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.

Network228.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
228.0.0.0
Broadcast address
228.127.255.255
First usable
228.0.0.1
Last usable
228.127.255.254
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
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex E4000000 · Integer 3825205248 to 3833593855
Reverse DNS zones
0.228.in-addr.arpa
1.228.in-addr.arpa
2.228.in-addr.arpa
3.228.in-addr.arpa
4.228.in-addr.arpa
5.228.in-addr.arpa
6.228.in-addr.arpa
7.228.in-addr.arpa
8.228.in-addr.arpa
9.228.in-addr.arpa
10.228.in-addr.arpa
11.228.in-addr.arpa
12.228.in-addr.arpa
13.228.in-addr.arpa
14.228.in-addr.arpa
15.228.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
Address11100100.00000000.00000000.00000000228.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network11100100.00000000.00000000.00000000228.0.0.0
Broadcast11100100.01111111.11111111.11111111228.127.255.255
Split into smaller subnets/17
/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)

228.0.0.0/9 makes 256 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1228.0.0.0/17228.0.0.1 to 228.0.127.254228.0.127.25532,766
2228.0.128.0/17228.0.128.1 to 228.0.255.254228.0.255.25532,766
3228.1.0.0/17228.1.0.1 to 228.1.127.254228.1.127.25532,766
4228.1.128.0/17228.1.128.1 to 228.1.255.254228.1.255.25532,766
5228.2.0.0/17228.2.0.1 to 228.2.127.254228.2.127.25532,766
6228.2.128.0/17228.2.128.1 to 228.2.255.254228.2.255.25532,766
7228.3.0.0/17228.3.0.1 to 228.3.127.254228.3.127.25532,766
8228.3.128.0/17228.3.128.1 to 228.3.255.254228.3.255.25532,766
9228.4.0.0/17228.4.0.1 to 228.4.127.254228.4.127.25532,766
10228.4.128.0/17228.4.128.1 to 228.4.255.254228.4.255.25532,766
11228.5.0.0/17228.5.0.1 to 228.5.127.254228.5.127.25532,766
12228.5.128.0/17228.5.128.1 to 228.5.255.254228.5.255.25532,766
13228.6.0.0/17228.6.0.1 to 228.6.127.254228.6.127.25532,766
14228.6.128.0/17228.6.128.1 to 228.6.255.254228.6.255.25532,766
15228.7.0.0/17228.7.0.1 to 228.7.127.254228.7.127.25532,766
16228.7.128.0/17228.7.128.1 to 228.7.255.254228.7.255.25532,766
17228.8.0.0/17228.8.0.1 to 228.8.127.254228.8.127.25532,766
18228.8.128.0/17228.8.128.1 to 228.8.255.254228.8.255.25532,766
19228.9.0.0/17228.9.0.1 to 228.9.127.254228.9.127.25532,766
20228.9.128.0/17228.9.128.1 to 228.9.255.254228.9.255.25532,766
21228.10.0.0/17228.10.0.1 to 228.10.127.254228.10.127.25532,766
22228.10.128.0/17228.10.128.1 to 228.10.255.254228.10.255.25532,766
23228.11.0.0/17228.11.0.1 to 228.11.127.254228.11.127.25532,766
24228.11.128.0/17228.11.128.1 to 228.11.255.254228.11.255.25532,766
25228.12.0.0/17228.12.0.1 to 228.12.127.254228.12.127.25532,766
26228.12.128.0/17228.12.128.1 to 228.12.255.254228.12.255.25532,766
27228.13.0.0/17228.13.0.1 to 228.13.127.254228.13.127.25532,766
28228.13.128.0/17228.13.128.1 to 228.13.255.254228.13.255.25532,766
29228.14.0.0/17228.14.0.1 to 228.14.127.254228.14.127.25532,766
30228.14.128.0/17228.14.128.1 to 228.14.255.254228.14.255.25532,766
31228.15.0.0/17228.15.0.1 to 228.15.127.254228.15.127.25532,766
32228.15.128.0/17228.15.128.1 to 228.15.255.254228.15.255.25532,766
33228.16.0.0/17228.16.0.1 to 228.16.127.254228.16.127.25532,766
34228.16.128.0/17228.16.128.1 to 228.16.255.254228.16.255.25532,766
35228.17.0.0/17228.17.0.1 to 228.17.127.254228.17.127.25532,766
36228.17.128.0/17228.17.128.1 to 228.17.255.254228.17.255.25532,766
37228.18.0.0/17228.18.0.1 to 228.18.127.254228.18.127.25532,766
38228.18.128.0/17228.18.128.1 to 228.18.255.254228.18.255.25532,766
39228.19.0.0/17228.19.0.1 to 228.19.127.254228.19.127.25532,766
40228.19.128.0/17228.19.128.1 to 228.19.255.254228.19.255.25532,766
41228.20.0.0/17228.20.0.1 to 228.20.127.254228.20.127.25532,766
42228.20.128.0/17228.20.128.1 to 228.20.255.254228.20.255.25532,766
43228.21.0.0/17228.21.0.1 to 228.21.127.254228.21.127.25532,766
44228.21.128.0/17228.21.128.1 to 228.21.255.254228.21.255.25532,766
45228.22.0.0/17228.22.0.1 to 228.22.127.254228.22.127.25532,766
46228.22.128.0/17228.22.128.1 to 228.22.255.254228.22.255.25532,766
47228.23.0.0/17228.23.0.1 to 228.23.127.254228.23.127.25532,766
48228.23.128.0/17228.23.128.1 to 228.23.255.254228.23.255.25532,766
49228.24.0.0/17228.24.0.1 to 228.24.127.254228.24.127.25532,766
50228.24.128.0/17228.24.128.1 to 228.24.255.254228.24.255.25532,766
51228.25.0.0/17228.25.0.1 to 228.25.127.254228.25.127.25532,766
52228.25.128.0/17228.25.128.1 to 228.25.255.254228.25.255.25532,766
53228.26.0.0/17228.26.0.1 to 228.26.127.254228.26.127.25532,766
54228.26.128.0/17228.26.128.1 to 228.26.255.254228.26.255.25532,766
55228.27.0.0/17228.27.0.1 to 228.27.127.254228.27.127.25532,766
56228.27.128.0/17228.27.128.1 to 228.27.255.254228.27.255.25532,766
57228.28.0.0/17228.28.0.1 to 228.28.127.254228.28.127.25532,766
58228.28.128.0/17228.28.128.1 to 228.28.255.254228.28.255.25532,766
59228.29.0.0/17228.29.0.1 to 228.29.127.254228.29.127.25532,766
60228.29.128.0/17228.29.128.1 to 228.29.255.254228.29.255.25532,766
61228.30.0.0/17228.30.0.1 to 228.30.127.254228.30.127.25532,766
62228.30.128.0/17228.30.128.1 to 228.30.255.254228.30.255.25532,766
63228.31.0.0/17228.31.0.1 to 228.31.127.254228.31.127.25532,766
64228.31.128.0/17228.31.128.1 to 228.31.255.254228.31.255.25532,766
65228.32.0.0/17228.32.0.1 to 228.32.127.254228.32.127.25532,766
66228.32.128.0/17228.32.128.1 to 228.32.255.254228.32.255.25532,766
67228.33.0.0/17228.33.0.1 to 228.33.127.254228.33.127.25532,766
68228.33.128.0/17228.33.128.1 to 228.33.255.254228.33.255.25532,766
69228.34.0.0/17228.34.0.1 to 228.34.127.254228.34.127.25532,766
70228.34.128.0/17228.34.128.1 to 228.34.255.254228.34.255.25532,766
71228.35.0.0/17228.35.0.1 to 228.35.127.254228.35.127.25532,766
72228.35.128.0/17228.35.128.1 to 228.35.255.254228.35.255.25532,766
73228.36.0.0/17228.36.0.1 to 228.36.127.254228.36.127.25532,766
74228.36.128.0/17228.36.128.1 to 228.36.255.254228.36.255.25532,766
75228.37.0.0/17228.37.0.1 to 228.37.127.254228.37.127.25532,766
76228.37.128.0/17228.37.128.1 to 228.37.255.254228.37.255.25532,766
77228.38.0.0/17228.38.0.1 to 228.38.127.254228.38.127.25532,766
78228.38.128.0/17228.38.128.1 to 228.38.255.254228.38.255.25532,766
79228.39.0.0/17228.39.0.1 to 228.39.127.254228.39.127.25532,766
80228.39.128.0/17228.39.128.1 to 228.39.255.254228.39.255.25532,766
81228.40.0.0/17228.40.0.1 to 228.40.127.254228.40.127.25532,766
82228.40.128.0/17228.40.128.1 to 228.40.255.254228.40.255.25532,766
83228.41.0.0/17228.41.0.1 to 228.41.127.254228.41.127.25532,766
84228.41.128.0/17228.41.128.1 to 228.41.255.254228.41.255.25532,766
85228.42.0.0/17228.42.0.1 to 228.42.127.254228.42.127.25532,766
86228.42.128.0/17228.42.128.1 to 228.42.255.254228.42.255.25532,766
87228.43.0.0/17228.43.0.1 to 228.43.127.254228.43.127.25532,766
88228.43.128.0/17228.43.128.1 to 228.43.255.254228.43.255.25532,766
89228.44.0.0/17228.44.0.1 to 228.44.127.254228.44.127.25532,766
90228.44.128.0/17228.44.128.1 to 228.44.255.254228.44.255.25532,766
91228.45.0.0/17228.45.0.1 to 228.45.127.254228.45.127.25532,766
92228.45.128.0/17228.45.128.1 to 228.45.255.254228.45.255.25532,766
93228.46.0.0/17228.46.0.1 to 228.46.127.254228.46.127.25532,766
94228.46.128.0/17228.46.128.1 to 228.46.255.254228.46.255.25532,766
95228.47.0.0/17228.47.0.1 to 228.47.127.254228.47.127.25532,766
96228.47.128.0/17228.47.128.1 to 228.47.255.254228.47.255.25532,766
97228.48.0.0/17228.48.0.1 to 228.48.127.254228.48.127.25532,766
98228.48.128.0/17228.48.128.1 to 228.48.255.254228.48.255.25532,766
99228.49.0.0/17228.49.0.1 to 228.49.127.254228.49.127.25532,766
100228.49.128.0/17228.49.128.1 to 228.49.255.254228.49.255.25532,766
101228.50.0.0/17228.50.0.1 to 228.50.127.254228.50.127.25532,766
102228.50.128.0/17228.50.128.1 to 228.50.255.254228.50.255.25532,766
103228.51.0.0/17228.51.0.1 to 228.51.127.254228.51.127.25532,766
104228.51.128.0/17228.51.128.1 to 228.51.255.254228.51.255.25532,766
105228.52.0.0/17228.52.0.1 to 228.52.127.254228.52.127.25532,766
106228.52.128.0/17228.52.128.1 to 228.52.255.254228.52.255.25532,766
107228.53.0.0/17228.53.0.1 to 228.53.127.254228.53.127.25532,766
108228.53.128.0/17228.53.128.1 to 228.53.255.254228.53.255.25532,766
109228.54.0.0/17228.54.0.1 to 228.54.127.254228.54.127.25532,766
110228.54.128.0/17228.54.128.1 to 228.54.255.254228.54.255.25532,766
111228.55.0.0/17228.55.0.1 to 228.55.127.254228.55.127.25532,766
112228.55.128.0/17228.55.128.1 to 228.55.255.254228.55.255.25532,766
113228.56.0.0/17228.56.0.1 to 228.56.127.254228.56.127.25532,766
114228.56.128.0/17228.56.128.1 to 228.56.255.254228.56.255.25532,766
115228.57.0.0/17228.57.0.1 to 228.57.127.254228.57.127.25532,766
116228.57.128.0/17228.57.128.1 to 228.57.255.254228.57.255.25532,766
117228.58.0.0/17228.58.0.1 to 228.58.127.254228.58.127.25532,766
118228.58.128.0/17228.58.128.1 to 228.58.255.254228.58.255.25532,766
119228.59.0.0/17228.59.0.1 to 228.59.127.254228.59.127.25532,766
120228.59.128.0/17228.59.128.1 to 228.59.255.254228.59.255.25532,766
121228.60.0.0/17228.60.0.1 to 228.60.127.254228.60.127.25532,766
122228.60.128.0/17228.60.128.1 to 228.60.255.254228.60.255.25532,766
123228.61.0.0/17228.61.0.1 to 228.61.127.254228.61.127.25532,766
124228.61.128.0/17228.61.128.1 to 228.61.255.254228.61.255.25532,766
125228.62.0.0/17228.62.0.1 to 228.62.127.254228.62.127.25532,766
126228.62.128.0/17228.62.128.1 to 228.62.255.254228.62.255.25532,766
127228.63.0.0/17228.63.0.1 to 228.63.127.254228.63.127.25532,766
128228.63.128.0/17228.63.128.1 to 228.63.255.254228.63.255.25532,766
129228.64.0.0/17228.64.0.1 to 228.64.127.254228.64.127.25532,766
130228.64.128.0/17228.64.128.1 to 228.64.255.254228.64.255.25532,766
131228.65.0.0/17228.65.0.1 to 228.65.127.254228.65.127.25532,766
132228.65.128.0/17228.65.128.1 to 228.65.255.254228.65.255.25532,766
133228.66.0.0/17228.66.0.1 to 228.66.127.254228.66.127.25532,766
134228.66.128.0/17228.66.128.1 to 228.66.255.254228.66.255.25532,766
135228.67.0.0/17228.67.0.1 to 228.67.127.254228.67.127.25532,766
136228.67.128.0/17228.67.128.1 to 228.67.255.254228.67.255.25532,766
137228.68.0.0/17228.68.0.1 to 228.68.127.254228.68.127.25532,766
138228.68.128.0/17228.68.128.1 to 228.68.255.254228.68.255.25532,766
139228.69.0.0/17228.69.0.1 to 228.69.127.254228.69.127.25532,766
140228.69.128.0/17228.69.128.1 to 228.69.255.254228.69.255.25532,766
141228.70.0.0/17228.70.0.1 to 228.70.127.254228.70.127.25532,766
142228.70.128.0/17228.70.128.1 to 228.70.255.254228.70.255.25532,766
143228.71.0.0/17228.71.0.1 to 228.71.127.254228.71.127.25532,766
144228.71.128.0/17228.71.128.1 to 228.71.255.254228.71.255.25532,766
145228.72.0.0/17228.72.0.1 to 228.72.127.254228.72.127.25532,766
146228.72.128.0/17228.72.128.1 to 228.72.255.254228.72.255.25532,766
147228.73.0.0/17228.73.0.1 to 228.73.127.254228.73.127.25532,766
148228.73.128.0/17228.73.128.1 to 228.73.255.254228.73.255.25532,766
149228.74.0.0/17228.74.0.1 to 228.74.127.254228.74.127.25532,766
150228.74.128.0/17228.74.128.1 to 228.74.255.254228.74.255.25532,766
151228.75.0.0/17228.75.0.1 to 228.75.127.254228.75.127.25532,766
152228.75.128.0/17228.75.128.1 to 228.75.255.254228.75.255.25532,766
153228.76.0.0/17228.76.0.1 to 228.76.127.254228.76.127.25532,766
154228.76.128.0/17228.76.128.1 to 228.76.255.254228.76.255.25532,766
155228.77.0.0/17228.77.0.1 to 228.77.127.254228.77.127.25532,766
156228.77.128.0/17228.77.128.1 to 228.77.255.254228.77.255.25532,766
157228.78.0.0/17228.78.0.1 to 228.78.127.254228.78.127.25532,766
158228.78.128.0/17228.78.128.1 to 228.78.255.254228.78.255.25532,766
159228.79.0.0/17228.79.0.1 to 228.79.127.254228.79.127.25532,766
160228.79.128.0/17228.79.128.1 to 228.79.255.254228.79.255.25532,766
161228.80.0.0/17228.80.0.1 to 228.80.127.254228.80.127.25532,766
162228.80.128.0/17228.80.128.1 to 228.80.255.254228.80.255.25532,766
163228.81.0.0/17228.81.0.1 to 228.81.127.254228.81.127.25532,766
164228.81.128.0/17228.81.128.1 to 228.81.255.254228.81.255.25532,766
165228.82.0.0/17228.82.0.1 to 228.82.127.254228.82.127.25532,766
166228.82.128.0/17228.82.128.1 to 228.82.255.254228.82.255.25532,766
167228.83.0.0/17228.83.0.1 to 228.83.127.254228.83.127.25532,766
168228.83.128.0/17228.83.128.1 to 228.83.255.254228.83.255.25532,766
169228.84.0.0/17228.84.0.1 to 228.84.127.254228.84.127.25532,766
170228.84.128.0/17228.84.128.1 to 228.84.255.254228.84.255.25532,766
171228.85.0.0/17228.85.0.1 to 228.85.127.254228.85.127.25532,766
172228.85.128.0/17228.85.128.1 to 228.85.255.254228.85.255.25532,766
173228.86.0.0/17228.86.0.1 to 228.86.127.254228.86.127.25532,766
174228.86.128.0/17228.86.128.1 to 228.86.255.254228.86.255.25532,766
175228.87.0.0/17228.87.0.1 to 228.87.127.254228.87.127.25532,766
176228.87.128.0/17228.87.128.1 to 228.87.255.254228.87.255.25532,766
177228.88.0.0/17228.88.0.1 to 228.88.127.254228.88.127.25532,766
178228.88.128.0/17228.88.128.1 to 228.88.255.254228.88.255.25532,766
179228.89.0.0/17228.89.0.1 to 228.89.127.254228.89.127.25532,766
180228.89.128.0/17228.89.128.1 to 228.89.255.254228.89.255.25532,766
181228.90.0.0/17228.90.0.1 to 228.90.127.254228.90.127.25532,766
182228.90.128.0/17228.90.128.1 to 228.90.255.254228.90.255.25532,766
183228.91.0.0/17228.91.0.1 to 228.91.127.254228.91.127.25532,766
184228.91.128.0/17228.91.128.1 to 228.91.255.254228.91.255.25532,766
185228.92.0.0/17228.92.0.1 to 228.92.127.254228.92.127.25532,766
186228.92.128.0/17228.92.128.1 to 228.92.255.254228.92.255.25532,766
187228.93.0.0/17228.93.0.1 to 228.93.127.254228.93.127.25532,766
188228.93.128.0/17228.93.128.1 to 228.93.255.254228.93.255.25532,766
189228.94.0.0/17228.94.0.1 to 228.94.127.254228.94.127.25532,766
190228.94.128.0/17228.94.128.1 to 228.94.255.254228.94.255.25532,766
191228.95.0.0/17228.95.0.1 to 228.95.127.254228.95.127.25532,766
192228.95.128.0/17228.95.128.1 to 228.95.255.254228.95.255.25532,766
193228.96.0.0/17228.96.0.1 to 228.96.127.254228.96.127.25532,766
194228.96.128.0/17228.96.128.1 to 228.96.255.254228.96.255.25532,766
195228.97.0.0/17228.97.0.1 to 228.97.127.254228.97.127.25532,766
196228.97.128.0/17228.97.128.1 to 228.97.255.254228.97.255.25532,766
197228.98.0.0/17228.98.0.1 to 228.98.127.254228.98.127.25532,766
198228.98.128.0/17228.98.128.1 to 228.98.255.254228.98.255.25532,766
199228.99.0.0/17228.99.0.1 to 228.99.127.254228.99.127.25532,766
200228.99.128.0/17228.99.128.1 to 228.99.255.254228.99.255.25532,766
201228.100.0.0/17228.100.0.1 to 228.100.127.254228.100.127.25532,766
202228.100.128.0/17228.100.128.1 to 228.100.255.254228.100.255.25532,766
203228.101.0.0/17228.101.0.1 to 228.101.127.254228.101.127.25532,766
204228.101.128.0/17228.101.128.1 to 228.101.255.254228.101.255.25532,766
205228.102.0.0/17228.102.0.1 to 228.102.127.254228.102.127.25532,766
206228.102.128.0/17228.102.128.1 to 228.102.255.254228.102.255.25532,766
207228.103.0.0/17228.103.0.1 to 228.103.127.254228.103.127.25532,766
208228.103.128.0/17228.103.128.1 to 228.103.255.254228.103.255.25532,766
209228.104.0.0/17228.104.0.1 to 228.104.127.254228.104.127.25532,766
210228.104.128.0/17228.104.128.1 to 228.104.255.254228.104.255.25532,766
211228.105.0.0/17228.105.0.1 to 228.105.127.254228.105.127.25532,766
212228.105.128.0/17228.105.128.1 to 228.105.255.254228.105.255.25532,766
213228.106.0.0/17228.106.0.1 to 228.106.127.254228.106.127.25532,766
214228.106.128.0/17228.106.128.1 to 228.106.255.254228.106.255.25532,766
215228.107.0.0/17228.107.0.1 to 228.107.127.254228.107.127.25532,766
216228.107.128.0/17228.107.128.1 to 228.107.255.254228.107.255.25532,766
217228.108.0.0/17228.108.0.1 to 228.108.127.254228.108.127.25532,766
218228.108.128.0/17228.108.128.1 to 228.108.255.254228.108.255.25532,766
219228.109.0.0/17228.109.0.1 to 228.109.127.254228.109.127.25532,766
220228.109.128.0/17228.109.128.1 to 228.109.255.254228.109.255.25532,766
221228.110.0.0/17228.110.0.1 to 228.110.127.254228.110.127.25532,766
222228.110.128.0/17228.110.128.1 to 228.110.255.254228.110.255.25532,766
223228.111.0.0/17228.111.0.1 to 228.111.127.254228.111.127.25532,766
224228.111.128.0/17228.111.128.1 to 228.111.255.254228.111.255.25532,766
225228.112.0.0/17228.112.0.1 to 228.112.127.254228.112.127.25532,766
226228.112.128.0/17228.112.128.1 to 228.112.255.254228.112.255.25532,766
227228.113.0.0/17228.113.0.1 to 228.113.127.254228.113.127.25532,766
228228.113.128.0/17228.113.128.1 to 228.113.255.254228.113.255.25532,766
229228.114.0.0/17228.114.0.1 to 228.114.127.254228.114.127.25532,766
230228.114.128.0/17228.114.128.1 to 228.114.255.254228.114.255.25532,766
231228.115.0.0/17228.115.0.1 to 228.115.127.254228.115.127.25532,766
232228.115.128.0/17228.115.128.1 to 228.115.255.254228.115.255.25532,766
233228.116.0.0/17228.116.0.1 to 228.116.127.254228.116.127.25532,766
234228.116.128.0/17228.116.128.1 to 228.116.255.254228.116.255.25532,766
235228.117.0.0/17228.117.0.1 to 228.117.127.254228.117.127.25532,766
236228.117.128.0/17228.117.128.1 to 228.117.255.254228.117.255.25532,766
237228.118.0.0/17228.118.0.1 to 228.118.127.254228.118.127.25532,766
238228.118.128.0/17228.118.128.1 to 228.118.255.254228.118.255.25532,766
239228.119.0.0/17228.119.0.1 to 228.119.127.254228.119.127.25532,766
240228.119.128.0/17228.119.128.1 to 228.119.255.254228.119.255.25532,766
241228.120.0.0/17228.120.0.1 to 228.120.127.254228.120.127.25532,766
242228.120.128.0/17228.120.128.1 to 228.120.255.254228.120.255.25532,766
243228.121.0.0/17228.121.0.1 to 228.121.127.254228.121.127.25532,766
244228.121.128.0/17228.121.128.1 to 228.121.255.254228.121.255.25532,766
245228.122.0.0/17228.122.0.1 to 228.122.127.254228.122.127.25532,766
246228.122.128.0/17228.122.128.1 to 228.122.255.254228.122.255.25532,766
247228.123.0.0/17228.123.0.1 to 228.123.127.254228.123.127.25532,766
248228.123.128.0/17228.123.128.1 to 228.123.255.254228.123.255.25532,766
249228.124.0.0/17228.124.0.1 to 228.124.127.254228.124.127.25532,766
250228.124.128.0/17228.124.128.1 to 228.124.255.254228.124.255.25532,766
251228.125.0.0/17228.125.0.1 to 228.125.127.254228.125.127.25532,766
252228.125.128.0/17228.125.128.1 to 228.125.255.254228.125.255.25532,766
253228.126.0.0/17228.126.0.1 to 228.126.127.254228.126.127.25532,766
254228.126.128.0/17228.126.128.1 to 228.126.255.254228.126.255.25532,766
255228.127.0.0/17228.127.0.1 to 228.127.127.254228.127.127.25532,766
256228.127.128.0/17228.127.128.1 to 228.127.255.254228.127.255.25532,766

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.