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.

Network166.64.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
166.64.0.0
Broadcast address
166.127.255.255
First usable
166.64.0.1
Last usable
166.127.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Public public
Old class
B (default /16)
As numbers
Hex A6400000 · Integer 2789212160 to 2793406463
Reverse DNS zones
64.166.in-addr.arpa
65.166.in-addr.arpa
66.166.in-addr.arpa
67.166.in-addr.arpa
68.166.in-addr.arpa
69.166.in-addr.arpa
70.166.in-addr.arpa
71.166.in-addr.arpa
72.166.in-addr.arpa
73.166.in-addr.arpa
74.166.in-addr.arpa
75.166.in-addr.arpa
76.166.in-addr.arpa
77.166.in-addr.arpa
78.166.in-addr.arpa
79.166.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100110.01000000.00000000.00000000166.64.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network10100110.01000000.00000000.00000000166.64.0.0
Broadcast10100110.01111111.11111111.11111111166.127.255.255
Split into smaller subnets/19
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

166.64.0.0/10 makes 512 subnets of /19; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1166.64.0.0/19166.64.0.1 to 166.64.31.254166.64.31.2558,190
2166.64.32.0/19166.64.32.1 to 166.64.63.254166.64.63.2558,190
3166.64.64.0/19166.64.64.1 to 166.64.95.254166.64.95.2558,190
4166.64.96.0/19166.64.96.1 to 166.64.127.254166.64.127.2558,190
5166.64.128.0/19166.64.128.1 to 166.64.159.254166.64.159.2558,190
6166.64.160.0/19166.64.160.1 to 166.64.191.254166.64.191.2558,190
7166.64.192.0/19166.64.192.1 to 166.64.223.254166.64.223.2558,190
8166.64.224.0/19166.64.224.1 to 166.64.255.254166.64.255.2558,190
9166.65.0.0/19166.65.0.1 to 166.65.31.254166.65.31.2558,190
10166.65.32.0/19166.65.32.1 to 166.65.63.254166.65.63.2558,190
11166.65.64.0/19166.65.64.1 to 166.65.95.254166.65.95.2558,190
12166.65.96.0/19166.65.96.1 to 166.65.127.254166.65.127.2558,190
13166.65.128.0/19166.65.128.1 to 166.65.159.254166.65.159.2558,190
14166.65.160.0/19166.65.160.1 to 166.65.191.254166.65.191.2558,190
15166.65.192.0/19166.65.192.1 to 166.65.223.254166.65.223.2558,190
16166.65.224.0/19166.65.224.1 to 166.65.255.254166.65.255.2558,190
17166.66.0.0/19166.66.0.1 to 166.66.31.254166.66.31.2558,190
18166.66.32.0/19166.66.32.1 to 166.66.63.254166.66.63.2558,190
19166.66.64.0/19166.66.64.1 to 166.66.95.254166.66.95.2558,190
20166.66.96.0/19166.66.96.1 to 166.66.127.254166.66.127.2558,190
21166.66.128.0/19166.66.128.1 to 166.66.159.254166.66.159.2558,190
22166.66.160.0/19166.66.160.1 to 166.66.191.254166.66.191.2558,190
23166.66.192.0/19166.66.192.1 to 166.66.223.254166.66.223.2558,190
24166.66.224.0/19166.66.224.1 to 166.66.255.254166.66.255.2558,190
25166.67.0.0/19166.67.0.1 to 166.67.31.254166.67.31.2558,190
26166.67.32.0/19166.67.32.1 to 166.67.63.254166.67.63.2558,190
27166.67.64.0/19166.67.64.1 to 166.67.95.254166.67.95.2558,190
28166.67.96.0/19166.67.96.1 to 166.67.127.254166.67.127.2558,190
29166.67.128.0/19166.67.128.1 to 166.67.159.254166.67.159.2558,190
30166.67.160.0/19166.67.160.1 to 166.67.191.254166.67.191.2558,190
31166.67.192.0/19166.67.192.1 to 166.67.223.254166.67.223.2558,190
32166.67.224.0/19166.67.224.1 to 166.67.255.254166.67.255.2558,190
33166.68.0.0/19166.68.0.1 to 166.68.31.254166.68.31.2558,190
34166.68.32.0/19166.68.32.1 to 166.68.63.254166.68.63.2558,190
35166.68.64.0/19166.68.64.1 to 166.68.95.254166.68.95.2558,190
36166.68.96.0/19166.68.96.1 to 166.68.127.254166.68.127.2558,190
37166.68.128.0/19166.68.128.1 to 166.68.159.254166.68.159.2558,190
38166.68.160.0/19166.68.160.1 to 166.68.191.254166.68.191.2558,190
39166.68.192.0/19166.68.192.1 to 166.68.223.254166.68.223.2558,190
40166.68.224.0/19166.68.224.1 to 166.68.255.254166.68.255.2558,190
41166.69.0.0/19166.69.0.1 to 166.69.31.254166.69.31.2558,190
42166.69.32.0/19166.69.32.1 to 166.69.63.254166.69.63.2558,190
43166.69.64.0/19166.69.64.1 to 166.69.95.254166.69.95.2558,190
44166.69.96.0/19166.69.96.1 to 166.69.127.254166.69.127.2558,190
45166.69.128.0/19166.69.128.1 to 166.69.159.254166.69.159.2558,190
46166.69.160.0/19166.69.160.1 to 166.69.191.254166.69.191.2558,190
47166.69.192.0/19166.69.192.1 to 166.69.223.254166.69.223.2558,190
48166.69.224.0/19166.69.224.1 to 166.69.255.254166.69.255.2558,190
49166.70.0.0/19166.70.0.1 to 166.70.31.254166.70.31.2558,190
50166.70.32.0/19166.70.32.1 to 166.70.63.254166.70.63.2558,190
51166.70.64.0/19166.70.64.1 to 166.70.95.254166.70.95.2558,190
52166.70.96.0/19166.70.96.1 to 166.70.127.254166.70.127.2558,190
53166.70.128.0/19166.70.128.1 to 166.70.159.254166.70.159.2558,190
54166.70.160.0/19166.70.160.1 to 166.70.191.254166.70.191.2558,190
55166.70.192.0/19166.70.192.1 to 166.70.223.254166.70.223.2558,190
56166.70.224.0/19166.70.224.1 to 166.70.255.254166.70.255.2558,190
57166.71.0.0/19166.71.0.1 to 166.71.31.254166.71.31.2558,190
58166.71.32.0/19166.71.32.1 to 166.71.63.254166.71.63.2558,190
59166.71.64.0/19166.71.64.1 to 166.71.95.254166.71.95.2558,190
60166.71.96.0/19166.71.96.1 to 166.71.127.254166.71.127.2558,190
61166.71.128.0/19166.71.128.1 to 166.71.159.254166.71.159.2558,190
62166.71.160.0/19166.71.160.1 to 166.71.191.254166.71.191.2558,190
63166.71.192.0/19166.71.192.1 to 166.71.223.254166.71.223.2558,190
64166.71.224.0/19166.71.224.1 to 166.71.255.254166.71.255.2558,190
65166.72.0.0/19166.72.0.1 to 166.72.31.254166.72.31.2558,190
66166.72.32.0/19166.72.32.1 to 166.72.63.254166.72.63.2558,190
67166.72.64.0/19166.72.64.1 to 166.72.95.254166.72.95.2558,190
68166.72.96.0/19166.72.96.1 to 166.72.127.254166.72.127.2558,190
69166.72.128.0/19166.72.128.1 to 166.72.159.254166.72.159.2558,190
70166.72.160.0/19166.72.160.1 to 166.72.191.254166.72.191.2558,190
71166.72.192.0/19166.72.192.1 to 166.72.223.254166.72.223.2558,190
72166.72.224.0/19166.72.224.1 to 166.72.255.254166.72.255.2558,190
73166.73.0.0/19166.73.0.1 to 166.73.31.254166.73.31.2558,190
74166.73.32.0/19166.73.32.1 to 166.73.63.254166.73.63.2558,190
75166.73.64.0/19166.73.64.1 to 166.73.95.254166.73.95.2558,190
76166.73.96.0/19166.73.96.1 to 166.73.127.254166.73.127.2558,190
77166.73.128.0/19166.73.128.1 to 166.73.159.254166.73.159.2558,190
78166.73.160.0/19166.73.160.1 to 166.73.191.254166.73.191.2558,190
79166.73.192.0/19166.73.192.1 to 166.73.223.254166.73.223.2558,190
80166.73.224.0/19166.73.224.1 to 166.73.255.254166.73.255.2558,190
81166.74.0.0/19166.74.0.1 to 166.74.31.254166.74.31.2558,190
82166.74.32.0/19166.74.32.1 to 166.74.63.254166.74.63.2558,190
83166.74.64.0/19166.74.64.1 to 166.74.95.254166.74.95.2558,190
84166.74.96.0/19166.74.96.1 to 166.74.127.254166.74.127.2558,190
85166.74.128.0/19166.74.128.1 to 166.74.159.254166.74.159.2558,190
86166.74.160.0/19166.74.160.1 to 166.74.191.254166.74.191.2558,190
87166.74.192.0/19166.74.192.1 to 166.74.223.254166.74.223.2558,190
88166.74.224.0/19166.74.224.1 to 166.74.255.254166.74.255.2558,190
89166.75.0.0/19166.75.0.1 to 166.75.31.254166.75.31.2558,190
90166.75.32.0/19166.75.32.1 to 166.75.63.254166.75.63.2558,190
91166.75.64.0/19166.75.64.1 to 166.75.95.254166.75.95.2558,190
92166.75.96.0/19166.75.96.1 to 166.75.127.254166.75.127.2558,190
93166.75.128.0/19166.75.128.1 to 166.75.159.254166.75.159.2558,190
94166.75.160.0/19166.75.160.1 to 166.75.191.254166.75.191.2558,190
95166.75.192.0/19166.75.192.1 to 166.75.223.254166.75.223.2558,190
96166.75.224.0/19166.75.224.1 to 166.75.255.254166.75.255.2558,190
97166.76.0.0/19166.76.0.1 to 166.76.31.254166.76.31.2558,190
98166.76.32.0/19166.76.32.1 to 166.76.63.254166.76.63.2558,190
99166.76.64.0/19166.76.64.1 to 166.76.95.254166.76.95.2558,190
100166.76.96.0/19166.76.96.1 to 166.76.127.254166.76.127.2558,190
101166.76.128.0/19166.76.128.1 to 166.76.159.254166.76.159.2558,190
102166.76.160.0/19166.76.160.1 to 166.76.191.254166.76.191.2558,190
103166.76.192.0/19166.76.192.1 to 166.76.223.254166.76.223.2558,190
104166.76.224.0/19166.76.224.1 to 166.76.255.254166.76.255.2558,190
105166.77.0.0/19166.77.0.1 to 166.77.31.254166.77.31.2558,190
106166.77.32.0/19166.77.32.1 to 166.77.63.254166.77.63.2558,190
107166.77.64.0/19166.77.64.1 to 166.77.95.254166.77.95.2558,190
108166.77.96.0/19166.77.96.1 to 166.77.127.254166.77.127.2558,190
109166.77.128.0/19166.77.128.1 to 166.77.159.254166.77.159.2558,190
110166.77.160.0/19166.77.160.1 to 166.77.191.254166.77.191.2558,190
111166.77.192.0/19166.77.192.1 to 166.77.223.254166.77.223.2558,190
112166.77.224.0/19166.77.224.1 to 166.77.255.254166.77.255.2558,190
113166.78.0.0/19166.78.0.1 to 166.78.31.254166.78.31.2558,190
114166.78.32.0/19166.78.32.1 to 166.78.63.254166.78.63.2558,190
115166.78.64.0/19166.78.64.1 to 166.78.95.254166.78.95.2558,190
116166.78.96.0/19166.78.96.1 to 166.78.127.254166.78.127.2558,190
117166.78.128.0/19166.78.128.1 to 166.78.159.254166.78.159.2558,190
118166.78.160.0/19166.78.160.1 to 166.78.191.254166.78.191.2558,190
119166.78.192.0/19166.78.192.1 to 166.78.223.254166.78.223.2558,190
120166.78.224.0/19166.78.224.1 to 166.78.255.254166.78.255.2558,190
121166.79.0.0/19166.79.0.1 to 166.79.31.254166.79.31.2558,190
122166.79.32.0/19166.79.32.1 to 166.79.63.254166.79.63.2558,190
123166.79.64.0/19166.79.64.1 to 166.79.95.254166.79.95.2558,190
124166.79.96.0/19166.79.96.1 to 166.79.127.254166.79.127.2558,190
125166.79.128.0/19166.79.128.1 to 166.79.159.254166.79.159.2558,190
126166.79.160.0/19166.79.160.1 to 166.79.191.254166.79.191.2558,190
127166.79.192.0/19166.79.192.1 to 166.79.223.254166.79.223.2558,190
128166.79.224.0/19166.79.224.1 to 166.79.255.254166.79.255.2558,190
129166.80.0.0/19166.80.0.1 to 166.80.31.254166.80.31.2558,190
130166.80.32.0/19166.80.32.1 to 166.80.63.254166.80.63.2558,190
131166.80.64.0/19166.80.64.1 to 166.80.95.254166.80.95.2558,190
132166.80.96.0/19166.80.96.1 to 166.80.127.254166.80.127.2558,190
133166.80.128.0/19166.80.128.1 to 166.80.159.254166.80.159.2558,190
134166.80.160.0/19166.80.160.1 to 166.80.191.254166.80.191.2558,190
135166.80.192.0/19166.80.192.1 to 166.80.223.254166.80.223.2558,190
136166.80.224.0/19166.80.224.1 to 166.80.255.254166.80.255.2558,190
137166.81.0.0/19166.81.0.1 to 166.81.31.254166.81.31.2558,190
138166.81.32.0/19166.81.32.1 to 166.81.63.254166.81.63.2558,190
139166.81.64.0/19166.81.64.1 to 166.81.95.254166.81.95.2558,190
140166.81.96.0/19166.81.96.1 to 166.81.127.254166.81.127.2558,190
141166.81.128.0/19166.81.128.1 to 166.81.159.254166.81.159.2558,190
142166.81.160.0/19166.81.160.1 to 166.81.191.254166.81.191.2558,190
143166.81.192.0/19166.81.192.1 to 166.81.223.254166.81.223.2558,190
144166.81.224.0/19166.81.224.1 to 166.81.255.254166.81.255.2558,190
145166.82.0.0/19166.82.0.1 to 166.82.31.254166.82.31.2558,190
146166.82.32.0/19166.82.32.1 to 166.82.63.254166.82.63.2558,190
147166.82.64.0/19166.82.64.1 to 166.82.95.254166.82.95.2558,190
148166.82.96.0/19166.82.96.1 to 166.82.127.254166.82.127.2558,190
149166.82.128.0/19166.82.128.1 to 166.82.159.254166.82.159.2558,190
150166.82.160.0/19166.82.160.1 to 166.82.191.254166.82.191.2558,190
151166.82.192.0/19166.82.192.1 to 166.82.223.254166.82.223.2558,190
152166.82.224.0/19166.82.224.1 to 166.82.255.254166.82.255.2558,190
153166.83.0.0/19166.83.0.1 to 166.83.31.254166.83.31.2558,190
154166.83.32.0/19166.83.32.1 to 166.83.63.254166.83.63.2558,190
155166.83.64.0/19166.83.64.1 to 166.83.95.254166.83.95.2558,190
156166.83.96.0/19166.83.96.1 to 166.83.127.254166.83.127.2558,190
157166.83.128.0/19166.83.128.1 to 166.83.159.254166.83.159.2558,190
158166.83.160.0/19166.83.160.1 to 166.83.191.254166.83.191.2558,190
159166.83.192.0/19166.83.192.1 to 166.83.223.254166.83.223.2558,190
160166.83.224.0/19166.83.224.1 to 166.83.255.254166.83.255.2558,190
161166.84.0.0/19166.84.0.1 to 166.84.31.254166.84.31.2558,190
162166.84.32.0/19166.84.32.1 to 166.84.63.254166.84.63.2558,190
163166.84.64.0/19166.84.64.1 to 166.84.95.254166.84.95.2558,190
164166.84.96.0/19166.84.96.1 to 166.84.127.254166.84.127.2558,190
165166.84.128.0/19166.84.128.1 to 166.84.159.254166.84.159.2558,190
166166.84.160.0/19166.84.160.1 to 166.84.191.254166.84.191.2558,190
167166.84.192.0/19166.84.192.1 to 166.84.223.254166.84.223.2558,190
168166.84.224.0/19166.84.224.1 to 166.84.255.254166.84.255.2558,190
169166.85.0.0/19166.85.0.1 to 166.85.31.254166.85.31.2558,190
170166.85.32.0/19166.85.32.1 to 166.85.63.254166.85.63.2558,190
171166.85.64.0/19166.85.64.1 to 166.85.95.254166.85.95.2558,190
172166.85.96.0/19166.85.96.1 to 166.85.127.254166.85.127.2558,190
173166.85.128.0/19166.85.128.1 to 166.85.159.254166.85.159.2558,190
174166.85.160.0/19166.85.160.1 to 166.85.191.254166.85.191.2558,190
175166.85.192.0/19166.85.192.1 to 166.85.223.254166.85.223.2558,190
176166.85.224.0/19166.85.224.1 to 166.85.255.254166.85.255.2558,190
177166.86.0.0/19166.86.0.1 to 166.86.31.254166.86.31.2558,190
178166.86.32.0/19166.86.32.1 to 166.86.63.254166.86.63.2558,190
179166.86.64.0/19166.86.64.1 to 166.86.95.254166.86.95.2558,190
180166.86.96.0/19166.86.96.1 to 166.86.127.254166.86.127.2558,190
181166.86.128.0/19166.86.128.1 to 166.86.159.254166.86.159.2558,190
182166.86.160.0/19166.86.160.1 to 166.86.191.254166.86.191.2558,190
183166.86.192.0/19166.86.192.1 to 166.86.223.254166.86.223.2558,190
184166.86.224.0/19166.86.224.1 to 166.86.255.254166.86.255.2558,190
185166.87.0.0/19166.87.0.1 to 166.87.31.254166.87.31.2558,190
186166.87.32.0/19166.87.32.1 to 166.87.63.254166.87.63.2558,190
187166.87.64.0/19166.87.64.1 to 166.87.95.254166.87.95.2558,190
188166.87.96.0/19166.87.96.1 to 166.87.127.254166.87.127.2558,190
189166.87.128.0/19166.87.128.1 to 166.87.159.254166.87.159.2558,190
190166.87.160.0/19166.87.160.1 to 166.87.191.254166.87.191.2558,190
191166.87.192.0/19166.87.192.1 to 166.87.223.254166.87.223.2558,190
192166.87.224.0/19166.87.224.1 to 166.87.255.254166.87.255.2558,190
193166.88.0.0/19166.88.0.1 to 166.88.31.254166.88.31.2558,190
194166.88.32.0/19166.88.32.1 to 166.88.63.254166.88.63.2558,190
195166.88.64.0/19166.88.64.1 to 166.88.95.254166.88.95.2558,190
196166.88.96.0/19166.88.96.1 to 166.88.127.254166.88.127.2558,190
197166.88.128.0/19166.88.128.1 to 166.88.159.254166.88.159.2558,190
198166.88.160.0/19166.88.160.1 to 166.88.191.254166.88.191.2558,190
199166.88.192.0/19166.88.192.1 to 166.88.223.254166.88.223.2558,190
200166.88.224.0/19166.88.224.1 to 166.88.255.254166.88.255.2558,190
201166.89.0.0/19166.89.0.1 to 166.89.31.254166.89.31.2558,190
202166.89.32.0/19166.89.32.1 to 166.89.63.254166.89.63.2558,190
203166.89.64.0/19166.89.64.1 to 166.89.95.254166.89.95.2558,190
204166.89.96.0/19166.89.96.1 to 166.89.127.254166.89.127.2558,190
205166.89.128.0/19166.89.128.1 to 166.89.159.254166.89.159.2558,190
206166.89.160.0/19166.89.160.1 to 166.89.191.254166.89.191.2558,190
207166.89.192.0/19166.89.192.1 to 166.89.223.254166.89.223.2558,190
208166.89.224.0/19166.89.224.1 to 166.89.255.254166.89.255.2558,190
209166.90.0.0/19166.90.0.1 to 166.90.31.254166.90.31.2558,190
210166.90.32.0/19166.90.32.1 to 166.90.63.254166.90.63.2558,190
211166.90.64.0/19166.90.64.1 to 166.90.95.254166.90.95.2558,190
212166.90.96.0/19166.90.96.1 to 166.90.127.254166.90.127.2558,190
213166.90.128.0/19166.90.128.1 to 166.90.159.254166.90.159.2558,190
214166.90.160.0/19166.90.160.1 to 166.90.191.254166.90.191.2558,190
215166.90.192.0/19166.90.192.1 to 166.90.223.254166.90.223.2558,190
216166.90.224.0/19166.90.224.1 to 166.90.255.254166.90.255.2558,190
217166.91.0.0/19166.91.0.1 to 166.91.31.254166.91.31.2558,190
218166.91.32.0/19166.91.32.1 to 166.91.63.254166.91.63.2558,190
219166.91.64.0/19166.91.64.1 to 166.91.95.254166.91.95.2558,190
220166.91.96.0/19166.91.96.1 to 166.91.127.254166.91.127.2558,190
221166.91.128.0/19166.91.128.1 to 166.91.159.254166.91.159.2558,190
222166.91.160.0/19166.91.160.1 to 166.91.191.254166.91.191.2558,190
223166.91.192.0/19166.91.192.1 to 166.91.223.254166.91.223.2558,190
224166.91.224.0/19166.91.224.1 to 166.91.255.254166.91.255.2558,190
225166.92.0.0/19166.92.0.1 to 166.92.31.254166.92.31.2558,190
226166.92.32.0/19166.92.32.1 to 166.92.63.254166.92.63.2558,190
227166.92.64.0/19166.92.64.1 to 166.92.95.254166.92.95.2558,190
228166.92.96.0/19166.92.96.1 to 166.92.127.254166.92.127.2558,190
229166.92.128.0/19166.92.128.1 to 166.92.159.254166.92.159.2558,190
230166.92.160.0/19166.92.160.1 to 166.92.191.254166.92.191.2558,190
231166.92.192.0/19166.92.192.1 to 166.92.223.254166.92.223.2558,190
232166.92.224.0/19166.92.224.1 to 166.92.255.254166.92.255.2558,190
233166.93.0.0/19166.93.0.1 to 166.93.31.254166.93.31.2558,190
234166.93.32.0/19166.93.32.1 to 166.93.63.254166.93.63.2558,190
235166.93.64.0/19166.93.64.1 to 166.93.95.254166.93.95.2558,190
236166.93.96.0/19166.93.96.1 to 166.93.127.254166.93.127.2558,190
237166.93.128.0/19166.93.128.1 to 166.93.159.254166.93.159.2558,190
238166.93.160.0/19166.93.160.1 to 166.93.191.254166.93.191.2558,190
239166.93.192.0/19166.93.192.1 to 166.93.223.254166.93.223.2558,190
240166.93.224.0/19166.93.224.1 to 166.93.255.254166.93.255.2558,190
241166.94.0.0/19166.94.0.1 to 166.94.31.254166.94.31.2558,190
242166.94.32.0/19166.94.32.1 to 166.94.63.254166.94.63.2558,190
243166.94.64.0/19166.94.64.1 to 166.94.95.254166.94.95.2558,190
244166.94.96.0/19166.94.96.1 to 166.94.127.254166.94.127.2558,190
245166.94.128.0/19166.94.128.1 to 166.94.159.254166.94.159.2558,190
246166.94.160.0/19166.94.160.1 to 166.94.191.254166.94.191.2558,190
247166.94.192.0/19166.94.192.1 to 166.94.223.254166.94.223.2558,190
248166.94.224.0/19166.94.224.1 to 166.94.255.254166.94.255.2558,190
249166.95.0.0/19166.95.0.1 to 166.95.31.254166.95.31.2558,190
250166.95.32.0/19166.95.32.1 to 166.95.63.254166.95.63.2558,190
251166.95.64.0/19166.95.64.1 to 166.95.95.254166.95.95.2558,190
252166.95.96.0/19166.95.96.1 to 166.95.127.254166.95.127.2558,190
253166.95.128.0/19166.95.128.1 to 166.95.159.254166.95.159.2558,190
254166.95.160.0/19166.95.160.1 to 166.95.191.254166.95.191.2558,190
255166.95.192.0/19166.95.192.1 to 166.95.223.254166.95.223.2558,190
256166.95.224.0/19166.95.224.1 to 166.95.255.254166.95.255.2558,190

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.