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.

Network202.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
202.0.0.0
Broadcast address
203.255.255.255
First usable
202.0.0.1
Last usable
203.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
C (default /24)
As numbers
Hex CA000000 · Integer 3388997632 to 3422552063
Reverse DNS zones
202.in-addr.arpa
203.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11001010.00000000.00000000.00000000202.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network11001010.00000000.00000000.00000000202.0.0.0
Broadcast11001011.11111111.11111111.11111111203.255.255.255
Split into smaller subnets/17
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

202.0.0.0/7 makes 1,024 subnets of /17; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1202.0.0.0/17202.0.0.1 to 202.0.127.254202.0.127.25532,766
2202.0.128.0/17202.0.128.1 to 202.0.255.254202.0.255.25532,766
3202.1.0.0/17202.1.0.1 to 202.1.127.254202.1.127.25532,766
4202.1.128.0/17202.1.128.1 to 202.1.255.254202.1.255.25532,766
5202.2.0.0/17202.2.0.1 to 202.2.127.254202.2.127.25532,766
6202.2.128.0/17202.2.128.1 to 202.2.255.254202.2.255.25532,766
7202.3.0.0/17202.3.0.1 to 202.3.127.254202.3.127.25532,766
8202.3.128.0/17202.3.128.1 to 202.3.255.254202.3.255.25532,766
9202.4.0.0/17202.4.0.1 to 202.4.127.254202.4.127.25532,766
10202.4.128.0/17202.4.128.1 to 202.4.255.254202.4.255.25532,766
11202.5.0.0/17202.5.0.1 to 202.5.127.254202.5.127.25532,766
12202.5.128.0/17202.5.128.1 to 202.5.255.254202.5.255.25532,766
13202.6.0.0/17202.6.0.1 to 202.6.127.254202.6.127.25532,766
14202.6.128.0/17202.6.128.1 to 202.6.255.254202.6.255.25532,766
15202.7.0.0/17202.7.0.1 to 202.7.127.254202.7.127.25532,766
16202.7.128.0/17202.7.128.1 to 202.7.255.254202.7.255.25532,766
17202.8.0.0/17202.8.0.1 to 202.8.127.254202.8.127.25532,766
18202.8.128.0/17202.8.128.1 to 202.8.255.254202.8.255.25532,766
19202.9.0.0/17202.9.0.1 to 202.9.127.254202.9.127.25532,766
20202.9.128.0/17202.9.128.1 to 202.9.255.254202.9.255.25532,766
21202.10.0.0/17202.10.0.1 to 202.10.127.254202.10.127.25532,766
22202.10.128.0/17202.10.128.1 to 202.10.255.254202.10.255.25532,766
23202.11.0.0/17202.11.0.1 to 202.11.127.254202.11.127.25532,766
24202.11.128.0/17202.11.128.1 to 202.11.255.254202.11.255.25532,766
25202.12.0.0/17202.12.0.1 to 202.12.127.254202.12.127.25532,766
26202.12.128.0/17202.12.128.1 to 202.12.255.254202.12.255.25532,766
27202.13.0.0/17202.13.0.1 to 202.13.127.254202.13.127.25532,766
28202.13.128.0/17202.13.128.1 to 202.13.255.254202.13.255.25532,766
29202.14.0.0/17202.14.0.1 to 202.14.127.254202.14.127.25532,766
30202.14.128.0/17202.14.128.1 to 202.14.255.254202.14.255.25532,766
31202.15.0.0/17202.15.0.1 to 202.15.127.254202.15.127.25532,766
32202.15.128.0/17202.15.128.1 to 202.15.255.254202.15.255.25532,766
33202.16.0.0/17202.16.0.1 to 202.16.127.254202.16.127.25532,766
34202.16.128.0/17202.16.128.1 to 202.16.255.254202.16.255.25532,766
35202.17.0.0/17202.17.0.1 to 202.17.127.254202.17.127.25532,766
36202.17.128.0/17202.17.128.1 to 202.17.255.254202.17.255.25532,766
37202.18.0.0/17202.18.0.1 to 202.18.127.254202.18.127.25532,766
38202.18.128.0/17202.18.128.1 to 202.18.255.254202.18.255.25532,766
39202.19.0.0/17202.19.0.1 to 202.19.127.254202.19.127.25532,766
40202.19.128.0/17202.19.128.1 to 202.19.255.254202.19.255.25532,766
41202.20.0.0/17202.20.0.1 to 202.20.127.254202.20.127.25532,766
42202.20.128.0/17202.20.128.1 to 202.20.255.254202.20.255.25532,766
43202.21.0.0/17202.21.0.1 to 202.21.127.254202.21.127.25532,766
44202.21.128.0/17202.21.128.1 to 202.21.255.254202.21.255.25532,766
45202.22.0.0/17202.22.0.1 to 202.22.127.254202.22.127.25532,766
46202.22.128.0/17202.22.128.1 to 202.22.255.254202.22.255.25532,766
47202.23.0.0/17202.23.0.1 to 202.23.127.254202.23.127.25532,766
48202.23.128.0/17202.23.128.1 to 202.23.255.254202.23.255.25532,766
49202.24.0.0/17202.24.0.1 to 202.24.127.254202.24.127.25532,766
50202.24.128.0/17202.24.128.1 to 202.24.255.254202.24.255.25532,766
51202.25.0.0/17202.25.0.1 to 202.25.127.254202.25.127.25532,766
52202.25.128.0/17202.25.128.1 to 202.25.255.254202.25.255.25532,766
53202.26.0.0/17202.26.0.1 to 202.26.127.254202.26.127.25532,766
54202.26.128.0/17202.26.128.1 to 202.26.255.254202.26.255.25532,766
55202.27.0.0/17202.27.0.1 to 202.27.127.254202.27.127.25532,766
56202.27.128.0/17202.27.128.1 to 202.27.255.254202.27.255.25532,766
57202.28.0.0/17202.28.0.1 to 202.28.127.254202.28.127.25532,766
58202.28.128.0/17202.28.128.1 to 202.28.255.254202.28.255.25532,766
59202.29.0.0/17202.29.0.1 to 202.29.127.254202.29.127.25532,766
60202.29.128.0/17202.29.128.1 to 202.29.255.254202.29.255.25532,766
61202.30.0.0/17202.30.0.1 to 202.30.127.254202.30.127.25532,766
62202.30.128.0/17202.30.128.1 to 202.30.255.254202.30.255.25532,766
63202.31.0.0/17202.31.0.1 to 202.31.127.254202.31.127.25532,766
64202.31.128.0/17202.31.128.1 to 202.31.255.254202.31.255.25532,766
65202.32.0.0/17202.32.0.1 to 202.32.127.254202.32.127.25532,766
66202.32.128.0/17202.32.128.1 to 202.32.255.254202.32.255.25532,766
67202.33.0.0/17202.33.0.1 to 202.33.127.254202.33.127.25532,766
68202.33.128.0/17202.33.128.1 to 202.33.255.254202.33.255.25532,766
69202.34.0.0/17202.34.0.1 to 202.34.127.254202.34.127.25532,766
70202.34.128.0/17202.34.128.1 to 202.34.255.254202.34.255.25532,766
71202.35.0.0/17202.35.0.1 to 202.35.127.254202.35.127.25532,766
72202.35.128.0/17202.35.128.1 to 202.35.255.254202.35.255.25532,766
73202.36.0.0/17202.36.0.1 to 202.36.127.254202.36.127.25532,766
74202.36.128.0/17202.36.128.1 to 202.36.255.254202.36.255.25532,766
75202.37.0.0/17202.37.0.1 to 202.37.127.254202.37.127.25532,766
76202.37.128.0/17202.37.128.1 to 202.37.255.254202.37.255.25532,766
77202.38.0.0/17202.38.0.1 to 202.38.127.254202.38.127.25532,766
78202.38.128.0/17202.38.128.1 to 202.38.255.254202.38.255.25532,766
79202.39.0.0/17202.39.0.1 to 202.39.127.254202.39.127.25532,766
80202.39.128.0/17202.39.128.1 to 202.39.255.254202.39.255.25532,766
81202.40.0.0/17202.40.0.1 to 202.40.127.254202.40.127.25532,766
82202.40.128.0/17202.40.128.1 to 202.40.255.254202.40.255.25532,766
83202.41.0.0/17202.41.0.1 to 202.41.127.254202.41.127.25532,766
84202.41.128.0/17202.41.128.1 to 202.41.255.254202.41.255.25532,766
85202.42.0.0/17202.42.0.1 to 202.42.127.254202.42.127.25532,766
86202.42.128.0/17202.42.128.1 to 202.42.255.254202.42.255.25532,766
87202.43.0.0/17202.43.0.1 to 202.43.127.254202.43.127.25532,766
88202.43.128.0/17202.43.128.1 to 202.43.255.254202.43.255.25532,766
89202.44.0.0/17202.44.0.1 to 202.44.127.254202.44.127.25532,766
90202.44.128.0/17202.44.128.1 to 202.44.255.254202.44.255.25532,766
91202.45.0.0/17202.45.0.1 to 202.45.127.254202.45.127.25532,766
92202.45.128.0/17202.45.128.1 to 202.45.255.254202.45.255.25532,766
93202.46.0.0/17202.46.0.1 to 202.46.127.254202.46.127.25532,766
94202.46.128.0/17202.46.128.1 to 202.46.255.254202.46.255.25532,766
95202.47.0.0/17202.47.0.1 to 202.47.127.254202.47.127.25532,766
96202.47.128.0/17202.47.128.1 to 202.47.255.254202.47.255.25532,766
97202.48.0.0/17202.48.0.1 to 202.48.127.254202.48.127.25532,766
98202.48.128.0/17202.48.128.1 to 202.48.255.254202.48.255.25532,766
99202.49.0.0/17202.49.0.1 to 202.49.127.254202.49.127.25532,766
100202.49.128.0/17202.49.128.1 to 202.49.255.254202.49.255.25532,766
101202.50.0.0/17202.50.0.1 to 202.50.127.254202.50.127.25532,766
102202.50.128.0/17202.50.128.1 to 202.50.255.254202.50.255.25532,766
103202.51.0.0/17202.51.0.1 to 202.51.127.254202.51.127.25532,766
104202.51.128.0/17202.51.128.1 to 202.51.255.254202.51.255.25532,766
105202.52.0.0/17202.52.0.1 to 202.52.127.254202.52.127.25532,766
106202.52.128.0/17202.52.128.1 to 202.52.255.254202.52.255.25532,766
107202.53.0.0/17202.53.0.1 to 202.53.127.254202.53.127.25532,766
108202.53.128.0/17202.53.128.1 to 202.53.255.254202.53.255.25532,766
109202.54.0.0/17202.54.0.1 to 202.54.127.254202.54.127.25532,766
110202.54.128.0/17202.54.128.1 to 202.54.255.254202.54.255.25532,766
111202.55.0.0/17202.55.0.1 to 202.55.127.254202.55.127.25532,766
112202.55.128.0/17202.55.128.1 to 202.55.255.254202.55.255.25532,766
113202.56.0.0/17202.56.0.1 to 202.56.127.254202.56.127.25532,766
114202.56.128.0/17202.56.128.1 to 202.56.255.254202.56.255.25532,766
115202.57.0.0/17202.57.0.1 to 202.57.127.254202.57.127.25532,766
116202.57.128.0/17202.57.128.1 to 202.57.255.254202.57.255.25532,766
117202.58.0.0/17202.58.0.1 to 202.58.127.254202.58.127.25532,766
118202.58.128.0/17202.58.128.1 to 202.58.255.254202.58.255.25532,766
119202.59.0.0/17202.59.0.1 to 202.59.127.254202.59.127.25532,766
120202.59.128.0/17202.59.128.1 to 202.59.255.254202.59.255.25532,766
121202.60.0.0/17202.60.0.1 to 202.60.127.254202.60.127.25532,766
122202.60.128.0/17202.60.128.1 to 202.60.255.254202.60.255.25532,766
123202.61.0.0/17202.61.0.1 to 202.61.127.254202.61.127.25532,766
124202.61.128.0/17202.61.128.1 to 202.61.255.254202.61.255.25532,766
125202.62.0.0/17202.62.0.1 to 202.62.127.254202.62.127.25532,766
126202.62.128.0/17202.62.128.1 to 202.62.255.254202.62.255.25532,766
127202.63.0.0/17202.63.0.1 to 202.63.127.254202.63.127.25532,766
128202.63.128.0/17202.63.128.1 to 202.63.255.254202.63.255.25532,766
129202.64.0.0/17202.64.0.1 to 202.64.127.254202.64.127.25532,766
130202.64.128.0/17202.64.128.1 to 202.64.255.254202.64.255.25532,766
131202.65.0.0/17202.65.0.1 to 202.65.127.254202.65.127.25532,766
132202.65.128.0/17202.65.128.1 to 202.65.255.254202.65.255.25532,766
133202.66.0.0/17202.66.0.1 to 202.66.127.254202.66.127.25532,766
134202.66.128.0/17202.66.128.1 to 202.66.255.254202.66.255.25532,766
135202.67.0.0/17202.67.0.1 to 202.67.127.254202.67.127.25532,766
136202.67.128.0/17202.67.128.1 to 202.67.255.254202.67.255.25532,766
137202.68.0.0/17202.68.0.1 to 202.68.127.254202.68.127.25532,766
138202.68.128.0/17202.68.128.1 to 202.68.255.254202.68.255.25532,766
139202.69.0.0/17202.69.0.1 to 202.69.127.254202.69.127.25532,766
140202.69.128.0/17202.69.128.1 to 202.69.255.254202.69.255.25532,766
141202.70.0.0/17202.70.0.1 to 202.70.127.254202.70.127.25532,766
142202.70.128.0/17202.70.128.1 to 202.70.255.254202.70.255.25532,766
143202.71.0.0/17202.71.0.1 to 202.71.127.254202.71.127.25532,766
144202.71.128.0/17202.71.128.1 to 202.71.255.254202.71.255.25532,766
145202.72.0.0/17202.72.0.1 to 202.72.127.254202.72.127.25532,766
146202.72.128.0/17202.72.128.1 to 202.72.255.254202.72.255.25532,766
147202.73.0.0/17202.73.0.1 to 202.73.127.254202.73.127.25532,766
148202.73.128.0/17202.73.128.1 to 202.73.255.254202.73.255.25532,766
149202.74.0.0/17202.74.0.1 to 202.74.127.254202.74.127.25532,766
150202.74.128.0/17202.74.128.1 to 202.74.255.254202.74.255.25532,766
151202.75.0.0/17202.75.0.1 to 202.75.127.254202.75.127.25532,766
152202.75.128.0/17202.75.128.1 to 202.75.255.254202.75.255.25532,766
153202.76.0.0/17202.76.0.1 to 202.76.127.254202.76.127.25532,766
154202.76.128.0/17202.76.128.1 to 202.76.255.254202.76.255.25532,766
155202.77.0.0/17202.77.0.1 to 202.77.127.254202.77.127.25532,766
156202.77.128.0/17202.77.128.1 to 202.77.255.254202.77.255.25532,766
157202.78.0.0/17202.78.0.1 to 202.78.127.254202.78.127.25532,766
158202.78.128.0/17202.78.128.1 to 202.78.255.254202.78.255.25532,766
159202.79.0.0/17202.79.0.1 to 202.79.127.254202.79.127.25532,766
160202.79.128.0/17202.79.128.1 to 202.79.255.254202.79.255.25532,766
161202.80.0.0/17202.80.0.1 to 202.80.127.254202.80.127.25532,766
162202.80.128.0/17202.80.128.1 to 202.80.255.254202.80.255.25532,766
163202.81.0.0/17202.81.0.1 to 202.81.127.254202.81.127.25532,766
164202.81.128.0/17202.81.128.1 to 202.81.255.254202.81.255.25532,766
165202.82.0.0/17202.82.0.1 to 202.82.127.254202.82.127.25532,766
166202.82.128.0/17202.82.128.1 to 202.82.255.254202.82.255.25532,766
167202.83.0.0/17202.83.0.1 to 202.83.127.254202.83.127.25532,766
168202.83.128.0/17202.83.128.1 to 202.83.255.254202.83.255.25532,766
169202.84.0.0/17202.84.0.1 to 202.84.127.254202.84.127.25532,766
170202.84.128.0/17202.84.128.1 to 202.84.255.254202.84.255.25532,766
171202.85.0.0/17202.85.0.1 to 202.85.127.254202.85.127.25532,766
172202.85.128.0/17202.85.128.1 to 202.85.255.254202.85.255.25532,766
173202.86.0.0/17202.86.0.1 to 202.86.127.254202.86.127.25532,766
174202.86.128.0/17202.86.128.1 to 202.86.255.254202.86.255.25532,766
175202.87.0.0/17202.87.0.1 to 202.87.127.254202.87.127.25532,766
176202.87.128.0/17202.87.128.1 to 202.87.255.254202.87.255.25532,766
177202.88.0.0/17202.88.0.1 to 202.88.127.254202.88.127.25532,766
178202.88.128.0/17202.88.128.1 to 202.88.255.254202.88.255.25532,766
179202.89.0.0/17202.89.0.1 to 202.89.127.254202.89.127.25532,766
180202.89.128.0/17202.89.128.1 to 202.89.255.254202.89.255.25532,766
181202.90.0.0/17202.90.0.1 to 202.90.127.254202.90.127.25532,766
182202.90.128.0/17202.90.128.1 to 202.90.255.254202.90.255.25532,766
183202.91.0.0/17202.91.0.1 to 202.91.127.254202.91.127.25532,766
184202.91.128.0/17202.91.128.1 to 202.91.255.254202.91.255.25532,766
185202.92.0.0/17202.92.0.1 to 202.92.127.254202.92.127.25532,766
186202.92.128.0/17202.92.128.1 to 202.92.255.254202.92.255.25532,766
187202.93.0.0/17202.93.0.1 to 202.93.127.254202.93.127.25532,766
188202.93.128.0/17202.93.128.1 to 202.93.255.254202.93.255.25532,766
189202.94.0.0/17202.94.0.1 to 202.94.127.254202.94.127.25532,766
190202.94.128.0/17202.94.128.1 to 202.94.255.254202.94.255.25532,766
191202.95.0.0/17202.95.0.1 to 202.95.127.254202.95.127.25532,766
192202.95.128.0/17202.95.128.1 to 202.95.255.254202.95.255.25532,766
193202.96.0.0/17202.96.0.1 to 202.96.127.254202.96.127.25532,766
194202.96.128.0/17202.96.128.1 to 202.96.255.254202.96.255.25532,766
195202.97.0.0/17202.97.0.1 to 202.97.127.254202.97.127.25532,766
196202.97.128.0/17202.97.128.1 to 202.97.255.254202.97.255.25532,766
197202.98.0.0/17202.98.0.1 to 202.98.127.254202.98.127.25532,766
198202.98.128.0/17202.98.128.1 to 202.98.255.254202.98.255.25532,766
199202.99.0.0/17202.99.0.1 to 202.99.127.254202.99.127.25532,766
200202.99.128.0/17202.99.128.1 to 202.99.255.254202.99.255.25532,766
201202.100.0.0/17202.100.0.1 to 202.100.127.254202.100.127.25532,766
202202.100.128.0/17202.100.128.1 to 202.100.255.254202.100.255.25532,766
203202.101.0.0/17202.101.0.1 to 202.101.127.254202.101.127.25532,766
204202.101.128.0/17202.101.128.1 to 202.101.255.254202.101.255.25532,766
205202.102.0.0/17202.102.0.1 to 202.102.127.254202.102.127.25532,766
206202.102.128.0/17202.102.128.1 to 202.102.255.254202.102.255.25532,766
207202.103.0.0/17202.103.0.1 to 202.103.127.254202.103.127.25532,766
208202.103.128.0/17202.103.128.1 to 202.103.255.254202.103.255.25532,766
209202.104.0.0/17202.104.0.1 to 202.104.127.254202.104.127.25532,766
210202.104.128.0/17202.104.128.1 to 202.104.255.254202.104.255.25532,766
211202.105.0.0/17202.105.0.1 to 202.105.127.254202.105.127.25532,766
212202.105.128.0/17202.105.128.1 to 202.105.255.254202.105.255.25532,766
213202.106.0.0/17202.106.0.1 to 202.106.127.254202.106.127.25532,766
214202.106.128.0/17202.106.128.1 to 202.106.255.254202.106.255.25532,766
215202.107.0.0/17202.107.0.1 to 202.107.127.254202.107.127.25532,766
216202.107.128.0/17202.107.128.1 to 202.107.255.254202.107.255.25532,766
217202.108.0.0/17202.108.0.1 to 202.108.127.254202.108.127.25532,766
218202.108.128.0/17202.108.128.1 to 202.108.255.254202.108.255.25532,766
219202.109.0.0/17202.109.0.1 to 202.109.127.254202.109.127.25532,766
220202.109.128.0/17202.109.128.1 to 202.109.255.254202.109.255.25532,766
221202.110.0.0/17202.110.0.1 to 202.110.127.254202.110.127.25532,766
222202.110.128.0/17202.110.128.1 to 202.110.255.254202.110.255.25532,766
223202.111.0.0/17202.111.0.1 to 202.111.127.254202.111.127.25532,766
224202.111.128.0/17202.111.128.1 to 202.111.255.254202.111.255.25532,766
225202.112.0.0/17202.112.0.1 to 202.112.127.254202.112.127.25532,766
226202.112.128.0/17202.112.128.1 to 202.112.255.254202.112.255.25532,766
227202.113.0.0/17202.113.0.1 to 202.113.127.254202.113.127.25532,766
228202.113.128.0/17202.113.128.1 to 202.113.255.254202.113.255.25532,766
229202.114.0.0/17202.114.0.1 to 202.114.127.254202.114.127.25532,766
230202.114.128.0/17202.114.128.1 to 202.114.255.254202.114.255.25532,766
231202.115.0.0/17202.115.0.1 to 202.115.127.254202.115.127.25532,766
232202.115.128.0/17202.115.128.1 to 202.115.255.254202.115.255.25532,766
233202.116.0.0/17202.116.0.1 to 202.116.127.254202.116.127.25532,766
234202.116.128.0/17202.116.128.1 to 202.116.255.254202.116.255.25532,766
235202.117.0.0/17202.117.0.1 to 202.117.127.254202.117.127.25532,766
236202.117.128.0/17202.117.128.1 to 202.117.255.254202.117.255.25532,766
237202.118.0.0/17202.118.0.1 to 202.118.127.254202.118.127.25532,766
238202.118.128.0/17202.118.128.1 to 202.118.255.254202.118.255.25532,766
239202.119.0.0/17202.119.0.1 to 202.119.127.254202.119.127.25532,766
240202.119.128.0/17202.119.128.1 to 202.119.255.254202.119.255.25532,766
241202.120.0.0/17202.120.0.1 to 202.120.127.254202.120.127.25532,766
242202.120.128.0/17202.120.128.1 to 202.120.255.254202.120.255.25532,766
243202.121.0.0/17202.121.0.1 to 202.121.127.254202.121.127.25532,766
244202.121.128.0/17202.121.128.1 to 202.121.255.254202.121.255.25532,766
245202.122.0.0/17202.122.0.1 to 202.122.127.254202.122.127.25532,766
246202.122.128.0/17202.122.128.1 to 202.122.255.254202.122.255.25532,766
247202.123.0.0/17202.123.0.1 to 202.123.127.254202.123.127.25532,766
248202.123.128.0/17202.123.128.1 to 202.123.255.254202.123.255.25532,766
249202.124.0.0/17202.124.0.1 to 202.124.127.254202.124.127.25532,766
250202.124.128.0/17202.124.128.1 to 202.124.255.254202.124.255.25532,766
251202.125.0.0/17202.125.0.1 to 202.125.127.254202.125.127.25532,766
252202.125.128.0/17202.125.128.1 to 202.125.255.254202.125.255.25532,766
253202.126.0.0/17202.126.0.1 to 202.126.127.254202.126.127.25532,766
254202.126.128.0/17202.126.128.1 to 202.126.255.254202.126.255.25532,766
255202.127.0.0/17202.127.0.1 to 202.127.127.254202.127.127.25532,766
256202.127.128.0/17202.127.128.1 to 202.127.255.254202.127.255.25532,766

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.