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.

Network208.0.0.0/4
Usable hosts268,435,454
Subnet mask240.0.0.0
Addresses268,435,456
Network address
208.0.0.0
Broadcast address
223.255.255.255
First usable
208.0.0.1
Last usable
223.255.255.254
Usable hosts
268,435,454 (268,435,456 less the network and broadcast addresses)
Subnet mask
240.0.0.0
Wildcard mask
15.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/4
Type
Public public
Old class
C (default /24)
As numbers
Hex D0000000 · Integer 3489660928 to 3758096383
Reverse DNS zones
208.in-addr.arpa
209.in-addr.arpa
210.in-addr.arpa
211.in-addr.arpa
212.in-addr.arpa
213.in-addr.arpa
214.in-addr.arpa
215.in-addr.arpa
216.in-addr.arpa
217.in-addr.arpa
218.in-addr.arpa
219.in-addr.arpa
220.in-addr.arpa
221.in-addr.arpa
222.in-addr.arpa
223.in-addr.arpa
/4 is not on a 8-bit boundary, so it takes 16 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11010000.00000000.00000000.00000000208.0.0.0
Subnet mask11110000.00000000.00000000.00000000240.0.0.0
Network11010000.00000000.00000000.00000000208.0.0.0
Broadcast11011111.11111111.11111111.11111111223.255.255.255
Split into smaller subnets/13
/5 (2)/6 (4)/7 (8)/8 (16)/9 (32)/10 (64)/11 (128)/12 (256)/13 (512)/14 (1,024)/15 (2,048)/16 (4,096)

208.0.0.0/4 makes 512 subnets of /13; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1208.0.0.0/13208.0.0.1 to 208.7.255.254208.7.255.255524,286
2208.8.0.0/13208.8.0.1 to 208.15.255.254208.15.255.255524,286
3208.16.0.0/13208.16.0.1 to 208.23.255.254208.23.255.255524,286
4208.24.0.0/13208.24.0.1 to 208.31.255.254208.31.255.255524,286
5208.32.0.0/13208.32.0.1 to 208.39.255.254208.39.255.255524,286
6208.40.0.0/13208.40.0.1 to 208.47.255.254208.47.255.255524,286
7208.48.0.0/13208.48.0.1 to 208.55.255.254208.55.255.255524,286
8208.56.0.0/13208.56.0.1 to 208.63.255.254208.63.255.255524,286
9208.64.0.0/13208.64.0.1 to 208.71.255.254208.71.255.255524,286
10208.72.0.0/13208.72.0.1 to 208.79.255.254208.79.255.255524,286
11208.80.0.0/13208.80.0.1 to 208.87.255.254208.87.255.255524,286
12208.88.0.0/13208.88.0.1 to 208.95.255.254208.95.255.255524,286
13208.96.0.0/13208.96.0.1 to 208.103.255.254208.103.255.255524,286
14208.104.0.0/13208.104.0.1 to 208.111.255.254208.111.255.255524,286
15208.112.0.0/13208.112.0.1 to 208.119.255.254208.119.255.255524,286
16208.120.0.0/13208.120.0.1 to 208.127.255.254208.127.255.255524,286
17208.128.0.0/13208.128.0.1 to 208.135.255.254208.135.255.255524,286
18208.136.0.0/13208.136.0.1 to 208.143.255.254208.143.255.255524,286
19208.144.0.0/13208.144.0.1 to 208.151.255.254208.151.255.255524,286
20208.152.0.0/13208.152.0.1 to 208.159.255.254208.159.255.255524,286
21208.160.0.0/13208.160.0.1 to 208.167.255.254208.167.255.255524,286
22208.168.0.0/13208.168.0.1 to 208.175.255.254208.175.255.255524,286
23208.176.0.0/13208.176.0.1 to 208.183.255.254208.183.255.255524,286
24208.184.0.0/13208.184.0.1 to 208.191.255.254208.191.255.255524,286
25208.192.0.0/13208.192.0.1 to 208.199.255.254208.199.255.255524,286
26208.200.0.0/13208.200.0.1 to 208.207.255.254208.207.255.255524,286
27208.208.0.0/13208.208.0.1 to 208.215.255.254208.215.255.255524,286
28208.216.0.0/13208.216.0.1 to 208.223.255.254208.223.255.255524,286
29208.224.0.0/13208.224.0.1 to 208.231.255.254208.231.255.255524,286
30208.232.0.0/13208.232.0.1 to 208.239.255.254208.239.255.255524,286
31208.240.0.0/13208.240.0.1 to 208.247.255.254208.247.255.255524,286
32208.248.0.0/13208.248.0.1 to 208.255.255.254208.255.255.255524,286
33209.0.0.0/13209.0.0.1 to 209.7.255.254209.7.255.255524,286
34209.8.0.0/13209.8.0.1 to 209.15.255.254209.15.255.255524,286
35209.16.0.0/13209.16.0.1 to 209.23.255.254209.23.255.255524,286
36209.24.0.0/13209.24.0.1 to 209.31.255.254209.31.255.255524,286
37209.32.0.0/13209.32.0.1 to 209.39.255.254209.39.255.255524,286
38209.40.0.0/13209.40.0.1 to 209.47.255.254209.47.255.255524,286
39209.48.0.0/13209.48.0.1 to 209.55.255.254209.55.255.255524,286
40209.56.0.0/13209.56.0.1 to 209.63.255.254209.63.255.255524,286
41209.64.0.0/13209.64.0.1 to 209.71.255.254209.71.255.255524,286
42209.72.0.0/13209.72.0.1 to 209.79.255.254209.79.255.255524,286
43209.80.0.0/13209.80.0.1 to 209.87.255.254209.87.255.255524,286
44209.88.0.0/13209.88.0.1 to 209.95.255.254209.95.255.255524,286
45209.96.0.0/13209.96.0.1 to 209.103.255.254209.103.255.255524,286
46209.104.0.0/13209.104.0.1 to 209.111.255.254209.111.255.255524,286
47209.112.0.0/13209.112.0.1 to 209.119.255.254209.119.255.255524,286
48209.120.0.0/13209.120.0.1 to 209.127.255.254209.127.255.255524,286
49209.128.0.0/13209.128.0.1 to 209.135.255.254209.135.255.255524,286
50209.136.0.0/13209.136.0.1 to 209.143.255.254209.143.255.255524,286
51209.144.0.0/13209.144.0.1 to 209.151.255.254209.151.255.255524,286
52209.152.0.0/13209.152.0.1 to 209.159.255.254209.159.255.255524,286
53209.160.0.0/13209.160.0.1 to 209.167.255.254209.167.255.255524,286
54209.168.0.0/13209.168.0.1 to 209.175.255.254209.175.255.255524,286
55209.176.0.0/13209.176.0.1 to 209.183.255.254209.183.255.255524,286
56209.184.0.0/13209.184.0.1 to 209.191.255.254209.191.255.255524,286
57209.192.0.0/13209.192.0.1 to 209.199.255.254209.199.255.255524,286
58209.200.0.0/13209.200.0.1 to 209.207.255.254209.207.255.255524,286
59209.208.0.0/13209.208.0.1 to 209.215.255.254209.215.255.255524,286
60209.216.0.0/13209.216.0.1 to 209.223.255.254209.223.255.255524,286
61209.224.0.0/13209.224.0.1 to 209.231.255.254209.231.255.255524,286
62209.232.0.0/13209.232.0.1 to 209.239.255.254209.239.255.255524,286
63209.240.0.0/13209.240.0.1 to 209.247.255.254209.247.255.255524,286
64209.248.0.0/13209.248.0.1 to 209.255.255.254209.255.255.255524,286
65210.0.0.0/13210.0.0.1 to 210.7.255.254210.7.255.255524,286
66210.8.0.0/13210.8.0.1 to 210.15.255.254210.15.255.255524,286
67210.16.0.0/13210.16.0.1 to 210.23.255.254210.23.255.255524,286
68210.24.0.0/13210.24.0.1 to 210.31.255.254210.31.255.255524,286
69210.32.0.0/13210.32.0.1 to 210.39.255.254210.39.255.255524,286
70210.40.0.0/13210.40.0.1 to 210.47.255.254210.47.255.255524,286
71210.48.0.0/13210.48.0.1 to 210.55.255.254210.55.255.255524,286
72210.56.0.0/13210.56.0.1 to 210.63.255.254210.63.255.255524,286
73210.64.0.0/13210.64.0.1 to 210.71.255.254210.71.255.255524,286
74210.72.0.0/13210.72.0.1 to 210.79.255.254210.79.255.255524,286
75210.80.0.0/13210.80.0.1 to 210.87.255.254210.87.255.255524,286
76210.88.0.0/13210.88.0.1 to 210.95.255.254210.95.255.255524,286
77210.96.0.0/13210.96.0.1 to 210.103.255.254210.103.255.255524,286
78210.104.0.0/13210.104.0.1 to 210.111.255.254210.111.255.255524,286
79210.112.0.0/13210.112.0.1 to 210.119.255.254210.119.255.255524,286
80210.120.0.0/13210.120.0.1 to 210.127.255.254210.127.255.255524,286
81210.128.0.0/13210.128.0.1 to 210.135.255.254210.135.255.255524,286
82210.136.0.0/13210.136.0.1 to 210.143.255.254210.143.255.255524,286
83210.144.0.0/13210.144.0.1 to 210.151.255.254210.151.255.255524,286
84210.152.0.0/13210.152.0.1 to 210.159.255.254210.159.255.255524,286
85210.160.0.0/13210.160.0.1 to 210.167.255.254210.167.255.255524,286
86210.168.0.0/13210.168.0.1 to 210.175.255.254210.175.255.255524,286
87210.176.0.0/13210.176.0.1 to 210.183.255.254210.183.255.255524,286
88210.184.0.0/13210.184.0.1 to 210.191.255.254210.191.255.255524,286
89210.192.0.0/13210.192.0.1 to 210.199.255.254210.199.255.255524,286
90210.200.0.0/13210.200.0.1 to 210.207.255.254210.207.255.255524,286
91210.208.0.0/13210.208.0.1 to 210.215.255.254210.215.255.255524,286
92210.216.0.0/13210.216.0.1 to 210.223.255.254210.223.255.255524,286
93210.224.0.0/13210.224.0.1 to 210.231.255.254210.231.255.255524,286
94210.232.0.0/13210.232.0.1 to 210.239.255.254210.239.255.255524,286
95210.240.0.0/13210.240.0.1 to 210.247.255.254210.247.255.255524,286
96210.248.0.0/13210.248.0.1 to 210.255.255.254210.255.255.255524,286
97211.0.0.0/13211.0.0.1 to 211.7.255.254211.7.255.255524,286
98211.8.0.0/13211.8.0.1 to 211.15.255.254211.15.255.255524,286
99211.16.0.0/13211.16.0.1 to 211.23.255.254211.23.255.255524,286
100211.24.0.0/13211.24.0.1 to 211.31.255.254211.31.255.255524,286
101211.32.0.0/13211.32.0.1 to 211.39.255.254211.39.255.255524,286
102211.40.0.0/13211.40.0.1 to 211.47.255.254211.47.255.255524,286
103211.48.0.0/13211.48.0.1 to 211.55.255.254211.55.255.255524,286
104211.56.0.0/13211.56.0.1 to 211.63.255.254211.63.255.255524,286
105211.64.0.0/13211.64.0.1 to 211.71.255.254211.71.255.255524,286
106211.72.0.0/13211.72.0.1 to 211.79.255.254211.79.255.255524,286
107211.80.0.0/13211.80.0.1 to 211.87.255.254211.87.255.255524,286
108211.88.0.0/13211.88.0.1 to 211.95.255.254211.95.255.255524,286
109211.96.0.0/13211.96.0.1 to 211.103.255.254211.103.255.255524,286
110211.104.0.0/13211.104.0.1 to 211.111.255.254211.111.255.255524,286
111211.112.0.0/13211.112.0.1 to 211.119.255.254211.119.255.255524,286
112211.120.0.0/13211.120.0.1 to 211.127.255.254211.127.255.255524,286
113211.128.0.0/13211.128.0.1 to 211.135.255.254211.135.255.255524,286
114211.136.0.0/13211.136.0.1 to 211.143.255.254211.143.255.255524,286
115211.144.0.0/13211.144.0.1 to 211.151.255.254211.151.255.255524,286
116211.152.0.0/13211.152.0.1 to 211.159.255.254211.159.255.255524,286
117211.160.0.0/13211.160.0.1 to 211.167.255.254211.167.255.255524,286
118211.168.0.0/13211.168.0.1 to 211.175.255.254211.175.255.255524,286
119211.176.0.0/13211.176.0.1 to 211.183.255.254211.183.255.255524,286
120211.184.0.0/13211.184.0.1 to 211.191.255.254211.191.255.255524,286
121211.192.0.0/13211.192.0.1 to 211.199.255.254211.199.255.255524,286
122211.200.0.0/13211.200.0.1 to 211.207.255.254211.207.255.255524,286
123211.208.0.0/13211.208.0.1 to 211.215.255.254211.215.255.255524,286
124211.216.0.0/13211.216.0.1 to 211.223.255.254211.223.255.255524,286
125211.224.0.0/13211.224.0.1 to 211.231.255.254211.231.255.255524,286
126211.232.0.0/13211.232.0.1 to 211.239.255.254211.239.255.255524,286
127211.240.0.0/13211.240.0.1 to 211.247.255.254211.247.255.255524,286
128211.248.0.0/13211.248.0.1 to 211.255.255.254211.255.255.255524,286
129212.0.0.0/13212.0.0.1 to 212.7.255.254212.7.255.255524,286
130212.8.0.0/13212.8.0.1 to 212.15.255.254212.15.255.255524,286
131212.16.0.0/13212.16.0.1 to 212.23.255.254212.23.255.255524,286
132212.24.0.0/13212.24.0.1 to 212.31.255.254212.31.255.255524,286
133212.32.0.0/13212.32.0.1 to 212.39.255.254212.39.255.255524,286
134212.40.0.0/13212.40.0.1 to 212.47.255.254212.47.255.255524,286
135212.48.0.0/13212.48.0.1 to 212.55.255.254212.55.255.255524,286
136212.56.0.0/13212.56.0.1 to 212.63.255.254212.63.255.255524,286
137212.64.0.0/13212.64.0.1 to 212.71.255.254212.71.255.255524,286
138212.72.0.0/13212.72.0.1 to 212.79.255.254212.79.255.255524,286
139212.80.0.0/13212.80.0.1 to 212.87.255.254212.87.255.255524,286
140212.88.0.0/13212.88.0.1 to 212.95.255.254212.95.255.255524,286
141212.96.0.0/13212.96.0.1 to 212.103.255.254212.103.255.255524,286
142212.104.0.0/13212.104.0.1 to 212.111.255.254212.111.255.255524,286
143212.112.0.0/13212.112.0.1 to 212.119.255.254212.119.255.255524,286
144212.120.0.0/13212.120.0.1 to 212.127.255.254212.127.255.255524,286
145212.128.0.0/13212.128.0.1 to 212.135.255.254212.135.255.255524,286
146212.136.0.0/13212.136.0.1 to 212.143.255.254212.143.255.255524,286
147212.144.0.0/13212.144.0.1 to 212.151.255.254212.151.255.255524,286
148212.152.0.0/13212.152.0.1 to 212.159.255.254212.159.255.255524,286
149212.160.0.0/13212.160.0.1 to 212.167.255.254212.167.255.255524,286
150212.168.0.0/13212.168.0.1 to 212.175.255.254212.175.255.255524,286
151212.176.0.0/13212.176.0.1 to 212.183.255.254212.183.255.255524,286
152212.184.0.0/13212.184.0.1 to 212.191.255.254212.191.255.255524,286
153212.192.0.0/13212.192.0.1 to 212.199.255.254212.199.255.255524,286
154212.200.0.0/13212.200.0.1 to 212.207.255.254212.207.255.255524,286
155212.208.0.0/13212.208.0.1 to 212.215.255.254212.215.255.255524,286
156212.216.0.0/13212.216.0.1 to 212.223.255.254212.223.255.255524,286
157212.224.0.0/13212.224.0.1 to 212.231.255.254212.231.255.255524,286
158212.232.0.0/13212.232.0.1 to 212.239.255.254212.239.255.255524,286
159212.240.0.0/13212.240.0.1 to 212.247.255.254212.247.255.255524,286
160212.248.0.0/13212.248.0.1 to 212.255.255.254212.255.255.255524,286
161213.0.0.0/13213.0.0.1 to 213.7.255.254213.7.255.255524,286
162213.8.0.0/13213.8.0.1 to 213.15.255.254213.15.255.255524,286
163213.16.0.0/13213.16.0.1 to 213.23.255.254213.23.255.255524,286
164213.24.0.0/13213.24.0.1 to 213.31.255.254213.31.255.255524,286
165213.32.0.0/13213.32.0.1 to 213.39.255.254213.39.255.255524,286
166213.40.0.0/13213.40.0.1 to 213.47.255.254213.47.255.255524,286
167213.48.0.0/13213.48.0.1 to 213.55.255.254213.55.255.255524,286
168213.56.0.0/13213.56.0.1 to 213.63.255.254213.63.255.255524,286
169213.64.0.0/13213.64.0.1 to 213.71.255.254213.71.255.255524,286
170213.72.0.0/13213.72.0.1 to 213.79.255.254213.79.255.255524,286
171213.80.0.0/13213.80.0.1 to 213.87.255.254213.87.255.255524,286
172213.88.0.0/13213.88.0.1 to 213.95.255.254213.95.255.255524,286
173213.96.0.0/13213.96.0.1 to 213.103.255.254213.103.255.255524,286
174213.104.0.0/13213.104.0.1 to 213.111.255.254213.111.255.255524,286
175213.112.0.0/13213.112.0.1 to 213.119.255.254213.119.255.255524,286
176213.120.0.0/13213.120.0.1 to 213.127.255.254213.127.255.255524,286
177213.128.0.0/13213.128.0.1 to 213.135.255.254213.135.255.255524,286
178213.136.0.0/13213.136.0.1 to 213.143.255.254213.143.255.255524,286
179213.144.0.0/13213.144.0.1 to 213.151.255.254213.151.255.255524,286
180213.152.0.0/13213.152.0.1 to 213.159.255.254213.159.255.255524,286
181213.160.0.0/13213.160.0.1 to 213.167.255.254213.167.255.255524,286
182213.168.0.0/13213.168.0.1 to 213.175.255.254213.175.255.255524,286
183213.176.0.0/13213.176.0.1 to 213.183.255.254213.183.255.255524,286
184213.184.0.0/13213.184.0.1 to 213.191.255.254213.191.255.255524,286
185213.192.0.0/13213.192.0.1 to 213.199.255.254213.199.255.255524,286
186213.200.0.0/13213.200.0.1 to 213.207.255.254213.207.255.255524,286
187213.208.0.0/13213.208.0.1 to 213.215.255.254213.215.255.255524,286
188213.216.0.0/13213.216.0.1 to 213.223.255.254213.223.255.255524,286
189213.224.0.0/13213.224.0.1 to 213.231.255.254213.231.255.255524,286
190213.232.0.0/13213.232.0.1 to 213.239.255.254213.239.255.255524,286
191213.240.0.0/13213.240.0.1 to 213.247.255.254213.247.255.255524,286
192213.248.0.0/13213.248.0.1 to 213.255.255.254213.255.255.255524,286
193214.0.0.0/13214.0.0.1 to 214.7.255.254214.7.255.255524,286
194214.8.0.0/13214.8.0.1 to 214.15.255.254214.15.255.255524,286
195214.16.0.0/13214.16.0.1 to 214.23.255.254214.23.255.255524,286
196214.24.0.0/13214.24.0.1 to 214.31.255.254214.31.255.255524,286
197214.32.0.0/13214.32.0.1 to 214.39.255.254214.39.255.255524,286
198214.40.0.0/13214.40.0.1 to 214.47.255.254214.47.255.255524,286
199214.48.0.0/13214.48.0.1 to 214.55.255.254214.55.255.255524,286
200214.56.0.0/13214.56.0.1 to 214.63.255.254214.63.255.255524,286
201214.64.0.0/13214.64.0.1 to 214.71.255.254214.71.255.255524,286
202214.72.0.0/13214.72.0.1 to 214.79.255.254214.79.255.255524,286
203214.80.0.0/13214.80.0.1 to 214.87.255.254214.87.255.255524,286
204214.88.0.0/13214.88.0.1 to 214.95.255.254214.95.255.255524,286
205214.96.0.0/13214.96.0.1 to 214.103.255.254214.103.255.255524,286
206214.104.0.0/13214.104.0.1 to 214.111.255.254214.111.255.255524,286
207214.112.0.0/13214.112.0.1 to 214.119.255.254214.119.255.255524,286
208214.120.0.0/13214.120.0.1 to 214.127.255.254214.127.255.255524,286
209214.128.0.0/13214.128.0.1 to 214.135.255.254214.135.255.255524,286
210214.136.0.0/13214.136.0.1 to 214.143.255.254214.143.255.255524,286
211214.144.0.0/13214.144.0.1 to 214.151.255.254214.151.255.255524,286
212214.152.0.0/13214.152.0.1 to 214.159.255.254214.159.255.255524,286
213214.160.0.0/13214.160.0.1 to 214.167.255.254214.167.255.255524,286
214214.168.0.0/13214.168.0.1 to 214.175.255.254214.175.255.255524,286
215214.176.0.0/13214.176.0.1 to 214.183.255.254214.183.255.255524,286
216214.184.0.0/13214.184.0.1 to 214.191.255.254214.191.255.255524,286
217214.192.0.0/13214.192.0.1 to 214.199.255.254214.199.255.255524,286
218214.200.0.0/13214.200.0.1 to 214.207.255.254214.207.255.255524,286
219214.208.0.0/13214.208.0.1 to 214.215.255.254214.215.255.255524,286
220214.216.0.0/13214.216.0.1 to 214.223.255.254214.223.255.255524,286
221214.224.0.0/13214.224.0.1 to 214.231.255.254214.231.255.255524,286
222214.232.0.0/13214.232.0.1 to 214.239.255.254214.239.255.255524,286
223214.240.0.0/13214.240.0.1 to 214.247.255.254214.247.255.255524,286
224214.248.0.0/13214.248.0.1 to 214.255.255.254214.255.255.255524,286
225215.0.0.0/13215.0.0.1 to 215.7.255.254215.7.255.255524,286
226215.8.0.0/13215.8.0.1 to 215.15.255.254215.15.255.255524,286
227215.16.0.0/13215.16.0.1 to 215.23.255.254215.23.255.255524,286
228215.24.0.0/13215.24.0.1 to 215.31.255.254215.31.255.255524,286
229215.32.0.0/13215.32.0.1 to 215.39.255.254215.39.255.255524,286
230215.40.0.0/13215.40.0.1 to 215.47.255.254215.47.255.255524,286
231215.48.0.0/13215.48.0.1 to 215.55.255.254215.55.255.255524,286
232215.56.0.0/13215.56.0.1 to 215.63.255.254215.63.255.255524,286
233215.64.0.0/13215.64.0.1 to 215.71.255.254215.71.255.255524,286
234215.72.0.0/13215.72.0.1 to 215.79.255.254215.79.255.255524,286
235215.80.0.0/13215.80.0.1 to 215.87.255.254215.87.255.255524,286
236215.88.0.0/13215.88.0.1 to 215.95.255.254215.95.255.255524,286
237215.96.0.0/13215.96.0.1 to 215.103.255.254215.103.255.255524,286
238215.104.0.0/13215.104.0.1 to 215.111.255.254215.111.255.255524,286
239215.112.0.0/13215.112.0.1 to 215.119.255.254215.119.255.255524,286
240215.120.0.0/13215.120.0.1 to 215.127.255.254215.127.255.255524,286
241215.128.0.0/13215.128.0.1 to 215.135.255.254215.135.255.255524,286
242215.136.0.0/13215.136.0.1 to 215.143.255.254215.143.255.255524,286
243215.144.0.0/13215.144.0.1 to 215.151.255.254215.151.255.255524,286
244215.152.0.0/13215.152.0.1 to 215.159.255.254215.159.255.255524,286
245215.160.0.0/13215.160.0.1 to 215.167.255.254215.167.255.255524,286
246215.168.0.0/13215.168.0.1 to 215.175.255.254215.175.255.255524,286
247215.176.0.0/13215.176.0.1 to 215.183.255.254215.183.255.255524,286
248215.184.0.0/13215.184.0.1 to 215.191.255.254215.191.255.255524,286
249215.192.0.0/13215.192.0.1 to 215.199.255.254215.199.255.255524,286
250215.200.0.0/13215.200.0.1 to 215.207.255.254215.207.255.255524,286
251215.208.0.0/13215.208.0.1 to 215.215.255.254215.215.255.255524,286
252215.216.0.0/13215.216.0.1 to 215.223.255.254215.223.255.255524,286
253215.224.0.0/13215.224.0.1 to 215.231.255.254215.231.255.255524,286
254215.232.0.0/13215.232.0.1 to 215.239.255.254215.239.255.255524,286
255215.240.0.0/13215.240.0.1 to 215.247.255.254215.247.255.255524,286
256215.248.0.0/13215.248.0.1 to 215.255.255.254215.255.255.255524,286

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.