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.

Network115.131.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
115.131.0.0
Broadcast address
115.131.255.255
First usable
115.131.0.1
Last usable
115.131.255.254
Usable hosts
65,534 (65,536 less the network and broadcast addresses)
Subnet mask
255.255.0.0
Wildcard mask
0.0.255.255 (Cisco ACLs, OSPF)
Prefix length
/16
Type
Public public
Old class
A (default /8)
As numbers
Hex 73830000 · Integer 1937965056 to 1938030591
Reverse DNS zone
131.115.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01110011.10000011..00000000.00000000115.131.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network01110011.10000011..00000000.00000000115.131.0.0
Broadcast01110011.10000011..11111111.11111111115.131.255.255
Split into smaller subnets/25
/17 (2)/18 (4)/19 (8)/20 (16)/21 (32)/22 (64)/23 (128)/24 (256)/25 (512)/26 (1,024)/27 (2,048)/28 (4,096)

115.131.0.0/16 makes 512 subnets of /25; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1115.131.0.0/25115.131.0.1 to 115.131.0.126115.131.0.127126
2115.131.0.128/25115.131.0.129 to 115.131.0.254115.131.0.255126
3115.131.1.0/25115.131.1.1 to 115.131.1.126115.131.1.127126
4115.131.1.128/25115.131.1.129 to 115.131.1.254115.131.1.255126
5115.131.2.0/25115.131.2.1 to 115.131.2.126115.131.2.127126
6115.131.2.128/25115.131.2.129 to 115.131.2.254115.131.2.255126
7115.131.3.0/25115.131.3.1 to 115.131.3.126115.131.3.127126
8115.131.3.128/25115.131.3.129 to 115.131.3.254115.131.3.255126
9115.131.4.0/25115.131.4.1 to 115.131.4.126115.131.4.127126
10115.131.4.128/25115.131.4.129 to 115.131.4.254115.131.4.255126
11115.131.5.0/25115.131.5.1 to 115.131.5.126115.131.5.127126
12115.131.5.128/25115.131.5.129 to 115.131.5.254115.131.5.255126
13115.131.6.0/25115.131.6.1 to 115.131.6.126115.131.6.127126
14115.131.6.128/25115.131.6.129 to 115.131.6.254115.131.6.255126
15115.131.7.0/25115.131.7.1 to 115.131.7.126115.131.7.127126
16115.131.7.128/25115.131.7.129 to 115.131.7.254115.131.7.255126
17115.131.8.0/25115.131.8.1 to 115.131.8.126115.131.8.127126
18115.131.8.128/25115.131.8.129 to 115.131.8.254115.131.8.255126
19115.131.9.0/25115.131.9.1 to 115.131.9.126115.131.9.127126
20115.131.9.128/25115.131.9.129 to 115.131.9.254115.131.9.255126
21115.131.10.0/25115.131.10.1 to 115.131.10.126115.131.10.127126
22115.131.10.128/25115.131.10.129 to 115.131.10.254115.131.10.255126
23115.131.11.0/25115.131.11.1 to 115.131.11.126115.131.11.127126
24115.131.11.128/25115.131.11.129 to 115.131.11.254115.131.11.255126
25115.131.12.0/25115.131.12.1 to 115.131.12.126115.131.12.127126
26115.131.12.128/25115.131.12.129 to 115.131.12.254115.131.12.255126
27115.131.13.0/25115.131.13.1 to 115.131.13.126115.131.13.127126
28115.131.13.128/25115.131.13.129 to 115.131.13.254115.131.13.255126
29115.131.14.0/25115.131.14.1 to 115.131.14.126115.131.14.127126
30115.131.14.128/25115.131.14.129 to 115.131.14.254115.131.14.255126
31115.131.15.0/25115.131.15.1 to 115.131.15.126115.131.15.127126
32115.131.15.128/25115.131.15.129 to 115.131.15.254115.131.15.255126
33115.131.16.0/25115.131.16.1 to 115.131.16.126115.131.16.127126
34115.131.16.128/25115.131.16.129 to 115.131.16.254115.131.16.255126
35115.131.17.0/25115.131.17.1 to 115.131.17.126115.131.17.127126
36115.131.17.128/25115.131.17.129 to 115.131.17.254115.131.17.255126
37115.131.18.0/25115.131.18.1 to 115.131.18.126115.131.18.127126
38115.131.18.128/25115.131.18.129 to 115.131.18.254115.131.18.255126
39115.131.19.0/25115.131.19.1 to 115.131.19.126115.131.19.127126
40115.131.19.128/25115.131.19.129 to 115.131.19.254115.131.19.255126
41115.131.20.0/25115.131.20.1 to 115.131.20.126115.131.20.127126
42115.131.20.128/25115.131.20.129 to 115.131.20.254115.131.20.255126
43115.131.21.0/25115.131.21.1 to 115.131.21.126115.131.21.127126
44115.131.21.128/25115.131.21.129 to 115.131.21.254115.131.21.255126
45115.131.22.0/25115.131.22.1 to 115.131.22.126115.131.22.127126
46115.131.22.128/25115.131.22.129 to 115.131.22.254115.131.22.255126
47115.131.23.0/25115.131.23.1 to 115.131.23.126115.131.23.127126
48115.131.23.128/25115.131.23.129 to 115.131.23.254115.131.23.255126
49115.131.24.0/25115.131.24.1 to 115.131.24.126115.131.24.127126
50115.131.24.128/25115.131.24.129 to 115.131.24.254115.131.24.255126
51115.131.25.0/25115.131.25.1 to 115.131.25.126115.131.25.127126
52115.131.25.128/25115.131.25.129 to 115.131.25.254115.131.25.255126
53115.131.26.0/25115.131.26.1 to 115.131.26.126115.131.26.127126
54115.131.26.128/25115.131.26.129 to 115.131.26.254115.131.26.255126
55115.131.27.0/25115.131.27.1 to 115.131.27.126115.131.27.127126
56115.131.27.128/25115.131.27.129 to 115.131.27.254115.131.27.255126
57115.131.28.0/25115.131.28.1 to 115.131.28.126115.131.28.127126
58115.131.28.128/25115.131.28.129 to 115.131.28.254115.131.28.255126
59115.131.29.0/25115.131.29.1 to 115.131.29.126115.131.29.127126
60115.131.29.128/25115.131.29.129 to 115.131.29.254115.131.29.255126
61115.131.30.0/25115.131.30.1 to 115.131.30.126115.131.30.127126
62115.131.30.128/25115.131.30.129 to 115.131.30.254115.131.30.255126
63115.131.31.0/25115.131.31.1 to 115.131.31.126115.131.31.127126
64115.131.31.128/25115.131.31.129 to 115.131.31.254115.131.31.255126
65115.131.32.0/25115.131.32.1 to 115.131.32.126115.131.32.127126
66115.131.32.128/25115.131.32.129 to 115.131.32.254115.131.32.255126
67115.131.33.0/25115.131.33.1 to 115.131.33.126115.131.33.127126
68115.131.33.128/25115.131.33.129 to 115.131.33.254115.131.33.255126
69115.131.34.0/25115.131.34.1 to 115.131.34.126115.131.34.127126
70115.131.34.128/25115.131.34.129 to 115.131.34.254115.131.34.255126
71115.131.35.0/25115.131.35.1 to 115.131.35.126115.131.35.127126
72115.131.35.128/25115.131.35.129 to 115.131.35.254115.131.35.255126
73115.131.36.0/25115.131.36.1 to 115.131.36.126115.131.36.127126
74115.131.36.128/25115.131.36.129 to 115.131.36.254115.131.36.255126
75115.131.37.0/25115.131.37.1 to 115.131.37.126115.131.37.127126
76115.131.37.128/25115.131.37.129 to 115.131.37.254115.131.37.255126
77115.131.38.0/25115.131.38.1 to 115.131.38.126115.131.38.127126
78115.131.38.128/25115.131.38.129 to 115.131.38.254115.131.38.255126
79115.131.39.0/25115.131.39.1 to 115.131.39.126115.131.39.127126
80115.131.39.128/25115.131.39.129 to 115.131.39.254115.131.39.255126
81115.131.40.0/25115.131.40.1 to 115.131.40.126115.131.40.127126
82115.131.40.128/25115.131.40.129 to 115.131.40.254115.131.40.255126
83115.131.41.0/25115.131.41.1 to 115.131.41.126115.131.41.127126
84115.131.41.128/25115.131.41.129 to 115.131.41.254115.131.41.255126
85115.131.42.0/25115.131.42.1 to 115.131.42.126115.131.42.127126
86115.131.42.128/25115.131.42.129 to 115.131.42.254115.131.42.255126
87115.131.43.0/25115.131.43.1 to 115.131.43.126115.131.43.127126
88115.131.43.128/25115.131.43.129 to 115.131.43.254115.131.43.255126
89115.131.44.0/25115.131.44.1 to 115.131.44.126115.131.44.127126
90115.131.44.128/25115.131.44.129 to 115.131.44.254115.131.44.255126
91115.131.45.0/25115.131.45.1 to 115.131.45.126115.131.45.127126
92115.131.45.128/25115.131.45.129 to 115.131.45.254115.131.45.255126
93115.131.46.0/25115.131.46.1 to 115.131.46.126115.131.46.127126
94115.131.46.128/25115.131.46.129 to 115.131.46.254115.131.46.255126
95115.131.47.0/25115.131.47.1 to 115.131.47.126115.131.47.127126
96115.131.47.128/25115.131.47.129 to 115.131.47.254115.131.47.255126
97115.131.48.0/25115.131.48.1 to 115.131.48.126115.131.48.127126
98115.131.48.128/25115.131.48.129 to 115.131.48.254115.131.48.255126
99115.131.49.0/25115.131.49.1 to 115.131.49.126115.131.49.127126
100115.131.49.128/25115.131.49.129 to 115.131.49.254115.131.49.255126
101115.131.50.0/25115.131.50.1 to 115.131.50.126115.131.50.127126
102115.131.50.128/25115.131.50.129 to 115.131.50.254115.131.50.255126
103115.131.51.0/25115.131.51.1 to 115.131.51.126115.131.51.127126
104115.131.51.128/25115.131.51.129 to 115.131.51.254115.131.51.255126
105115.131.52.0/25115.131.52.1 to 115.131.52.126115.131.52.127126
106115.131.52.128/25115.131.52.129 to 115.131.52.254115.131.52.255126
107115.131.53.0/25115.131.53.1 to 115.131.53.126115.131.53.127126
108115.131.53.128/25115.131.53.129 to 115.131.53.254115.131.53.255126
109115.131.54.0/25115.131.54.1 to 115.131.54.126115.131.54.127126
110115.131.54.128/25115.131.54.129 to 115.131.54.254115.131.54.255126
111115.131.55.0/25115.131.55.1 to 115.131.55.126115.131.55.127126
112115.131.55.128/25115.131.55.129 to 115.131.55.254115.131.55.255126
113115.131.56.0/25115.131.56.1 to 115.131.56.126115.131.56.127126
114115.131.56.128/25115.131.56.129 to 115.131.56.254115.131.56.255126
115115.131.57.0/25115.131.57.1 to 115.131.57.126115.131.57.127126
116115.131.57.128/25115.131.57.129 to 115.131.57.254115.131.57.255126
117115.131.58.0/25115.131.58.1 to 115.131.58.126115.131.58.127126
118115.131.58.128/25115.131.58.129 to 115.131.58.254115.131.58.255126
119115.131.59.0/25115.131.59.1 to 115.131.59.126115.131.59.127126
120115.131.59.128/25115.131.59.129 to 115.131.59.254115.131.59.255126
121115.131.60.0/25115.131.60.1 to 115.131.60.126115.131.60.127126
122115.131.60.128/25115.131.60.129 to 115.131.60.254115.131.60.255126
123115.131.61.0/25115.131.61.1 to 115.131.61.126115.131.61.127126
124115.131.61.128/25115.131.61.129 to 115.131.61.254115.131.61.255126
125115.131.62.0/25115.131.62.1 to 115.131.62.126115.131.62.127126
126115.131.62.128/25115.131.62.129 to 115.131.62.254115.131.62.255126
127115.131.63.0/25115.131.63.1 to 115.131.63.126115.131.63.127126
128115.131.63.128/25115.131.63.129 to 115.131.63.254115.131.63.255126
129115.131.64.0/25115.131.64.1 to 115.131.64.126115.131.64.127126
130115.131.64.128/25115.131.64.129 to 115.131.64.254115.131.64.255126
131115.131.65.0/25115.131.65.1 to 115.131.65.126115.131.65.127126
132115.131.65.128/25115.131.65.129 to 115.131.65.254115.131.65.255126
133115.131.66.0/25115.131.66.1 to 115.131.66.126115.131.66.127126
134115.131.66.128/25115.131.66.129 to 115.131.66.254115.131.66.255126
135115.131.67.0/25115.131.67.1 to 115.131.67.126115.131.67.127126
136115.131.67.128/25115.131.67.129 to 115.131.67.254115.131.67.255126
137115.131.68.0/25115.131.68.1 to 115.131.68.126115.131.68.127126
138115.131.68.128/25115.131.68.129 to 115.131.68.254115.131.68.255126
139115.131.69.0/25115.131.69.1 to 115.131.69.126115.131.69.127126
140115.131.69.128/25115.131.69.129 to 115.131.69.254115.131.69.255126
141115.131.70.0/25115.131.70.1 to 115.131.70.126115.131.70.127126
142115.131.70.128/25115.131.70.129 to 115.131.70.254115.131.70.255126
143115.131.71.0/25115.131.71.1 to 115.131.71.126115.131.71.127126
144115.131.71.128/25115.131.71.129 to 115.131.71.254115.131.71.255126
145115.131.72.0/25115.131.72.1 to 115.131.72.126115.131.72.127126
146115.131.72.128/25115.131.72.129 to 115.131.72.254115.131.72.255126
147115.131.73.0/25115.131.73.1 to 115.131.73.126115.131.73.127126
148115.131.73.128/25115.131.73.129 to 115.131.73.254115.131.73.255126
149115.131.74.0/25115.131.74.1 to 115.131.74.126115.131.74.127126
150115.131.74.128/25115.131.74.129 to 115.131.74.254115.131.74.255126
151115.131.75.0/25115.131.75.1 to 115.131.75.126115.131.75.127126
152115.131.75.128/25115.131.75.129 to 115.131.75.254115.131.75.255126
153115.131.76.0/25115.131.76.1 to 115.131.76.126115.131.76.127126
154115.131.76.128/25115.131.76.129 to 115.131.76.254115.131.76.255126
155115.131.77.0/25115.131.77.1 to 115.131.77.126115.131.77.127126
156115.131.77.128/25115.131.77.129 to 115.131.77.254115.131.77.255126
157115.131.78.0/25115.131.78.1 to 115.131.78.126115.131.78.127126
158115.131.78.128/25115.131.78.129 to 115.131.78.254115.131.78.255126
159115.131.79.0/25115.131.79.1 to 115.131.79.126115.131.79.127126
160115.131.79.128/25115.131.79.129 to 115.131.79.254115.131.79.255126
161115.131.80.0/25115.131.80.1 to 115.131.80.126115.131.80.127126
162115.131.80.128/25115.131.80.129 to 115.131.80.254115.131.80.255126
163115.131.81.0/25115.131.81.1 to 115.131.81.126115.131.81.127126
164115.131.81.128/25115.131.81.129 to 115.131.81.254115.131.81.255126
165115.131.82.0/25115.131.82.1 to 115.131.82.126115.131.82.127126
166115.131.82.128/25115.131.82.129 to 115.131.82.254115.131.82.255126
167115.131.83.0/25115.131.83.1 to 115.131.83.126115.131.83.127126
168115.131.83.128/25115.131.83.129 to 115.131.83.254115.131.83.255126
169115.131.84.0/25115.131.84.1 to 115.131.84.126115.131.84.127126
170115.131.84.128/25115.131.84.129 to 115.131.84.254115.131.84.255126
171115.131.85.0/25115.131.85.1 to 115.131.85.126115.131.85.127126
172115.131.85.128/25115.131.85.129 to 115.131.85.254115.131.85.255126
173115.131.86.0/25115.131.86.1 to 115.131.86.126115.131.86.127126
174115.131.86.128/25115.131.86.129 to 115.131.86.254115.131.86.255126
175115.131.87.0/25115.131.87.1 to 115.131.87.126115.131.87.127126
176115.131.87.128/25115.131.87.129 to 115.131.87.254115.131.87.255126
177115.131.88.0/25115.131.88.1 to 115.131.88.126115.131.88.127126
178115.131.88.128/25115.131.88.129 to 115.131.88.254115.131.88.255126
179115.131.89.0/25115.131.89.1 to 115.131.89.126115.131.89.127126
180115.131.89.128/25115.131.89.129 to 115.131.89.254115.131.89.255126
181115.131.90.0/25115.131.90.1 to 115.131.90.126115.131.90.127126
182115.131.90.128/25115.131.90.129 to 115.131.90.254115.131.90.255126
183115.131.91.0/25115.131.91.1 to 115.131.91.126115.131.91.127126
184115.131.91.128/25115.131.91.129 to 115.131.91.254115.131.91.255126
185115.131.92.0/25115.131.92.1 to 115.131.92.126115.131.92.127126
186115.131.92.128/25115.131.92.129 to 115.131.92.254115.131.92.255126
187115.131.93.0/25115.131.93.1 to 115.131.93.126115.131.93.127126
188115.131.93.128/25115.131.93.129 to 115.131.93.254115.131.93.255126
189115.131.94.0/25115.131.94.1 to 115.131.94.126115.131.94.127126
190115.131.94.128/25115.131.94.129 to 115.131.94.254115.131.94.255126
191115.131.95.0/25115.131.95.1 to 115.131.95.126115.131.95.127126
192115.131.95.128/25115.131.95.129 to 115.131.95.254115.131.95.255126
193115.131.96.0/25115.131.96.1 to 115.131.96.126115.131.96.127126
194115.131.96.128/25115.131.96.129 to 115.131.96.254115.131.96.255126
195115.131.97.0/25115.131.97.1 to 115.131.97.126115.131.97.127126
196115.131.97.128/25115.131.97.129 to 115.131.97.254115.131.97.255126
197115.131.98.0/25115.131.98.1 to 115.131.98.126115.131.98.127126
198115.131.98.128/25115.131.98.129 to 115.131.98.254115.131.98.255126
199115.131.99.0/25115.131.99.1 to 115.131.99.126115.131.99.127126
200115.131.99.128/25115.131.99.129 to 115.131.99.254115.131.99.255126
201115.131.100.0/25115.131.100.1 to 115.131.100.126115.131.100.127126
202115.131.100.128/25115.131.100.129 to 115.131.100.254115.131.100.255126
203115.131.101.0/25115.131.101.1 to 115.131.101.126115.131.101.127126
204115.131.101.128/25115.131.101.129 to 115.131.101.254115.131.101.255126
205115.131.102.0/25115.131.102.1 to 115.131.102.126115.131.102.127126
206115.131.102.128/25115.131.102.129 to 115.131.102.254115.131.102.255126
207115.131.103.0/25115.131.103.1 to 115.131.103.126115.131.103.127126
208115.131.103.128/25115.131.103.129 to 115.131.103.254115.131.103.255126
209115.131.104.0/25115.131.104.1 to 115.131.104.126115.131.104.127126
210115.131.104.128/25115.131.104.129 to 115.131.104.254115.131.104.255126
211115.131.105.0/25115.131.105.1 to 115.131.105.126115.131.105.127126
212115.131.105.128/25115.131.105.129 to 115.131.105.254115.131.105.255126
213115.131.106.0/25115.131.106.1 to 115.131.106.126115.131.106.127126
214115.131.106.128/25115.131.106.129 to 115.131.106.254115.131.106.255126
215115.131.107.0/25115.131.107.1 to 115.131.107.126115.131.107.127126
216115.131.107.128/25115.131.107.129 to 115.131.107.254115.131.107.255126
217115.131.108.0/25115.131.108.1 to 115.131.108.126115.131.108.127126
218115.131.108.128/25115.131.108.129 to 115.131.108.254115.131.108.255126
219115.131.109.0/25115.131.109.1 to 115.131.109.126115.131.109.127126
220115.131.109.128/25115.131.109.129 to 115.131.109.254115.131.109.255126
221115.131.110.0/25115.131.110.1 to 115.131.110.126115.131.110.127126
222115.131.110.128/25115.131.110.129 to 115.131.110.254115.131.110.255126
223115.131.111.0/25115.131.111.1 to 115.131.111.126115.131.111.127126
224115.131.111.128/25115.131.111.129 to 115.131.111.254115.131.111.255126
225115.131.112.0/25115.131.112.1 to 115.131.112.126115.131.112.127126
226115.131.112.128/25115.131.112.129 to 115.131.112.254115.131.112.255126
227115.131.113.0/25115.131.113.1 to 115.131.113.126115.131.113.127126
228115.131.113.128/25115.131.113.129 to 115.131.113.254115.131.113.255126
229115.131.114.0/25115.131.114.1 to 115.131.114.126115.131.114.127126
230115.131.114.128/25115.131.114.129 to 115.131.114.254115.131.114.255126
231115.131.115.0/25115.131.115.1 to 115.131.115.126115.131.115.127126
232115.131.115.128/25115.131.115.129 to 115.131.115.254115.131.115.255126
233115.131.116.0/25115.131.116.1 to 115.131.116.126115.131.116.127126
234115.131.116.128/25115.131.116.129 to 115.131.116.254115.131.116.255126
235115.131.117.0/25115.131.117.1 to 115.131.117.126115.131.117.127126
236115.131.117.128/25115.131.117.129 to 115.131.117.254115.131.117.255126
237115.131.118.0/25115.131.118.1 to 115.131.118.126115.131.118.127126
238115.131.118.128/25115.131.118.129 to 115.131.118.254115.131.118.255126
239115.131.119.0/25115.131.119.1 to 115.131.119.126115.131.119.127126
240115.131.119.128/25115.131.119.129 to 115.131.119.254115.131.119.255126
241115.131.120.0/25115.131.120.1 to 115.131.120.126115.131.120.127126
242115.131.120.128/25115.131.120.129 to 115.131.120.254115.131.120.255126
243115.131.121.0/25115.131.121.1 to 115.131.121.126115.131.121.127126
244115.131.121.128/25115.131.121.129 to 115.131.121.254115.131.121.255126
245115.131.122.0/25115.131.122.1 to 115.131.122.126115.131.122.127126
246115.131.122.128/25115.131.122.129 to 115.131.122.254115.131.122.255126
247115.131.123.0/25115.131.123.1 to 115.131.123.126115.131.123.127126
248115.131.123.128/25115.131.123.129 to 115.131.123.254115.131.123.255126
249115.131.124.0/25115.131.124.1 to 115.131.124.126115.131.124.127126
250115.131.124.128/25115.131.124.129 to 115.131.124.254115.131.124.255126
251115.131.125.0/25115.131.125.1 to 115.131.125.126115.131.125.127126
252115.131.125.128/25115.131.125.129 to 115.131.125.254115.131.125.255126
253115.131.126.0/25115.131.126.1 to 115.131.126.126115.131.126.127126
254115.131.126.128/25115.131.126.129 to 115.131.126.254115.131.126.255126
255115.131.127.0/25115.131.127.1 to 115.131.127.126115.131.127.127126
256115.131.127.128/25115.131.127.129 to 115.131.127.254115.131.127.255126

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.