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.

Network208.0.0.0/4
Usable hosts268,435,454
Subnet mask240.0.0.0
Addresses268,435,456
Network address
208.0.0.0
Broadcast address
223.255.255.255
First usable
208.0.0.1
Last usable
223.255.255.254
Usable hosts
268,435,454 (268,435,456 less the network and broadcast addresses)
Subnet mask
240.0.0.0
Wildcard mask
15.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/4
Type
Public public
Old class
C (default /24)
As numbers
Hex D0000000 · Integer 3489660928 to 3758096383
Reverse DNS zones
208.in-addr.arpa
209.in-addr.arpa
210.in-addr.arpa
211.in-addr.arpa
212.in-addr.arpa
213.in-addr.arpa
214.in-addr.arpa
215.in-addr.arpa
216.in-addr.arpa
217.in-addr.arpa
218.in-addr.arpa
219.in-addr.arpa
220.in-addr.arpa
221.in-addr.arpa
222.in-addr.arpa
223.in-addr.arpa
/4 is not on a 8-bit boundary, so it takes 16 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11010000.00000000.00000000.00000000208.0.0.0
Subnet mask11110000.00000000.00000000.00000000240.0.0.0
Network11010000.00000000.00000000.00000000208.0.0.0
Broadcast11011111.11111111.11111111.11111111223.255.255.255
Split into smaller subnets/14
/5 (2)/6 (4)/7 (8)/8 (16)/9 (32)/10 (64)/11 (128)/12 (256)/13 (512)/14 (1,024)/15 (2,048)/16 (4,096)

208.0.0.0/4 makes 1,024 subnets of /14; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1208.0.0.0/14208.0.0.1 to 208.3.255.254208.3.255.255262,142
2208.4.0.0/14208.4.0.1 to 208.7.255.254208.7.255.255262,142
3208.8.0.0/14208.8.0.1 to 208.11.255.254208.11.255.255262,142
4208.12.0.0/14208.12.0.1 to 208.15.255.254208.15.255.255262,142
5208.16.0.0/14208.16.0.1 to 208.19.255.254208.19.255.255262,142
6208.20.0.0/14208.20.0.1 to 208.23.255.254208.23.255.255262,142
7208.24.0.0/14208.24.0.1 to 208.27.255.254208.27.255.255262,142
8208.28.0.0/14208.28.0.1 to 208.31.255.254208.31.255.255262,142
9208.32.0.0/14208.32.0.1 to 208.35.255.254208.35.255.255262,142
10208.36.0.0/14208.36.0.1 to 208.39.255.254208.39.255.255262,142
11208.40.0.0/14208.40.0.1 to 208.43.255.254208.43.255.255262,142
12208.44.0.0/14208.44.0.1 to 208.47.255.254208.47.255.255262,142
13208.48.0.0/14208.48.0.1 to 208.51.255.254208.51.255.255262,142
14208.52.0.0/14208.52.0.1 to 208.55.255.254208.55.255.255262,142
15208.56.0.0/14208.56.0.1 to 208.59.255.254208.59.255.255262,142
16208.60.0.0/14208.60.0.1 to 208.63.255.254208.63.255.255262,142
17208.64.0.0/14208.64.0.1 to 208.67.255.254208.67.255.255262,142
18208.68.0.0/14208.68.0.1 to 208.71.255.254208.71.255.255262,142
19208.72.0.0/14208.72.0.1 to 208.75.255.254208.75.255.255262,142
20208.76.0.0/14208.76.0.1 to 208.79.255.254208.79.255.255262,142
21208.80.0.0/14208.80.0.1 to 208.83.255.254208.83.255.255262,142
22208.84.0.0/14208.84.0.1 to 208.87.255.254208.87.255.255262,142
23208.88.0.0/14208.88.0.1 to 208.91.255.254208.91.255.255262,142
24208.92.0.0/14208.92.0.1 to 208.95.255.254208.95.255.255262,142
25208.96.0.0/14208.96.0.1 to 208.99.255.254208.99.255.255262,142
26208.100.0.0/14208.100.0.1 to 208.103.255.254208.103.255.255262,142
27208.104.0.0/14208.104.0.1 to 208.107.255.254208.107.255.255262,142
28208.108.0.0/14208.108.0.1 to 208.111.255.254208.111.255.255262,142
29208.112.0.0/14208.112.0.1 to 208.115.255.254208.115.255.255262,142
30208.116.0.0/14208.116.0.1 to 208.119.255.254208.119.255.255262,142
31208.120.0.0/14208.120.0.1 to 208.123.255.254208.123.255.255262,142
32208.124.0.0/14208.124.0.1 to 208.127.255.254208.127.255.255262,142
33208.128.0.0/14208.128.0.1 to 208.131.255.254208.131.255.255262,142
34208.132.0.0/14208.132.0.1 to 208.135.255.254208.135.255.255262,142
35208.136.0.0/14208.136.0.1 to 208.139.255.254208.139.255.255262,142
36208.140.0.0/14208.140.0.1 to 208.143.255.254208.143.255.255262,142
37208.144.0.0/14208.144.0.1 to 208.147.255.254208.147.255.255262,142
38208.148.0.0/14208.148.0.1 to 208.151.255.254208.151.255.255262,142
39208.152.0.0/14208.152.0.1 to 208.155.255.254208.155.255.255262,142
40208.156.0.0/14208.156.0.1 to 208.159.255.254208.159.255.255262,142
41208.160.0.0/14208.160.0.1 to 208.163.255.254208.163.255.255262,142
42208.164.0.0/14208.164.0.1 to 208.167.255.254208.167.255.255262,142
43208.168.0.0/14208.168.0.1 to 208.171.255.254208.171.255.255262,142
44208.172.0.0/14208.172.0.1 to 208.175.255.254208.175.255.255262,142
45208.176.0.0/14208.176.0.1 to 208.179.255.254208.179.255.255262,142
46208.180.0.0/14208.180.0.1 to 208.183.255.254208.183.255.255262,142
47208.184.0.0/14208.184.0.1 to 208.187.255.254208.187.255.255262,142
48208.188.0.0/14208.188.0.1 to 208.191.255.254208.191.255.255262,142
49208.192.0.0/14208.192.0.1 to 208.195.255.254208.195.255.255262,142
50208.196.0.0/14208.196.0.1 to 208.199.255.254208.199.255.255262,142
51208.200.0.0/14208.200.0.1 to 208.203.255.254208.203.255.255262,142
52208.204.0.0/14208.204.0.1 to 208.207.255.254208.207.255.255262,142
53208.208.0.0/14208.208.0.1 to 208.211.255.254208.211.255.255262,142
54208.212.0.0/14208.212.0.1 to 208.215.255.254208.215.255.255262,142
55208.216.0.0/14208.216.0.1 to 208.219.255.254208.219.255.255262,142
56208.220.0.0/14208.220.0.1 to 208.223.255.254208.223.255.255262,142
57208.224.0.0/14208.224.0.1 to 208.227.255.254208.227.255.255262,142
58208.228.0.0/14208.228.0.1 to 208.231.255.254208.231.255.255262,142
59208.232.0.0/14208.232.0.1 to 208.235.255.254208.235.255.255262,142
60208.236.0.0/14208.236.0.1 to 208.239.255.254208.239.255.255262,142
61208.240.0.0/14208.240.0.1 to 208.243.255.254208.243.255.255262,142
62208.244.0.0/14208.244.0.1 to 208.247.255.254208.247.255.255262,142
63208.248.0.0/14208.248.0.1 to 208.251.255.254208.251.255.255262,142
64208.252.0.0/14208.252.0.1 to 208.255.255.254208.255.255.255262,142
65209.0.0.0/14209.0.0.1 to 209.3.255.254209.3.255.255262,142
66209.4.0.0/14209.4.0.1 to 209.7.255.254209.7.255.255262,142
67209.8.0.0/14209.8.0.1 to 209.11.255.254209.11.255.255262,142
68209.12.0.0/14209.12.0.1 to 209.15.255.254209.15.255.255262,142
69209.16.0.0/14209.16.0.1 to 209.19.255.254209.19.255.255262,142
70209.20.0.0/14209.20.0.1 to 209.23.255.254209.23.255.255262,142
71209.24.0.0/14209.24.0.1 to 209.27.255.254209.27.255.255262,142
72209.28.0.0/14209.28.0.1 to 209.31.255.254209.31.255.255262,142
73209.32.0.0/14209.32.0.1 to 209.35.255.254209.35.255.255262,142
74209.36.0.0/14209.36.0.1 to 209.39.255.254209.39.255.255262,142
75209.40.0.0/14209.40.0.1 to 209.43.255.254209.43.255.255262,142
76209.44.0.0/14209.44.0.1 to 209.47.255.254209.47.255.255262,142
77209.48.0.0/14209.48.0.1 to 209.51.255.254209.51.255.255262,142
78209.52.0.0/14209.52.0.1 to 209.55.255.254209.55.255.255262,142
79209.56.0.0/14209.56.0.1 to 209.59.255.254209.59.255.255262,142
80209.60.0.0/14209.60.0.1 to 209.63.255.254209.63.255.255262,142
81209.64.0.0/14209.64.0.1 to 209.67.255.254209.67.255.255262,142
82209.68.0.0/14209.68.0.1 to 209.71.255.254209.71.255.255262,142
83209.72.0.0/14209.72.0.1 to 209.75.255.254209.75.255.255262,142
84209.76.0.0/14209.76.0.1 to 209.79.255.254209.79.255.255262,142
85209.80.0.0/14209.80.0.1 to 209.83.255.254209.83.255.255262,142
86209.84.0.0/14209.84.0.1 to 209.87.255.254209.87.255.255262,142
87209.88.0.0/14209.88.0.1 to 209.91.255.254209.91.255.255262,142
88209.92.0.0/14209.92.0.1 to 209.95.255.254209.95.255.255262,142
89209.96.0.0/14209.96.0.1 to 209.99.255.254209.99.255.255262,142
90209.100.0.0/14209.100.0.1 to 209.103.255.254209.103.255.255262,142
91209.104.0.0/14209.104.0.1 to 209.107.255.254209.107.255.255262,142
92209.108.0.0/14209.108.0.1 to 209.111.255.254209.111.255.255262,142
93209.112.0.0/14209.112.0.1 to 209.115.255.254209.115.255.255262,142
94209.116.0.0/14209.116.0.1 to 209.119.255.254209.119.255.255262,142
95209.120.0.0/14209.120.0.1 to 209.123.255.254209.123.255.255262,142
96209.124.0.0/14209.124.0.1 to 209.127.255.254209.127.255.255262,142
97209.128.0.0/14209.128.0.1 to 209.131.255.254209.131.255.255262,142
98209.132.0.0/14209.132.0.1 to 209.135.255.254209.135.255.255262,142
99209.136.0.0/14209.136.0.1 to 209.139.255.254209.139.255.255262,142
100209.140.0.0/14209.140.0.1 to 209.143.255.254209.143.255.255262,142
101209.144.0.0/14209.144.0.1 to 209.147.255.254209.147.255.255262,142
102209.148.0.0/14209.148.0.1 to 209.151.255.254209.151.255.255262,142
103209.152.0.0/14209.152.0.1 to 209.155.255.254209.155.255.255262,142
104209.156.0.0/14209.156.0.1 to 209.159.255.254209.159.255.255262,142
105209.160.0.0/14209.160.0.1 to 209.163.255.254209.163.255.255262,142
106209.164.0.0/14209.164.0.1 to 209.167.255.254209.167.255.255262,142
107209.168.0.0/14209.168.0.1 to 209.171.255.254209.171.255.255262,142
108209.172.0.0/14209.172.0.1 to 209.175.255.254209.175.255.255262,142
109209.176.0.0/14209.176.0.1 to 209.179.255.254209.179.255.255262,142
110209.180.0.0/14209.180.0.1 to 209.183.255.254209.183.255.255262,142
111209.184.0.0/14209.184.0.1 to 209.187.255.254209.187.255.255262,142
112209.188.0.0/14209.188.0.1 to 209.191.255.254209.191.255.255262,142
113209.192.0.0/14209.192.0.1 to 209.195.255.254209.195.255.255262,142
114209.196.0.0/14209.196.0.1 to 209.199.255.254209.199.255.255262,142
115209.200.0.0/14209.200.0.1 to 209.203.255.254209.203.255.255262,142
116209.204.0.0/14209.204.0.1 to 209.207.255.254209.207.255.255262,142
117209.208.0.0/14209.208.0.1 to 209.211.255.254209.211.255.255262,142
118209.212.0.0/14209.212.0.1 to 209.215.255.254209.215.255.255262,142
119209.216.0.0/14209.216.0.1 to 209.219.255.254209.219.255.255262,142
120209.220.0.0/14209.220.0.1 to 209.223.255.254209.223.255.255262,142
121209.224.0.0/14209.224.0.1 to 209.227.255.254209.227.255.255262,142
122209.228.0.0/14209.228.0.1 to 209.231.255.254209.231.255.255262,142
123209.232.0.0/14209.232.0.1 to 209.235.255.254209.235.255.255262,142
124209.236.0.0/14209.236.0.1 to 209.239.255.254209.239.255.255262,142
125209.240.0.0/14209.240.0.1 to 209.243.255.254209.243.255.255262,142
126209.244.0.0/14209.244.0.1 to 209.247.255.254209.247.255.255262,142
127209.248.0.0/14209.248.0.1 to 209.251.255.254209.251.255.255262,142
128209.252.0.0/14209.252.0.1 to 209.255.255.254209.255.255.255262,142
129210.0.0.0/14210.0.0.1 to 210.3.255.254210.3.255.255262,142
130210.4.0.0/14210.4.0.1 to 210.7.255.254210.7.255.255262,142
131210.8.0.0/14210.8.0.1 to 210.11.255.254210.11.255.255262,142
132210.12.0.0/14210.12.0.1 to 210.15.255.254210.15.255.255262,142
133210.16.0.0/14210.16.0.1 to 210.19.255.254210.19.255.255262,142
134210.20.0.0/14210.20.0.1 to 210.23.255.254210.23.255.255262,142
135210.24.0.0/14210.24.0.1 to 210.27.255.254210.27.255.255262,142
136210.28.0.0/14210.28.0.1 to 210.31.255.254210.31.255.255262,142
137210.32.0.0/14210.32.0.1 to 210.35.255.254210.35.255.255262,142
138210.36.0.0/14210.36.0.1 to 210.39.255.254210.39.255.255262,142
139210.40.0.0/14210.40.0.1 to 210.43.255.254210.43.255.255262,142
140210.44.0.0/14210.44.0.1 to 210.47.255.254210.47.255.255262,142
141210.48.0.0/14210.48.0.1 to 210.51.255.254210.51.255.255262,142
142210.52.0.0/14210.52.0.1 to 210.55.255.254210.55.255.255262,142
143210.56.0.0/14210.56.0.1 to 210.59.255.254210.59.255.255262,142
144210.60.0.0/14210.60.0.1 to 210.63.255.254210.63.255.255262,142
145210.64.0.0/14210.64.0.1 to 210.67.255.254210.67.255.255262,142
146210.68.0.0/14210.68.0.1 to 210.71.255.254210.71.255.255262,142
147210.72.0.0/14210.72.0.1 to 210.75.255.254210.75.255.255262,142
148210.76.0.0/14210.76.0.1 to 210.79.255.254210.79.255.255262,142
149210.80.0.0/14210.80.0.1 to 210.83.255.254210.83.255.255262,142
150210.84.0.0/14210.84.0.1 to 210.87.255.254210.87.255.255262,142
151210.88.0.0/14210.88.0.1 to 210.91.255.254210.91.255.255262,142
152210.92.0.0/14210.92.0.1 to 210.95.255.254210.95.255.255262,142
153210.96.0.0/14210.96.0.1 to 210.99.255.254210.99.255.255262,142
154210.100.0.0/14210.100.0.1 to 210.103.255.254210.103.255.255262,142
155210.104.0.0/14210.104.0.1 to 210.107.255.254210.107.255.255262,142
156210.108.0.0/14210.108.0.1 to 210.111.255.254210.111.255.255262,142
157210.112.0.0/14210.112.0.1 to 210.115.255.254210.115.255.255262,142
158210.116.0.0/14210.116.0.1 to 210.119.255.254210.119.255.255262,142
159210.120.0.0/14210.120.0.1 to 210.123.255.254210.123.255.255262,142
160210.124.0.0/14210.124.0.1 to 210.127.255.254210.127.255.255262,142
161210.128.0.0/14210.128.0.1 to 210.131.255.254210.131.255.255262,142
162210.132.0.0/14210.132.0.1 to 210.135.255.254210.135.255.255262,142
163210.136.0.0/14210.136.0.1 to 210.139.255.254210.139.255.255262,142
164210.140.0.0/14210.140.0.1 to 210.143.255.254210.143.255.255262,142
165210.144.0.0/14210.144.0.1 to 210.147.255.254210.147.255.255262,142
166210.148.0.0/14210.148.0.1 to 210.151.255.254210.151.255.255262,142
167210.152.0.0/14210.152.0.1 to 210.155.255.254210.155.255.255262,142
168210.156.0.0/14210.156.0.1 to 210.159.255.254210.159.255.255262,142
169210.160.0.0/14210.160.0.1 to 210.163.255.254210.163.255.255262,142
170210.164.0.0/14210.164.0.1 to 210.167.255.254210.167.255.255262,142
171210.168.0.0/14210.168.0.1 to 210.171.255.254210.171.255.255262,142
172210.172.0.0/14210.172.0.1 to 210.175.255.254210.175.255.255262,142
173210.176.0.0/14210.176.0.1 to 210.179.255.254210.179.255.255262,142
174210.180.0.0/14210.180.0.1 to 210.183.255.254210.183.255.255262,142
175210.184.0.0/14210.184.0.1 to 210.187.255.254210.187.255.255262,142
176210.188.0.0/14210.188.0.1 to 210.191.255.254210.191.255.255262,142
177210.192.0.0/14210.192.0.1 to 210.195.255.254210.195.255.255262,142
178210.196.0.0/14210.196.0.1 to 210.199.255.254210.199.255.255262,142
179210.200.0.0/14210.200.0.1 to 210.203.255.254210.203.255.255262,142
180210.204.0.0/14210.204.0.1 to 210.207.255.254210.207.255.255262,142
181210.208.0.0/14210.208.0.1 to 210.211.255.254210.211.255.255262,142
182210.212.0.0/14210.212.0.1 to 210.215.255.254210.215.255.255262,142
183210.216.0.0/14210.216.0.1 to 210.219.255.254210.219.255.255262,142
184210.220.0.0/14210.220.0.1 to 210.223.255.254210.223.255.255262,142
185210.224.0.0/14210.224.0.1 to 210.227.255.254210.227.255.255262,142
186210.228.0.0/14210.228.0.1 to 210.231.255.254210.231.255.255262,142
187210.232.0.0/14210.232.0.1 to 210.235.255.254210.235.255.255262,142
188210.236.0.0/14210.236.0.1 to 210.239.255.254210.239.255.255262,142
189210.240.0.0/14210.240.0.1 to 210.243.255.254210.243.255.255262,142
190210.244.0.0/14210.244.0.1 to 210.247.255.254210.247.255.255262,142
191210.248.0.0/14210.248.0.1 to 210.251.255.254210.251.255.255262,142
192210.252.0.0/14210.252.0.1 to 210.255.255.254210.255.255.255262,142
193211.0.0.0/14211.0.0.1 to 211.3.255.254211.3.255.255262,142
194211.4.0.0/14211.4.0.1 to 211.7.255.254211.7.255.255262,142
195211.8.0.0/14211.8.0.1 to 211.11.255.254211.11.255.255262,142
196211.12.0.0/14211.12.0.1 to 211.15.255.254211.15.255.255262,142
197211.16.0.0/14211.16.0.1 to 211.19.255.254211.19.255.255262,142
198211.20.0.0/14211.20.0.1 to 211.23.255.254211.23.255.255262,142
199211.24.0.0/14211.24.0.1 to 211.27.255.254211.27.255.255262,142
200211.28.0.0/14211.28.0.1 to 211.31.255.254211.31.255.255262,142
201211.32.0.0/14211.32.0.1 to 211.35.255.254211.35.255.255262,142
202211.36.0.0/14211.36.0.1 to 211.39.255.254211.39.255.255262,142
203211.40.0.0/14211.40.0.1 to 211.43.255.254211.43.255.255262,142
204211.44.0.0/14211.44.0.1 to 211.47.255.254211.47.255.255262,142
205211.48.0.0/14211.48.0.1 to 211.51.255.254211.51.255.255262,142
206211.52.0.0/14211.52.0.1 to 211.55.255.254211.55.255.255262,142
207211.56.0.0/14211.56.0.1 to 211.59.255.254211.59.255.255262,142
208211.60.0.0/14211.60.0.1 to 211.63.255.254211.63.255.255262,142
209211.64.0.0/14211.64.0.1 to 211.67.255.254211.67.255.255262,142
210211.68.0.0/14211.68.0.1 to 211.71.255.254211.71.255.255262,142
211211.72.0.0/14211.72.0.1 to 211.75.255.254211.75.255.255262,142
212211.76.0.0/14211.76.0.1 to 211.79.255.254211.79.255.255262,142
213211.80.0.0/14211.80.0.1 to 211.83.255.254211.83.255.255262,142
214211.84.0.0/14211.84.0.1 to 211.87.255.254211.87.255.255262,142
215211.88.0.0/14211.88.0.1 to 211.91.255.254211.91.255.255262,142
216211.92.0.0/14211.92.0.1 to 211.95.255.254211.95.255.255262,142
217211.96.0.0/14211.96.0.1 to 211.99.255.254211.99.255.255262,142
218211.100.0.0/14211.100.0.1 to 211.103.255.254211.103.255.255262,142
219211.104.0.0/14211.104.0.1 to 211.107.255.254211.107.255.255262,142
220211.108.0.0/14211.108.0.1 to 211.111.255.254211.111.255.255262,142
221211.112.0.0/14211.112.0.1 to 211.115.255.254211.115.255.255262,142
222211.116.0.0/14211.116.0.1 to 211.119.255.254211.119.255.255262,142
223211.120.0.0/14211.120.0.1 to 211.123.255.254211.123.255.255262,142
224211.124.0.0/14211.124.0.1 to 211.127.255.254211.127.255.255262,142
225211.128.0.0/14211.128.0.1 to 211.131.255.254211.131.255.255262,142
226211.132.0.0/14211.132.0.1 to 211.135.255.254211.135.255.255262,142
227211.136.0.0/14211.136.0.1 to 211.139.255.254211.139.255.255262,142
228211.140.0.0/14211.140.0.1 to 211.143.255.254211.143.255.255262,142
229211.144.0.0/14211.144.0.1 to 211.147.255.254211.147.255.255262,142
230211.148.0.0/14211.148.0.1 to 211.151.255.254211.151.255.255262,142
231211.152.0.0/14211.152.0.1 to 211.155.255.254211.155.255.255262,142
232211.156.0.0/14211.156.0.1 to 211.159.255.254211.159.255.255262,142
233211.160.0.0/14211.160.0.1 to 211.163.255.254211.163.255.255262,142
234211.164.0.0/14211.164.0.1 to 211.167.255.254211.167.255.255262,142
235211.168.0.0/14211.168.0.1 to 211.171.255.254211.171.255.255262,142
236211.172.0.0/14211.172.0.1 to 211.175.255.254211.175.255.255262,142
237211.176.0.0/14211.176.0.1 to 211.179.255.254211.179.255.255262,142
238211.180.0.0/14211.180.0.1 to 211.183.255.254211.183.255.255262,142
239211.184.0.0/14211.184.0.1 to 211.187.255.254211.187.255.255262,142
240211.188.0.0/14211.188.0.1 to 211.191.255.254211.191.255.255262,142
241211.192.0.0/14211.192.0.1 to 211.195.255.254211.195.255.255262,142
242211.196.0.0/14211.196.0.1 to 211.199.255.254211.199.255.255262,142
243211.200.0.0/14211.200.0.1 to 211.203.255.254211.203.255.255262,142
244211.204.0.0/14211.204.0.1 to 211.207.255.254211.207.255.255262,142
245211.208.0.0/14211.208.0.1 to 211.211.255.254211.211.255.255262,142
246211.212.0.0/14211.212.0.1 to 211.215.255.254211.215.255.255262,142
247211.216.0.0/14211.216.0.1 to 211.219.255.254211.219.255.255262,142
248211.220.0.0/14211.220.0.1 to 211.223.255.254211.223.255.255262,142
249211.224.0.0/14211.224.0.1 to 211.227.255.254211.227.255.255262,142
250211.228.0.0/14211.228.0.1 to 211.231.255.254211.231.255.255262,142
251211.232.0.0/14211.232.0.1 to 211.235.255.254211.235.255.255262,142
252211.236.0.0/14211.236.0.1 to 211.239.255.254211.239.255.255262,142
253211.240.0.0/14211.240.0.1 to 211.243.255.254211.243.255.255262,142
254211.244.0.0/14211.244.0.1 to 211.247.255.254211.247.255.255262,142
255211.248.0.0/14211.248.0.1 to 211.251.255.254211.251.255.255262,142
256211.252.0.0/14211.252.0.1 to 211.255.255.254211.255.255.255262,142

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.