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.

Network204.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
204.0.0.0
Broadcast address
204.255.255.255
First usable
204.0.0.1
Last usable
204.255.255.254
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 CC000000 · Integer 3422552064 to 3439329279
Reverse DNS zone
204.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11001100..00000000.00000000.00000000204.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network11001100..00000000.00000000.00000000204.0.0.0
Broadcast11001100..11111111.11111111.11111111204.255.255.255
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)

204.0.0.0/8 makes 1,024 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1204.0.0.0/18204.0.0.1 to 204.0.63.254204.0.63.25516,382
2204.0.64.0/18204.0.64.1 to 204.0.127.254204.0.127.25516,382
3204.0.128.0/18204.0.128.1 to 204.0.191.254204.0.191.25516,382
4204.0.192.0/18204.0.192.1 to 204.0.255.254204.0.255.25516,382
5204.1.0.0/18204.1.0.1 to 204.1.63.254204.1.63.25516,382
6204.1.64.0/18204.1.64.1 to 204.1.127.254204.1.127.25516,382
7204.1.128.0/18204.1.128.1 to 204.1.191.254204.1.191.25516,382
8204.1.192.0/18204.1.192.1 to 204.1.255.254204.1.255.25516,382
9204.2.0.0/18204.2.0.1 to 204.2.63.254204.2.63.25516,382
10204.2.64.0/18204.2.64.1 to 204.2.127.254204.2.127.25516,382
11204.2.128.0/18204.2.128.1 to 204.2.191.254204.2.191.25516,382
12204.2.192.0/18204.2.192.1 to 204.2.255.254204.2.255.25516,382
13204.3.0.0/18204.3.0.1 to 204.3.63.254204.3.63.25516,382
14204.3.64.0/18204.3.64.1 to 204.3.127.254204.3.127.25516,382
15204.3.128.0/18204.3.128.1 to 204.3.191.254204.3.191.25516,382
16204.3.192.0/18204.3.192.1 to 204.3.255.254204.3.255.25516,382
17204.4.0.0/18204.4.0.1 to 204.4.63.254204.4.63.25516,382
18204.4.64.0/18204.4.64.1 to 204.4.127.254204.4.127.25516,382
19204.4.128.0/18204.4.128.1 to 204.4.191.254204.4.191.25516,382
20204.4.192.0/18204.4.192.1 to 204.4.255.254204.4.255.25516,382
21204.5.0.0/18204.5.0.1 to 204.5.63.254204.5.63.25516,382
22204.5.64.0/18204.5.64.1 to 204.5.127.254204.5.127.25516,382
23204.5.128.0/18204.5.128.1 to 204.5.191.254204.5.191.25516,382
24204.5.192.0/18204.5.192.1 to 204.5.255.254204.5.255.25516,382
25204.6.0.0/18204.6.0.1 to 204.6.63.254204.6.63.25516,382
26204.6.64.0/18204.6.64.1 to 204.6.127.254204.6.127.25516,382
27204.6.128.0/18204.6.128.1 to 204.6.191.254204.6.191.25516,382
28204.6.192.0/18204.6.192.1 to 204.6.255.254204.6.255.25516,382
29204.7.0.0/18204.7.0.1 to 204.7.63.254204.7.63.25516,382
30204.7.64.0/18204.7.64.1 to 204.7.127.254204.7.127.25516,382
31204.7.128.0/18204.7.128.1 to 204.7.191.254204.7.191.25516,382
32204.7.192.0/18204.7.192.1 to 204.7.255.254204.7.255.25516,382
33204.8.0.0/18204.8.0.1 to 204.8.63.254204.8.63.25516,382
34204.8.64.0/18204.8.64.1 to 204.8.127.254204.8.127.25516,382
35204.8.128.0/18204.8.128.1 to 204.8.191.254204.8.191.25516,382
36204.8.192.0/18204.8.192.1 to 204.8.255.254204.8.255.25516,382
37204.9.0.0/18204.9.0.1 to 204.9.63.254204.9.63.25516,382
38204.9.64.0/18204.9.64.1 to 204.9.127.254204.9.127.25516,382
39204.9.128.0/18204.9.128.1 to 204.9.191.254204.9.191.25516,382
40204.9.192.0/18204.9.192.1 to 204.9.255.254204.9.255.25516,382
41204.10.0.0/18204.10.0.1 to 204.10.63.254204.10.63.25516,382
42204.10.64.0/18204.10.64.1 to 204.10.127.254204.10.127.25516,382
43204.10.128.0/18204.10.128.1 to 204.10.191.254204.10.191.25516,382
44204.10.192.0/18204.10.192.1 to 204.10.255.254204.10.255.25516,382
45204.11.0.0/18204.11.0.1 to 204.11.63.254204.11.63.25516,382
46204.11.64.0/18204.11.64.1 to 204.11.127.254204.11.127.25516,382
47204.11.128.0/18204.11.128.1 to 204.11.191.254204.11.191.25516,382
48204.11.192.0/18204.11.192.1 to 204.11.255.254204.11.255.25516,382
49204.12.0.0/18204.12.0.1 to 204.12.63.254204.12.63.25516,382
50204.12.64.0/18204.12.64.1 to 204.12.127.254204.12.127.25516,382
51204.12.128.0/18204.12.128.1 to 204.12.191.254204.12.191.25516,382
52204.12.192.0/18204.12.192.1 to 204.12.255.254204.12.255.25516,382
53204.13.0.0/18204.13.0.1 to 204.13.63.254204.13.63.25516,382
54204.13.64.0/18204.13.64.1 to 204.13.127.254204.13.127.25516,382
55204.13.128.0/18204.13.128.1 to 204.13.191.254204.13.191.25516,382
56204.13.192.0/18204.13.192.1 to 204.13.255.254204.13.255.25516,382
57204.14.0.0/18204.14.0.1 to 204.14.63.254204.14.63.25516,382
58204.14.64.0/18204.14.64.1 to 204.14.127.254204.14.127.25516,382
59204.14.128.0/18204.14.128.1 to 204.14.191.254204.14.191.25516,382
60204.14.192.0/18204.14.192.1 to 204.14.255.254204.14.255.25516,382
61204.15.0.0/18204.15.0.1 to 204.15.63.254204.15.63.25516,382
62204.15.64.0/18204.15.64.1 to 204.15.127.254204.15.127.25516,382
63204.15.128.0/18204.15.128.1 to 204.15.191.254204.15.191.25516,382
64204.15.192.0/18204.15.192.1 to 204.15.255.254204.15.255.25516,382
65204.16.0.0/18204.16.0.1 to 204.16.63.254204.16.63.25516,382
66204.16.64.0/18204.16.64.1 to 204.16.127.254204.16.127.25516,382
67204.16.128.0/18204.16.128.1 to 204.16.191.254204.16.191.25516,382
68204.16.192.0/18204.16.192.1 to 204.16.255.254204.16.255.25516,382
69204.17.0.0/18204.17.0.1 to 204.17.63.254204.17.63.25516,382
70204.17.64.0/18204.17.64.1 to 204.17.127.254204.17.127.25516,382
71204.17.128.0/18204.17.128.1 to 204.17.191.254204.17.191.25516,382
72204.17.192.0/18204.17.192.1 to 204.17.255.254204.17.255.25516,382
73204.18.0.0/18204.18.0.1 to 204.18.63.254204.18.63.25516,382
74204.18.64.0/18204.18.64.1 to 204.18.127.254204.18.127.25516,382
75204.18.128.0/18204.18.128.1 to 204.18.191.254204.18.191.25516,382
76204.18.192.0/18204.18.192.1 to 204.18.255.254204.18.255.25516,382
77204.19.0.0/18204.19.0.1 to 204.19.63.254204.19.63.25516,382
78204.19.64.0/18204.19.64.1 to 204.19.127.254204.19.127.25516,382
79204.19.128.0/18204.19.128.1 to 204.19.191.254204.19.191.25516,382
80204.19.192.0/18204.19.192.1 to 204.19.255.254204.19.255.25516,382
81204.20.0.0/18204.20.0.1 to 204.20.63.254204.20.63.25516,382
82204.20.64.0/18204.20.64.1 to 204.20.127.254204.20.127.25516,382
83204.20.128.0/18204.20.128.1 to 204.20.191.254204.20.191.25516,382
84204.20.192.0/18204.20.192.1 to 204.20.255.254204.20.255.25516,382
85204.21.0.0/18204.21.0.1 to 204.21.63.254204.21.63.25516,382
86204.21.64.0/18204.21.64.1 to 204.21.127.254204.21.127.25516,382
87204.21.128.0/18204.21.128.1 to 204.21.191.254204.21.191.25516,382
88204.21.192.0/18204.21.192.1 to 204.21.255.254204.21.255.25516,382
89204.22.0.0/18204.22.0.1 to 204.22.63.254204.22.63.25516,382
90204.22.64.0/18204.22.64.1 to 204.22.127.254204.22.127.25516,382
91204.22.128.0/18204.22.128.1 to 204.22.191.254204.22.191.25516,382
92204.22.192.0/18204.22.192.1 to 204.22.255.254204.22.255.25516,382
93204.23.0.0/18204.23.0.1 to 204.23.63.254204.23.63.25516,382
94204.23.64.0/18204.23.64.1 to 204.23.127.254204.23.127.25516,382
95204.23.128.0/18204.23.128.1 to 204.23.191.254204.23.191.25516,382
96204.23.192.0/18204.23.192.1 to 204.23.255.254204.23.255.25516,382
97204.24.0.0/18204.24.0.1 to 204.24.63.254204.24.63.25516,382
98204.24.64.0/18204.24.64.1 to 204.24.127.254204.24.127.25516,382
99204.24.128.0/18204.24.128.1 to 204.24.191.254204.24.191.25516,382
100204.24.192.0/18204.24.192.1 to 204.24.255.254204.24.255.25516,382
101204.25.0.0/18204.25.0.1 to 204.25.63.254204.25.63.25516,382
102204.25.64.0/18204.25.64.1 to 204.25.127.254204.25.127.25516,382
103204.25.128.0/18204.25.128.1 to 204.25.191.254204.25.191.25516,382
104204.25.192.0/18204.25.192.1 to 204.25.255.254204.25.255.25516,382
105204.26.0.0/18204.26.0.1 to 204.26.63.254204.26.63.25516,382
106204.26.64.0/18204.26.64.1 to 204.26.127.254204.26.127.25516,382
107204.26.128.0/18204.26.128.1 to 204.26.191.254204.26.191.25516,382
108204.26.192.0/18204.26.192.1 to 204.26.255.254204.26.255.25516,382
109204.27.0.0/18204.27.0.1 to 204.27.63.254204.27.63.25516,382
110204.27.64.0/18204.27.64.1 to 204.27.127.254204.27.127.25516,382
111204.27.128.0/18204.27.128.1 to 204.27.191.254204.27.191.25516,382
112204.27.192.0/18204.27.192.1 to 204.27.255.254204.27.255.25516,382
113204.28.0.0/18204.28.0.1 to 204.28.63.254204.28.63.25516,382
114204.28.64.0/18204.28.64.1 to 204.28.127.254204.28.127.25516,382
115204.28.128.0/18204.28.128.1 to 204.28.191.254204.28.191.25516,382
116204.28.192.0/18204.28.192.1 to 204.28.255.254204.28.255.25516,382
117204.29.0.0/18204.29.0.1 to 204.29.63.254204.29.63.25516,382
118204.29.64.0/18204.29.64.1 to 204.29.127.254204.29.127.25516,382
119204.29.128.0/18204.29.128.1 to 204.29.191.254204.29.191.25516,382
120204.29.192.0/18204.29.192.1 to 204.29.255.254204.29.255.25516,382
121204.30.0.0/18204.30.0.1 to 204.30.63.254204.30.63.25516,382
122204.30.64.0/18204.30.64.1 to 204.30.127.254204.30.127.25516,382
123204.30.128.0/18204.30.128.1 to 204.30.191.254204.30.191.25516,382
124204.30.192.0/18204.30.192.1 to 204.30.255.254204.30.255.25516,382
125204.31.0.0/18204.31.0.1 to 204.31.63.254204.31.63.25516,382
126204.31.64.0/18204.31.64.1 to 204.31.127.254204.31.127.25516,382
127204.31.128.0/18204.31.128.1 to 204.31.191.254204.31.191.25516,382
128204.31.192.0/18204.31.192.1 to 204.31.255.254204.31.255.25516,382
129204.32.0.0/18204.32.0.1 to 204.32.63.254204.32.63.25516,382
130204.32.64.0/18204.32.64.1 to 204.32.127.254204.32.127.25516,382
131204.32.128.0/18204.32.128.1 to 204.32.191.254204.32.191.25516,382
132204.32.192.0/18204.32.192.1 to 204.32.255.254204.32.255.25516,382
133204.33.0.0/18204.33.0.1 to 204.33.63.254204.33.63.25516,382
134204.33.64.0/18204.33.64.1 to 204.33.127.254204.33.127.25516,382
135204.33.128.0/18204.33.128.1 to 204.33.191.254204.33.191.25516,382
136204.33.192.0/18204.33.192.1 to 204.33.255.254204.33.255.25516,382
137204.34.0.0/18204.34.0.1 to 204.34.63.254204.34.63.25516,382
138204.34.64.0/18204.34.64.1 to 204.34.127.254204.34.127.25516,382
139204.34.128.0/18204.34.128.1 to 204.34.191.254204.34.191.25516,382
140204.34.192.0/18204.34.192.1 to 204.34.255.254204.34.255.25516,382
141204.35.0.0/18204.35.0.1 to 204.35.63.254204.35.63.25516,382
142204.35.64.0/18204.35.64.1 to 204.35.127.254204.35.127.25516,382
143204.35.128.0/18204.35.128.1 to 204.35.191.254204.35.191.25516,382
144204.35.192.0/18204.35.192.1 to 204.35.255.254204.35.255.25516,382
145204.36.0.0/18204.36.0.1 to 204.36.63.254204.36.63.25516,382
146204.36.64.0/18204.36.64.1 to 204.36.127.254204.36.127.25516,382
147204.36.128.0/18204.36.128.1 to 204.36.191.254204.36.191.25516,382
148204.36.192.0/18204.36.192.1 to 204.36.255.254204.36.255.25516,382
149204.37.0.0/18204.37.0.1 to 204.37.63.254204.37.63.25516,382
150204.37.64.0/18204.37.64.1 to 204.37.127.254204.37.127.25516,382
151204.37.128.0/18204.37.128.1 to 204.37.191.254204.37.191.25516,382
152204.37.192.0/18204.37.192.1 to 204.37.255.254204.37.255.25516,382
153204.38.0.0/18204.38.0.1 to 204.38.63.254204.38.63.25516,382
154204.38.64.0/18204.38.64.1 to 204.38.127.254204.38.127.25516,382
155204.38.128.0/18204.38.128.1 to 204.38.191.254204.38.191.25516,382
156204.38.192.0/18204.38.192.1 to 204.38.255.254204.38.255.25516,382
157204.39.0.0/18204.39.0.1 to 204.39.63.254204.39.63.25516,382
158204.39.64.0/18204.39.64.1 to 204.39.127.254204.39.127.25516,382
159204.39.128.0/18204.39.128.1 to 204.39.191.254204.39.191.25516,382
160204.39.192.0/18204.39.192.1 to 204.39.255.254204.39.255.25516,382
161204.40.0.0/18204.40.0.1 to 204.40.63.254204.40.63.25516,382
162204.40.64.0/18204.40.64.1 to 204.40.127.254204.40.127.25516,382
163204.40.128.0/18204.40.128.1 to 204.40.191.254204.40.191.25516,382
164204.40.192.0/18204.40.192.1 to 204.40.255.254204.40.255.25516,382
165204.41.0.0/18204.41.0.1 to 204.41.63.254204.41.63.25516,382
166204.41.64.0/18204.41.64.1 to 204.41.127.254204.41.127.25516,382
167204.41.128.0/18204.41.128.1 to 204.41.191.254204.41.191.25516,382
168204.41.192.0/18204.41.192.1 to 204.41.255.254204.41.255.25516,382
169204.42.0.0/18204.42.0.1 to 204.42.63.254204.42.63.25516,382
170204.42.64.0/18204.42.64.1 to 204.42.127.254204.42.127.25516,382
171204.42.128.0/18204.42.128.1 to 204.42.191.254204.42.191.25516,382
172204.42.192.0/18204.42.192.1 to 204.42.255.254204.42.255.25516,382
173204.43.0.0/18204.43.0.1 to 204.43.63.254204.43.63.25516,382
174204.43.64.0/18204.43.64.1 to 204.43.127.254204.43.127.25516,382
175204.43.128.0/18204.43.128.1 to 204.43.191.254204.43.191.25516,382
176204.43.192.0/18204.43.192.1 to 204.43.255.254204.43.255.25516,382
177204.44.0.0/18204.44.0.1 to 204.44.63.254204.44.63.25516,382
178204.44.64.0/18204.44.64.1 to 204.44.127.254204.44.127.25516,382
179204.44.128.0/18204.44.128.1 to 204.44.191.254204.44.191.25516,382
180204.44.192.0/18204.44.192.1 to 204.44.255.254204.44.255.25516,382
181204.45.0.0/18204.45.0.1 to 204.45.63.254204.45.63.25516,382
182204.45.64.0/18204.45.64.1 to 204.45.127.254204.45.127.25516,382
183204.45.128.0/18204.45.128.1 to 204.45.191.254204.45.191.25516,382
184204.45.192.0/18204.45.192.1 to 204.45.255.254204.45.255.25516,382
185204.46.0.0/18204.46.0.1 to 204.46.63.254204.46.63.25516,382
186204.46.64.0/18204.46.64.1 to 204.46.127.254204.46.127.25516,382
187204.46.128.0/18204.46.128.1 to 204.46.191.254204.46.191.25516,382
188204.46.192.0/18204.46.192.1 to 204.46.255.254204.46.255.25516,382
189204.47.0.0/18204.47.0.1 to 204.47.63.254204.47.63.25516,382
190204.47.64.0/18204.47.64.1 to 204.47.127.254204.47.127.25516,382
191204.47.128.0/18204.47.128.1 to 204.47.191.254204.47.191.25516,382
192204.47.192.0/18204.47.192.1 to 204.47.255.254204.47.255.25516,382
193204.48.0.0/18204.48.0.1 to 204.48.63.254204.48.63.25516,382
194204.48.64.0/18204.48.64.1 to 204.48.127.254204.48.127.25516,382
195204.48.128.0/18204.48.128.1 to 204.48.191.254204.48.191.25516,382
196204.48.192.0/18204.48.192.1 to 204.48.255.254204.48.255.25516,382
197204.49.0.0/18204.49.0.1 to 204.49.63.254204.49.63.25516,382
198204.49.64.0/18204.49.64.1 to 204.49.127.254204.49.127.25516,382
199204.49.128.0/18204.49.128.1 to 204.49.191.254204.49.191.25516,382
200204.49.192.0/18204.49.192.1 to 204.49.255.254204.49.255.25516,382
201204.50.0.0/18204.50.0.1 to 204.50.63.254204.50.63.25516,382
202204.50.64.0/18204.50.64.1 to 204.50.127.254204.50.127.25516,382
203204.50.128.0/18204.50.128.1 to 204.50.191.254204.50.191.25516,382
204204.50.192.0/18204.50.192.1 to 204.50.255.254204.50.255.25516,382
205204.51.0.0/18204.51.0.1 to 204.51.63.254204.51.63.25516,382
206204.51.64.0/18204.51.64.1 to 204.51.127.254204.51.127.25516,382
207204.51.128.0/18204.51.128.1 to 204.51.191.254204.51.191.25516,382
208204.51.192.0/18204.51.192.1 to 204.51.255.254204.51.255.25516,382
209204.52.0.0/18204.52.0.1 to 204.52.63.254204.52.63.25516,382
210204.52.64.0/18204.52.64.1 to 204.52.127.254204.52.127.25516,382
211204.52.128.0/18204.52.128.1 to 204.52.191.254204.52.191.25516,382
212204.52.192.0/18204.52.192.1 to 204.52.255.254204.52.255.25516,382
213204.53.0.0/18204.53.0.1 to 204.53.63.254204.53.63.25516,382
214204.53.64.0/18204.53.64.1 to 204.53.127.254204.53.127.25516,382
215204.53.128.0/18204.53.128.1 to 204.53.191.254204.53.191.25516,382
216204.53.192.0/18204.53.192.1 to 204.53.255.254204.53.255.25516,382
217204.54.0.0/18204.54.0.1 to 204.54.63.254204.54.63.25516,382
218204.54.64.0/18204.54.64.1 to 204.54.127.254204.54.127.25516,382
219204.54.128.0/18204.54.128.1 to 204.54.191.254204.54.191.25516,382
220204.54.192.0/18204.54.192.1 to 204.54.255.254204.54.255.25516,382
221204.55.0.0/18204.55.0.1 to 204.55.63.254204.55.63.25516,382
222204.55.64.0/18204.55.64.1 to 204.55.127.254204.55.127.25516,382
223204.55.128.0/18204.55.128.1 to 204.55.191.254204.55.191.25516,382
224204.55.192.0/18204.55.192.1 to 204.55.255.254204.55.255.25516,382
225204.56.0.0/18204.56.0.1 to 204.56.63.254204.56.63.25516,382
226204.56.64.0/18204.56.64.1 to 204.56.127.254204.56.127.25516,382
227204.56.128.0/18204.56.128.1 to 204.56.191.254204.56.191.25516,382
228204.56.192.0/18204.56.192.1 to 204.56.255.254204.56.255.25516,382
229204.57.0.0/18204.57.0.1 to 204.57.63.254204.57.63.25516,382
230204.57.64.0/18204.57.64.1 to 204.57.127.254204.57.127.25516,382
231204.57.128.0/18204.57.128.1 to 204.57.191.254204.57.191.25516,382
232204.57.192.0/18204.57.192.1 to 204.57.255.254204.57.255.25516,382
233204.58.0.0/18204.58.0.1 to 204.58.63.254204.58.63.25516,382
234204.58.64.0/18204.58.64.1 to 204.58.127.254204.58.127.25516,382
235204.58.128.0/18204.58.128.1 to 204.58.191.254204.58.191.25516,382
236204.58.192.0/18204.58.192.1 to 204.58.255.254204.58.255.25516,382
237204.59.0.0/18204.59.0.1 to 204.59.63.254204.59.63.25516,382
238204.59.64.0/18204.59.64.1 to 204.59.127.254204.59.127.25516,382
239204.59.128.0/18204.59.128.1 to 204.59.191.254204.59.191.25516,382
240204.59.192.0/18204.59.192.1 to 204.59.255.254204.59.255.25516,382
241204.60.0.0/18204.60.0.1 to 204.60.63.254204.60.63.25516,382
242204.60.64.0/18204.60.64.1 to 204.60.127.254204.60.127.25516,382
243204.60.128.0/18204.60.128.1 to 204.60.191.254204.60.191.25516,382
244204.60.192.0/18204.60.192.1 to 204.60.255.254204.60.255.25516,382
245204.61.0.0/18204.61.0.1 to 204.61.63.254204.61.63.25516,382
246204.61.64.0/18204.61.64.1 to 204.61.127.254204.61.127.25516,382
247204.61.128.0/18204.61.128.1 to 204.61.191.254204.61.191.25516,382
248204.61.192.0/18204.61.192.1 to 204.61.255.254204.61.255.25516,382
249204.62.0.0/18204.62.0.1 to 204.62.63.254204.62.63.25516,382
250204.62.64.0/18204.62.64.1 to 204.62.127.254204.62.127.25516,382
251204.62.128.0/18204.62.128.1 to 204.62.191.254204.62.191.25516,382
252204.62.192.0/18204.62.192.1 to 204.62.255.254204.62.255.25516,382
253204.63.0.0/18204.63.0.1 to 204.63.63.254204.63.63.25516,382
254204.63.64.0/18204.63.64.1 to 204.63.127.254204.63.127.25516,382
255204.63.128.0/18204.63.128.1 to 204.63.191.254204.63.191.25516,382
256204.63.192.0/18204.63.192.1 to 204.63.255.254204.63.255.25516,382

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.