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.

Network187.2.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
187.2.0.0
Broadcast address
187.3.255.255
First usable
187.2.0.1
Last usable
187.3.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
B (default /16)
As numbers
Hex BB020000 · Integer 3137470464 to 3137601535
Reverse DNS zones
2.187.in-addr.arpa
3.187.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10111011.00000010.00000000.00000000187.2.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network10111011.00000010.00000000.00000000187.2.0.0
Broadcast10111011.00000011.11111111.11111111187.3.255.255
Split into smaller subnets/23
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

187.2.0.0/15 makes 256 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1187.2.0.0/23187.2.0.1 to 187.2.1.254187.2.1.255510
2187.2.2.0/23187.2.2.1 to 187.2.3.254187.2.3.255510
3187.2.4.0/23187.2.4.1 to 187.2.5.254187.2.5.255510
4187.2.6.0/23187.2.6.1 to 187.2.7.254187.2.7.255510
5187.2.8.0/23187.2.8.1 to 187.2.9.254187.2.9.255510
6187.2.10.0/23187.2.10.1 to 187.2.11.254187.2.11.255510
7187.2.12.0/23187.2.12.1 to 187.2.13.254187.2.13.255510
8187.2.14.0/23187.2.14.1 to 187.2.15.254187.2.15.255510
9187.2.16.0/23187.2.16.1 to 187.2.17.254187.2.17.255510
10187.2.18.0/23187.2.18.1 to 187.2.19.254187.2.19.255510
11187.2.20.0/23187.2.20.1 to 187.2.21.254187.2.21.255510
12187.2.22.0/23187.2.22.1 to 187.2.23.254187.2.23.255510
13187.2.24.0/23187.2.24.1 to 187.2.25.254187.2.25.255510
14187.2.26.0/23187.2.26.1 to 187.2.27.254187.2.27.255510
15187.2.28.0/23187.2.28.1 to 187.2.29.254187.2.29.255510
16187.2.30.0/23187.2.30.1 to 187.2.31.254187.2.31.255510
17187.2.32.0/23187.2.32.1 to 187.2.33.254187.2.33.255510
18187.2.34.0/23187.2.34.1 to 187.2.35.254187.2.35.255510
19187.2.36.0/23187.2.36.1 to 187.2.37.254187.2.37.255510
20187.2.38.0/23187.2.38.1 to 187.2.39.254187.2.39.255510
21187.2.40.0/23187.2.40.1 to 187.2.41.254187.2.41.255510
22187.2.42.0/23187.2.42.1 to 187.2.43.254187.2.43.255510
23187.2.44.0/23187.2.44.1 to 187.2.45.254187.2.45.255510
24187.2.46.0/23187.2.46.1 to 187.2.47.254187.2.47.255510
25187.2.48.0/23187.2.48.1 to 187.2.49.254187.2.49.255510
26187.2.50.0/23187.2.50.1 to 187.2.51.254187.2.51.255510
27187.2.52.0/23187.2.52.1 to 187.2.53.254187.2.53.255510
28187.2.54.0/23187.2.54.1 to 187.2.55.254187.2.55.255510
29187.2.56.0/23187.2.56.1 to 187.2.57.254187.2.57.255510
30187.2.58.0/23187.2.58.1 to 187.2.59.254187.2.59.255510
31187.2.60.0/23187.2.60.1 to 187.2.61.254187.2.61.255510
32187.2.62.0/23187.2.62.1 to 187.2.63.254187.2.63.255510
33187.2.64.0/23187.2.64.1 to 187.2.65.254187.2.65.255510
34187.2.66.0/23187.2.66.1 to 187.2.67.254187.2.67.255510
35187.2.68.0/23187.2.68.1 to 187.2.69.254187.2.69.255510
36187.2.70.0/23187.2.70.1 to 187.2.71.254187.2.71.255510
37187.2.72.0/23187.2.72.1 to 187.2.73.254187.2.73.255510
38187.2.74.0/23187.2.74.1 to 187.2.75.254187.2.75.255510
39187.2.76.0/23187.2.76.1 to 187.2.77.254187.2.77.255510
40187.2.78.0/23187.2.78.1 to 187.2.79.254187.2.79.255510
41187.2.80.0/23187.2.80.1 to 187.2.81.254187.2.81.255510
42187.2.82.0/23187.2.82.1 to 187.2.83.254187.2.83.255510
43187.2.84.0/23187.2.84.1 to 187.2.85.254187.2.85.255510
44187.2.86.0/23187.2.86.1 to 187.2.87.254187.2.87.255510
45187.2.88.0/23187.2.88.1 to 187.2.89.254187.2.89.255510
46187.2.90.0/23187.2.90.1 to 187.2.91.254187.2.91.255510
47187.2.92.0/23187.2.92.1 to 187.2.93.254187.2.93.255510
48187.2.94.0/23187.2.94.1 to 187.2.95.254187.2.95.255510
49187.2.96.0/23187.2.96.1 to 187.2.97.254187.2.97.255510
50187.2.98.0/23187.2.98.1 to 187.2.99.254187.2.99.255510
51187.2.100.0/23187.2.100.1 to 187.2.101.254187.2.101.255510
52187.2.102.0/23187.2.102.1 to 187.2.103.254187.2.103.255510
53187.2.104.0/23187.2.104.1 to 187.2.105.254187.2.105.255510
54187.2.106.0/23187.2.106.1 to 187.2.107.254187.2.107.255510
55187.2.108.0/23187.2.108.1 to 187.2.109.254187.2.109.255510
56187.2.110.0/23187.2.110.1 to 187.2.111.254187.2.111.255510
57187.2.112.0/23187.2.112.1 to 187.2.113.254187.2.113.255510
58187.2.114.0/23187.2.114.1 to 187.2.115.254187.2.115.255510
59187.2.116.0/23187.2.116.1 to 187.2.117.254187.2.117.255510
60187.2.118.0/23187.2.118.1 to 187.2.119.254187.2.119.255510
61187.2.120.0/23187.2.120.1 to 187.2.121.254187.2.121.255510
62187.2.122.0/23187.2.122.1 to 187.2.123.254187.2.123.255510
63187.2.124.0/23187.2.124.1 to 187.2.125.254187.2.125.255510
64187.2.126.0/23187.2.126.1 to 187.2.127.254187.2.127.255510
65187.2.128.0/23187.2.128.1 to 187.2.129.254187.2.129.255510
66187.2.130.0/23187.2.130.1 to 187.2.131.254187.2.131.255510
67187.2.132.0/23187.2.132.1 to 187.2.133.254187.2.133.255510
68187.2.134.0/23187.2.134.1 to 187.2.135.254187.2.135.255510
69187.2.136.0/23187.2.136.1 to 187.2.137.254187.2.137.255510
70187.2.138.0/23187.2.138.1 to 187.2.139.254187.2.139.255510
71187.2.140.0/23187.2.140.1 to 187.2.141.254187.2.141.255510
72187.2.142.0/23187.2.142.1 to 187.2.143.254187.2.143.255510
73187.2.144.0/23187.2.144.1 to 187.2.145.254187.2.145.255510
74187.2.146.0/23187.2.146.1 to 187.2.147.254187.2.147.255510
75187.2.148.0/23187.2.148.1 to 187.2.149.254187.2.149.255510
76187.2.150.0/23187.2.150.1 to 187.2.151.254187.2.151.255510
77187.2.152.0/23187.2.152.1 to 187.2.153.254187.2.153.255510
78187.2.154.0/23187.2.154.1 to 187.2.155.254187.2.155.255510
79187.2.156.0/23187.2.156.1 to 187.2.157.254187.2.157.255510
80187.2.158.0/23187.2.158.1 to 187.2.159.254187.2.159.255510
81187.2.160.0/23187.2.160.1 to 187.2.161.254187.2.161.255510
82187.2.162.0/23187.2.162.1 to 187.2.163.254187.2.163.255510
83187.2.164.0/23187.2.164.1 to 187.2.165.254187.2.165.255510
84187.2.166.0/23187.2.166.1 to 187.2.167.254187.2.167.255510
85187.2.168.0/23187.2.168.1 to 187.2.169.254187.2.169.255510
86187.2.170.0/23187.2.170.1 to 187.2.171.254187.2.171.255510
87187.2.172.0/23187.2.172.1 to 187.2.173.254187.2.173.255510
88187.2.174.0/23187.2.174.1 to 187.2.175.254187.2.175.255510
89187.2.176.0/23187.2.176.1 to 187.2.177.254187.2.177.255510
90187.2.178.0/23187.2.178.1 to 187.2.179.254187.2.179.255510
91187.2.180.0/23187.2.180.1 to 187.2.181.254187.2.181.255510
92187.2.182.0/23187.2.182.1 to 187.2.183.254187.2.183.255510
93187.2.184.0/23187.2.184.1 to 187.2.185.254187.2.185.255510
94187.2.186.0/23187.2.186.1 to 187.2.187.254187.2.187.255510
95187.2.188.0/23187.2.188.1 to 187.2.189.254187.2.189.255510
96187.2.190.0/23187.2.190.1 to 187.2.191.254187.2.191.255510
97187.2.192.0/23187.2.192.1 to 187.2.193.254187.2.193.255510
98187.2.194.0/23187.2.194.1 to 187.2.195.254187.2.195.255510
99187.2.196.0/23187.2.196.1 to 187.2.197.254187.2.197.255510
100187.2.198.0/23187.2.198.1 to 187.2.199.254187.2.199.255510
101187.2.200.0/23187.2.200.1 to 187.2.201.254187.2.201.255510
102187.2.202.0/23187.2.202.1 to 187.2.203.254187.2.203.255510
103187.2.204.0/23187.2.204.1 to 187.2.205.254187.2.205.255510
104187.2.206.0/23187.2.206.1 to 187.2.207.254187.2.207.255510
105187.2.208.0/23187.2.208.1 to 187.2.209.254187.2.209.255510
106187.2.210.0/23187.2.210.1 to 187.2.211.254187.2.211.255510
107187.2.212.0/23187.2.212.1 to 187.2.213.254187.2.213.255510
108187.2.214.0/23187.2.214.1 to 187.2.215.254187.2.215.255510
109187.2.216.0/23187.2.216.1 to 187.2.217.254187.2.217.255510
110187.2.218.0/23187.2.218.1 to 187.2.219.254187.2.219.255510
111187.2.220.0/23187.2.220.1 to 187.2.221.254187.2.221.255510
112187.2.222.0/23187.2.222.1 to 187.2.223.254187.2.223.255510
113187.2.224.0/23187.2.224.1 to 187.2.225.254187.2.225.255510
114187.2.226.0/23187.2.226.1 to 187.2.227.254187.2.227.255510
115187.2.228.0/23187.2.228.1 to 187.2.229.254187.2.229.255510
116187.2.230.0/23187.2.230.1 to 187.2.231.254187.2.231.255510
117187.2.232.0/23187.2.232.1 to 187.2.233.254187.2.233.255510
118187.2.234.0/23187.2.234.1 to 187.2.235.254187.2.235.255510
119187.2.236.0/23187.2.236.1 to 187.2.237.254187.2.237.255510
120187.2.238.0/23187.2.238.1 to 187.2.239.254187.2.239.255510
121187.2.240.0/23187.2.240.1 to 187.2.241.254187.2.241.255510
122187.2.242.0/23187.2.242.1 to 187.2.243.254187.2.243.255510
123187.2.244.0/23187.2.244.1 to 187.2.245.254187.2.245.255510
124187.2.246.0/23187.2.246.1 to 187.2.247.254187.2.247.255510
125187.2.248.0/23187.2.248.1 to 187.2.249.254187.2.249.255510
126187.2.250.0/23187.2.250.1 to 187.2.251.254187.2.251.255510
127187.2.252.0/23187.2.252.1 to 187.2.253.254187.2.253.255510
128187.2.254.0/23187.2.254.1 to 187.2.255.254187.2.255.255510
129187.3.0.0/23187.3.0.1 to 187.3.1.254187.3.1.255510
130187.3.2.0/23187.3.2.1 to 187.3.3.254187.3.3.255510
131187.3.4.0/23187.3.4.1 to 187.3.5.254187.3.5.255510
132187.3.6.0/23187.3.6.1 to 187.3.7.254187.3.7.255510
133187.3.8.0/23187.3.8.1 to 187.3.9.254187.3.9.255510
134187.3.10.0/23187.3.10.1 to 187.3.11.254187.3.11.255510
135187.3.12.0/23187.3.12.1 to 187.3.13.254187.3.13.255510
136187.3.14.0/23187.3.14.1 to 187.3.15.254187.3.15.255510
137187.3.16.0/23187.3.16.1 to 187.3.17.254187.3.17.255510
138187.3.18.0/23187.3.18.1 to 187.3.19.254187.3.19.255510
139187.3.20.0/23187.3.20.1 to 187.3.21.254187.3.21.255510
140187.3.22.0/23187.3.22.1 to 187.3.23.254187.3.23.255510
141187.3.24.0/23187.3.24.1 to 187.3.25.254187.3.25.255510
142187.3.26.0/23187.3.26.1 to 187.3.27.254187.3.27.255510
143187.3.28.0/23187.3.28.1 to 187.3.29.254187.3.29.255510
144187.3.30.0/23187.3.30.1 to 187.3.31.254187.3.31.255510
145187.3.32.0/23187.3.32.1 to 187.3.33.254187.3.33.255510
146187.3.34.0/23187.3.34.1 to 187.3.35.254187.3.35.255510
147187.3.36.0/23187.3.36.1 to 187.3.37.254187.3.37.255510
148187.3.38.0/23187.3.38.1 to 187.3.39.254187.3.39.255510
149187.3.40.0/23187.3.40.1 to 187.3.41.254187.3.41.255510
150187.3.42.0/23187.3.42.1 to 187.3.43.254187.3.43.255510
151187.3.44.0/23187.3.44.1 to 187.3.45.254187.3.45.255510
152187.3.46.0/23187.3.46.1 to 187.3.47.254187.3.47.255510
153187.3.48.0/23187.3.48.1 to 187.3.49.254187.3.49.255510
154187.3.50.0/23187.3.50.1 to 187.3.51.254187.3.51.255510
155187.3.52.0/23187.3.52.1 to 187.3.53.254187.3.53.255510
156187.3.54.0/23187.3.54.1 to 187.3.55.254187.3.55.255510
157187.3.56.0/23187.3.56.1 to 187.3.57.254187.3.57.255510
158187.3.58.0/23187.3.58.1 to 187.3.59.254187.3.59.255510
159187.3.60.0/23187.3.60.1 to 187.3.61.254187.3.61.255510
160187.3.62.0/23187.3.62.1 to 187.3.63.254187.3.63.255510
161187.3.64.0/23187.3.64.1 to 187.3.65.254187.3.65.255510
162187.3.66.0/23187.3.66.1 to 187.3.67.254187.3.67.255510
163187.3.68.0/23187.3.68.1 to 187.3.69.254187.3.69.255510
164187.3.70.0/23187.3.70.1 to 187.3.71.254187.3.71.255510
165187.3.72.0/23187.3.72.1 to 187.3.73.254187.3.73.255510
166187.3.74.0/23187.3.74.1 to 187.3.75.254187.3.75.255510
167187.3.76.0/23187.3.76.1 to 187.3.77.254187.3.77.255510
168187.3.78.0/23187.3.78.1 to 187.3.79.254187.3.79.255510
169187.3.80.0/23187.3.80.1 to 187.3.81.254187.3.81.255510
170187.3.82.0/23187.3.82.1 to 187.3.83.254187.3.83.255510
171187.3.84.0/23187.3.84.1 to 187.3.85.254187.3.85.255510
172187.3.86.0/23187.3.86.1 to 187.3.87.254187.3.87.255510
173187.3.88.0/23187.3.88.1 to 187.3.89.254187.3.89.255510
174187.3.90.0/23187.3.90.1 to 187.3.91.254187.3.91.255510
175187.3.92.0/23187.3.92.1 to 187.3.93.254187.3.93.255510
176187.3.94.0/23187.3.94.1 to 187.3.95.254187.3.95.255510
177187.3.96.0/23187.3.96.1 to 187.3.97.254187.3.97.255510
178187.3.98.0/23187.3.98.1 to 187.3.99.254187.3.99.255510
179187.3.100.0/23187.3.100.1 to 187.3.101.254187.3.101.255510
180187.3.102.0/23187.3.102.1 to 187.3.103.254187.3.103.255510
181187.3.104.0/23187.3.104.1 to 187.3.105.254187.3.105.255510
182187.3.106.0/23187.3.106.1 to 187.3.107.254187.3.107.255510
183187.3.108.0/23187.3.108.1 to 187.3.109.254187.3.109.255510
184187.3.110.0/23187.3.110.1 to 187.3.111.254187.3.111.255510
185187.3.112.0/23187.3.112.1 to 187.3.113.254187.3.113.255510
186187.3.114.0/23187.3.114.1 to 187.3.115.254187.3.115.255510
187187.3.116.0/23187.3.116.1 to 187.3.117.254187.3.117.255510
188187.3.118.0/23187.3.118.1 to 187.3.119.254187.3.119.255510
189187.3.120.0/23187.3.120.1 to 187.3.121.254187.3.121.255510
190187.3.122.0/23187.3.122.1 to 187.3.123.254187.3.123.255510
191187.3.124.0/23187.3.124.1 to 187.3.125.254187.3.125.255510
192187.3.126.0/23187.3.126.1 to 187.3.127.254187.3.127.255510
193187.3.128.0/23187.3.128.1 to 187.3.129.254187.3.129.255510
194187.3.130.0/23187.3.130.1 to 187.3.131.254187.3.131.255510
195187.3.132.0/23187.3.132.1 to 187.3.133.254187.3.133.255510
196187.3.134.0/23187.3.134.1 to 187.3.135.254187.3.135.255510
197187.3.136.0/23187.3.136.1 to 187.3.137.254187.3.137.255510
198187.3.138.0/23187.3.138.1 to 187.3.139.254187.3.139.255510
199187.3.140.0/23187.3.140.1 to 187.3.141.254187.3.141.255510
200187.3.142.0/23187.3.142.1 to 187.3.143.254187.3.143.255510
201187.3.144.0/23187.3.144.1 to 187.3.145.254187.3.145.255510
202187.3.146.0/23187.3.146.1 to 187.3.147.254187.3.147.255510
203187.3.148.0/23187.3.148.1 to 187.3.149.254187.3.149.255510
204187.3.150.0/23187.3.150.1 to 187.3.151.254187.3.151.255510
205187.3.152.0/23187.3.152.1 to 187.3.153.254187.3.153.255510
206187.3.154.0/23187.3.154.1 to 187.3.155.254187.3.155.255510
207187.3.156.0/23187.3.156.1 to 187.3.157.254187.3.157.255510
208187.3.158.0/23187.3.158.1 to 187.3.159.254187.3.159.255510
209187.3.160.0/23187.3.160.1 to 187.3.161.254187.3.161.255510
210187.3.162.0/23187.3.162.1 to 187.3.163.254187.3.163.255510
211187.3.164.0/23187.3.164.1 to 187.3.165.254187.3.165.255510
212187.3.166.0/23187.3.166.1 to 187.3.167.254187.3.167.255510
213187.3.168.0/23187.3.168.1 to 187.3.169.254187.3.169.255510
214187.3.170.0/23187.3.170.1 to 187.3.171.254187.3.171.255510
215187.3.172.0/23187.3.172.1 to 187.3.173.254187.3.173.255510
216187.3.174.0/23187.3.174.1 to 187.3.175.254187.3.175.255510
217187.3.176.0/23187.3.176.1 to 187.3.177.254187.3.177.255510
218187.3.178.0/23187.3.178.1 to 187.3.179.254187.3.179.255510
219187.3.180.0/23187.3.180.1 to 187.3.181.254187.3.181.255510
220187.3.182.0/23187.3.182.1 to 187.3.183.254187.3.183.255510
221187.3.184.0/23187.3.184.1 to 187.3.185.254187.3.185.255510
222187.3.186.0/23187.3.186.1 to 187.3.187.254187.3.187.255510
223187.3.188.0/23187.3.188.1 to 187.3.189.254187.3.189.255510
224187.3.190.0/23187.3.190.1 to 187.3.191.254187.3.191.255510
225187.3.192.0/23187.3.192.1 to 187.3.193.254187.3.193.255510
226187.3.194.0/23187.3.194.1 to 187.3.195.254187.3.195.255510
227187.3.196.0/23187.3.196.1 to 187.3.197.254187.3.197.255510
228187.3.198.0/23187.3.198.1 to 187.3.199.254187.3.199.255510
229187.3.200.0/23187.3.200.1 to 187.3.201.254187.3.201.255510
230187.3.202.0/23187.3.202.1 to 187.3.203.254187.3.203.255510
231187.3.204.0/23187.3.204.1 to 187.3.205.254187.3.205.255510
232187.3.206.0/23187.3.206.1 to 187.3.207.254187.3.207.255510
233187.3.208.0/23187.3.208.1 to 187.3.209.254187.3.209.255510
234187.3.210.0/23187.3.210.1 to 187.3.211.254187.3.211.255510
235187.3.212.0/23187.3.212.1 to 187.3.213.254187.3.213.255510
236187.3.214.0/23187.3.214.1 to 187.3.215.254187.3.215.255510
237187.3.216.0/23187.3.216.1 to 187.3.217.254187.3.217.255510
238187.3.218.0/23187.3.218.1 to 187.3.219.254187.3.219.255510
239187.3.220.0/23187.3.220.1 to 187.3.221.254187.3.221.255510
240187.3.222.0/23187.3.222.1 to 187.3.223.254187.3.223.255510
241187.3.224.0/23187.3.224.1 to 187.3.225.254187.3.225.255510
242187.3.226.0/23187.3.226.1 to 187.3.227.254187.3.227.255510
243187.3.228.0/23187.3.228.1 to 187.3.229.254187.3.229.255510
244187.3.230.0/23187.3.230.1 to 187.3.231.254187.3.231.255510
245187.3.232.0/23187.3.232.1 to 187.3.233.254187.3.233.255510
246187.3.234.0/23187.3.234.1 to 187.3.235.254187.3.235.255510
247187.3.236.0/23187.3.236.1 to 187.3.237.254187.3.237.255510
248187.3.238.0/23187.3.238.1 to 187.3.239.254187.3.239.255510
249187.3.240.0/23187.3.240.1 to 187.3.241.254187.3.241.255510
250187.3.242.0/23187.3.242.1 to 187.3.243.254187.3.243.255510
251187.3.244.0/23187.3.244.1 to 187.3.245.254187.3.245.255510
252187.3.246.0/23187.3.246.1 to 187.3.247.254187.3.247.255510
253187.3.248.0/23187.3.248.1 to 187.3.249.254187.3.249.255510
254187.3.250.0/23187.3.250.1 to 187.3.251.254187.3.251.255510
255187.3.252.0/23187.3.252.1 to 187.3.253.254187.3.253.255510
256187.3.254.0/23187.3.254.1 to 187.3.255.254187.3.255.255510

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.