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.

Network153.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
153.0.0.0
Broadcast address
153.255.255.255
First usable
153.0.0.1
Last usable
153.255.255.254
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
B (default /16)
As numbers
Hex 99000000 · Integer 2566914048 to 2583691263
Reverse DNS zone
153.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10011001..00000000.00000000.00000000153.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network10011001..00000000.00000000.00000000153.0.0.0
Broadcast10011001..11111111.11111111.11111111153.255.255.255
Split into smaller subnets/20
/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)

153.0.0.0/8 makes 4,096 subnets of /20; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1153.0.0.0/20153.0.0.1 to 153.0.15.254153.0.15.2554,094
2153.0.16.0/20153.0.16.1 to 153.0.31.254153.0.31.2554,094
3153.0.32.0/20153.0.32.1 to 153.0.47.254153.0.47.2554,094
4153.0.48.0/20153.0.48.1 to 153.0.63.254153.0.63.2554,094
5153.0.64.0/20153.0.64.1 to 153.0.79.254153.0.79.2554,094
6153.0.80.0/20153.0.80.1 to 153.0.95.254153.0.95.2554,094
7153.0.96.0/20153.0.96.1 to 153.0.111.254153.0.111.2554,094
8153.0.112.0/20153.0.112.1 to 153.0.127.254153.0.127.2554,094
9153.0.128.0/20153.0.128.1 to 153.0.143.254153.0.143.2554,094
10153.0.144.0/20153.0.144.1 to 153.0.159.254153.0.159.2554,094
11153.0.160.0/20153.0.160.1 to 153.0.175.254153.0.175.2554,094
12153.0.176.0/20153.0.176.1 to 153.0.191.254153.0.191.2554,094
13153.0.192.0/20153.0.192.1 to 153.0.207.254153.0.207.2554,094
14153.0.208.0/20153.0.208.1 to 153.0.223.254153.0.223.2554,094
15153.0.224.0/20153.0.224.1 to 153.0.239.254153.0.239.2554,094
16153.0.240.0/20153.0.240.1 to 153.0.255.254153.0.255.2554,094
17153.1.0.0/20153.1.0.1 to 153.1.15.254153.1.15.2554,094
18153.1.16.0/20153.1.16.1 to 153.1.31.254153.1.31.2554,094
19153.1.32.0/20153.1.32.1 to 153.1.47.254153.1.47.2554,094
20153.1.48.0/20153.1.48.1 to 153.1.63.254153.1.63.2554,094
21153.1.64.0/20153.1.64.1 to 153.1.79.254153.1.79.2554,094
22153.1.80.0/20153.1.80.1 to 153.1.95.254153.1.95.2554,094
23153.1.96.0/20153.1.96.1 to 153.1.111.254153.1.111.2554,094
24153.1.112.0/20153.1.112.1 to 153.1.127.254153.1.127.2554,094
25153.1.128.0/20153.1.128.1 to 153.1.143.254153.1.143.2554,094
26153.1.144.0/20153.1.144.1 to 153.1.159.254153.1.159.2554,094
27153.1.160.0/20153.1.160.1 to 153.1.175.254153.1.175.2554,094
28153.1.176.0/20153.1.176.1 to 153.1.191.254153.1.191.2554,094
29153.1.192.0/20153.1.192.1 to 153.1.207.254153.1.207.2554,094
30153.1.208.0/20153.1.208.1 to 153.1.223.254153.1.223.2554,094
31153.1.224.0/20153.1.224.1 to 153.1.239.254153.1.239.2554,094
32153.1.240.0/20153.1.240.1 to 153.1.255.254153.1.255.2554,094
33153.2.0.0/20153.2.0.1 to 153.2.15.254153.2.15.2554,094
34153.2.16.0/20153.2.16.1 to 153.2.31.254153.2.31.2554,094
35153.2.32.0/20153.2.32.1 to 153.2.47.254153.2.47.2554,094
36153.2.48.0/20153.2.48.1 to 153.2.63.254153.2.63.2554,094
37153.2.64.0/20153.2.64.1 to 153.2.79.254153.2.79.2554,094
38153.2.80.0/20153.2.80.1 to 153.2.95.254153.2.95.2554,094
39153.2.96.0/20153.2.96.1 to 153.2.111.254153.2.111.2554,094
40153.2.112.0/20153.2.112.1 to 153.2.127.254153.2.127.2554,094
41153.2.128.0/20153.2.128.1 to 153.2.143.254153.2.143.2554,094
42153.2.144.0/20153.2.144.1 to 153.2.159.254153.2.159.2554,094
43153.2.160.0/20153.2.160.1 to 153.2.175.254153.2.175.2554,094
44153.2.176.0/20153.2.176.1 to 153.2.191.254153.2.191.2554,094
45153.2.192.0/20153.2.192.1 to 153.2.207.254153.2.207.2554,094
46153.2.208.0/20153.2.208.1 to 153.2.223.254153.2.223.2554,094
47153.2.224.0/20153.2.224.1 to 153.2.239.254153.2.239.2554,094
48153.2.240.0/20153.2.240.1 to 153.2.255.254153.2.255.2554,094
49153.3.0.0/20153.3.0.1 to 153.3.15.254153.3.15.2554,094
50153.3.16.0/20153.3.16.1 to 153.3.31.254153.3.31.2554,094
51153.3.32.0/20153.3.32.1 to 153.3.47.254153.3.47.2554,094
52153.3.48.0/20153.3.48.1 to 153.3.63.254153.3.63.2554,094
53153.3.64.0/20153.3.64.1 to 153.3.79.254153.3.79.2554,094
54153.3.80.0/20153.3.80.1 to 153.3.95.254153.3.95.2554,094
55153.3.96.0/20153.3.96.1 to 153.3.111.254153.3.111.2554,094
56153.3.112.0/20153.3.112.1 to 153.3.127.254153.3.127.2554,094
57153.3.128.0/20153.3.128.1 to 153.3.143.254153.3.143.2554,094
58153.3.144.0/20153.3.144.1 to 153.3.159.254153.3.159.2554,094
59153.3.160.0/20153.3.160.1 to 153.3.175.254153.3.175.2554,094
60153.3.176.0/20153.3.176.1 to 153.3.191.254153.3.191.2554,094
61153.3.192.0/20153.3.192.1 to 153.3.207.254153.3.207.2554,094
62153.3.208.0/20153.3.208.1 to 153.3.223.254153.3.223.2554,094
63153.3.224.0/20153.3.224.1 to 153.3.239.254153.3.239.2554,094
64153.3.240.0/20153.3.240.1 to 153.3.255.254153.3.255.2554,094
65153.4.0.0/20153.4.0.1 to 153.4.15.254153.4.15.2554,094
66153.4.16.0/20153.4.16.1 to 153.4.31.254153.4.31.2554,094
67153.4.32.0/20153.4.32.1 to 153.4.47.254153.4.47.2554,094
68153.4.48.0/20153.4.48.1 to 153.4.63.254153.4.63.2554,094
69153.4.64.0/20153.4.64.1 to 153.4.79.254153.4.79.2554,094
70153.4.80.0/20153.4.80.1 to 153.4.95.254153.4.95.2554,094
71153.4.96.0/20153.4.96.1 to 153.4.111.254153.4.111.2554,094
72153.4.112.0/20153.4.112.1 to 153.4.127.254153.4.127.2554,094
73153.4.128.0/20153.4.128.1 to 153.4.143.254153.4.143.2554,094
74153.4.144.0/20153.4.144.1 to 153.4.159.254153.4.159.2554,094
75153.4.160.0/20153.4.160.1 to 153.4.175.254153.4.175.2554,094
76153.4.176.0/20153.4.176.1 to 153.4.191.254153.4.191.2554,094
77153.4.192.0/20153.4.192.1 to 153.4.207.254153.4.207.2554,094
78153.4.208.0/20153.4.208.1 to 153.4.223.254153.4.223.2554,094
79153.4.224.0/20153.4.224.1 to 153.4.239.254153.4.239.2554,094
80153.4.240.0/20153.4.240.1 to 153.4.255.254153.4.255.2554,094
81153.5.0.0/20153.5.0.1 to 153.5.15.254153.5.15.2554,094
82153.5.16.0/20153.5.16.1 to 153.5.31.254153.5.31.2554,094
83153.5.32.0/20153.5.32.1 to 153.5.47.254153.5.47.2554,094
84153.5.48.0/20153.5.48.1 to 153.5.63.254153.5.63.2554,094
85153.5.64.0/20153.5.64.1 to 153.5.79.254153.5.79.2554,094
86153.5.80.0/20153.5.80.1 to 153.5.95.254153.5.95.2554,094
87153.5.96.0/20153.5.96.1 to 153.5.111.254153.5.111.2554,094
88153.5.112.0/20153.5.112.1 to 153.5.127.254153.5.127.2554,094
89153.5.128.0/20153.5.128.1 to 153.5.143.254153.5.143.2554,094
90153.5.144.0/20153.5.144.1 to 153.5.159.254153.5.159.2554,094
91153.5.160.0/20153.5.160.1 to 153.5.175.254153.5.175.2554,094
92153.5.176.0/20153.5.176.1 to 153.5.191.254153.5.191.2554,094
93153.5.192.0/20153.5.192.1 to 153.5.207.254153.5.207.2554,094
94153.5.208.0/20153.5.208.1 to 153.5.223.254153.5.223.2554,094
95153.5.224.0/20153.5.224.1 to 153.5.239.254153.5.239.2554,094
96153.5.240.0/20153.5.240.1 to 153.5.255.254153.5.255.2554,094
97153.6.0.0/20153.6.0.1 to 153.6.15.254153.6.15.2554,094
98153.6.16.0/20153.6.16.1 to 153.6.31.254153.6.31.2554,094
99153.6.32.0/20153.6.32.1 to 153.6.47.254153.6.47.2554,094
100153.6.48.0/20153.6.48.1 to 153.6.63.254153.6.63.2554,094
101153.6.64.0/20153.6.64.1 to 153.6.79.254153.6.79.2554,094
102153.6.80.0/20153.6.80.1 to 153.6.95.254153.6.95.2554,094
103153.6.96.0/20153.6.96.1 to 153.6.111.254153.6.111.2554,094
104153.6.112.0/20153.6.112.1 to 153.6.127.254153.6.127.2554,094
105153.6.128.0/20153.6.128.1 to 153.6.143.254153.6.143.2554,094
106153.6.144.0/20153.6.144.1 to 153.6.159.254153.6.159.2554,094
107153.6.160.0/20153.6.160.1 to 153.6.175.254153.6.175.2554,094
108153.6.176.0/20153.6.176.1 to 153.6.191.254153.6.191.2554,094
109153.6.192.0/20153.6.192.1 to 153.6.207.254153.6.207.2554,094
110153.6.208.0/20153.6.208.1 to 153.6.223.254153.6.223.2554,094
111153.6.224.0/20153.6.224.1 to 153.6.239.254153.6.239.2554,094
112153.6.240.0/20153.6.240.1 to 153.6.255.254153.6.255.2554,094
113153.7.0.0/20153.7.0.1 to 153.7.15.254153.7.15.2554,094
114153.7.16.0/20153.7.16.1 to 153.7.31.254153.7.31.2554,094
115153.7.32.0/20153.7.32.1 to 153.7.47.254153.7.47.2554,094
116153.7.48.0/20153.7.48.1 to 153.7.63.254153.7.63.2554,094
117153.7.64.0/20153.7.64.1 to 153.7.79.254153.7.79.2554,094
118153.7.80.0/20153.7.80.1 to 153.7.95.254153.7.95.2554,094
119153.7.96.0/20153.7.96.1 to 153.7.111.254153.7.111.2554,094
120153.7.112.0/20153.7.112.1 to 153.7.127.254153.7.127.2554,094
121153.7.128.0/20153.7.128.1 to 153.7.143.254153.7.143.2554,094
122153.7.144.0/20153.7.144.1 to 153.7.159.254153.7.159.2554,094
123153.7.160.0/20153.7.160.1 to 153.7.175.254153.7.175.2554,094
124153.7.176.0/20153.7.176.1 to 153.7.191.254153.7.191.2554,094
125153.7.192.0/20153.7.192.1 to 153.7.207.254153.7.207.2554,094
126153.7.208.0/20153.7.208.1 to 153.7.223.254153.7.223.2554,094
127153.7.224.0/20153.7.224.1 to 153.7.239.254153.7.239.2554,094
128153.7.240.0/20153.7.240.1 to 153.7.255.254153.7.255.2554,094
129153.8.0.0/20153.8.0.1 to 153.8.15.254153.8.15.2554,094
130153.8.16.0/20153.8.16.1 to 153.8.31.254153.8.31.2554,094
131153.8.32.0/20153.8.32.1 to 153.8.47.254153.8.47.2554,094
132153.8.48.0/20153.8.48.1 to 153.8.63.254153.8.63.2554,094
133153.8.64.0/20153.8.64.1 to 153.8.79.254153.8.79.2554,094
134153.8.80.0/20153.8.80.1 to 153.8.95.254153.8.95.2554,094
135153.8.96.0/20153.8.96.1 to 153.8.111.254153.8.111.2554,094
136153.8.112.0/20153.8.112.1 to 153.8.127.254153.8.127.2554,094
137153.8.128.0/20153.8.128.1 to 153.8.143.254153.8.143.2554,094
138153.8.144.0/20153.8.144.1 to 153.8.159.254153.8.159.2554,094
139153.8.160.0/20153.8.160.1 to 153.8.175.254153.8.175.2554,094
140153.8.176.0/20153.8.176.1 to 153.8.191.254153.8.191.2554,094
141153.8.192.0/20153.8.192.1 to 153.8.207.254153.8.207.2554,094
142153.8.208.0/20153.8.208.1 to 153.8.223.254153.8.223.2554,094
143153.8.224.0/20153.8.224.1 to 153.8.239.254153.8.239.2554,094
144153.8.240.0/20153.8.240.1 to 153.8.255.254153.8.255.2554,094
145153.9.0.0/20153.9.0.1 to 153.9.15.254153.9.15.2554,094
146153.9.16.0/20153.9.16.1 to 153.9.31.254153.9.31.2554,094
147153.9.32.0/20153.9.32.1 to 153.9.47.254153.9.47.2554,094
148153.9.48.0/20153.9.48.1 to 153.9.63.254153.9.63.2554,094
149153.9.64.0/20153.9.64.1 to 153.9.79.254153.9.79.2554,094
150153.9.80.0/20153.9.80.1 to 153.9.95.254153.9.95.2554,094
151153.9.96.0/20153.9.96.1 to 153.9.111.254153.9.111.2554,094
152153.9.112.0/20153.9.112.1 to 153.9.127.254153.9.127.2554,094
153153.9.128.0/20153.9.128.1 to 153.9.143.254153.9.143.2554,094
154153.9.144.0/20153.9.144.1 to 153.9.159.254153.9.159.2554,094
155153.9.160.0/20153.9.160.1 to 153.9.175.254153.9.175.2554,094
156153.9.176.0/20153.9.176.1 to 153.9.191.254153.9.191.2554,094
157153.9.192.0/20153.9.192.1 to 153.9.207.254153.9.207.2554,094
158153.9.208.0/20153.9.208.1 to 153.9.223.254153.9.223.2554,094
159153.9.224.0/20153.9.224.1 to 153.9.239.254153.9.239.2554,094
160153.9.240.0/20153.9.240.1 to 153.9.255.254153.9.255.2554,094
161153.10.0.0/20153.10.0.1 to 153.10.15.254153.10.15.2554,094
162153.10.16.0/20153.10.16.1 to 153.10.31.254153.10.31.2554,094
163153.10.32.0/20153.10.32.1 to 153.10.47.254153.10.47.2554,094
164153.10.48.0/20153.10.48.1 to 153.10.63.254153.10.63.2554,094
165153.10.64.0/20153.10.64.1 to 153.10.79.254153.10.79.2554,094
166153.10.80.0/20153.10.80.1 to 153.10.95.254153.10.95.2554,094
167153.10.96.0/20153.10.96.1 to 153.10.111.254153.10.111.2554,094
168153.10.112.0/20153.10.112.1 to 153.10.127.254153.10.127.2554,094
169153.10.128.0/20153.10.128.1 to 153.10.143.254153.10.143.2554,094
170153.10.144.0/20153.10.144.1 to 153.10.159.254153.10.159.2554,094
171153.10.160.0/20153.10.160.1 to 153.10.175.254153.10.175.2554,094
172153.10.176.0/20153.10.176.1 to 153.10.191.254153.10.191.2554,094
173153.10.192.0/20153.10.192.1 to 153.10.207.254153.10.207.2554,094
174153.10.208.0/20153.10.208.1 to 153.10.223.254153.10.223.2554,094
175153.10.224.0/20153.10.224.1 to 153.10.239.254153.10.239.2554,094
176153.10.240.0/20153.10.240.1 to 153.10.255.254153.10.255.2554,094
177153.11.0.0/20153.11.0.1 to 153.11.15.254153.11.15.2554,094
178153.11.16.0/20153.11.16.1 to 153.11.31.254153.11.31.2554,094
179153.11.32.0/20153.11.32.1 to 153.11.47.254153.11.47.2554,094
180153.11.48.0/20153.11.48.1 to 153.11.63.254153.11.63.2554,094
181153.11.64.0/20153.11.64.1 to 153.11.79.254153.11.79.2554,094
182153.11.80.0/20153.11.80.1 to 153.11.95.254153.11.95.2554,094
183153.11.96.0/20153.11.96.1 to 153.11.111.254153.11.111.2554,094
184153.11.112.0/20153.11.112.1 to 153.11.127.254153.11.127.2554,094
185153.11.128.0/20153.11.128.1 to 153.11.143.254153.11.143.2554,094
186153.11.144.0/20153.11.144.1 to 153.11.159.254153.11.159.2554,094
187153.11.160.0/20153.11.160.1 to 153.11.175.254153.11.175.2554,094
188153.11.176.0/20153.11.176.1 to 153.11.191.254153.11.191.2554,094
189153.11.192.0/20153.11.192.1 to 153.11.207.254153.11.207.2554,094
190153.11.208.0/20153.11.208.1 to 153.11.223.254153.11.223.2554,094
191153.11.224.0/20153.11.224.1 to 153.11.239.254153.11.239.2554,094
192153.11.240.0/20153.11.240.1 to 153.11.255.254153.11.255.2554,094
193153.12.0.0/20153.12.0.1 to 153.12.15.254153.12.15.2554,094
194153.12.16.0/20153.12.16.1 to 153.12.31.254153.12.31.2554,094
195153.12.32.0/20153.12.32.1 to 153.12.47.254153.12.47.2554,094
196153.12.48.0/20153.12.48.1 to 153.12.63.254153.12.63.2554,094
197153.12.64.0/20153.12.64.1 to 153.12.79.254153.12.79.2554,094
198153.12.80.0/20153.12.80.1 to 153.12.95.254153.12.95.2554,094
199153.12.96.0/20153.12.96.1 to 153.12.111.254153.12.111.2554,094
200153.12.112.0/20153.12.112.1 to 153.12.127.254153.12.127.2554,094
201153.12.128.0/20153.12.128.1 to 153.12.143.254153.12.143.2554,094
202153.12.144.0/20153.12.144.1 to 153.12.159.254153.12.159.2554,094
203153.12.160.0/20153.12.160.1 to 153.12.175.254153.12.175.2554,094
204153.12.176.0/20153.12.176.1 to 153.12.191.254153.12.191.2554,094
205153.12.192.0/20153.12.192.1 to 153.12.207.254153.12.207.2554,094
206153.12.208.0/20153.12.208.1 to 153.12.223.254153.12.223.2554,094
207153.12.224.0/20153.12.224.1 to 153.12.239.254153.12.239.2554,094
208153.12.240.0/20153.12.240.1 to 153.12.255.254153.12.255.2554,094
209153.13.0.0/20153.13.0.1 to 153.13.15.254153.13.15.2554,094
210153.13.16.0/20153.13.16.1 to 153.13.31.254153.13.31.2554,094
211153.13.32.0/20153.13.32.1 to 153.13.47.254153.13.47.2554,094
212153.13.48.0/20153.13.48.1 to 153.13.63.254153.13.63.2554,094
213153.13.64.0/20153.13.64.1 to 153.13.79.254153.13.79.2554,094
214153.13.80.0/20153.13.80.1 to 153.13.95.254153.13.95.2554,094
215153.13.96.0/20153.13.96.1 to 153.13.111.254153.13.111.2554,094
216153.13.112.0/20153.13.112.1 to 153.13.127.254153.13.127.2554,094
217153.13.128.0/20153.13.128.1 to 153.13.143.254153.13.143.2554,094
218153.13.144.0/20153.13.144.1 to 153.13.159.254153.13.159.2554,094
219153.13.160.0/20153.13.160.1 to 153.13.175.254153.13.175.2554,094
220153.13.176.0/20153.13.176.1 to 153.13.191.254153.13.191.2554,094
221153.13.192.0/20153.13.192.1 to 153.13.207.254153.13.207.2554,094
222153.13.208.0/20153.13.208.1 to 153.13.223.254153.13.223.2554,094
223153.13.224.0/20153.13.224.1 to 153.13.239.254153.13.239.2554,094
224153.13.240.0/20153.13.240.1 to 153.13.255.254153.13.255.2554,094
225153.14.0.0/20153.14.0.1 to 153.14.15.254153.14.15.2554,094
226153.14.16.0/20153.14.16.1 to 153.14.31.254153.14.31.2554,094
227153.14.32.0/20153.14.32.1 to 153.14.47.254153.14.47.2554,094
228153.14.48.0/20153.14.48.1 to 153.14.63.254153.14.63.2554,094
229153.14.64.0/20153.14.64.1 to 153.14.79.254153.14.79.2554,094
230153.14.80.0/20153.14.80.1 to 153.14.95.254153.14.95.2554,094
231153.14.96.0/20153.14.96.1 to 153.14.111.254153.14.111.2554,094
232153.14.112.0/20153.14.112.1 to 153.14.127.254153.14.127.2554,094
233153.14.128.0/20153.14.128.1 to 153.14.143.254153.14.143.2554,094
234153.14.144.0/20153.14.144.1 to 153.14.159.254153.14.159.2554,094
235153.14.160.0/20153.14.160.1 to 153.14.175.254153.14.175.2554,094
236153.14.176.0/20153.14.176.1 to 153.14.191.254153.14.191.2554,094
237153.14.192.0/20153.14.192.1 to 153.14.207.254153.14.207.2554,094
238153.14.208.0/20153.14.208.1 to 153.14.223.254153.14.223.2554,094
239153.14.224.0/20153.14.224.1 to 153.14.239.254153.14.239.2554,094
240153.14.240.0/20153.14.240.1 to 153.14.255.254153.14.255.2554,094
241153.15.0.0/20153.15.0.1 to 153.15.15.254153.15.15.2554,094
242153.15.16.0/20153.15.16.1 to 153.15.31.254153.15.31.2554,094
243153.15.32.0/20153.15.32.1 to 153.15.47.254153.15.47.2554,094
244153.15.48.0/20153.15.48.1 to 153.15.63.254153.15.63.2554,094
245153.15.64.0/20153.15.64.1 to 153.15.79.254153.15.79.2554,094
246153.15.80.0/20153.15.80.1 to 153.15.95.254153.15.95.2554,094
247153.15.96.0/20153.15.96.1 to 153.15.111.254153.15.111.2554,094
248153.15.112.0/20153.15.112.1 to 153.15.127.254153.15.127.2554,094
249153.15.128.0/20153.15.128.1 to 153.15.143.254153.15.143.2554,094
250153.15.144.0/20153.15.144.1 to 153.15.159.254153.15.159.2554,094
251153.15.160.0/20153.15.160.1 to 153.15.175.254153.15.175.2554,094
252153.15.176.0/20153.15.176.1 to 153.15.191.254153.15.191.2554,094
253153.15.192.0/20153.15.192.1 to 153.15.207.254153.15.207.2554,094
254153.15.208.0/20153.15.208.1 to 153.15.223.254153.15.223.2554,094
255153.15.224.0/20153.15.224.1 to 153.15.239.254153.15.239.2554,094
256153.15.240.0/20153.15.240.1 to 153.15.255.254153.15.255.2554,094

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.