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.

Network187.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
187.0.0.0
Broadcast address
187.255.255.255
First usable
187.0.0.1
Last usable
187.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Public public
Old class
B (default /16)
As numbers
Hex BB000000 · Integer 3137339392 to 3154116607
Reverse DNS zone
187.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10111011..00000000.00000000.00000000187.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network10111011..00000000.00000000.00000000187.0.0.0
Broadcast10111011..11111111.11111111.11111111187.255.255.255
Split into smaller subnets/19
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

187.0.0.0/8 makes 2,048 subnets of /19; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1187.0.0.0/19187.0.0.1 to 187.0.31.254187.0.31.2558,190
2187.0.32.0/19187.0.32.1 to 187.0.63.254187.0.63.2558,190
3187.0.64.0/19187.0.64.1 to 187.0.95.254187.0.95.2558,190
4187.0.96.0/19187.0.96.1 to 187.0.127.254187.0.127.2558,190
5187.0.128.0/19187.0.128.1 to 187.0.159.254187.0.159.2558,190
6187.0.160.0/19187.0.160.1 to 187.0.191.254187.0.191.2558,190
7187.0.192.0/19187.0.192.1 to 187.0.223.254187.0.223.2558,190
8187.0.224.0/19187.0.224.1 to 187.0.255.254187.0.255.2558,190
9187.1.0.0/19187.1.0.1 to 187.1.31.254187.1.31.2558,190
10187.1.32.0/19187.1.32.1 to 187.1.63.254187.1.63.2558,190
11187.1.64.0/19187.1.64.1 to 187.1.95.254187.1.95.2558,190
12187.1.96.0/19187.1.96.1 to 187.1.127.254187.1.127.2558,190
13187.1.128.0/19187.1.128.1 to 187.1.159.254187.1.159.2558,190
14187.1.160.0/19187.1.160.1 to 187.1.191.254187.1.191.2558,190
15187.1.192.0/19187.1.192.1 to 187.1.223.254187.1.223.2558,190
16187.1.224.0/19187.1.224.1 to 187.1.255.254187.1.255.2558,190
17187.2.0.0/19187.2.0.1 to 187.2.31.254187.2.31.2558,190
18187.2.32.0/19187.2.32.1 to 187.2.63.254187.2.63.2558,190
19187.2.64.0/19187.2.64.1 to 187.2.95.254187.2.95.2558,190
20187.2.96.0/19187.2.96.1 to 187.2.127.254187.2.127.2558,190
21187.2.128.0/19187.2.128.1 to 187.2.159.254187.2.159.2558,190
22187.2.160.0/19187.2.160.1 to 187.2.191.254187.2.191.2558,190
23187.2.192.0/19187.2.192.1 to 187.2.223.254187.2.223.2558,190
24187.2.224.0/19187.2.224.1 to 187.2.255.254187.2.255.2558,190
25187.3.0.0/19187.3.0.1 to 187.3.31.254187.3.31.2558,190
26187.3.32.0/19187.3.32.1 to 187.3.63.254187.3.63.2558,190
27187.3.64.0/19187.3.64.1 to 187.3.95.254187.3.95.2558,190
28187.3.96.0/19187.3.96.1 to 187.3.127.254187.3.127.2558,190
29187.3.128.0/19187.3.128.1 to 187.3.159.254187.3.159.2558,190
30187.3.160.0/19187.3.160.1 to 187.3.191.254187.3.191.2558,190
31187.3.192.0/19187.3.192.1 to 187.3.223.254187.3.223.2558,190
32187.3.224.0/19187.3.224.1 to 187.3.255.254187.3.255.2558,190
33187.4.0.0/19187.4.0.1 to 187.4.31.254187.4.31.2558,190
34187.4.32.0/19187.4.32.1 to 187.4.63.254187.4.63.2558,190
35187.4.64.0/19187.4.64.1 to 187.4.95.254187.4.95.2558,190
36187.4.96.0/19187.4.96.1 to 187.4.127.254187.4.127.2558,190
37187.4.128.0/19187.4.128.1 to 187.4.159.254187.4.159.2558,190
38187.4.160.0/19187.4.160.1 to 187.4.191.254187.4.191.2558,190
39187.4.192.0/19187.4.192.1 to 187.4.223.254187.4.223.2558,190
40187.4.224.0/19187.4.224.1 to 187.4.255.254187.4.255.2558,190
41187.5.0.0/19187.5.0.1 to 187.5.31.254187.5.31.2558,190
42187.5.32.0/19187.5.32.1 to 187.5.63.254187.5.63.2558,190
43187.5.64.0/19187.5.64.1 to 187.5.95.254187.5.95.2558,190
44187.5.96.0/19187.5.96.1 to 187.5.127.254187.5.127.2558,190
45187.5.128.0/19187.5.128.1 to 187.5.159.254187.5.159.2558,190
46187.5.160.0/19187.5.160.1 to 187.5.191.254187.5.191.2558,190
47187.5.192.0/19187.5.192.1 to 187.5.223.254187.5.223.2558,190
48187.5.224.0/19187.5.224.1 to 187.5.255.254187.5.255.2558,190
49187.6.0.0/19187.6.0.1 to 187.6.31.254187.6.31.2558,190
50187.6.32.0/19187.6.32.1 to 187.6.63.254187.6.63.2558,190
51187.6.64.0/19187.6.64.1 to 187.6.95.254187.6.95.2558,190
52187.6.96.0/19187.6.96.1 to 187.6.127.254187.6.127.2558,190
53187.6.128.0/19187.6.128.1 to 187.6.159.254187.6.159.2558,190
54187.6.160.0/19187.6.160.1 to 187.6.191.254187.6.191.2558,190
55187.6.192.0/19187.6.192.1 to 187.6.223.254187.6.223.2558,190
56187.6.224.0/19187.6.224.1 to 187.6.255.254187.6.255.2558,190
57187.7.0.0/19187.7.0.1 to 187.7.31.254187.7.31.2558,190
58187.7.32.0/19187.7.32.1 to 187.7.63.254187.7.63.2558,190
59187.7.64.0/19187.7.64.1 to 187.7.95.254187.7.95.2558,190
60187.7.96.0/19187.7.96.1 to 187.7.127.254187.7.127.2558,190
61187.7.128.0/19187.7.128.1 to 187.7.159.254187.7.159.2558,190
62187.7.160.0/19187.7.160.1 to 187.7.191.254187.7.191.2558,190
63187.7.192.0/19187.7.192.1 to 187.7.223.254187.7.223.2558,190
64187.7.224.0/19187.7.224.1 to 187.7.255.254187.7.255.2558,190
65187.8.0.0/19187.8.0.1 to 187.8.31.254187.8.31.2558,190
66187.8.32.0/19187.8.32.1 to 187.8.63.254187.8.63.2558,190
67187.8.64.0/19187.8.64.1 to 187.8.95.254187.8.95.2558,190
68187.8.96.0/19187.8.96.1 to 187.8.127.254187.8.127.2558,190
69187.8.128.0/19187.8.128.1 to 187.8.159.254187.8.159.2558,190
70187.8.160.0/19187.8.160.1 to 187.8.191.254187.8.191.2558,190
71187.8.192.0/19187.8.192.1 to 187.8.223.254187.8.223.2558,190
72187.8.224.0/19187.8.224.1 to 187.8.255.254187.8.255.2558,190
73187.9.0.0/19187.9.0.1 to 187.9.31.254187.9.31.2558,190
74187.9.32.0/19187.9.32.1 to 187.9.63.254187.9.63.2558,190
75187.9.64.0/19187.9.64.1 to 187.9.95.254187.9.95.2558,190
76187.9.96.0/19187.9.96.1 to 187.9.127.254187.9.127.2558,190
77187.9.128.0/19187.9.128.1 to 187.9.159.254187.9.159.2558,190
78187.9.160.0/19187.9.160.1 to 187.9.191.254187.9.191.2558,190
79187.9.192.0/19187.9.192.1 to 187.9.223.254187.9.223.2558,190
80187.9.224.0/19187.9.224.1 to 187.9.255.254187.9.255.2558,190
81187.10.0.0/19187.10.0.1 to 187.10.31.254187.10.31.2558,190
82187.10.32.0/19187.10.32.1 to 187.10.63.254187.10.63.2558,190
83187.10.64.0/19187.10.64.1 to 187.10.95.254187.10.95.2558,190
84187.10.96.0/19187.10.96.1 to 187.10.127.254187.10.127.2558,190
85187.10.128.0/19187.10.128.1 to 187.10.159.254187.10.159.2558,190
86187.10.160.0/19187.10.160.1 to 187.10.191.254187.10.191.2558,190
87187.10.192.0/19187.10.192.1 to 187.10.223.254187.10.223.2558,190
88187.10.224.0/19187.10.224.1 to 187.10.255.254187.10.255.2558,190
89187.11.0.0/19187.11.0.1 to 187.11.31.254187.11.31.2558,190
90187.11.32.0/19187.11.32.1 to 187.11.63.254187.11.63.2558,190
91187.11.64.0/19187.11.64.1 to 187.11.95.254187.11.95.2558,190
92187.11.96.0/19187.11.96.1 to 187.11.127.254187.11.127.2558,190
93187.11.128.0/19187.11.128.1 to 187.11.159.254187.11.159.2558,190
94187.11.160.0/19187.11.160.1 to 187.11.191.254187.11.191.2558,190
95187.11.192.0/19187.11.192.1 to 187.11.223.254187.11.223.2558,190
96187.11.224.0/19187.11.224.1 to 187.11.255.254187.11.255.2558,190
97187.12.0.0/19187.12.0.1 to 187.12.31.254187.12.31.2558,190
98187.12.32.0/19187.12.32.1 to 187.12.63.254187.12.63.2558,190
99187.12.64.0/19187.12.64.1 to 187.12.95.254187.12.95.2558,190
100187.12.96.0/19187.12.96.1 to 187.12.127.254187.12.127.2558,190
101187.12.128.0/19187.12.128.1 to 187.12.159.254187.12.159.2558,190
102187.12.160.0/19187.12.160.1 to 187.12.191.254187.12.191.2558,190
103187.12.192.0/19187.12.192.1 to 187.12.223.254187.12.223.2558,190
104187.12.224.0/19187.12.224.1 to 187.12.255.254187.12.255.2558,190
105187.13.0.0/19187.13.0.1 to 187.13.31.254187.13.31.2558,190
106187.13.32.0/19187.13.32.1 to 187.13.63.254187.13.63.2558,190
107187.13.64.0/19187.13.64.1 to 187.13.95.254187.13.95.2558,190
108187.13.96.0/19187.13.96.1 to 187.13.127.254187.13.127.2558,190
109187.13.128.0/19187.13.128.1 to 187.13.159.254187.13.159.2558,190
110187.13.160.0/19187.13.160.1 to 187.13.191.254187.13.191.2558,190
111187.13.192.0/19187.13.192.1 to 187.13.223.254187.13.223.2558,190
112187.13.224.0/19187.13.224.1 to 187.13.255.254187.13.255.2558,190
113187.14.0.0/19187.14.0.1 to 187.14.31.254187.14.31.2558,190
114187.14.32.0/19187.14.32.1 to 187.14.63.254187.14.63.2558,190
115187.14.64.0/19187.14.64.1 to 187.14.95.254187.14.95.2558,190
116187.14.96.0/19187.14.96.1 to 187.14.127.254187.14.127.2558,190
117187.14.128.0/19187.14.128.1 to 187.14.159.254187.14.159.2558,190
118187.14.160.0/19187.14.160.1 to 187.14.191.254187.14.191.2558,190
119187.14.192.0/19187.14.192.1 to 187.14.223.254187.14.223.2558,190
120187.14.224.0/19187.14.224.1 to 187.14.255.254187.14.255.2558,190
121187.15.0.0/19187.15.0.1 to 187.15.31.254187.15.31.2558,190
122187.15.32.0/19187.15.32.1 to 187.15.63.254187.15.63.2558,190
123187.15.64.0/19187.15.64.1 to 187.15.95.254187.15.95.2558,190
124187.15.96.0/19187.15.96.1 to 187.15.127.254187.15.127.2558,190
125187.15.128.0/19187.15.128.1 to 187.15.159.254187.15.159.2558,190
126187.15.160.0/19187.15.160.1 to 187.15.191.254187.15.191.2558,190
127187.15.192.0/19187.15.192.1 to 187.15.223.254187.15.223.2558,190
128187.15.224.0/19187.15.224.1 to 187.15.255.254187.15.255.2558,190
129187.16.0.0/19187.16.0.1 to 187.16.31.254187.16.31.2558,190
130187.16.32.0/19187.16.32.1 to 187.16.63.254187.16.63.2558,190
131187.16.64.0/19187.16.64.1 to 187.16.95.254187.16.95.2558,190
132187.16.96.0/19187.16.96.1 to 187.16.127.254187.16.127.2558,190
133187.16.128.0/19187.16.128.1 to 187.16.159.254187.16.159.2558,190
134187.16.160.0/19187.16.160.1 to 187.16.191.254187.16.191.2558,190
135187.16.192.0/19187.16.192.1 to 187.16.223.254187.16.223.2558,190
136187.16.224.0/19187.16.224.1 to 187.16.255.254187.16.255.2558,190
137187.17.0.0/19187.17.0.1 to 187.17.31.254187.17.31.2558,190
138187.17.32.0/19187.17.32.1 to 187.17.63.254187.17.63.2558,190
139187.17.64.0/19187.17.64.1 to 187.17.95.254187.17.95.2558,190
140187.17.96.0/19187.17.96.1 to 187.17.127.254187.17.127.2558,190
141187.17.128.0/19187.17.128.1 to 187.17.159.254187.17.159.2558,190
142187.17.160.0/19187.17.160.1 to 187.17.191.254187.17.191.2558,190
143187.17.192.0/19187.17.192.1 to 187.17.223.254187.17.223.2558,190
144187.17.224.0/19187.17.224.1 to 187.17.255.254187.17.255.2558,190
145187.18.0.0/19187.18.0.1 to 187.18.31.254187.18.31.2558,190
146187.18.32.0/19187.18.32.1 to 187.18.63.254187.18.63.2558,190
147187.18.64.0/19187.18.64.1 to 187.18.95.254187.18.95.2558,190
148187.18.96.0/19187.18.96.1 to 187.18.127.254187.18.127.2558,190
149187.18.128.0/19187.18.128.1 to 187.18.159.254187.18.159.2558,190
150187.18.160.0/19187.18.160.1 to 187.18.191.254187.18.191.2558,190
151187.18.192.0/19187.18.192.1 to 187.18.223.254187.18.223.2558,190
152187.18.224.0/19187.18.224.1 to 187.18.255.254187.18.255.2558,190
153187.19.0.0/19187.19.0.1 to 187.19.31.254187.19.31.2558,190
154187.19.32.0/19187.19.32.1 to 187.19.63.254187.19.63.2558,190
155187.19.64.0/19187.19.64.1 to 187.19.95.254187.19.95.2558,190
156187.19.96.0/19187.19.96.1 to 187.19.127.254187.19.127.2558,190
157187.19.128.0/19187.19.128.1 to 187.19.159.254187.19.159.2558,190
158187.19.160.0/19187.19.160.1 to 187.19.191.254187.19.191.2558,190
159187.19.192.0/19187.19.192.1 to 187.19.223.254187.19.223.2558,190
160187.19.224.0/19187.19.224.1 to 187.19.255.254187.19.255.2558,190
161187.20.0.0/19187.20.0.1 to 187.20.31.254187.20.31.2558,190
162187.20.32.0/19187.20.32.1 to 187.20.63.254187.20.63.2558,190
163187.20.64.0/19187.20.64.1 to 187.20.95.254187.20.95.2558,190
164187.20.96.0/19187.20.96.1 to 187.20.127.254187.20.127.2558,190
165187.20.128.0/19187.20.128.1 to 187.20.159.254187.20.159.2558,190
166187.20.160.0/19187.20.160.1 to 187.20.191.254187.20.191.2558,190
167187.20.192.0/19187.20.192.1 to 187.20.223.254187.20.223.2558,190
168187.20.224.0/19187.20.224.1 to 187.20.255.254187.20.255.2558,190
169187.21.0.0/19187.21.0.1 to 187.21.31.254187.21.31.2558,190
170187.21.32.0/19187.21.32.1 to 187.21.63.254187.21.63.2558,190
171187.21.64.0/19187.21.64.1 to 187.21.95.254187.21.95.2558,190
172187.21.96.0/19187.21.96.1 to 187.21.127.254187.21.127.2558,190
173187.21.128.0/19187.21.128.1 to 187.21.159.254187.21.159.2558,190
174187.21.160.0/19187.21.160.1 to 187.21.191.254187.21.191.2558,190
175187.21.192.0/19187.21.192.1 to 187.21.223.254187.21.223.2558,190
176187.21.224.0/19187.21.224.1 to 187.21.255.254187.21.255.2558,190
177187.22.0.0/19187.22.0.1 to 187.22.31.254187.22.31.2558,190
178187.22.32.0/19187.22.32.1 to 187.22.63.254187.22.63.2558,190
179187.22.64.0/19187.22.64.1 to 187.22.95.254187.22.95.2558,190
180187.22.96.0/19187.22.96.1 to 187.22.127.254187.22.127.2558,190
181187.22.128.0/19187.22.128.1 to 187.22.159.254187.22.159.2558,190
182187.22.160.0/19187.22.160.1 to 187.22.191.254187.22.191.2558,190
183187.22.192.0/19187.22.192.1 to 187.22.223.254187.22.223.2558,190
184187.22.224.0/19187.22.224.1 to 187.22.255.254187.22.255.2558,190
185187.23.0.0/19187.23.0.1 to 187.23.31.254187.23.31.2558,190
186187.23.32.0/19187.23.32.1 to 187.23.63.254187.23.63.2558,190
187187.23.64.0/19187.23.64.1 to 187.23.95.254187.23.95.2558,190
188187.23.96.0/19187.23.96.1 to 187.23.127.254187.23.127.2558,190
189187.23.128.0/19187.23.128.1 to 187.23.159.254187.23.159.2558,190
190187.23.160.0/19187.23.160.1 to 187.23.191.254187.23.191.2558,190
191187.23.192.0/19187.23.192.1 to 187.23.223.254187.23.223.2558,190
192187.23.224.0/19187.23.224.1 to 187.23.255.254187.23.255.2558,190
193187.24.0.0/19187.24.0.1 to 187.24.31.254187.24.31.2558,190
194187.24.32.0/19187.24.32.1 to 187.24.63.254187.24.63.2558,190
195187.24.64.0/19187.24.64.1 to 187.24.95.254187.24.95.2558,190
196187.24.96.0/19187.24.96.1 to 187.24.127.254187.24.127.2558,190
197187.24.128.0/19187.24.128.1 to 187.24.159.254187.24.159.2558,190
198187.24.160.0/19187.24.160.1 to 187.24.191.254187.24.191.2558,190
199187.24.192.0/19187.24.192.1 to 187.24.223.254187.24.223.2558,190
200187.24.224.0/19187.24.224.1 to 187.24.255.254187.24.255.2558,190
201187.25.0.0/19187.25.0.1 to 187.25.31.254187.25.31.2558,190
202187.25.32.0/19187.25.32.1 to 187.25.63.254187.25.63.2558,190
203187.25.64.0/19187.25.64.1 to 187.25.95.254187.25.95.2558,190
204187.25.96.0/19187.25.96.1 to 187.25.127.254187.25.127.2558,190
205187.25.128.0/19187.25.128.1 to 187.25.159.254187.25.159.2558,190
206187.25.160.0/19187.25.160.1 to 187.25.191.254187.25.191.2558,190
207187.25.192.0/19187.25.192.1 to 187.25.223.254187.25.223.2558,190
208187.25.224.0/19187.25.224.1 to 187.25.255.254187.25.255.2558,190
209187.26.0.0/19187.26.0.1 to 187.26.31.254187.26.31.2558,190
210187.26.32.0/19187.26.32.1 to 187.26.63.254187.26.63.2558,190
211187.26.64.0/19187.26.64.1 to 187.26.95.254187.26.95.2558,190
212187.26.96.0/19187.26.96.1 to 187.26.127.254187.26.127.2558,190
213187.26.128.0/19187.26.128.1 to 187.26.159.254187.26.159.2558,190
214187.26.160.0/19187.26.160.1 to 187.26.191.254187.26.191.2558,190
215187.26.192.0/19187.26.192.1 to 187.26.223.254187.26.223.2558,190
216187.26.224.0/19187.26.224.1 to 187.26.255.254187.26.255.2558,190
217187.27.0.0/19187.27.0.1 to 187.27.31.254187.27.31.2558,190
218187.27.32.0/19187.27.32.1 to 187.27.63.254187.27.63.2558,190
219187.27.64.0/19187.27.64.1 to 187.27.95.254187.27.95.2558,190
220187.27.96.0/19187.27.96.1 to 187.27.127.254187.27.127.2558,190
221187.27.128.0/19187.27.128.1 to 187.27.159.254187.27.159.2558,190
222187.27.160.0/19187.27.160.1 to 187.27.191.254187.27.191.2558,190
223187.27.192.0/19187.27.192.1 to 187.27.223.254187.27.223.2558,190
224187.27.224.0/19187.27.224.1 to 187.27.255.254187.27.255.2558,190
225187.28.0.0/19187.28.0.1 to 187.28.31.254187.28.31.2558,190
226187.28.32.0/19187.28.32.1 to 187.28.63.254187.28.63.2558,190
227187.28.64.0/19187.28.64.1 to 187.28.95.254187.28.95.2558,190
228187.28.96.0/19187.28.96.1 to 187.28.127.254187.28.127.2558,190
229187.28.128.0/19187.28.128.1 to 187.28.159.254187.28.159.2558,190
230187.28.160.0/19187.28.160.1 to 187.28.191.254187.28.191.2558,190
231187.28.192.0/19187.28.192.1 to 187.28.223.254187.28.223.2558,190
232187.28.224.0/19187.28.224.1 to 187.28.255.254187.28.255.2558,190
233187.29.0.0/19187.29.0.1 to 187.29.31.254187.29.31.2558,190
234187.29.32.0/19187.29.32.1 to 187.29.63.254187.29.63.2558,190
235187.29.64.0/19187.29.64.1 to 187.29.95.254187.29.95.2558,190
236187.29.96.0/19187.29.96.1 to 187.29.127.254187.29.127.2558,190
237187.29.128.0/19187.29.128.1 to 187.29.159.254187.29.159.2558,190
238187.29.160.0/19187.29.160.1 to 187.29.191.254187.29.191.2558,190
239187.29.192.0/19187.29.192.1 to 187.29.223.254187.29.223.2558,190
240187.29.224.0/19187.29.224.1 to 187.29.255.254187.29.255.2558,190
241187.30.0.0/19187.30.0.1 to 187.30.31.254187.30.31.2558,190
242187.30.32.0/19187.30.32.1 to 187.30.63.254187.30.63.2558,190
243187.30.64.0/19187.30.64.1 to 187.30.95.254187.30.95.2558,190
244187.30.96.0/19187.30.96.1 to 187.30.127.254187.30.127.2558,190
245187.30.128.0/19187.30.128.1 to 187.30.159.254187.30.159.2558,190
246187.30.160.0/19187.30.160.1 to 187.30.191.254187.30.191.2558,190
247187.30.192.0/19187.30.192.1 to 187.30.223.254187.30.223.2558,190
248187.30.224.0/19187.30.224.1 to 187.30.255.254187.30.255.2558,190
249187.31.0.0/19187.31.0.1 to 187.31.31.254187.31.31.2558,190
250187.31.32.0/19187.31.32.1 to 187.31.63.254187.31.63.2558,190
251187.31.64.0/19187.31.64.1 to 187.31.95.254187.31.95.2558,190
252187.31.96.0/19187.31.96.1 to 187.31.127.254187.31.127.2558,190
253187.31.128.0/19187.31.128.1 to 187.31.159.254187.31.159.2558,190
254187.31.160.0/19187.31.160.1 to 187.31.191.254187.31.191.2558,190
255187.31.192.0/19187.31.192.1 to 187.31.223.254187.31.223.2558,190
256187.31.224.0/19187.31.224.1 to 187.31.255.254187.31.255.2558,190

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.