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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.

Network217.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
217.128.0.0
Broadcast address
217.255.255.255
First usable
217.128.0.1
Last usable
217.255.255.254
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
C (default /24)
As numbers
Hex D9800000 · Integer 3649044480 to 3657433087
Reverse DNS zones
128.217.in-addr.arpa
129.217.in-addr.arpa
130.217.in-addr.arpa
131.217.in-addr.arpa
132.217.in-addr.arpa
133.217.in-addr.arpa
134.217.in-addr.arpa
135.217.in-addr.arpa
136.217.in-addr.arpa
137.217.in-addr.arpa
138.217.in-addr.arpa
139.217.in-addr.arpa
140.217.in-addr.arpa
141.217.in-addr.arpa
142.217.in-addr.arpa
143.217.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
Address11011001.10000000.00000000.00000000217.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network11011001.10000000.00000000.00000000217.128.0.0
Broadcast11011001.11111111.11111111.11111111217.255.255.255
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)

217.128.0.0/9 makes 4,096 subnets of /21; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1217.128.0.0/21217.128.0.1 to 217.128.7.254217.128.7.2552,046
2217.128.8.0/21217.128.8.1 to 217.128.15.254217.128.15.2552,046
3217.128.16.0/21217.128.16.1 to 217.128.23.254217.128.23.2552,046
4217.128.24.0/21217.128.24.1 to 217.128.31.254217.128.31.2552,046
5217.128.32.0/21217.128.32.1 to 217.128.39.254217.128.39.2552,046
6217.128.40.0/21217.128.40.1 to 217.128.47.254217.128.47.2552,046
7217.128.48.0/21217.128.48.1 to 217.128.55.254217.128.55.2552,046
8217.128.56.0/21217.128.56.1 to 217.128.63.254217.128.63.2552,046
9217.128.64.0/21217.128.64.1 to 217.128.71.254217.128.71.2552,046
10217.128.72.0/21217.128.72.1 to 217.128.79.254217.128.79.2552,046
11217.128.80.0/21217.128.80.1 to 217.128.87.254217.128.87.2552,046
12217.128.88.0/21217.128.88.1 to 217.128.95.254217.128.95.2552,046
13217.128.96.0/21217.128.96.1 to 217.128.103.254217.128.103.2552,046
14217.128.104.0/21217.128.104.1 to 217.128.111.254217.128.111.2552,046
15217.128.112.0/21217.128.112.1 to 217.128.119.254217.128.119.2552,046
16217.128.120.0/21217.128.120.1 to 217.128.127.254217.128.127.2552,046
17217.128.128.0/21217.128.128.1 to 217.128.135.254217.128.135.2552,046
18217.128.136.0/21217.128.136.1 to 217.128.143.254217.128.143.2552,046
19217.128.144.0/21217.128.144.1 to 217.128.151.254217.128.151.2552,046
20217.128.152.0/21217.128.152.1 to 217.128.159.254217.128.159.2552,046
21217.128.160.0/21217.128.160.1 to 217.128.167.254217.128.167.2552,046
22217.128.168.0/21217.128.168.1 to 217.128.175.254217.128.175.2552,046
23217.128.176.0/21217.128.176.1 to 217.128.183.254217.128.183.2552,046
24217.128.184.0/21217.128.184.1 to 217.128.191.254217.128.191.2552,046
25217.128.192.0/21217.128.192.1 to 217.128.199.254217.128.199.2552,046
26217.128.200.0/21217.128.200.1 to 217.128.207.254217.128.207.2552,046
27217.128.208.0/21217.128.208.1 to 217.128.215.254217.128.215.2552,046
28217.128.216.0/21217.128.216.1 to 217.128.223.254217.128.223.2552,046
29217.128.224.0/21217.128.224.1 to 217.128.231.254217.128.231.2552,046
30217.128.232.0/21217.128.232.1 to 217.128.239.254217.128.239.2552,046
31217.128.240.0/21217.128.240.1 to 217.128.247.254217.128.247.2552,046
32217.128.248.0/21217.128.248.1 to 217.128.255.254217.128.255.2552,046
33217.129.0.0/21217.129.0.1 to 217.129.7.254217.129.7.2552,046
34217.129.8.0/21217.129.8.1 to 217.129.15.254217.129.15.2552,046
35217.129.16.0/21217.129.16.1 to 217.129.23.254217.129.23.2552,046
36217.129.24.0/21217.129.24.1 to 217.129.31.254217.129.31.2552,046
37217.129.32.0/21217.129.32.1 to 217.129.39.254217.129.39.2552,046
38217.129.40.0/21217.129.40.1 to 217.129.47.254217.129.47.2552,046
39217.129.48.0/21217.129.48.1 to 217.129.55.254217.129.55.2552,046
40217.129.56.0/21217.129.56.1 to 217.129.63.254217.129.63.2552,046
41217.129.64.0/21217.129.64.1 to 217.129.71.254217.129.71.2552,046
42217.129.72.0/21217.129.72.1 to 217.129.79.254217.129.79.2552,046
43217.129.80.0/21217.129.80.1 to 217.129.87.254217.129.87.2552,046
44217.129.88.0/21217.129.88.1 to 217.129.95.254217.129.95.2552,046
45217.129.96.0/21217.129.96.1 to 217.129.103.254217.129.103.2552,046
46217.129.104.0/21217.129.104.1 to 217.129.111.254217.129.111.2552,046
47217.129.112.0/21217.129.112.1 to 217.129.119.254217.129.119.2552,046
48217.129.120.0/21217.129.120.1 to 217.129.127.254217.129.127.2552,046
49217.129.128.0/21217.129.128.1 to 217.129.135.254217.129.135.2552,046
50217.129.136.0/21217.129.136.1 to 217.129.143.254217.129.143.2552,046
51217.129.144.0/21217.129.144.1 to 217.129.151.254217.129.151.2552,046
52217.129.152.0/21217.129.152.1 to 217.129.159.254217.129.159.2552,046
53217.129.160.0/21217.129.160.1 to 217.129.167.254217.129.167.2552,046
54217.129.168.0/21217.129.168.1 to 217.129.175.254217.129.175.2552,046
55217.129.176.0/21217.129.176.1 to 217.129.183.254217.129.183.2552,046
56217.129.184.0/21217.129.184.1 to 217.129.191.254217.129.191.2552,046
57217.129.192.0/21217.129.192.1 to 217.129.199.254217.129.199.2552,046
58217.129.200.0/21217.129.200.1 to 217.129.207.254217.129.207.2552,046
59217.129.208.0/21217.129.208.1 to 217.129.215.254217.129.215.2552,046
60217.129.216.0/21217.129.216.1 to 217.129.223.254217.129.223.2552,046
61217.129.224.0/21217.129.224.1 to 217.129.231.254217.129.231.2552,046
62217.129.232.0/21217.129.232.1 to 217.129.239.254217.129.239.2552,046
63217.129.240.0/21217.129.240.1 to 217.129.247.254217.129.247.2552,046
64217.129.248.0/21217.129.248.1 to 217.129.255.254217.129.255.2552,046
65217.130.0.0/21217.130.0.1 to 217.130.7.254217.130.7.2552,046
66217.130.8.0/21217.130.8.1 to 217.130.15.254217.130.15.2552,046
67217.130.16.0/21217.130.16.1 to 217.130.23.254217.130.23.2552,046
68217.130.24.0/21217.130.24.1 to 217.130.31.254217.130.31.2552,046
69217.130.32.0/21217.130.32.1 to 217.130.39.254217.130.39.2552,046
70217.130.40.0/21217.130.40.1 to 217.130.47.254217.130.47.2552,046
71217.130.48.0/21217.130.48.1 to 217.130.55.254217.130.55.2552,046
72217.130.56.0/21217.130.56.1 to 217.130.63.254217.130.63.2552,046
73217.130.64.0/21217.130.64.1 to 217.130.71.254217.130.71.2552,046
74217.130.72.0/21217.130.72.1 to 217.130.79.254217.130.79.2552,046
75217.130.80.0/21217.130.80.1 to 217.130.87.254217.130.87.2552,046
76217.130.88.0/21217.130.88.1 to 217.130.95.254217.130.95.2552,046
77217.130.96.0/21217.130.96.1 to 217.130.103.254217.130.103.2552,046
78217.130.104.0/21217.130.104.1 to 217.130.111.254217.130.111.2552,046
79217.130.112.0/21217.130.112.1 to 217.130.119.254217.130.119.2552,046
80217.130.120.0/21217.130.120.1 to 217.130.127.254217.130.127.2552,046
81217.130.128.0/21217.130.128.1 to 217.130.135.254217.130.135.2552,046
82217.130.136.0/21217.130.136.1 to 217.130.143.254217.130.143.2552,046
83217.130.144.0/21217.130.144.1 to 217.130.151.254217.130.151.2552,046
84217.130.152.0/21217.130.152.1 to 217.130.159.254217.130.159.2552,046
85217.130.160.0/21217.130.160.1 to 217.130.167.254217.130.167.2552,046
86217.130.168.0/21217.130.168.1 to 217.130.175.254217.130.175.2552,046
87217.130.176.0/21217.130.176.1 to 217.130.183.254217.130.183.2552,046
88217.130.184.0/21217.130.184.1 to 217.130.191.254217.130.191.2552,046
89217.130.192.0/21217.130.192.1 to 217.130.199.254217.130.199.2552,046
90217.130.200.0/21217.130.200.1 to 217.130.207.254217.130.207.2552,046
91217.130.208.0/21217.130.208.1 to 217.130.215.254217.130.215.2552,046
92217.130.216.0/21217.130.216.1 to 217.130.223.254217.130.223.2552,046
93217.130.224.0/21217.130.224.1 to 217.130.231.254217.130.231.2552,046
94217.130.232.0/21217.130.232.1 to 217.130.239.254217.130.239.2552,046
95217.130.240.0/21217.130.240.1 to 217.130.247.254217.130.247.2552,046
96217.130.248.0/21217.130.248.1 to 217.130.255.254217.130.255.2552,046
97217.131.0.0/21217.131.0.1 to 217.131.7.254217.131.7.2552,046
98217.131.8.0/21217.131.8.1 to 217.131.15.254217.131.15.2552,046
99217.131.16.0/21217.131.16.1 to 217.131.23.254217.131.23.2552,046
100217.131.24.0/21217.131.24.1 to 217.131.31.254217.131.31.2552,046
101217.131.32.0/21217.131.32.1 to 217.131.39.254217.131.39.2552,046
102217.131.40.0/21217.131.40.1 to 217.131.47.254217.131.47.2552,046
103217.131.48.0/21217.131.48.1 to 217.131.55.254217.131.55.2552,046
104217.131.56.0/21217.131.56.1 to 217.131.63.254217.131.63.2552,046
105217.131.64.0/21217.131.64.1 to 217.131.71.254217.131.71.2552,046
106217.131.72.0/21217.131.72.1 to 217.131.79.254217.131.79.2552,046
107217.131.80.0/21217.131.80.1 to 217.131.87.254217.131.87.2552,046
108217.131.88.0/21217.131.88.1 to 217.131.95.254217.131.95.2552,046
109217.131.96.0/21217.131.96.1 to 217.131.103.254217.131.103.2552,046
110217.131.104.0/21217.131.104.1 to 217.131.111.254217.131.111.2552,046
111217.131.112.0/21217.131.112.1 to 217.131.119.254217.131.119.2552,046
112217.131.120.0/21217.131.120.1 to 217.131.127.254217.131.127.2552,046
113217.131.128.0/21217.131.128.1 to 217.131.135.254217.131.135.2552,046
114217.131.136.0/21217.131.136.1 to 217.131.143.254217.131.143.2552,046
115217.131.144.0/21217.131.144.1 to 217.131.151.254217.131.151.2552,046
116217.131.152.0/21217.131.152.1 to 217.131.159.254217.131.159.2552,046
117217.131.160.0/21217.131.160.1 to 217.131.167.254217.131.167.2552,046
118217.131.168.0/21217.131.168.1 to 217.131.175.254217.131.175.2552,046
119217.131.176.0/21217.131.176.1 to 217.131.183.254217.131.183.2552,046
120217.131.184.0/21217.131.184.1 to 217.131.191.254217.131.191.2552,046
121217.131.192.0/21217.131.192.1 to 217.131.199.254217.131.199.2552,046
122217.131.200.0/21217.131.200.1 to 217.131.207.254217.131.207.2552,046
123217.131.208.0/21217.131.208.1 to 217.131.215.254217.131.215.2552,046
124217.131.216.0/21217.131.216.1 to 217.131.223.254217.131.223.2552,046
125217.131.224.0/21217.131.224.1 to 217.131.231.254217.131.231.2552,046
126217.131.232.0/21217.131.232.1 to 217.131.239.254217.131.239.2552,046
127217.131.240.0/21217.131.240.1 to 217.131.247.254217.131.247.2552,046
128217.131.248.0/21217.131.248.1 to 217.131.255.254217.131.255.2552,046
129217.132.0.0/21217.132.0.1 to 217.132.7.254217.132.7.2552,046
130217.132.8.0/21217.132.8.1 to 217.132.15.254217.132.15.2552,046
131217.132.16.0/21217.132.16.1 to 217.132.23.254217.132.23.2552,046
132217.132.24.0/21217.132.24.1 to 217.132.31.254217.132.31.2552,046
133217.132.32.0/21217.132.32.1 to 217.132.39.254217.132.39.2552,046
134217.132.40.0/21217.132.40.1 to 217.132.47.254217.132.47.2552,046
135217.132.48.0/21217.132.48.1 to 217.132.55.254217.132.55.2552,046
136217.132.56.0/21217.132.56.1 to 217.132.63.254217.132.63.2552,046
137217.132.64.0/21217.132.64.1 to 217.132.71.254217.132.71.2552,046
138217.132.72.0/21217.132.72.1 to 217.132.79.254217.132.79.2552,046
139217.132.80.0/21217.132.80.1 to 217.132.87.254217.132.87.2552,046
140217.132.88.0/21217.132.88.1 to 217.132.95.254217.132.95.2552,046
141217.132.96.0/21217.132.96.1 to 217.132.103.254217.132.103.2552,046
142217.132.104.0/21217.132.104.1 to 217.132.111.254217.132.111.2552,046
143217.132.112.0/21217.132.112.1 to 217.132.119.254217.132.119.2552,046
144217.132.120.0/21217.132.120.1 to 217.132.127.254217.132.127.2552,046
145217.132.128.0/21217.132.128.1 to 217.132.135.254217.132.135.2552,046
146217.132.136.0/21217.132.136.1 to 217.132.143.254217.132.143.2552,046
147217.132.144.0/21217.132.144.1 to 217.132.151.254217.132.151.2552,046
148217.132.152.0/21217.132.152.1 to 217.132.159.254217.132.159.2552,046
149217.132.160.0/21217.132.160.1 to 217.132.167.254217.132.167.2552,046
150217.132.168.0/21217.132.168.1 to 217.132.175.254217.132.175.2552,046
151217.132.176.0/21217.132.176.1 to 217.132.183.254217.132.183.2552,046
152217.132.184.0/21217.132.184.1 to 217.132.191.254217.132.191.2552,046
153217.132.192.0/21217.132.192.1 to 217.132.199.254217.132.199.2552,046
154217.132.200.0/21217.132.200.1 to 217.132.207.254217.132.207.2552,046
155217.132.208.0/21217.132.208.1 to 217.132.215.254217.132.215.2552,046
156217.132.216.0/21217.132.216.1 to 217.132.223.254217.132.223.2552,046
157217.132.224.0/21217.132.224.1 to 217.132.231.254217.132.231.2552,046
158217.132.232.0/21217.132.232.1 to 217.132.239.254217.132.239.2552,046
159217.132.240.0/21217.132.240.1 to 217.132.247.254217.132.247.2552,046
160217.132.248.0/21217.132.248.1 to 217.132.255.254217.132.255.2552,046
161217.133.0.0/21217.133.0.1 to 217.133.7.254217.133.7.2552,046
162217.133.8.0/21217.133.8.1 to 217.133.15.254217.133.15.2552,046
163217.133.16.0/21217.133.16.1 to 217.133.23.254217.133.23.2552,046
164217.133.24.0/21217.133.24.1 to 217.133.31.254217.133.31.2552,046
165217.133.32.0/21217.133.32.1 to 217.133.39.254217.133.39.2552,046
166217.133.40.0/21217.133.40.1 to 217.133.47.254217.133.47.2552,046
167217.133.48.0/21217.133.48.1 to 217.133.55.254217.133.55.2552,046
168217.133.56.0/21217.133.56.1 to 217.133.63.254217.133.63.2552,046
169217.133.64.0/21217.133.64.1 to 217.133.71.254217.133.71.2552,046
170217.133.72.0/21217.133.72.1 to 217.133.79.254217.133.79.2552,046
171217.133.80.0/21217.133.80.1 to 217.133.87.254217.133.87.2552,046
172217.133.88.0/21217.133.88.1 to 217.133.95.254217.133.95.2552,046
173217.133.96.0/21217.133.96.1 to 217.133.103.254217.133.103.2552,046
174217.133.104.0/21217.133.104.1 to 217.133.111.254217.133.111.2552,046
175217.133.112.0/21217.133.112.1 to 217.133.119.254217.133.119.2552,046
176217.133.120.0/21217.133.120.1 to 217.133.127.254217.133.127.2552,046
177217.133.128.0/21217.133.128.1 to 217.133.135.254217.133.135.2552,046
178217.133.136.0/21217.133.136.1 to 217.133.143.254217.133.143.2552,046
179217.133.144.0/21217.133.144.1 to 217.133.151.254217.133.151.2552,046
180217.133.152.0/21217.133.152.1 to 217.133.159.254217.133.159.2552,046
181217.133.160.0/21217.133.160.1 to 217.133.167.254217.133.167.2552,046
182217.133.168.0/21217.133.168.1 to 217.133.175.254217.133.175.2552,046
183217.133.176.0/21217.133.176.1 to 217.133.183.254217.133.183.2552,046
184217.133.184.0/21217.133.184.1 to 217.133.191.254217.133.191.2552,046
185217.133.192.0/21217.133.192.1 to 217.133.199.254217.133.199.2552,046
186217.133.200.0/21217.133.200.1 to 217.133.207.254217.133.207.2552,046
187217.133.208.0/21217.133.208.1 to 217.133.215.254217.133.215.2552,046
188217.133.216.0/21217.133.216.1 to 217.133.223.254217.133.223.2552,046
189217.133.224.0/21217.133.224.1 to 217.133.231.254217.133.231.2552,046
190217.133.232.0/21217.133.232.1 to 217.133.239.254217.133.239.2552,046
191217.133.240.0/21217.133.240.1 to 217.133.247.254217.133.247.2552,046
192217.133.248.0/21217.133.248.1 to 217.133.255.254217.133.255.2552,046
193217.134.0.0/21217.134.0.1 to 217.134.7.254217.134.7.2552,046
194217.134.8.0/21217.134.8.1 to 217.134.15.254217.134.15.2552,046
195217.134.16.0/21217.134.16.1 to 217.134.23.254217.134.23.2552,046
196217.134.24.0/21217.134.24.1 to 217.134.31.254217.134.31.2552,046
197217.134.32.0/21217.134.32.1 to 217.134.39.254217.134.39.2552,046
198217.134.40.0/21217.134.40.1 to 217.134.47.254217.134.47.2552,046
199217.134.48.0/21217.134.48.1 to 217.134.55.254217.134.55.2552,046
200217.134.56.0/21217.134.56.1 to 217.134.63.254217.134.63.2552,046
201217.134.64.0/21217.134.64.1 to 217.134.71.254217.134.71.2552,046
202217.134.72.0/21217.134.72.1 to 217.134.79.254217.134.79.2552,046
203217.134.80.0/21217.134.80.1 to 217.134.87.254217.134.87.2552,046
204217.134.88.0/21217.134.88.1 to 217.134.95.254217.134.95.2552,046
205217.134.96.0/21217.134.96.1 to 217.134.103.254217.134.103.2552,046
206217.134.104.0/21217.134.104.1 to 217.134.111.254217.134.111.2552,046
207217.134.112.0/21217.134.112.1 to 217.134.119.254217.134.119.2552,046
208217.134.120.0/21217.134.120.1 to 217.134.127.254217.134.127.2552,046
209217.134.128.0/21217.134.128.1 to 217.134.135.254217.134.135.2552,046
210217.134.136.0/21217.134.136.1 to 217.134.143.254217.134.143.2552,046
211217.134.144.0/21217.134.144.1 to 217.134.151.254217.134.151.2552,046
212217.134.152.0/21217.134.152.1 to 217.134.159.254217.134.159.2552,046
213217.134.160.0/21217.134.160.1 to 217.134.167.254217.134.167.2552,046
214217.134.168.0/21217.134.168.1 to 217.134.175.254217.134.175.2552,046
215217.134.176.0/21217.134.176.1 to 217.134.183.254217.134.183.2552,046
216217.134.184.0/21217.134.184.1 to 217.134.191.254217.134.191.2552,046
217217.134.192.0/21217.134.192.1 to 217.134.199.254217.134.199.2552,046
218217.134.200.0/21217.134.200.1 to 217.134.207.254217.134.207.2552,046
219217.134.208.0/21217.134.208.1 to 217.134.215.254217.134.215.2552,046
220217.134.216.0/21217.134.216.1 to 217.134.223.254217.134.223.2552,046
221217.134.224.0/21217.134.224.1 to 217.134.231.254217.134.231.2552,046
222217.134.232.0/21217.134.232.1 to 217.134.239.254217.134.239.2552,046
223217.134.240.0/21217.134.240.1 to 217.134.247.254217.134.247.2552,046
224217.134.248.0/21217.134.248.1 to 217.134.255.254217.134.255.2552,046
225217.135.0.0/21217.135.0.1 to 217.135.7.254217.135.7.2552,046
226217.135.8.0/21217.135.8.1 to 217.135.15.254217.135.15.2552,046
227217.135.16.0/21217.135.16.1 to 217.135.23.254217.135.23.2552,046
228217.135.24.0/21217.135.24.1 to 217.135.31.254217.135.31.2552,046
229217.135.32.0/21217.135.32.1 to 217.135.39.254217.135.39.2552,046
230217.135.40.0/21217.135.40.1 to 217.135.47.254217.135.47.2552,046
231217.135.48.0/21217.135.48.1 to 217.135.55.254217.135.55.2552,046
232217.135.56.0/21217.135.56.1 to 217.135.63.254217.135.63.2552,046
233217.135.64.0/21217.135.64.1 to 217.135.71.254217.135.71.2552,046
234217.135.72.0/21217.135.72.1 to 217.135.79.254217.135.79.2552,046
235217.135.80.0/21217.135.80.1 to 217.135.87.254217.135.87.2552,046
236217.135.88.0/21217.135.88.1 to 217.135.95.254217.135.95.2552,046
237217.135.96.0/21217.135.96.1 to 217.135.103.254217.135.103.2552,046
238217.135.104.0/21217.135.104.1 to 217.135.111.254217.135.111.2552,046
239217.135.112.0/21217.135.112.1 to 217.135.119.254217.135.119.2552,046
240217.135.120.0/21217.135.120.1 to 217.135.127.254217.135.127.2552,046
241217.135.128.0/21217.135.128.1 to 217.135.135.254217.135.135.2552,046
242217.135.136.0/21217.135.136.1 to 217.135.143.254217.135.143.2552,046
243217.135.144.0/21217.135.144.1 to 217.135.151.254217.135.151.2552,046
244217.135.152.0/21217.135.152.1 to 217.135.159.254217.135.159.2552,046
245217.135.160.0/21217.135.160.1 to 217.135.167.254217.135.167.2552,046
246217.135.168.0/21217.135.168.1 to 217.135.175.254217.135.175.2552,046
247217.135.176.0/21217.135.176.1 to 217.135.183.254217.135.183.2552,046
248217.135.184.0/21217.135.184.1 to 217.135.191.254217.135.191.2552,046
249217.135.192.0/21217.135.192.1 to 217.135.199.254217.135.199.2552,046
250217.135.200.0/21217.135.200.1 to 217.135.207.254217.135.207.2552,046
251217.135.208.0/21217.135.208.1 to 217.135.215.254217.135.215.2552,046
252217.135.216.0/21217.135.216.1 to 217.135.223.254217.135.223.2552,046
253217.135.224.0/21217.135.224.1 to 217.135.231.254217.135.231.2552,046
254217.135.232.0/21217.135.232.1 to 217.135.239.254217.135.239.2552,046
255217.135.240.0/21217.135.240.1 to 217.135.247.254217.135.247.2552,046
256217.135.248.0/21217.135.248.1 to 217.135.255.254217.135.255.2552,046

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.