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.

Network230.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
230.0.0.0
Broadcast address
230.255.255.255
First usable
230.0.0.1
Last usable
230.255.255.254
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
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex E6000000 · Integer 3858759680 to 3875536895
Reverse DNS zone
230.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11100110..00000000.00000000.00000000230.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network11100110..00000000.00000000.00000000230.0.0.0
Broadcast11100110..11111111.11111111.11111111230.255.255.255
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)

230.0.0.0/8 makes 256 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1230.0.0.0/16230.0.0.1 to 230.0.255.254230.0.255.25565,534
2230.1.0.0/16230.1.0.1 to 230.1.255.254230.1.255.25565,534
3230.2.0.0/16230.2.0.1 to 230.2.255.254230.2.255.25565,534
4230.3.0.0/16230.3.0.1 to 230.3.255.254230.3.255.25565,534
5230.4.0.0/16230.4.0.1 to 230.4.255.254230.4.255.25565,534
6230.5.0.0/16230.5.0.1 to 230.5.255.254230.5.255.25565,534
7230.6.0.0/16230.6.0.1 to 230.6.255.254230.6.255.25565,534
8230.7.0.0/16230.7.0.1 to 230.7.255.254230.7.255.25565,534
9230.8.0.0/16230.8.0.1 to 230.8.255.254230.8.255.25565,534
10230.9.0.0/16230.9.0.1 to 230.9.255.254230.9.255.25565,534
11230.10.0.0/16230.10.0.1 to 230.10.255.254230.10.255.25565,534
12230.11.0.0/16230.11.0.1 to 230.11.255.254230.11.255.25565,534
13230.12.0.0/16230.12.0.1 to 230.12.255.254230.12.255.25565,534
14230.13.0.0/16230.13.0.1 to 230.13.255.254230.13.255.25565,534
15230.14.0.0/16230.14.0.1 to 230.14.255.254230.14.255.25565,534
16230.15.0.0/16230.15.0.1 to 230.15.255.254230.15.255.25565,534
17230.16.0.0/16230.16.0.1 to 230.16.255.254230.16.255.25565,534
18230.17.0.0/16230.17.0.1 to 230.17.255.254230.17.255.25565,534
19230.18.0.0/16230.18.0.1 to 230.18.255.254230.18.255.25565,534
20230.19.0.0/16230.19.0.1 to 230.19.255.254230.19.255.25565,534
21230.20.0.0/16230.20.0.1 to 230.20.255.254230.20.255.25565,534
22230.21.0.0/16230.21.0.1 to 230.21.255.254230.21.255.25565,534
23230.22.0.0/16230.22.0.1 to 230.22.255.254230.22.255.25565,534
24230.23.0.0/16230.23.0.1 to 230.23.255.254230.23.255.25565,534
25230.24.0.0/16230.24.0.1 to 230.24.255.254230.24.255.25565,534
26230.25.0.0/16230.25.0.1 to 230.25.255.254230.25.255.25565,534
27230.26.0.0/16230.26.0.1 to 230.26.255.254230.26.255.25565,534
28230.27.0.0/16230.27.0.1 to 230.27.255.254230.27.255.25565,534
29230.28.0.0/16230.28.0.1 to 230.28.255.254230.28.255.25565,534
30230.29.0.0/16230.29.0.1 to 230.29.255.254230.29.255.25565,534
31230.30.0.0/16230.30.0.1 to 230.30.255.254230.30.255.25565,534
32230.31.0.0/16230.31.0.1 to 230.31.255.254230.31.255.25565,534
33230.32.0.0/16230.32.0.1 to 230.32.255.254230.32.255.25565,534
34230.33.0.0/16230.33.0.1 to 230.33.255.254230.33.255.25565,534
35230.34.0.0/16230.34.0.1 to 230.34.255.254230.34.255.25565,534
36230.35.0.0/16230.35.0.1 to 230.35.255.254230.35.255.25565,534
37230.36.0.0/16230.36.0.1 to 230.36.255.254230.36.255.25565,534
38230.37.0.0/16230.37.0.1 to 230.37.255.254230.37.255.25565,534
39230.38.0.0/16230.38.0.1 to 230.38.255.254230.38.255.25565,534
40230.39.0.0/16230.39.0.1 to 230.39.255.254230.39.255.25565,534
41230.40.0.0/16230.40.0.1 to 230.40.255.254230.40.255.25565,534
42230.41.0.0/16230.41.0.1 to 230.41.255.254230.41.255.25565,534
43230.42.0.0/16230.42.0.1 to 230.42.255.254230.42.255.25565,534
44230.43.0.0/16230.43.0.1 to 230.43.255.254230.43.255.25565,534
45230.44.0.0/16230.44.0.1 to 230.44.255.254230.44.255.25565,534
46230.45.0.0/16230.45.0.1 to 230.45.255.254230.45.255.25565,534
47230.46.0.0/16230.46.0.1 to 230.46.255.254230.46.255.25565,534
48230.47.0.0/16230.47.0.1 to 230.47.255.254230.47.255.25565,534
49230.48.0.0/16230.48.0.1 to 230.48.255.254230.48.255.25565,534
50230.49.0.0/16230.49.0.1 to 230.49.255.254230.49.255.25565,534
51230.50.0.0/16230.50.0.1 to 230.50.255.254230.50.255.25565,534
52230.51.0.0/16230.51.0.1 to 230.51.255.254230.51.255.25565,534
53230.52.0.0/16230.52.0.1 to 230.52.255.254230.52.255.25565,534
54230.53.0.0/16230.53.0.1 to 230.53.255.254230.53.255.25565,534
55230.54.0.0/16230.54.0.1 to 230.54.255.254230.54.255.25565,534
56230.55.0.0/16230.55.0.1 to 230.55.255.254230.55.255.25565,534
57230.56.0.0/16230.56.0.1 to 230.56.255.254230.56.255.25565,534
58230.57.0.0/16230.57.0.1 to 230.57.255.254230.57.255.25565,534
59230.58.0.0/16230.58.0.1 to 230.58.255.254230.58.255.25565,534
60230.59.0.0/16230.59.0.1 to 230.59.255.254230.59.255.25565,534
61230.60.0.0/16230.60.0.1 to 230.60.255.254230.60.255.25565,534
62230.61.0.0/16230.61.0.1 to 230.61.255.254230.61.255.25565,534
63230.62.0.0/16230.62.0.1 to 230.62.255.254230.62.255.25565,534
64230.63.0.0/16230.63.0.1 to 230.63.255.254230.63.255.25565,534
65230.64.0.0/16230.64.0.1 to 230.64.255.254230.64.255.25565,534
66230.65.0.0/16230.65.0.1 to 230.65.255.254230.65.255.25565,534
67230.66.0.0/16230.66.0.1 to 230.66.255.254230.66.255.25565,534
68230.67.0.0/16230.67.0.1 to 230.67.255.254230.67.255.25565,534
69230.68.0.0/16230.68.0.1 to 230.68.255.254230.68.255.25565,534
70230.69.0.0/16230.69.0.1 to 230.69.255.254230.69.255.25565,534
71230.70.0.0/16230.70.0.1 to 230.70.255.254230.70.255.25565,534
72230.71.0.0/16230.71.0.1 to 230.71.255.254230.71.255.25565,534
73230.72.0.0/16230.72.0.1 to 230.72.255.254230.72.255.25565,534
74230.73.0.0/16230.73.0.1 to 230.73.255.254230.73.255.25565,534
75230.74.0.0/16230.74.0.1 to 230.74.255.254230.74.255.25565,534
76230.75.0.0/16230.75.0.1 to 230.75.255.254230.75.255.25565,534
77230.76.0.0/16230.76.0.1 to 230.76.255.254230.76.255.25565,534
78230.77.0.0/16230.77.0.1 to 230.77.255.254230.77.255.25565,534
79230.78.0.0/16230.78.0.1 to 230.78.255.254230.78.255.25565,534
80230.79.0.0/16230.79.0.1 to 230.79.255.254230.79.255.25565,534
81230.80.0.0/16230.80.0.1 to 230.80.255.254230.80.255.25565,534
82230.81.0.0/16230.81.0.1 to 230.81.255.254230.81.255.25565,534
83230.82.0.0/16230.82.0.1 to 230.82.255.254230.82.255.25565,534
84230.83.0.0/16230.83.0.1 to 230.83.255.254230.83.255.25565,534
85230.84.0.0/16230.84.0.1 to 230.84.255.254230.84.255.25565,534
86230.85.0.0/16230.85.0.1 to 230.85.255.254230.85.255.25565,534
87230.86.0.0/16230.86.0.1 to 230.86.255.254230.86.255.25565,534
88230.87.0.0/16230.87.0.1 to 230.87.255.254230.87.255.25565,534
89230.88.0.0/16230.88.0.1 to 230.88.255.254230.88.255.25565,534
90230.89.0.0/16230.89.0.1 to 230.89.255.254230.89.255.25565,534
91230.90.0.0/16230.90.0.1 to 230.90.255.254230.90.255.25565,534
92230.91.0.0/16230.91.0.1 to 230.91.255.254230.91.255.25565,534
93230.92.0.0/16230.92.0.1 to 230.92.255.254230.92.255.25565,534
94230.93.0.0/16230.93.0.1 to 230.93.255.254230.93.255.25565,534
95230.94.0.0/16230.94.0.1 to 230.94.255.254230.94.255.25565,534
96230.95.0.0/16230.95.0.1 to 230.95.255.254230.95.255.25565,534
97230.96.0.0/16230.96.0.1 to 230.96.255.254230.96.255.25565,534
98230.97.0.0/16230.97.0.1 to 230.97.255.254230.97.255.25565,534
99230.98.0.0/16230.98.0.1 to 230.98.255.254230.98.255.25565,534
100230.99.0.0/16230.99.0.1 to 230.99.255.254230.99.255.25565,534
101230.100.0.0/16230.100.0.1 to 230.100.255.254230.100.255.25565,534
102230.101.0.0/16230.101.0.1 to 230.101.255.254230.101.255.25565,534
103230.102.0.0/16230.102.0.1 to 230.102.255.254230.102.255.25565,534
104230.103.0.0/16230.103.0.1 to 230.103.255.254230.103.255.25565,534
105230.104.0.0/16230.104.0.1 to 230.104.255.254230.104.255.25565,534
106230.105.0.0/16230.105.0.1 to 230.105.255.254230.105.255.25565,534
107230.106.0.0/16230.106.0.1 to 230.106.255.254230.106.255.25565,534
108230.107.0.0/16230.107.0.1 to 230.107.255.254230.107.255.25565,534
109230.108.0.0/16230.108.0.1 to 230.108.255.254230.108.255.25565,534
110230.109.0.0/16230.109.0.1 to 230.109.255.254230.109.255.25565,534
111230.110.0.0/16230.110.0.1 to 230.110.255.254230.110.255.25565,534
112230.111.0.0/16230.111.0.1 to 230.111.255.254230.111.255.25565,534
113230.112.0.0/16230.112.0.1 to 230.112.255.254230.112.255.25565,534
114230.113.0.0/16230.113.0.1 to 230.113.255.254230.113.255.25565,534
115230.114.0.0/16230.114.0.1 to 230.114.255.254230.114.255.25565,534
116230.115.0.0/16230.115.0.1 to 230.115.255.254230.115.255.25565,534
117230.116.0.0/16230.116.0.1 to 230.116.255.254230.116.255.25565,534
118230.117.0.0/16230.117.0.1 to 230.117.255.254230.117.255.25565,534
119230.118.0.0/16230.118.0.1 to 230.118.255.254230.118.255.25565,534
120230.119.0.0/16230.119.0.1 to 230.119.255.254230.119.255.25565,534
121230.120.0.0/16230.120.0.1 to 230.120.255.254230.120.255.25565,534
122230.121.0.0/16230.121.0.1 to 230.121.255.254230.121.255.25565,534
123230.122.0.0/16230.122.0.1 to 230.122.255.254230.122.255.25565,534
124230.123.0.0/16230.123.0.1 to 230.123.255.254230.123.255.25565,534
125230.124.0.0/16230.124.0.1 to 230.124.255.254230.124.255.25565,534
126230.125.0.0/16230.125.0.1 to 230.125.255.254230.125.255.25565,534
127230.126.0.0/16230.126.0.1 to 230.126.255.254230.126.255.25565,534
128230.127.0.0/16230.127.0.1 to 230.127.255.254230.127.255.25565,534
129230.128.0.0/16230.128.0.1 to 230.128.255.254230.128.255.25565,534
130230.129.0.0/16230.129.0.1 to 230.129.255.254230.129.255.25565,534
131230.130.0.0/16230.130.0.1 to 230.130.255.254230.130.255.25565,534
132230.131.0.0/16230.131.0.1 to 230.131.255.254230.131.255.25565,534
133230.132.0.0/16230.132.0.1 to 230.132.255.254230.132.255.25565,534
134230.133.0.0/16230.133.0.1 to 230.133.255.254230.133.255.25565,534
135230.134.0.0/16230.134.0.1 to 230.134.255.254230.134.255.25565,534
136230.135.0.0/16230.135.0.1 to 230.135.255.254230.135.255.25565,534
137230.136.0.0/16230.136.0.1 to 230.136.255.254230.136.255.25565,534
138230.137.0.0/16230.137.0.1 to 230.137.255.254230.137.255.25565,534
139230.138.0.0/16230.138.0.1 to 230.138.255.254230.138.255.25565,534
140230.139.0.0/16230.139.0.1 to 230.139.255.254230.139.255.25565,534
141230.140.0.0/16230.140.0.1 to 230.140.255.254230.140.255.25565,534
142230.141.0.0/16230.141.0.1 to 230.141.255.254230.141.255.25565,534
143230.142.0.0/16230.142.0.1 to 230.142.255.254230.142.255.25565,534
144230.143.0.0/16230.143.0.1 to 230.143.255.254230.143.255.25565,534
145230.144.0.0/16230.144.0.1 to 230.144.255.254230.144.255.25565,534
146230.145.0.0/16230.145.0.1 to 230.145.255.254230.145.255.25565,534
147230.146.0.0/16230.146.0.1 to 230.146.255.254230.146.255.25565,534
148230.147.0.0/16230.147.0.1 to 230.147.255.254230.147.255.25565,534
149230.148.0.0/16230.148.0.1 to 230.148.255.254230.148.255.25565,534
150230.149.0.0/16230.149.0.1 to 230.149.255.254230.149.255.25565,534
151230.150.0.0/16230.150.0.1 to 230.150.255.254230.150.255.25565,534
152230.151.0.0/16230.151.0.1 to 230.151.255.254230.151.255.25565,534
153230.152.0.0/16230.152.0.1 to 230.152.255.254230.152.255.25565,534
154230.153.0.0/16230.153.0.1 to 230.153.255.254230.153.255.25565,534
155230.154.0.0/16230.154.0.1 to 230.154.255.254230.154.255.25565,534
156230.155.0.0/16230.155.0.1 to 230.155.255.254230.155.255.25565,534
157230.156.0.0/16230.156.0.1 to 230.156.255.254230.156.255.25565,534
158230.157.0.0/16230.157.0.1 to 230.157.255.254230.157.255.25565,534
159230.158.0.0/16230.158.0.1 to 230.158.255.254230.158.255.25565,534
160230.159.0.0/16230.159.0.1 to 230.159.255.254230.159.255.25565,534
161230.160.0.0/16230.160.0.1 to 230.160.255.254230.160.255.25565,534
162230.161.0.0/16230.161.0.1 to 230.161.255.254230.161.255.25565,534
163230.162.0.0/16230.162.0.1 to 230.162.255.254230.162.255.25565,534
164230.163.0.0/16230.163.0.1 to 230.163.255.254230.163.255.25565,534
165230.164.0.0/16230.164.0.1 to 230.164.255.254230.164.255.25565,534
166230.165.0.0/16230.165.0.1 to 230.165.255.254230.165.255.25565,534
167230.166.0.0/16230.166.0.1 to 230.166.255.254230.166.255.25565,534
168230.167.0.0/16230.167.0.1 to 230.167.255.254230.167.255.25565,534
169230.168.0.0/16230.168.0.1 to 230.168.255.254230.168.255.25565,534
170230.169.0.0/16230.169.0.1 to 230.169.255.254230.169.255.25565,534
171230.170.0.0/16230.170.0.1 to 230.170.255.254230.170.255.25565,534
172230.171.0.0/16230.171.0.1 to 230.171.255.254230.171.255.25565,534
173230.172.0.0/16230.172.0.1 to 230.172.255.254230.172.255.25565,534
174230.173.0.0/16230.173.0.1 to 230.173.255.254230.173.255.25565,534
175230.174.0.0/16230.174.0.1 to 230.174.255.254230.174.255.25565,534
176230.175.0.0/16230.175.0.1 to 230.175.255.254230.175.255.25565,534
177230.176.0.0/16230.176.0.1 to 230.176.255.254230.176.255.25565,534
178230.177.0.0/16230.177.0.1 to 230.177.255.254230.177.255.25565,534
179230.178.0.0/16230.178.0.1 to 230.178.255.254230.178.255.25565,534
180230.179.0.0/16230.179.0.1 to 230.179.255.254230.179.255.25565,534
181230.180.0.0/16230.180.0.1 to 230.180.255.254230.180.255.25565,534
182230.181.0.0/16230.181.0.1 to 230.181.255.254230.181.255.25565,534
183230.182.0.0/16230.182.0.1 to 230.182.255.254230.182.255.25565,534
184230.183.0.0/16230.183.0.1 to 230.183.255.254230.183.255.25565,534
185230.184.0.0/16230.184.0.1 to 230.184.255.254230.184.255.25565,534
186230.185.0.0/16230.185.0.1 to 230.185.255.254230.185.255.25565,534
187230.186.0.0/16230.186.0.1 to 230.186.255.254230.186.255.25565,534
188230.187.0.0/16230.187.0.1 to 230.187.255.254230.187.255.25565,534
189230.188.0.0/16230.188.0.1 to 230.188.255.254230.188.255.25565,534
190230.189.0.0/16230.189.0.1 to 230.189.255.254230.189.255.25565,534
191230.190.0.0/16230.190.0.1 to 230.190.255.254230.190.255.25565,534
192230.191.0.0/16230.191.0.1 to 230.191.255.254230.191.255.25565,534
193230.192.0.0/16230.192.0.1 to 230.192.255.254230.192.255.25565,534
194230.193.0.0/16230.193.0.1 to 230.193.255.254230.193.255.25565,534
195230.194.0.0/16230.194.0.1 to 230.194.255.254230.194.255.25565,534
196230.195.0.0/16230.195.0.1 to 230.195.255.254230.195.255.25565,534
197230.196.0.0/16230.196.0.1 to 230.196.255.254230.196.255.25565,534
198230.197.0.0/16230.197.0.1 to 230.197.255.254230.197.255.25565,534
199230.198.0.0/16230.198.0.1 to 230.198.255.254230.198.255.25565,534
200230.199.0.0/16230.199.0.1 to 230.199.255.254230.199.255.25565,534
201230.200.0.0/16230.200.0.1 to 230.200.255.254230.200.255.25565,534
202230.201.0.0/16230.201.0.1 to 230.201.255.254230.201.255.25565,534
203230.202.0.0/16230.202.0.1 to 230.202.255.254230.202.255.25565,534
204230.203.0.0/16230.203.0.1 to 230.203.255.254230.203.255.25565,534
205230.204.0.0/16230.204.0.1 to 230.204.255.254230.204.255.25565,534
206230.205.0.0/16230.205.0.1 to 230.205.255.254230.205.255.25565,534
207230.206.0.0/16230.206.0.1 to 230.206.255.254230.206.255.25565,534
208230.207.0.0/16230.207.0.1 to 230.207.255.254230.207.255.25565,534
209230.208.0.0/16230.208.0.1 to 230.208.255.254230.208.255.25565,534
210230.209.0.0/16230.209.0.1 to 230.209.255.254230.209.255.25565,534
211230.210.0.0/16230.210.0.1 to 230.210.255.254230.210.255.25565,534
212230.211.0.0/16230.211.0.1 to 230.211.255.254230.211.255.25565,534
213230.212.0.0/16230.212.0.1 to 230.212.255.254230.212.255.25565,534
214230.213.0.0/16230.213.0.1 to 230.213.255.254230.213.255.25565,534
215230.214.0.0/16230.214.0.1 to 230.214.255.254230.214.255.25565,534
216230.215.0.0/16230.215.0.1 to 230.215.255.254230.215.255.25565,534
217230.216.0.0/16230.216.0.1 to 230.216.255.254230.216.255.25565,534
218230.217.0.0/16230.217.0.1 to 230.217.255.254230.217.255.25565,534
219230.218.0.0/16230.218.0.1 to 230.218.255.254230.218.255.25565,534
220230.219.0.0/16230.219.0.1 to 230.219.255.254230.219.255.25565,534
221230.220.0.0/16230.220.0.1 to 230.220.255.254230.220.255.25565,534
222230.221.0.0/16230.221.0.1 to 230.221.255.254230.221.255.25565,534
223230.222.0.0/16230.222.0.1 to 230.222.255.254230.222.255.25565,534
224230.223.0.0/16230.223.0.1 to 230.223.255.254230.223.255.25565,534
225230.224.0.0/16230.224.0.1 to 230.224.255.254230.224.255.25565,534
226230.225.0.0/16230.225.0.1 to 230.225.255.254230.225.255.25565,534
227230.226.0.0/16230.226.0.1 to 230.226.255.254230.226.255.25565,534
228230.227.0.0/16230.227.0.1 to 230.227.255.254230.227.255.25565,534
229230.228.0.0/16230.228.0.1 to 230.228.255.254230.228.255.25565,534
230230.229.0.0/16230.229.0.1 to 230.229.255.254230.229.255.25565,534
231230.230.0.0/16230.230.0.1 to 230.230.255.254230.230.255.25565,534
232230.231.0.0/16230.231.0.1 to 230.231.255.254230.231.255.25565,534
233230.232.0.0/16230.232.0.1 to 230.232.255.254230.232.255.25565,534
234230.233.0.0/16230.233.0.1 to 230.233.255.254230.233.255.25565,534
235230.234.0.0/16230.234.0.1 to 230.234.255.254230.234.255.25565,534
236230.235.0.0/16230.235.0.1 to 230.235.255.254230.235.255.25565,534
237230.236.0.0/16230.236.0.1 to 230.236.255.254230.236.255.25565,534
238230.237.0.0/16230.237.0.1 to 230.237.255.254230.237.255.25565,534
239230.238.0.0/16230.238.0.1 to 230.238.255.254230.238.255.25565,534
240230.239.0.0/16230.239.0.1 to 230.239.255.254230.239.255.25565,534
241230.240.0.0/16230.240.0.1 to 230.240.255.254230.240.255.25565,534
242230.241.0.0/16230.241.0.1 to 230.241.255.254230.241.255.25565,534
243230.242.0.0/16230.242.0.1 to 230.242.255.254230.242.255.25565,534
244230.243.0.0/16230.243.0.1 to 230.243.255.254230.243.255.25565,534
245230.244.0.0/16230.244.0.1 to 230.244.255.254230.244.255.25565,534
246230.245.0.0/16230.245.0.1 to 230.245.255.254230.245.255.25565,534
247230.246.0.0/16230.246.0.1 to 230.246.255.254230.246.255.25565,534
248230.247.0.0/16230.247.0.1 to 230.247.255.254230.247.255.25565,534
249230.248.0.0/16230.248.0.1 to 230.248.255.254230.248.255.25565,534
250230.249.0.0/16230.249.0.1 to 230.249.255.254230.249.255.25565,534
251230.250.0.0/16230.250.0.1 to 230.250.255.254230.250.255.25565,534
252230.251.0.0/16230.251.0.1 to 230.251.255.254230.251.255.25565,534
253230.252.0.0/16230.252.0.1 to 230.252.255.254230.252.255.25565,534
254230.253.0.0/16230.253.0.1 to 230.253.255.254230.253.255.25565,534
255230.254.0.0/16230.254.0.1 to 230.254.255.254230.254.255.25565,534
256230.255.0.0/16230.255.0.1 to 230.255.255.254230.255.255.25565,534

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.