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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.

Network192.168.208.0/21
Usable hosts2,046
Subnet mask255.255.248.0
Addresses2,048
Network address
192.168.208.0
Broadcast address
192.168.215.255
First usable
192.168.208.1
Last usable
192.168.215.254
Usable hosts
2,046 (2,048 less the network and broadcast addresses)
Subnet mask
255.255.248.0
Wildcard mask
0.0.7.255 (Cisco ACLs, OSPF)
Prefix length
/21
Type
Private (RFC 1918) 192.168.0.0/16
Office and home networks; not routed on the internet
Old class
C (default /24)
As numbers
Hex C0A8D000 · Integer 3232288768 to 3232290815
Reverse DNS zones
208.168.192.in-addr.arpa
209.168.192.in-addr.arpa
210.168.192.in-addr.arpa
211.168.192.in-addr.arpa
212.168.192.in-addr.arpa
213.168.192.in-addr.arpa
214.168.192.in-addr.arpa
215.168.192.in-addr.arpa
/21 is not on a 8-bit boundary, so it takes 8 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11000000.10101000.11010000.00000000192.168.208.0
Subnet mask11111111.11111111.11111000.00000000255.255.248.0
Network11000000.10101000.11010000.00000000192.168.208.0
Broadcast11000000.10101000.11010111.11111111192.168.215.255
Split into smaller subnets/30
/22 (2)/23 (4)/24 (8)/25 (16)/26 (32)/27 (64)/28 (128)/29 (256)/30 (512)/31 (1,024)/32 (2,048)

192.168.208.0/21 makes 512 subnets of /30; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1192.168.208.0/30192.168.208.1 to 192.168.208.2192.168.208.32
2192.168.208.4/30192.168.208.5 to 192.168.208.6192.168.208.72
3192.168.208.8/30192.168.208.9 to 192.168.208.10192.168.208.112
4192.168.208.12/30192.168.208.13 to 192.168.208.14192.168.208.152
5192.168.208.16/30192.168.208.17 to 192.168.208.18192.168.208.192
6192.168.208.20/30192.168.208.21 to 192.168.208.22192.168.208.232
7192.168.208.24/30192.168.208.25 to 192.168.208.26192.168.208.272
8192.168.208.28/30192.168.208.29 to 192.168.208.30192.168.208.312
9192.168.208.32/30192.168.208.33 to 192.168.208.34192.168.208.352
10192.168.208.36/30192.168.208.37 to 192.168.208.38192.168.208.392
11192.168.208.40/30192.168.208.41 to 192.168.208.42192.168.208.432
12192.168.208.44/30192.168.208.45 to 192.168.208.46192.168.208.472
13192.168.208.48/30192.168.208.49 to 192.168.208.50192.168.208.512
14192.168.208.52/30192.168.208.53 to 192.168.208.54192.168.208.552
15192.168.208.56/30192.168.208.57 to 192.168.208.58192.168.208.592
16192.168.208.60/30192.168.208.61 to 192.168.208.62192.168.208.632
17192.168.208.64/30192.168.208.65 to 192.168.208.66192.168.208.672
18192.168.208.68/30192.168.208.69 to 192.168.208.70192.168.208.712
19192.168.208.72/30192.168.208.73 to 192.168.208.74192.168.208.752
20192.168.208.76/30192.168.208.77 to 192.168.208.78192.168.208.792
21192.168.208.80/30192.168.208.81 to 192.168.208.82192.168.208.832
22192.168.208.84/30192.168.208.85 to 192.168.208.86192.168.208.872
23192.168.208.88/30192.168.208.89 to 192.168.208.90192.168.208.912
24192.168.208.92/30192.168.208.93 to 192.168.208.94192.168.208.952
25192.168.208.96/30192.168.208.97 to 192.168.208.98192.168.208.992
26192.168.208.100/30192.168.208.101 to 192.168.208.102192.168.208.1032
27192.168.208.104/30192.168.208.105 to 192.168.208.106192.168.208.1072
28192.168.208.108/30192.168.208.109 to 192.168.208.110192.168.208.1112
29192.168.208.112/30192.168.208.113 to 192.168.208.114192.168.208.1152
30192.168.208.116/30192.168.208.117 to 192.168.208.118192.168.208.1192
31192.168.208.120/30192.168.208.121 to 192.168.208.122192.168.208.1232
32192.168.208.124/30192.168.208.125 to 192.168.208.126192.168.208.1272
33192.168.208.128/30192.168.208.129 to 192.168.208.130192.168.208.1312
34192.168.208.132/30192.168.208.133 to 192.168.208.134192.168.208.1352
35192.168.208.136/30192.168.208.137 to 192.168.208.138192.168.208.1392
36192.168.208.140/30192.168.208.141 to 192.168.208.142192.168.208.1432
37192.168.208.144/30192.168.208.145 to 192.168.208.146192.168.208.1472
38192.168.208.148/30192.168.208.149 to 192.168.208.150192.168.208.1512
39192.168.208.152/30192.168.208.153 to 192.168.208.154192.168.208.1552
40192.168.208.156/30192.168.208.157 to 192.168.208.158192.168.208.1592
41192.168.208.160/30192.168.208.161 to 192.168.208.162192.168.208.1632
42192.168.208.164/30192.168.208.165 to 192.168.208.166192.168.208.1672
43192.168.208.168/30192.168.208.169 to 192.168.208.170192.168.208.1712
44192.168.208.172/30192.168.208.173 to 192.168.208.174192.168.208.1752
45192.168.208.176/30192.168.208.177 to 192.168.208.178192.168.208.1792
46192.168.208.180/30192.168.208.181 to 192.168.208.182192.168.208.1832
47192.168.208.184/30192.168.208.185 to 192.168.208.186192.168.208.1872
48192.168.208.188/30192.168.208.189 to 192.168.208.190192.168.208.1912
49192.168.208.192/30192.168.208.193 to 192.168.208.194192.168.208.1952
50192.168.208.196/30192.168.208.197 to 192.168.208.198192.168.208.1992
51192.168.208.200/30192.168.208.201 to 192.168.208.202192.168.208.2032
52192.168.208.204/30192.168.208.205 to 192.168.208.206192.168.208.2072
53192.168.208.208/30192.168.208.209 to 192.168.208.210192.168.208.2112
54192.168.208.212/30192.168.208.213 to 192.168.208.214192.168.208.2152
55192.168.208.216/30192.168.208.217 to 192.168.208.218192.168.208.2192
56192.168.208.220/30192.168.208.221 to 192.168.208.222192.168.208.2232
57192.168.208.224/30192.168.208.225 to 192.168.208.226192.168.208.2272
58192.168.208.228/30192.168.208.229 to 192.168.208.230192.168.208.2312
59192.168.208.232/30192.168.208.233 to 192.168.208.234192.168.208.2352
60192.168.208.236/30192.168.208.237 to 192.168.208.238192.168.208.2392
61192.168.208.240/30192.168.208.241 to 192.168.208.242192.168.208.2432
62192.168.208.244/30192.168.208.245 to 192.168.208.246192.168.208.2472
63192.168.208.248/30192.168.208.249 to 192.168.208.250192.168.208.2512
64192.168.208.252/30192.168.208.253 to 192.168.208.254192.168.208.2552
65192.168.209.0/30192.168.209.1 to 192.168.209.2192.168.209.32
66192.168.209.4/30192.168.209.5 to 192.168.209.6192.168.209.72
67192.168.209.8/30192.168.209.9 to 192.168.209.10192.168.209.112
68192.168.209.12/30192.168.209.13 to 192.168.209.14192.168.209.152
69192.168.209.16/30192.168.209.17 to 192.168.209.18192.168.209.192
70192.168.209.20/30192.168.209.21 to 192.168.209.22192.168.209.232
71192.168.209.24/30192.168.209.25 to 192.168.209.26192.168.209.272
72192.168.209.28/30192.168.209.29 to 192.168.209.30192.168.209.312
73192.168.209.32/30192.168.209.33 to 192.168.209.34192.168.209.352
74192.168.209.36/30192.168.209.37 to 192.168.209.38192.168.209.392
75192.168.209.40/30192.168.209.41 to 192.168.209.42192.168.209.432
76192.168.209.44/30192.168.209.45 to 192.168.209.46192.168.209.472
77192.168.209.48/30192.168.209.49 to 192.168.209.50192.168.209.512
78192.168.209.52/30192.168.209.53 to 192.168.209.54192.168.209.552
79192.168.209.56/30192.168.209.57 to 192.168.209.58192.168.209.592
80192.168.209.60/30192.168.209.61 to 192.168.209.62192.168.209.632
81192.168.209.64/30192.168.209.65 to 192.168.209.66192.168.209.672
82192.168.209.68/30192.168.209.69 to 192.168.209.70192.168.209.712
83192.168.209.72/30192.168.209.73 to 192.168.209.74192.168.209.752
84192.168.209.76/30192.168.209.77 to 192.168.209.78192.168.209.792
85192.168.209.80/30192.168.209.81 to 192.168.209.82192.168.209.832
86192.168.209.84/30192.168.209.85 to 192.168.209.86192.168.209.872
87192.168.209.88/30192.168.209.89 to 192.168.209.90192.168.209.912
88192.168.209.92/30192.168.209.93 to 192.168.209.94192.168.209.952
89192.168.209.96/30192.168.209.97 to 192.168.209.98192.168.209.992
90192.168.209.100/30192.168.209.101 to 192.168.209.102192.168.209.1032
91192.168.209.104/30192.168.209.105 to 192.168.209.106192.168.209.1072
92192.168.209.108/30192.168.209.109 to 192.168.209.110192.168.209.1112
93192.168.209.112/30192.168.209.113 to 192.168.209.114192.168.209.1152
94192.168.209.116/30192.168.209.117 to 192.168.209.118192.168.209.1192
95192.168.209.120/30192.168.209.121 to 192.168.209.122192.168.209.1232
96192.168.209.124/30192.168.209.125 to 192.168.209.126192.168.209.1272
97192.168.209.128/30192.168.209.129 to 192.168.209.130192.168.209.1312
98192.168.209.132/30192.168.209.133 to 192.168.209.134192.168.209.1352
99192.168.209.136/30192.168.209.137 to 192.168.209.138192.168.209.1392
100192.168.209.140/30192.168.209.141 to 192.168.209.142192.168.209.1432
101192.168.209.144/30192.168.209.145 to 192.168.209.146192.168.209.1472
102192.168.209.148/30192.168.209.149 to 192.168.209.150192.168.209.1512
103192.168.209.152/30192.168.209.153 to 192.168.209.154192.168.209.1552
104192.168.209.156/30192.168.209.157 to 192.168.209.158192.168.209.1592
105192.168.209.160/30192.168.209.161 to 192.168.209.162192.168.209.1632
106192.168.209.164/30192.168.209.165 to 192.168.209.166192.168.209.1672
107192.168.209.168/30192.168.209.169 to 192.168.209.170192.168.209.1712
108192.168.209.172/30192.168.209.173 to 192.168.209.174192.168.209.1752
109192.168.209.176/30192.168.209.177 to 192.168.209.178192.168.209.1792
110192.168.209.180/30192.168.209.181 to 192.168.209.182192.168.209.1832
111192.168.209.184/30192.168.209.185 to 192.168.209.186192.168.209.1872
112192.168.209.188/30192.168.209.189 to 192.168.209.190192.168.209.1912
113192.168.209.192/30192.168.209.193 to 192.168.209.194192.168.209.1952
114192.168.209.196/30192.168.209.197 to 192.168.209.198192.168.209.1992
115192.168.209.200/30192.168.209.201 to 192.168.209.202192.168.209.2032
116192.168.209.204/30192.168.209.205 to 192.168.209.206192.168.209.2072
117192.168.209.208/30192.168.209.209 to 192.168.209.210192.168.209.2112
118192.168.209.212/30192.168.209.213 to 192.168.209.214192.168.209.2152
119192.168.209.216/30192.168.209.217 to 192.168.209.218192.168.209.2192
120192.168.209.220/30192.168.209.221 to 192.168.209.222192.168.209.2232
121192.168.209.224/30192.168.209.225 to 192.168.209.226192.168.209.2272
122192.168.209.228/30192.168.209.229 to 192.168.209.230192.168.209.2312
123192.168.209.232/30192.168.209.233 to 192.168.209.234192.168.209.2352
124192.168.209.236/30192.168.209.237 to 192.168.209.238192.168.209.2392
125192.168.209.240/30192.168.209.241 to 192.168.209.242192.168.209.2432
126192.168.209.244/30192.168.209.245 to 192.168.209.246192.168.209.2472
127192.168.209.248/30192.168.209.249 to 192.168.209.250192.168.209.2512
128192.168.209.252/30192.168.209.253 to 192.168.209.254192.168.209.2552
129192.168.210.0/30192.168.210.1 to 192.168.210.2192.168.210.32
130192.168.210.4/30192.168.210.5 to 192.168.210.6192.168.210.72
131192.168.210.8/30192.168.210.9 to 192.168.210.10192.168.210.112
132192.168.210.12/30192.168.210.13 to 192.168.210.14192.168.210.152
133192.168.210.16/30192.168.210.17 to 192.168.210.18192.168.210.192
134192.168.210.20/30192.168.210.21 to 192.168.210.22192.168.210.232
135192.168.210.24/30192.168.210.25 to 192.168.210.26192.168.210.272
136192.168.210.28/30192.168.210.29 to 192.168.210.30192.168.210.312
137192.168.210.32/30192.168.210.33 to 192.168.210.34192.168.210.352
138192.168.210.36/30192.168.210.37 to 192.168.210.38192.168.210.392
139192.168.210.40/30192.168.210.41 to 192.168.210.42192.168.210.432
140192.168.210.44/30192.168.210.45 to 192.168.210.46192.168.210.472
141192.168.210.48/30192.168.210.49 to 192.168.210.50192.168.210.512
142192.168.210.52/30192.168.210.53 to 192.168.210.54192.168.210.552
143192.168.210.56/30192.168.210.57 to 192.168.210.58192.168.210.592
144192.168.210.60/30192.168.210.61 to 192.168.210.62192.168.210.632
145192.168.210.64/30192.168.210.65 to 192.168.210.66192.168.210.672
146192.168.210.68/30192.168.210.69 to 192.168.210.70192.168.210.712
147192.168.210.72/30192.168.210.73 to 192.168.210.74192.168.210.752
148192.168.210.76/30192.168.210.77 to 192.168.210.78192.168.210.792
149192.168.210.80/30192.168.210.81 to 192.168.210.82192.168.210.832
150192.168.210.84/30192.168.210.85 to 192.168.210.86192.168.210.872
151192.168.210.88/30192.168.210.89 to 192.168.210.90192.168.210.912
152192.168.210.92/30192.168.210.93 to 192.168.210.94192.168.210.952
153192.168.210.96/30192.168.210.97 to 192.168.210.98192.168.210.992
154192.168.210.100/30192.168.210.101 to 192.168.210.102192.168.210.1032
155192.168.210.104/30192.168.210.105 to 192.168.210.106192.168.210.1072
156192.168.210.108/30192.168.210.109 to 192.168.210.110192.168.210.1112
157192.168.210.112/30192.168.210.113 to 192.168.210.114192.168.210.1152
158192.168.210.116/30192.168.210.117 to 192.168.210.118192.168.210.1192
159192.168.210.120/30192.168.210.121 to 192.168.210.122192.168.210.1232
160192.168.210.124/30192.168.210.125 to 192.168.210.126192.168.210.1272
161192.168.210.128/30192.168.210.129 to 192.168.210.130192.168.210.1312
162192.168.210.132/30192.168.210.133 to 192.168.210.134192.168.210.1352
163192.168.210.136/30192.168.210.137 to 192.168.210.138192.168.210.1392
164192.168.210.140/30192.168.210.141 to 192.168.210.142192.168.210.1432
165192.168.210.144/30192.168.210.145 to 192.168.210.146192.168.210.1472
166192.168.210.148/30192.168.210.149 to 192.168.210.150192.168.210.1512
167192.168.210.152/30192.168.210.153 to 192.168.210.154192.168.210.1552
168192.168.210.156/30192.168.210.157 to 192.168.210.158192.168.210.1592
169192.168.210.160/30192.168.210.161 to 192.168.210.162192.168.210.1632
170192.168.210.164/30192.168.210.165 to 192.168.210.166192.168.210.1672
171192.168.210.168/30192.168.210.169 to 192.168.210.170192.168.210.1712
172192.168.210.172/30192.168.210.173 to 192.168.210.174192.168.210.1752
173192.168.210.176/30192.168.210.177 to 192.168.210.178192.168.210.1792
174192.168.210.180/30192.168.210.181 to 192.168.210.182192.168.210.1832
175192.168.210.184/30192.168.210.185 to 192.168.210.186192.168.210.1872
176192.168.210.188/30192.168.210.189 to 192.168.210.190192.168.210.1912
177192.168.210.192/30192.168.210.193 to 192.168.210.194192.168.210.1952
178192.168.210.196/30192.168.210.197 to 192.168.210.198192.168.210.1992
179192.168.210.200/30192.168.210.201 to 192.168.210.202192.168.210.2032
180192.168.210.204/30192.168.210.205 to 192.168.210.206192.168.210.2072
181192.168.210.208/30192.168.210.209 to 192.168.210.210192.168.210.2112
182192.168.210.212/30192.168.210.213 to 192.168.210.214192.168.210.2152
183192.168.210.216/30192.168.210.217 to 192.168.210.218192.168.210.2192
184192.168.210.220/30192.168.210.221 to 192.168.210.222192.168.210.2232
185192.168.210.224/30192.168.210.225 to 192.168.210.226192.168.210.2272
186192.168.210.228/30192.168.210.229 to 192.168.210.230192.168.210.2312
187192.168.210.232/30192.168.210.233 to 192.168.210.234192.168.210.2352
188192.168.210.236/30192.168.210.237 to 192.168.210.238192.168.210.2392
189192.168.210.240/30192.168.210.241 to 192.168.210.242192.168.210.2432
190192.168.210.244/30192.168.210.245 to 192.168.210.246192.168.210.2472
191192.168.210.248/30192.168.210.249 to 192.168.210.250192.168.210.2512
192192.168.210.252/30192.168.210.253 to 192.168.210.254192.168.210.2552
193192.168.211.0/30192.168.211.1 to 192.168.211.2192.168.211.32
194192.168.211.4/30192.168.211.5 to 192.168.211.6192.168.211.72
195192.168.211.8/30192.168.211.9 to 192.168.211.10192.168.211.112
196192.168.211.12/30192.168.211.13 to 192.168.211.14192.168.211.152
197192.168.211.16/30192.168.211.17 to 192.168.211.18192.168.211.192
198192.168.211.20/30192.168.211.21 to 192.168.211.22192.168.211.232
199192.168.211.24/30192.168.211.25 to 192.168.211.26192.168.211.272
200192.168.211.28/30192.168.211.29 to 192.168.211.30192.168.211.312
201192.168.211.32/30192.168.211.33 to 192.168.211.34192.168.211.352
202192.168.211.36/30192.168.211.37 to 192.168.211.38192.168.211.392
203192.168.211.40/30192.168.211.41 to 192.168.211.42192.168.211.432
204192.168.211.44/30192.168.211.45 to 192.168.211.46192.168.211.472
205192.168.211.48/30192.168.211.49 to 192.168.211.50192.168.211.512
206192.168.211.52/30192.168.211.53 to 192.168.211.54192.168.211.552
207192.168.211.56/30192.168.211.57 to 192.168.211.58192.168.211.592
208192.168.211.60/30192.168.211.61 to 192.168.211.62192.168.211.632
209192.168.211.64/30192.168.211.65 to 192.168.211.66192.168.211.672
210192.168.211.68/30192.168.211.69 to 192.168.211.70192.168.211.712
211192.168.211.72/30192.168.211.73 to 192.168.211.74192.168.211.752
212192.168.211.76/30192.168.211.77 to 192.168.211.78192.168.211.792
213192.168.211.80/30192.168.211.81 to 192.168.211.82192.168.211.832
214192.168.211.84/30192.168.211.85 to 192.168.211.86192.168.211.872
215192.168.211.88/30192.168.211.89 to 192.168.211.90192.168.211.912
216192.168.211.92/30192.168.211.93 to 192.168.211.94192.168.211.952
217192.168.211.96/30192.168.211.97 to 192.168.211.98192.168.211.992
218192.168.211.100/30192.168.211.101 to 192.168.211.102192.168.211.1032
219192.168.211.104/30192.168.211.105 to 192.168.211.106192.168.211.1072
220192.168.211.108/30192.168.211.109 to 192.168.211.110192.168.211.1112
221192.168.211.112/30192.168.211.113 to 192.168.211.114192.168.211.1152
222192.168.211.116/30192.168.211.117 to 192.168.211.118192.168.211.1192
223192.168.211.120/30192.168.211.121 to 192.168.211.122192.168.211.1232
224192.168.211.124/30192.168.211.125 to 192.168.211.126192.168.211.1272
225192.168.211.128/30192.168.211.129 to 192.168.211.130192.168.211.1312
226192.168.211.132/30192.168.211.133 to 192.168.211.134192.168.211.1352
227192.168.211.136/30192.168.211.137 to 192.168.211.138192.168.211.1392
228192.168.211.140/30192.168.211.141 to 192.168.211.142192.168.211.1432
229192.168.211.144/30192.168.211.145 to 192.168.211.146192.168.211.1472
230192.168.211.148/30192.168.211.149 to 192.168.211.150192.168.211.1512
231192.168.211.152/30192.168.211.153 to 192.168.211.154192.168.211.1552
232192.168.211.156/30192.168.211.157 to 192.168.211.158192.168.211.1592
233192.168.211.160/30192.168.211.161 to 192.168.211.162192.168.211.1632
234192.168.211.164/30192.168.211.165 to 192.168.211.166192.168.211.1672
235192.168.211.168/30192.168.211.169 to 192.168.211.170192.168.211.1712
236192.168.211.172/30192.168.211.173 to 192.168.211.174192.168.211.1752
237192.168.211.176/30192.168.211.177 to 192.168.211.178192.168.211.1792
238192.168.211.180/30192.168.211.181 to 192.168.211.182192.168.211.1832
239192.168.211.184/30192.168.211.185 to 192.168.211.186192.168.211.1872
240192.168.211.188/30192.168.211.189 to 192.168.211.190192.168.211.1912
241192.168.211.192/30192.168.211.193 to 192.168.211.194192.168.211.1952
242192.168.211.196/30192.168.211.197 to 192.168.211.198192.168.211.1992
243192.168.211.200/30192.168.211.201 to 192.168.211.202192.168.211.2032
244192.168.211.204/30192.168.211.205 to 192.168.211.206192.168.211.2072
245192.168.211.208/30192.168.211.209 to 192.168.211.210192.168.211.2112
246192.168.211.212/30192.168.211.213 to 192.168.211.214192.168.211.2152
247192.168.211.216/30192.168.211.217 to 192.168.211.218192.168.211.2192
248192.168.211.220/30192.168.211.221 to 192.168.211.222192.168.211.2232
249192.168.211.224/30192.168.211.225 to 192.168.211.226192.168.211.2272
250192.168.211.228/30192.168.211.229 to 192.168.211.230192.168.211.2312
251192.168.211.232/30192.168.211.233 to 192.168.211.234192.168.211.2352
252192.168.211.236/30192.168.211.237 to 192.168.211.238192.168.211.2392
253192.168.211.240/30192.168.211.241 to 192.168.211.242192.168.211.2432
254192.168.211.244/30192.168.211.245 to 192.168.211.246192.168.211.2472
255192.168.211.248/30192.168.211.249 to 192.168.211.250192.168.211.2512
256192.168.211.252/30192.168.211.253 to 192.168.211.254192.168.211.2552

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.