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.

Network127.186.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
127.186.0.0
Broadcast address
127.187.255.255
First usable
127.186.0.1
Last usable
127.187.255.254
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
Loopback 127.0.0.0/8
This computer
Old class
A (default /8)
As numbers
Hex 7FBA0000 · Integer 2142896128 to 2143027199
Reverse DNS zones
186.127.in-addr.arpa
187.127.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
Address01111111.10111010.00000000.00000000127.186.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network01111111.10111010.00000000.00000000127.186.0.0
Broadcast01111111.10111011.11111111.11111111127.187.255.255
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)

127.186.0.0/15 makes 256 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1127.186.0.0/23127.186.0.1 to 127.186.1.254127.186.1.255510
2127.186.2.0/23127.186.2.1 to 127.186.3.254127.186.3.255510
3127.186.4.0/23127.186.4.1 to 127.186.5.254127.186.5.255510
4127.186.6.0/23127.186.6.1 to 127.186.7.254127.186.7.255510
5127.186.8.0/23127.186.8.1 to 127.186.9.254127.186.9.255510
6127.186.10.0/23127.186.10.1 to 127.186.11.254127.186.11.255510
7127.186.12.0/23127.186.12.1 to 127.186.13.254127.186.13.255510
8127.186.14.0/23127.186.14.1 to 127.186.15.254127.186.15.255510
9127.186.16.0/23127.186.16.1 to 127.186.17.254127.186.17.255510
10127.186.18.0/23127.186.18.1 to 127.186.19.254127.186.19.255510
11127.186.20.0/23127.186.20.1 to 127.186.21.254127.186.21.255510
12127.186.22.0/23127.186.22.1 to 127.186.23.254127.186.23.255510
13127.186.24.0/23127.186.24.1 to 127.186.25.254127.186.25.255510
14127.186.26.0/23127.186.26.1 to 127.186.27.254127.186.27.255510
15127.186.28.0/23127.186.28.1 to 127.186.29.254127.186.29.255510
16127.186.30.0/23127.186.30.1 to 127.186.31.254127.186.31.255510
17127.186.32.0/23127.186.32.1 to 127.186.33.254127.186.33.255510
18127.186.34.0/23127.186.34.1 to 127.186.35.254127.186.35.255510
19127.186.36.0/23127.186.36.1 to 127.186.37.254127.186.37.255510
20127.186.38.0/23127.186.38.1 to 127.186.39.254127.186.39.255510
21127.186.40.0/23127.186.40.1 to 127.186.41.254127.186.41.255510
22127.186.42.0/23127.186.42.1 to 127.186.43.254127.186.43.255510
23127.186.44.0/23127.186.44.1 to 127.186.45.254127.186.45.255510
24127.186.46.0/23127.186.46.1 to 127.186.47.254127.186.47.255510
25127.186.48.0/23127.186.48.1 to 127.186.49.254127.186.49.255510
26127.186.50.0/23127.186.50.1 to 127.186.51.254127.186.51.255510
27127.186.52.0/23127.186.52.1 to 127.186.53.254127.186.53.255510
28127.186.54.0/23127.186.54.1 to 127.186.55.254127.186.55.255510
29127.186.56.0/23127.186.56.1 to 127.186.57.254127.186.57.255510
30127.186.58.0/23127.186.58.1 to 127.186.59.254127.186.59.255510
31127.186.60.0/23127.186.60.1 to 127.186.61.254127.186.61.255510
32127.186.62.0/23127.186.62.1 to 127.186.63.254127.186.63.255510
33127.186.64.0/23127.186.64.1 to 127.186.65.254127.186.65.255510
34127.186.66.0/23127.186.66.1 to 127.186.67.254127.186.67.255510
35127.186.68.0/23127.186.68.1 to 127.186.69.254127.186.69.255510
36127.186.70.0/23127.186.70.1 to 127.186.71.254127.186.71.255510
37127.186.72.0/23127.186.72.1 to 127.186.73.254127.186.73.255510
38127.186.74.0/23127.186.74.1 to 127.186.75.254127.186.75.255510
39127.186.76.0/23127.186.76.1 to 127.186.77.254127.186.77.255510
40127.186.78.0/23127.186.78.1 to 127.186.79.254127.186.79.255510
41127.186.80.0/23127.186.80.1 to 127.186.81.254127.186.81.255510
42127.186.82.0/23127.186.82.1 to 127.186.83.254127.186.83.255510
43127.186.84.0/23127.186.84.1 to 127.186.85.254127.186.85.255510
44127.186.86.0/23127.186.86.1 to 127.186.87.254127.186.87.255510
45127.186.88.0/23127.186.88.1 to 127.186.89.254127.186.89.255510
46127.186.90.0/23127.186.90.1 to 127.186.91.254127.186.91.255510
47127.186.92.0/23127.186.92.1 to 127.186.93.254127.186.93.255510
48127.186.94.0/23127.186.94.1 to 127.186.95.254127.186.95.255510
49127.186.96.0/23127.186.96.1 to 127.186.97.254127.186.97.255510
50127.186.98.0/23127.186.98.1 to 127.186.99.254127.186.99.255510
51127.186.100.0/23127.186.100.1 to 127.186.101.254127.186.101.255510
52127.186.102.0/23127.186.102.1 to 127.186.103.254127.186.103.255510
53127.186.104.0/23127.186.104.1 to 127.186.105.254127.186.105.255510
54127.186.106.0/23127.186.106.1 to 127.186.107.254127.186.107.255510
55127.186.108.0/23127.186.108.1 to 127.186.109.254127.186.109.255510
56127.186.110.0/23127.186.110.1 to 127.186.111.254127.186.111.255510
57127.186.112.0/23127.186.112.1 to 127.186.113.254127.186.113.255510
58127.186.114.0/23127.186.114.1 to 127.186.115.254127.186.115.255510
59127.186.116.0/23127.186.116.1 to 127.186.117.254127.186.117.255510
60127.186.118.0/23127.186.118.1 to 127.186.119.254127.186.119.255510
61127.186.120.0/23127.186.120.1 to 127.186.121.254127.186.121.255510
62127.186.122.0/23127.186.122.1 to 127.186.123.254127.186.123.255510
63127.186.124.0/23127.186.124.1 to 127.186.125.254127.186.125.255510
64127.186.126.0/23127.186.126.1 to 127.186.127.254127.186.127.255510
65127.186.128.0/23127.186.128.1 to 127.186.129.254127.186.129.255510
66127.186.130.0/23127.186.130.1 to 127.186.131.254127.186.131.255510
67127.186.132.0/23127.186.132.1 to 127.186.133.254127.186.133.255510
68127.186.134.0/23127.186.134.1 to 127.186.135.254127.186.135.255510
69127.186.136.0/23127.186.136.1 to 127.186.137.254127.186.137.255510
70127.186.138.0/23127.186.138.1 to 127.186.139.254127.186.139.255510
71127.186.140.0/23127.186.140.1 to 127.186.141.254127.186.141.255510
72127.186.142.0/23127.186.142.1 to 127.186.143.254127.186.143.255510
73127.186.144.0/23127.186.144.1 to 127.186.145.254127.186.145.255510
74127.186.146.0/23127.186.146.1 to 127.186.147.254127.186.147.255510
75127.186.148.0/23127.186.148.1 to 127.186.149.254127.186.149.255510
76127.186.150.0/23127.186.150.1 to 127.186.151.254127.186.151.255510
77127.186.152.0/23127.186.152.1 to 127.186.153.254127.186.153.255510
78127.186.154.0/23127.186.154.1 to 127.186.155.254127.186.155.255510
79127.186.156.0/23127.186.156.1 to 127.186.157.254127.186.157.255510
80127.186.158.0/23127.186.158.1 to 127.186.159.254127.186.159.255510
81127.186.160.0/23127.186.160.1 to 127.186.161.254127.186.161.255510
82127.186.162.0/23127.186.162.1 to 127.186.163.254127.186.163.255510
83127.186.164.0/23127.186.164.1 to 127.186.165.254127.186.165.255510
84127.186.166.0/23127.186.166.1 to 127.186.167.254127.186.167.255510
85127.186.168.0/23127.186.168.1 to 127.186.169.254127.186.169.255510
86127.186.170.0/23127.186.170.1 to 127.186.171.254127.186.171.255510
87127.186.172.0/23127.186.172.1 to 127.186.173.254127.186.173.255510
88127.186.174.0/23127.186.174.1 to 127.186.175.254127.186.175.255510
89127.186.176.0/23127.186.176.1 to 127.186.177.254127.186.177.255510
90127.186.178.0/23127.186.178.1 to 127.186.179.254127.186.179.255510
91127.186.180.0/23127.186.180.1 to 127.186.181.254127.186.181.255510
92127.186.182.0/23127.186.182.1 to 127.186.183.254127.186.183.255510
93127.186.184.0/23127.186.184.1 to 127.186.185.254127.186.185.255510
94127.186.186.0/23127.186.186.1 to 127.186.187.254127.186.187.255510
95127.186.188.0/23127.186.188.1 to 127.186.189.254127.186.189.255510
96127.186.190.0/23127.186.190.1 to 127.186.191.254127.186.191.255510
97127.186.192.0/23127.186.192.1 to 127.186.193.254127.186.193.255510
98127.186.194.0/23127.186.194.1 to 127.186.195.254127.186.195.255510
99127.186.196.0/23127.186.196.1 to 127.186.197.254127.186.197.255510
100127.186.198.0/23127.186.198.1 to 127.186.199.254127.186.199.255510
101127.186.200.0/23127.186.200.1 to 127.186.201.254127.186.201.255510
102127.186.202.0/23127.186.202.1 to 127.186.203.254127.186.203.255510
103127.186.204.0/23127.186.204.1 to 127.186.205.254127.186.205.255510
104127.186.206.0/23127.186.206.1 to 127.186.207.254127.186.207.255510
105127.186.208.0/23127.186.208.1 to 127.186.209.254127.186.209.255510
106127.186.210.0/23127.186.210.1 to 127.186.211.254127.186.211.255510
107127.186.212.0/23127.186.212.1 to 127.186.213.254127.186.213.255510
108127.186.214.0/23127.186.214.1 to 127.186.215.254127.186.215.255510
109127.186.216.0/23127.186.216.1 to 127.186.217.254127.186.217.255510
110127.186.218.0/23127.186.218.1 to 127.186.219.254127.186.219.255510
111127.186.220.0/23127.186.220.1 to 127.186.221.254127.186.221.255510
112127.186.222.0/23127.186.222.1 to 127.186.223.254127.186.223.255510
113127.186.224.0/23127.186.224.1 to 127.186.225.254127.186.225.255510
114127.186.226.0/23127.186.226.1 to 127.186.227.254127.186.227.255510
115127.186.228.0/23127.186.228.1 to 127.186.229.254127.186.229.255510
116127.186.230.0/23127.186.230.1 to 127.186.231.254127.186.231.255510
117127.186.232.0/23127.186.232.1 to 127.186.233.254127.186.233.255510
118127.186.234.0/23127.186.234.1 to 127.186.235.254127.186.235.255510
119127.186.236.0/23127.186.236.1 to 127.186.237.254127.186.237.255510
120127.186.238.0/23127.186.238.1 to 127.186.239.254127.186.239.255510
121127.186.240.0/23127.186.240.1 to 127.186.241.254127.186.241.255510
122127.186.242.0/23127.186.242.1 to 127.186.243.254127.186.243.255510
123127.186.244.0/23127.186.244.1 to 127.186.245.254127.186.245.255510
124127.186.246.0/23127.186.246.1 to 127.186.247.254127.186.247.255510
125127.186.248.0/23127.186.248.1 to 127.186.249.254127.186.249.255510
126127.186.250.0/23127.186.250.1 to 127.186.251.254127.186.251.255510
127127.186.252.0/23127.186.252.1 to 127.186.253.254127.186.253.255510
128127.186.254.0/23127.186.254.1 to 127.186.255.254127.186.255.255510
129127.187.0.0/23127.187.0.1 to 127.187.1.254127.187.1.255510
130127.187.2.0/23127.187.2.1 to 127.187.3.254127.187.3.255510
131127.187.4.0/23127.187.4.1 to 127.187.5.254127.187.5.255510
132127.187.6.0/23127.187.6.1 to 127.187.7.254127.187.7.255510
133127.187.8.0/23127.187.8.1 to 127.187.9.254127.187.9.255510
134127.187.10.0/23127.187.10.1 to 127.187.11.254127.187.11.255510
135127.187.12.0/23127.187.12.1 to 127.187.13.254127.187.13.255510
136127.187.14.0/23127.187.14.1 to 127.187.15.254127.187.15.255510
137127.187.16.0/23127.187.16.1 to 127.187.17.254127.187.17.255510
138127.187.18.0/23127.187.18.1 to 127.187.19.254127.187.19.255510
139127.187.20.0/23127.187.20.1 to 127.187.21.254127.187.21.255510
140127.187.22.0/23127.187.22.1 to 127.187.23.254127.187.23.255510
141127.187.24.0/23127.187.24.1 to 127.187.25.254127.187.25.255510
142127.187.26.0/23127.187.26.1 to 127.187.27.254127.187.27.255510
143127.187.28.0/23127.187.28.1 to 127.187.29.254127.187.29.255510
144127.187.30.0/23127.187.30.1 to 127.187.31.254127.187.31.255510
145127.187.32.0/23127.187.32.1 to 127.187.33.254127.187.33.255510
146127.187.34.0/23127.187.34.1 to 127.187.35.254127.187.35.255510
147127.187.36.0/23127.187.36.1 to 127.187.37.254127.187.37.255510
148127.187.38.0/23127.187.38.1 to 127.187.39.254127.187.39.255510
149127.187.40.0/23127.187.40.1 to 127.187.41.254127.187.41.255510
150127.187.42.0/23127.187.42.1 to 127.187.43.254127.187.43.255510
151127.187.44.0/23127.187.44.1 to 127.187.45.254127.187.45.255510
152127.187.46.0/23127.187.46.1 to 127.187.47.254127.187.47.255510
153127.187.48.0/23127.187.48.1 to 127.187.49.254127.187.49.255510
154127.187.50.0/23127.187.50.1 to 127.187.51.254127.187.51.255510
155127.187.52.0/23127.187.52.1 to 127.187.53.254127.187.53.255510
156127.187.54.0/23127.187.54.1 to 127.187.55.254127.187.55.255510
157127.187.56.0/23127.187.56.1 to 127.187.57.254127.187.57.255510
158127.187.58.0/23127.187.58.1 to 127.187.59.254127.187.59.255510
159127.187.60.0/23127.187.60.1 to 127.187.61.254127.187.61.255510
160127.187.62.0/23127.187.62.1 to 127.187.63.254127.187.63.255510
161127.187.64.0/23127.187.64.1 to 127.187.65.254127.187.65.255510
162127.187.66.0/23127.187.66.1 to 127.187.67.254127.187.67.255510
163127.187.68.0/23127.187.68.1 to 127.187.69.254127.187.69.255510
164127.187.70.0/23127.187.70.1 to 127.187.71.254127.187.71.255510
165127.187.72.0/23127.187.72.1 to 127.187.73.254127.187.73.255510
166127.187.74.0/23127.187.74.1 to 127.187.75.254127.187.75.255510
167127.187.76.0/23127.187.76.1 to 127.187.77.254127.187.77.255510
168127.187.78.0/23127.187.78.1 to 127.187.79.254127.187.79.255510
169127.187.80.0/23127.187.80.1 to 127.187.81.254127.187.81.255510
170127.187.82.0/23127.187.82.1 to 127.187.83.254127.187.83.255510
171127.187.84.0/23127.187.84.1 to 127.187.85.254127.187.85.255510
172127.187.86.0/23127.187.86.1 to 127.187.87.254127.187.87.255510
173127.187.88.0/23127.187.88.1 to 127.187.89.254127.187.89.255510
174127.187.90.0/23127.187.90.1 to 127.187.91.254127.187.91.255510
175127.187.92.0/23127.187.92.1 to 127.187.93.254127.187.93.255510
176127.187.94.0/23127.187.94.1 to 127.187.95.254127.187.95.255510
177127.187.96.0/23127.187.96.1 to 127.187.97.254127.187.97.255510
178127.187.98.0/23127.187.98.1 to 127.187.99.254127.187.99.255510
179127.187.100.0/23127.187.100.1 to 127.187.101.254127.187.101.255510
180127.187.102.0/23127.187.102.1 to 127.187.103.254127.187.103.255510
181127.187.104.0/23127.187.104.1 to 127.187.105.254127.187.105.255510
182127.187.106.0/23127.187.106.1 to 127.187.107.254127.187.107.255510
183127.187.108.0/23127.187.108.1 to 127.187.109.254127.187.109.255510
184127.187.110.0/23127.187.110.1 to 127.187.111.254127.187.111.255510
185127.187.112.0/23127.187.112.1 to 127.187.113.254127.187.113.255510
186127.187.114.0/23127.187.114.1 to 127.187.115.254127.187.115.255510
187127.187.116.0/23127.187.116.1 to 127.187.117.254127.187.117.255510
188127.187.118.0/23127.187.118.1 to 127.187.119.254127.187.119.255510
189127.187.120.0/23127.187.120.1 to 127.187.121.254127.187.121.255510
190127.187.122.0/23127.187.122.1 to 127.187.123.254127.187.123.255510
191127.187.124.0/23127.187.124.1 to 127.187.125.254127.187.125.255510
192127.187.126.0/23127.187.126.1 to 127.187.127.254127.187.127.255510
193127.187.128.0/23127.187.128.1 to 127.187.129.254127.187.129.255510
194127.187.130.0/23127.187.130.1 to 127.187.131.254127.187.131.255510
195127.187.132.0/23127.187.132.1 to 127.187.133.254127.187.133.255510
196127.187.134.0/23127.187.134.1 to 127.187.135.254127.187.135.255510
197127.187.136.0/23127.187.136.1 to 127.187.137.254127.187.137.255510
198127.187.138.0/23127.187.138.1 to 127.187.139.254127.187.139.255510
199127.187.140.0/23127.187.140.1 to 127.187.141.254127.187.141.255510
200127.187.142.0/23127.187.142.1 to 127.187.143.254127.187.143.255510
201127.187.144.0/23127.187.144.1 to 127.187.145.254127.187.145.255510
202127.187.146.0/23127.187.146.1 to 127.187.147.254127.187.147.255510
203127.187.148.0/23127.187.148.1 to 127.187.149.254127.187.149.255510
204127.187.150.0/23127.187.150.1 to 127.187.151.254127.187.151.255510
205127.187.152.0/23127.187.152.1 to 127.187.153.254127.187.153.255510
206127.187.154.0/23127.187.154.1 to 127.187.155.254127.187.155.255510
207127.187.156.0/23127.187.156.1 to 127.187.157.254127.187.157.255510
208127.187.158.0/23127.187.158.1 to 127.187.159.254127.187.159.255510
209127.187.160.0/23127.187.160.1 to 127.187.161.254127.187.161.255510
210127.187.162.0/23127.187.162.1 to 127.187.163.254127.187.163.255510
211127.187.164.0/23127.187.164.1 to 127.187.165.254127.187.165.255510
212127.187.166.0/23127.187.166.1 to 127.187.167.254127.187.167.255510
213127.187.168.0/23127.187.168.1 to 127.187.169.254127.187.169.255510
214127.187.170.0/23127.187.170.1 to 127.187.171.254127.187.171.255510
215127.187.172.0/23127.187.172.1 to 127.187.173.254127.187.173.255510
216127.187.174.0/23127.187.174.1 to 127.187.175.254127.187.175.255510
217127.187.176.0/23127.187.176.1 to 127.187.177.254127.187.177.255510
218127.187.178.0/23127.187.178.1 to 127.187.179.254127.187.179.255510
219127.187.180.0/23127.187.180.1 to 127.187.181.254127.187.181.255510
220127.187.182.0/23127.187.182.1 to 127.187.183.254127.187.183.255510
221127.187.184.0/23127.187.184.1 to 127.187.185.254127.187.185.255510
222127.187.186.0/23127.187.186.1 to 127.187.187.254127.187.187.255510
223127.187.188.0/23127.187.188.1 to 127.187.189.254127.187.189.255510
224127.187.190.0/23127.187.190.1 to 127.187.191.254127.187.191.255510
225127.187.192.0/23127.187.192.1 to 127.187.193.254127.187.193.255510
226127.187.194.0/23127.187.194.1 to 127.187.195.254127.187.195.255510
227127.187.196.0/23127.187.196.1 to 127.187.197.254127.187.197.255510
228127.187.198.0/23127.187.198.1 to 127.187.199.254127.187.199.255510
229127.187.200.0/23127.187.200.1 to 127.187.201.254127.187.201.255510
230127.187.202.0/23127.187.202.1 to 127.187.203.254127.187.203.255510
231127.187.204.0/23127.187.204.1 to 127.187.205.254127.187.205.255510
232127.187.206.0/23127.187.206.1 to 127.187.207.254127.187.207.255510
233127.187.208.0/23127.187.208.1 to 127.187.209.254127.187.209.255510
234127.187.210.0/23127.187.210.1 to 127.187.211.254127.187.211.255510
235127.187.212.0/23127.187.212.1 to 127.187.213.254127.187.213.255510
236127.187.214.0/23127.187.214.1 to 127.187.215.254127.187.215.255510
237127.187.216.0/23127.187.216.1 to 127.187.217.254127.187.217.255510
238127.187.218.0/23127.187.218.1 to 127.187.219.254127.187.219.255510
239127.187.220.0/23127.187.220.1 to 127.187.221.254127.187.221.255510
240127.187.222.0/23127.187.222.1 to 127.187.223.254127.187.223.255510
241127.187.224.0/23127.187.224.1 to 127.187.225.254127.187.225.255510
242127.187.226.0/23127.187.226.1 to 127.187.227.254127.187.227.255510
243127.187.228.0/23127.187.228.1 to 127.187.229.254127.187.229.255510
244127.187.230.0/23127.187.230.1 to 127.187.231.254127.187.231.255510
245127.187.232.0/23127.187.232.1 to 127.187.233.254127.187.233.255510
246127.187.234.0/23127.187.234.1 to 127.187.235.254127.187.235.255510
247127.187.236.0/23127.187.236.1 to 127.187.237.254127.187.237.255510
248127.187.238.0/23127.187.238.1 to 127.187.239.254127.187.239.255510
249127.187.240.0/23127.187.240.1 to 127.187.241.254127.187.241.255510
250127.187.242.0/23127.187.242.1 to 127.187.243.254127.187.243.255510
251127.187.244.0/23127.187.244.1 to 127.187.245.254127.187.245.255510
252127.187.246.0/23127.187.246.1 to 127.187.247.254127.187.247.255510
253127.187.248.0/23127.187.248.1 to 127.187.249.254127.187.249.255510
254127.187.250.0/23127.187.250.1 to 127.187.251.254127.187.251.255510
255127.187.252.0/23127.187.252.1 to 127.187.253.254127.187.253.255510
256127.187.254.0/23127.187.254.1 to 127.187.255.254127.187.255.255510

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.