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.

Network187.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
187.0.0.0
Broadcast address
187.255.255.255
First usable
187.0.0.1
Last usable
187.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Public public
Old class
B (default /16)
As numbers
Hex BB000000 · Integer 3137339392 to 3154116607
Reverse DNS zone
187.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10111011..00000000.00000000.00000000187.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network10111011..00000000.00000000.00000000187.0.0.0
Broadcast10111011..11111111.11111111.11111111187.255.255.255
Split into smaller subnets/16
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

187.0.0.0/8 makes 256 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1187.0.0.0/16187.0.0.1 to 187.0.255.254187.0.255.25565,534
2187.1.0.0/16187.1.0.1 to 187.1.255.254187.1.255.25565,534
3187.2.0.0/16187.2.0.1 to 187.2.255.254187.2.255.25565,534
4187.3.0.0/16187.3.0.1 to 187.3.255.254187.3.255.25565,534
5187.4.0.0/16187.4.0.1 to 187.4.255.254187.4.255.25565,534
6187.5.0.0/16187.5.0.1 to 187.5.255.254187.5.255.25565,534
7187.6.0.0/16187.6.0.1 to 187.6.255.254187.6.255.25565,534
8187.7.0.0/16187.7.0.1 to 187.7.255.254187.7.255.25565,534
9187.8.0.0/16187.8.0.1 to 187.8.255.254187.8.255.25565,534
10187.9.0.0/16187.9.0.1 to 187.9.255.254187.9.255.25565,534
11187.10.0.0/16187.10.0.1 to 187.10.255.254187.10.255.25565,534
12187.11.0.0/16187.11.0.1 to 187.11.255.254187.11.255.25565,534
13187.12.0.0/16187.12.0.1 to 187.12.255.254187.12.255.25565,534
14187.13.0.0/16187.13.0.1 to 187.13.255.254187.13.255.25565,534
15187.14.0.0/16187.14.0.1 to 187.14.255.254187.14.255.25565,534
16187.15.0.0/16187.15.0.1 to 187.15.255.254187.15.255.25565,534
17187.16.0.0/16187.16.0.1 to 187.16.255.254187.16.255.25565,534
18187.17.0.0/16187.17.0.1 to 187.17.255.254187.17.255.25565,534
19187.18.0.0/16187.18.0.1 to 187.18.255.254187.18.255.25565,534
20187.19.0.0/16187.19.0.1 to 187.19.255.254187.19.255.25565,534
21187.20.0.0/16187.20.0.1 to 187.20.255.254187.20.255.25565,534
22187.21.0.0/16187.21.0.1 to 187.21.255.254187.21.255.25565,534
23187.22.0.0/16187.22.0.1 to 187.22.255.254187.22.255.25565,534
24187.23.0.0/16187.23.0.1 to 187.23.255.254187.23.255.25565,534
25187.24.0.0/16187.24.0.1 to 187.24.255.254187.24.255.25565,534
26187.25.0.0/16187.25.0.1 to 187.25.255.254187.25.255.25565,534
27187.26.0.0/16187.26.0.1 to 187.26.255.254187.26.255.25565,534
28187.27.0.0/16187.27.0.1 to 187.27.255.254187.27.255.25565,534
29187.28.0.0/16187.28.0.1 to 187.28.255.254187.28.255.25565,534
30187.29.0.0/16187.29.0.1 to 187.29.255.254187.29.255.25565,534
31187.30.0.0/16187.30.0.1 to 187.30.255.254187.30.255.25565,534
32187.31.0.0/16187.31.0.1 to 187.31.255.254187.31.255.25565,534
33187.32.0.0/16187.32.0.1 to 187.32.255.254187.32.255.25565,534
34187.33.0.0/16187.33.0.1 to 187.33.255.254187.33.255.25565,534
35187.34.0.0/16187.34.0.1 to 187.34.255.254187.34.255.25565,534
36187.35.0.0/16187.35.0.1 to 187.35.255.254187.35.255.25565,534
37187.36.0.0/16187.36.0.1 to 187.36.255.254187.36.255.25565,534
38187.37.0.0/16187.37.0.1 to 187.37.255.254187.37.255.25565,534
39187.38.0.0/16187.38.0.1 to 187.38.255.254187.38.255.25565,534
40187.39.0.0/16187.39.0.1 to 187.39.255.254187.39.255.25565,534
41187.40.0.0/16187.40.0.1 to 187.40.255.254187.40.255.25565,534
42187.41.0.0/16187.41.0.1 to 187.41.255.254187.41.255.25565,534
43187.42.0.0/16187.42.0.1 to 187.42.255.254187.42.255.25565,534
44187.43.0.0/16187.43.0.1 to 187.43.255.254187.43.255.25565,534
45187.44.0.0/16187.44.0.1 to 187.44.255.254187.44.255.25565,534
46187.45.0.0/16187.45.0.1 to 187.45.255.254187.45.255.25565,534
47187.46.0.0/16187.46.0.1 to 187.46.255.254187.46.255.25565,534
48187.47.0.0/16187.47.0.1 to 187.47.255.254187.47.255.25565,534
49187.48.0.0/16187.48.0.1 to 187.48.255.254187.48.255.25565,534
50187.49.0.0/16187.49.0.1 to 187.49.255.254187.49.255.25565,534
51187.50.0.0/16187.50.0.1 to 187.50.255.254187.50.255.25565,534
52187.51.0.0/16187.51.0.1 to 187.51.255.254187.51.255.25565,534
53187.52.0.0/16187.52.0.1 to 187.52.255.254187.52.255.25565,534
54187.53.0.0/16187.53.0.1 to 187.53.255.254187.53.255.25565,534
55187.54.0.0/16187.54.0.1 to 187.54.255.254187.54.255.25565,534
56187.55.0.0/16187.55.0.1 to 187.55.255.254187.55.255.25565,534
57187.56.0.0/16187.56.0.1 to 187.56.255.254187.56.255.25565,534
58187.57.0.0/16187.57.0.1 to 187.57.255.254187.57.255.25565,534
59187.58.0.0/16187.58.0.1 to 187.58.255.254187.58.255.25565,534
60187.59.0.0/16187.59.0.1 to 187.59.255.254187.59.255.25565,534
61187.60.0.0/16187.60.0.1 to 187.60.255.254187.60.255.25565,534
62187.61.0.0/16187.61.0.1 to 187.61.255.254187.61.255.25565,534
63187.62.0.0/16187.62.0.1 to 187.62.255.254187.62.255.25565,534
64187.63.0.0/16187.63.0.1 to 187.63.255.254187.63.255.25565,534
65187.64.0.0/16187.64.0.1 to 187.64.255.254187.64.255.25565,534
66187.65.0.0/16187.65.0.1 to 187.65.255.254187.65.255.25565,534
67187.66.0.0/16187.66.0.1 to 187.66.255.254187.66.255.25565,534
68187.67.0.0/16187.67.0.1 to 187.67.255.254187.67.255.25565,534
69187.68.0.0/16187.68.0.1 to 187.68.255.254187.68.255.25565,534
70187.69.0.0/16187.69.0.1 to 187.69.255.254187.69.255.25565,534
71187.70.0.0/16187.70.0.1 to 187.70.255.254187.70.255.25565,534
72187.71.0.0/16187.71.0.1 to 187.71.255.254187.71.255.25565,534
73187.72.0.0/16187.72.0.1 to 187.72.255.254187.72.255.25565,534
74187.73.0.0/16187.73.0.1 to 187.73.255.254187.73.255.25565,534
75187.74.0.0/16187.74.0.1 to 187.74.255.254187.74.255.25565,534
76187.75.0.0/16187.75.0.1 to 187.75.255.254187.75.255.25565,534
77187.76.0.0/16187.76.0.1 to 187.76.255.254187.76.255.25565,534
78187.77.0.0/16187.77.0.1 to 187.77.255.254187.77.255.25565,534
79187.78.0.0/16187.78.0.1 to 187.78.255.254187.78.255.25565,534
80187.79.0.0/16187.79.0.1 to 187.79.255.254187.79.255.25565,534
81187.80.0.0/16187.80.0.1 to 187.80.255.254187.80.255.25565,534
82187.81.0.0/16187.81.0.1 to 187.81.255.254187.81.255.25565,534
83187.82.0.0/16187.82.0.1 to 187.82.255.254187.82.255.25565,534
84187.83.0.0/16187.83.0.1 to 187.83.255.254187.83.255.25565,534
85187.84.0.0/16187.84.0.1 to 187.84.255.254187.84.255.25565,534
86187.85.0.0/16187.85.0.1 to 187.85.255.254187.85.255.25565,534
87187.86.0.0/16187.86.0.1 to 187.86.255.254187.86.255.25565,534
88187.87.0.0/16187.87.0.1 to 187.87.255.254187.87.255.25565,534
89187.88.0.0/16187.88.0.1 to 187.88.255.254187.88.255.25565,534
90187.89.0.0/16187.89.0.1 to 187.89.255.254187.89.255.25565,534
91187.90.0.0/16187.90.0.1 to 187.90.255.254187.90.255.25565,534
92187.91.0.0/16187.91.0.1 to 187.91.255.254187.91.255.25565,534
93187.92.0.0/16187.92.0.1 to 187.92.255.254187.92.255.25565,534
94187.93.0.0/16187.93.0.1 to 187.93.255.254187.93.255.25565,534
95187.94.0.0/16187.94.0.1 to 187.94.255.254187.94.255.25565,534
96187.95.0.0/16187.95.0.1 to 187.95.255.254187.95.255.25565,534
97187.96.0.0/16187.96.0.1 to 187.96.255.254187.96.255.25565,534
98187.97.0.0/16187.97.0.1 to 187.97.255.254187.97.255.25565,534
99187.98.0.0/16187.98.0.1 to 187.98.255.254187.98.255.25565,534
100187.99.0.0/16187.99.0.1 to 187.99.255.254187.99.255.25565,534
101187.100.0.0/16187.100.0.1 to 187.100.255.254187.100.255.25565,534
102187.101.0.0/16187.101.0.1 to 187.101.255.254187.101.255.25565,534
103187.102.0.0/16187.102.0.1 to 187.102.255.254187.102.255.25565,534
104187.103.0.0/16187.103.0.1 to 187.103.255.254187.103.255.25565,534
105187.104.0.0/16187.104.0.1 to 187.104.255.254187.104.255.25565,534
106187.105.0.0/16187.105.0.1 to 187.105.255.254187.105.255.25565,534
107187.106.0.0/16187.106.0.1 to 187.106.255.254187.106.255.25565,534
108187.107.0.0/16187.107.0.1 to 187.107.255.254187.107.255.25565,534
109187.108.0.0/16187.108.0.1 to 187.108.255.254187.108.255.25565,534
110187.109.0.0/16187.109.0.1 to 187.109.255.254187.109.255.25565,534
111187.110.0.0/16187.110.0.1 to 187.110.255.254187.110.255.25565,534
112187.111.0.0/16187.111.0.1 to 187.111.255.254187.111.255.25565,534
113187.112.0.0/16187.112.0.1 to 187.112.255.254187.112.255.25565,534
114187.113.0.0/16187.113.0.1 to 187.113.255.254187.113.255.25565,534
115187.114.0.0/16187.114.0.1 to 187.114.255.254187.114.255.25565,534
116187.115.0.0/16187.115.0.1 to 187.115.255.254187.115.255.25565,534
117187.116.0.0/16187.116.0.1 to 187.116.255.254187.116.255.25565,534
118187.117.0.0/16187.117.0.1 to 187.117.255.254187.117.255.25565,534
119187.118.0.0/16187.118.0.1 to 187.118.255.254187.118.255.25565,534
120187.119.0.0/16187.119.0.1 to 187.119.255.254187.119.255.25565,534
121187.120.0.0/16187.120.0.1 to 187.120.255.254187.120.255.25565,534
122187.121.0.0/16187.121.0.1 to 187.121.255.254187.121.255.25565,534
123187.122.0.0/16187.122.0.1 to 187.122.255.254187.122.255.25565,534
124187.123.0.0/16187.123.0.1 to 187.123.255.254187.123.255.25565,534
125187.124.0.0/16187.124.0.1 to 187.124.255.254187.124.255.25565,534
126187.125.0.0/16187.125.0.1 to 187.125.255.254187.125.255.25565,534
127187.126.0.0/16187.126.0.1 to 187.126.255.254187.126.255.25565,534
128187.127.0.0/16187.127.0.1 to 187.127.255.254187.127.255.25565,534
129187.128.0.0/16187.128.0.1 to 187.128.255.254187.128.255.25565,534
130187.129.0.0/16187.129.0.1 to 187.129.255.254187.129.255.25565,534
131187.130.0.0/16187.130.0.1 to 187.130.255.254187.130.255.25565,534
132187.131.0.0/16187.131.0.1 to 187.131.255.254187.131.255.25565,534
133187.132.0.0/16187.132.0.1 to 187.132.255.254187.132.255.25565,534
134187.133.0.0/16187.133.0.1 to 187.133.255.254187.133.255.25565,534
135187.134.0.0/16187.134.0.1 to 187.134.255.254187.134.255.25565,534
136187.135.0.0/16187.135.0.1 to 187.135.255.254187.135.255.25565,534
137187.136.0.0/16187.136.0.1 to 187.136.255.254187.136.255.25565,534
138187.137.0.0/16187.137.0.1 to 187.137.255.254187.137.255.25565,534
139187.138.0.0/16187.138.0.1 to 187.138.255.254187.138.255.25565,534
140187.139.0.0/16187.139.0.1 to 187.139.255.254187.139.255.25565,534
141187.140.0.0/16187.140.0.1 to 187.140.255.254187.140.255.25565,534
142187.141.0.0/16187.141.0.1 to 187.141.255.254187.141.255.25565,534
143187.142.0.0/16187.142.0.1 to 187.142.255.254187.142.255.25565,534
144187.143.0.0/16187.143.0.1 to 187.143.255.254187.143.255.25565,534
145187.144.0.0/16187.144.0.1 to 187.144.255.254187.144.255.25565,534
146187.145.0.0/16187.145.0.1 to 187.145.255.254187.145.255.25565,534
147187.146.0.0/16187.146.0.1 to 187.146.255.254187.146.255.25565,534
148187.147.0.0/16187.147.0.1 to 187.147.255.254187.147.255.25565,534
149187.148.0.0/16187.148.0.1 to 187.148.255.254187.148.255.25565,534
150187.149.0.0/16187.149.0.1 to 187.149.255.254187.149.255.25565,534
151187.150.0.0/16187.150.0.1 to 187.150.255.254187.150.255.25565,534
152187.151.0.0/16187.151.0.1 to 187.151.255.254187.151.255.25565,534
153187.152.0.0/16187.152.0.1 to 187.152.255.254187.152.255.25565,534
154187.153.0.0/16187.153.0.1 to 187.153.255.254187.153.255.25565,534
155187.154.0.0/16187.154.0.1 to 187.154.255.254187.154.255.25565,534
156187.155.0.0/16187.155.0.1 to 187.155.255.254187.155.255.25565,534
157187.156.0.0/16187.156.0.1 to 187.156.255.254187.156.255.25565,534
158187.157.0.0/16187.157.0.1 to 187.157.255.254187.157.255.25565,534
159187.158.0.0/16187.158.0.1 to 187.158.255.254187.158.255.25565,534
160187.159.0.0/16187.159.0.1 to 187.159.255.254187.159.255.25565,534
161187.160.0.0/16187.160.0.1 to 187.160.255.254187.160.255.25565,534
162187.161.0.0/16187.161.0.1 to 187.161.255.254187.161.255.25565,534
163187.162.0.0/16187.162.0.1 to 187.162.255.254187.162.255.25565,534
164187.163.0.0/16187.163.0.1 to 187.163.255.254187.163.255.25565,534
165187.164.0.0/16187.164.0.1 to 187.164.255.254187.164.255.25565,534
166187.165.0.0/16187.165.0.1 to 187.165.255.254187.165.255.25565,534
167187.166.0.0/16187.166.0.1 to 187.166.255.254187.166.255.25565,534
168187.167.0.0/16187.167.0.1 to 187.167.255.254187.167.255.25565,534
169187.168.0.0/16187.168.0.1 to 187.168.255.254187.168.255.25565,534
170187.169.0.0/16187.169.0.1 to 187.169.255.254187.169.255.25565,534
171187.170.0.0/16187.170.0.1 to 187.170.255.254187.170.255.25565,534
172187.171.0.0/16187.171.0.1 to 187.171.255.254187.171.255.25565,534
173187.172.0.0/16187.172.0.1 to 187.172.255.254187.172.255.25565,534
174187.173.0.0/16187.173.0.1 to 187.173.255.254187.173.255.25565,534
175187.174.0.0/16187.174.0.1 to 187.174.255.254187.174.255.25565,534
176187.175.0.0/16187.175.0.1 to 187.175.255.254187.175.255.25565,534
177187.176.0.0/16187.176.0.1 to 187.176.255.254187.176.255.25565,534
178187.177.0.0/16187.177.0.1 to 187.177.255.254187.177.255.25565,534
179187.178.0.0/16187.178.0.1 to 187.178.255.254187.178.255.25565,534
180187.179.0.0/16187.179.0.1 to 187.179.255.254187.179.255.25565,534
181187.180.0.0/16187.180.0.1 to 187.180.255.254187.180.255.25565,534
182187.181.0.0/16187.181.0.1 to 187.181.255.254187.181.255.25565,534
183187.182.0.0/16187.182.0.1 to 187.182.255.254187.182.255.25565,534
184187.183.0.0/16187.183.0.1 to 187.183.255.254187.183.255.25565,534
185187.184.0.0/16187.184.0.1 to 187.184.255.254187.184.255.25565,534
186187.185.0.0/16187.185.0.1 to 187.185.255.254187.185.255.25565,534
187187.186.0.0/16187.186.0.1 to 187.186.255.254187.186.255.25565,534
188187.187.0.0/16187.187.0.1 to 187.187.255.254187.187.255.25565,534
189187.188.0.0/16187.188.0.1 to 187.188.255.254187.188.255.25565,534
190187.189.0.0/16187.189.0.1 to 187.189.255.254187.189.255.25565,534
191187.190.0.0/16187.190.0.1 to 187.190.255.254187.190.255.25565,534
192187.191.0.0/16187.191.0.1 to 187.191.255.254187.191.255.25565,534
193187.192.0.0/16187.192.0.1 to 187.192.255.254187.192.255.25565,534
194187.193.0.0/16187.193.0.1 to 187.193.255.254187.193.255.25565,534
195187.194.0.0/16187.194.0.1 to 187.194.255.254187.194.255.25565,534
196187.195.0.0/16187.195.0.1 to 187.195.255.254187.195.255.25565,534
197187.196.0.0/16187.196.0.1 to 187.196.255.254187.196.255.25565,534
198187.197.0.0/16187.197.0.1 to 187.197.255.254187.197.255.25565,534
199187.198.0.0/16187.198.0.1 to 187.198.255.254187.198.255.25565,534
200187.199.0.0/16187.199.0.1 to 187.199.255.254187.199.255.25565,534
201187.200.0.0/16187.200.0.1 to 187.200.255.254187.200.255.25565,534
202187.201.0.0/16187.201.0.1 to 187.201.255.254187.201.255.25565,534
203187.202.0.0/16187.202.0.1 to 187.202.255.254187.202.255.25565,534
204187.203.0.0/16187.203.0.1 to 187.203.255.254187.203.255.25565,534
205187.204.0.0/16187.204.0.1 to 187.204.255.254187.204.255.25565,534
206187.205.0.0/16187.205.0.1 to 187.205.255.254187.205.255.25565,534
207187.206.0.0/16187.206.0.1 to 187.206.255.254187.206.255.25565,534
208187.207.0.0/16187.207.0.1 to 187.207.255.254187.207.255.25565,534
209187.208.0.0/16187.208.0.1 to 187.208.255.254187.208.255.25565,534
210187.209.0.0/16187.209.0.1 to 187.209.255.254187.209.255.25565,534
211187.210.0.0/16187.210.0.1 to 187.210.255.254187.210.255.25565,534
212187.211.0.0/16187.211.0.1 to 187.211.255.254187.211.255.25565,534
213187.212.0.0/16187.212.0.1 to 187.212.255.254187.212.255.25565,534
214187.213.0.0/16187.213.0.1 to 187.213.255.254187.213.255.25565,534
215187.214.0.0/16187.214.0.1 to 187.214.255.254187.214.255.25565,534
216187.215.0.0/16187.215.0.1 to 187.215.255.254187.215.255.25565,534
217187.216.0.0/16187.216.0.1 to 187.216.255.254187.216.255.25565,534
218187.217.0.0/16187.217.0.1 to 187.217.255.254187.217.255.25565,534
219187.218.0.0/16187.218.0.1 to 187.218.255.254187.218.255.25565,534
220187.219.0.0/16187.219.0.1 to 187.219.255.254187.219.255.25565,534
221187.220.0.0/16187.220.0.1 to 187.220.255.254187.220.255.25565,534
222187.221.0.0/16187.221.0.1 to 187.221.255.254187.221.255.25565,534
223187.222.0.0/16187.222.0.1 to 187.222.255.254187.222.255.25565,534
224187.223.0.0/16187.223.0.1 to 187.223.255.254187.223.255.25565,534
225187.224.0.0/16187.224.0.1 to 187.224.255.254187.224.255.25565,534
226187.225.0.0/16187.225.0.1 to 187.225.255.254187.225.255.25565,534
227187.226.0.0/16187.226.0.1 to 187.226.255.254187.226.255.25565,534
228187.227.0.0/16187.227.0.1 to 187.227.255.254187.227.255.25565,534
229187.228.0.0/16187.228.0.1 to 187.228.255.254187.228.255.25565,534
230187.229.0.0/16187.229.0.1 to 187.229.255.254187.229.255.25565,534
231187.230.0.0/16187.230.0.1 to 187.230.255.254187.230.255.25565,534
232187.231.0.0/16187.231.0.1 to 187.231.255.254187.231.255.25565,534
233187.232.0.0/16187.232.0.1 to 187.232.255.254187.232.255.25565,534
234187.233.0.0/16187.233.0.1 to 187.233.255.254187.233.255.25565,534
235187.234.0.0/16187.234.0.1 to 187.234.255.254187.234.255.25565,534
236187.235.0.0/16187.235.0.1 to 187.235.255.254187.235.255.25565,534
237187.236.0.0/16187.236.0.1 to 187.236.255.254187.236.255.25565,534
238187.237.0.0/16187.237.0.1 to 187.237.255.254187.237.255.25565,534
239187.238.0.0/16187.238.0.1 to 187.238.255.254187.238.255.25565,534
240187.239.0.0/16187.239.0.1 to 187.239.255.254187.239.255.25565,534
241187.240.0.0/16187.240.0.1 to 187.240.255.254187.240.255.25565,534
242187.241.0.0/16187.241.0.1 to 187.241.255.254187.241.255.25565,534
243187.242.0.0/16187.242.0.1 to 187.242.255.254187.242.255.25565,534
244187.243.0.0/16187.243.0.1 to 187.243.255.254187.243.255.25565,534
245187.244.0.0/16187.244.0.1 to 187.244.255.254187.244.255.25565,534
246187.245.0.0/16187.245.0.1 to 187.245.255.254187.245.255.25565,534
247187.246.0.0/16187.246.0.1 to 187.246.255.254187.246.255.25565,534
248187.247.0.0/16187.247.0.1 to 187.247.255.254187.247.255.25565,534
249187.248.0.0/16187.248.0.1 to 187.248.255.254187.248.255.25565,534
250187.249.0.0/16187.249.0.1 to 187.249.255.254187.249.255.25565,534
251187.250.0.0/16187.250.0.1 to 187.250.255.254187.250.255.25565,534
252187.251.0.0/16187.251.0.1 to 187.251.255.254187.251.255.25565,534
253187.252.0.0/16187.252.0.1 to 187.252.255.254187.252.255.25565,534
254187.253.0.0/16187.253.0.1 to 187.253.255.254187.253.255.25565,534
255187.254.0.0/16187.254.0.1 to 187.254.255.254187.254.255.25565,534
256187.255.0.0/16187.255.0.1 to 187.255.255.254187.255.255.25565,534

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.