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.

Network240.211.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
240.211.0.0
Broadcast address
240.211.255.255
First usable
240.211.0.1
Last usable
240.211.255.254
Usable hosts
65,534 (65,536 less the network and broadcast addresses)
Subnet mask
255.255.0.0
Wildcard mask
0.0.255.255 (Cisco ACLs, OSPF)
Prefix length
/16
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F0D30000 · Integer 4040359936 to 4040425471
Reverse DNS zone
211.240.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11110000.11010011..00000000.00000000240.211.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network11110000.11010011..00000000.00000000240.211.0.0
Broadcast11110000.11010011..11111111.11111111240.211.255.255
Split into smaller subnets/24
/17 (2)/18 (4)/19 (8)/20 (16)/21 (32)/22 (64)/23 (128)/24 (256)/25 (512)/26 (1,024)/27 (2,048)/28 (4,096)

240.211.0.0/16 makes 256 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1240.211.0.0/24240.211.0.1 to 240.211.0.254240.211.0.255254
2240.211.1.0/24240.211.1.1 to 240.211.1.254240.211.1.255254
3240.211.2.0/24240.211.2.1 to 240.211.2.254240.211.2.255254
4240.211.3.0/24240.211.3.1 to 240.211.3.254240.211.3.255254
5240.211.4.0/24240.211.4.1 to 240.211.4.254240.211.4.255254
6240.211.5.0/24240.211.5.1 to 240.211.5.254240.211.5.255254
7240.211.6.0/24240.211.6.1 to 240.211.6.254240.211.6.255254
8240.211.7.0/24240.211.7.1 to 240.211.7.254240.211.7.255254
9240.211.8.0/24240.211.8.1 to 240.211.8.254240.211.8.255254
10240.211.9.0/24240.211.9.1 to 240.211.9.254240.211.9.255254
11240.211.10.0/24240.211.10.1 to 240.211.10.254240.211.10.255254
12240.211.11.0/24240.211.11.1 to 240.211.11.254240.211.11.255254
13240.211.12.0/24240.211.12.1 to 240.211.12.254240.211.12.255254
14240.211.13.0/24240.211.13.1 to 240.211.13.254240.211.13.255254
15240.211.14.0/24240.211.14.1 to 240.211.14.254240.211.14.255254
16240.211.15.0/24240.211.15.1 to 240.211.15.254240.211.15.255254
17240.211.16.0/24240.211.16.1 to 240.211.16.254240.211.16.255254
18240.211.17.0/24240.211.17.1 to 240.211.17.254240.211.17.255254
19240.211.18.0/24240.211.18.1 to 240.211.18.254240.211.18.255254
20240.211.19.0/24240.211.19.1 to 240.211.19.254240.211.19.255254
21240.211.20.0/24240.211.20.1 to 240.211.20.254240.211.20.255254
22240.211.21.0/24240.211.21.1 to 240.211.21.254240.211.21.255254
23240.211.22.0/24240.211.22.1 to 240.211.22.254240.211.22.255254
24240.211.23.0/24240.211.23.1 to 240.211.23.254240.211.23.255254
25240.211.24.0/24240.211.24.1 to 240.211.24.254240.211.24.255254
26240.211.25.0/24240.211.25.1 to 240.211.25.254240.211.25.255254
27240.211.26.0/24240.211.26.1 to 240.211.26.254240.211.26.255254
28240.211.27.0/24240.211.27.1 to 240.211.27.254240.211.27.255254
29240.211.28.0/24240.211.28.1 to 240.211.28.254240.211.28.255254
30240.211.29.0/24240.211.29.1 to 240.211.29.254240.211.29.255254
31240.211.30.0/24240.211.30.1 to 240.211.30.254240.211.30.255254
32240.211.31.0/24240.211.31.1 to 240.211.31.254240.211.31.255254
33240.211.32.0/24240.211.32.1 to 240.211.32.254240.211.32.255254
34240.211.33.0/24240.211.33.1 to 240.211.33.254240.211.33.255254
35240.211.34.0/24240.211.34.1 to 240.211.34.254240.211.34.255254
36240.211.35.0/24240.211.35.1 to 240.211.35.254240.211.35.255254
37240.211.36.0/24240.211.36.1 to 240.211.36.254240.211.36.255254
38240.211.37.0/24240.211.37.1 to 240.211.37.254240.211.37.255254
39240.211.38.0/24240.211.38.1 to 240.211.38.254240.211.38.255254
40240.211.39.0/24240.211.39.1 to 240.211.39.254240.211.39.255254
41240.211.40.0/24240.211.40.1 to 240.211.40.254240.211.40.255254
42240.211.41.0/24240.211.41.1 to 240.211.41.254240.211.41.255254
43240.211.42.0/24240.211.42.1 to 240.211.42.254240.211.42.255254
44240.211.43.0/24240.211.43.1 to 240.211.43.254240.211.43.255254
45240.211.44.0/24240.211.44.1 to 240.211.44.254240.211.44.255254
46240.211.45.0/24240.211.45.1 to 240.211.45.254240.211.45.255254
47240.211.46.0/24240.211.46.1 to 240.211.46.254240.211.46.255254
48240.211.47.0/24240.211.47.1 to 240.211.47.254240.211.47.255254
49240.211.48.0/24240.211.48.1 to 240.211.48.254240.211.48.255254
50240.211.49.0/24240.211.49.1 to 240.211.49.254240.211.49.255254
51240.211.50.0/24240.211.50.1 to 240.211.50.254240.211.50.255254
52240.211.51.0/24240.211.51.1 to 240.211.51.254240.211.51.255254
53240.211.52.0/24240.211.52.1 to 240.211.52.254240.211.52.255254
54240.211.53.0/24240.211.53.1 to 240.211.53.254240.211.53.255254
55240.211.54.0/24240.211.54.1 to 240.211.54.254240.211.54.255254
56240.211.55.0/24240.211.55.1 to 240.211.55.254240.211.55.255254
57240.211.56.0/24240.211.56.1 to 240.211.56.254240.211.56.255254
58240.211.57.0/24240.211.57.1 to 240.211.57.254240.211.57.255254
59240.211.58.0/24240.211.58.1 to 240.211.58.254240.211.58.255254
60240.211.59.0/24240.211.59.1 to 240.211.59.254240.211.59.255254
61240.211.60.0/24240.211.60.1 to 240.211.60.254240.211.60.255254
62240.211.61.0/24240.211.61.1 to 240.211.61.254240.211.61.255254
63240.211.62.0/24240.211.62.1 to 240.211.62.254240.211.62.255254
64240.211.63.0/24240.211.63.1 to 240.211.63.254240.211.63.255254
65240.211.64.0/24240.211.64.1 to 240.211.64.254240.211.64.255254
66240.211.65.0/24240.211.65.1 to 240.211.65.254240.211.65.255254
67240.211.66.0/24240.211.66.1 to 240.211.66.254240.211.66.255254
68240.211.67.0/24240.211.67.1 to 240.211.67.254240.211.67.255254
69240.211.68.0/24240.211.68.1 to 240.211.68.254240.211.68.255254
70240.211.69.0/24240.211.69.1 to 240.211.69.254240.211.69.255254
71240.211.70.0/24240.211.70.1 to 240.211.70.254240.211.70.255254
72240.211.71.0/24240.211.71.1 to 240.211.71.254240.211.71.255254
73240.211.72.0/24240.211.72.1 to 240.211.72.254240.211.72.255254
74240.211.73.0/24240.211.73.1 to 240.211.73.254240.211.73.255254
75240.211.74.0/24240.211.74.1 to 240.211.74.254240.211.74.255254
76240.211.75.0/24240.211.75.1 to 240.211.75.254240.211.75.255254
77240.211.76.0/24240.211.76.1 to 240.211.76.254240.211.76.255254
78240.211.77.0/24240.211.77.1 to 240.211.77.254240.211.77.255254
79240.211.78.0/24240.211.78.1 to 240.211.78.254240.211.78.255254
80240.211.79.0/24240.211.79.1 to 240.211.79.254240.211.79.255254
81240.211.80.0/24240.211.80.1 to 240.211.80.254240.211.80.255254
82240.211.81.0/24240.211.81.1 to 240.211.81.254240.211.81.255254
83240.211.82.0/24240.211.82.1 to 240.211.82.254240.211.82.255254
84240.211.83.0/24240.211.83.1 to 240.211.83.254240.211.83.255254
85240.211.84.0/24240.211.84.1 to 240.211.84.254240.211.84.255254
86240.211.85.0/24240.211.85.1 to 240.211.85.254240.211.85.255254
87240.211.86.0/24240.211.86.1 to 240.211.86.254240.211.86.255254
88240.211.87.0/24240.211.87.1 to 240.211.87.254240.211.87.255254
89240.211.88.0/24240.211.88.1 to 240.211.88.254240.211.88.255254
90240.211.89.0/24240.211.89.1 to 240.211.89.254240.211.89.255254
91240.211.90.0/24240.211.90.1 to 240.211.90.254240.211.90.255254
92240.211.91.0/24240.211.91.1 to 240.211.91.254240.211.91.255254
93240.211.92.0/24240.211.92.1 to 240.211.92.254240.211.92.255254
94240.211.93.0/24240.211.93.1 to 240.211.93.254240.211.93.255254
95240.211.94.0/24240.211.94.1 to 240.211.94.254240.211.94.255254
96240.211.95.0/24240.211.95.1 to 240.211.95.254240.211.95.255254
97240.211.96.0/24240.211.96.1 to 240.211.96.254240.211.96.255254
98240.211.97.0/24240.211.97.1 to 240.211.97.254240.211.97.255254
99240.211.98.0/24240.211.98.1 to 240.211.98.254240.211.98.255254
100240.211.99.0/24240.211.99.1 to 240.211.99.254240.211.99.255254
101240.211.100.0/24240.211.100.1 to 240.211.100.254240.211.100.255254
102240.211.101.0/24240.211.101.1 to 240.211.101.254240.211.101.255254
103240.211.102.0/24240.211.102.1 to 240.211.102.254240.211.102.255254
104240.211.103.0/24240.211.103.1 to 240.211.103.254240.211.103.255254
105240.211.104.0/24240.211.104.1 to 240.211.104.254240.211.104.255254
106240.211.105.0/24240.211.105.1 to 240.211.105.254240.211.105.255254
107240.211.106.0/24240.211.106.1 to 240.211.106.254240.211.106.255254
108240.211.107.0/24240.211.107.1 to 240.211.107.254240.211.107.255254
109240.211.108.0/24240.211.108.1 to 240.211.108.254240.211.108.255254
110240.211.109.0/24240.211.109.1 to 240.211.109.254240.211.109.255254
111240.211.110.0/24240.211.110.1 to 240.211.110.254240.211.110.255254
112240.211.111.0/24240.211.111.1 to 240.211.111.254240.211.111.255254
113240.211.112.0/24240.211.112.1 to 240.211.112.254240.211.112.255254
114240.211.113.0/24240.211.113.1 to 240.211.113.254240.211.113.255254
115240.211.114.0/24240.211.114.1 to 240.211.114.254240.211.114.255254
116240.211.115.0/24240.211.115.1 to 240.211.115.254240.211.115.255254
117240.211.116.0/24240.211.116.1 to 240.211.116.254240.211.116.255254
118240.211.117.0/24240.211.117.1 to 240.211.117.254240.211.117.255254
119240.211.118.0/24240.211.118.1 to 240.211.118.254240.211.118.255254
120240.211.119.0/24240.211.119.1 to 240.211.119.254240.211.119.255254
121240.211.120.0/24240.211.120.1 to 240.211.120.254240.211.120.255254
122240.211.121.0/24240.211.121.1 to 240.211.121.254240.211.121.255254
123240.211.122.0/24240.211.122.1 to 240.211.122.254240.211.122.255254
124240.211.123.0/24240.211.123.1 to 240.211.123.254240.211.123.255254
125240.211.124.0/24240.211.124.1 to 240.211.124.254240.211.124.255254
126240.211.125.0/24240.211.125.1 to 240.211.125.254240.211.125.255254
127240.211.126.0/24240.211.126.1 to 240.211.126.254240.211.126.255254
128240.211.127.0/24240.211.127.1 to 240.211.127.254240.211.127.255254
129240.211.128.0/24240.211.128.1 to 240.211.128.254240.211.128.255254
130240.211.129.0/24240.211.129.1 to 240.211.129.254240.211.129.255254
131240.211.130.0/24240.211.130.1 to 240.211.130.254240.211.130.255254
132240.211.131.0/24240.211.131.1 to 240.211.131.254240.211.131.255254
133240.211.132.0/24240.211.132.1 to 240.211.132.254240.211.132.255254
134240.211.133.0/24240.211.133.1 to 240.211.133.254240.211.133.255254
135240.211.134.0/24240.211.134.1 to 240.211.134.254240.211.134.255254
136240.211.135.0/24240.211.135.1 to 240.211.135.254240.211.135.255254
137240.211.136.0/24240.211.136.1 to 240.211.136.254240.211.136.255254
138240.211.137.0/24240.211.137.1 to 240.211.137.254240.211.137.255254
139240.211.138.0/24240.211.138.1 to 240.211.138.254240.211.138.255254
140240.211.139.0/24240.211.139.1 to 240.211.139.254240.211.139.255254
141240.211.140.0/24240.211.140.1 to 240.211.140.254240.211.140.255254
142240.211.141.0/24240.211.141.1 to 240.211.141.254240.211.141.255254
143240.211.142.0/24240.211.142.1 to 240.211.142.254240.211.142.255254
144240.211.143.0/24240.211.143.1 to 240.211.143.254240.211.143.255254
145240.211.144.0/24240.211.144.1 to 240.211.144.254240.211.144.255254
146240.211.145.0/24240.211.145.1 to 240.211.145.254240.211.145.255254
147240.211.146.0/24240.211.146.1 to 240.211.146.254240.211.146.255254
148240.211.147.0/24240.211.147.1 to 240.211.147.254240.211.147.255254
149240.211.148.0/24240.211.148.1 to 240.211.148.254240.211.148.255254
150240.211.149.0/24240.211.149.1 to 240.211.149.254240.211.149.255254
151240.211.150.0/24240.211.150.1 to 240.211.150.254240.211.150.255254
152240.211.151.0/24240.211.151.1 to 240.211.151.254240.211.151.255254
153240.211.152.0/24240.211.152.1 to 240.211.152.254240.211.152.255254
154240.211.153.0/24240.211.153.1 to 240.211.153.254240.211.153.255254
155240.211.154.0/24240.211.154.1 to 240.211.154.254240.211.154.255254
156240.211.155.0/24240.211.155.1 to 240.211.155.254240.211.155.255254
157240.211.156.0/24240.211.156.1 to 240.211.156.254240.211.156.255254
158240.211.157.0/24240.211.157.1 to 240.211.157.254240.211.157.255254
159240.211.158.0/24240.211.158.1 to 240.211.158.254240.211.158.255254
160240.211.159.0/24240.211.159.1 to 240.211.159.254240.211.159.255254
161240.211.160.0/24240.211.160.1 to 240.211.160.254240.211.160.255254
162240.211.161.0/24240.211.161.1 to 240.211.161.254240.211.161.255254
163240.211.162.0/24240.211.162.1 to 240.211.162.254240.211.162.255254
164240.211.163.0/24240.211.163.1 to 240.211.163.254240.211.163.255254
165240.211.164.0/24240.211.164.1 to 240.211.164.254240.211.164.255254
166240.211.165.0/24240.211.165.1 to 240.211.165.254240.211.165.255254
167240.211.166.0/24240.211.166.1 to 240.211.166.254240.211.166.255254
168240.211.167.0/24240.211.167.1 to 240.211.167.254240.211.167.255254
169240.211.168.0/24240.211.168.1 to 240.211.168.254240.211.168.255254
170240.211.169.0/24240.211.169.1 to 240.211.169.254240.211.169.255254
171240.211.170.0/24240.211.170.1 to 240.211.170.254240.211.170.255254
172240.211.171.0/24240.211.171.1 to 240.211.171.254240.211.171.255254
173240.211.172.0/24240.211.172.1 to 240.211.172.254240.211.172.255254
174240.211.173.0/24240.211.173.1 to 240.211.173.254240.211.173.255254
175240.211.174.0/24240.211.174.1 to 240.211.174.254240.211.174.255254
176240.211.175.0/24240.211.175.1 to 240.211.175.254240.211.175.255254
177240.211.176.0/24240.211.176.1 to 240.211.176.254240.211.176.255254
178240.211.177.0/24240.211.177.1 to 240.211.177.254240.211.177.255254
179240.211.178.0/24240.211.178.1 to 240.211.178.254240.211.178.255254
180240.211.179.0/24240.211.179.1 to 240.211.179.254240.211.179.255254
181240.211.180.0/24240.211.180.1 to 240.211.180.254240.211.180.255254
182240.211.181.0/24240.211.181.1 to 240.211.181.254240.211.181.255254
183240.211.182.0/24240.211.182.1 to 240.211.182.254240.211.182.255254
184240.211.183.0/24240.211.183.1 to 240.211.183.254240.211.183.255254
185240.211.184.0/24240.211.184.1 to 240.211.184.254240.211.184.255254
186240.211.185.0/24240.211.185.1 to 240.211.185.254240.211.185.255254
187240.211.186.0/24240.211.186.1 to 240.211.186.254240.211.186.255254
188240.211.187.0/24240.211.187.1 to 240.211.187.254240.211.187.255254
189240.211.188.0/24240.211.188.1 to 240.211.188.254240.211.188.255254
190240.211.189.0/24240.211.189.1 to 240.211.189.254240.211.189.255254
191240.211.190.0/24240.211.190.1 to 240.211.190.254240.211.190.255254
192240.211.191.0/24240.211.191.1 to 240.211.191.254240.211.191.255254
193240.211.192.0/24240.211.192.1 to 240.211.192.254240.211.192.255254
194240.211.193.0/24240.211.193.1 to 240.211.193.254240.211.193.255254
195240.211.194.0/24240.211.194.1 to 240.211.194.254240.211.194.255254
196240.211.195.0/24240.211.195.1 to 240.211.195.254240.211.195.255254
197240.211.196.0/24240.211.196.1 to 240.211.196.254240.211.196.255254
198240.211.197.0/24240.211.197.1 to 240.211.197.254240.211.197.255254
199240.211.198.0/24240.211.198.1 to 240.211.198.254240.211.198.255254
200240.211.199.0/24240.211.199.1 to 240.211.199.254240.211.199.255254
201240.211.200.0/24240.211.200.1 to 240.211.200.254240.211.200.255254
202240.211.201.0/24240.211.201.1 to 240.211.201.254240.211.201.255254
203240.211.202.0/24240.211.202.1 to 240.211.202.254240.211.202.255254
204240.211.203.0/24240.211.203.1 to 240.211.203.254240.211.203.255254
205240.211.204.0/24240.211.204.1 to 240.211.204.254240.211.204.255254
206240.211.205.0/24240.211.205.1 to 240.211.205.254240.211.205.255254
207240.211.206.0/24240.211.206.1 to 240.211.206.254240.211.206.255254
208240.211.207.0/24240.211.207.1 to 240.211.207.254240.211.207.255254
209240.211.208.0/24240.211.208.1 to 240.211.208.254240.211.208.255254
210240.211.209.0/24240.211.209.1 to 240.211.209.254240.211.209.255254
211240.211.210.0/24240.211.210.1 to 240.211.210.254240.211.210.255254
212240.211.211.0/24240.211.211.1 to 240.211.211.254240.211.211.255254
213240.211.212.0/24240.211.212.1 to 240.211.212.254240.211.212.255254
214240.211.213.0/24240.211.213.1 to 240.211.213.254240.211.213.255254
215240.211.214.0/24240.211.214.1 to 240.211.214.254240.211.214.255254
216240.211.215.0/24240.211.215.1 to 240.211.215.254240.211.215.255254
217240.211.216.0/24240.211.216.1 to 240.211.216.254240.211.216.255254
218240.211.217.0/24240.211.217.1 to 240.211.217.254240.211.217.255254
219240.211.218.0/24240.211.218.1 to 240.211.218.254240.211.218.255254
220240.211.219.0/24240.211.219.1 to 240.211.219.254240.211.219.255254
221240.211.220.0/24240.211.220.1 to 240.211.220.254240.211.220.255254
222240.211.221.0/24240.211.221.1 to 240.211.221.254240.211.221.255254
223240.211.222.0/24240.211.222.1 to 240.211.222.254240.211.222.255254
224240.211.223.0/24240.211.223.1 to 240.211.223.254240.211.223.255254
225240.211.224.0/24240.211.224.1 to 240.211.224.254240.211.224.255254
226240.211.225.0/24240.211.225.1 to 240.211.225.254240.211.225.255254
227240.211.226.0/24240.211.226.1 to 240.211.226.254240.211.226.255254
228240.211.227.0/24240.211.227.1 to 240.211.227.254240.211.227.255254
229240.211.228.0/24240.211.228.1 to 240.211.228.254240.211.228.255254
230240.211.229.0/24240.211.229.1 to 240.211.229.254240.211.229.255254
231240.211.230.0/24240.211.230.1 to 240.211.230.254240.211.230.255254
232240.211.231.0/24240.211.231.1 to 240.211.231.254240.211.231.255254
233240.211.232.0/24240.211.232.1 to 240.211.232.254240.211.232.255254
234240.211.233.0/24240.211.233.1 to 240.211.233.254240.211.233.255254
235240.211.234.0/24240.211.234.1 to 240.211.234.254240.211.234.255254
236240.211.235.0/24240.211.235.1 to 240.211.235.254240.211.235.255254
237240.211.236.0/24240.211.236.1 to 240.211.236.254240.211.236.255254
238240.211.237.0/24240.211.237.1 to 240.211.237.254240.211.237.255254
239240.211.238.0/24240.211.238.1 to 240.211.238.254240.211.238.255254
240240.211.239.0/24240.211.239.1 to 240.211.239.254240.211.239.255254
241240.211.240.0/24240.211.240.1 to 240.211.240.254240.211.240.255254
242240.211.241.0/24240.211.241.1 to 240.211.241.254240.211.241.255254
243240.211.242.0/24240.211.242.1 to 240.211.242.254240.211.242.255254
244240.211.243.0/24240.211.243.1 to 240.211.243.254240.211.243.255254
245240.211.244.0/24240.211.244.1 to 240.211.244.254240.211.244.255254
246240.211.245.0/24240.211.245.1 to 240.211.245.254240.211.245.255254
247240.211.246.0/24240.211.246.1 to 240.211.246.254240.211.246.255254
248240.211.247.0/24240.211.247.1 to 240.211.247.254240.211.247.255254
249240.211.248.0/24240.211.248.1 to 240.211.248.254240.211.248.255254
250240.211.249.0/24240.211.249.1 to 240.211.249.254240.211.249.255254
251240.211.250.0/24240.211.250.1 to 240.211.250.254240.211.250.255254
252240.211.251.0/24240.211.251.1 to 240.211.251.254240.211.251.255254
253240.211.252.0/24240.211.252.1 to 240.211.252.254240.211.252.255254
254240.211.253.0/24240.211.253.1 to 240.211.253.254240.211.253.255254
255240.211.254.0/24240.211.254.1 to 240.211.254.254240.211.254.255254
256240.211.255.0/24240.211.255.1 to 240.211.255.254240.211.255.255254

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.