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.

Network102.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
102.0.0.0
Broadcast address
102.127.255.255
First usable
102.0.0.1
Last usable
102.127.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Public public
Old class
A (default /8)
As numbers
Hex 66000000 · Integer 1711276032 to 1719664639
Reverse DNS zones
0.102.in-addr.arpa
1.102.in-addr.arpa
2.102.in-addr.arpa
3.102.in-addr.arpa
4.102.in-addr.arpa
5.102.in-addr.arpa
6.102.in-addr.arpa
7.102.in-addr.arpa
8.102.in-addr.arpa
9.102.in-addr.arpa
10.102.in-addr.arpa
11.102.in-addr.arpa
12.102.in-addr.arpa
13.102.in-addr.arpa
14.102.in-addr.arpa
15.102.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
Address01100110.00000000.00000000.00000000102.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network01100110.00000000.00000000.00000000102.0.0.0
Broadcast01100110.01111111.11111111.11111111102.127.255.255
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)

102.0.0.0/9 makes 256 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1102.0.0.0/17102.0.0.1 to 102.0.127.254102.0.127.25532,766
2102.0.128.0/17102.0.128.1 to 102.0.255.254102.0.255.25532,766
3102.1.0.0/17102.1.0.1 to 102.1.127.254102.1.127.25532,766
4102.1.128.0/17102.1.128.1 to 102.1.255.254102.1.255.25532,766
5102.2.0.0/17102.2.0.1 to 102.2.127.254102.2.127.25532,766
6102.2.128.0/17102.2.128.1 to 102.2.255.254102.2.255.25532,766
7102.3.0.0/17102.3.0.1 to 102.3.127.254102.3.127.25532,766
8102.3.128.0/17102.3.128.1 to 102.3.255.254102.3.255.25532,766
9102.4.0.0/17102.4.0.1 to 102.4.127.254102.4.127.25532,766
10102.4.128.0/17102.4.128.1 to 102.4.255.254102.4.255.25532,766
11102.5.0.0/17102.5.0.1 to 102.5.127.254102.5.127.25532,766
12102.5.128.0/17102.5.128.1 to 102.5.255.254102.5.255.25532,766
13102.6.0.0/17102.6.0.1 to 102.6.127.254102.6.127.25532,766
14102.6.128.0/17102.6.128.1 to 102.6.255.254102.6.255.25532,766
15102.7.0.0/17102.7.0.1 to 102.7.127.254102.7.127.25532,766
16102.7.128.0/17102.7.128.1 to 102.7.255.254102.7.255.25532,766
17102.8.0.0/17102.8.0.1 to 102.8.127.254102.8.127.25532,766
18102.8.128.0/17102.8.128.1 to 102.8.255.254102.8.255.25532,766
19102.9.0.0/17102.9.0.1 to 102.9.127.254102.9.127.25532,766
20102.9.128.0/17102.9.128.1 to 102.9.255.254102.9.255.25532,766
21102.10.0.0/17102.10.0.1 to 102.10.127.254102.10.127.25532,766
22102.10.128.0/17102.10.128.1 to 102.10.255.254102.10.255.25532,766
23102.11.0.0/17102.11.0.1 to 102.11.127.254102.11.127.25532,766
24102.11.128.0/17102.11.128.1 to 102.11.255.254102.11.255.25532,766
25102.12.0.0/17102.12.0.1 to 102.12.127.254102.12.127.25532,766
26102.12.128.0/17102.12.128.1 to 102.12.255.254102.12.255.25532,766
27102.13.0.0/17102.13.0.1 to 102.13.127.254102.13.127.25532,766
28102.13.128.0/17102.13.128.1 to 102.13.255.254102.13.255.25532,766
29102.14.0.0/17102.14.0.1 to 102.14.127.254102.14.127.25532,766
30102.14.128.0/17102.14.128.1 to 102.14.255.254102.14.255.25532,766
31102.15.0.0/17102.15.0.1 to 102.15.127.254102.15.127.25532,766
32102.15.128.0/17102.15.128.1 to 102.15.255.254102.15.255.25532,766
33102.16.0.0/17102.16.0.1 to 102.16.127.254102.16.127.25532,766
34102.16.128.0/17102.16.128.1 to 102.16.255.254102.16.255.25532,766
35102.17.0.0/17102.17.0.1 to 102.17.127.254102.17.127.25532,766
36102.17.128.0/17102.17.128.1 to 102.17.255.254102.17.255.25532,766
37102.18.0.0/17102.18.0.1 to 102.18.127.254102.18.127.25532,766
38102.18.128.0/17102.18.128.1 to 102.18.255.254102.18.255.25532,766
39102.19.0.0/17102.19.0.1 to 102.19.127.254102.19.127.25532,766
40102.19.128.0/17102.19.128.1 to 102.19.255.254102.19.255.25532,766
41102.20.0.0/17102.20.0.1 to 102.20.127.254102.20.127.25532,766
42102.20.128.0/17102.20.128.1 to 102.20.255.254102.20.255.25532,766
43102.21.0.0/17102.21.0.1 to 102.21.127.254102.21.127.25532,766
44102.21.128.0/17102.21.128.1 to 102.21.255.254102.21.255.25532,766
45102.22.0.0/17102.22.0.1 to 102.22.127.254102.22.127.25532,766
46102.22.128.0/17102.22.128.1 to 102.22.255.254102.22.255.25532,766
47102.23.0.0/17102.23.0.1 to 102.23.127.254102.23.127.25532,766
48102.23.128.0/17102.23.128.1 to 102.23.255.254102.23.255.25532,766
49102.24.0.0/17102.24.0.1 to 102.24.127.254102.24.127.25532,766
50102.24.128.0/17102.24.128.1 to 102.24.255.254102.24.255.25532,766
51102.25.0.0/17102.25.0.1 to 102.25.127.254102.25.127.25532,766
52102.25.128.0/17102.25.128.1 to 102.25.255.254102.25.255.25532,766
53102.26.0.0/17102.26.0.1 to 102.26.127.254102.26.127.25532,766
54102.26.128.0/17102.26.128.1 to 102.26.255.254102.26.255.25532,766
55102.27.0.0/17102.27.0.1 to 102.27.127.254102.27.127.25532,766
56102.27.128.0/17102.27.128.1 to 102.27.255.254102.27.255.25532,766
57102.28.0.0/17102.28.0.1 to 102.28.127.254102.28.127.25532,766
58102.28.128.0/17102.28.128.1 to 102.28.255.254102.28.255.25532,766
59102.29.0.0/17102.29.0.1 to 102.29.127.254102.29.127.25532,766
60102.29.128.0/17102.29.128.1 to 102.29.255.254102.29.255.25532,766
61102.30.0.0/17102.30.0.1 to 102.30.127.254102.30.127.25532,766
62102.30.128.0/17102.30.128.1 to 102.30.255.254102.30.255.25532,766
63102.31.0.0/17102.31.0.1 to 102.31.127.254102.31.127.25532,766
64102.31.128.0/17102.31.128.1 to 102.31.255.254102.31.255.25532,766
65102.32.0.0/17102.32.0.1 to 102.32.127.254102.32.127.25532,766
66102.32.128.0/17102.32.128.1 to 102.32.255.254102.32.255.25532,766
67102.33.0.0/17102.33.0.1 to 102.33.127.254102.33.127.25532,766
68102.33.128.0/17102.33.128.1 to 102.33.255.254102.33.255.25532,766
69102.34.0.0/17102.34.0.1 to 102.34.127.254102.34.127.25532,766
70102.34.128.0/17102.34.128.1 to 102.34.255.254102.34.255.25532,766
71102.35.0.0/17102.35.0.1 to 102.35.127.254102.35.127.25532,766
72102.35.128.0/17102.35.128.1 to 102.35.255.254102.35.255.25532,766
73102.36.0.0/17102.36.0.1 to 102.36.127.254102.36.127.25532,766
74102.36.128.0/17102.36.128.1 to 102.36.255.254102.36.255.25532,766
75102.37.0.0/17102.37.0.1 to 102.37.127.254102.37.127.25532,766
76102.37.128.0/17102.37.128.1 to 102.37.255.254102.37.255.25532,766
77102.38.0.0/17102.38.0.1 to 102.38.127.254102.38.127.25532,766
78102.38.128.0/17102.38.128.1 to 102.38.255.254102.38.255.25532,766
79102.39.0.0/17102.39.0.1 to 102.39.127.254102.39.127.25532,766
80102.39.128.0/17102.39.128.1 to 102.39.255.254102.39.255.25532,766
81102.40.0.0/17102.40.0.1 to 102.40.127.254102.40.127.25532,766
82102.40.128.0/17102.40.128.1 to 102.40.255.254102.40.255.25532,766
83102.41.0.0/17102.41.0.1 to 102.41.127.254102.41.127.25532,766
84102.41.128.0/17102.41.128.1 to 102.41.255.254102.41.255.25532,766
85102.42.0.0/17102.42.0.1 to 102.42.127.254102.42.127.25532,766
86102.42.128.0/17102.42.128.1 to 102.42.255.254102.42.255.25532,766
87102.43.0.0/17102.43.0.1 to 102.43.127.254102.43.127.25532,766
88102.43.128.0/17102.43.128.1 to 102.43.255.254102.43.255.25532,766
89102.44.0.0/17102.44.0.1 to 102.44.127.254102.44.127.25532,766
90102.44.128.0/17102.44.128.1 to 102.44.255.254102.44.255.25532,766
91102.45.0.0/17102.45.0.1 to 102.45.127.254102.45.127.25532,766
92102.45.128.0/17102.45.128.1 to 102.45.255.254102.45.255.25532,766
93102.46.0.0/17102.46.0.1 to 102.46.127.254102.46.127.25532,766
94102.46.128.0/17102.46.128.1 to 102.46.255.254102.46.255.25532,766
95102.47.0.0/17102.47.0.1 to 102.47.127.254102.47.127.25532,766
96102.47.128.0/17102.47.128.1 to 102.47.255.254102.47.255.25532,766
97102.48.0.0/17102.48.0.1 to 102.48.127.254102.48.127.25532,766
98102.48.128.0/17102.48.128.1 to 102.48.255.254102.48.255.25532,766
99102.49.0.0/17102.49.0.1 to 102.49.127.254102.49.127.25532,766
100102.49.128.0/17102.49.128.1 to 102.49.255.254102.49.255.25532,766
101102.50.0.0/17102.50.0.1 to 102.50.127.254102.50.127.25532,766
102102.50.128.0/17102.50.128.1 to 102.50.255.254102.50.255.25532,766
103102.51.0.0/17102.51.0.1 to 102.51.127.254102.51.127.25532,766
104102.51.128.0/17102.51.128.1 to 102.51.255.254102.51.255.25532,766
105102.52.0.0/17102.52.0.1 to 102.52.127.254102.52.127.25532,766
106102.52.128.0/17102.52.128.1 to 102.52.255.254102.52.255.25532,766
107102.53.0.0/17102.53.0.1 to 102.53.127.254102.53.127.25532,766
108102.53.128.0/17102.53.128.1 to 102.53.255.254102.53.255.25532,766
109102.54.0.0/17102.54.0.1 to 102.54.127.254102.54.127.25532,766
110102.54.128.0/17102.54.128.1 to 102.54.255.254102.54.255.25532,766
111102.55.0.0/17102.55.0.1 to 102.55.127.254102.55.127.25532,766
112102.55.128.0/17102.55.128.1 to 102.55.255.254102.55.255.25532,766
113102.56.0.0/17102.56.0.1 to 102.56.127.254102.56.127.25532,766
114102.56.128.0/17102.56.128.1 to 102.56.255.254102.56.255.25532,766
115102.57.0.0/17102.57.0.1 to 102.57.127.254102.57.127.25532,766
116102.57.128.0/17102.57.128.1 to 102.57.255.254102.57.255.25532,766
117102.58.0.0/17102.58.0.1 to 102.58.127.254102.58.127.25532,766
118102.58.128.0/17102.58.128.1 to 102.58.255.254102.58.255.25532,766
119102.59.0.0/17102.59.0.1 to 102.59.127.254102.59.127.25532,766
120102.59.128.0/17102.59.128.1 to 102.59.255.254102.59.255.25532,766
121102.60.0.0/17102.60.0.1 to 102.60.127.254102.60.127.25532,766
122102.60.128.0/17102.60.128.1 to 102.60.255.254102.60.255.25532,766
123102.61.0.0/17102.61.0.1 to 102.61.127.254102.61.127.25532,766
124102.61.128.0/17102.61.128.1 to 102.61.255.254102.61.255.25532,766
125102.62.0.0/17102.62.0.1 to 102.62.127.254102.62.127.25532,766
126102.62.128.0/17102.62.128.1 to 102.62.255.254102.62.255.25532,766
127102.63.0.0/17102.63.0.1 to 102.63.127.254102.63.127.25532,766
128102.63.128.0/17102.63.128.1 to 102.63.255.254102.63.255.25532,766
129102.64.0.0/17102.64.0.1 to 102.64.127.254102.64.127.25532,766
130102.64.128.0/17102.64.128.1 to 102.64.255.254102.64.255.25532,766
131102.65.0.0/17102.65.0.1 to 102.65.127.254102.65.127.25532,766
132102.65.128.0/17102.65.128.1 to 102.65.255.254102.65.255.25532,766
133102.66.0.0/17102.66.0.1 to 102.66.127.254102.66.127.25532,766
134102.66.128.0/17102.66.128.1 to 102.66.255.254102.66.255.25532,766
135102.67.0.0/17102.67.0.1 to 102.67.127.254102.67.127.25532,766
136102.67.128.0/17102.67.128.1 to 102.67.255.254102.67.255.25532,766
137102.68.0.0/17102.68.0.1 to 102.68.127.254102.68.127.25532,766
138102.68.128.0/17102.68.128.1 to 102.68.255.254102.68.255.25532,766
139102.69.0.0/17102.69.0.1 to 102.69.127.254102.69.127.25532,766
140102.69.128.0/17102.69.128.1 to 102.69.255.254102.69.255.25532,766
141102.70.0.0/17102.70.0.1 to 102.70.127.254102.70.127.25532,766
142102.70.128.0/17102.70.128.1 to 102.70.255.254102.70.255.25532,766
143102.71.0.0/17102.71.0.1 to 102.71.127.254102.71.127.25532,766
144102.71.128.0/17102.71.128.1 to 102.71.255.254102.71.255.25532,766
145102.72.0.0/17102.72.0.1 to 102.72.127.254102.72.127.25532,766
146102.72.128.0/17102.72.128.1 to 102.72.255.254102.72.255.25532,766
147102.73.0.0/17102.73.0.1 to 102.73.127.254102.73.127.25532,766
148102.73.128.0/17102.73.128.1 to 102.73.255.254102.73.255.25532,766
149102.74.0.0/17102.74.0.1 to 102.74.127.254102.74.127.25532,766
150102.74.128.0/17102.74.128.1 to 102.74.255.254102.74.255.25532,766
151102.75.0.0/17102.75.0.1 to 102.75.127.254102.75.127.25532,766
152102.75.128.0/17102.75.128.1 to 102.75.255.254102.75.255.25532,766
153102.76.0.0/17102.76.0.1 to 102.76.127.254102.76.127.25532,766
154102.76.128.0/17102.76.128.1 to 102.76.255.254102.76.255.25532,766
155102.77.0.0/17102.77.0.1 to 102.77.127.254102.77.127.25532,766
156102.77.128.0/17102.77.128.1 to 102.77.255.254102.77.255.25532,766
157102.78.0.0/17102.78.0.1 to 102.78.127.254102.78.127.25532,766
158102.78.128.0/17102.78.128.1 to 102.78.255.254102.78.255.25532,766
159102.79.0.0/17102.79.0.1 to 102.79.127.254102.79.127.25532,766
160102.79.128.0/17102.79.128.1 to 102.79.255.254102.79.255.25532,766
161102.80.0.0/17102.80.0.1 to 102.80.127.254102.80.127.25532,766
162102.80.128.0/17102.80.128.1 to 102.80.255.254102.80.255.25532,766
163102.81.0.0/17102.81.0.1 to 102.81.127.254102.81.127.25532,766
164102.81.128.0/17102.81.128.1 to 102.81.255.254102.81.255.25532,766
165102.82.0.0/17102.82.0.1 to 102.82.127.254102.82.127.25532,766
166102.82.128.0/17102.82.128.1 to 102.82.255.254102.82.255.25532,766
167102.83.0.0/17102.83.0.1 to 102.83.127.254102.83.127.25532,766
168102.83.128.0/17102.83.128.1 to 102.83.255.254102.83.255.25532,766
169102.84.0.0/17102.84.0.1 to 102.84.127.254102.84.127.25532,766
170102.84.128.0/17102.84.128.1 to 102.84.255.254102.84.255.25532,766
171102.85.0.0/17102.85.0.1 to 102.85.127.254102.85.127.25532,766
172102.85.128.0/17102.85.128.1 to 102.85.255.254102.85.255.25532,766
173102.86.0.0/17102.86.0.1 to 102.86.127.254102.86.127.25532,766
174102.86.128.0/17102.86.128.1 to 102.86.255.254102.86.255.25532,766
175102.87.0.0/17102.87.0.1 to 102.87.127.254102.87.127.25532,766
176102.87.128.0/17102.87.128.1 to 102.87.255.254102.87.255.25532,766
177102.88.0.0/17102.88.0.1 to 102.88.127.254102.88.127.25532,766
178102.88.128.0/17102.88.128.1 to 102.88.255.254102.88.255.25532,766
179102.89.0.0/17102.89.0.1 to 102.89.127.254102.89.127.25532,766
180102.89.128.0/17102.89.128.1 to 102.89.255.254102.89.255.25532,766
181102.90.0.0/17102.90.0.1 to 102.90.127.254102.90.127.25532,766
182102.90.128.0/17102.90.128.1 to 102.90.255.254102.90.255.25532,766
183102.91.0.0/17102.91.0.1 to 102.91.127.254102.91.127.25532,766
184102.91.128.0/17102.91.128.1 to 102.91.255.254102.91.255.25532,766
185102.92.0.0/17102.92.0.1 to 102.92.127.254102.92.127.25532,766
186102.92.128.0/17102.92.128.1 to 102.92.255.254102.92.255.25532,766
187102.93.0.0/17102.93.0.1 to 102.93.127.254102.93.127.25532,766
188102.93.128.0/17102.93.128.1 to 102.93.255.254102.93.255.25532,766
189102.94.0.0/17102.94.0.1 to 102.94.127.254102.94.127.25532,766
190102.94.128.0/17102.94.128.1 to 102.94.255.254102.94.255.25532,766
191102.95.0.0/17102.95.0.1 to 102.95.127.254102.95.127.25532,766
192102.95.128.0/17102.95.128.1 to 102.95.255.254102.95.255.25532,766
193102.96.0.0/17102.96.0.1 to 102.96.127.254102.96.127.25532,766
194102.96.128.0/17102.96.128.1 to 102.96.255.254102.96.255.25532,766
195102.97.0.0/17102.97.0.1 to 102.97.127.254102.97.127.25532,766
196102.97.128.0/17102.97.128.1 to 102.97.255.254102.97.255.25532,766
197102.98.0.0/17102.98.0.1 to 102.98.127.254102.98.127.25532,766
198102.98.128.0/17102.98.128.1 to 102.98.255.254102.98.255.25532,766
199102.99.0.0/17102.99.0.1 to 102.99.127.254102.99.127.25532,766
200102.99.128.0/17102.99.128.1 to 102.99.255.254102.99.255.25532,766
201102.100.0.0/17102.100.0.1 to 102.100.127.254102.100.127.25532,766
202102.100.128.0/17102.100.128.1 to 102.100.255.254102.100.255.25532,766
203102.101.0.0/17102.101.0.1 to 102.101.127.254102.101.127.25532,766
204102.101.128.0/17102.101.128.1 to 102.101.255.254102.101.255.25532,766
205102.102.0.0/17102.102.0.1 to 102.102.127.254102.102.127.25532,766
206102.102.128.0/17102.102.128.1 to 102.102.255.254102.102.255.25532,766
207102.103.0.0/17102.103.0.1 to 102.103.127.254102.103.127.25532,766
208102.103.128.0/17102.103.128.1 to 102.103.255.254102.103.255.25532,766
209102.104.0.0/17102.104.0.1 to 102.104.127.254102.104.127.25532,766
210102.104.128.0/17102.104.128.1 to 102.104.255.254102.104.255.25532,766
211102.105.0.0/17102.105.0.1 to 102.105.127.254102.105.127.25532,766
212102.105.128.0/17102.105.128.1 to 102.105.255.254102.105.255.25532,766
213102.106.0.0/17102.106.0.1 to 102.106.127.254102.106.127.25532,766
214102.106.128.0/17102.106.128.1 to 102.106.255.254102.106.255.25532,766
215102.107.0.0/17102.107.0.1 to 102.107.127.254102.107.127.25532,766
216102.107.128.0/17102.107.128.1 to 102.107.255.254102.107.255.25532,766
217102.108.0.0/17102.108.0.1 to 102.108.127.254102.108.127.25532,766
218102.108.128.0/17102.108.128.1 to 102.108.255.254102.108.255.25532,766
219102.109.0.0/17102.109.0.1 to 102.109.127.254102.109.127.25532,766
220102.109.128.0/17102.109.128.1 to 102.109.255.254102.109.255.25532,766
221102.110.0.0/17102.110.0.1 to 102.110.127.254102.110.127.25532,766
222102.110.128.0/17102.110.128.1 to 102.110.255.254102.110.255.25532,766
223102.111.0.0/17102.111.0.1 to 102.111.127.254102.111.127.25532,766
224102.111.128.0/17102.111.128.1 to 102.111.255.254102.111.255.25532,766
225102.112.0.0/17102.112.0.1 to 102.112.127.254102.112.127.25532,766
226102.112.128.0/17102.112.128.1 to 102.112.255.254102.112.255.25532,766
227102.113.0.0/17102.113.0.1 to 102.113.127.254102.113.127.25532,766
228102.113.128.0/17102.113.128.1 to 102.113.255.254102.113.255.25532,766
229102.114.0.0/17102.114.0.1 to 102.114.127.254102.114.127.25532,766
230102.114.128.0/17102.114.128.1 to 102.114.255.254102.114.255.25532,766
231102.115.0.0/17102.115.0.1 to 102.115.127.254102.115.127.25532,766
232102.115.128.0/17102.115.128.1 to 102.115.255.254102.115.255.25532,766
233102.116.0.0/17102.116.0.1 to 102.116.127.254102.116.127.25532,766
234102.116.128.0/17102.116.128.1 to 102.116.255.254102.116.255.25532,766
235102.117.0.0/17102.117.0.1 to 102.117.127.254102.117.127.25532,766
236102.117.128.0/17102.117.128.1 to 102.117.255.254102.117.255.25532,766
237102.118.0.0/17102.118.0.1 to 102.118.127.254102.118.127.25532,766
238102.118.128.0/17102.118.128.1 to 102.118.255.254102.118.255.25532,766
239102.119.0.0/17102.119.0.1 to 102.119.127.254102.119.127.25532,766
240102.119.128.0/17102.119.128.1 to 102.119.255.254102.119.255.25532,766
241102.120.0.0/17102.120.0.1 to 102.120.127.254102.120.127.25532,766
242102.120.128.0/17102.120.128.1 to 102.120.255.254102.120.255.25532,766
243102.121.0.0/17102.121.0.1 to 102.121.127.254102.121.127.25532,766
244102.121.128.0/17102.121.128.1 to 102.121.255.254102.121.255.25532,766
245102.122.0.0/17102.122.0.1 to 102.122.127.254102.122.127.25532,766
246102.122.128.0/17102.122.128.1 to 102.122.255.254102.122.255.25532,766
247102.123.0.0/17102.123.0.1 to 102.123.127.254102.123.127.25532,766
248102.123.128.0/17102.123.128.1 to 102.123.255.254102.123.255.25532,766
249102.124.0.0/17102.124.0.1 to 102.124.127.254102.124.127.25532,766
250102.124.128.0/17102.124.128.1 to 102.124.255.254102.124.255.25532,766
251102.125.0.0/17102.125.0.1 to 102.125.127.254102.125.127.25532,766
252102.125.128.0/17102.125.128.1 to 102.125.255.254102.125.255.25532,766
253102.126.0.0/17102.126.0.1 to 102.126.127.254102.126.127.25532,766
254102.126.128.0/17102.126.128.1 to 102.126.255.254102.126.255.25532,766
255102.127.0.0/17102.127.0.1 to 102.127.127.254102.127.127.25532,766
256102.127.128.0/17102.127.128.1 to 102.127.255.254102.127.255.25532,766

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.