Speed and call quality testMy IP addressIP subnet calculatorDNS reportWhoIs lookupRemote support

Internet and network

Speed and call quality testTest delay, jitter and speed, with a focus on phone calls.My IP addressYour public IPv4 and IPv6 addresses, provider and address range.WhoIs lookupWho owns a domain or IP address, when it expires, and its DNS.DNS reportEvery DNS record for a domain, with email setup checked.IP subnet calculatorWork out a network's range, mask and hosts, and split it into subnets.

Computers and devices

Update checkIs this computer, phone and browser up to date? With links to update.Camera and mic testCheck your webcam and microphone before a call.Test print pagePrint an A4 page to check a printer: edges, text, line art and colours.

Make and print

Clean textStrip hidden characters, smart quotes and odd spaces from pasted text.QR code makerMake a QR code for a link, contact or message. Nothing leaves your browser.Wi-Fi QR posterPrint an A4 poster that lets guests join your Wi-Fi by scanning.

Surftec support

Remote supportLet a Surftec engineer connect to your computer to help you.All workingA full-screen confirmation that everything is up and running.

Surftec

Surftec websiteServices, news and how to contact Surftec
Cloud Tools
Guest
GuestNot signed in

Surftec customers will be recognised automatically when they use these tools from their office network.

Customer sign-in is coming soon.

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.

Network212.2.0.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
212.2.0.0
Broadcast address
212.2.63.255
First usable
212.2.0.1
Last usable
212.2.63.254
Usable hosts
16,382 (16,384 less the network and broadcast addresses)
Subnet mask
255.255.192.0
Wildcard mask
0.0.63.255 (Cisco ACLs, OSPF)
Prefix length
/18
Type
Public public
Old class
C (default /24)
As numbers
Hex D4020000 · Integer 3556900864 to 3556917247
Reverse DNS zones
0.2.212.in-addr.arpa
1.2.212.in-addr.arpa
2.2.212.in-addr.arpa
3.2.212.in-addr.arpa
4.2.212.in-addr.arpa
5.2.212.in-addr.arpa
6.2.212.in-addr.arpa
7.2.212.in-addr.arpa
8.2.212.in-addr.arpa
9.2.212.in-addr.arpa
10.2.212.in-addr.arpa
11.2.212.in-addr.arpa
12.2.212.in-addr.arpa
13.2.212.in-addr.arpa
14.2.212.in-addr.arpa
15.2.212.in-addr.arpa
and 48 more
/18 is not on a 8-bit boundary, so it takes 64 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11010100.00000010.00000000.00000000212.2.0.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network11010100.00000010.00000000.00000000212.2.0.0
Broadcast11010100.00000010.00111111.11111111212.2.63.255
Split into smaller subnets/30
/19 (2)/20 (4)/21 (8)/22 (16)/23 (32)/24 (64)/25 (128)/26 (256)/27 (512)/28 (1,024)/29 (2,048)/30 (4,096)

212.2.0.0/18 makes 4,096 subnets of /30; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1212.2.0.0/30212.2.0.1 to 212.2.0.2212.2.0.32
2212.2.0.4/30212.2.0.5 to 212.2.0.6212.2.0.72
3212.2.0.8/30212.2.0.9 to 212.2.0.10212.2.0.112
4212.2.0.12/30212.2.0.13 to 212.2.0.14212.2.0.152
5212.2.0.16/30212.2.0.17 to 212.2.0.18212.2.0.192
6212.2.0.20/30212.2.0.21 to 212.2.0.22212.2.0.232
7212.2.0.24/30212.2.0.25 to 212.2.0.26212.2.0.272
8212.2.0.28/30212.2.0.29 to 212.2.0.30212.2.0.312
9212.2.0.32/30212.2.0.33 to 212.2.0.34212.2.0.352
10212.2.0.36/30212.2.0.37 to 212.2.0.38212.2.0.392
11212.2.0.40/30212.2.0.41 to 212.2.0.42212.2.0.432
12212.2.0.44/30212.2.0.45 to 212.2.0.46212.2.0.472
13212.2.0.48/30212.2.0.49 to 212.2.0.50212.2.0.512
14212.2.0.52/30212.2.0.53 to 212.2.0.54212.2.0.552
15212.2.0.56/30212.2.0.57 to 212.2.0.58212.2.0.592
16212.2.0.60/30212.2.0.61 to 212.2.0.62212.2.0.632
17212.2.0.64/30212.2.0.65 to 212.2.0.66212.2.0.672
18212.2.0.68/30212.2.0.69 to 212.2.0.70212.2.0.712
19212.2.0.72/30212.2.0.73 to 212.2.0.74212.2.0.752
20212.2.0.76/30212.2.0.77 to 212.2.0.78212.2.0.792
21212.2.0.80/30212.2.0.81 to 212.2.0.82212.2.0.832
22212.2.0.84/30212.2.0.85 to 212.2.0.86212.2.0.872
23212.2.0.88/30212.2.0.89 to 212.2.0.90212.2.0.912
24212.2.0.92/30212.2.0.93 to 212.2.0.94212.2.0.952
25212.2.0.96/30212.2.0.97 to 212.2.0.98212.2.0.992
26212.2.0.100/30212.2.0.101 to 212.2.0.102212.2.0.1032
27212.2.0.104/30212.2.0.105 to 212.2.0.106212.2.0.1072
28212.2.0.108/30212.2.0.109 to 212.2.0.110212.2.0.1112
29212.2.0.112/30212.2.0.113 to 212.2.0.114212.2.0.1152
30212.2.0.116/30212.2.0.117 to 212.2.0.118212.2.0.1192
31212.2.0.120/30212.2.0.121 to 212.2.0.122212.2.0.1232
32212.2.0.124/30212.2.0.125 to 212.2.0.126212.2.0.1272
33212.2.0.128/30212.2.0.129 to 212.2.0.130212.2.0.1312
34212.2.0.132/30212.2.0.133 to 212.2.0.134212.2.0.1352
35212.2.0.136/30212.2.0.137 to 212.2.0.138212.2.0.1392
36212.2.0.140/30212.2.0.141 to 212.2.0.142212.2.0.1432
37212.2.0.144/30212.2.0.145 to 212.2.0.146212.2.0.1472
38212.2.0.148/30212.2.0.149 to 212.2.0.150212.2.0.1512
39212.2.0.152/30212.2.0.153 to 212.2.0.154212.2.0.1552
40212.2.0.156/30212.2.0.157 to 212.2.0.158212.2.0.1592
41212.2.0.160/30212.2.0.161 to 212.2.0.162212.2.0.1632
42212.2.0.164/30212.2.0.165 to 212.2.0.166212.2.0.1672
43212.2.0.168/30212.2.0.169 to 212.2.0.170212.2.0.1712
44212.2.0.172/30212.2.0.173 to 212.2.0.174212.2.0.1752
45212.2.0.176/30212.2.0.177 to 212.2.0.178212.2.0.1792
46212.2.0.180/30212.2.0.181 to 212.2.0.182212.2.0.1832
47212.2.0.184/30212.2.0.185 to 212.2.0.186212.2.0.1872
48212.2.0.188/30212.2.0.189 to 212.2.0.190212.2.0.1912
49212.2.0.192/30212.2.0.193 to 212.2.0.194212.2.0.1952
50212.2.0.196/30212.2.0.197 to 212.2.0.198212.2.0.1992
51212.2.0.200/30212.2.0.201 to 212.2.0.202212.2.0.2032
52212.2.0.204/30212.2.0.205 to 212.2.0.206212.2.0.2072
53212.2.0.208/30212.2.0.209 to 212.2.0.210212.2.0.2112
54212.2.0.212/30212.2.0.213 to 212.2.0.214212.2.0.2152
55212.2.0.216/30212.2.0.217 to 212.2.0.218212.2.0.2192
56212.2.0.220/30212.2.0.221 to 212.2.0.222212.2.0.2232
57212.2.0.224/30212.2.0.225 to 212.2.0.226212.2.0.2272
58212.2.0.228/30212.2.0.229 to 212.2.0.230212.2.0.2312
59212.2.0.232/30212.2.0.233 to 212.2.0.234212.2.0.2352
60212.2.0.236/30212.2.0.237 to 212.2.0.238212.2.0.2392
61212.2.0.240/30212.2.0.241 to 212.2.0.242212.2.0.2432
62212.2.0.244/30212.2.0.245 to 212.2.0.246212.2.0.2472
63212.2.0.248/30212.2.0.249 to 212.2.0.250212.2.0.2512
64212.2.0.252/30212.2.0.253 to 212.2.0.254212.2.0.2552
65212.2.1.0/30212.2.1.1 to 212.2.1.2212.2.1.32
66212.2.1.4/30212.2.1.5 to 212.2.1.6212.2.1.72
67212.2.1.8/30212.2.1.9 to 212.2.1.10212.2.1.112
68212.2.1.12/30212.2.1.13 to 212.2.1.14212.2.1.152
69212.2.1.16/30212.2.1.17 to 212.2.1.18212.2.1.192
70212.2.1.20/30212.2.1.21 to 212.2.1.22212.2.1.232
71212.2.1.24/30212.2.1.25 to 212.2.1.26212.2.1.272
72212.2.1.28/30212.2.1.29 to 212.2.1.30212.2.1.312
73212.2.1.32/30212.2.1.33 to 212.2.1.34212.2.1.352
74212.2.1.36/30212.2.1.37 to 212.2.1.38212.2.1.392
75212.2.1.40/30212.2.1.41 to 212.2.1.42212.2.1.432
76212.2.1.44/30212.2.1.45 to 212.2.1.46212.2.1.472
77212.2.1.48/30212.2.1.49 to 212.2.1.50212.2.1.512
78212.2.1.52/30212.2.1.53 to 212.2.1.54212.2.1.552
79212.2.1.56/30212.2.1.57 to 212.2.1.58212.2.1.592
80212.2.1.60/30212.2.1.61 to 212.2.1.62212.2.1.632
81212.2.1.64/30212.2.1.65 to 212.2.1.66212.2.1.672
82212.2.1.68/30212.2.1.69 to 212.2.1.70212.2.1.712
83212.2.1.72/30212.2.1.73 to 212.2.1.74212.2.1.752
84212.2.1.76/30212.2.1.77 to 212.2.1.78212.2.1.792
85212.2.1.80/30212.2.1.81 to 212.2.1.82212.2.1.832
86212.2.1.84/30212.2.1.85 to 212.2.1.86212.2.1.872
87212.2.1.88/30212.2.1.89 to 212.2.1.90212.2.1.912
88212.2.1.92/30212.2.1.93 to 212.2.1.94212.2.1.952
89212.2.1.96/30212.2.1.97 to 212.2.1.98212.2.1.992
90212.2.1.100/30212.2.1.101 to 212.2.1.102212.2.1.1032
91212.2.1.104/30212.2.1.105 to 212.2.1.106212.2.1.1072
92212.2.1.108/30212.2.1.109 to 212.2.1.110212.2.1.1112
93212.2.1.112/30212.2.1.113 to 212.2.1.114212.2.1.1152
94212.2.1.116/30212.2.1.117 to 212.2.1.118212.2.1.1192
95212.2.1.120/30212.2.1.121 to 212.2.1.122212.2.1.1232
96212.2.1.124/30212.2.1.125 to 212.2.1.126212.2.1.1272
97212.2.1.128/30212.2.1.129 to 212.2.1.130212.2.1.1312
98212.2.1.132/30212.2.1.133 to 212.2.1.134212.2.1.1352
99212.2.1.136/30212.2.1.137 to 212.2.1.138212.2.1.1392
100212.2.1.140/30212.2.1.141 to 212.2.1.142212.2.1.1432
101212.2.1.144/30212.2.1.145 to 212.2.1.146212.2.1.1472
102212.2.1.148/30212.2.1.149 to 212.2.1.150212.2.1.1512
103212.2.1.152/30212.2.1.153 to 212.2.1.154212.2.1.1552
104212.2.1.156/30212.2.1.157 to 212.2.1.158212.2.1.1592
105212.2.1.160/30212.2.1.161 to 212.2.1.162212.2.1.1632
106212.2.1.164/30212.2.1.165 to 212.2.1.166212.2.1.1672
107212.2.1.168/30212.2.1.169 to 212.2.1.170212.2.1.1712
108212.2.1.172/30212.2.1.173 to 212.2.1.174212.2.1.1752
109212.2.1.176/30212.2.1.177 to 212.2.1.178212.2.1.1792
110212.2.1.180/30212.2.1.181 to 212.2.1.182212.2.1.1832
111212.2.1.184/30212.2.1.185 to 212.2.1.186212.2.1.1872
112212.2.1.188/30212.2.1.189 to 212.2.1.190212.2.1.1912
113212.2.1.192/30212.2.1.193 to 212.2.1.194212.2.1.1952
114212.2.1.196/30212.2.1.197 to 212.2.1.198212.2.1.1992
115212.2.1.200/30212.2.1.201 to 212.2.1.202212.2.1.2032
116212.2.1.204/30212.2.1.205 to 212.2.1.206212.2.1.2072
117212.2.1.208/30212.2.1.209 to 212.2.1.210212.2.1.2112
118212.2.1.212/30212.2.1.213 to 212.2.1.214212.2.1.2152
119212.2.1.216/30212.2.1.217 to 212.2.1.218212.2.1.2192
120212.2.1.220/30212.2.1.221 to 212.2.1.222212.2.1.2232
121212.2.1.224/30212.2.1.225 to 212.2.1.226212.2.1.2272
122212.2.1.228/30212.2.1.229 to 212.2.1.230212.2.1.2312
123212.2.1.232/30212.2.1.233 to 212.2.1.234212.2.1.2352
124212.2.1.236/30212.2.1.237 to 212.2.1.238212.2.1.2392
125212.2.1.240/30212.2.1.241 to 212.2.1.242212.2.1.2432
126212.2.1.244/30212.2.1.245 to 212.2.1.246212.2.1.2472
127212.2.1.248/30212.2.1.249 to 212.2.1.250212.2.1.2512
128212.2.1.252/30212.2.1.253 to 212.2.1.254212.2.1.2552
129212.2.2.0/30212.2.2.1 to 212.2.2.2212.2.2.32
130212.2.2.4/30212.2.2.5 to 212.2.2.6212.2.2.72
131212.2.2.8/30212.2.2.9 to 212.2.2.10212.2.2.112
132212.2.2.12/30212.2.2.13 to 212.2.2.14212.2.2.152
133212.2.2.16/30212.2.2.17 to 212.2.2.18212.2.2.192
134212.2.2.20/30212.2.2.21 to 212.2.2.22212.2.2.232
135212.2.2.24/30212.2.2.25 to 212.2.2.26212.2.2.272
136212.2.2.28/30212.2.2.29 to 212.2.2.30212.2.2.312
137212.2.2.32/30212.2.2.33 to 212.2.2.34212.2.2.352
138212.2.2.36/30212.2.2.37 to 212.2.2.38212.2.2.392
139212.2.2.40/30212.2.2.41 to 212.2.2.42212.2.2.432
140212.2.2.44/30212.2.2.45 to 212.2.2.46212.2.2.472
141212.2.2.48/30212.2.2.49 to 212.2.2.50212.2.2.512
142212.2.2.52/30212.2.2.53 to 212.2.2.54212.2.2.552
143212.2.2.56/30212.2.2.57 to 212.2.2.58212.2.2.592
144212.2.2.60/30212.2.2.61 to 212.2.2.62212.2.2.632
145212.2.2.64/30212.2.2.65 to 212.2.2.66212.2.2.672
146212.2.2.68/30212.2.2.69 to 212.2.2.70212.2.2.712
147212.2.2.72/30212.2.2.73 to 212.2.2.74212.2.2.752
148212.2.2.76/30212.2.2.77 to 212.2.2.78212.2.2.792
149212.2.2.80/30212.2.2.81 to 212.2.2.82212.2.2.832
150212.2.2.84/30212.2.2.85 to 212.2.2.86212.2.2.872
151212.2.2.88/30212.2.2.89 to 212.2.2.90212.2.2.912
152212.2.2.92/30212.2.2.93 to 212.2.2.94212.2.2.952
153212.2.2.96/30212.2.2.97 to 212.2.2.98212.2.2.992
154212.2.2.100/30212.2.2.101 to 212.2.2.102212.2.2.1032
155212.2.2.104/30212.2.2.105 to 212.2.2.106212.2.2.1072
156212.2.2.108/30212.2.2.109 to 212.2.2.110212.2.2.1112
157212.2.2.112/30212.2.2.113 to 212.2.2.114212.2.2.1152
158212.2.2.116/30212.2.2.117 to 212.2.2.118212.2.2.1192
159212.2.2.120/30212.2.2.121 to 212.2.2.122212.2.2.1232
160212.2.2.124/30212.2.2.125 to 212.2.2.126212.2.2.1272
161212.2.2.128/30212.2.2.129 to 212.2.2.130212.2.2.1312
162212.2.2.132/30212.2.2.133 to 212.2.2.134212.2.2.1352
163212.2.2.136/30212.2.2.137 to 212.2.2.138212.2.2.1392
164212.2.2.140/30212.2.2.141 to 212.2.2.142212.2.2.1432
165212.2.2.144/30212.2.2.145 to 212.2.2.146212.2.2.1472
166212.2.2.148/30212.2.2.149 to 212.2.2.150212.2.2.1512
167212.2.2.152/30212.2.2.153 to 212.2.2.154212.2.2.1552
168212.2.2.156/30212.2.2.157 to 212.2.2.158212.2.2.1592
169212.2.2.160/30212.2.2.161 to 212.2.2.162212.2.2.1632
170212.2.2.164/30212.2.2.165 to 212.2.2.166212.2.2.1672
171212.2.2.168/30212.2.2.169 to 212.2.2.170212.2.2.1712
172212.2.2.172/30212.2.2.173 to 212.2.2.174212.2.2.1752
173212.2.2.176/30212.2.2.177 to 212.2.2.178212.2.2.1792
174212.2.2.180/30212.2.2.181 to 212.2.2.182212.2.2.1832
175212.2.2.184/30212.2.2.185 to 212.2.2.186212.2.2.1872
176212.2.2.188/30212.2.2.189 to 212.2.2.190212.2.2.1912
177212.2.2.192/30212.2.2.193 to 212.2.2.194212.2.2.1952
178212.2.2.196/30212.2.2.197 to 212.2.2.198212.2.2.1992
179212.2.2.200/30212.2.2.201 to 212.2.2.202212.2.2.2032
180212.2.2.204/30212.2.2.205 to 212.2.2.206212.2.2.2072
181212.2.2.208/30212.2.2.209 to 212.2.2.210212.2.2.2112
182212.2.2.212/30212.2.2.213 to 212.2.2.214212.2.2.2152
183212.2.2.216/30212.2.2.217 to 212.2.2.218212.2.2.2192
184212.2.2.220/30212.2.2.221 to 212.2.2.222212.2.2.2232
185212.2.2.224/30212.2.2.225 to 212.2.2.226212.2.2.2272
186212.2.2.228/30212.2.2.229 to 212.2.2.230212.2.2.2312
187212.2.2.232/30212.2.2.233 to 212.2.2.234212.2.2.2352
188212.2.2.236/30212.2.2.237 to 212.2.2.238212.2.2.2392
189212.2.2.240/30212.2.2.241 to 212.2.2.242212.2.2.2432
190212.2.2.244/30212.2.2.245 to 212.2.2.246212.2.2.2472
191212.2.2.248/30212.2.2.249 to 212.2.2.250212.2.2.2512
192212.2.2.252/30212.2.2.253 to 212.2.2.254212.2.2.2552
193212.2.3.0/30212.2.3.1 to 212.2.3.2212.2.3.32
194212.2.3.4/30212.2.3.5 to 212.2.3.6212.2.3.72
195212.2.3.8/30212.2.3.9 to 212.2.3.10212.2.3.112
196212.2.3.12/30212.2.3.13 to 212.2.3.14212.2.3.152
197212.2.3.16/30212.2.3.17 to 212.2.3.18212.2.3.192
198212.2.3.20/30212.2.3.21 to 212.2.3.22212.2.3.232
199212.2.3.24/30212.2.3.25 to 212.2.3.26212.2.3.272
200212.2.3.28/30212.2.3.29 to 212.2.3.30212.2.3.312
201212.2.3.32/30212.2.3.33 to 212.2.3.34212.2.3.352
202212.2.3.36/30212.2.3.37 to 212.2.3.38212.2.3.392
203212.2.3.40/30212.2.3.41 to 212.2.3.42212.2.3.432
204212.2.3.44/30212.2.3.45 to 212.2.3.46212.2.3.472
205212.2.3.48/30212.2.3.49 to 212.2.3.50212.2.3.512
206212.2.3.52/30212.2.3.53 to 212.2.3.54212.2.3.552
207212.2.3.56/30212.2.3.57 to 212.2.3.58212.2.3.592
208212.2.3.60/30212.2.3.61 to 212.2.3.62212.2.3.632
209212.2.3.64/30212.2.3.65 to 212.2.3.66212.2.3.672
210212.2.3.68/30212.2.3.69 to 212.2.3.70212.2.3.712
211212.2.3.72/30212.2.3.73 to 212.2.3.74212.2.3.752
212212.2.3.76/30212.2.3.77 to 212.2.3.78212.2.3.792
213212.2.3.80/30212.2.3.81 to 212.2.3.82212.2.3.832
214212.2.3.84/30212.2.3.85 to 212.2.3.86212.2.3.872
215212.2.3.88/30212.2.3.89 to 212.2.3.90212.2.3.912
216212.2.3.92/30212.2.3.93 to 212.2.3.94212.2.3.952
217212.2.3.96/30212.2.3.97 to 212.2.3.98212.2.3.992
218212.2.3.100/30212.2.3.101 to 212.2.3.102212.2.3.1032
219212.2.3.104/30212.2.3.105 to 212.2.3.106212.2.3.1072
220212.2.3.108/30212.2.3.109 to 212.2.3.110212.2.3.1112
221212.2.3.112/30212.2.3.113 to 212.2.3.114212.2.3.1152
222212.2.3.116/30212.2.3.117 to 212.2.3.118212.2.3.1192
223212.2.3.120/30212.2.3.121 to 212.2.3.122212.2.3.1232
224212.2.3.124/30212.2.3.125 to 212.2.3.126212.2.3.1272
225212.2.3.128/30212.2.3.129 to 212.2.3.130212.2.3.1312
226212.2.3.132/30212.2.3.133 to 212.2.3.134212.2.3.1352
227212.2.3.136/30212.2.3.137 to 212.2.3.138212.2.3.1392
228212.2.3.140/30212.2.3.141 to 212.2.3.142212.2.3.1432
229212.2.3.144/30212.2.3.145 to 212.2.3.146212.2.3.1472
230212.2.3.148/30212.2.3.149 to 212.2.3.150212.2.3.1512
231212.2.3.152/30212.2.3.153 to 212.2.3.154212.2.3.1552
232212.2.3.156/30212.2.3.157 to 212.2.3.158212.2.3.1592
233212.2.3.160/30212.2.3.161 to 212.2.3.162212.2.3.1632
234212.2.3.164/30212.2.3.165 to 212.2.3.166212.2.3.1672
235212.2.3.168/30212.2.3.169 to 212.2.3.170212.2.3.1712
236212.2.3.172/30212.2.3.173 to 212.2.3.174212.2.3.1752
237212.2.3.176/30212.2.3.177 to 212.2.3.178212.2.3.1792
238212.2.3.180/30212.2.3.181 to 212.2.3.182212.2.3.1832
239212.2.3.184/30212.2.3.185 to 212.2.3.186212.2.3.1872
240212.2.3.188/30212.2.3.189 to 212.2.3.190212.2.3.1912
241212.2.3.192/30212.2.3.193 to 212.2.3.194212.2.3.1952
242212.2.3.196/30212.2.3.197 to 212.2.3.198212.2.3.1992
243212.2.3.200/30212.2.3.201 to 212.2.3.202212.2.3.2032
244212.2.3.204/30212.2.3.205 to 212.2.3.206212.2.3.2072
245212.2.3.208/30212.2.3.209 to 212.2.3.210212.2.3.2112
246212.2.3.212/30212.2.3.213 to 212.2.3.214212.2.3.2152
247212.2.3.216/30212.2.3.217 to 212.2.3.218212.2.3.2192
248212.2.3.220/30212.2.3.221 to 212.2.3.222212.2.3.2232
249212.2.3.224/30212.2.3.225 to 212.2.3.226212.2.3.2272
250212.2.3.228/30212.2.3.229 to 212.2.3.230212.2.3.2312
251212.2.3.232/30212.2.3.233 to 212.2.3.234212.2.3.2352
252212.2.3.236/30212.2.3.237 to 212.2.3.238212.2.3.2392
253212.2.3.240/30212.2.3.241 to 212.2.3.242212.2.3.2432
254212.2.3.244/30212.2.3.245 to 212.2.3.246212.2.3.2472
255212.2.3.248/30212.2.3.249 to 212.2.3.250212.2.3.2512
256212.2.3.252/30212.2.3.253 to 212.2.3.254212.2.3.2552

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.