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.

Network197.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
197.0.0.0
Broadcast address
197.255.255.255
First usable
197.0.0.1
Last usable
197.255.255.254
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
C (default /24)
As numbers
Hex C5000000 · Integer 3305111552 to 3321888767
Reverse DNS zone
197.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11000101..00000000.00000000.00000000197.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network11000101..00000000.00000000.00000000197.0.0.0
Broadcast11000101..11111111.11111111.11111111197.255.255.255
Split into smaller subnets/18
/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)

197.0.0.0/8 makes 1,024 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1197.0.0.0/18197.0.0.1 to 197.0.63.254197.0.63.25516,382
2197.0.64.0/18197.0.64.1 to 197.0.127.254197.0.127.25516,382
3197.0.128.0/18197.0.128.1 to 197.0.191.254197.0.191.25516,382
4197.0.192.0/18197.0.192.1 to 197.0.255.254197.0.255.25516,382
5197.1.0.0/18197.1.0.1 to 197.1.63.254197.1.63.25516,382
6197.1.64.0/18197.1.64.1 to 197.1.127.254197.1.127.25516,382
7197.1.128.0/18197.1.128.1 to 197.1.191.254197.1.191.25516,382
8197.1.192.0/18197.1.192.1 to 197.1.255.254197.1.255.25516,382
9197.2.0.0/18197.2.0.1 to 197.2.63.254197.2.63.25516,382
10197.2.64.0/18197.2.64.1 to 197.2.127.254197.2.127.25516,382
11197.2.128.0/18197.2.128.1 to 197.2.191.254197.2.191.25516,382
12197.2.192.0/18197.2.192.1 to 197.2.255.254197.2.255.25516,382
13197.3.0.0/18197.3.0.1 to 197.3.63.254197.3.63.25516,382
14197.3.64.0/18197.3.64.1 to 197.3.127.254197.3.127.25516,382
15197.3.128.0/18197.3.128.1 to 197.3.191.254197.3.191.25516,382
16197.3.192.0/18197.3.192.1 to 197.3.255.254197.3.255.25516,382
17197.4.0.0/18197.4.0.1 to 197.4.63.254197.4.63.25516,382
18197.4.64.0/18197.4.64.1 to 197.4.127.254197.4.127.25516,382
19197.4.128.0/18197.4.128.1 to 197.4.191.254197.4.191.25516,382
20197.4.192.0/18197.4.192.1 to 197.4.255.254197.4.255.25516,382
21197.5.0.0/18197.5.0.1 to 197.5.63.254197.5.63.25516,382
22197.5.64.0/18197.5.64.1 to 197.5.127.254197.5.127.25516,382
23197.5.128.0/18197.5.128.1 to 197.5.191.254197.5.191.25516,382
24197.5.192.0/18197.5.192.1 to 197.5.255.254197.5.255.25516,382
25197.6.0.0/18197.6.0.1 to 197.6.63.254197.6.63.25516,382
26197.6.64.0/18197.6.64.1 to 197.6.127.254197.6.127.25516,382
27197.6.128.0/18197.6.128.1 to 197.6.191.254197.6.191.25516,382
28197.6.192.0/18197.6.192.1 to 197.6.255.254197.6.255.25516,382
29197.7.0.0/18197.7.0.1 to 197.7.63.254197.7.63.25516,382
30197.7.64.0/18197.7.64.1 to 197.7.127.254197.7.127.25516,382
31197.7.128.0/18197.7.128.1 to 197.7.191.254197.7.191.25516,382
32197.7.192.0/18197.7.192.1 to 197.7.255.254197.7.255.25516,382
33197.8.0.0/18197.8.0.1 to 197.8.63.254197.8.63.25516,382
34197.8.64.0/18197.8.64.1 to 197.8.127.254197.8.127.25516,382
35197.8.128.0/18197.8.128.1 to 197.8.191.254197.8.191.25516,382
36197.8.192.0/18197.8.192.1 to 197.8.255.254197.8.255.25516,382
37197.9.0.0/18197.9.0.1 to 197.9.63.254197.9.63.25516,382
38197.9.64.0/18197.9.64.1 to 197.9.127.254197.9.127.25516,382
39197.9.128.0/18197.9.128.1 to 197.9.191.254197.9.191.25516,382
40197.9.192.0/18197.9.192.1 to 197.9.255.254197.9.255.25516,382
41197.10.0.0/18197.10.0.1 to 197.10.63.254197.10.63.25516,382
42197.10.64.0/18197.10.64.1 to 197.10.127.254197.10.127.25516,382
43197.10.128.0/18197.10.128.1 to 197.10.191.254197.10.191.25516,382
44197.10.192.0/18197.10.192.1 to 197.10.255.254197.10.255.25516,382
45197.11.0.0/18197.11.0.1 to 197.11.63.254197.11.63.25516,382
46197.11.64.0/18197.11.64.1 to 197.11.127.254197.11.127.25516,382
47197.11.128.0/18197.11.128.1 to 197.11.191.254197.11.191.25516,382
48197.11.192.0/18197.11.192.1 to 197.11.255.254197.11.255.25516,382
49197.12.0.0/18197.12.0.1 to 197.12.63.254197.12.63.25516,382
50197.12.64.0/18197.12.64.1 to 197.12.127.254197.12.127.25516,382
51197.12.128.0/18197.12.128.1 to 197.12.191.254197.12.191.25516,382
52197.12.192.0/18197.12.192.1 to 197.12.255.254197.12.255.25516,382
53197.13.0.0/18197.13.0.1 to 197.13.63.254197.13.63.25516,382
54197.13.64.0/18197.13.64.1 to 197.13.127.254197.13.127.25516,382
55197.13.128.0/18197.13.128.1 to 197.13.191.254197.13.191.25516,382
56197.13.192.0/18197.13.192.1 to 197.13.255.254197.13.255.25516,382
57197.14.0.0/18197.14.0.1 to 197.14.63.254197.14.63.25516,382
58197.14.64.0/18197.14.64.1 to 197.14.127.254197.14.127.25516,382
59197.14.128.0/18197.14.128.1 to 197.14.191.254197.14.191.25516,382
60197.14.192.0/18197.14.192.1 to 197.14.255.254197.14.255.25516,382
61197.15.0.0/18197.15.0.1 to 197.15.63.254197.15.63.25516,382
62197.15.64.0/18197.15.64.1 to 197.15.127.254197.15.127.25516,382
63197.15.128.0/18197.15.128.1 to 197.15.191.254197.15.191.25516,382
64197.15.192.0/18197.15.192.1 to 197.15.255.254197.15.255.25516,382
65197.16.0.0/18197.16.0.1 to 197.16.63.254197.16.63.25516,382
66197.16.64.0/18197.16.64.1 to 197.16.127.254197.16.127.25516,382
67197.16.128.0/18197.16.128.1 to 197.16.191.254197.16.191.25516,382
68197.16.192.0/18197.16.192.1 to 197.16.255.254197.16.255.25516,382
69197.17.0.0/18197.17.0.1 to 197.17.63.254197.17.63.25516,382
70197.17.64.0/18197.17.64.1 to 197.17.127.254197.17.127.25516,382
71197.17.128.0/18197.17.128.1 to 197.17.191.254197.17.191.25516,382
72197.17.192.0/18197.17.192.1 to 197.17.255.254197.17.255.25516,382
73197.18.0.0/18197.18.0.1 to 197.18.63.254197.18.63.25516,382
74197.18.64.0/18197.18.64.1 to 197.18.127.254197.18.127.25516,382
75197.18.128.0/18197.18.128.1 to 197.18.191.254197.18.191.25516,382
76197.18.192.0/18197.18.192.1 to 197.18.255.254197.18.255.25516,382
77197.19.0.0/18197.19.0.1 to 197.19.63.254197.19.63.25516,382
78197.19.64.0/18197.19.64.1 to 197.19.127.254197.19.127.25516,382
79197.19.128.0/18197.19.128.1 to 197.19.191.254197.19.191.25516,382
80197.19.192.0/18197.19.192.1 to 197.19.255.254197.19.255.25516,382
81197.20.0.0/18197.20.0.1 to 197.20.63.254197.20.63.25516,382
82197.20.64.0/18197.20.64.1 to 197.20.127.254197.20.127.25516,382
83197.20.128.0/18197.20.128.1 to 197.20.191.254197.20.191.25516,382
84197.20.192.0/18197.20.192.1 to 197.20.255.254197.20.255.25516,382
85197.21.0.0/18197.21.0.1 to 197.21.63.254197.21.63.25516,382
86197.21.64.0/18197.21.64.1 to 197.21.127.254197.21.127.25516,382
87197.21.128.0/18197.21.128.1 to 197.21.191.254197.21.191.25516,382
88197.21.192.0/18197.21.192.1 to 197.21.255.254197.21.255.25516,382
89197.22.0.0/18197.22.0.1 to 197.22.63.254197.22.63.25516,382
90197.22.64.0/18197.22.64.1 to 197.22.127.254197.22.127.25516,382
91197.22.128.0/18197.22.128.1 to 197.22.191.254197.22.191.25516,382
92197.22.192.0/18197.22.192.1 to 197.22.255.254197.22.255.25516,382
93197.23.0.0/18197.23.0.1 to 197.23.63.254197.23.63.25516,382
94197.23.64.0/18197.23.64.1 to 197.23.127.254197.23.127.25516,382
95197.23.128.0/18197.23.128.1 to 197.23.191.254197.23.191.25516,382
96197.23.192.0/18197.23.192.1 to 197.23.255.254197.23.255.25516,382
97197.24.0.0/18197.24.0.1 to 197.24.63.254197.24.63.25516,382
98197.24.64.0/18197.24.64.1 to 197.24.127.254197.24.127.25516,382
99197.24.128.0/18197.24.128.1 to 197.24.191.254197.24.191.25516,382
100197.24.192.0/18197.24.192.1 to 197.24.255.254197.24.255.25516,382
101197.25.0.0/18197.25.0.1 to 197.25.63.254197.25.63.25516,382
102197.25.64.0/18197.25.64.1 to 197.25.127.254197.25.127.25516,382
103197.25.128.0/18197.25.128.1 to 197.25.191.254197.25.191.25516,382
104197.25.192.0/18197.25.192.1 to 197.25.255.254197.25.255.25516,382
105197.26.0.0/18197.26.0.1 to 197.26.63.254197.26.63.25516,382
106197.26.64.0/18197.26.64.1 to 197.26.127.254197.26.127.25516,382
107197.26.128.0/18197.26.128.1 to 197.26.191.254197.26.191.25516,382
108197.26.192.0/18197.26.192.1 to 197.26.255.254197.26.255.25516,382
109197.27.0.0/18197.27.0.1 to 197.27.63.254197.27.63.25516,382
110197.27.64.0/18197.27.64.1 to 197.27.127.254197.27.127.25516,382
111197.27.128.0/18197.27.128.1 to 197.27.191.254197.27.191.25516,382
112197.27.192.0/18197.27.192.1 to 197.27.255.254197.27.255.25516,382
113197.28.0.0/18197.28.0.1 to 197.28.63.254197.28.63.25516,382
114197.28.64.0/18197.28.64.1 to 197.28.127.254197.28.127.25516,382
115197.28.128.0/18197.28.128.1 to 197.28.191.254197.28.191.25516,382
116197.28.192.0/18197.28.192.1 to 197.28.255.254197.28.255.25516,382
117197.29.0.0/18197.29.0.1 to 197.29.63.254197.29.63.25516,382
118197.29.64.0/18197.29.64.1 to 197.29.127.254197.29.127.25516,382
119197.29.128.0/18197.29.128.1 to 197.29.191.254197.29.191.25516,382
120197.29.192.0/18197.29.192.1 to 197.29.255.254197.29.255.25516,382
121197.30.0.0/18197.30.0.1 to 197.30.63.254197.30.63.25516,382
122197.30.64.0/18197.30.64.1 to 197.30.127.254197.30.127.25516,382
123197.30.128.0/18197.30.128.1 to 197.30.191.254197.30.191.25516,382
124197.30.192.0/18197.30.192.1 to 197.30.255.254197.30.255.25516,382
125197.31.0.0/18197.31.0.1 to 197.31.63.254197.31.63.25516,382
126197.31.64.0/18197.31.64.1 to 197.31.127.254197.31.127.25516,382
127197.31.128.0/18197.31.128.1 to 197.31.191.254197.31.191.25516,382
128197.31.192.0/18197.31.192.1 to 197.31.255.254197.31.255.25516,382
129197.32.0.0/18197.32.0.1 to 197.32.63.254197.32.63.25516,382
130197.32.64.0/18197.32.64.1 to 197.32.127.254197.32.127.25516,382
131197.32.128.0/18197.32.128.1 to 197.32.191.254197.32.191.25516,382
132197.32.192.0/18197.32.192.1 to 197.32.255.254197.32.255.25516,382
133197.33.0.0/18197.33.0.1 to 197.33.63.254197.33.63.25516,382
134197.33.64.0/18197.33.64.1 to 197.33.127.254197.33.127.25516,382
135197.33.128.0/18197.33.128.1 to 197.33.191.254197.33.191.25516,382
136197.33.192.0/18197.33.192.1 to 197.33.255.254197.33.255.25516,382
137197.34.0.0/18197.34.0.1 to 197.34.63.254197.34.63.25516,382
138197.34.64.0/18197.34.64.1 to 197.34.127.254197.34.127.25516,382
139197.34.128.0/18197.34.128.1 to 197.34.191.254197.34.191.25516,382
140197.34.192.0/18197.34.192.1 to 197.34.255.254197.34.255.25516,382
141197.35.0.0/18197.35.0.1 to 197.35.63.254197.35.63.25516,382
142197.35.64.0/18197.35.64.1 to 197.35.127.254197.35.127.25516,382
143197.35.128.0/18197.35.128.1 to 197.35.191.254197.35.191.25516,382
144197.35.192.0/18197.35.192.1 to 197.35.255.254197.35.255.25516,382
145197.36.0.0/18197.36.0.1 to 197.36.63.254197.36.63.25516,382
146197.36.64.0/18197.36.64.1 to 197.36.127.254197.36.127.25516,382
147197.36.128.0/18197.36.128.1 to 197.36.191.254197.36.191.25516,382
148197.36.192.0/18197.36.192.1 to 197.36.255.254197.36.255.25516,382
149197.37.0.0/18197.37.0.1 to 197.37.63.254197.37.63.25516,382
150197.37.64.0/18197.37.64.1 to 197.37.127.254197.37.127.25516,382
151197.37.128.0/18197.37.128.1 to 197.37.191.254197.37.191.25516,382
152197.37.192.0/18197.37.192.1 to 197.37.255.254197.37.255.25516,382
153197.38.0.0/18197.38.0.1 to 197.38.63.254197.38.63.25516,382
154197.38.64.0/18197.38.64.1 to 197.38.127.254197.38.127.25516,382
155197.38.128.0/18197.38.128.1 to 197.38.191.254197.38.191.25516,382
156197.38.192.0/18197.38.192.1 to 197.38.255.254197.38.255.25516,382
157197.39.0.0/18197.39.0.1 to 197.39.63.254197.39.63.25516,382
158197.39.64.0/18197.39.64.1 to 197.39.127.254197.39.127.25516,382
159197.39.128.0/18197.39.128.1 to 197.39.191.254197.39.191.25516,382
160197.39.192.0/18197.39.192.1 to 197.39.255.254197.39.255.25516,382
161197.40.0.0/18197.40.0.1 to 197.40.63.254197.40.63.25516,382
162197.40.64.0/18197.40.64.1 to 197.40.127.254197.40.127.25516,382
163197.40.128.0/18197.40.128.1 to 197.40.191.254197.40.191.25516,382
164197.40.192.0/18197.40.192.1 to 197.40.255.254197.40.255.25516,382
165197.41.0.0/18197.41.0.1 to 197.41.63.254197.41.63.25516,382
166197.41.64.0/18197.41.64.1 to 197.41.127.254197.41.127.25516,382
167197.41.128.0/18197.41.128.1 to 197.41.191.254197.41.191.25516,382
168197.41.192.0/18197.41.192.1 to 197.41.255.254197.41.255.25516,382
169197.42.0.0/18197.42.0.1 to 197.42.63.254197.42.63.25516,382
170197.42.64.0/18197.42.64.1 to 197.42.127.254197.42.127.25516,382
171197.42.128.0/18197.42.128.1 to 197.42.191.254197.42.191.25516,382
172197.42.192.0/18197.42.192.1 to 197.42.255.254197.42.255.25516,382
173197.43.0.0/18197.43.0.1 to 197.43.63.254197.43.63.25516,382
174197.43.64.0/18197.43.64.1 to 197.43.127.254197.43.127.25516,382
175197.43.128.0/18197.43.128.1 to 197.43.191.254197.43.191.25516,382
176197.43.192.0/18197.43.192.1 to 197.43.255.254197.43.255.25516,382
177197.44.0.0/18197.44.0.1 to 197.44.63.254197.44.63.25516,382
178197.44.64.0/18197.44.64.1 to 197.44.127.254197.44.127.25516,382
179197.44.128.0/18197.44.128.1 to 197.44.191.254197.44.191.25516,382
180197.44.192.0/18197.44.192.1 to 197.44.255.254197.44.255.25516,382
181197.45.0.0/18197.45.0.1 to 197.45.63.254197.45.63.25516,382
182197.45.64.0/18197.45.64.1 to 197.45.127.254197.45.127.25516,382
183197.45.128.0/18197.45.128.1 to 197.45.191.254197.45.191.25516,382
184197.45.192.0/18197.45.192.1 to 197.45.255.254197.45.255.25516,382
185197.46.0.0/18197.46.0.1 to 197.46.63.254197.46.63.25516,382
186197.46.64.0/18197.46.64.1 to 197.46.127.254197.46.127.25516,382
187197.46.128.0/18197.46.128.1 to 197.46.191.254197.46.191.25516,382
188197.46.192.0/18197.46.192.1 to 197.46.255.254197.46.255.25516,382
189197.47.0.0/18197.47.0.1 to 197.47.63.254197.47.63.25516,382
190197.47.64.0/18197.47.64.1 to 197.47.127.254197.47.127.25516,382
191197.47.128.0/18197.47.128.1 to 197.47.191.254197.47.191.25516,382
192197.47.192.0/18197.47.192.1 to 197.47.255.254197.47.255.25516,382
193197.48.0.0/18197.48.0.1 to 197.48.63.254197.48.63.25516,382
194197.48.64.0/18197.48.64.1 to 197.48.127.254197.48.127.25516,382
195197.48.128.0/18197.48.128.1 to 197.48.191.254197.48.191.25516,382
196197.48.192.0/18197.48.192.1 to 197.48.255.254197.48.255.25516,382
197197.49.0.0/18197.49.0.1 to 197.49.63.254197.49.63.25516,382
198197.49.64.0/18197.49.64.1 to 197.49.127.254197.49.127.25516,382
199197.49.128.0/18197.49.128.1 to 197.49.191.254197.49.191.25516,382
200197.49.192.0/18197.49.192.1 to 197.49.255.254197.49.255.25516,382
201197.50.0.0/18197.50.0.1 to 197.50.63.254197.50.63.25516,382
202197.50.64.0/18197.50.64.1 to 197.50.127.254197.50.127.25516,382
203197.50.128.0/18197.50.128.1 to 197.50.191.254197.50.191.25516,382
204197.50.192.0/18197.50.192.1 to 197.50.255.254197.50.255.25516,382
205197.51.0.0/18197.51.0.1 to 197.51.63.254197.51.63.25516,382
206197.51.64.0/18197.51.64.1 to 197.51.127.254197.51.127.25516,382
207197.51.128.0/18197.51.128.1 to 197.51.191.254197.51.191.25516,382
208197.51.192.0/18197.51.192.1 to 197.51.255.254197.51.255.25516,382
209197.52.0.0/18197.52.0.1 to 197.52.63.254197.52.63.25516,382
210197.52.64.0/18197.52.64.1 to 197.52.127.254197.52.127.25516,382
211197.52.128.0/18197.52.128.1 to 197.52.191.254197.52.191.25516,382
212197.52.192.0/18197.52.192.1 to 197.52.255.254197.52.255.25516,382
213197.53.0.0/18197.53.0.1 to 197.53.63.254197.53.63.25516,382
214197.53.64.0/18197.53.64.1 to 197.53.127.254197.53.127.25516,382
215197.53.128.0/18197.53.128.1 to 197.53.191.254197.53.191.25516,382
216197.53.192.0/18197.53.192.1 to 197.53.255.254197.53.255.25516,382
217197.54.0.0/18197.54.0.1 to 197.54.63.254197.54.63.25516,382
218197.54.64.0/18197.54.64.1 to 197.54.127.254197.54.127.25516,382
219197.54.128.0/18197.54.128.1 to 197.54.191.254197.54.191.25516,382
220197.54.192.0/18197.54.192.1 to 197.54.255.254197.54.255.25516,382
221197.55.0.0/18197.55.0.1 to 197.55.63.254197.55.63.25516,382
222197.55.64.0/18197.55.64.1 to 197.55.127.254197.55.127.25516,382
223197.55.128.0/18197.55.128.1 to 197.55.191.254197.55.191.25516,382
224197.55.192.0/18197.55.192.1 to 197.55.255.254197.55.255.25516,382
225197.56.0.0/18197.56.0.1 to 197.56.63.254197.56.63.25516,382
226197.56.64.0/18197.56.64.1 to 197.56.127.254197.56.127.25516,382
227197.56.128.0/18197.56.128.1 to 197.56.191.254197.56.191.25516,382
228197.56.192.0/18197.56.192.1 to 197.56.255.254197.56.255.25516,382
229197.57.0.0/18197.57.0.1 to 197.57.63.254197.57.63.25516,382
230197.57.64.0/18197.57.64.1 to 197.57.127.254197.57.127.25516,382
231197.57.128.0/18197.57.128.1 to 197.57.191.254197.57.191.25516,382
232197.57.192.0/18197.57.192.1 to 197.57.255.254197.57.255.25516,382
233197.58.0.0/18197.58.0.1 to 197.58.63.254197.58.63.25516,382
234197.58.64.0/18197.58.64.1 to 197.58.127.254197.58.127.25516,382
235197.58.128.0/18197.58.128.1 to 197.58.191.254197.58.191.25516,382
236197.58.192.0/18197.58.192.1 to 197.58.255.254197.58.255.25516,382
237197.59.0.0/18197.59.0.1 to 197.59.63.254197.59.63.25516,382
238197.59.64.0/18197.59.64.1 to 197.59.127.254197.59.127.25516,382
239197.59.128.0/18197.59.128.1 to 197.59.191.254197.59.191.25516,382
240197.59.192.0/18197.59.192.1 to 197.59.255.254197.59.255.25516,382
241197.60.0.0/18197.60.0.1 to 197.60.63.254197.60.63.25516,382
242197.60.64.0/18197.60.64.1 to 197.60.127.254197.60.127.25516,382
243197.60.128.0/18197.60.128.1 to 197.60.191.254197.60.191.25516,382
244197.60.192.0/18197.60.192.1 to 197.60.255.254197.60.255.25516,382
245197.61.0.0/18197.61.0.1 to 197.61.63.254197.61.63.25516,382
246197.61.64.0/18197.61.64.1 to 197.61.127.254197.61.127.25516,382
247197.61.128.0/18197.61.128.1 to 197.61.191.254197.61.191.25516,382
248197.61.192.0/18197.61.192.1 to 197.61.255.254197.61.255.25516,382
249197.62.0.0/18197.62.0.1 to 197.62.63.254197.62.63.25516,382
250197.62.64.0/18197.62.64.1 to 197.62.127.254197.62.127.25516,382
251197.62.128.0/18197.62.128.1 to 197.62.191.254197.62.191.25516,382
252197.62.192.0/18197.62.192.1 to 197.62.255.254197.62.255.25516,382
253197.63.0.0/18197.63.0.1 to 197.63.63.254197.63.63.25516,382
254197.63.64.0/18197.63.64.1 to 197.63.127.254197.63.127.25516,382
255197.63.128.0/18197.63.128.1 to 197.63.191.254197.63.191.25516,382
256197.63.192.0/18197.63.192.1 to 197.63.255.254197.63.255.25516,382

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.