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.

Network248.2.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
248.2.0.0
Broadcast address
248.3.255.255
First usable
248.2.0.1
Last usable
248.3.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F8020000 · Integer 4160880640 to 4161011711
Reverse DNS zones
2.248.in-addr.arpa
3.248.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11111000.00000010.00000000.00000000248.2.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network11111000.00000010.00000000.00000000248.2.0.0
Broadcast11111000.00000011.11111111.11111111248.3.255.255
Split into smaller subnets/25
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

248.2.0.0/15 makes 1,024 subnets of /25; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1248.2.0.0/25248.2.0.1 to 248.2.0.126248.2.0.127126
2248.2.0.128/25248.2.0.129 to 248.2.0.254248.2.0.255126
3248.2.1.0/25248.2.1.1 to 248.2.1.126248.2.1.127126
4248.2.1.128/25248.2.1.129 to 248.2.1.254248.2.1.255126
5248.2.2.0/25248.2.2.1 to 248.2.2.126248.2.2.127126
6248.2.2.128/25248.2.2.129 to 248.2.2.254248.2.2.255126
7248.2.3.0/25248.2.3.1 to 248.2.3.126248.2.3.127126
8248.2.3.128/25248.2.3.129 to 248.2.3.254248.2.3.255126
9248.2.4.0/25248.2.4.1 to 248.2.4.126248.2.4.127126
10248.2.4.128/25248.2.4.129 to 248.2.4.254248.2.4.255126
11248.2.5.0/25248.2.5.1 to 248.2.5.126248.2.5.127126
12248.2.5.128/25248.2.5.129 to 248.2.5.254248.2.5.255126
13248.2.6.0/25248.2.6.1 to 248.2.6.126248.2.6.127126
14248.2.6.128/25248.2.6.129 to 248.2.6.254248.2.6.255126
15248.2.7.0/25248.2.7.1 to 248.2.7.126248.2.7.127126
16248.2.7.128/25248.2.7.129 to 248.2.7.254248.2.7.255126
17248.2.8.0/25248.2.8.1 to 248.2.8.126248.2.8.127126
18248.2.8.128/25248.2.8.129 to 248.2.8.254248.2.8.255126
19248.2.9.0/25248.2.9.1 to 248.2.9.126248.2.9.127126
20248.2.9.128/25248.2.9.129 to 248.2.9.254248.2.9.255126
21248.2.10.0/25248.2.10.1 to 248.2.10.126248.2.10.127126
22248.2.10.128/25248.2.10.129 to 248.2.10.254248.2.10.255126
23248.2.11.0/25248.2.11.1 to 248.2.11.126248.2.11.127126
24248.2.11.128/25248.2.11.129 to 248.2.11.254248.2.11.255126
25248.2.12.0/25248.2.12.1 to 248.2.12.126248.2.12.127126
26248.2.12.128/25248.2.12.129 to 248.2.12.254248.2.12.255126
27248.2.13.0/25248.2.13.1 to 248.2.13.126248.2.13.127126
28248.2.13.128/25248.2.13.129 to 248.2.13.254248.2.13.255126
29248.2.14.0/25248.2.14.1 to 248.2.14.126248.2.14.127126
30248.2.14.128/25248.2.14.129 to 248.2.14.254248.2.14.255126
31248.2.15.0/25248.2.15.1 to 248.2.15.126248.2.15.127126
32248.2.15.128/25248.2.15.129 to 248.2.15.254248.2.15.255126
33248.2.16.0/25248.2.16.1 to 248.2.16.126248.2.16.127126
34248.2.16.128/25248.2.16.129 to 248.2.16.254248.2.16.255126
35248.2.17.0/25248.2.17.1 to 248.2.17.126248.2.17.127126
36248.2.17.128/25248.2.17.129 to 248.2.17.254248.2.17.255126
37248.2.18.0/25248.2.18.1 to 248.2.18.126248.2.18.127126
38248.2.18.128/25248.2.18.129 to 248.2.18.254248.2.18.255126
39248.2.19.0/25248.2.19.1 to 248.2.19.126248.2.19.127126
40248.2.19.128/25248.2.19.129 to 248.2.19.254248.2.19.255126
41248.2.20.0/25248.2.20.1 to 248.2.20.126248.2.20.127126
42248.2.20.128/25248.2.20.129 to 248.2.20.254248.2.20.255126
43248.2.21.0/25248.2.21.1 to 248.2.21.126248.2.21.127126
44248.2.21.128/25248.2.21.129 to 248.2.21.254248.2.21.255126
45248.2.22.0/25248.2.22.1 to 248.2.22.126248.2.22.127126
46248.2.22.128/25248.2.22.129 to 248.2.22.254248.2.22.255126
47248.2.23.0/25248.2.23.1 to 248.2.23.126248.2.23.127126
48248.2.23.128/25248.2.23.129 to 248.2.23.254248.2.23.255126
49248.2.24.0/25248.2.24.1 to 248.2.24.126248.2.24.127126
50248.2.24.128/25248.2.24.129 to 248.2.24.254248.2.24.255126
51248.2.25.0/25248.2.25.1 to 248.2.25.126248.2.25.127126
52248.2.25.128/25248.2.25.129 to 248.2.25.254248.2.25.255126
53248.2.26.0/25248.2.26.1 to 248.2.26.126248.2.26.127126
54248.2.26.128/25248.2.26.129 to 248.2.26.254248.2.26.255126
55248.2.27.0/25248.2.27.1 to 248.2.27.126248.2.27.127126
56248.2.27.128/25248.2.27.129 to 248.2.27.254248.2.27.255126
57248.2.28.0/25248.2.28.1 to 248.2.28.126248.2.28.127126
58248.2.28.128/25248.2.28.129 to 248.2.28.254248.2.28.255126
59248.2.29.0/25248.2.29.1 to 248.2.29.126248.2.29.127126
60248.2.29.128/25248.2.29.129 to 248.2.29.254248.2.29.255126
61248.2.30.0/25248.2.30.1 to 248.2.30.126248.2.30.127126
62248.2.30.128/25248.2.30.129 to 248.2.30.254248.2.30.255126
63248.2.31.0/25248.2.31.1 to 248.2.31.126248.2.31.127126
64248.2.31.128/25248.2.31.129 to 248.2.31.254248.2.31.255126
65248.2.32.0/25248.2.32.1 to 248.2.32.126248.2.32.127126
66248.2.32.128/25248.2.32.129 to 248.2.32.254248.2.32.255126
67248.2.33.0/25248.2.33.1 to 248.2.33.126248.2.33.127126
68248.2.33.128/25248.2.33.129 to 248.2.33.254248.2.33.255126
69248.2.34.0/25248.2.34.1 to 248.2.34.126248.2.34.127126
70248.2.34.128/25248.2.34.129 to 248.2.34.254248.2.34.255126
71248.2.35.0/25248.2.35.1 to 248.2.35.126248.2.35.127126
72248.2.35.128/25248.2.35.129 to 248.2.35.254248.2.35.255126
73248.2.36.0/25248.2.36.1 to 248.2.36.126248.2.36.127126
74248.2.36.128/25248.2.36.129 to 248.2.36.254248.2.36.255126
75248.2.37.0/25248.2.37.1 to 248.2.37.126248.2.37.127126
76248.2.37.128/25248.2.37.129 to 248.2.37.254248.2.37.255126
77248.2.38.0/25248.2.38.1 to 248.2.38.126248.2.38.127126
78248.2.38.128/25248.2.38.129 to 248.2.38.254248.2.38.255126
79248.2.39.0/25248.2.39.1 to 248.2.39.126248.2.39.127126
80248.2.39.128/25248.2.39.129 to 248.2.39.254248.2.39.255126
81248.2.40.0/25248.2.40.1 to 248.2.40.126248.2.40.127126
82248.2.40.128/25248.2.40.129 to 248.2.40.254248.2.40.255126
83248.2.41.0/25248.2.41.1 to 248.2.41.126248.2.41.127126
84248.2.41.128/25248.2.41.129 to 248.2.41.254248.2.41.255126
85248.2.42.0/25248.2.42.1 to 248.2.42.126248.2.42.127126
86248.2.42.128/25248.2.42.129 to 248.2.42.254248.2.42.255126
87248.2.43.0/25248.2.43.1 to 248.2.43.126248.2.43.127126
88248.2.43.128/25248.2.43.129 to 248.2.43.254248.2.43.255126
89248.2.44.0/25248.2.44.1 to 248.2.44.126248.2.44.127126
90248.2.44.128/25248.2.44.129 to 248.2.44.254248.2.44.255126
91248.2.45.0/25248.2.45.1 to 248.2.45.126248.2.45.127126
92248.2.45.128/25248.2.45.129 to 248.2.45.254248.2.45.255126
93248.2.46.0/25248.2.46.1 to 248.2.46.126248.2.46.127126
94248.2.46.128/25248.2.46.129 to 248.2.46.254248.2.46.255126
95248.2.47.0/25248.2.47.1 to 248.2.47.126248.2.47.127126
96248.2.47.128/25248.2.47.129 to 248.2.47.254248.2.47.255126
97248.2.48.0/25248.2.48.1 to 248.2.48.126248.2.48.127126
98248.2.48.128/25248.2.48.129 to 248.2.48.254248.2.48.255126
99248.2.49.0/25248.2.49.1 to 248.2.49.126248.2.49.127126
100248.2.49.128/25248.2.49.129 to 248.2.49.254248.2.49.255126
101248.2.50.0/25248.2.50.1 to 248.2.50.126248.2.50.127126
102248.2.50.128/25248.2.50.129 to 248.2.50.254248.2.50.255126
103248.2.51.0/25248.2.51.1 to 248.2.51.126248.2.51.127126
104248.2.51.128/25248.2.51.129 to 248.2.51.254248.2.51.255126
105248.2.52.0/25248.2.52.1 to 248.2.52.126248.2.52.127126
106248.2.52.128/25248.2.52.129 to 248.2.52.254248.2.52.255126
107248.2.53.0/25248.2.53.1 to 248.2.53.126248.2.53.127126
108248.2.53.128/25248.2.53.129 to 248.2.53.254248.2.53.255126
109248.2.54.0/25248.2.54.1 to 248.2.54.126248.2.54.127126
110248.2.54.128/25248.2.54.129 to 248.2.54.254248.2.54.255126
111248.2.55.0/25248.2.55.1 to 248.2.55.126248.2.55.127126
112248.2.55.128/25248.2.55.129 to 248.2.55.254248.2.55.255126
113248.2.56.0/25248.2.56.1 to 248.2.56.126248.2.56.127126
114248.2.56.128/25248.2.56.129 to 248.2.56.254248.2.56.255126
115248.2.57.0/25248.2.57.1 to 248.2.57.126248.2.57.127126
116248.2.57.128/25248.2.57.129 to 248.2.57.254248.2.57.255126
117248.2.58.0/25248.2.58.1 to 248.2.58.126248.2.58.127126
118248.2.58.128/25248.2.58.129 to 248.2.58.254248.2.58.255126
119248.2.59.0/25248.2.59.1 to 248.2.59.126248.2.59.127126
120248.2.59.128/25248.2.59.129 to 248.2.59.254248.2.59.255126
121248.2.60.0/25248.2.60.1 to 248.2.60.126248.2.60.127126
122248.2.60.128/25248.2.60.129 to 248.2.60.254248.2.60.255126
123248.2.61.0/25248.2.61.1 to 248.2.61.126248.2.61.127126
124248.2.61.128/25248.2.61.129 to 248.2.61.254248.2.61.255126
125248.2.62.0/25248.2.62.1 to 248.2.62.126248.2.62.127126
126248.2.62.128/25248.2.62.129 to 248.2.62.254248.2.62.255126
127248.2.63.0/25248.2.63.1 to 248.2.63.126248.2.63.127126
128248.2.63.128/25248.2.63.129 to 248.2.63.254248.2.63.255126
129248.2.64.0/25248.2.64.1 to 248.2.64.126248.2.64.127126
130248.2.64.128/25248.2.64.129 to 248.2.64.254248.2.64.255126
131248.2.65.0/25248.2.65.1 to 248.2.65.126248.2.65.127126
132248.2.65.128/25248.2.65.129 to 248.2.65.254248.2.65.255126
133248.2.66.0/25248.2.66.1 to 248.2.66.126248.2.66.127126
134248.2.66.128/25248.2.66.129 to 248.2.66.254248.2.66.255126
135248.2.67.0/25248.2.67.1 to 248.2.67.126248.2.67.127126
136248.2.67.128/25248.2.67.129 to 248.2.67.254248.2.67.255126
137248.2.68.0/25248.2.68.1 to 248.2.68.126248.2.68.127126
138248.2.68.128/25248.2.68.129 to 248.2.68.254248.2.68.255126
139248.2.69.0/25248.2.69.1 to 248.2.69.126248.2.69.127126
140248.2.69.128/25248.2.69.129 to 248.2.69.254248.2.69.255126
141248.2.70.0/25248.2.70.1 to 248.2.70.126248.2.70.127126
142248.2.70.128/25248.2.70.129 to 248.2.70.254248.2.70.255126
143248.2.71.0/25248.2.71.1 to 248.2.71.126248.2.71.127126
144248.2.71.128/25248.2.71.129 to 248.2.71.254248.2.71.255126
145248.2.72.0/25248.2.72.1 to 248.2.72.126248.2.72.127126
146248.2.72.128/25248.2.72.129 to 248.2.72.254248.2.72.255126
147248.2.73.0/25248.2.73.1 to 248.2.73.126248.2.73.127126
148248.2.73.128/25248.2.73.129 to 248.2.73.254248.2.73.255126
149248.2.74.0/25248.2.74.1 to 248.2.74.126248.2.74.127126
150248.2.74.128/25248.2.74.129 to 248.2.74.254248.2.74.255126
151248.2.75.0/25248.2.75.1 to 248.2.75.126248.2.75.127126
152248.2.75.128/25248.2.75.129 to 248.2.75.254248.2.75.255126
153248.2.76.0/25248.2.76.1 to 248.2.76.126248.2.76.127126
154248.2.76.128/25248.2.76.129 to 248.2.76.254248.2.76.255126
155248.2.77.0/25248.2.77.1 to 248.2.77.126248.2.77.127126
156248.2.77.128/25248.2.77.129 to 248.2.77.254248.2.77.255126
157248.2.78.0/25248.2.78.1 to 248.2.78.126248.2.78.127126
158248.2.78.128/25248.2.78.129 to 248.2.78.254248.2.78.255126
159248.2.79.0/25248.2.79.1 to 248.2.79.126248.2.79.127126
160248.2.79.128/25248.2.79.129 to 248.2.79.254248.2.79.255126
161248.2.80.0/25248.2.80.1 to 248.2.80.126248.2.80.127126
162248.2.80.128/25248.2.80.129 to 248.2.80.254248.2.80.255126
163248.2.81.0/25248.2.81.1 to 248.2.81.126248.2.81.127126
164248.2.81.128/25248.2.81.129 to 248.2.81.254248.2.81.255126
165248.2.82.0/25248.2.82.1 to 248.2.82.126248.2.82.127126
166248.2.82.128/25248.2.82.129 to 248.2.82.254248.2.82.255126
167248.2.83.0/25248.2.83.1 to 248.2.83.126248.2.83.127126
168248.2.83.128/25248.2.83.129 to 248.2.83.254248.2.83.255126
169248.2.84.0/25248.2.84.1 to 248.2.84.126248.2.84.127126
170248.2.84.128/25248.2.84.129 to 248.2.84.254248.2.84.255126
171248.2.85.0/25248.2.85.1 to 248.2.85.126248.2.85.127126
172248.2.85.128/25248.2.85.129 to 248.2.85.254248.2.85.255126
173248.2.86.0/25248.2.86.1 to 248.2.86.126248.2.86.127126
174248.2.86.128/25248.2.86.129 to 248.2.86.254248.2.86.255126
175248.2.87.0/25248.2.87.1 to 248.2.87.126248.2.87.127126
176248.2.87.128/25248.2.87.129 to 248.2.87.254248.2.87.255126
177248.2.88.0/25248.2.88.1 to 248.2.88.126248.2.88.127126
178248.2.88.128/25248.2.88.129 to 248.2.88.254248.2.88.255126
179248.2.89.0/25248.2.89.1 to 248.2.89.126248.2.89.127126
180248.2.89.128/25248.2.89.129 to 248.2.89.254248.2.89.255126
181248.2.90.0/25248.2.90.1 to 248.2.90.126248.2.90.127126
182248.2.90.128/25248.2.90.129 to 248.2.90.254248.2.90.255126
183248.2.91.0/25248.2.91.1 to 248.2.91.126248.2.91.127126
184248.2.91.128/25248.2.91.129 to 248.2.91.254248.2.91.255126
185248.2.92.0/25248.2.92.1 to 248.2.92.126248.2.92.127126
186248.2.92.128/25248.2.92.129 to 248.2.92.254248.2.92.255126
187248.2.93.0/25248.2.93.1 to 248.2.93.126248.2.93.127126
188248.2.93.128/25248.2.93.129 to 248.2.93.254248.2.93.255126
189248.2.94.0/25248.2.94.1 to 248.2.94.126248.2.94.127126
190248.2.94.128/25248.2.94.129 to 248.2.94.254248.2.94.255126
191248.2.95.0/25248.2.95.1 to 248.2.95.126248.2.95.127126
192248.2.95.128/25248.2.95.129 to 248.2.95.254248.2.95.255126
193248.2.96.0/25248.2.96.1 to 248.2.96.126248.2.96.127126
194248.2.96.128/25248.2.96.129 to 248.2.96.254248.2.96.255126
195248.2.97.0/25248.2.97.1 to 248.2.97.126248.2.97.127126
196248.2.97.128/25248.2.97.129 to 248.2.97.254248.2.97.255126
197248.2.98.0/25248.2.98.1 to 248.2.98.126248.2.98.127126
198248.2.98.128/25248.2.98.129 to 248.2.98.254248.2.98.255126
199248.2.99.0/25248.2.99.1 to 248.2.99.126248.2.99.127126
200248.2.99.128/25248.2.99.129 to 248.2.99.254248.2.99.255126
201248.2.100.0/25248.2.100.1 to 248.2.100.126248.2.100.127126
202248.2.100.128/25248.2.100.129 to 248.2.100.254248.2.100.255126
203248.2.101.0/25248.2.101.1 to 248.2.101.126248.2.101.127126
204248.2.101.128/25248.2.101.129 to 248.2.101.254248.2.101.255126
205248.2.102.0/25248.2.102.1 to 248.2.102.126248.2.102.127126
206248.2.102.128/25248.2.102.129 to 248.2.102.254248.2.102.255126
207248.2.103.0/25248.2.103.1 to 248.2.103.126248.2.103.127126
208248.2.103.128/25248.2.103.129 to 248.2.103.254248.2.103.255126
209248.2.104.0/25248.2.104.1 to 248.2.104.126248.2.104.127126
210248.2.104.128/25248.2.104.129 to 248.2.104.254248.2.104.255126
211248.2.105.0/25248.2.105.1 to 248.2.105.126248.2.105.127126
212248.2.105.128/25248.2.105.129 to 248.2.105.254248.2.105.255126
213248.2.106.0/25248.2.106.1 to 248.2.106.126248.2.106.127126
214248.2.106.128/25248.2.106.129 to 248.2.106.254248.2.106.255126
215248.2.107.0/25248.2.107.1 to 248.2.107.126248.2.107.127126
216248.2.107.128/25248.2.107.129 to 248.2.107.254248.2.107.255126
217248.2.108.0/25248.2.108.1 to 248.2.108.126248.2.108.127126
218248.2.108.128/25248.2.108.129 to 248.2.108.254248.2.108.255126
219248.2.109.0/25248.2.109.1 to 248.2.109.126248.2.109.127126
220248.2.109.128/25248.2.109.129 to 248.2.109.254248.2.109.255126
221248.2.110.0/25248.2.110.1 to 248.2.110.126248.2.110.127126
222248.2.110.128/25248.2.110.129 to 248.2.110.254248.2.110.255126
223248.2.111.0/25248.2.111.1 to 248.2.111.126248.2.111.127126
224248.2.111.128/25248.2.111.129 to 248.2.111.254248.2.111.255126
225248.2.112.0/25248.2.112.1 to 248.2.112.126248.2.112.127126
226248.2.112.128/25248.2.112.129 to 248.2.112.254248.2.112.255126
227248.2.113.0/25248.2.113.1 to 248.2.113.126248.2.113.127126
228248.2.113.128/25248.2.113.129 to 248.2.113.254248.2.113.255126
229248.2.114.0/25248.2.114.1 to 248.2.114.126248.2.114.127126
230248.2.114.128/25248.2.114.129 to 248.2.114.254248.2.114.255126
231248.2.115.0/25248.2.115.1 to 248.2.115.126248.2.115.127126
232248.2.115.128/25248.2.115.129 to 248.2.115.254248.2.115.255126
233248.2.116.0/25248.2.116.1 to 248.2.116.126248.2.116.127126
234248.2.116.128/25248.2.116.129 to 248.2.116.254248.2.116.255126
235248.2.117.0/25248.2.117.1 to 248.2.117.126248.2.117.127126
236248.2.117.128/25248.2.117.129 to 248.2.117.254248.2.117.255126
237248.2.118.0/25248.2.118.1 to 248.2.118.126248.2.118.127126
238248.2.118.128/25248.2.118.129 to 248.2.118.254248.2.118.255126
239248.2.119.0/25248.2.119.1 to 248.2.119.126248.2.119.127126
240248.2.119.128/25248.2.119.129 to 248.2.119.254248.2.119.255126
241248.2.120.0/25248.2.120.1 to 248.2.120.126248.2.120.127126
242248.2.120.128/25248.2.120.129 to 248.2.120.254248.2.120.255126
243248.2.121.0/25248.2.121.1 to 248.2.121.126248.2.121.127126
244248.2.121.128/25248.2.121.129 to 248.2.121.254248.2.121.255126
245248.2.122.0/25248.2.122.1 to 248.2.122.126248.2.122.127126
246248.2.122.128/25248.2.122.129 to 248.2.122.254248.2.122.255126
247248.2.123.0/25248.2.123.1 to 248.2.123.126248.2.123.127126
248248.2.123.128/25248.2.123.129 to 248.2.123.254248.2.123.255126
249248.2.124.0/25248.2.124.1 to 248.2.124.126248.2.124.127126
250248.2.124.128/25248.2.124.129 to 248.2.124.254248.2.124.255126
251248.2.125.0/25248.2.125.1 to 248.2.125.126248.2.125.127126
252248.2.125.128/25248.2.125.129 to 248.2.125.254248.2.125.255126
253248.2.126.0/25248.2.126.1 to 248.2.126.126248.2.126.127126
254248.2.126.128/25248.2.126.129 to 248.2.126.254248.2.126.255126
255248.2.127.0/25248.2.127.1 to 248.2.127.126248.2.127.127126
256248.2.127.128/25248.2.127.129 to 248.2.127.254248.2.127.255126

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.