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.

Network175.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
175.0.0.0
Broadcast address
175.127.255.255
First usable
175.0.0.1
Last usable
175.127.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Public public
Old class
B (default /16)
As numbers
Hex AF000000 · Integer 2936012800 to 2944401407
Reverse DNS zones
0.175.in-addr.arpa
1.175.in-addr.arpa
2.175.in-addr.arpa
3.175.in-addr.arpa
4.175.in-addr.arpa
5.175.in-addr.arpa
6.175.in-addr.arpa
7.175.in-addr.arpa
8.175.in-addr.arpa
9.175.in-addr.arpa
10.175.in-addr.arpa
11.175.in-addr.arpa
12.175.in-addr.arpa
13.175.in-addr.arpa
14.175.in-addr.arpa
15.175.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10101111.00000000.00000000.00000000175.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network10101111.00000000.00000000.00000000175.0.0.0
Broadcast10101111.01111111.11111111.11111111175.127.255.255
Split into smaller subnets/18
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

175.0.0.0/9 makes 512 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1175.0.0.0/18175.0.0.1 to 175.0.63.254175.0.63.25516,382
2175.0.64.0/18175.0.64.1 to 175.0.127.254175.0.127.25516,382
3175.0.128.0/18175.0.128.1 to 175.0.191.254175.0.191.25516,382
4175.0.192.0/18175.0.192.1 to 175.0.255.254175.0.255.25516,382
5175.1.0.0/18175.1.0.1 to 175.1.63.254175.1.63.25516,382
6175.1.64.0/18175.1.64.1 to 175.1.127.254175.1.127.25516,382
7175.1.128.0/18175.1.128.1 to 175.1.191.254175.1.191.25516,382
8175.1.192.0/18175.1.192.1 to 175.1.255.254175.1.255.25516,382
9175.2.0.0/18175.2.0.1 to 175.2.63.254175.2.63.25516,382
10175.2.64.0/18175.2.64.1 to 175.2.127.254175.2.127.25516,382
11175.2.128.0/18175.2.128.1 to 175.2.191.254175.2.191.25516,382
12175.2.192.0/18175.2.192.1 to 175.2.255.254175.2.255.25516,382
13175.3.0.0/18175.3.0.1 to 175.3.63.254175.3.63.25516,382
14175.3.64.0/18175.3.64.1 to 175.3.127.254175.3.127.25516,382
15175.3.128.0/18175.3.128.1 to 175.3.191.254175.3.191.25516,382
16175.3.192.0/18175.3.192.1 to 175.3.255.254175.3.255.25516,382
17175.4.0.0/18175.4.0.1 to 175.4.63.254175.4.63.25516,382
18175.4.64.0/18175.4.64.1 to 175.4.127.254175.4.127.25516,382
19175.4.128.0/18175.4.128.1 to 175.4.191.254175.4.191.25516,382
20175.4.192.0/18175.4.192.1 to 175.4.255.254175.4.255.25516,382
21175.5.0.0/18175.5.0.1 to 175.5.63.254175.5.63.25516,382
22175.5.64.0/18175.5.64.1 to 175.5.127.254175.5.127.25516,382
23175.5.128.0/18175.5.128.1 to 175.5.191.254175.5.191.25516,382
24175.5.192.0/18175.5.192.1 to 175.5.255.254175.5.255.25516,382
25175.6.0.0/18175.6.0.1 to 175.6.63.254175.6.63.25516,382
26175.6.64.0/18175.6.64.1 to 175.6.127.254175.6.127.25516,382
27175.6.128.0/18175.6.128.1 to 175.6.191.254175.6.191.25516,382
28175.6.192.0/18175.6.192.1 to 175.6.255.254175.6.255.25516,382
29175.7.0.0/18175.7.0.1 to 175.7.63.254175.7.63.25516,382
30175.7.64.0/18175.7.64.1 to 175.7.127.254175.7.127.25516,382
31175.7.128.0/18175.7.128.1 to 175.7.191.254175.7.191.25516,382
32175.7.192.0/18175.7.192.1 to 175.7.255.254175.7.255.25516,382
33175.8.0.0/18175.8.0.1 to 175.8.63.254175.8.63.25516,382
34175.8.64.0/18175.8.64.1 to 175.8.127.254175.8.127.25516,382
35175.8.128.0/18175.8.128.1 to 175.8.191.254175.8.191.25516,382
36175.8.192.0/18175.8.192.1 to 175.8.255.254175.8.255.25516,382
37175.9.0.0/18175.9.0.1 to 175.9.63.254175.9.63.25516,382
38175.9.64.0/18175.9.64.1 to 175.9.127.254175.9.127.25516,382
39175.9.128.0/18175.9.128.1 to 175.9.191.254175.9.191.25516,382
40175.9.192.0/18175.9.192.1 to 175.9.255.254175.9.255.25516,382
41175.10.0.0/18175.10.0.1 to 175.10.63.254175.10.63.25516,382
42175.10.64.0/18175.10.64.1 to 175.10.127.254175.10.127.25516,382
43175.10.128.0/18175.10.128.1 to 175.10.191.254175.10.191.25516,382
44175.10.192.0/18175.10.192.1 to 175.10.255.254175.10.255.25516,382
45175.11.0.0/18175.11.0.1 to 175.11.63.254175.11.63.25516,382
46175.11.64.0/18175.11.64.1 to 175.11.127.254175.11.127.25516,382
47175.11.128.0/18175.11.128.1 to 175.11.191.254175.11.191.25516,382
48175.11.192.0/18175.11.192.1 to 175.11.255.254175.11.255.25516,382
49175.12.0.0/18175.12.0.1 to 175.12.63.254175.12.63.25516,382
50175.12.64.0/18175.12.64.1 to 175.12.127.254175.12.127.25516,382
51175.12.128.0/18175.12.128.1 to 175.12.191.254175.12.191.25516,382
52175.12.192.0/18175.12.192.1 to 175.12.255.254175.12.255.25516,382
53175.13.0.0/18175.13.0.1 to 175.13.63.254175.13.63.25516,382
54175.13.64.0/18175.13.64.1 to 175.13.127.254175.13.127.25516,382
55175.13.128.0/18175.13.128.1 to 175.13.191.254175.13.191.25516,382
56175.13.192.0/18175.13.192.1 to 175.13.255.254175.13.255.25516,382
57175.14.0.0/18175.14.0.1 to 175.14.63.254175.14.63.25516,382
58175.14.64.0/18175.14.64.1 to 175.14.127.254175.14.127.25516,382
59175.14.128.0/18175.14.128.1 to 175.14.191.254175.14.191.25516,382
60175.14.192.0/18175.14.192.1 to 175.14.255.254175.14.255.25516,382
61175.15.0.0/18175.15.0.1 to 175.15.63.254175.15.63.25516,382
62175.15.64.0/18175.15.64.1 to 175.15.127.254175.15.127.25516,382
63175.15.128.0/18175.15.128.1 to 175.15.191.254175.15.191.25516,382
64175.15.192.0/18175.15.192.1 to 175.15.255.254175.15.255.25516,382
65175.16.0.0/18175.16.0.1 to 175.16.63.254175.16.63.25516,382
66175.16.64.0/18175.16.64.1 to 175.16.127.254175.16.127.25516,382
67175.16.128.0/18175.16.128.1 to 175.16.191.254175.16.191.25516,382
68175.16.192.0/18175.16.192.1 to 175.16.255.254175.16.255.25516,382
69175.17.0.0/18175.17.0.1 to 175.17.63.254175.17.63.25516,382
70175.17.64.0/18175.17.64.1 to 175.17.127.254175.17.127.25516,382
71175.17.128.0/18175.17.128.1 to 175.17.191.254175.17.191.25516,382
72175.17.192.0/18175.17.192.1 to 175.17.255.254175.17.255.25516,382
73175.18.0.0/18175.18.0.1 to 175.18.63.254175.18.63.25516,382
74175.18.64.0/18175.18.64.1 to 175.18.127.254175.18.127.25516,382
75175.18.128.0/18175.18.128.1 to 175.18.191.254175.18.191.25516,382
76175.18.192.0/18175.18.192.1 to 175.18.255.254175.18.255.25516,382
77175.19.0.0/18175.19.0.1 to 175.19.63.254175.19.63.25516,382
78175.19.64.0/18175.19.64.1 to 175.19.127.254175.19.127.25516,382
79175.19.128.0/18175.19.128.1 to 175.19.191.254175.19.191.25516,382
80175.19.192.0/18175.19.192.1 to 175.19.255.254175.19.255.25516,382
81175.20.0.0/18175.20.0.1 to 175.20.63.254175.20.63.25516,382
82175.20.64.0/18175.20.64.1 to 175.20.127.254175.20.127.25516,382
83175.20.128.0/18175.20.128.1 to 175.20.191.254175.20.191.25516,382
84175.20.192.0/18175.20.192.1 to 175.20.255.254175.20.255.25516,382
85175.21.0.0/18175.21.0.1 to 175.21.63.254175.21.63.25516,382
86175.21.64.0/18175.21.64.1 to 175.21.127.254175.21.127.25516,382
87175.21.128.0/18175.21.128.1 to 175.21.191.254175.21.191.25516,382
88175.21.192.0/18175.21.192.1 to 175.21.255.254175.21.255.25516,382
89175.22.0.0/18175.22.0.1 to 175.22.63.254175.22.63.25516,382
90175.22.64.0/18175.22.64.1 to 175.22.127.254175.22.127.25516,382
91175.22.128.0/18175.22.128.1 to 175.22.191.254175.22.191.25516,382
92175.22.192.0/18175.22.192.1 to 175.22.255.254175.22.255.25516,382
93175.23.0.0/18175.23.0.1 to 175.23.63.254175.23.63.25516,382
94175.23.64.0/18175.23.64.1 to 175.23.127.254175.23.127.25516,382
95175.23.128.0/18175.23.128.1 to 175.23.191.254175.23.191.25516,382
96175.23.192.0/18175.23.192.1 to 175.23.255.254175.23.255.25516,382
97175.24.0.0/18175.24.0.1 to 175.24.63.254175.24.63.25516,382
98175.24.64.0/18175.24.64.1 to 175.24.127.254175.24.127.25516,382
99175.24.128.0/18175.24.128.1 to 175.24.191.254175.24.191.25516,382
100175.24.192.0/18175.24.192.1 to 175.24.255.254175.24.255.25516,382
101175.25.0.0/18175.25.0.1 to 175.25.63.254175.25.63.25516,382
102175.25.64.0/18175.25.64.1 to 175.25.127.254175.25.127.25516,382
103175.25.128.0/18175.25.128.1 to 175.25.191.254175.25.191.25516,382
104175.25.192.0/18175.25.192.1 to 175.25.255.254175.25.255.25516,382
105175.26.0.0/18175.26.0.1 to 175.26.63.254175.26.63.25516,382
106175.26.64.0/18175.26.64.1 to 175.26.127.254175.26.127.25516,382
107175.26.128.0/18175.26.128.1 to 175.26.191.254175.26.191.25516,382
108175.26.192.0/18175.26.192.1 to 175.26.255.254175.26.255.25516,382
109175.27.0.0/18175.27.0.1 to 175.27.63.254175.27.63.25516,382
110175.27.64.0/18175.27.64.1 to 175.27.127.254175.27.127.25516,382
111175.27.128.0/18175.27.128.1 to 175.27.191.254175.27.191.25516,382
112175.27.192.0/18175.27.192.1 to 175.27.255.254175.27.255.25516,382
113175.28.0.0/18175.28.0.1 to 175.28.63.254175.28.63.25516,382
114175.28.64.0/18175.28.64.1 to 175.28.127.254175.28.127.25516,382
115175.28.128.0/18175.28.128.1 to 175.28.191.254175.28.191.25516,382
116175.28.192.0/18175.28.192.1 to 175.28.255.254175.28.255.25516,382
117175.29.0.0/18175.29.0.1 to 175.29.63.254175.29.63.25516,382
118175.29.64.0/18175.29.64.1 to 175.29.127.254175.29.127.25516,382
119175.29.128.0/18175.29.128.1 to 175.29.191.254175.29.191.25516,382
120175.29.192.0/18175.29.192.1 to 175.29.255.254175.29.255.25516,382
121175.30.0.0/18175.30.0.1 to 175.30.63.254175.30.63.25516,382
122175.30.64.0/18175.30.64.1 to 175.30.127.254175.30.127.25516,382
123175.30.128.0/18175.30.128.1 to 175.30.191.254175.30.191.25516,382
124175.30.192.0/18175.30.192.1 to 175.30.255.254175.30.255.25516,382
125175.31.0.0/18175.31.0.1 to 175.31.63.254175.31.63.25516,382
126175.31.64.0/18175.31.64.1 to 175.31.127.254175.31.127.25516,382
127175.31.128.0/18175.31.128.1 to 175.31.191.254175.31.191.25516,382
128175.31.192.0/18175.31.192.1 to 175.31.255.254175.31.255.25516,382
129175.32.0.0/18175.32.0.1 to 175.32.63.254175.32.63.25516,382
130175.32.64.0/18175.32.64.1 to 175.32.127.254175.32.127.25516,382
131175.32.128.0/18175.32.128.1 to 175.32.191.254175.32.191.25516,382
132175.32.192.0/18175.32.192.1 to 175.32.255.254175.32.255.25516,382
133175.33.0.0/18175.33.0.1 to 175.33.63.254175.33.63.25516,382
134175.33.64.0/18175.33.64.1 to 175.33.127.254175.33.127.25516,382
135175.33.128.0/18175.33.128.1 to 175.33.191.254175.33.191.25516,382
136175.33.192.0/18175.33.192.1 to 175.33.255.254175.33.255.25516,382
137175.34.0.0/18175.34.0.1 to 175.34.63.254175.34.63.25516,382
138175.34.64.0/18175.34.64.1 to 175.34.127.254175.34.127.25516,382
139175.34.128.0/18175.34.128.1 to 175.34.191.254175.34.191.25516,382
140175.34.192.0/18175.34.192.1 to 175.34.255.254175.34.255.25516,382
141175.35.0.0/18175.35.0.1 to 175.35.63.254175.35.63.25516,382
142175.35.64.0/18175.35.64.1 to 175.35.127.254175.35.127.25516,382
143175.35.128.0/18175.35.128.1 to 175.35.191.254175.35.191.25516,382
144175.35.192.0/18175.35.192.1 to 175.35.255.254175.35.255.25516,382
145175.36.0.0/18175.36.0.1 to 175.36.63.254175.36.63.25516,382
146175.36.64.0/18175.36.64.1 to 175.36.127.254175.36.127.25516,382
147175.36.128.0/18175.36.128.1 to 175.36.191.254175.36.191.25516,382
148175.36.192.0/18175.36.192.1 to 175.36.255.254175.36.255.25516,382
149175.37.0.0/18175.37.0.1 to 175.37.63.254175.37.63.25516,382
150175.37.64.0/18175.37.64.1 to 175.37.127.254175.37.127.25516,382
151175.37.128.0/18175.37.128.1 to 175.37.191.254175.37.191.25516,382
152175.37.192.0/18175.37.192.1 to 175.37.255.254175.37.255.25516,382
153175.38.0.0/18175.38.0.1 to 175.38.63.254175.38.63.25516,382
154175.38.64.0/18175.38.64.1 to 175.38.127.254175.38.127.25516,382
155175.38.128.0/18175.38.128.1 to 175.38.191.254175.38.191.25516,382
156175.38.192.0/18175.38.192.1 to 175.38.255.254175.38.255.25516,382
157175.39.0.0/18175.39.0.1 to 175.39.63.254175.39.63.25516,382
158175.39.64.0/18175.39.64.1 to 175.39.127.254175.39.127.25516,382
159175.39.128.0/18175.39.128.1 to 175.39.191.254175.39.191.25516,382
160175.39.192.0/18175.39.192.1 to 175.39.255.254175.39.255.25516,382
161175.40.0.0/18175.40.0.1 to 175.40.63.254175.40.63.25516,382
162175.40.64.0/18175.40.64.1 to 175.40.127.254175.40.127.25516,382
163175.40.128.0/18175.40.128.1 to 175.40.191.254175.40.191.25516,382
164175.40.192.0/18175.40.192.1 to 175.40.255.254175.40.255.25516,382
165175.41.0.0/18175.41.0.1 to 175.41.63.254175.41.63.25516,382
166175.41.64.0/18175.41.64.1 to 175.41.127.254175.41.127.25516,382
167175.41.128.0/18175.41.128.1 to 175.41.191.254175.41.191.25516,382
168175.41.192.0/18175.41.192.1 to 175.41.255.254175.41.255.25516,382
169175.42.0.0/18175.42.0.1 to 175.42.63.254175.42.63.25516,382
170175.42.64.0/18175.42.64.1 to 175.42.127.254175.42.127.25516,382
171175.42.128.0/18175.42.128.1 to 175.42.191.254175.42.191.25516,382
172175.42.192.0/18175.42.192.1 to 175.42.255.254175.42.255.25516,382
173175.43.0.0/18175.43.0.1 to 175.43.63.254175.43.63.25516,382
174175.43.64.0/18175.43.64.1 to 175.43.127.254175.43.127.25516,382
175175.43.128.0/18175.43.128.1 to 175.43.191.254175.43.191.25516,382
176175.43.192.0/18175.43.192.1 to 175.43.255.254175.43.255.25516,382
177175.44.0.0/18175.44.0.1 to 175.44.63.254175.44.63.25516,382
178175.44.64.0/18175.44.64.1 to 175.44.127.254175.44.127.25516,382
179175.44.128.0/18175.44.128.1 to 175.44.191.254175.44.191.25516,382
180175.44.192.0/18175.44.192.1 to 175.44.255.254175.44.255.25516,382
181175.45.0.0/18175.45.0.1 to 175.45.63.254175.45.63.25516,382
182175.45.64.0/18175.45.64.1 to 175.45.127.254175.45.127.25516,382
183175.45.128.0/18175.45.128.1 to 175.45.191.254175.45.191.25516,382
184175.45.192.0/18175.45.192.1 to 175.45.255.254175.45.255.25516,382
185175.46.0.0/18175.46.0.1 to 175.46.63.254175.46.63.25516,382
186175.46.64.0/18175.46.64.1 to 175.46.127.254175.46.127.25516,382
187175.46.128.0/18175.46.128.1 to 175.46.191.254175.46.191.25516,382
188175.46.192.0/18175.46.192.1 to 175.46.255.254175.46.255.25516,382
189175.47.0.0/18175.47.0.1 to 175.47.63.254175.47.63.25516,382
190175.47.64.0/18175.47.64.1 to 175.47.127.254175.47.127.25516,382
191175.47.128.0/18175.47.128.1 to 175.47.191.254175.47.191.25516,382
192175.47.192.0/18175.47.192.1 to 175.47.255.254175.47.255.25516,382
193175.48.0.0/18175.48.0.1 to 175.48.63.254175.48.63.25516,382
194175.48.64.0/18175.48.64.1 to 175.48.127.254175.48.127.25516,382
195175.48.128.0/18175.48.128.1 to 175.48.191.254175.48.191.25516,382
196175.48.192.0/18175.48.192.1 to 175.48.255.254175.48.255.25516,382
197175.49.0.0/18175.49.0.1 to 175.49.63.254175.49.63.25516,382
198175.49.64.0/18175.49.64.1 to 175.49.127.254175.49.127.25516,382
199175.49.128.0/18175.49.128.1 to 175.49.191.254175.49.191.25516,382
200175.49.192.0/18175.49.192.1 to 175.49.255.254175.49.255.25516,382
201175.50.0.0/18175.50.0.1 to 175.50.63.254175.50.63.25516,382
202175.50.64.0/18175.50.64.1 to 175.50.127.254175.50.127.25516,382
203175.50.128.0/18175.50.128.1 to 175.50.191.254175.50.191.25516,382
204175.50.192.0/18175.50.192.1 to 175.50.255.254175.50.255.25516,382
205175.51.0.0/18175.51.0.1 to 175.51.63.254175.51.63.25516,382
206175.51.64.0/18175.51.64.1 to 175.51.127.254175.51.127.25516,382
207175.51.128.0/18175.51.128.1 to 175.51.191.254175.51.191.25516,382
208175.51.192.0/18175.51.192.1 to 175.51.255.254175.51.255.25516,382
209175.52.0.0/18175.52.0.1 to 175.52.63.254175.52.63.25516,382
210175.52.64.0/18175.52.64.1 to 175.52.127.254175.52.127.25516,382
211175.52.128.0/18175.52.128.1 to 175.52.191.254175.52.191.25516,382
212175.52.192.0/18175.52.192.1 to 175.52.255.254175.52.255.25516,382
213175.53.0.0/18175.53.0.1 to 175.53.63.254175.53.63.25516,382
214175.53.64.0/18175.53.64.1 to 175.53.127.254175.53.127.25516,382
215175.53.128.0/18175.53.128.1 to 175.53.191.254175.53.191.25516,382
216175.53.192.0/18175.53.192.1 to 175.53.255.254175.53.255.25516,382
217175.54.0.0/18175.54.0.1 to 175.54.63.254175.54.63.25516,382
218175.54.64.0/18175.54.64.1 to 175.54.127.254175.54.127.25516,382
219175.54.128.0/18175.54.128.1 to 175.54.191.254175.54.191.25516,382
220175.54.192.0/18175.54.192.1 to 175.54.255.254175.54.255.25516,382
221175.55.0.0/18175.55.0.1 to 175.55.63.254175.55.63.25516,382
222175.55.64.0/18175.55.64.1 to 175.55.127.254175.55.127.25516,382
223175.55.128.0/18175.55.128.1 to 175.55.191.254175.55.191.25516,382
224175.55.192.0/18175.55.192.1 to 175.55.255.254175.55.255.25516,382
225175.56.0.0/18175.56.0.1 to 175.56.63.254175.56.63.25516,382
226175.56.64.0/18175.56.64.1 to 175.56.127.254175.56.127.25516,382
227175.56.128.0/18175.56.128.1 to 175.56.191.254175.56.191.25516,382
228175.56.192.0/18175.56.192.1 to 175.56.255.254175.56.255.25516,382
229175.57.0.0/18175.57.0.1 to 175.57.63.254175.57.63.25516,382
230175.57.64.0/18175.57.64.1 to 175.57.127.254175.57.127.25516,382
231175.57.128.0/18175.57.128.1 to 175.57.191.254175.57.191.25516,382
232175.57.192.0/18175.57.192.1 to 175.57.255.254175.57.255.25516,382
233175.58.0.0/18175.58.0.1 to 175.58.63.254175.58.63.25516,382
234175.58.64.0/18175.58.64.1 to 175.58.127.254175.58.127.25516,382
235175.58.128.0/18175.58.128.1 to 175.58.191.254175.58.191.25516,382
236175.58.192.0/18175.58.192.1 to 175.58.255.254175.58.255.25516,382
237175.59.0.0/18175.59.0.1 to 175.59.63.254175.59.63.25516,382
238175.59.64.0/18175.59.64.1 to 175.59.127.254175.59.127.25516,382
239175.59.128.0/18175.59.128.1 to 175.59.191.254175.59.191.25516,382
240175.59.192.0/18175.59.192.1 to 175.59.255.254175.59.255.25516,382
241175.60.0.0/18175.60.0.1 to 175.60.63.254175.60.63.25516,382
242175.60.64.0/18175.60.64.1 to 175.60.127.254175.60.127.25516,382
243175.60.128.0/18175.60.128.1 to 175.60.191.254175.60.191.25516,382
244175.60.192.0/18175.60.192.1 to 175.60.255.254175.60.255.25516,382
245175.61.0.0/18175.61.0.1 to 175.61.63.254175.61.63.25516,382
246175.61.64.0/18175.61.64.1 to 175.61.127.254175.61.127.25516,382
247175.61.128.0/18175.61.128.1 to 175.61.191.254175.61.191.25516,382
248175.61.192.0/18175.61.192.1 to 175.61.255.254175.61.255.25516,382
249175.62.0.0/18175.62.0.1 to 175.62.63.254175.62.63.25516,382
250175.62.64.0/18175.62.64.1 to 175.62.127.254175.62.127.25516,382
251175.62.128.0/18175.62.128.1 to 175.62.191.254175.62.191.25516,382
252175.62.192.0/18175.62.192.1 to 175.62.255.254175.62.255.25516,382
253175.63.0.0/18175.63.0.1 to 175.63.63.254175.63.63.25516,382
254175.63.64.0/18175.63.64.1 to 175.63.127.254175.63.127.25516,382
255175.63.128.0/18175.63.128.1 to 175.63.191.254175.63.191.25516,382
256175.63.192.0/18175.63.192.1 to 175.63.255.254175.63.255.25516,382

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.