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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.

Network243.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
243.128.0.0
Broadcast address
243.255.255.255
First usable
243.128.0.1
Last usable
243.255.255.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F3800000 · Integer 4085252096 to 4093640703
Reverse DNS zones
128.243.in-addr.arpa
129.243.in-addr.arpa
130.243.in-addr.arpa
131.243.in-addr.arpa
132.243.in-addr.arpa
133.243.in-addr.arpa
134.243.in-addr.arpa
135.243.in-addr.arpa
136.243.in-addr.arpa
137.243.in-addr.arpa
138.243.in-addr.arpa
139.243.in-addr.arpa
140.243.in-addr.arpa
141.243.in-addr.arpa
142.243.in-addr.arpa
143.243.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
Address11110011.10000000.00000000.00000000243.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network11110011.10000000.00000000.00000000243.128.0.0
Broadcast11110011.11111111.11111111.11111111243.255.255.255
Split into smaller subnets/17
/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)

243.128.0.0/9 makes 256 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1243.128.0.0/17243.128.0.1 to 243.128.127.254243.128.127.25532,766
2243.128.128.0/17243.128.128.1 to 243.128.255.254243.128.255.25532,766
3243.129.0.0/17243.129.0.1 to 243.129.127.254243.129.127.25532,766
4243.129.128.0/17243.129.128.1 to 243.129.255.254243.129.255.25532,766
5243.130.0.0/17243.130.0.1 to 243.130.127.254243.130.127.25532,766
6243.130.128.0/17243.130.128.1 to 243.130.255.254243.130.255.25532,766
7243.131.0.0/17243.131.0.1 to 243.131.127.254243.131.127.25532,766
8243.131.128.0/17243.131.128.1 to 243.131.255.254243.131.255.25532,766
9243.132.0.0/17243.132.0.1 to 243.132.127.254243.132.127.25532,766
10243.132.128.0/17243.132.128.1 to 243.132.255.254243.132.255.25532,766
11243.133.0.0/17243.133.0.1 to 243.133.127.254243.133.127.25532,766
12243.133.128.0/17243.133.128.1 to 243.133.255.254243.133.255.25532,766
13243.134.0.0/17243.134.0.1 to 243.134.127.254243.134.127.25532,766
14243.134.128.0/17243.134.128.1 to 243.134.255.254243.134.255.25532,766
15243.135.0.0/17243.135.0.1 to 243.135.127.254243.135.127.25532,766
16243.135.128.0/17243.135.128.1 to 243.135.255.254243.135.255.25532,766
17243.136.0.0/17243.136.0.1 to 243.136.127.254243.136.127.25532,766
18243.136.128.0/17243.136.128.1 to 243.136.255.254243.136.255.25532,766
19243.137.0.0/17243.137.0.1 to 243.137.127.254243.137.127.25532,766
20243.137.128.0/17243.137.128.1 to 243.137.255.254243.137.255.25532,766
21243.138.0.0/17243.138.0.1 to 243.138.127.254243.138.127.25532,766
22243.138.128.0/17243.138.128.1 to 243.138.255.254243.138.255.25532,766
23243.139.0.0/17243.139.0.1 to 243.139.127.254243.139.127.25532,766
24243.139.128.0/17243.139.128.1 to 243.139.255.254243.139.255.25532,766
25243.140.0.0/17243.140.0.1 to 243.140.127.254243.140.127.25532,766
26243.140.128.0/17243.140.128.1 to 243.140.255.254243.140.255.25532,766
27243.141.0.0/17243.141.0.1 to 243.141.127.254243.141.127.25532,766
28243.141.128.0/17243.141.128.1 to 243.141.255.254243.141.255.25532,766
29243.142.0.0/17243.142.0.1 to 243.142.127.254243.142.127.25532,766
30243.142.128.0/17243.142.128.1 to 243.142.255.254243.142.255.25532,766
31243.143.0.0/17243.143.0.1 to 243.143.127.254243.143.127.25532,766
32243.143.128.0/17243.143.128.1 to 243.143.255.254243.143.255.25532,766
33243.144.0.0/17243.144.0.1 to 243.144.127.254243.144.127.25532,766
34243.144.128.0/17243.144.128.1 to 243.144.255.254243.144.255.25532,766
35243.145.0.0/17243.145.0.1 to 243.145.127.254243.145.127.25532,766
36243.145.128.0/17243.145.128.1 to 243.145.255.254243.145.255.25532,766
37243.146.0.0/17243.146.0.1 to 243.146.127.254243.146.127.25532,766
38243.146.128.0/17243.146.128.1 to 243.146.255.254243.146.255.25532,766
39243.147.0.0/17243.147.0.1 to 243.147.127.254243.147.127.25532,766
40243.147.128.0/17243.147.128.1 to 243.147.255.254243.147.255.25532,766
41243.148.0.0/17243.148.0.1 to 243.148.127.254243.148.127.25532,766
42243.148.128.0/17243.148.128.1 to 243.148.255.254243.148.255.25532,766
43243.149.0.0/17243.149.0.1 to 243.149.127.254243.149.127.25532,766
44243.149.128.0/17243.149.128.1 to 243.149.255.254243.149.255.25532,766
45243.150.0.0/17243.150.0.1 to 243.150.127.254243.150.127.25532,766
46243.150.128.0/17243.150.128.1 to 243.150.255.254243.150.255.25532,766
47243.151.0.0/17243.151.0.1 to 243.151.127.254243.151.127.25532,766
48243.151.128.0/17243.151.128.1 to 243.151.255.254243.151.255.25532,766
49243.152.0.0/17243.152.0.1 to 243.152.127.254243.152.127.25532,766
50243.152.128.0/17243.152.128.1 to 243.152.255.254243.152.255.25532,766
51243.153.0.0/17243.153.0.1 to 243.153.127.254243.153.127.25532,766
52243.153.128.0/17243.153.128.1 to 243.153.255.254243.153.255.25532,766
53243.154.0.0/17243.154.0.1 to 243.154.127.254243.154.127.25532,766
54243.154.128.0/17243.154.128.1 to 243.154.255.254243.154.255.25532,766
55243.155.0.0/17243.155.0.1 to 243.155.127.254243.155.127.25532,766
56243.155.128.0/17243.155.128.1 to 243.155.255.254243.155.255.25532,766
57243.156.0.0/17243.156.0.1 to 243.156.127.254243.156.127.25532,766
58243.156.128.0/17243.156.128.1 to 243.156.255.254243.156.255.25532,766
59243.157.0.0/17243.157.0.1 to 243.157.127.254243.157.127.25532,766
60243.157.128.0/17243.157.128.1 to 243.157.255.254243.157.255.25532,766
61243.158.0.0/17243.158.0.1 to 243.158.127.254243.158.127.25532,766
62243.158.128.0/17243.158.128.1 to 243.158.255.254243.158.255.25532,766
63243.159.0.0/17243.159.0.1 to 243.159.127.254243.159.127.25532,766
64243.159.128.0/17243.159.128.1 to 243.159.255.254243.159.255.25532,766
65243.160.0.0/17243.160.0.1 to 243.160.127.254243.160.127.25532,766
66243.160.128.0/17243.160.128.1 to 243.160.255.254243.160.255.25532,766
67243.161.0.0/17243.161.0.1 to 243.161.127.254243.161.127.25532,766
68243.161.128.0/17243.161.128.1 to 243.161.255.254243.161.255.25532,766
69243.162.0.0/17243.162.0.1 to 243.162.127.254243.162.127.25532,766
70243.162.128.0/17243.162.128.1 to 243.162.255.254243.162.255.25532,766
71243.163.0.0/17243.163.0.1 to 243.163.127.254243.163.127.25532,766
72243.163.128.0/17243.163.128.1 to 243.163.255.254243.163.255.25532,766
73243.164.0.0/17243.164.0.1 to 243.164.127.254243.164.127.25532,766
74243.164.128.0/17243.164.128.1 to 243.164.255.254243.164.255.25532,766
75243.165.0.0/17243.165.0.1 to 243.165.127.254243.165.127.25532,766
76243.165.128.0/17243.165.128.1 to 243.165.255.254243.165.255.25532,766
77243.166.0.0/17243.166.0.1 to 243.166.127.254243.166.127.25532,766
78243.166.128.0/17243.166.128.1 to 243.166.255.254243.166.255.25532,766
79243.167.0.0/17243.167.0.1 to 243.167.127.254243.167.127.25532,766
80243.167.128.0/17243.167.128.1 to 243.167.255.254243.167.255.25532,766
81243.168.0.0/17243.168.0.1 to 243.168.127.254243.168.127.25532,766
82243.168.128.0/17243.168.128.1 to 243.168.255.254243.168.255.25532,766
83243.169.0.0/17243.169.0.1 to 243.169.127.254243.169.127.25532,766
84243.169.128.0/17243.169.128.1 to 243.169.255.254243.169.255.25532,766
85243.170.0.0/17243.170.0.1 to 243.170.127.254243.170.127.25532,766
86243.170.128.0/17243.170.128.1 to 243.170.255.254243.170.255.25532,766
87243.171.0.0/17243.171.0.1 to 243.171.127.254243.171.127.25532,766
88243.171.128.0/17243.171.128.1 to 243.171.255.254243.171.255.25532,766
89243.172.0.0/17243.172.0.1 to 243.172.127.254243.172.127.25532,766
90243.172.128.0/17243.172.128.1 to 243.172.255.254243.172.255.25532,766
91243.173.0.0/17243.173.0.1 to 243.173.127.254243.173.127.25532,766
92243.173.128.0/17243.173.128.1 to 243.173.255.254243.173.255.25532,766
93243.174.0.0/17243.174.0.1 to 243.174.127.254243.174.127.25532,766
94243.174.128.0/17243.174.128.1 to 243.174.255.254243.174.255.25532,766
95243.175.0.0/17243.175.0.1 to 243.175.127.254243.175.127.25532,766
96243.175.128.0/17243.175.128.1 to 243.175.255.254243.175.255.25532,766
97243.176.0.0/17243.176.0.1 to 243.176.127.254243.176.127.25532,766
98243.176.128.0/17243.176.128.1 to 243.176.255.254243.176.255.25532,766
99243.177.0.0/17243.177.0.1 to 243.177.127.254243.177.127.25532,766
100243.177.128.0/17243.177.128.1 to 243.177.255.254243.177.255.25532,766
101243.178.0.0/17243.178.0.1 to 243.178.127.254243.178.127.25532,766
102243.178.128.0/17243.178.128.1 to 243.178.255.254243.178.255.25532,766
103243.179.0.0/17243.179.0.1 to 243.179.127.254243.179.127.25532,766
104243.179.128.0/17243.179.128.1 to 243.179.255.254243.179.255.25532,766
105243.180.0.0/17243.180.0.1 to 243.180.127.254243.180.127.25532,766
106243.180.128.0/17243.180.128.1 to 243.180.255.254243.180.255.25532,766
107243.181.0.0/17243.181.0.1 to 243.181.127.254243.181.127.25532,766
108243.181.128.0/17243.181.128.1 to 243.181.255.254243.181.255.25532,766
109243.182.0.0/17243.182.0.1 to 243.182.127.254243.182.127.25532,766
110243.182.128.0/17243.182.128.1 to 243.182.255.254243.182.255.25532,766
111243.183.0.0/17243.183.0.1 to 243.183.127.254243.183.127.25532,766
112243.183.128.0/17243.183.128.1 to 243.183.255.254243.183.255.25532,766
113243.184.0.0/17243.184.0.1 to 243.184.127.254243.184.127.25532,766
114243.184.128.0/17243.184.128.1 to 243.184.255.254243.184.255.25532,766
115243.185.0.0/17243.185.0.1 to 243.185.127.254243.185.127.25532,766
116243.185.128.0/17243.185.128.1 to 243.185.255.254243.185.255.25532,766
117243.186.0.0/17243.186.0.1 to 243.186.127.254243.186.127.25532,766
118243.186.128.0/17243.186.128.1 to 243.186.255.254243.186.255.25532,766
119243.187.0.0/17243.187.0.1 to 243.187.127.254243.187.127.25532,766
120243.187.128.0/17243.187.128.1 to 243.187.255.254243.187.255.25532,766
121243.188.0.0/17243.188.0.1 to 243.188.127.254243.188.127.25532,766
122243.188.128.0/17243.188.128.1 to 243.188.255.254243.188.255.25532,766
123243.189.0.0/17243.189.0.1 to 243.189.127.254243.189.127.25532,766
124243.189.128.0/17243.189.128.1 to 243.189.255.254243.189.255.25532,766
125243.190.0.0/17243.190.0.1 to 243.190.127.254243.190.127.25532,766
126243.190.128.0/17243.190.128.1 to 243.190.255.254243.190.255.25532,766
127243.191.0.0/17243.191.0.1 to 243.191.127.254243.191.127.25532,766
128243.191.128.0/17243.191.128.1 to 243.191.255.254243.191.255.25532,766
129243.192.0.0/17243.192.0.1 to 243.192.127.254243.192.127.25532,766
130243.192.128.0/17243.192.128.1 to 243.192.255.254243.192.255.25532,766
131243.193.0.0/17243.193.0.1 to 243.193.127.254243.193.127.25532,766
132243.193.128.0/17243.193.128.1 to 243.193.255.254243.193.255.25532,766
133243.194.0.0/17243.194.0.1 to 243.194.127.254243.194.127.25532,766
134243.194.128.0/17243.194.128.1 to 243.194.255.254243.194.255.25532,766
135243.195.0.0/17243.195.0.1 to 243.195.127.254243.195.127.25532,766
136243.195.128.0/17243.195.128.1 to 243.195.255.254243.195.255.25532,766
137243.196.0.0/17243.196.0.1 to 243.196.127.254243.196.127.25532,766
138243.196.128.0/17243.196.128.1 to 243.196.255.254243.196.255.25532,766
139243.197.0.0/17243.197.0.1 to 243.197.127.254243.197.127.25532,766
140243.197.128.0/17243.197.128.1 to 243.197.255.254243.197.255.25532,766
141243.198.0.0/17243.198.0.1 to 243.198.127.254243.198.127.25532,766
142243.198.128.0/17243.198.128.1 to 243.198.255.254243.198.255.25532,766
143243.199.0.0/17243.199.0.1 to 243.199.127.254243.199.127.25532,766
144243.199.128.0/17243.199.128.1 to 243.199.255.254243.199.255.25532,766
145243.200.0.0/17243.200.0.1 to 243.200.127.254243.200.127.25532,766
146243.200.128.0/17243.200.128.1 to 243.200.255.254243.200.255.25532,766
147243.201.0.0/17243.201.0.1 to 243.201.127.254243.201.127.25532,766
148243.201.128.0/17243.201.128.1 to 243.201.255.254243.201.255.25532,766
149243.202.0.0/17243.202.0.1 to 243.202.127.254243.202.127.25532,766
150243.202.128.0/17243.202.128.1 to 243.202.255.254243.202.255.25532,766
151243.203.0.0/17243.203.0.1 to 243.203.127.254243.203.127.25532,766
152243.203.128.0/17243.203.128.1 to 243.203.255.254243.203.255.25532,766
153243.204.0.0/17243.204.0.1 to 243.204.127.254243.204.127.25532,766
154243.204.128.0/17243.204.128.1 to 243.204.255.254243.204.255.25532,766
155243.205.0.0/17243.205.0.1 to 243.205.127.254243.205.127.25532,766
156243.205.128.0/17243.205.128.1 to 243.205.255.254243.205.255.25532,766
157243.206.0.0/17243.206.0.1 to 243.206.127.254243.206.127.25532,766
158243.206.128.0/17243.206.128.1 to 243.206.255.254243.206.255.25532,766
159243.207.0.0/17243.207.0.1 to 243.207.127.254243.207.127.25532,766
160243.207.128.0/17243.207.128.1 to 243.207.255.254243.207.255.25532,766
161243.208.0.0/17243.208.0.1 to 243.208.127.254243.208.127.25532,766
162243.208.128.0/17243.208.128.1 to 243.208.255.254243.208.255.25532,766
163243.209.0.0/17243.209.0.1 to 243.209.127.254243.209.127.25532,766
164243.209.128.0/17243.209.128.1 to 243.209.255.254243.209.255.25532,766
165243.210.0.0/17243.210.0.1 to 243.210.127.254243.210.127.25532,766
166243.210.128.0/17243.210.128.1 to 243.210.255.254243.210.255.25532,766
167243.211.0.0/17243.211.0.1 to 243.211.127.254243.211.127.25532,766
168243.211.128.0/17243.211.128.1 to 243.211.255.254243.211.255.25532,766
169243.212.0.0/17243.212.0.1 to 243.212.127.254243.212.127.25532,766
170243.212.128.0/17243.212.128.1 to 243.212.255.254243.212.255.25532,766
171243.213.0.0/17243.213.0.1 to 243.213.127.254243.213.127.25532,766
172243.213.128.0/17243.213.128.1 to 243.213.255.254243.213.255.25532,766
173243.214.0.0/17243.214.0.1 to 243.214.127.254243.214.127.25532,766
174243.214.128.0/17243.214.128.1 to 243.214.255.254243.214.255.25532,766
175243.215.0.0/17243.215.0.1 to 243.215.127.254243.215.127.25532,766
176243.215.128.0/17243.215.128.1 to 243.215.255.254243.215.255.25532,766
177243.216.0.0/17243.216.0.1 to 243.216.127.254243.216.127.25532,766
178243.216.128.0/17243.216.128.1 to 243.216.255.254243.216.255.25532,766
179243.217.0.0/17243.217.0.1 to 243.217.127.254243.217.127.25532,766
180243.217.128.0/17243.217.128.1 to 243.217.255.254243.217.255.25532,766
181243.218.0.0/17243.218.0.1 to 243.218.127.254243.218.127.25532,766
182243.218.128.0/17243.218.128.1 to 243.218.255.254243.218.255.25532,766
183243.219.0.0/17243.219.0.1 to 243.219.127.254243.219.127.25532,766
184243.219.128.0/17243.219.128.1 to 243.219.255.254243.219.255.25532,766
185243.220.0.0/17243.220.0.1 to 243.220.127.254243.220.127.25532,766
186243.220.128.0/17243.220.128.1 to 243.220.255.254243.220.255.25532,766
187243.221.0.0/17243.221.0.1 to 243.221.127.254243.221.127.25532,766
188243.221.128.0/17243.221.128.1 to 243.221.255.254243.221.255.25532,766
189243.222.0.0/17243.222.0.1 to 243.222.127.254243.222.127.25532,766
190243.222.128.0/17243.222.128.1 to 243.222.255.254243.222.255.25532,766
191243.223.0.0/17243.223.0.1 to 243.223.127.254243.223.127.25532,766
192243.223.128.0/17243.223.128.1 to 243.223.255.254243.223.255.25532,766
193243.224.0.0/17243.224.0.1 to 243.224.127.254243.224.127.25532,766
194243.224.128.0/17243.224.128.1 to 243.224.255.254243.224.255.25532,766
195243.225.0.0/17243.225.0.1 to 243.225.127.254243.225.127.25532,766
196243.225.128.0/17243.225.128.1 to 243.225.255.254243.225.255.25532,766
197243.226.0.0/17243.226.0.1 to 243.226.127.254243.226.127.25532,766
198243.226.128.0/17243.226.128.1 to 243.226.255.254243.226.255.25532,766
199243.227.0.0/17243.227.0.1 to 243.227.127.254243.227.127.25532,766
200243.227.128.0/17243.227.128.1 to 243.227.255.254243.227.255.25532,766
201243.228.0.0/17243.228.0.1 to 243.228.127.254243.228.127.25532,766
202243.228.128.0/17243.228.128.1 to 243.228.255.254243.228.255.25532,766
203243.229.0.0/17243.229.0.1 to 243.229.127.254243.229.127.25532,766
204243.229.128.0/17243.229.128.1 to 243.229.255.254243.229.255.25532,766
205243.230.0.0/17243.230.0.1 to 243.230.127.254243.230.127.25532,766
206243.230.128.0/17243.230.128.1 to 243.230.255.254243.230.255.25532,766
207243.231.0.0/17243.231.0.1 to 243.231.127.254243.231.127.25532,766
208243.231.128.0/17243.231.128.1 to 243.231.255.254243.231.255.25532,766
209243.232.0.0/17243.232.0.1 to 243.232.127.254243.232.127.25532,766
210243.232.128.0/17243.232.128.1 to 243.232.255.254243.232.255.25532,766
211243.233.0.0/17243.233.0.1 to 243.233.127.254243.233.127.25532,766
212243.233.128.0/17243.233.128.1 to 243.233.255.254243.233.255.25532,766
213243.234.0.0/17243.234.0.1 to 243.234.127.254243.234.127.25532,766
214243.234.128.0/17243.234.128.1 to 243.234.255.254243.234.255.25532,766
215243.235.0.0/17243.235.0.1 to 243.235.127.254243.235.127.25532,766
216243.235.128.0/17243.235.128.1 to 243.235.255.254243.235.255.25532,766
217243.236.0.0/17243.236.0.1 to 243.236.127.254243.236.127.25532,766
218243.236.128.0/17243.236.128.1 to 243.236.255.254243.236.255.25532,766
219243.237.0.0/17243.237.0.1 to 243.237.127.254243.237.127.25532,766
220243.237.128.0/17243.237.128.1 to 243.237.255.254243.237.255.25532,766
221243.238.0.0/17243.238.0.1 to 243.238.127.254243.238.127.25532,766
222243.238.128.0/17243.238.128.1 to 243.238.255.254243.238.255.25532,766
223243.239.0.0/17243.239.0.1 to 243.239.127.254243.239.127.25532,766
224243.239.128.0/17243.239.128.1 to 243.239.255.254243.239.255.25532,766
225243.240.0.0/17243.240.0.1 to 243.240.127.254243.240.127.25532,766
226243.240.128.0/17243.240.128.1 to 243.240.255.254243.240.255.25532,766
227243.241.0.0/17243.241.0.1 to 243.241.127.254243.241.127.25532,766
228243.241.128.0/17243.241.128.1 to 243.241.255.254243.241.255.25532,766
229243.242.0.0/17243.242.0.1 to 243.242.127.254243.242.127.25532,766
230243.242.128.0/17243.242.128.1 to 243.242.255.254243.242.255.25532,766
231243.243.0.0/17243.243.0.1 to 243.243.127.254243.243.127.25532,766
232243.243.128.0/17243.243.128.1 to 243.243.255.254243.243.255.25532,766
233243.244.0.0/17243.244.0.1 to 243.244.127.254243.244.127.25532,766
234243.244.128.0/17243.244.128.1 to 243.244.255.254243.244.255.25532,766
235243.245.0.0/17243.245.0.1 to 243.245.127.254243.245.127.25532,766
236243.245.128.0/17243.245.128.1 to 243.245.255.254243.245.255.25532,766
237243.246.0.0/17243.246.0.1 to 243.246.127.254243.246.127.25532,766
238243.246.128.0/17243.246.128.1 to 243.246.255.254243.246.255.25532,766
239243.247.0.0/17243.247.0.1 to 243.247.127.254243.247.127.25532,766
240243.247.128.0/17243.247.128.1 to 243.247.255.254243.247.255.25532,766
241243.248.0.0/17243.248.0.1 to 243.248.127.254243.248.127.25532,766
242243.248.128.0/17243.248.128.1 to 243.248.255.254243.248.255.25532,766
243243.249.0.0/17243.249.0.1 to 243.249.127.254243.249.127.25532,766
244243.249.128.0/17243.249.128.1 to 243.249.255.254243.249.255.25532,766
245243.250.0.0/17243.250.0.1 to 243.250.127.254243.250.127.25532,766
246243.250.128.0/17243.250.128.1 to 243.250.255.254243.250.255.25532,766
247243.251.0.0/17243.251.0.1 to 243.251.127.254243.251.127.25532,766
248243.251.128.0/17243.251.128.1 to 243.251.255.254243.251.255.25532,766
249243.252.0.0/17243.252.0.1 to 243.252.127.254243.252.127.25532,766
250243.252.128.0/17243.252.128.1 to 243.252.255.254243.252.255.25532,766
251243.253.0.0/17243.253.0.1 to 243.253.127.254243.253.127.25532,766
252243.253.128.0/17243.253.128.1 to 243.253.255.254243.253.255.25532,766
253243.254.0.0/17243.254.0.1 to 243.254.127.254243.254.127.25532,766
254243.254.128.0/17243.254.128.1 to 243.254.255.254243.254.255.25532,766
255243.255.0.0/17243.255.0.1 to 243.255.127.254243.255.127.25532,766
256243.255.128.0/17243.255.128.1 to 243.255.255.254243.255.255.25532,766

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.