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.

Network120.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
120.0.0.0
Broadcast address
121.255.255.255
First usable
120.0.0.1
Last usable
121.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
A (default /8)
As numbers
Hex 78000000 · Integer 2013265920 to 2046820351
Reverse DNS zones
120.in-addr.arpa
121.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01111000.00000000.00000000.00000000120.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network01111000.00000000.00000000.00000000120.0.0.0
Broadcast01111001.11111111.11111111.11111111121.255.255.255
Split into smaller subnets/16
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

120.0.0.0/7 makes 512 subnets of /16; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1120.0.0.0/16120.0.0.1 to 120.0.255.254120.0.255.25565,534
2120.1.0.0/16120.1.0.1 to 120.1.255.254120.1.255.25565,534
3120.2.0.0/16120.2.0.1 to 120.2.255.254120.2.255.25565,534
4120.3.0.0/16120.3.0.1 to 120.3.255.254120.3.255.25565,534
5120.4.0.0/16120.4.0.1 to 120.4.255.254120.4.255.25565,534
6120.5.0.0/16120.5.0.1 to 120.5.255.254120.5.255.25565,534
7120.6.0.0/16120.6.0.1 to 120.6.255.254120.6.255.25565,534
8120.7.0.0/16120.7.0.1 to 120.7.255.254120.7.255.25565,534
9120.8.0.0/16120.8.0.1 to 120.8.255.254120.8.255.25565,534
10120.9.0.0/16120.9.0.1 to 120.9.255.254120.9.255.25565,534
11120.10.0.0/16120.10.0.1 to 120.10.255.254120.10.255.25565,534
12120.11.0.0/16120.11.0.1 to 120.11.255.254120.11.255.25565,534
13120.12.0.0/16120.12.0.1 to 120.12.255.254120.12.255.25565,534
14120.13.0.0/16120.13.0.1 to 120.13.255.254120.13.255.25565,534
15120.14.0.0/16120.14.0.1 to 120.14.255.254120.14.255.25565,534
16120.15.0.0/16120.15.0.1 to 120.15.255.254120.15.255.25565,534
17120.16.0.0/16120.16.0.1 to 120.16.255.254120.16.255.25565,534
18120.17.0.0/16120.17.0.1 to 120.17.255.254120.17.255.25565,534
19120.18.0.0/16120.18.0.1 to 120.18.255.254120.18.255.25565,534
20120.19.0.0/16120.19.0.1 to 120.19.255.254120.19.255.25565,534
21120.20.0.0/16120.20.0.1 to 120.20.255.254120.20.255.25565,534
22120.21.0.0/16120.21.0.1 to 120.21.255.254120.21.255.25565,534
23120.22.0.0/16120.22.0.1 to 120.22.255.254120.22.255.25565,534
24120.23.0.0/16120.23.0.1 to 120.23.255.254120.23.255.25565,534
25120.24.0.0/16120.24.0.1 to 120.24.255.254120.24.255.25565,534
26120.25.0.0/16120.25.0.1 to 120.25.255.254120.25.255.25565,534
27120.26.0.0/16120.26.0.1 to 120.26.255.254120.26.255.25565,534
28120.27.0.0/16120.27.0.1 to 120.27.255.254120.27.255.25565,534
29120.28.0.0/16120.28.0.1 to 120.28.255.254120.28.255.25565,534
30120.29.0.0/16120.29.0.1 to 120.29.255.254120.29.255.25565,534
31120.30.0.0/16120.30.0.1 to 120.30.255.254120.30.255.25565,534
32120.31.0.0/16120.31.0.1 to 120.31.255.254120.31.255.25565,534
33120.32.0.0/16120.32.0.1 to 120.32.255.254120.32.255.25565,534
34120.33.0.0/16120.33.0.1 to 120.33.255.254120.33.255.25565,534
35120.34.0.0/16120.34.0.1 to 120.34.255.254120.34.255.25565,534
36120.35.0.0/16120.35.0.1 to 120.35.255.254120.35.255.25565,534
37120.36.0.0/16120.36.0.1 to 120.36.255.254120.36.255.25565,534
38120.37.0.0/16120.37.0.1 to 120.37.255.254120.37.255.25565,534
39120.38.0.0/16120.38.0.1 to 120.38.255.254120.38.255.25565,534
40120.39.0.0/16120.39.0.1 to 120.39.255.254120.39.255.25565,534
41120.40.0.0/16120.40.0.1 to 120.40.255.254120.40.255.25565,534
42120.41.0.0/16120.41.0.1 to 120.41.255.254120.41.255.25565,534
43120.42.0.0/16120.42.0.1 to 120.42.255.254120.42.255.25565,534
44120.43.0.0/16120.43.0.1 to 120.43.255.254120.43.255.25565,534
45120.44.0.0/16120.44.0.1 to 120.44.255.254120.44.255.25565,534
46120.45.0.0/16120.45.0.1 to 120.45.255.254120.45.255.25565,534
47120.46.0.0/16120.46.0.1 to 120.46.255.254120.46.255.25565,534
48120.47.0.0/16120.47.0.1 to 120.47.255.254120.47.255.25565,534
49120.48.0.0/16120.48.0.1 to 120.48.255.254120.48.255.25565,534
50120.49.0.0/16120.49.0.1 to 120.49.255.254120.49.255.25565,534
51120.50.0.0/16120.50.0.1 to 120.50.255.254120.50.255.25565,534
52120.51.0.0/16120.51.0.1 to 120.51.255.254120.51.255.25565,534
53120.52.0.0/16120.52.0.1 to 120.52.255.254120.52.255.25565,534
54120.53.0.0/16120.53.0.1 to 120.53.255.254120.53.255.25565,534
55120.54.0.0/16120.54.0.1 to 120.54.255.254120.54.255.25565,534
56120.55.0.0/16120.55.0.1 to 120.55.255.254120.55.255.25565,534
57120.56.0.0/16120.56.0.1 to 120.56.255.254120.56.255.25565,534
58120.57.0.0/16120.57.0.1 to 120.57.255.254120.57.255.25565,534
59120.58.0.0/16120.58.0.1 to 120.58.255.254120.58.255.25565,534
60120.59.0.0/16120.59.0.1 to 120.59.255.254120.59.255.25565,534
61120.60.0.0/16120.60.0.1 to 120.60.255.254120.60.255.25565,534
62120.61.0.0/16120.61.0.1 to 120.61.255.254120.61.255.25565,534
63120.62.0.0/16120.62.0.1 to 120.62.255.254120.62.255.25565,534
64120.63.0.0/16120.63.0.1 to 120.63.255.254120.63.255.25565,534
65120.64.0.0/16120.64.0.1 to 120.64.255.254120.64.255.25565,534
66120.65.0.0/16120.65.0.1 to 120.65.255.254120.65.255.25565,534
67120.66.0.0/16120.66.0.1 to 120.66.255.254120.66.255.25565,534
68120.67.0.0/16120.67.0.1 to 120.67.255.254120.67.255.25565,534
69120.68.0.0/16120.68.0.1 to 120.68.255.254120.68.255.25565,534
70120.69.0.0/16120.69.0.1 to 120.69.255.254120.69.255.25565,534
71120.70.0.0/16120.70.0.1 to 120.70.255.254120.70.255.25565,534
72120.71.0.0/16120.71.0.1 to 120.71.255.254120.71.255.25565,534
73120.72.0.0/16120.72.0.1 to 120.72.255.254120.72.255.25565,534
74120.73.0.0/16120.73.0.1 to 120.73.255.254120.73.255.25565,534
75120.74.0.0/16120.74.0.1 to 120.74.255.254120.74.255.25565,534
76120.75.0.0/16120.75.0.1 to 120.75.255.254120.75.255.25565,534
77120.76.0.0/16120.76.0.1 to 120.76.255.254120.76.255.25565,534
78120.77.0.0/16120.77.0.1 to 120.77.255.254120.77.255.25565,534
79120.78.0.0/16120.78.0.1 to 120.78.255.254120.78.255.25565,534
80120.79.0.0/16120.79.0.1 to 120.79.255.254120.79.255.25565,534
81120.80.0.0/16120.80.0.1 to 120.80.255.254120.80.255.25565,534
82120.81.0.0/16120.81.0.1 to 120.81.255.254120.81.255.25565,534
83120.82.0.0/16120.82.0.1 to 120.82.255.254120.82.255.25565,534
84120.83.0.0/16120.83.0.1 to 120.83.255.254120.83.255.25565,534
85120.84.0.0/16120.84.0.1 to 120.84.255.254120.84.255.25565,534
86120.85.0.0/16120.85.0.1 to 120.85.255.254120.85.255.25565,534
87120.86.0.0/16120.86.0.1 to 120.86.255.254120.86.255.25565,534
88120.87.0.0/16120.87.0.1 to 120.87.255.254120.87.255.25565,534
89120.88.0.0/16120.88.0.1 to 120.88.255.254120.88.255.25565,534
90120.89.0.0/16120.89.0.1 to 120.89.255.254120.89.255.25565,534
91120.90.0.0/16120.90.0.1 to 120.90.255.254120.90.255.25565,534
92120.91.0.0/16120.91.0.1 to 120.91.255.254120.91.255.25565,534
93120.92.0.0/16120.92.0.1 to 120.92.255.254120.92.255.25565,534
94120.93.0.0/16120.93.0.1 to 120.93.255.254120.93.255.25565,534
95120.94.0.0/16120.94.0.1 to 120.94.255.254120.94.255.25565,534
96120.95.0.0/16120.95.0.1 to 120.95.255.254120.95.255.25565,534
97120.96.0.0/16120.96.0.1 to 120.96.255.254120.96.255.25565,534
98120.97.0.0/16120.97.0.1 to 120.97.255.254120.97.255.25565,534
99120.98.0.0/16120.98.0.1 to 120.98.255.254120.98.255.25565,534
100120.99.0.0/16120.99.0.1 to 120.99.255.254120.99.255.25565,534
101120.100.0.0/16120.100.0.1 to 120.100.255.254120.100.255.25565,534
102120.101.0.0/16120.101.0.1 to 120.101.255.254120.101.255.25565,534
103120.102.0.0/16120.102.0.1 to 120.102.255.254120.102.255.25565,534
104120.103.0.0/16120.103.0.1 to 120.103.255.254120.103.255.25565,534
105120.104.0.0/16120.104.0.1 to 120.104.255.254120.104.255.25565,534
106120.105.0.0/16120.105.0.1 to 120.105.255.254120.105.255.25565,534
107120.106.0.0/16120.106.0.1 to 120.106.255.254120.106.255.25565,534
108120.107.0.0/16120.107.0.1 to 120.107.255.254120.107.255.25565,534
109120.108.0.0/16120.108.0.1 to 120.108.255.254120.108.255.25565,534
110120.109.0.0/16120.109.0.1 to 120.109.255.254120.109.255.25565,534
111120.110.0.0/16120.110.0.1 to 120.110.255.254120.110.255.25565,534
112120.111.0.0/16120.111.0.1 to 120.111.255.254120.111.255.25565,534
113120.112.0.0/16120.112.0.1 to 120.112.255.254120.112.255.25565,534
114120.113.0.0/16120.113.0.1 to 120.113.255.254120.113.255.25565,534
115120.114.0.0/16120.114.0.1 to 120.114.255.254120.114.255.25565,534
116120.115.0.0/16120.115.0.1 to 120.115.255.254120.115.255.25565,534
117120.116.0.0/16120.116.0.1 to 120.116.255.254120.116.255.25565,534
118120.117.0.0/16120.117.0.1 to 120.117.255.254120.117.255.25565,534
119120.118.0.0/16120.118.0.1 to 120.118.255.254120.118.255.25565,534
120120.119.0.0/16120.119.0.1 to 120.119.255.254120.119.255.25565,534
121120.120.0.0/16120.120.0.1 to 120.120.255.254120.120.255.25565,534
122120.121.0.0/16120.121.0.1 to 120.121.255.254120.121.255.25565,534
123120.122.0.0/16120.122.0.1 to 120.122.255.254120.122.255.25565,534
124120.123.0.0/16120.123.0.1 to 120.123.255.254120.123.255.25565,534
125120.124.0.0/16120.124.0.1 to 120.124.255.254120.124.255.25565,534
126120.125.0.0/16120.125.0.1 to 120.125.255.254120.125.255.25565,534
127120.126.0.0/16120.126.0.1 to 120.126.255.254120.126.255.25565,534
128120.127.0.0/16120.127.0.1 to 120.127.255.254120.127.255.25565,534
129120.128.0.0/16120.128.0.1 to 120.128.255.254120.128.255.25565,534
130120.129.0.0/16120.129.0.1 to 120.129.255.254120.129.255.25565,534
131120.130.0.0/16120.130.0.1 to 120.130.255.254120.130.255.25565,534
132120.131.0.0/16120.131.0.1 to 120.131.255.254120.131.255.25565,534
133120.132.0.0/16120.132.0.1 to 120.132.255.254120.132.255.25565,534
134120.133.0.0/16120.133.0.1 to 120.133.255.254120.133.255.25565,534
135120.134.0.0/16120.134.0.1 to 120.134.255.254120.134.255.25565,534
136120.135.0.0/16120.135.0.1 to 120.135.255.254120.135.255.25565,534
137120.136.0.0/16120.136.0.1 to 120.136.255.254120.136.255.25565,534
138120.137.0.0/16120.137.0.1 to 120.137.255.254120.137.255.25565,534
139120.138.0.0/16120.138.0.1 to 120.138.255.254120.138.255.25565,534
140120.139.0.0/16120.139.0.1 to 120.139.255.254120.139.255.25565,534
141120.140.0.0/16120.140.0.1 to 120.140.255.254120.140.255.25565,534
142120.141.0.0/16120.141.0.1 to 120.141.255.254120.141.255.25565,534
143120.142.0.0/16120.142.0.1 to 120.142.255.254120.142.255.25565,534
144120.143.0.0/16120.143.0.1 to 120.143.255.254120.143.255.25565,534
145120.144.0.0/16120.144.0.1 to 120.144.255.254120.144.255.25565,534
146120.145.0.0/16120.145.0.1 to 120.145.255.254120.145.255.25565,534
147120.146.0.0/16120.146.0.1 to 120.146.255.254120.146.255.25565,534
148120.147.0.0/16120.147.0.1 to 120.147.255.254120.147.255.25565,534
149120.148.0.0/16120.148.0.1 to 120.148.255.254120.148.255.25565,534
150120.149.0.0/16120.149.0.1 to 120.149.255.254120.149.255.25565,534
151120.150.0.0/16120.150.0.1 to 120.150.255.254120.150.255.25565,534
152120.151.0.0/16120.151.0.1 to 120.151.255.254120.151.255.25565,534
153120.152.0.0/16120.152.0.1 to 120.152.255.254120.152.255.25565,534
154120.153.0.0/16120.153.0.1 to 120.153.255.254120.153.255.25565,534
155120.154.0.0/16120.154.0.1 to 120.154.255.254120.154.255.25565,534
156120.155.0.0/16120.155.0.1 to 120.155.255.254120.155.255.25565,534
157120.156.0.0/16120.156.0.1 to 120.156.255.254120.156.255.25565,534
158120.157.0.0/16120.157.0.1 to 120.157.255.254120.157.255.25565,534
159120.158.0.0/16120.158.0.1 to 120.158.255.254120.158.255.25565,534
160120.159.0.0/16120.159.0.1 to 120.159.255.254120.159.255.25565,534
161120.160.0.0/16120.160.0.1 to 120.160.255.254120.160.255.25565,534
162120.161.0.0/16120.161.0.1 to 120.161.255.254120.161.255.25565,534
163120.162.0.0/16120.162.0.1 to 120.162.255.254120.162.255.25565,534
164120.163.0.0/16120.163.0.1 to 120.163.255.254120.163.255.25565,534
165120.164.0.0/16120.164.0.1 to 120.164.255.254120.164.255.25565,534
166120.165.0.0/16120.165.0.1 to 120.165.255.254120.165.255.25565,534
167120.166.0.0/16120.166.0.1 to 120.166.255.254120.166.255.25565,534
168120.167.0.0/16120.167.0.1 to 120.167.255.254120.167.255.25565,534
169120.168.0.0/16120.168.0.1 to 120.168.255.254120.168.255.25565,534
170120.169.0.0/16120.169.0.1 to 120.169.255.254120.169.255.25565,534
171120.170.0.0/16120.170.0.1 to 120.170.255.254120.170.255.25565,534
172120.171.0.0/16120.171.0.1 to 120.171.255.254120.171.255.25565,534
173120.172.0.0/16120.172.0.1 to 120.172.255.254120.172.255.25565,534
174120.173.0.0/16120.173.0.1 to 120.173.255.254120.173.255.25565,534
175120.174.0.0/16120.174.0.1 to 120.174.255.254120.174.255.25565,534
176120.175.0.0/16120.175.0.1 to 120.175.255.254120.175.255.25565,534
177120.176.0.0/16120.176.0.1 to 120.176.255.254120.176.255.25565,534
178120.177.0.0/16120.177.0.1 to 120.177.255.254120.177.255.25565,534
179120.178.0.0/16120.178.0.1 to 120.178.255.254120.178.255.25565,534
180120.179.0.0/16120.179.0.1 to 120.179.255.254120.179.255.25565,534
181120.180.0.0/16120.180.0.1 to 120.180.255.254120.180.255.25565,534
182120.181.0.0/16120.181.0.1 to 120.181.255.254120.181.255.25565,534
183120.182.0.0/16120.182.0.1 to 120.182.255.254120.182.255.25565,534
184120.183.0.0/16120.183.0.1 to 120.183.255.254120.183.255.25565,534
185120.184.0.0/16120.184.0.1 to 120.184.255.254120.184.255.25565,534
186120.185.0.0/16120.185.0.1 to 120.185.255.254120.185.255.25565,534
187120.186.0.0/16120.186.0.1 to 120.186.255.254120.186.255.25565,534
188120.187.0.0/16120.187.0.1 to 120.187.255.254120.187.255.25565,534
189120.188.0.0/16120.188.0.1 to 120.188.255.254120.188.255.25565,534
190120.189.0.0/16120.189.0.1 to 120.189.255.254120.189.255.25565,534
191120.190.0.0/16120.190.0.1 to 120.190.255.254120.190.255.25565,534
192120.191.0.0/16120.191.0.1 to 120.191.255.254120.191.255.25565,534
193120.192.0.0/16120.192.0.1 to 120.192.255.254120.192.255.25565,534
194120.193.0.0/16120.193.0.1 to 120.193.255.254120.193.255.25565,534
195120.194.0.0/16120.194.0.1 to 120.194.255.254120.194.255.25565,534
196120.195.0.0/16120.195.0.1 to 120.195.255.254120.195.255.25565,534
197120.196.0.0/16120.196.0.1 to 120.196.255.254120.196.255.25565,534
198120.197.0.0/16120.197.0.1 to 120.197.255.254120.197.255.25565,534
199120.198.0.0/16120.198.0.1 to 120.198.255.254120.198.255.25565,534
200120.199.0.0/16120.199.0.1 to 120.199.255.254120.199.255.25565,534
201120.200.0.0/16120.200.0.1 to 120.200.255.254120.200.255.25565,534
202120.201.0.0/16120.201.0.1 to 120.201.255.254120.201.255.25565,534
203120.202.0.0/16120.202.0.1 to 120.202.255.254120.202.255.25565,534
204120.203.0.0/16120.203.0.1 to 120.203.255.254120.203.255.25565,534
205120.204.0.0/16120.204.0.1 to 120.204.255.254120.204.255.25565,534
206120.205.0.0/16120.205.0.1 to 120.205.255.254120.205.255.25565,534
207120.206.0.0/16120.206.0.1 to 120.206.255.254120.206.255.25565,534
208120.207.0.0/16120.207.0.1 to 120.207.255.254120.207.255.25565,534
209120.208.0.0/16120.208.0.1 to 120.208.255.254120.208.255.25565,534
210120.209.0.0/16120.209.0.1 to 120.209.255.254120.209.255.25565,534
211120.210.0.0/16120.210.0.1 to 120.210.255.254120.210.255.25565,534
212120.211.0.0/16120.211.0.1 to 120.211.255.254120.211.255.25565,534
213120.212.0.0/16120.212.0.1 to 120.212.255.254120.212.255.25565,534
214120.213.0.0/16120.213.0.1 to 120.213.255.254120.213.255.25565,534
215120.214.0.0/16120.214.0.1 to 120.214.255.254120.214.255.25565,534
216120.215.0.0/16120.215.0.1 to 120.215.255.254120.215.255.25565,534
217120.216.0.0/16120.216.0.1 to 120.216.255.254120.216.255.25565,534
218120.217.0.0/16120.217.0.1 to 120.217.255.254120.217.255.25565,534
219120.218.0.0/16120.218.0.1 to 120.218.255.254120.218.255.25565,534
220120.219.0.0/16120.219.0.1 to 120.219.255.254120.219.255.25565,534
221120.220.0.0/16120.220.0.1 to 120.220.255.254120.220.255.25565,534
222120.221.0.0/16120.221.0.1 to 120.221.255.254120.221.255.25565,534
223120.222.0.0/16120.222.0.1 to 120.222.255.254120.222.255.25565,534
224120.223.0.0/16120.223.0.1 to 120.223.255.254120.223.255.25565,534
225120.224.0.0/16120.224.0.1 to 120.224.255.254120.224.255.25565,534
226120.225.0.0/16120.225.0.1 to 120.225.255.254120.225.255.25565,534
227120.226.0.0/16120.226.0.1 to 120.226.255.254120.226.255.25565,534
228120.227.0.0/16120.227.0.1 to 120.227.255.254120.227.255.25565,534
229120.228.0.0/16120.228.0.1 to 120.228.255.254120.228.255.25565,534
230120.229.0.0/16120.229.0.1 to 120.229.255.254120.229.255.25565,534
231120.230.0.0/16120.230.0.1 to 120.230.255.254120.230.255.25565,534
232120.231.0.0/16120.231.0.1 to 120.231.255.254120.231.255.25565,534
233120.232.0.0/16120.232.0.1 to 120.232.255.254120.232.255.25565,534
234120.233.0.0/16120.233.0.1 to 120.233.255.254120.233.255.25565,534
235120.234.0.0/16120.234.0.1 to 120.234.255.254120.234.255.25565,534
236120.235.0.0/16120.235.0.1 to 120.235.255.254120.235.255.25565,534
237120.236.0.0/16120.236.0.1 to 120.236.255.254120.236.255.25565,534
238120.237.0.0/16120.237.0.1 to 120.237.255.254120.237.255.25565,534
239120.238.0.0/16120.238.0.1 to 120.238.255.254120.238.255.25565,534
240120.239.0.0/16120.239.0.1 to 120.239.255.254120.239.255.25565,534
241120.240.0.0/16120.240.0.1 to 120.240.255.254120.240.255.25565,534
242120.241.0.0/16120.241.0.1 to 120.241.255.254120.241.255.25565,534
243120.242.0.0/16120.242.0.1 to 120.242.255.254120.242.255.25565,534
244120.243.0.0/16120.243.0.1 to 120.243.255.254120.243.255.25565,534
245120.244.0.0/16120.244.0.1 to 120.244.255.254120.244.255.25565,534
246120.245.0.0/16120.245.0.1 to 120.245.255.254120.245.255.25565,534
247120.246.0.0/16120.246.0.1 to 120.246.255.254120.246.255.25565,534
248120.247.0.0/16120.247.0.1 to 120.247.255.254120.247.255.25565,534
249120.248.0.0/16120.248.0.1 to 120.248.255.254120.248.255.25565,534
250120.249.0.0/16120.249.0.1 to 120.249.255.254120.249.255.25565,534
251120.250.0.0/16120.250.0.1 to 120.250.255.254120.250.255.25565,534
252120.251.0.0/16120.251.0.1 to 120.251.255.254120.251.255.25565,534
253120.252.0.0/16120.252.0.1 to 120.252.255.254120.252.255.25565,534
254120.253.0.0/16120.253.0.1 to 120.253.255.254120.253.255.25565,534
255120.254.0.0/16120.254.0.1 to 120.254.255.254120.254.255.25565,534
256120.255.0.0/16120.255.0.1 to 120.255.255.254120.255.255.25565,534

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.