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.

Network242.200.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
242.200.0.0
Broadcast address
242.207.255.255
First usable
242.200.0.1
Last usable
242.207.255.254
Usable hosts
524,286 (524,288 less the network and broadcast addresses)
Subnet mask
255.248.0.0
Wildcard mask
0.7.255.255 (Cisco ACLs, OSPF)
Prefix length
/13
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F2C80000 · Integer 4073193472 to 4073717759
Reverse DNS zones
200.242.in-addr.arpa
201.242.in-addr.arpa
202.242.in-addr.arpa
203.242.in-addr.arpa
204.242.in-addr.arpa
205.242.in-addr.arpa
206.242.in-addr.arpa
207.242.in-addr.arpa
/13 is not on a 8-bit boundary, so it takes 8 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11110010.11001000.00000000.00000000242.200.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network11110010.11001000.00000000.00000000242.200.0.0
Broadcast11110010.11001111.11111111.11111111242.207.255.255
Split into smaller subnets/23
/14 (2)/15 (4)/16 (8)/17 (16)/18 (32)/19 (64)/20 (128)/21 (256)/22 (512)/23 (1,024)/24 (2,048)/25 (4,096)

242.200.0.0/13 makes 1,024 subnets of /23; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1242.200.0.0/23242.200.0.1 to 242.200.1.254242.200.1.255510
2242.200.2.0/23242.200.2.1 to 242.200.3.254242.200.3.255510
3242.200.4.0/23242.200.4.1 to 242.200.5.254242.200.5.255510
4242.200.6.0/23242.200.6.1 to 242.200.7.254242.200.7.255510
5242.200.8.0/23242.200.8.1 to 242.200.9.254242.200.9.255510
6242.200.10.0/23242.200.10.1 to 242.200.11.254242.200.11.255510
7242.200.12.0/23242.200.12.1 to 242.200.13.254242.200.13.255510
8242.200.14.0/23242.200.14.1 to 242.200.15.254242.200.15.255510
9242.200.16.0/23242.200.16.1 to 242.200.17.254242.200.17.255510
10242.200.18.0/23242.200.18.1 to 242.200.19.254242.200.19.255510
11242.200.20.0/23242.200.20.1 to 242.200.21.254242.200.21.255510
12242.200.22.0/23242.200.22.1 to 242.200.23.254242.200.23.255510
13242.200.24.0/23242.200.24.1 to 242.200.25.254242.200.25.255510
14242.200.26.0/23242.200.26.1 to 242.200.27.254242.200.27.255510
15242.200.28.0/23242.200.28.1 to 242.200.29.254242.200.29.255510
16242.200.30.0/23242.200.30.1 to 242.200.31.254242.200.31.255510
17242.200.32.0/23242.200.32.1 to 242.200.33.254242.200.33.255510
18242.200.34.0/23242.200.34.1 to 242.200.35.254242.200.35.255510
19242.200.36.0/23242.200.36.1 to 242.200.37.254242.200.37.255510
20242.200.38.0/23242.200.38.1 to 242.200.39.254242.200.39.255510
21242.200.40.0/23242.200.40.1 to 242.200.41.254242.200.41.255510
22242.200.42.0/23242.200.42.1 to 242.200.43.254242.200.43.255510
23242.200.44.0/23242.200.44.1 to 242.200.45.254242.200.45.255510
24242.200.46.0/23242.200.46.1 to 242.200.47.254242.200.47.255510
25242.200.48.0/23242.200.48.1 to 242.200.49.254242.200.49.255510
26242.200.50.0/23242.200.50.1 to 242.200.51.254242.200.51.255510
27242.200.52.0/23242.200.52.1 to 242.200.53.254242.200.53.255510
28242.200.54.0/23242.200.54.1 to 242.200.55.254242.200.55.255510
29242.200.56.0/23242.200.56.1 to 242.200.57.254242.200.57.255510
30242.200.58.0/23242.200.58.1 to 242.200.59.254242.200.59.255510
31242.200.60.0/23242.200.60.1 to 242.200.61.254242.200.61.255510
32242.200.62.0/23242.200.62.1 to 242.200.63.254242.200.63.255510
33242.200.64.0/23242.200.64.1 to 242.200.65.254242.200.65.255510
34242.200.66.0/23242.200.66.1 to 242.200.67.254242.200.67.255510
35242.200.68.0/23242.200.68.1 to 242.200.69.254242.200.69.255510
36242.200.70.0/23242.200.70.1 to 242.200.71.254242.200.71.255510
37242.200.72.0/23242.200.72.1 to 242.200.73.254242.200.73.255510
38242.200.74.0/23242.200.74.1 to 242.200.75.254242.200.75.255510
39242.200.76.0/23242.200.76.1 to 242.200.77.254242.200.77.255510
40242.200.78.0/23242.200.78.1 to 242.200.79.254242.200.79.255510
41242.200.80.0/23242.200.80.1 to 242.200.81.254242.200.81.255510
42242.200.82.0/23242.200.82.1 to 242.200.83.254242.200.83.255510
43242.200.84.0/23242.200.84.1 to 242.200.85.254242.200.85.255510
44242.200.86.0/23242.200.86.1 to 242.200.87.254242.200.87.255510
45242.200.88.0/23242.200.88.1 to 242.200.89.254242.200.89.255510
46242.200.90.0/23242.200.90.1 to 242.200.91.254242.200.91.255510
47242.200.92.0/23242.200.92.1 to 242.200.93.254242.200.93.255510
48242.200.94.0/23242.200.94.1 to 242.200.95.254242.200.95.255510
49242.200.96.0/23242.200.96.1 to 242.200.97.254242.200.97.255510
50242.200.98.0/23242.200.98.1 to 242.200.99.254242.200.99.255510
51242.200.100.0/23242.200.100.1 to 242.200.101.254242.200.101.255510
52242.200.102.0/23242.200.102.1 to 242.200.103.254242.200.103.255510
53242.200.104.0/23242.200.104.1 to 242.200.105.254242.200.105.255510
54242.200.106.0/23242.200.106.1 to 242.200.107.254242.200.107.255510
55242.200.108.0/23242.200.108.1 to 242.200.109.254242.200.109.255510
56242.200.110.0/23242.200.110.1 to 242.200.111.254242.200.111.255510
57242.200.112.0/23242.200.112.1 to 242.200.113.254242.200.113.255510
58242.200.114.0/23242.200.114.1 to 242.200.115.254242.200.115.255510
59242.200.116.0/23242.200.116.1 to 242.200.117.254242.200.117.255510
60242.200.118.0/23242.200.118.1 to 242.200.119.254242.200.119.255510
61242.200.120.0/23242.200.120.1 to 242.200.121.254242.200.121.255510
62242.200.122.0/23242.200.122.1 to 242.200.123.254242.200.123.255510
63242.200.124.0/23242.200.124.1 to 242.200.125.254242.200.125.255510
64242.200.126.0/23242.200.126.1 to 242.200.127.254242.200.127.255510
65242.200.128.0/23242.200.128.1 to 242.200.129.254242.200.129.255510
66242.200.130.0/23242.200.130.1 to 242.200.131.254242.200.131.255510
67242.200.132.0/23242.200.132.1 to 242.200.133.254242.200.133.255510
68242.200.134.0/23242.200.134.1 to 242.200.135.254242.200.135.255510
69242.200.136.0/23242.200.136.1 to 242.200.137.254242.200.137.255510
70242.200.138.0/23242.200.138.1 to 242.200.139.254242.200.139.255510
71242.200.140.0/23242.200.140.1 to 242.200.141.254242.200.141.255510
72242.200.142.0/23242.200.142.1 to 242.200.143.254242.200.143.255510
73242.200.144.0/23242.200.144.1 to 242.200.145.254242.200.145.255510
74242.200.146.0/23242.200.146.1 to 242.200.147.254242.200.147.255510
75242.200.148.0/23242.200.148.1 to 242.200.149.254242.200.149.255510
76242.200.150.0/23242.200.150.1 to 242.200.151.254242.200.151.255510
77242.200.152.0/23242.200.152.1 to 242.200.153.254242.200.153.255510
78242.200.154.0/23242.200.154.1 to 242.200.155.254242.200.155.255510
79242.200.156.0/23242.200.156.1 to 242.200.157.254242.200.157.255510
80242.200.158.0/23242.200.158.1 to 242.200.159.254242.200.159.255510
81242.200.160.0/23242.200.160.1 to 242.200.161.254242.200.161.255510
82242.200.162.0/23242.200.162.1 to 242.200.163.254242.200.163.255510
83242.200.164.0/23242.200.164.1 to 242.200.165.254242.200.165.255510
84242.200.166.0/23242.200.166.1 to 242.200.167.254242.200.167.255510
85242.200.168.0/23242.200.168.1 to 242.200.169.254242.200.169.255510
86242.200.170.0/23242.200.170.1 to 242.200.171.254242.200.171.255510
87242.200.172.0/23242.200.172.1 to 242.200.173.254242.200.173.255510
88242.200.174.0/23242.200.174.1 to 242.200.175.254242.200.175.255510
89242.200.176.0/23242.200.176.1 to 242.200.177.254242.200.177.255510
90242.200.178.0/23242.200.178.1 to 242.200.179.254242.200.179.255510
91242.200.180.0/23242.200.180.1 to 242.200.181.254242.200.181.255510
92242.200.182.0/23242.200.182.1 to 242.200.183.254242.200.183.255510
93242.200.184.0/23242.200.184.1 to 242.200.185.254242.200.185.255510
94242.200.186.0/23242.200.186.1 to 242.200.187.254242.200.187.255510
95242.200.188.0/23242.200.188.1 to 242.200.189.254242.200.189.255510
96242.200.190.0/23242.200.190.1 to 242.200.191.254242.200.191.255510
97242.200.192.0/23242.200.192.1 to 242.200.193.254242.200.193.255510
98242.200.194.0/23242.200.194.1 to 242.200.195.254242.200.195.255510
99242.200.196.0/23242.200.196.1 to 242.200.197.254242.200.197.255510
100242.200.198.0/23242.200.198.1 to 242.200.199.254242.200.199.255510
101242.200.200.0/23242.200.200.1 to 242.200.201.254242.200.201.255510
102242.200.202.0/23242.200.202.1 to 242.200.203.254242.200.203.255510
103242.200.204.0/23242.200.204.1 to 242.200.205.254242.200.205.255510
104242.200.206.0/23242.200.206.1 to 242.200.207.254242.200.207.255510
105242.200.208.0/23242.200.208.1 to 242.200.209.254242.200.209.255510
106242.200.210.0/23242.200.210.1 to 242.200.211.254242.200.211.255510
107242.200.212.0/23242.200.212.1 to 242.200.213.254242.200.213.255510
108242.200.214.0/23242.200.214.1 to 242.200.215.254242.200.215.255510
109242.200.216.0/23242.200.216.1 to 242.200.217.254242.200.217.255510
110242.200.218.0/23242.200.218.1 to 242.200.219.254242.200.219.255510
111242.200.220.0/23242.200.220.1 to 242.200.221.254242.200.221.255510
112242.200.222.0/23242.200.222.1 to 242.200.223.254242.200.223.255510
113242.200.224.0/23242.200.224.1 to 242.200.225.254242.200.225.255510
114242.200.226.0/23242.200.226.1 to 242.200.227.254242.200.227.255510
115242.200.228.0/23242.200.228.1 to 242.200.229.254242.200.229.255510
116242.200.230.0/23242.200.230.1 to 242.200.231.254242.200.231.255510
117242.200.232.0/23242.200.232.1 to 242.200.233.254242.200.233.255510
118242.200.234.0/23242.200.234.1 to 242.200.235.254242.200.235.255510
119242.200.236.0/23242.200.236.1 to 242.200.237.254242.200.237.255510
120242.200.238.0/23242.200.238.1 to 242.200.239.254242.200.239.255510
121242.200.240.0/23242.200.240.1 to 242.200.241.254242.200.241.255510
122242.200.242.0/23242.200.242.1 to 242.200.243.254242.200.243.255510
123242.200.244.0/23242.200.244.1 to 242.200.245.254242.200.245.255510
124242.200.246.0/23242.200.246.1 to 242.200.247.254242.200.247.255510
125242.200.248.0/23242.200.248.1 to 242.200.249.254242.200.249.255510
126242.200.250.0/23242.200.250.1 to 242.200.251.254242.200.251.255510
127242.200.252.0/23242.200.252.1 to 242.200.253.254242.200.253.255510
128242.200.254.0/23242.200.254.1 to 242.200.255.254242.200.255.255510
129242.201.0.0/23242.201.0.1 to 242.201.1.254242.201.1.255510
130242.201.2.0/23242.201.2.1 to 242.201.3.254242.201.3.255510
131242.201.4.0/23242.201.4.1 to 242.201.5.254242.201.5.255510
132242.201.6.0/23242.201.6.1 to 242.201.7.254242.201.7.255510
133242.201.8.0/23242.201.8.1 to 242.201.9.254242.201.9.255510
134242.201.10.0/23242.201.10.1 to 242.201.11.254242.201.11.255510
135242.201.12.0/23242.201.12.1 to 242.201.13.254242.201.13.255510
136242.201.14.0/23242.201.14.1 to 242.201.15.254242.201.15.255510
137242.201.16.0/23242.201.16.1 to 242.201.17.254242.201.17.255510
138242.201.18.0/23242.201.18.1 to 242.201.19.254242.201.19.255510
139242.201.20.0/23242.201.20.1 to 242.201.21.254242.201.21.255510
140242.201.22.0/23242.201.22.1 to 242.201.23.254242.201.23.255510
141242.201.24.0/23242.201.24.1 to 242.201.25.254242.201.25.255510
142242.201.26.0/23242.201.26.1 to 242.201.27.254242.201.27.255510
143242.201.28.0/23242.201.28.1 to 242.201.29.254242.201.29.255510
144242.201.30.0/23242.201.30.1 to 242.201.31.254242.201.31.255510
145242.201.32.0/23242.201.32.1 to 242.201.33.254242.201.33.255510
146242.201.34.0/23242.201.34.1 to 242.201.35.254242.201.35.255510
147242.201.36.0/23242.201.36.1 to 242.201.37.254242.201.37.255510
148242.201.38.0/23242.201.38.1 to 242.201.39.254242.201.39.255510
149242.201.40.0/23242.201.40.1 to 242.201.41.254242.201.41.255510
150242.201.42.0/23242.201.42.1 to 242.201.43.254242.201.43.255510
151242.201.44.0/23242.201.44.1 to 242.201.45.254242.201.45.255510
152242.201.46.0/23242.201.46.1 to 242.201.47.254242.201.47.255510
153242.201.48.0/23242.201.48.1 to 242.201.49.254242.201.49.255510
154242.201.50.0/23242.201.50.1 to 242.201.51.254242.201.51.255510
155242.201.52.0/23242.201.52.1 to 242.201.53.254242.201.53.255510
156242.201.54.0/23242.201.54.1 to 242.201.55.254242.201.55.255510
157242.201.56.0/23242.201.56.1 to 242.201.57.254242.201.57.255510
158242.201.58.0/23242.201.58.1 to 242.201.59.254242.201.59.255510
159242.201.60.0/23242.201.60.1 to 242.201.61.254242.201.61.255510
160242.201.62.0/23242.201.62.1 to 242.201.63.254242.201.63.255510
161242.201.64.0/23242.201.64.1 to 242.201.65.254242.201.65.255510
162242.201.66.0/23242.201.66.1 to 242.201.67.254242.201.67.255510
163242.201.68.0/23242.201.68.1 to 242.201.69.254242.201.69.255510
164242.201.70.0/23242.201.70.1 to 242.201.71.254242.201.71.255510
165242.201.72.0/23242.201.72.1 to 242.201.73.254242.201.73.255510
166242.201.74.0/23242.201.74.1 to 242.201.75.254242.201.75.255510
167242.201.76.0/23242.201.76.1 to 242.201.77.254242.201.77.255510
168242.201.78.0/23242.201.78.1 to 242.201.79.254242.201.79.255510
169242.201.80.0/23242.201.80.1 to 242.201.81.254242.201.81.255510
170242.201.82.0/23242.201.82.1 to 242.201.83.254242.201.83.255510
171242.201.84.0/23242.201.84.1 to 242.201.85.254242.201.85.255510
172242.201.86.0/23242.201.86.1 to 242.201.87.254242.201.87.255510
173242.201.88.0/23242.201.88.1 to 242.201.89.254242.201.89.255510
174242.201.90.0/23242.201.90.1 to 242.201.91.254242.201.91.255510
175242.201.92.0/23242.201.92.1 to 242.201.93.254242.201.93.255510
176242.201.94.0/23242.201.94.1 to 242.201.95.254242.201.95.255510
177242.201.96.0/23242.201.96.1 to 242.201.97.254242.201.97.255510
178242.201.98.0/23242.201.98.1 to 242.201.99.254242.201.99.255510
179242.201.100.0/23242.201.100.1 to 242.201.101.254242.201.101.255510
180242.201.102.0/23242.201.102.1 to 242.201.103.254242.201.103.255510
181242.201.104.0/23242.201.104.1 to 242.201.105.254242.201.105.255510
182242.201.106.0/23242.201.106.1 to 242.201.107.254242.201.107.255510
183242.201.108.0/23242.201.108.1 to 242.201.109.254242.201.109.255510
184242.201.110.0/23242.201.110.1 to 242.201.111.254242.201.111.255510
185242.201.112.0/23242.201.112.1 to 242.201.113.254242.201.113.255510
186242.201.114.0/23242.201.114.1 to 242.201.115.254242.201.115.255510
187242.201.116.0/23242.201.116.1 to 242.201.117.254242.201.117.255510
188242.201.118.0/23242.201.118.1 to 242.201.119.254242.201.119.255510
189242.201.120.0/23242.201.120.1 to 242.201.121.254242.201.121.255510
190242.201.122.0/23242.201.122.1 to 242.201.123.254242.201.123.255510
191242.201.124.0/23242.201.124.1 to 242.201.125.254242.201.125.255510
192242.201.126.0/23242.201.126.1 to 242.201.127.254242.201.127.255510
193242.201.128.0/23242.201.128.1 to 242.201.129.254242.201.129.255510
194242.201.130.0/23242.201.130.1 to 242.201.131.254242.201.131.255510
195242.201.132.0/23242.201.132.1 to 242.201.133.254242.201.133.255510
196242.201.134.0/23242.201.134.1 to 242.201.135.254242.201.135.255510
197242.201.136.0/23242.201.136.1 to 242.201.137.254242.201.137.255510
198242.201.138.0/23242.201.138.1 to 242.201.139.254242.201.139.255510
199242.201.140.0/23242.201.140.1 to 242.201.141.254242.201.141.255510
200242.201.142.0/23242.201.142.1 to 242.201.143.254242.201.143.255510
201242.201.144.0/23242.201.144.1 to 242.201.145.254242.201.145.255510
202242.201.146.0/23242.201.146.1 to 242.201.147.254242.201.147.255510
203242.201.148.0/23242.201.148.1 to 242.201.149.254242.201.149.255510
204242.201.150.0/23242.201.150.1 to 242.201.151.254242.201.151.255510
205242.201.152.0/23242.201.152.1 to 242.201.153.254242.201.153.255510
206242.201.154.0/23242.201.154.1 to 242.201.155.254242.201.155.255510
207242.201.156.0/23242.201.156.1 to 242.201.157.254242.201.157.255510
208242.201.158.0/23242.201.158.1 to 242.201.159.254242.201.159.255510
209242.201.160.0/23242.201.160.1 to 242.201.161.254242.201.161.255510
210242.201.162.0/23242.201.162.1 to 242.201.163.254242.201.163.255510
211242.201.164.0/23242.201.164.1 to 242.201.165.254242.201.165.255510
212242.201.166.0/23242.201.166.1 to 242.201.167.254242.201.167.255510
213242.201.168.0/23242.201.168.1 to 242.201.169.254242.201.169.255510
214242.201.170.0/23242.201.170.1 to 242.201.171.254242.201.171.255510
215242.201.172.0/23242.201.172.1 to 242.201.173.254242.201.173.255510
216242.201.174.0/23242.201.174.1 to 242.201.175.254242.201.175.255510
217242.201.176.0/23242.201.176.1 to 242.201.177.254242.201.177.255510
218242.201.178.0/23242.201.178.1 to 242.201.179.254242.201.179.255510
219242.201.180.0/23242.201.180.1 to 242.201.181.254242.201.181.255510
220242.201.182.0/23242.201.182.1 to 242.201.183.254242.201.183.255510
221242.201.184.0/23242.201.184.1 to 242.201.185.254242.201.185.255510
222242.201.186.0/23242.201.186.1 to 242.201.187.254242.201.187.255510
223242.201.188.0/23242.201.188.1 to 242.201.189.254242.201.189.255510
224242.201.190.0/23242.201.190.1 to 242.201.191.254242.201.191.255510
225242.201.192.0/23242.201.192.1 to 242.201.193.254242.201.193.255510
226242.201.194.0/23242.201.194.1 to 242.201.195.254242.201.195.255510
227242.201.196.0/23242.201.196.1 to 242.201.197.254242.201.197.255510
228242.201.198.0/23242.201.198.1 to 242.201.199.254242.201.199.255510
229242.201.200.0/23242.201.200.1 to 242.201.201.254242.201.201.255510
230242.201.202.0/23242.201.202.1 to 242.201.203.254242.201.203.255510
231242.201.204.0/23242.201.204.1 to 242.201.205.254242.201.205.255510
232242.201.206.0/23242.201.206.1 to 242.201.207.254242.201.207.255510
233242.201.208.0/23242.201.208.1 to 242.201.209.254242.201.209.255510
234242.201.210.0/23242.201.210.1 to 242.201.211.254242.201.211.255510
235242.201.212.0/23242.201.212.1 to 242.201.213.254242.201.213.255510
236242.201.214.0/23242.201.214.1 to 242.201.215.254242.201.215.255510
237242.201.216.0/23242.201.216.1 to 242.201.217.254242.201.217.255510
238242.201.218.0/23242.201.218.1 to 242.201.219.254242.201.219.255510
239242.201.220.0/23242.201.220.1 to 242.201.221.254242.201.221.255510
240242.201.222.0/23242.201.222.1 to 242.201.223.254242.201.223.255510
241242.201.224.0/23242.201.224.1 to 242.201.225.254242.201.225.255510
242242.201.226.0/23242.201.226.1 to 242.201.227.254242.201.227.255510
243242.201.228.0/23242.201.228.1 to 242.201.229.254242.201.229.255510
244242.201.230.0/23242.201.230.1 to 242.201.231.254242.201.231.255510
245242.201.232.0/23242.201.232.1 to 242.201.233.254242.201.233.255510
246242.201.234.0/23242.201.234.1 to 242.201.235.254242.201.235.255510
247242.201.236.0/23242.201.236.1 to 242.201.237.254242.201.237.255510
248242.201.238.0/23242.201.238.1 to 242.201.239.254242.201.239.255510
249242.201.240.0/23242.201.240.1 to 242.201.241.254242.201.241.255510
250242.201.242.0/23242.201.242.1 to 242.201.243.254242.201.243.255510
251242.201.244.0/23242.201.244.1 to 242.201.245.254242.201.245.255510
252242.201.246.0/23242.201.246.1 to 242.201.247.254242.201.247.255510
253242.201.248.0/23242.201.248.1 to 242.201.249.254242.201.249.255510
254242.201.250.0/23242.201.250.1 to 242.201.251.254242.201.251.255510
255242.201.252.0/23242.201.252.1 to 242.201.253.254242.201.253.255510
256242.201.254.0/23242.201.254.1 to 242.201.255.254242.201.255.255510

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.