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.

Network170.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
170.0.0.0
Broadcast address
171.255.255.255
First usable
170.0.0.1
Last usable
171.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
B (default /16)
As numbers
Hex AA000000 · Integer 2852126720 to 2885681151
Reverse DNS zones
170.in-addr.arpa
171.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10101010.00000000.00000000.00000000170.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network10101010.00000000.00000000.00000000170.0.0.0
Broadcast10101011.11111111.11111111.11111111171.255.255.255
Split into smaller subnets/18
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

170.0.0.0/7 makes 2,048 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1170.0.0.0/18170.0.0.1 to 170.0.63.254170.0.63.25516,382
2170.0.64.0/18170.0.64.1 to 170.0.127.254170.0.127.25516,382
3170.0.128.0/18170.0.128.1 to 170.0.191.254170.0.191.25516,382
4170.0.192.0/18170.0.192.1 to 170.0.255.254170.0.255.25516,382
5170.1.0.0/18170.1.0.1 to 170.1.63.254170.1.63.25516,382
6170.1.64.0/18170.1.64.1 to 170.1.127.254170.1.127.25516,382
7170.1.128.0/18170.1.128.1 to 170.1.191.254170.1.191.25516,382
8170.1.192.0/18170.1.192.1 to 170.1.255.254170.1.255.25516,382
9170.2.0.0/18170.2.0.1 to 170.2.63.254170.2.63.25516,382
10170.2.64.0/18170.2.64.1 to 170.2.127.254170.2.127.25516,382
11170.2.128.0/18170.2.128.1 to 170.2.191.254170.2.191.25516,382
12170.2.192.0/18170.2.192.1 to 170.2.255.254170.2.255.25516,382
13170.3.0.0/18170.3.0.1 to 170.3.63.254170.3.63.25516,382
14170.3.64.0/18170.3.64.1 to 170.3.127.254170.3.127.25516,382
15170.3.128.0/18170.3.128.1 to 170.3.191.254170.3.191.25516,382
16170.3.192.0/18170.3.192.1 to 170.3.255.254170.3.255.25516,382
17170.4.0.0/18170.4.0.1 to 170.4.63.254170.4.63.25516,382
18170.4.64.0/18170.4.64.1 to 170.4.127.254170.4.127.25516,382
19170.4.128.0/18170.4.128.1 to 170.4.191.254170.4.191.25516,382
20170.4.192.0/18170.4.192.1 to 170.4.255.254170.4.255.25516,382
21170.5.0.0/18170.5.0.1 to 170.5.63.254170.5.63.25516,382
22170.5.64.0/18170.5.64.1 to 170.5.127.254170.5.127.25516,382
23170.5.128.0/18170.5.128.1 to 170.5.191.254170.5.191.25516,382
24170.5.192.0/18170.5.192.1 to 170.5.255.254170.5.255.25516,382
25170.6.0.0/18170.6.0.1 to 170.6.63.254170.6.63.25516,382
26170.6.64.0/18170.6.64.1 to 170.6.127.254170.6.127.25516,382
27170.6.128.0/18170.6.128.1 to 170.6.191.254170.6.191.25516,382
28170.6.192.0/18170.6.192.1 to 170.6.255.254170.6.255.25516,382
29170.7.0.0/18170.7.0.1 to 170.7.63.254170.7.63.25516,382
30170.7.64.0/18170.7.64.1 to 170.7.127.254170.7.127.25516,382
31170.7.128.0/18170.7.128.1 to 170.7.191.254170.7.191.25516,382
32170.7.192.0/18170.7.192.1 to 170.7.255.254170.7.255.25516,382
33170.8.0.0/18170.8.0.1 to 170.8.63.254170.8.63.25516,382
34170.8.64.0/18170.8.64.1 to 170.8.127.254170.8.127.25516,382
35170.8.128.0/18170.8.128.1 to 170.8.191.254170.8.191.25516,382
36170.8.192.0/18170.8.192.1 to 170.8.255.254170.8.255.25516,382
37170.9.0.0/18170.9.0.1 to 170.9.63.254170.9.63.25516,382
38170.9.64.0/18170.9.64.1 to 170.9.127.254170.9.127.25516,382
39170.9.128.0/18170.9.128.1 to 170.9.191.254170.9.191.25516,382
40170.9.192.0/18170.9.192.1 to 170.9.255.254170.9.255.25516,382
41170.10.0.0/18170.10.0.1 to 170.10.63.254170.10.63.25516,382
42170.10.64.0/18170.10.64.1 to 170.10.127.254170.10.127.25516,382
43170.10.128.0/18170.10.128.1 to 170.10.191.254170.10.191.25516,382
44170.10.192.0/18170.10.192.1 to 170.10.255.254170.10.255.25516,382
45170.11.0.0/18170.11.0.1 to 170.11.63.254170.11.63.25516,382
46170.11.64.0/18170.11.64.1 to 170.11.127.254170.11.127.25516,382
47170.11.128.0/18170.11.128.1 to 170.11.191.254170.11.191.25516,382
48170.11.192.0/18170.11.192.1 to 170.11.255.254170.11.255.25516,382
49170.12.0.0/18170.12.0.1 to 170.12.63.254170.12.63.25516,382
50170.12.64.0/18170.12.64.1 to 170.12.127.254170.12.127.25516,382
51170.12.128.0/18170.12.128.1 to 170.12.191.254170.12.191.25516,382
52170.12.192.0/18170.12.192.1 to 170.12.255.254170.12.255.25516,382
53170.13.0.0/18170.13.0.1 to 170.13.63.254170.13.63.25516,382
54170.13.64.0/18170.13.64.1 to 170.13.127.254170.13.127.25516,382
55170.13.128.0/18170.13.128.1 to 170.13.191.254170.13.191.25516,382
56170.13.192.0/18170.13.192.1 to 170.13.255.254170.13.255.25516,382
57170.14.0.0/18170.14.0.1 to 170.14.63.254170.14.63.25516,382
58170.14.64.0/18170.14.64.1 to 170.14.127.254170.14.127.25516,382
59170.14.128.0/18170.14.128.1 to 170.14.191.254170.14.191.25516,382
60170.14.192.0/18170.14.192.1 to 170.14.255.254170.14.255.25516,382
61170.15.0.0/18170.15.0.1 to 170.15.63.254170.15.63.25516,382
62170.15.64.0/18170.15.64.1 to 170.15.127.254170.15.127.25516,382
63170.15.128.0/18170.15.128.1 to 170.15.191.254170.15.191.25516,382
64170.15.192.0/18170.15.192.1 to 170.15.255.254170.15.255.25516,382
65170.16.0.0/18170.16.0.1 to 170.16.63.254170.16.63.25516,382
66170.16.64.0/18170.16.64.1 to 170.16.127.254170.16.127.25516,382
67170.16.128.0/18170.16.128.1 to 170.16.191.254170.16.191.25516,382
68170.16.192.0/18170.16.192.1 to 170.16.255.254170.16.255.25516,382
69170.17.0.0/18170.17.0.1 to 170.17.63.254170.17.63.25516,382
70170.17.64.0/18170.17.64.1 to 170.17.127.254170.17.127.25516,382
71170.17.128.0/18170.17.128.1 to 170.17.191.254170.17.191.25516,382
72170.17.192.0/18170.17.192.1 to 170.17.255.254170.17.255.25516,382
73170.18.0.0/18170.18.0.1 to 170.18.63.254170.18.63.25516,382
74170.18.64.0/18170.18.64.1 to 170.18.127.254170.18.127.25516,382
75170.18.128.0/18170.18.128.1 to 170.18.191.254170.18.191.25516,382
76170.18.192.0/18170.18.192.1 to 170.18.255.254170.18.255.25516,382
77170.19.0.0/18170.19.0.1 to 170.19.63.254170.19.63.25516,382
78170.19.64.0/18170.19.64.1 to 170.19.127.254170.19.127.25516,382
79170.19.128.0/18170.19.128.1 to 170.19.191.254170.19.191.25516,382
80170.19.192.0/18170.19.192.1 to 170.19.255.254170.19.255.25516,382
81170.20.0.0/18170.20.0.1 to 170.20.63.254170.20.63.25516,382
82170.20.64.0/18170.20.64.1 to 170.20.127.254170.20.127.25516,382
83170.20.128.0/18170.20.128.1 to 170.20.191.254170.20.191.25516,382
84170.20.192.0/18170.20.192.1 to 170.20.255.254170.20.255.25516,382
85170.21.0.0/18170.21.0.1 to 170.21.63.254170.21.63.25516,382
86170.21.64.0/18170.21.64.1 to 170.21.127.254170.21.127.25516,382
87170.21.128.0/18170.21.128.1 to 170.21.191.254170.21.191.25516,382
88170.21.192.0/18170.21.192.1 to 170.21.255.254170.21.255.25516,382
89170.22.0.0/18170.22.0.1 to 170.22.63.254170.22.63.25516,382
90170.22.64.0/18170.22.64.1 to 170.22.127.254170.22.127.25516,382
91170.22.128.0/18170.22.128.1 to 170.22.191.254170.22.191.25516,382
92170.22.192.0/18170.22.192.1 to 170.22.255.254170.22.255.25516,382
93170.23.0.0/18170.23.0.1 to 170.23.63.254170.23.63.25516,382
94170.23.64.0/18170.23.64.1 to 170.23.127.254170.23.127.25516,382
95170.23.128.0/18170.23.128.1 to 170.23.191.254170.23.191.25516,382
96170.23.192.0/18170.23.192.1 to 170.23.255.254170.23.255.25516,382
97170.24.0.0/18170.24.0.1 to 170.24.63.254170.24.63.25516,382
98170.24.64.0/18170.24.64.1 to 170.24.127.254170.24.127.25516,382
99170.24.128.0/18170.24.128.1 to 170.24.191.254170.24.191.25516,382
100170.24.192.0/18170.24.192.1 to 170.24.255.254170.24.255.25516,382
101170.25.0.0/18170.25.0.1 to 170.25.63.254170.25.63.25516,382
102170.25.64.0/18170.25.64.1 to 170.25.127.254170.25.127.25516,382
103170.25.128.0/18170.25.128.1 to 170.25.191.254170.25.191.25516,382
104170.25.192.0/18170.25.192.1 to 170.25.255.254170.25.255.25516,382
105170.26.0.0/18170.26.0.1 to 170.26.63.254170.26.63.25516,382
106170.26.64.0/18170.26.64.1 to 170.26.127.254170.26.127.25516,382
107170.26.128.0/18170.26.128.1 to 170.26.191.254170.26.191.25516,382
108170.26.192.0/18170.26.192.1 to 170.26.255.254170.26.255.25516,382
109170.27.0.0/18170.27.0.1 to 170.27.63.254170.27.63.25516,382
110170.27.64.0/18170.27.64.1 to 170.27.127.254170.27.127.25516,382
111170.27.128.0/18170.27.128.1 to 170.27.191.254170.27.191.25516,382
112170.27.192.0/18170.27.192.1 to 170.27.255.254170.27.255.25516,382
113170.28.0.0/18170.28.0.1 to 170.28.63.254170.28.63.25516,382
114170.28.64.0/18170.28.64.1 to 170.28.127.254170.28.127.25516,382
115170.28.128.0/18170.28.128.1 to 170.28.191.254170.28.191.25516,382
116170.28.192.0/18170.28.192.1 to 170.28.255.254170.28.255.25516,382
117170.29.0.0/18170.29.0.1 to 170.29.63.254170.29.63.25516,382
118170.29.64.0/18170.29.64.1 to 170.29.127.254170.29.127.25516,382
119170.29.128.0/18170.29.128.1 to 170.29.191.254170.29.191.25516,382
120170.29.192.0/18170.29.192.1 to 170.29.255.254170.29.255.25516,382
121170.30.0.0/18170.30.0.1 to 170.30.63.254170.30.63.25516,382
122170.30.64.0/18170.30.64.1 to 170.30.127.254170.30.127.25516,382
123170.30.128.0/18170.30.128.1 to 170.30.191.254170.30.191.25516,382
124170.30.192.0/18170.30.192.1 to 170.30.255.254170.30.255.25516,382
125170.31.0.0/18170.31.0.1 to 170.31.63.254170.31.63.25516,382
126170.31.64.0/18170.31.64.1 to 170.31.127.254170.31.127.25516,382
127170.31.128.0/18170.31.128.1 to 170.31.191.254170.31.191.25516,382
128170.31.192.0/18170.31.192.1 to 170.31.255.254170.31.255.25516,382
129170.32.0.0/18170.32.0.1 to 170.32.63.254170.32.63.25516,382
130170.32.64.0/18170.32.64.1 to 170.32.127.254170.32.127.25516,382
131170.32.128.0/18170.32.128.1 to 170.32.191.254170.32.191.25516,382
132170.32.192.0/18170.32.192.1 to 170.32.255.254170.32.255.25516,382
133170.33.0.0/18170.33.0.1 to 170.33.63.254170.33.63.25516,382
134170.33.64.0/18170.33.64.1 to 170.33.127.254170.33.127.25516,382
135170.33.128.0/18170.33.128.1 to 170.33.191.254170.33.191.25516,382
136170.33.192.0/18170.33.192.1 to 170.33.255.254170.33.255.25516,382
137170.34.0.0/18170.34.0.1 to 170.34.63.254170.34.63.25516,382
138170.34.64.0/18170.34.64.1 to 170.34.127.254170.34.127.25516,382
139170.34.128.0/18170.34.128.1 to 170.34.191.254170.34.191.25516,382
140170.34.192.0/18170.34.192.1 to 170.34.255.254170.34.255.25516,382
141170.35.0.0/18170.35.0.1 to 170.35.63.254170.35.63.25516,382
142170.35.64.0/18170.35.64.1 to 170.35.127.254170.35.127.25516,382
143170.35.128.0/18170.35.128.1 to 170.35.191.254170.35.191.25516,382
144170.35.192.0/18170.35.192.1 to 170.35.255.254170.35.255.25516,382
145170.36.0.0/18170.36.0.1 to 170.36.63.254170.36.63.25516,382
146170.36.64.0/18170.36.64.1 to 170.36.127.254170.36.127.25516,382
147170.36.128.0/18170.36.128.1 to 170.36.191.254170.36.191.25516,382
148170.36.192.0/18170.36.192.1 to 170.36.255.254170.36.255.25516,382
149170.37.0.0/18170.37.0.1 to 170.37.63.254170.37.63.25516,382
150170.37.64.0/18170.37.64.1 to 170.37.127.254170.37.127.25516,382
151170.37.128.0/18170.37.128.1 to 170.37.191.254170.37.191.25516,382
152170.37.192.0/18170.37.192.1 to 170.37.255.254170.37.255.25516,382
153170.38.0.0/18170.38.0.1 to 170.38.63.254170.38.63.25516,382
154170.38.64.0/18170.38.64.1 to 170.38.127.254170.38.127.25516,382
155170.38.128.0/18170.38.128.1 to 170.38.191.254170.38.191.25516,382
156170.38.192.0/18170.38.192.1 to 170.38.255.254170.38.255.25516,382
157170.39.0.0/18170.39.0.1 to 170.39.63.254170.39.63.25516,382
158170.39.64.0/18170.39.64.1 to 170.39.127.254170.39.127.25516,382
159170.39.128.0/18170.39.128.1 to 170.39.191.254170.39.191.25516,382
160170.39.192.0/18170.39.192.1 to 170.39.255.254170.39.255.25516,382
161170.40.0.0/18170.40.0.1 to 170.40.63.254170.40.63.25516,382
162170.40.64.0/18170.40.64.1 to 170.40.127.254170.40.127.25516,382
163170.40.128.0/18170.40.128.1 to 170.40.191.254170.40.191.25516,382
164170.40.192.0/18170.40.192.1 to 170.40.255.254170.40.255.25516,382
165170.41.0.0/18170.41.0.1 to 170.41.63.254170.41.63.25516,382
166170.41.64.0/18170.41.64.1 to 170.41.127.254170.41.127.25516,382
167170.41.128.0/18170.41.128.1 to 170.41.191.254170.41.191.25516,382
168170.41.192.0/18170.41.192.1 to 170.41.255.254170.41.255.25516,382
169170.42.0.0/18170.42.0.1 to 170.42.63.254170.42.63.25516,382
170170.42.64.0/18170.42.64.1 to 170.42.127.254170.42.127.25516,382
171170.42.128.0/18170.42.128.1 to 170.42.191.254170.42.191.25516,382
172170.42.192.0/18170.42.192.1 to 170.42.255.254170.42.255.25516,382
173170.43.0.0/18170.43.0.1 to 170.43.63.254170.43.63.25516,382
174170.43.64.0/18170.43.64.1 to 170.43.127.254170.43.127.25516,382
175170.43.128.0/18170.43.128.1 to 170.43.191.254170.43.191.25516,382
176170.43.192.0/18170.43.192.1 to 170.43.255.254170.43.255.25516,382
177170.44.0.0/18170.44.0.1 to 170.44.63.254170.44.63.25516,382
178170.44.64.0/18170.44.64.1 to 170.44.127.254170.44.127.25516,382
179170.44.128.0/18170.44.128.1 to 170.44.191.254170.44.191.25516,382
180170.44.192.0/18170.44.192.1 to 170.44.255.254170.44.255.25516,382
181170.45.0.0/18170.45.0.1 to 170.45.63.254170.45.63.25516,382
182170.45.64.0/18170.45.64.1 to 170.45.127.254170.45.127.25516,382
183170.45.128.0/18170.45.128.1 to 170.45.191.254170.45.191.25516,382
184170.45.192.0/18170.45.192.1 to 170.45.255.254170.45.255.25516,382
185170.46.0.0/18170.46.0.1 to 170.46.63.254170.46.63.25516,382
186170.46.64.0/18170.46.64.1 to 170.46.127.254170.46.127.25516,382
187170.46.128.0/18170.46.128.1 to 170.46.191.254170.46.191.25516,382
188170.46.192.0/18170.46.192.1 to 170.46.255.254170.46.255.25516,382
189170.47.0.0/18170.47.0.1 to 170.47.63.254170.47.63.25516,382
190170.47.64.0/18170.47.64.1 to 170.47.127.254170.47.127.25516,382
191170.47.128.0/18170.47.128.1 to 170.47.191.254170.47.191.25516,382
192170.47.192.0/18170.47.192.1 to 170.47.255.254170.47.255.25516,382
193170.48.0.0/18170.48.0.1 to 170.48.63.254170.48.63.25516,382
194170.48.64.0/18170.48.64.1 to 170.48.127.254170.48.127.25516,382
195170.48.128.0/18170.48.128.1 to 170.48.191.254170.48.191.25516,382
196170.48.192.0/18170.48.192.1 to 170.48.255.254170.48.255.25516,382
197170.49.0.0/18170.49.0.1 to 170.49.63.254170.49.63.25516,382
198170.49.64.0/18170.49.64.1 to 170.49.127.254170.49.127.25516,382
199170.49.128.0/18170.49.128.1 to 170.49.191.254170.49.191.25516,382
200170.49.192.0/18170.49.192.1 to 170.49.255.254170.49.255.25516,382
201170.50.0.0/18170.50.0.1 to 170.50.63.254170.50.63.25516,382
202170.50.64.0/18170.50.64.1 to 170.50.127.254170.50.127.25516,382
203170.50.128.0/18170.50.128.1 to 170.50.191.254170.50.191.25516,382
204170.50.192.0/18170.50.192.1 to 170.50.255.254170.50.255.25516,382
205170.51.0.0/18170.51.0.1 to 170.51.63.254170.51.63.25516,382
206170.51.64.0/18170.51.64.1 to 170.51.127.254170.51.127.25516,382
207170.51.128.0/18170.51.128.1 to 170.51.191.254170.51.191.25516,382
208170.51.192.0/18170.51.192.1 to 170.51.255.254170.51.255.25516,382
209170.52.0.0/18170.52.0.1 to 170.52.63.254170.52.63.25516,382
210170.52.64.0/18170.52.64.1 to 170.52.127.254170.52.127.25516,382
211170.52.128.0/18170.52.128.1 to 170.52.191.254170.52.191.25516,382
212170.52.192.0/18170.52.192.1 to 170.52.255.254170.52.255.25516,382
213170.53.0.0/18170.53.0.1 to 170.53.63.254170.53.63.25516,382
214170.53.64.0/18170.53.64.1 to 170.53.127.254170.53.127.25516,382
215170.53.128.0/18170.53.128.1 to 170.53.191.254170.53.191.25516,382
216170.53.192.0/18170.53.192.1 to 170.53.255.254170.53.255.25516,382
217170.54.0.0/18170.54.0.1 to 170.54.63.254170.54.63.25516,382
218170.54.64.0/18170.54.64.1 to 170.54.127.254170.54.127.25516,382
219170.54.128.0/18170.54.128.1 to 170.54.191.254170.54.191.25516,382
220170.54.192.0/18170.54.192.1 to 170.54.255.254170.54.255.25516,382
221170.55.0.0/18170.55.0.1 to 170.55.63.254170.55.63.25516,382
222170.55.64.0/18170.55.64.1 to 170.55.127.254170.55.127.25516,382
223170.55.128.0/18170.55.128.1 to 170.55.191.254170.55.191.25516,382
224170.55.192.0/18170.55.192.1 to 170.55.255.254170.55.255.25516,382
225170.56.0.0/18170.56.0.1 to 170.56.63.254170.56.63.25516,382
226170.56.64.0/18170.56.64.1 to 170.56.127.254170.56.127.25516,382
227170.56.128.0/18170.56.128.1 to 170.56.191.254170.56.191.25516,382
228170.56.192.0/18170.56.192.1 to 170.56.255.254170.56.255.25516,382
229170.57.0.0/18170.57.0.1 to 170.57.63.254170.57.63.25516,382
230170.57.64.0/18170.57.64.1 to 170.57.127.254170.57.127.25516,382
231170.57.128.0/18170.57.128.1 to 170.57.191.254170.57.191.25516,382
232170.57.192.0/18170.57.192.1 to 170.57.255.254170.57.255.25516,382
233170.58.0.0/18170.58.0.1 to 170.58.63.254170.58.63.25516,382
234170.58.64.0/18170.58.64.1 to 170.58.127.254170.58.127.25516,382
235170.58.128.0/18170.58.128.1 to 170.58.191.254170.58.191.25516,382
236170.58.192.0/18170.58.192.1 to 170.58.255.254170.58.255.25516,382
237170.59.0.0/18170.59.0.1 to 170.59.63.254170.59.63.25516,382
238170.59.64.0/18170.59.64.1 to 170.59.127.254170.59.127.25516,382
239170.59.128.0/18170.59.128.1 to 170.59.191.254170.59.191.25516,382
240170.59.192.0/18170.59.192.1 to 170.59.255.254170.59.255.25516,382
241170.60.0.0/18170.60.0.1 to 170.60.63.254170.60.63.25516,382
242170.60.64.0/18170.60.64.1 to 170.60.127.254170.60.127.25516,382
243170.60.128.0/18170.60.128.1 to 170.60.191.254170.60.191.25516,382
244170.60.192.0/18170.60.192.1 to 170.60.255.254170.60.255.25516,382
245170.61.0.0/18170.61.0.1 to 170.61.63.254170.61.63.25516,382
246170.61.64.0/18170.61.64.1 to 170.61.127.254170.61.127.25516,382
247170.61.128.0/18170.61.128.1 to 170.61.191.254170.61.191.25516,382
248170.61.192.0/18170.61.192.1 to 170.61.255.254170.61.255.25516,382
249170.62.0.0/18170.62.0.1 to 170.62.63.254170.62.63.25516,382
250170.62.64.0/18170.62.64.1 to 170.62.127.254170.62.127.25516,382
251170.62.128.0/18170.62.128.1 to 170.62.191.254170.62.191.25516,382
252170.62.192.0/18170.62.192.1 to 170.62.255.254170.62.255.25516,382
253170.63.0.0/18170.63.0.1 to 170.63.63.254170.63.63.25516,382
254170.63.64.0/18170.63.64.1 to 170.63.127.254170.63.127.25516,382
255170.63.128.0/18170.63.128.1 to 170.63.191.254170.63.191.25516,382
256170.63.192.0/18170.63.192.1 to 170.63.255.254170.63.255.25516,382

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.