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.

Network244.0.0.0/6
Usable hosts67,108,862
Subnet mask252.0.0.0
Addresses67,108,864
Network address
244.0.0.0
Broadcast address
247.255.255.255
First usable
244.0.0.1
Last usable
247.255.255.254
Usable hosts
67,108,862 (67,108,864 less the network and broadcast addresses)
Subnet mask
252.0.0.0
Wildcard mask
3.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/6
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F4000000 · Integer 4093640704 to 4160749567
Reverse DNS zones
244.in-addr.arpa
245.in-addr.arpa
246.in-addr.arpa
247.in-addr.arpa
/6 is not on a 8-bit boundary, so it takes 4 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11110100.00000000.00000000.00000000244.0.0.0
Subnet mask11111100.00000000.00000000.00000000252.0.0.0
Network11110100.00000000.00000000.00000000244.0.0.0
Broadcast11110111.11111111.11111111.11111111247.255.255.255
Split into smaller subnets/17
/7 (2)/8 (4)/9 (8)/10 (16)/11 (32)/12 (64)/13 (128)/14 (256)/15 (512)/16 (1,024)/17 (2,048)/18 (4,096)

244.0.0.0/6 makes 2,048 subnets of /17; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1244.0.0.0/17244.0.0.1 to 244.0.127.254244.0.127.25532,766
2244.0.128.0/17244.0.128.1 to 244.0.255.254244.0.255.25532,766
3244.1.0.0/17244.1.0.1 to 244.1.127.254244.1.127.25532,766
4244.1.128.0/17244.1.128.1 to 244.1.255.254244.1.255.25532,766
5244.2.0.0/17244.2.0.1 to 244.2.127.254244.2.127.25532,766
6244.2.128.0/17244.2.128.1 to 244.2.255.254244.2.255.25532,766
7244.3.0.0/17244.3.0.1 to 244.3.127.254244.3.127.25532,766
8244.3.128.0/17244.3.128.1 to 244.3.255.254244.3.255.25532,766
9244.4.0.0/17244.4.0.1 to 244.4.127.254244.4.127.25532,766
10244.4.128.0/17244.4.128.1 to 244.4.255.254244.4.255.25532,766
11244.5.0.0/17244.5.0.1 to 244.5.127.254244.5.127.25532,766
12244.5.128.0/17244.5.128.1 to 244.5.255.254244.5.255.25532,766
13244.6.0.0/17244.6.0.1 to 244.6.127.254244.6.127.25532,766
14244.6.128.0/17244.6.128.1 to 244.6.255.254244.6.255.25532,766
15244.7.0.0/17244.7.0.1 to 244.7.127.254244.7.127.25532,766
16244.7.128.0/17244.7.128.1 to 244.7.255.254244.7.255.25532,766
17244.8.0.0/17244.8.0.1 to 244.8.127.254244.8.127.25532,766
18244.8.128.0/17244.8.128.1 to 244.8.255.254244.8.255.25532,766
19244.9.0.0/17244.9.0.1 to 244.9.127.254244.9.127.25532,766
20244.9.128.0/17244.9.128.1 to 244.9.255.254244.9.255.25532,766
21244.10.0.0/17244.10.0.1 to 244.10.127.254244.10.127.25532,766
22244.10.128.0/17244.10.128.1 to 244.10.255.254244.10.255.25532,766
23244.11.0.0/17244.11.0.1 to 244.11.127.254244.11.127.25532,766
24244.11.128.0/17244.11.128.1 to 244.11.255.254244.11.255.25532,766
25244.12.0.0/17244.12.0.1 to 244.12.127.254244.12.127.25532,766
26244.12.128.0/17244.12.128.1 to 244.12.255.254244.12.255.25532,766
27244.13.0.0/17244.13.0.1 to 244.13.127.254244.13.127.25532,766
28244.13.128.0/17244.13.128.1 to 244.13.255.254244.13.255.25532,766
29244.14.0.0/17244.14.0.1 to 244.14.127.254244.14.127.25532,766
30244.14.128.0/17244.14.128.1 to 244.14.255.254244.14.255.25532,766
31244.15.0.0/17244.15.0.1 to 244.15.127.254244.15.127.25532,766
32244.15.128.0/17244.15.128.1 to 244.15.255.254244.15.255.25532,766
33244.16.0.0/17244.16.0.1 to 244.16.127.254244.16.127.25532,766
34244.16.128.0/17244.16.128.1 to 244.16.255.254244.16.255.25532,766
35244.17.0.0/17244.17.0.1 to 244.17.127.254244.17.127.25532,766
36244.17.128.0/17244.17.128.1 to 244.17.255.254244.17.255.25532,766
37244.18.0.0/17244.18.0.1 to 244.18.127.254244.18.127.25532,766
38244.18.128.0/17244.18.128.1 to 244.18.255.254244.18.255.25532,766
39244.19.0.0/17244.19.0.1 to 244.19.127.254244.19.127.25532,766
40244.19.128.0/17244.19.128.1 to 244.19.255.254244.19.255.25532,766
41244.20.0.0/17244.20.0.1 to 244.20.127.254244.20.127.25532,766
42244.20.128.0/17244.20.128.1 to 244.20.255.254244.20.255.25532,766
43244.21.0.0/17244.21.0.1 to 244.21.127.254244.21.127.25532,766
44244.21.128.0/17244.21.128.1 to 244.21.255.254244.21.255.25532,766
45244.22.0.0/17244.22.0.1 to 244.22.127.254244.22.127.25532,766
46244.22.128.0/17244.22.128.1 to 244.22.255.254244.22.255.25532,766
47244.23.0.0/17244.23.0.1 to 244.23.127.254244.23.127.25532,766
48244.23.128.0/17244.23.128.1 to 244.23.255.254244.23.255.25532,766
49244.24.0.0/17244.24.0.1 to 244.24.127.254244.24.127.25532,766
50244.24.128.0/17244.24.128.1 to 244.24.255.254244.24.255.25532,766
51244.25.0.0/17244.25.0.1 to 244.25.127.254244.25.127.25532,766
52244.25.128.0/17244.25.128.1 to 244.25.255.254244.25.255.25532,766
53244.26.0.0/17244.26.0.1 to 244.26.127.254244.26.127.25532,766
54244.26.128.0/17244.26.128.1 to 244.26.255.254244.26.255.25532,766
55244.27.0.0/17244.27.0.1 to 244.27.127.254244.27.127.25532,766
56244.27.128.0/17244.27.128.1 to 244.27.255.254244.27.255.25532,766
57244.28.0.0/17244.28.0.1 to 244.28.127.254244.28.127.25532,766
58244.28.128.0/17244.28.128.1 to 244.28.255.254244.28.255.25532,766
59244.29.0.0/17244.29.0.1 to 244.29.127.254244.29.127.25532,766
60244.29.128.0/17244.29.128.1 to 244.29.255.254244.29.255.25532,766
61244.30.0.0/17244.30.0.1 to 244.30.127.254244.30.127.25532,766
62244.30.128.0/17244.30.128.1 to 244.30.255.254244.30.255.25532,766
63244.31.0.0/17244.31.0.1 to 244.31.127.254244.31.127.25532,766
64244.31.128.0/17244.31.128.1 to 244.31.255.254244.31.255.25532,766
65244.32.0.0/17244.32.0.1 to 244.32.127.254244.32.127.25532,766
66244.32.128.0/17244.32.128.1 to 244.32.255.254244.32.255.25532,766
67244.33.0.0/17244.33.0.1 to 244.33.127.254244.33.127.25532,766
68244.33.128.0/17244.33.128.1 to 244.33.255.254244.33.255.25532,766
69244.34.0.0/17244.34.0.1 to 244.34.127.254244.34.127.25532,766
70244.34.128.0/17244.34.128.1 to 244.34.255.254244.34.255.25532,766
71244.35.0.0/17244.35.0.1 to 244.35.127.254244.35.127.25532,766
72244.35.128.0/17244.35.128.1 to 244.35.255.254244.35.255.25532,766
73244.36.0.0/17244.36.0.1 to 244.36.127.254244.36.127.25532,766
74244.36.128.0/17244.36.128.1 to 244.36.255.254244.36.255.25532,766
75244.37.0.0/17244.37.0.1 to 244.37.127.254244.37.127.25532,766
76244.37.128.0/17244.37.128.1 to 244.37.255.254244.37.255.25532,766
77244.38.0.0/17244.38.0.1 to 244.38.127.254244.38.127.25532,766
78244.38.128.0/17244.38.128.1 to 244.38.255.254244.38.255.25532,766
79244.39.0.0/17244.39.0.1 to 244.39.127.254244.39.127.25532,766
80244.39.128.0/17244.39.128.1 to 244.39.255.254244.39.255.25532,766
81244.40.0.0/17244.40.0.1 to 244.40.127.254244.40.127.25532,766
82244.40.128.0/17244.40.128.1 to 244.40.255.254244.40.255.25532,766
83244.41.0.0/17244.41.0.1 to 244.41.127.254244.41.127.25532,766
84244.41.128.0/17244.41.128.1 to 244.41.255.254244.41.255.25532,766
85244.42.0.0/17244.42.0.1 to 244.42.127.254244.42.127.25532,766
86244.42.128.0/17244.42.128.1 to 244.42.255.254244.42.255.25532,766
87244.43.0.0/17244.43.0.1 to 244.43.127.254244.43.127.25532,766
88244.43.128.0/17244.43.128.1 to 244.43.255.254244.43.255.25532,766
89244.44.0.0/17244.44.0.1 to 244.44.127.254244.44.127.25532,766
90244.44.128.0/17244.44.128.1 to 244.44.255.254244.44.255.25532,766
91244.45.0.0/17244.45.0.1 to 244.45.127.254244.45.127.25532,766
92244.45.128.0/17244.45.128.1 to 244.45.255.254244.45.255.25532,766
93244.46.0.0/17244.46.0.1 to 244.46.127.254244.46.127.25532,766
94244.46.128.0/17244.46.128.1 to 244.46.255.254244.46.255.25532,766
95244.47.0.0/17244.47.0.1 to 244.47.127.254244.47.127.25532,766
96244.47.128.0/17244.47.128.1 to 244.47.255.254244.47.255.25532,766
97244.48.0.0/17244.48.0.1 to 244.48.127.254244.48.127.25532,766
98244.48.128.0/17244.48.128.1 to 244.48.255.254244.48.255.25532,766
99244.49.0.0/17244.49.0.1 to 244.49.127.254244.49.127.25532,766
100244.49.128.0/17244.49.128.1 to 244.49.255.254244.49.255.25532,766
101244.50.0.0/17244.50.0.1 to 244.50.127.254244.50.127.25532,766
102244.50.128.0/17244.50.128.1 to 244.50.255.254244.50.255.25532,766
103244.51.0.0/17244.51.0.1 to 244.51.127.254244.51.127.25532,766
104244.51.128.0/17244.51.128.1 to 244.51.255.254244.51.255.25532,766
105244.52.0.0/17244.52.0.1 to 244.52.127.254244.52.127.25532,766
106244.52.128.0/17244.52.128.1 to 244.52.255.254244.52.255.25532,766
107244.53.0.0/17244.53.0.1 to 244.53.127.254244.53.127.25532,766
108244.53.128.0/17244.53.128.1 to 244.53.255.254244.53.255.25532,766
109244.54.0.0/17244.54.0.1 to 244.54.127.254244.54.127.25532,766
110244.54.128.0/17244.54.128.1 to 244.54.255.254244.54.255.25532,766
111244.55.0.0/17244.55.0.1 to 244.55.127.254244.55.127.25532,766
112244.55.128.0/17244.55.128.1 to 244.55.255.254244.55.255.25532,766
113244.56.0.0/17244.56.0.1 to 244.56.127.254244.56.127.25532,766
114244.56.128.0/17244.56.128.1 to 244.56.255.254244.56.255.25532,766
115244.57.0.0/17244.57.0.1 to 244.57.127.254244.57.127.25532,766
116244.57.128.0/17244.57.128.1 to 244.57.255.254244.57.255.25532,766
117244.58.0.0/17244.58.0.1 to 244.58.127.254244.58.127.25532,766
118244.58.128.0/17244.58.128.1 to 244.58.255.254244.58.255.25532,766
119244.59.0.0/17244.59.0.1 to 244.59.127.254244.59.127.25532,766
120244.59.128.0/17244.59.128.1 to 244.59.255.254244.59.255.25532,766
121244.60.0.0/17244.60.0.1 to 244.60.127.254244.60.127.25532,766
122244.60.128.0/17244.60.128.1 to 244.60.255.254244.60.255.25532,766
123244.61.0.0/17244.61.0.1 to 244.61.127.254244.61.127.25532,766
124244.61.128.0/17244.61.128.1 to 244.61.255.254244.61.255.25532,766
125244.62.0.0/17244.62.0.1 to 244.62.127.254244.62.127.25532,766
126244.62.128.0/17244.62.128.1 to 244.62.255.254244.62.255.25532,766
127244.63.0.0/17244.63.0.1 to 244.63.127.254244.63.127.25532,766
128244.63.128.0/17244.63.128.1 to 244.63.255.254244.63.255.25532,766
129244.64.0.0/17244.64.0.1 to 244.64.127.254244.64.127.25532,766
130244.64.128.0/17244.64.128.1 to 244.64.255.254244.64.255.25532,766
131244.65.0.0/17244.65.0.1 to 244.65.127.254244.65.127.25532,766
132244.65.128.0/17244.65.128.1 to 244.65.255.254244.65.255.25532,766
133244.66.0.0/17244.66.0.1 to 244.66.127.254244.66.127.25532,766
134244.66.128.0/17244.66.128.1 to 244.66.255.254244.66.255.25532,766
135244.67.0.0/17244.67.0.1 to 244.67.127.254244.67.127.25532,766
136244.67.128.0/17244.67.128.1 to 244.67.255.254244.67.255.25532,766
137244.68.0.0/17244.68.0.1 to 244.68.127.254244.68.127.25532,766
138244.68.128.0/17244.68.128.1 to 244.68.255.254244.68.255.25532,766
139244.69.0.0/17244.69.0.1 to 244.69.127.254244.69.127.25532,766
140244.69.128.0/17244.69.128.1 to 244.69.255.254244.69.255.25532,766
141244.70.0.0/17244.70.0.1 to 244.70.127.254244.70.127.25532,766
142244.70.128.0/17244.70.128.1 to 244.70.255.254244.70.255.25532,766
143244.71.0.0/17244.71.0.1 to 244.71.127.254244.71.127.25532,766
144244.71.128.0/17244.71.128.1 to 244.71.255.254244.71.255.25532,766
145244.72.0.0/17244.72.0.1 to 244.72.127.254244.72.127.25532,766
146244.72.128.0/17244.72.128.1 to 244.72.255.254244.72.255.25532,766
147244.73.0.0/17244.73.0.1 to 244.73.127.254244.73.127.25532,766
148244.73.128.0/17244.73.128.1 to 244.73.255.254244.73.255.25532,766
149244.74.0.0/17244.74.0.1 to 244.74.127.254244.74.127.25532,766
150244.74.128.0/17244.74.128.1 to 244.74.255.254244.74.255.25532,766
151244.75.0.0/17244.75.0.1 to 244.75.127.254244.75.127.25532,766
152244.75.128.0/17244.75.128.1 to 244.75.255.254244.75.255.25532,766
153244.76.0.0/17244.76.0.1 to 244.76.127.254244.76.127.25532,766
154244.76.128.0/17244.76.128.1 to 244.76.255.254244.76.255.25532,766
155244.77.0.0/17244.77.0.1 to 244.77.127.254244.77.127.25532,766
156244.77.128.0/17244.77.128.1 to 244.77.255.254244.77.255.25532,766
157244.78.0.0/17244.78.0.1 to 244.78.127.254244.78.127.25532,766
158244.78.128.0/17244.78.128.1 to 244.78.255.254244.78.255.25532,766
159244.79.0.0/17244.79.0.1 to 244.79.127.254244.79.127.25532,766
160244.79.128.0/17244.79.128.1 to 244.79.255.254244.79.255.25532,766
161244.80.0.0/17244.80.0.1 to 244.80.127.254244.80.127.25532,766
162244.80.128.0/17244.80.128.1 to 244.80.255.254244.80.255.25532,766
163244.81.0.0/17244.81.0.1 to 244.81.127.254244.81.127.25532,766
164244.81.128.0/17244.81.128.1 to 244.81.255.254244.81.255.25532,766
165244.82.0.0/17244.82.0.1 to 244.82.127.254244.82.127.25532,766
166244.82.128.0/17244.82.128.1 to 244.82.255.254244.82.255.25532,766
167244.83.0.0/17244.83.0.1 to 244.83.127.254244.83.127.25532,766
168244.83.128.0/17244.83.128.1 to 244.83.255.254244.83.255.25532,766
169244.84.0.0/17244.84.0.1 to 244.84.127.254244.84.127.25532,766
170244.84.128.0/17244.84.128.1 to 244.84.255.254244.84.255.25532,766
171244.85.0.0/17244.85.0.1 to 244.85.127.254244.85.127.25532,766
172244.85.128.0/17244.85.128.1 to 244.85.255.254244.85.255.25532,766
173244.86.0.0/17244.86.0.1 to 244.86.127.254244.86.127.25532,766
174244.86.128.0/17244.86.128.1 to 244.86.255.254244.86.255.25532,766
175244.87.0.0/17244.87.0.1 to 244.87.127.254244.87.127.25532,766
176244.87.128.0/17244.87.128.1 to 244.87.255.254244.87.255.25532,766
177244.88.0.0/17244.88.0.1 to 244.88.127.254244.88.127.25532,766
178244.88.128.0/17244.88.128.1 to 244.88.255.254244.88.255.25532,766
179244.89.0.0/17244.89.0.1 to 244.89.127.254244.89.127.25532,766
180244.89.128.0/17244.89.128.1 to 244.89.255.254244.89.255.25532,766
181244.90.0.0/17244.90.0.1 to 244.90.127.254244.90.127.25532,766
182244.90.128.0/17244.90.128.1 to 244.90.255.254244.90.255.25532,766
183244.91.0.0/17244.91.0.1 to 244.91.127.254244.91.127.25532,766
184244.91.128.0/17244.91.128.1 to 244.91.255.254244.91.255.25532,766
185244.92.0.0/17244.92.0.1 to 244.92.127.254244.92.127.25532,766
186244.92.128.0/17244.92.128.1 to 244.92.255.254244.92.255.25532,766
187244.93.0.0/17244.93.0.1 to 244.93.127.254244.93.127.25532,766
188244.93.128.0/17244.93.128.1 to 244.93.255.254244.93.255.25532,766
189244.94.0.0/17244.94.0.1 to 244.94.127.254244.94.127.25532,766
190244.94.128.0/17244.94.128.1 to 244.94.255.254244.94.255.25532,766
191244.95.0.0/17244.95.0.1 to 244.95.127.254244.95.127.25532,766
192244.95.128.0/17244.95.128.1 to 244.95.255.254244.95.255.25532,766
193244.96.0.0/17244.96.0.1 to 244.96.127.254244.96.127.25532,766
194244.96.128.0/17244.96.128.1 to 244.96.255.254244.96.255.25532,766
195244.97.0.0/17244.97.0.1 to 244.97.127.254244.97.127.25532,766
196244.97.128.0/17244.97.128.1 to 244.97.255.254244.97.255.25532,766
197244.98.0.0/17244.98.0.1 to 244.98.127.254244.98.127.25532,766
198244.98.128.0/17244.98.128.1 to 244.98.255.254244.98.255.25532,766
199244.99.0.0/17244.99.0.1 to 244.99.127.254244.99.127.25532,766
200244.99.128.0/17244.99.128.1 to 244.99.255.254244.99.255.25532,766
201244.100.0.0/17244.100.0.1 to 244.100.127.254244.100.127.25532,766
202244.100.128.0/17244.100.128.1 to 244.100.255.254244.100.255.25532,766
203244.101.0.0/17244.101.0.1 to 244.101.127.254244.101.127.25532,766
204244.101.128.0/17244.101.128.1 to 244.101.255.254244.101.255.25532,766
205244.102.0.0/17244.102.0.1 to 244.102.127.254244.102.127.25532,766
206244.102.128.0/17244.102.128.1 to 244.102.255.254244.102.255.25532,766
207244.103.0.0/17244.103.0.1 to 244.103.127.254244.103.127.25532,766
208244.103.128.0/17244.103.128.1 to 244.103.255.254244.103.255.25532,766
209244.104.0.0/17244.104.0.1 to 244.104.127.254244.104.127.25532,766
210244.104.128.0/17244.104.128.1 to 244.104.255.254244.104.255.25532,766
211244.105.0.0/17244.105.0.1 to 244.105.127.254244.105.127.25532,766
212244.105.128.0/17244.105.128.1 to 244.105.255.254244.105.255.25532,766
213244.106.0.0/17244.106.0.1 to 244.106.127.254244.106.127.25532,766
214244.106.128.0/17244.106.128.1 to 244.106.255.254244.106.255.25532,766
215244.107.0.0/17244.107.0.1 to 244.107.127.254244.107.127.25532,766
216244.107.128.0/17244.107.128.1 to 244.107.255.254244.107.255.25532,766
217244.108.0.0/17244.108.0.1 to 244.108.127.254244.108.127.25532,766
218244.108.128.0/17244.108.128.1 to 244.108.255.254244.108.255.25532,766
219244.109.0.0/17244.109.0.1 to 244.109.127.254244.109.127.25532,766
220244.109.128.0/17244.109.128.1 to 244.109.255.254244.109.255.25532,766
221244.110.0.0/17244.110.0.1 to 244.110.127.254244.110.127.25532,766
222244.110.128.0/17244.110.128.1 to 244.110.255.254244.110.255.25532,766
223244.111.0.0/17244.111.0.1 to 244.111.127.254244.111.127.25532,766
224244.111.128.0/17244.111.128.1 to 244.111.255.254244.111.255.25532,766
225244.112.0.0/17244.112.0.1 to 244.112.127.254244.112.127.25532,766
226244.112.128.0/17244.112.128.1 to 244.112.255.254244.112.255.25532,766
227244.113.0.0/17244.113.0.1 to 244.113.127.254244.113.127.25532,766
228244.113.128.0/17244.113.128.1 to 244.113.255.254244.113.255.25532,766
229244.114.0.0/17244.114.0.1 to 244.114.127.254244.114.127.25532,766
230244.114.128.0/17244.114.128.1 to 244.114.255.254244.114.255.25532,766
231244.115.0.0/17244.115.0.1 to 244.115.127.254244.115.127.25532,766
232244.115.128.0/17244.115.128.1 to 244.115.255.254244.115.255.25532,766
233244.116.0.0/17244.116.0.1 to 244.116.127.254244.116.127.25532,766
234244.116.128.0/17244.116.128.1 to 244.116.255.254244.116.255.25532,766
235244.117.0.0/17244.117.0.1 to 244.117.127.254244.117.127.25532,766
236244.117.128.0/17244.117.128.1 to 244.117.255.254244.117.255.25532,766
237244.118.0.0/17244.118.0.1 to 244.118.127.254244.118.127.25532,766
238244.118.128.0/17244.118.128.1 to 244.118.255.254244.118.255.25532,766
239244.119.0.0/17244.119.0.1 to 244.119.127.254244.119.127.25532,766
240244.119.128.0/17244.119.128.1 to 244.119.255.254244.119.255.25532,766
241244.120.0.0/17244.120.0.1 to 244.120.127.254244.120.127.25532,766
242244.120.128.0/17244.120.128.1 to 244.120.255.254244.120.255.25532,766
243244.121.0.0/17244.121.0.1 to 244.121.127.254244.121.127.25532,766
244244.121.128.0/17244.121.128.1 to 244.121.255.254244.121.255.25532,766
245244.122.0.0/17244.122.0.1 to 244.122.127.254244.122.127.25532,766
246244.122.128.0/17244.122.128.1 to 244.122.255.254244.122.255.25532,766
247244.123.0.0/17244.123.0.1 to 244.123.127.254244.123.127.25532,766
248244.123.128.0/17244.123.128.1 to 244.123.255.254244.123.255.25532,766
249244.124.0.0/17244.124.0.1 to 244.124.127.254244.124.127.25532,766
250244.124.128.0/17244.124.128.1 to 244.124.255.254244.124.255.25532,766
251244.125.0.0/17244.125.0.1 to 244.125.127.254244.125.127.25532,766
252244.125.128.0/17244.125.128.1 to 244.125.255.254244.125.255.25532,766
253244.126.0.0/17244.126.0.1 to 244.126.127.254244.126.127.25532,766
254244.126.128.0/17244.126.128.1 to 244.126.255.254244.126.255.25532,766
255244.127.0.0/17244.127.0.1 to 244.127.127.254244.127.127.25532,766
256244.127.128.0/17244.127.128.1 to 244.127.255.254244.127.255.25532,766

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.