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.

Network204.3.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
204.3.0.0
Broadcast address
204.3.127.255
First usable
204.3.0.1
Last usable
204.3.127.254
Usable hosts
32,766 (32,768 less the network and broadcast addresses)
Subnet mask
255.255.128.0
Wildcard mask
0.0.127.255 (Cisco ACLs, OSPF)
Prefix length
/17
Type
Public public
Old class
C (default /24)
As numbers
Hex CC030000 · Integer 3422748672 to 3422781439
Reverse DNS zones
0.3.204.in-addr.arpa
1.3.204.in-addr.arpa
2.3.204.in-addr.arpa
3.3.204.in-addr.arpa
4.3.204.in-addr.arpa
5.3.204.in-addr.arpa
6.3.204.in-addr.arpa
7.3.204.in-addr.arpa
8.3.204.in-addr.arpa
9.3.204.in-addr.arpa
10.3.204.in-addr.arpa
11.3.204.in-addr.arpa
12.3.204.in-addr.arpa
13.3.204.in-addr.arpa
14.3.204.in-addr.arpa
15.3.204.in-addr.arpa
and 112 more
/17 is not on a 8-bit boundary, so it takes 128 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11001100.00000011.00000000.00000000204.3.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network11001100.00000011.00000000.00000000204.3.0.0
Broadcast11001100.00000011.01111111.11111111204.3.127.255
Split into smaller subnets/26
/18 (2)/19 (4)/20 (8)/21 (16)/22 (32)/23 (64)/24 (128)/25 (256)/26 (512)/27 (1,024)/28 (2,048)/29 (4,096)

204.3.0.0/17 makes 512 subnets of /26; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1204.3.0.0/26204.3.0.1 to 204.3.0.62204.3.0.6362
2204.3.0.64/26204.3.0.65 to 204.3.0.126204.3.0.12762
3204.3.0.128/26204.3.0.129 to 204.3.0.190204.3.0.19162
4204.3.0.192/26204.3.0.193 to 204.3.0.254204.3.0.25562
5204.3.1.0/26204.3.1.1 to 204.3.1.62204.3.1.6362
6204.3.1.64/26204.3.1.65 to 204.3.1.126204.3.1.12762
7204.3.1.128/26204.3.1.129 to 204.3.1.190204.3.1.19162
8204.3.1.192/26204.3.1.193 to 204.3.1.254204.3.1.25562
9204.3.2.0/26204.3.2.1 to 204.3.2.62204.3.2.6362
10204.3.2.64/26204.3.2.65 to 204.3.2.126204.3.2.12762
11204.3.2.128/26204.3.2.129 to 204.3.2.190204.3.2.19162
12204.3.2.192/26204.3.2.193 to 204.3.2.254204.3.2.25562
13204.3.3.0/26204.3.3.1 to 204.3.3.62204.3.3.6362
14204.3.3.64/26204.3.3.65 to 204.3.3.126204.3.3.12762
15204.3.3.128/26204.3.3.129 to 204.3.3.190204.3.3.19162
16204.3.3.192/26204.3.3.193 to 204.3.3.254204.3.3.25562
17204.3.4.0/26204.3.4.1 to 204.3.4.62204.3.4.6362
18204.3.4.64/26204.3.4.65 to 204.3.4.126204.3.4.12762
19204.3.4.128/26204.3.4.129 to 204.3.4.190204.3.4.19162
20204.3.4.192/26204.3.4.193 to 204.3.4.254204.3.4.25562
21204.3.5.0/26204.3.5.1 to 204.3.5.62204.3.5.6362
22204.3.5.64/26204.3.5.65 to 204.3.5.126204.3.5.12762
23204.3.5.128/26204.3.5.129 to 204.3.5.190204.3.5.19162
24204.3.5.192/26204.3.5.193 to 204.3.5.254204.3.5.25562
25204.3.6.0/26204.3.6.1 to 204.3.6.62204.3.6.6362
26204.3.6.64/26204.3.6.65 to 204.3.6.126204.3.6.12762
27204.3.6.128/26204.3.6.129 to 204.3.6.190204.3.6.19162
28204.3.6.192/26204.3.6.193 to 204.3.6.254204.3.6.25562
29204.3.7.0/26204.3.7.1 to 204.3.7.62204.3.7.6362
30204.3.7.64/26204.3.7.65 to 204.3.7.126204.3.7.12762
31204.3.7.128/26204.3.7.129 to 204.3.7.190204.3.7.19162
32204.3.7.192/26204.3.7.193 to 204.3.7.254204.3.7.25562
33204.3.8.0/26204.3.8.1 to 204.3.8.62204.3.8.6362
34204.3.8.64/26204.3.8.65 to 204.3.8.126204.3.8.12762
35204.3.8.128/26204.3.8.129 to 204.3.8.190204.3.8.19162
36204.3.8.192/26204.3.8.193 to 204.3.8.254204.3.8.25562
37204.3.9.0/26204.3.9.1 to 204.3.9.62204.3.9.6362
38204.3.9.64/26204.3.9.65 to 204.3.9.126204.3.9.12762
39204.3.9.128/26204.3.9.129 to 204.3.9.190204.3.9.19162
40204.3.9.192/26204.3.9.193 to 204.3.9.254204.3.9.25562
41204.3.10.0/26204.3.10.1 to 204.3.10.62204.3.10.6362
42204.3.10.64/26204.3.10.65 to 204.3.10.126204.3.10.12762
43204.3.10.128/26204.3.10.129 to 204.3.10.190204.3.10.19162
44204.3.10.192/26204.3.10.193 to 204.3.10.254204.3.10.25562
45204.3.11.0/26204.3.11.1 to 204.3.11.62204.3.11.6362
46204.3.11.64/26204.3.11.65 to 204.3.11.126204.3.11.12762
47204.3.11.128/26204.3.11.129 to 204.3.11.190204.3.11.19162
48204.3.11.192/26204.3.11.193 to 204.3.11.254204.3.11.25562
49204.3.12.0/26204.3.12.1 to 204.3.12.62204.3.12.6362
50204.3.12.64/26204.3.12.65 to 204.3.12.126204.3.12.12762
51204.3.12.128/26204.3.12.129 to 204.3.12.190204.3.12.19162
52204.3.12.192/26204.3.12.193 to 204.3.12.254204.3.12.25562
53204.3.13.0/26204.3.13.1 to 204.3.13.62204.3.13.6362
54204.3.13.64/26204.3.13.65 to 204.3.13.126204.3.13.12762
55204.3.13.128/26204.3.13.129 to 204.3.13.190204.3.13.19162
56204.3.13.192/26204.3.13.193 to 204.3.13.254204.3.13.25562
57204.3.14.0/26204.3.14.1 to 204.3.14.62204.3.14.6362
58204.3.14.64/26204.3.14.65 to 204.3.14.126204.3.14.12762
59204.3.14.128/26204.3.14.129 to 204.3.14.190204.3.14.19162
60204.3.14.192/26204.3.14.193 to 204.3.14.254204.3.14.25562
61204.3.15.0/26204.3.15.1 to 204.3.15.62204.3.15.6362
62204.3.15.64/26204.3.15.65 to 204.3.15.126204.3.15.12762
63204.3.15.128/26204.3.15.129 to 204.3.15.190204.3.15.19162
64204.3.15.192/26204.3.15.193 to 204.3.15.254204.3.15.25562
65204.3.16.0/26204.3.16.1 to 204.3.16.62204.3.16.6362
66204.3.16.64/26204.3.16.65 to 204.3.16.126204.3.16.12762
67204.3.16.128/26204.3.16.129 to 204.3.16.190204.3.16.19162
68204.3.16.192/26204.3.16.193 to 204.3.16.254204.3.16.25562
69204.3.17.0/26204.3.17.1 to 204.3.17.62204.3.17.6362
70204.3.17.64/26204.3.17.65 to 204.3.17.126204.3.17.12762
71204.3.17.128/26204.3.17.129 to 204.3.17.190204.3.17.19162
72204.3.17.192/26204.3.17.193 to 204.3.17.254204.3.17.25562
73204.3.18.0/26204.3.18.1 to 204.3.18.62204.3.18.6362
74204.3.18.64/26204.3.18.65 to 204.3.18.126204.3.18.12762
75204.3.18.128/26204.3.18.129 to 204.3.18.190204.3.18.19162
76204.3.18.192/26204.3.18.193 to 204.3.18.254204.3.18.25562
77204.3.19.0/26204.3.19.1 to 204.3.19.62204.3.19.6362
78204.3.19.64/26204.3.19.65 to 204.3.19.126204.3.19.12762
79204.3.19.128/26204.3.19.129 to 204.3.19.190204.3.19.19162
80204.3.19.192/26204.3.19.193 to 204.3.19.254204.3.19.25562
81204.3.20.0/26204.3.20.1 to 204.3.20.62204.3.20.6362
82204.3.20.64/26204.3.20.65 to 204.3.20.126204.3.20.12762
83204.3.20.128/26204.3.20.129 to 204.3.20.190204.3.20.19162
84204.3.20.192/26204.3.20.193 to 204.3.20.254204.3.20.25562
85204.3.21.0/26204.3.21.1 to 204.3.21.62204.3.21.6362
86204.3.21.64/26204.3.21.65 to 204.3.21.126204.3.21.12762
87204.3.21.128/26204.3.21.129 to 204.3.21.190204.3.21.19162
88204.3.21.192/26204.3.21.193 to 204.3.21.254204.3.21.25562
89204.3.22.0/26204.3.22.1 to 204.3.22.62204.3.22.6362
90204.3.22.64/26204.3.22.65 to 204.3.22.126204.3.22.12762
91204.3.22.128/26204.3.22.129 to 204.3.22.190204.3.22.19162
92204.3.22.192/26204.3.22.193 to 204.3.22.254204.3.22.25562
93204.3.23.0/26204.3.23.1 to 204.3.23.62204.3.23.6362
94204.3.23.64/26204.3.23.65 to 204.3.23.126204.3.23.12762
95204.3.23.128/26204.3.23.129 to 204.3.23.190204.3.23.19162
96204.3.23.192/26204.3.23.193 to 204.3.23.254204.3.23.25562
97204.3.24.0/26204.3.24.1 to 204.3.24.62204.3.24.6362
98204.3.24.64/26204.3.24.65 to 204.3.24.126204.3.24.12762
99204.3.24.128/26204.3.24.129 to 204.3.24.190204.3.24.19162
100204.3.24.192/26204.3.24.193 to 204.3.24.254204.3.24.25562
101204.3.25.0/26204.3.25.1 to 204.3.25.62204.3.25.6362
102204.3.25.64/26204.3.25.65 to 204.3.25.126204.3.25.12762
103204.3.25.128/26204.3.25.129 to 204.3.25.190204.3.25.19162
104204.3.25.192/26204.3.25.193 to 204.3.25.254204.3.25.25562
105204.3.26.0/26204.3.26.1 to 204.3.26.62204.3.26.6362
106204.3.26.64/26204.3.26.65 to 204.3.26.126204.3.26.12762
107204.3.26.128/26204.3.26.129 to 204.3.26.190204.3.26.19162
108204.3.26.192/26204.3.26.193 to 204.3.26.254204.3.26.25562
109204.3.27.0/26204.3.27.1 to 204.3.27.62204.3.27.6362
110204.3.27.64/26204.3.27.65 to 204.3.27.126204.3.27.12762
111204.3.27.128/26204.3.27.129 to 204.3.27.190204.3.27.19162
112204.3.27.192/26204.3.27.193 to 204.3.27.254204.3.27.25562
113204.3.28.0/26204.3.28.1 to 204.3.28.62204.3.28.6362
114204.3.28.64/26204.3.28.65 to 204.3.28.126204.3.28.12762
115204.3.28.128/26204.3.28.129 to 204.3.28.190204.3.28.19162
116204.3.28.192/26204.3.28.193 to 204.3.28.254204.3.28.25562
117204.3.29.0/26204.3.29.1 to 204.3.29.62204.3.29.6362
118204.3.29.64/26204.3.29.65 to 204.3.29.126204.3.29.12762
119204.3.29.128/26204.3.29.129 to 204.3.29.190204.3.29.19162
120204.3.29.192/26204.3.29.193 to 204.3.29.254204.3.29.25562
121204.3.30.0/26204.3.30.1 to 204.3.30.62204.3.30.6362
122204.3.30.64/26204.3.30.65 to 204.3.30.126204.3.30.12762
123204.3.30.128/26204.3.30.129 to 204.3.30.190204.3.30.19162
124204.3.30.192/26204.3.30.193 to 204.3.30.254204.3.30.25562
125204.3.31.0/26204.3.31.1 to 204.3.31.62204.3.31.6362
126204.3.31.64/26204.3.31.65 to 204.3.31.126204.3.31.12762
127204.3.31.128/26204.3.31.129 to 204.3.31.190204.3.31.19162
128204.3.31.192/26204.3.31.193 to 204.3.31.254204.3.31.25562
129204.3.32.0/26204.3.32.1 to 204.3.32.62204.3.32.6362
130204.3.32.64/26204.3.32.65 to 204.3.32.126204.3.32.12762
131204.3.32.128/26204.3.32.129 to 204.3.32.190204.3.32.19162
132204.3.32.192/26204.3.32.193 to 204.3.32.254204.3.32.25562
133204.3.33.0/26204.3.33.1 to 204.3.33.62204.3.33.6362
134204.3.33.64/26204.3.33.65 to 204.3.33.126204.3.33.12762
135204.3.33.128/26204.3.33.129 to 204.3.33.190204.3.33.19162
136204.3.33.192/26204.3.33.193 to 204.3.33.254204.3.33.25562
137204.3.34.0/26204.3.34.1 to 204.3.34.62204.3.34.6362
138204.3.34.64/26204.3.34.65 to 204.3.34.126204.3.34.12762
139204.3.34.128/26204.3.34.129 to 204.3.34.190204.3.34.19162
140204.3.34.192/26204.3.34.193 to 204.3.34.254204.3.34.25562
141204.3.35.0/26204.3.35.1 to 204.3.35.62204.3.35.6362
142204.3.35.64/26204.3.35.65 to 204.3.35.126204.3.35.12762
143204.3.35.128/26204.3.35.129 to 204.3.35.190204.3.35.19162
144204.3.35.192/26204.3.35.193 to 204.3.35.254204.3.35.25562
145204.3.36.0/26204.3.36.1 to 204.3.36.62204.3.36.6362
146204.3.36.64/26204.3.36.65 to 204.3.36.126204.3.36.12762
147204.3.36.128/26204.3.36.129 to 204.3.36.190204.3.36.19162
148204.3.36.192/26204.3.36.193 to 204.3.36.254204.3.36.25562
149204.3.37.0/26204.3.37.1 to 204.3.37.62204.3.37.6362
150204.3.37.64/26204.3.37.65 to 204.3.37.126204.3.37.12762
151204.3.37.128/26204.3.37.129 to 204.3.37.190204.3.37.19162
152204.3.37.192/26204.3.37.193 to 204.3.37.254204.3.37.25562
153204.3.38.0/26204.3.38.1 to 204.3.38.62204.3.38.6362
154204.3.38.64/26204.3.38.65 to 204.3.38.126204.3.38.12762
155204.3.38.128/26204.3.38.129 to 204.3.38.190204.3.38.19162
156204.3.38.192/26204.3.38.193 to 204.3.38.254204.3.38.25562
157204.3.39.0/26204.3.39.1 to 204.3.39.62204.3.39.6362
158204.3.39.64/26204.3.39.65 to 204.3.39.126204.3.39.12762
159204.3.39.128/26204.3.39.129 to 204.3.39.190204.3.39.19162
160204.3.39.192/26204.3.39.193 to 204.3.39.254204.3.39.25562
161204.3.40.0/26204.3.40.1 to 204.3.40.62204.3.40.6362
162204.3.40.64/26204.3.40.65 to 204.3.40.126204.3.40.12762
163204.3.40.128/26204.3.40.129 to 204.3.40.190204.3.40.19162
164204.3.40.192/26204.3.40.193 to 204.3.40.254204.3.40.25562
165204.3.41.0/26204.3.41.1 to 204.3.41.62204.3.41.6362
166204.3.41.64/26204.3.41.65 to 204.3.41.126204.3.41.12762
167204.3.41.128/26204.3.41.129 to 204.3.41.190204.3.41.19162
168204.3.41.192/26204.3.41.193 to 204.3.41.254204.3.41.25562
169204.3.42.0/26204.3.42.1 to 204.3.42.62204.3.42.6362
170204.3.42.64/26204.3.42.65 to 204.3.42.126204.3.42.12762
171204.3.42.128/26204.3.42.129 to 204.3.42.190204.3.42.19162
172204.3.42.192/26204.3.42.193 to 204.3.42.254204.3.42.25562
173204.3.43.0/26204.3.43.1 to 204.3.43.62204.3.43.6362
174204.3.43.64/26204.3.43.65 to 204.3.43.126204.3.43.12762
175204.3.43.128/26204.3.43.129 to 204.3.43.190204.3.43.19162
176204.3.43.192/26204.3.43.193 to 204.3.43.254204.3.43.25562
177204.3.44.0/26204.3.44.1 to 204.3.44.62204.3.44.6362
178204.3.44.64/26204.3.44.65 to 204.3.44.126204.3.44.12762
179204.3.44.128/26204.3.44.129 to 204.3.44.190204.3.44.19162
180204.3.44.192/26204.3.44.193 to 204.3.44.254204.3.44.25562
181204.3.45.0/26204.3.45.1 to 204.3.45.62204.3.45.6362
182204.3.45.64/26204.3.45.65 to 204.3.45.126204.3.45.12762
183204.3.45.128/26204.3.45.129 to 204.3.45.190204.3.45.19162
184204.3.45.192/26204.3.45.193 to 204.3.45.254204.3.45.25562
185204.3.46.0/26204.3.46.1 to 204.3.46.62204.3.46.6362
186204.3.46.64/26204.3.46.65 to 204.3.46.126204.3.46.12762
187204.3.46.128/26204.3.46.129 to 204.3.46.190204.3.46.19162
188204.3.46.192/26204.3.46.193 to 204.3.46.254204.3.46.25562
189204.3.47.0/26204.3.47.1 to 204.3.47.62204.3.47.6362
190204.3.47.64/26204.3.47.65 to 204.3.47.126204.3.47.12762
191204.3.47.128/26204.3.47.129 to 204.3.47.190204.3.47.19162
192204.3.47.192/26204.3.47.193 to 204.3.47.254204.3.47.25562
193204.3.48.0/26204.3.48.1 to 204.3.48.62204.3.48.6362
194204.3.48.64/26204.3.48.65 to 204.3.48.126204.3.48.12762
195204.3.48.128/26204.3.48.129 to 204.3.48.190204.3.48.19162
196204.3.48.192/26204.3.48.193 to 204.3.48.254204.3.48.25562
197204.3.49.0/26204.3.49.1 to 204.3.49.62204.3.49.6362
198204.3.49.64/26204.3.49.65 to 204.3.49.126204.3.49.12762
199204.3.49.128/26204.3.49.129 to 204.3.49.190204.3.49.19162
200204.3.49.192/26204.3.49.193 to 204.3.49.254204.3.49.25562
201204.3.50.0/26204.3.50.1 to 204.3.50.62204.3.50.6362
202204.3.50.64/26204.3.50.65 to 204.3.50.126204.3.50.12762
203204.3.50.128/26204.3.50.129 to 204.3.50.190204.3.50.19162
204204.3.50.192/26204.3.50.193 to 204.3.50.254204.3.50.25562
205204.3.51.0/26204.3.51.1 to 204.3.51.62204.3.51.6362
206204.3.51.64/26204.3.51.65 to 204.3.51.126204.3.51.12762
207204.3.51.128/26204.3.51.129 to 204.3.51.190204.3.51.19162
208204.3.51.192/26204.3.51.193 to 204.3.51.254204.3.51.25562
209204.3.52.0/26204.3.52.1 to 204.3.52.62204.3.52.6362
210204.3.52.64/26204.3.52.65 to 204.3.52.126204.3.52.12762
211204.3.52.128/26204.3.52.129 to 204.3.52.190204.3.52.19162
212204.3.52.192/26204.3.52.193 to 204.3.52.254204.3.52.25562
213204.3.53.0/26204.3.53.1 to 204.3.53.62204.3.53.6362
214204.3.53.64/26204.3.53.65 to 204.3.53.126204.3.53.12762
215204.3.53.128/26204.3.53.129 to 204.3.53.190204.3.53.19162
216204.3.53.192/26204.3.53.193 to 204.3.53.254204.3.53.25562
217204.3.54.0/26204.3.54.1 to 204.3.54.62204.3.54.6362
218204.3.54.64/26204.3.54.65 to 204.3.54.126204.3.54.12762
219204.3.54.128/26204.3.54.129 to 204.3.54.190204.3.54.19162
220204.3.54.192/26204.3.54.193 to 204.3.54.254204.3.54.25562
221204.3.55.0/26204.3.55.1 to 204.3.55.62204.3.55.6362
222204.3.55.64/26204.3.55.65 to 204.3.55.126204.3.55.12762
223204.3.55.128/26204.3.55.129 to 204.3.55.190204.3.55.19162
224204.3.55.192/26204.3.55.193 to 204.3.55.254204.3.55.25562
225204.3.56.0/26204.3.56.1 to 204.3.56.62204.3.56.6362
226204.3.56.64/26204.3.56.65 to 204.3.56.126204.3.56.12762
227204.3.56.128/26204.3.56.129 to 204.3.56.190204.3.56.19162
228204.3.56.192/26204.3.56.193 to 204.3.56.254204.3.56.25562
229204.3.57.0/26204.3.57.1 to 204.3.57.62204.3.57.6362
230204.3.57.64/26204.3.57.65 to 204.3.57.126204.3.57.12762
231204.3.57.128/26204.3.57.129 to 204.3.57.190204.3.57.19162
232204.3.57.192/26204.3.57.193 to 204.3.57.254204.3.57.25562
233204.3.58.0/26204.3.58.1 to 204.3.58.62204.3.58.6362
234204.3.58.64/26204.3.58.65 to 204.3.58.126204.3.58.12762
235204.3.58.128/26204.3.58.129 to 204.3.58.190204.3.58.19162
236204.3.58.192/26204.3.58.193 to 204.3.58.254204.3.58.25562
237204.3.59.0/26204.3.59.1 to 204.3.59.62204.3.59.6362
238204.3.59.64/26204.3.59.65 to 204.3.59.126204.3.59.12762
239204.3.59.128/26204.3.59.129 to 204.3.59.190204.3.59.19162
240204.3.59.192/26204.3.59.193 to 204.3.59.254204.3.59.25562
241204.3.60.0/26204.3.60.1 to 204.3.60.62204.3.60.6362
242204.3.60.64/26204.3.60.65 to 204.3.60.126204.3.60.12762
243204.3.60.128/26204.3.60.129 to 204.3.60.190204.3.60.19162
244204.3.60.192/26204.3.60.193 to 204.3.60.254204.3.60.25562
245204.3.61.0/26204.3.61.1 to 204.3.61.62204.3.61.6362
246204.3.61.64/26204.3.61.65 to 204.3.61.126204.3.61.12762
247204.3.61.128/26204.3.61.129 to 204.3.61.190204.3.61.19162
248204.3.61.192/26204.3.61.193 to 204.3.61.254204.3.61.25562
249204.3.62.0/26204.3.62.1 to 204.3.62.62204.3.62.6362
250204.3.62.64/26204.3.62.65 to 204.3.62.126204.3.62.12762
251204.3.62.128/26204.3.62.129 to 204.3.62.190204.3.62.19162
252204.3.62.192/26204.3.62.193 to 204.3.62.254204.3.62.25562
253204.3.63.0/26204.3.63.1 to 204.3.63.62204.3.63.6362
254204.3.63.64/26204.3.63.65 to 204.3.63.126204.3.63.12762
255204.3.63.128/26204.3.63.129 to 204.3.63.190204.3.63.19162
256204.3.63.192/26204.3.63.193 to 204.3.63.254204.3.63.25562

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.