046
179	`123.133.144.0/21`	`123.133.144.1` to `123.133.151.254`	123.133.151.255	2,046
180	`123.133.152.0/21`	`123.133.152.1` to `123.133.159.254`	123.133.159.255	2,046
181	`123.133.160.0/21`	`123.133.160.1` to `123.133.167.254`	123.133.167.255	2,046
182	`123.133.168.0/21`	`123.133.168.1` to `123.133.175.254`	123.133.175.255	2,046
183	`123.133.176.0/21`	`123.133.176.1` to `123.133.183.254`	123.133.183.255	2,046
184	`123.133.184.0/21`	`123.133.184.1` to `123.133.191.254`	123.133.191.255	2,046
185	`123.133.192.0/21`	`123.133.192.1` to `123.133.199.254`	123.133.199.255	2,046
186	`123.133.200.0/21`	`123.133.200.1` to `123.133.207.254`	123.133.207.255	2,046
187	`123.133.208.0/21`	`123.133.208.1` to `123.133.215.254`	123.133.215.255	2,046
188	`123.133.216.0/21`	`123.133.216.1` to `123.133.223.254`	123.133.223.255	2,046
189	`123.133.224.0/21`	`123.133.224.1` to `123.133.231.254`	123.133.231.255	2,046
190	`123.133.232.0/21`	`123.133.232.1` to `123.133.239.254`	123.133.239.255	2,046
191	`123.133.240.0/21`	`123.133.240.1` to `123.133.247.254`	123.133.247.255	2,046
192	`123.133.248.0/21`	`123.133.248.1` to `123.133.255.254`	123.133.255.255	2,046
193	`123.134.0.0/21`	`123.134.0.1` to `123.134.7.254`	123.134.7.255	2,046
194	`123.134.8.0/21`	`123.134.8.1` to `123.134.15.254`	123.134.15.255	2,046
195	`123.134.16.0/21`	`123.134.16.1` to `123.134.23.254`	123.134.23.255	2,046
196	`123.134.24.0/21`	`123.134.24.1` to `123.134.31.254`	123.134.31.255	2,046
197	`123.134.32.0/21`	`123.134.32.1` to `123.134.39.254`	123.134.39.255	2,046
198	`123.134.40.0/21`	`123.134.40.1` to `123.134.47.254`	123.134.47.255	2,046
199	`123.134.48.0/21`	`123.134.48.1` to `123.134.55.254`	123.134.55.255	2,046
200	`123.134.56.0/21`	`123.134.56.1` to `123.134.63.254`	123.134.63.255	2,046
201	`123.134.64.0/21`	`123.134.64.1` to `123.134.71.254`	123.134.71.255	2,046
202	`123.134.72.0/21`	`123.134.72.1` to `123.134.79.254`	123.134.79.255	2,046
203	`123.134.80.0/21`	`123.134.80.1` to `123.134.87.254`	123.134.87.255	2,046
204	`123.134.88.0/21`	`123.134.88.1` to `123.134.95.254`	123.134.95.255	2,046
205	`123.134.96.0/21`	`123.134.96.1` to `123.134.103.254`	123.134.103.255	2,046
206	`123.134.104.0/21`	`123.134.104.1` to `123.134.111.254`	123.134.111.255	2,046
207	`123.134.112.0/21`	`123.134.112.1` to `123.134.119.254`	123.134.119.255	2,046
208	`123.134.120.0/21`	`123.134.120.1` to `123.134.127.254`	123.134.127.255	2,046
209	`123.134.128.0/21`	`123.134.128.1` to `123.134.135.254`	123.134.135.255	2,046
210	`123.134.136.0/21`	`123.134.136.1` to `123.134.143.254`	123.134.143.255	2,046
211	`123.134.144.0/21`	`123.134.144.1` to `123.134.151.254`	123.134.151.255	2,046
212	`123.134.152.0/21`	`123.134.152.1` to `123.134.159.254`	123.134.159.255	2,046
213	`123.134.160.0/21`	`123.134.160.1` to `123.134.167.254`	123.134.167.255	2,046
214	`123.134.168.0/21`	`123.134.168.1` to `123.134.175.254`	123.134.175.255	2,046
215	`123.134.176.0/21`	`123.134.176.1` to `123.134.183.254`	123.134.183.255	2,046
216	`123.134.184.0/21`	`123.134.184.1` to `123.134.191.254`	123.134.191.255	2,046
217	`123.134.192.0/21`	`123.134.192.1` to `123.134.199.254`	123.134.199.255	2,046
218	`123.134.200.0/21`	`123.134.200.1` to `123.134.207.254`	123.134.207.255	2,046
219	`123.134.208.0/21`	`123.134.208.1` to `123.134.215.254`	123.134.215.255	2,046
220	`123.134.216.0/21`	`123.134.216.1` to `123.134.223.254`	123.134.223.255	2,046
221	`123.134.224.0/21`	`123.134.224.1` to `123.134.231.254`	123.134.231.255	2,046
222	`123.134.232.0/21`	`123.134.232.1` to `123.134.239.254`	123.134.239.255	2,046
223	`123.134.240.0/21`	`123.134.240.1` to `123.134.247.254`	123.134.247.255	2,046
224	`123.134.248.0/21`	`123.134.248.1` to `123.134.255.254`	123.134.255.255	2,046
225	`123.135.0.0/21`	`123.135.0.1` to `123.135.7.254`	123.135.7.255	2,046
226	`123.135.8.0/21`	`123.135.8.1` to `123.135.15.254`	123.135.15.255	2,046
227	`123.135.16.0/21`	`123.135.16.1` to `123.135.23.254`	123.135.23.255	2,046
228	`123.135.24.0/21`	`123.135.24.1` to `123.135.31.254`	123.135.31.255	2,046
229	`123.135.32.0/21`	`123.135.32.1` to `123.135.39.254`	123.135.39.255	2,046
230	`123.135.40.0/21`	`123.135.40.1` to `123.135.47.254`	123.135.47.255	2,046
231	`123.135.48.0/21`	`123.135.48.1` to `123.135.55.254`	123.135.55.255	2,046
232	`123.135.56.0/21`	`123.135.56.1` to `123.135.63.254`	123.135.63.255	2,046
233	`123.135.64.0/21`	`123.135.64.1` to `123.135.71.254`	123.135.71.255	2,046
234	`123.135.72.0/21`	`123.135.72.1` to `123.135.79.254`	123.135.79.255	2,046
235	`123.135.80.0/21`	`123.135.80.1` to `123.135.87.254`	123.135.87.255	2,046
236	`123.135.88.0/21`	`123.135.88.1` to `123.135.95.254`	123.135.95.255	2,046
237	`123.135.96.0/21`	`123.135.96.1` to `123.135.103.254`	123.135.103.255	2,046
238	`123.135.104.0/21`	`123.135.104.1` to `123.135.111.254`	123.135.111.255	2,046
239	`123.135.112.0/21`	`123.135.112.1` to `123.135.119.254`	123.135.119.255	2,046
240	`123.135.120.0/21`	`123.135.120.1` to `123.135.127.254`	123.135.127.255	2,046
241	`123.135.128.0/21`	`123.135.128.1` to `123.135.135.254`	123.135.135.255	2,046
242	`123.135.136.0/21`	`123.135.136.1` to `123.135.143.254`	123.135.143.255	2,046
243	`123.135.144.0/21`	`123.135.144.1` to `123.135.151.254`	123.135.151.255	2,046
244	`123.135.152.0/21`	`123.135.152.1` to `123.135.159.254`	123.135.159.255	2,046
245	`123.135.160.0/21`	`123.135.160.1` to `123.135.167.254`	123.135.167.255	2,046
246	`123.135.168.0/21`	`123.135.168.1` to `123.135.175.254`	123.135.175.255	2,046
247	`123.135.176.0/21`	`123.135.176.1` to `123.135.183.254`	123.135.183.255	2,046
248	`123.135.184.0/21`	`123.135.184.1` to `123.135.191.254`	123.135.191.255	2,046
249	`123.135.192.0/21`	`123.135.192.1` to `123.135.199.254`	123.135.199.255	2,046
250	`123.135.200.0/21`	`123.135.200.1` to `123.135.207.254`	123.135.207.255	2,046
251	`123.135.208.0/21`	`123.135.208.1` to `123.135.215.254`	123.135.215.255	2,046
252	`123.135.216.0/21`	`123.135.216.1` to `123.135.223.254`	123.135.223.255	2,046
253	`123.135.224.0/21`	`123.135.224.1` to `123.135.231.254`	123.135.231.255	2,046
254	`123.135.232.0/21`	`123.135.232.1` to `123.135.239.254`	123.135.239.255	2,046
255	`123.135.240.0/21`	`123.135.240.1` to `123.135.247.254`	123.135.247.255	2,046
256	`123.135.248.0/21`	`123.135.248.1` to `123.135.255.254`	123.135.255.255	2,046

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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