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.

Network220.0.0.0/6
Usable hosts67,108,862
Subnet mask252.0.0.0
Addresses67,108,864
Network address
220.0.0.0
Broadcast address
223.255.255.255
First usable
220.0.0.1
Last usable
223.255.255.254
Usable hosts
67,108,862 (67,108,864 less the network and broadcast addresses)
Subnet mask
252.0.0.0
Wildcard mask
3.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/6
Type
Public public
Old class
C (default /24)
As numbers
Hex DC000000 · Integer 3690987520 to 3758096383
Reverse DNS zones
220.in-addr.arpa
221.in-addr.arpa
222.in-addr.arpa
223.in-addr.arpa
/6 is not on a 8-bit boundary, so it takes 4 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11011100.00000000.00000000.00000000220.0.0.0
Subnet mask11111100.00000000.00000000.00000000252.0.0.0
Network11011100.00000000.00000000.00000000220.0.0.0
Broadcast11011111.11111111.11111111.11111111223.255.255.255
Split into smaller subnets/16
/7 (2)/8 (4)/9 (8)/10 (16)/11 (32)/12 (64)/13 (128)/14 (256)/15 (512)/16 (1,024)/17 (2,048)/18 (4,096)

220.0.0.0/6 makes 1,024 subnets of /16; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1220.0.0.0/16220.0.0.1 to 220.0.255.254220.0.255.25565,534
2220.1.0.0/16220.1.0.1 to 220.1.255.254220.1.255.25565,534
3220.2.0.0/16220.2.0.1 to 220.2.255.254220.2.255.25565,534
4220.3.0.0/16220.3.0.1 to 220.3.255.254220.3.255.25565,534
5220.4.0.0/16220.4.0.1 to 220.4.255.254220.4.255.25565,534
6220.5.0.0/16220.5.0.1 to 220.5.255.254220.5.255.25565,534
7220.6.0.0/16220.6.0.1 to 220.6.255.254220.6.255.25565,534
8220.7.0.0/16220.7.0.1 to 220.7.255.254220.7.255.25565,534
9220.8.0.0/16220.8.0.1 to 220.8.255.254220.8.255.25565,534
10220.9.0.0/16220.9.0.1 to 220.9.255.254220.9.255.25565,534
11220.10.0.0/16220.10.0.1 to 220.10.255.254220.10.255.25565,534
12220.11.0.0/16220.11.0.1 to 220.11.255.254220.11.255.25565,534
13220.12.0.0/16220.12.0.1 to 220.12.255.254220.12.255.25565,534
14220.13.0.0/16220.13.0.1 to 220.13.255.254220.13.255.25565,534
15220.14.0.0/16220.14.0.1 to 220.14.255.254220.14.255.25565,534
16220.15.0.0/16220.15.0.1 to 220.15.255.254220.15.255.25565,534
17220.16.0.0/16220.16.0.1 to 220.16.255.254220.16.255.25565,534
18220.17.0.0/16220.17.0.1 to 220.17.255.254220.17.255.25565,534
19220.18.0.0/16220.18.0.1 to 220.18.255.254220.18.255.25565,534
20220.19.0.0/16220.19.0.1 to 220.19.255.254220.19.255.25565,534
21220.20.0.0/16220.20.0.1 to 220.20.255.254220.20.255.25565,534
22220.21.0.0/16220.21.0.1 to 220.21.255.254220.21.255.25565,534
23220.22.0.0/16220.22.0.1 to 220.22.255.254220.22.255.25565,534
24220.23.0.0/16220.23.0.1 to 220.23.255.254220.23.255.25565,534
25220.24.0.0/16220.24.0.1 to 220.24.255.254220.24.255.25565,534
26220.25.0.0/16220.25.0.1 to 220.25.255.254220.25.255.25565,534
27220.26.0.0/16220.26.0.1 to 220.26.255.254220.26.255.25565,534
28220.27.0.0/16220.27.0.1 to 220.27.255.254220.27.255.25565,534
29220.28.0.0/16220.28.0.1 to 220.28.255.254220.28.255.25565,534
30220.29.0.0/16220.29.0.1 to 220.29.255.254220.29.255.25565,534
31220.30.0.0/16220.30.0.1 to 220.30.255.254220.30.255.25565,534
32220.31.0.0/16220.31.0.1 to 220.31.255.254220.31.255.25565,534
33220.32.0.0/16220.32.0.1 to 220.32.255.254220.32.255.25565,534
34220.33.0.0/16220.33.0.1 to 220.33.255.254220.33.255.25565,534
35220.34.0.0/16220.34.0.1 to 220.34.255.254220.34.255.25565,534
36220.35.0.0/16220.35.0.1 to 220.35.255.254220.35.255.25565,534
37220.36.0.0/16220.36.0.1 to 220.36.255.254220.36.255.25565,534
38220.37.0.0/16220.37.0.1 to 220.37.255.254220.37.255.25565,534
39220.38.0.0/16220.38.0.1 to 220.38.255.254220.38.255.25565,534
40220.39.0.0/16220.39.0.1 to 220.39.255.254220.39.255.25565,534
41220.40.0.0/16220.40.0.1 to 220.40.255.254220.40.255.25565,534
42220.41.0.0/16220.41.0.1 to 220.41.255.254220.41.255.25565,534
43220.42.0.0/16220.42.0.1 to 220.42.255.254220.42.255.25565,534
44220.43.0.0/16220.43.0.1 to 220.43.255.254220.43.255.25565,534
45220.44.0.0/16220.44.0.1 to 220.44.255.254220.44.255.25565,534
46220.45.0.0/16220.45.0.1 to 220.45.255.254220.45.255.25565,534
47220.46.0.0/16220.46.0.1 to 220.46.255.254220.46.255.25565,534
48220.47.0.0/16220.47.0.1 to 220.47.255.254220.47.255.25565,534
49220.48.0.0/16220.48.0.1 to 220.48.255.254220.48.255.25565,534
50220.49.0.0/16220.49.0.1 to 220.49.255.254220.49.255.25565,534
51220.50.0.0/16220.50.0.1 to 220.50.255.254220.50.255.25565,534
52220.51.0.0/16220.51.0.1 to 220.51.255.254220.51.255.25565,534
53220.52.0.0/16220.52.0.1 to 220.52.255.254220.52.255.25565,534
54220.53.0.0/16220.53.0.1 to 220.53.255.254220.53.255.25565,534
55220.54.0.0/16220.54.0.1 to 220.54.255.254220.54.255.25565,534
56220.55.0.0/16220.55.0.1 to 220.55.255.254220.55.255.25565,534
57220.56.0.0/16220.56.0.1 to 220.56.255.254220.56.255.25565,534
58220.57.0.0/16220.57.0.1 to 220.57.255.254220.57.255.25565,534
59220.58.0.0/16220.58.0.1 to 220.58.255.254220.58.255.25565,534
60220.59.0.0/16220.59.0.1 to 220.59.255.254220.59.255.25565,534
61220.60.0.0/16220.60.0.1 to 220.60.255.254220.60.255.25565,534
62220.61.0.0/16220.61.0.1 to 220.61.255.254220.61.255.25565,534
63220.62.0.0/16220.62.0.1 to 220.62.255.254220.62.255.25565,534
64220.63.0.0/16220.63.0.1 to 220.63.255.254220.63.255.25565,534
65220.64.0.0/16220.64.0.1 to 220.64.255.254220.64.255.25565,534
66220.65.0.0/16220.65.0.1 to 220.65.255.254220.65.255.25565,534
67220.66.0.0/16220.66.0.1 to 220.66.255.254220.66.255.25565,534
68220.67.0.0/16220.67.0.1 to 220.67.255.254220.67.255.25565,534
69220.68.0.0/16220.68.0.1 to 220.68.255.254220.68.255.25565,534
70220.69.0.0/16220.69.0.1 to 220.69.255.254220.69.255.25565,534
71220.70.0.0/16220.70.0.1 to 220.70.255.254220.70.255.25565,534
72220.71.0.0/16220.71.0.1 to 220.71.255.254220.71.255.25565,534
73220.72.0.0/16220.72.0.1 to 220.72.255.254220.72.255.25565,534
74220.73.0.0/16220.73.0.1 to 220.73.255.254220.73.255.25565,534
75220.74.0.0/16220.74.0.1 to 220.74.255.254220.74.255.25565,534
76220.75.0.0/16220.75.0.1 to 220.75.255.254220.75.255.25565,534
77220.76.0.0/16220.76.0.1 to 220.76.255.254220.76.255.25565,534
78220.77.0.0/16220.77.0.1 to 220.77.255.254220.77.255.25565,534
79220.78.0.0/16220.78.0.1 to 220.78.255.254220.78.255.25565,534
80220.79.0.0/16220.79.0.1 to 220.79.255.254220.79.255.25565,534
81220.80.0.0/16220.80.0.1 to 220.80.255.254220.80.255.25565,534
82220.81.0.0/16220.81.0.1 to 220.81.255.254220.81.255.25565,534
83220.82.0.0/16220.82.0.1 to 220.82.255.254220.82.255.25565,534
84220.83.0.0/16220.83.0.1 to 220.83.255.254220.83.255.25565,534
85220.84.0.0/16220.84.0.1 to 220.84.255.254220.84.255.25565,534
86220.85.0.0/16220.85.0.1 to 220.85.255.254220.85.255.25565,534
87220.86.0.0/16220.86.0.1 to 220.86.255.254220.86.255.25565,534
88220.87.0.0/16220.87.0.1 to 220.87.255.254220.87.255.25565,534
89220.88.0.0/16220.88.0.1 to 220.88.255.254220.88.255.25565,534
90220.89.0.0/16220.89.0.1 to 220.89.255.254220.89.255.25565,534
91220.90.0.0/16220.90.0.1 to 220.90.255.254220.90.255.25565,534
92220.91.0.0/16220.91.0.1 to 220.91.255.254220.91.255.25565,534
93220.92.0.0/16220.92.0.1 to 220.92.255.254220.92.255.25565,534
94220.93.0.0/16220.93.0.1 to 220.93.255.254220.93.255.25565,534
95220.94.0.0/16220.94.0.1 to 220.94.255.254220.94.255.25565,534
96220.95.0.0/16220.95.0.1 to 220.95.255.254220.95.255.25565,534
97220.96.0.0/16220.96.0.1 to 220.96.255.254220.96.255.25565,534
98220.97.0.0/16220.97.0.1 to 220.97.255.254220.97.255.25565,534
99220.98.0.0/16220.98.0.1 to 220.98.255.254220.98.255.25565,534
100220.99.0.0/16220.99.0.1 to 220.99.255.254220.99.255.25565,534
101220.100.0.0/16220.100.0.1 to 220.100.255.254220.100.255.25565,534
102220.101.0.0/16220.101.0.1 to 220.101.255.254220.101.255.25565,534
103220.102.0.0/16220.102.0.1 to 220.102.255.254220.102.255.25565,534
104220.103.0.0/16220.103.0.1 to 220.103.255.254220.103.255.25565,534
105220.104.0.0/16220.104.0.1 to 220.104.255.254220.104.255.25565,534
106220.105.0.0/16220.105.0.1 to 220.105.255.254220.105.255.25565,534
107220.106.0.0/16220.106.0.1 to 220.106.255.254220.106.255.25565,534
108220.107.0.0/16220.107.0.1 to 220.107.255.254220.107.255.25565,534
109220.108.0.0/16220.108.0.1 to 220.108.255.254220.108.255.25565,534
110220.109.0.0/16220.109.0.1 to 220.109.255.254220.109.255.25565,534
111220.110.0.0/16220.110.0.1 to 220.110.255.254220.110.255.25565,534
112220.111.0.0/16220.111.0.1 to 220.111.255.254220.111.255.25565,534
113220.112.0.0/16220.112.0.1 to 220.112.255.254220.112.255.25565,534
114220.113.0.0/16220.113.0.1 to 220.113.255.254220.113.255.25565,534
115220.114.0.0/16220.114.0.1 to 220.114.255.254220.114.255.25565,534
116220.115.0.0/16220.115.0.1 to 220.115.255.254220.115.255.25565,534
117220.116.0.0/16220.116.0.1 to 220.116.255.254220.116.255.25565,534
118220.117.0.0/16220.117.0.1 to 220.117.255.254220.117.255.25565,534
119220.118.0.0/16220.118.0.1 to 220.118.255.254220.118.255.25565,534
120220.119.0.0/16220.119.0.1 to 220.119.255.254220.119.255.25565,534
121220.120.0.0/16220.120.0.1 to 220.120.255.254220.120.255.25565,534
122220.121.0.0/16220.121.0.1 to 220.121.255.254220.121.255.25565,534
123220.122.0.0/16220.122.0.1 to 220.122.255.254220.122.255.25565,534
124220.123.0.0/16220.123.0.1 to 220.123.255.254220.123.255.25565,534
125220.124.0.0/16220.124.0.1 to 220.124.255.254220.124.255.25565,534
126220.125.0.0/16220.125.0.1 to 220.125.255.254220.125.255.25565,534
127220.126.0.0/16220.126.0.1 to 220.126.255.254220.126.255.25565,534
128220.127.0.0/16220.127.0.1 to 220.127.255.254220.127.255.25565,534
129220.128.0.0/16220.128.0.1 to 220.128.255.254220.128.255.25565,534
130220.129.0.0/16220.129.0.1 to 220.129.255.254220.129.255.25565,534
131220.130.0.0/16220.130.0.1 to 220.130.255.254220.130.255.25565,534
132220.131.0.0/16220.131.0.1 to 220.131.255.254220.131.255.25565,534
133220.132.0.0/16220.132.0.1 to 220.132.255.254220.132.255.25565,534
134220.133.0.0/16220.133.0.1 to 220.133.255.254220.133.255.25565,534
135220.134.0.0/16220.134.0.1 to 220.134.255.254220.134.255.25565,534
136220.135.0.0/16220.135.0.1 to 220.135.255.254220.135.255.25565,534
137220.136.0.0/16220.136.0.1 to 220.136.255.254220.136.255.25565,534
138220.137.0.0/16220.137.0.1 to 220.137.255.254220.137.255.25565,534
139220.138.0.0/16220.138.0.1 to 220.138.255.254220.138.255.25565,534
140220.139.0.0/16220.139.0.1 to 220.139.255.254220.139.255.25565,534
141220.140.0.0/16220.140.0.1 to 220.140.255.254220.140.255.25565,534
142220.141.0.0/16220.141.0.1 to 220.141.255.254220.141.255.25565,534
143220.142.0.0/16220.142.0.1 to 220.142.255.254220.142.255.25565,534
144220.143.0.0/16220.143.0.1 to 220.143.255.254220.143.255.25565,534
145220.144.0.0/16220.144.0.1 to 220.144.255.254220.144.255.25565,534
146220.145.0.0/16220.145.0.1 to 220.145.255.254220.145.255.25565,534
147220.146.0.0/16220.146.0.1 to 220.146.255.254220.146.255.25565,534
148220.147.0.0/16220.147.0.1 to 220.147.255.254220.147.255.25565,534
149220.148.0.0/16220.148.0.1 to 220.148.255.254220.148.255.25565,534
150220.149.0.0/16220.149.0.1 to 220.149.255.254220.149.255.25565,534
151220.150.0.0/16220.150.0.1 to 220.150.255.254220.150.255.25565,534
152220.151.0.0/16220.151.0.1 to 220.151.255.254220.151.255.25565,534
153220.152.0.0/16220.152.0.1 to 220.152.255.254220.152.255.25565,534
154220.153.0.0/16220.153.0.1 to 220.153.255.254220.153.255.25565,534
155220.154.0.0/16220.154.0.1 to 220.154.255.254220.154.255.25565,534
156220.155.0.0/16220.155.0.1 to 220.155.255.254220.155.255.25565,534
157220.156.0.0/16220.156.0.1 to 220.156.255.254220.156.255.25565,534
158220.157.0.0/16220.157.0.1 to 220.157.255.254220.157.255.25565,534
159220.158.0.0/16220.158.0.1 to 220.158.255.254220.158.255.25565,534
160220.159.0.0/16220.159.0.1 to 220.159.255.254220.159.255.25565,534
161220.160.0.0/16220.160.0.1 to 220.160.255.254220.160.255.25565,534
162220.161.0.0/16220.161.0.1 to 220.161.255.254220.161.255.25565,534
163220.162.0.0/16220.162.0.1 to 220.162.255.254220.162.255.25565,534
164220.163.0.0/16220.163.0.1 to 220.163.255.254220.163.255.25565,534
165220.164.0.0/16220.164.0.1 to 220.164.255.254220.164.255.25565,534
166220.165.0.0/16220.165.0.1 to 220.165.255.254220.165.255.25565,534
167220.166.0.0/16220.166.0.1 to 220.166.255.254220.166.255.25565,534
168220.167.0.0/16220.167.0.1 to 220.167.255.254220.167.255.25565,534
169220.168.0.0/16220.168.0.1 to 220.168.255.254220.168.255.25565,534
170220.169.0.0/16220.169.0.1 to 220.169.255.254220.169.255.25565,534
171220.170.0.0/16220.170.0.1 to 220.170.255.254220.170.255.25565,534
172220.171.0.0/16220.171.0.1 to 220.171.255.254220.171.255.25565,534
173220.172.0.0/16220.172.0.1 to 220.172.255.254220.172.255.25565,534
174220.173.0.0/16220.173.0.1 to 220.173.255.254220.173.255.25565,534
175220.174.0.0/16220.174.0.1 to 220.174.255.254220.174.255.25565,534
176220.175.0.0/16220.175.0.1 to 220.175.255.254220.175.255.25565,534
177220.176.0.0/16220.176.0.1 to 220.176.255.254220.176.255.25565,534
178220.177.0.0/16220.177.0.1 to 220.177.255.254220.177.255.25565,534
179220.178.0.0/16220.178.0.1 to 220.178.255.254220.178.255.25565,534
180220.179.0.0/16220.179.0.1 to 220.179.255.254220.179.255.25565,534
181220.180.0.0/16220.180.0.1 to 220.180.255.254220.180.255.25565,534
182220.181.0.0/16220.181.0.1 to 220.181.255.254220.181.255.25565,534
183220.182.0.0/16220.182.0.1 to 220.182.255.254220.182.255.25565,534
184220.183.0.0/16220.183.0.1 to 220.183.255.254220.183.255.25565,534
185220.184.0.0/16220.184.0.1 to 220.184.255.254220.184.255.25565,534
186220.185.0.0/16220.185.0.1 to 220.185.255.254220.185.255.25565,534
187220.186.0.0/16220.186.0.1 to 220.186.255.254220.186.255.25565,534
188220.187.0.0/16220.187.0.1 to 220.187.255.254220.187.255.25565,534
189220.188.0.0/16220.188.0.1 to 220.188.255.254220.188.255.25565,534
190220.189.0.0/16220.189.0.1 to 220.189.255.254220.189.255.25565,534
191220.190.0.0/16220.190.0.1 to 220.190.255.254220.190.255.25565,534
192220.191.0.0/16220.191.0.1 to 220.191.255.254220.191.255.25565,534
193220.192.0.0/16220.192.0.1 to 220.192.255.254220.192.255.25565,534
194220.193.0.0/16220.193.0.1 to 220.193.255.254220.193.255.25565,534
195220.194.0.0/16220.194.0.1 to 220.194.255.254220.194.255.25565,534
196220.195.0.0/16220.195.0.1 to 220.195.255.254220.195.255.25565,534
197220.196.0.0/16220.196.0.1 to 220.196.255.254220.196.255.25565,534
198220.197.0.0/16220.197.0.1 to 220.197.255.254220.197.255.25565,534
199220.198.0.0/16220.198.0.1 to 220.198.255.254220.198.255.25565,534
200220.199.0.0/16220.199.0.1 to 220.199.255.254220.199.255.25565,534
201220.200.0.0/16220.200.0.1 to 220.200.255.254220.200.255.25565,534
202220.201.0.0/16220.201.0.1 to 220.201.255.254220.201.255.25565,534
203220.202.0.0/16220.202.0.1 to 220.202.255.254220.202.255.25565,534
204220.203.0.0/16220.203.0.1 to 220.203.255.254220.203.255.25565,534
205220.204.0.0/16220.204.0.1 to 220.204.255.254220.204.255.25565,534
206220.205.0.0/16220.205.0.1 to 220.205.255.254220.205.255.25565,534
207220.206.0.0/16220.206.0.1 to 220.206.255.254220.206.255.25565,534
208220.207.0.0/16220.207.0.1 to 220.207.255.254220.207.255.25565,534
209220.208.0.0/16220.208.0.1 to 220.208.255.254220.208.255.25565,534
210220.209.0.0/16220.209.0.1 to 220.209.255.254220.209.255.25565,534
211220.210.0.0/16220.210.0.1 to 220.210.255.254220.210.255.25565,534
212220.211.0.0/16220.211.0.1 to 220.211.255.254220.211.255.25565,534
213220.212.0.0/16220.212.0.1 to 220.212.255.254220.212.255.25565,534
214220.213.0.0/16220.213.0.1 to 220.213.255.254220.213.255.25565,534
215220.214.0.0/16220.214.0.1 to 220.214.255.254220.214.255.25565,534
216220.215.0.0/16220.215.0.1 to 220.215.255.254220.215.255.25565,534
217220.216.0.0/16220.216.0.1 to 220.216.255.254220.216.255.25565,534
218220.217.0.0/16220.217.0.1 to 220.217.255.254220.217.255.25565,534
219220.218.0.0/16220.218.0.1 to 220.218.255.254220.218.255.25565,534
220220.219.0.0/16220.219.0.1 to 220.219.255.254220.219.255.25565,534
221220.220.0.0/16220.220.0.1 to 220.220.255.254220.220.255.25565,534
222220.221.0.0/16220.221.0.1 to 220.221.255.254220.221.255.25565,534
223220.222.0.0/16220.222.0.1 to 220.222.255.254220.222.255.25565,534
224220.223.0.0/16220.223.0.1 to 220.223.255.254220.223.255.25565,534
225220.224.0.0/16220.224.0.1 to 220.224.255.254220.224.255.25565,534
226220.225.0.0/16220.225.0.1 to 220.225.255.254220.225.255.25565,534
227220.226.0.0/16220.226.0.1 to 220.226.255.254220.226.255.25565,534
228220.227.0.0/16220.227.0.1 to 220.227.255.254220.227.255.25565,534
229220.228.0.0/16220.228.0.1 to 220.228.255.254220.228.255.25565,534
230220.229.0.0/16220.229.0.1 to 220.229.255.254220.229.255.25565,534
231220.230.0.0/16220.230.0.1 to 220.230.255.254220.230.255.25565,534
232220.231.0.0/16220.231.0.1 to 220.231.255.254220.231.255.25565,534
233220.232.0.0/16220.232.0.1 to 220.232.255.254220.232.255.25565,534
234220.233.0.0/16220.233.0.1 to 220.233.255.254220.233.255.25565,534
235220.234.0.0/16220.234.0.1 to 220.234.255.254220.234.255.25565,534
236220.235.0.0/16220.235.0.1 to 220.235.255.254220.235.255.25565,534
237220.236.0.0/16220.236.0.1 to 220.236.255.254220.236.255.25565,534
238220.237.0.0/16220.237.0.1 to 220.237.255.254220.237.255.25565,534
239220.238.0.0/16220.238.0.1 to 220.238.255.254220.238.255.25565,534
240220.239.0.0/16220.239.0.1 to 220.239.255.254220.239.255.25565,534
241220.240.0.0/16220.240.0.1 to 220.240.255.254220.240.255.25565,534
242220.241.0.0/16220.241.0.1 to 220.241.255.254220.241.255.25565,534
243220.242.0.0/16220.242.0.1 to 220.242.255.254220.242.255.25565,534
244220.243.0.0/16220.243.0.1 to 220.243.255.254220.243.255.25565,534
245220.244.0.0/16220.244.0.1 to 220.244.255.254220.244.255.25565,534
246220.245.0.0/16220.245.0.1 to 220.245.255.254220.245.255.25565,534
247220.246.0.0/16220.246.0.1 to 220.246.255.254220.246.255.25565,534
248220.247.0.0/16220.247.0.1 to 220.247.255.254220.247.255.25565,534
249220.248.0.0/16220.248.0.1 to 220.248.255.254220.248.255.25565,534
250220.249.0.0/16220.249.0.1 to 220.249.255.254220.249.255.25565,534
251220.250.0.0/16220.250.0.1 to 220.250.255.254220.250.255.25565,534
252220.251.0.0/16220.251.0.1 to 220.251.255.254220.251.255.25565,534
253220.252.0.0/16220.252.0.1 to 220.252.255.254220.252.255.25565,534
254220.253.0.0/16220.253.0.1 to 220.253.255.254220.253.255.25565,534
255220.254.0.0/16220.254.0.1 to 220.254.255.254220.254.255.25565,534
256220.255.0.0/16220.255.0.1 to 220.255.255.254220.255.255.25565,534

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.