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.

Network254.3.0.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
254.3.0.0
Broadcast address
254.3.31.255
First usable
254.3.0.1
Last usable
254.3.31.254
Usable hosts
8,190 (8,192 less the network and broadcast addresses)
Subnet mask
255.255.224.0
Wildcard mask
0.0.31.255 (Cisco ACLs, OSPF)
Prefix length
/19
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex FE030000 · Integer 4261609472 to 4261617663
Reverse DNS zones
0.3.254.in-addr.arpa
1.3.254.in-addr.arpa
2.3.254.in-addr.arpa
3.3.254.in-addr.arpa
4.3.254.in-addr.arpa
5.3.254.in-addr.arpa
6.3.254.in-addr.arpa
7.3.254.in-addr.arpa
8.3.254.in-addr.arpa
9.3.254.in-addr.arpa
10.3.254.in-addr.arpa
11.3.254.in-addr.arpa
12.3.254.in-addr.arpa
13.3.254.in-addr.arpa
14.3.254.in-addr.arpa
15.3.254.in-addr.arpa
and 16 more
/19 is not on a 8-bit boundary, so it takes 32 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11111110.00000011.00000000.00000000254.3.0.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network11111110.00000011.00000000.00000000254.3.0.0
Broadcast11111110.00000011.00011111.11111111254.3.31.255
Split into smaller subnets/27
/20 (2)/21 (4)/22 (8)/23 (16)/24 (32)/25 (64)/26 (128)/27 (256)/28 (512)/29 (1,024)/30 (2,048)/31 (4,096)

254.3.0.0/19 makes 256 subnets of /27.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1254.3.0.0/27254.3.0.1 to 254.3.0.30254.3.0.3130
2254.3.0.32/27254.3.0.33 to 254.3.0.62254.3.0.6330
3254.3.0.64/27254.3.0.65 to 254.3.0.94254.3.0.9530
4254.3.0.96/27254.3.0.97 to 254.3.0.126254.3.0.12730
5254.3.0.128/27254.3.0.129 to 254.3.0.158254.3.0.15930
6254.3.0.160/27254.3.0.161 to 254.3.0.190254.3.0.19130
7254.3.0.192/27254.3.0.193 to 254.3.0.222254.3.0.22330
8254.3.0.224/27254.3.0.225 to 254.3.0.254254.3.0.25530
9254.3.1.0/27254.3.1.1 to 254.3.1.30254.3.1.3130
10254.3.1.32/27254.3.1.33 to 254.3.1.62254.3.1.6330
11254.3.1.64/27254.3.1.65 to 254.3.1.94254.3.1.9530
12254.3.1.96/27254.3.1.97 to 254.3.1.126254.3.1.12730
13254.3.1.128/27254.3.1.129 to 254.3.1.158254.3.1.15930
14254.3.1.160/27254.3.1.161 to 254.3.1.190254.3.1.19130
15254.3.1.192/27254.3.1.193 to 254.3.1.222254.3.1.22330
16254.3.1.224/27254.3.1.225 to 254.3.1.254254.3.1.25530
17254.3.2.0/27254.3.2.1 to 254.3.2.30254.3.2.3130
18254.3.2.32/27254.3.2.33 to 254.3.2.62254.3.2.6330
19254.3.2.64/27254.3.2.65 to 254.3.2.94254.3.2.9530
20254.3.2.96/27254.3.2.97 to 254.3.2.126254.3.2.12730
21254.3.2.128/27254.3.2.129 to 254.3.2.158254.3.2.15930
22254.3.2.160/27254.3.2.161 to 254.3.2.190254.3.2.19130
23254.3.2.192/27254.3.2.193 to 254.3.2.222254.3.2.22330
24254.3.2.224/27254.3.2.225 to 254.3.2.254254.3.2.25530
25254.3.3.0/27254.3.3.1 to 254.3.3.30254.3.3.3130
26254.3.3.32/27254.3.3.33 to 254.3.3.62254.3.3.6330
27254.3.3.64/27254.3.3.65 to 254.3.3.94254.3.3.9530
28254.3.3.96/27254.3.3.97 to 254.3.3.126254.3.3.12730
29254.3.3.128/27254.3.3.129 to 254.3.3.158254.3.3.15930
30254.3.3.160/27254.3.3.161 to 254.3.3.190254.3.3.19130
31254.3.3.192/27254.3.3.193 to 254.3.3.222254.3.3.22330
32254.3.3.224/27254.3.3.225 to 254.3.3.254254.3.3.25530
33254.3.4.0/27254.3.4.1 to 254.3.4.30254.3.4.3130
34254.3.4.32/27254.3.4.33 to 254.3.4.62254.3.4.6330
35254.3.4.64/27254.3.4.65 to 254.3.4.94254.3.4.9530
36254.3.4.96/27254.3.4.97 to 254.3.4.126254.3.4.12730
37254.3.4.128/27254.3.4.129 to 254.3.4.158254.3.4.15930
38254.3.4.160/27254.3.4.161 to 254.3.4.190254.3.4.19130
39254.3.4.192/27254.3.4.193 to 254.3.4.222254.3.4.22330
40254.3.4.224/27254.3.4.225 to 254.3.4.254254.3.4.25530
41254.3.5.0/27254.3.5.1 to 254.3.5.30254.3.5.3130
42254.3.5.32/27254.3.5.33 to 254.3.5.62254.3.5.6330
43254.3.5.64/27254.3.5.65 to 254.3.5.94254.3.5.9530
44254.3.5.96/27254.3.5.97 to 254.3.5.126254.3.5.12730
45254.3.5.128/27254.3.5.129 to 254.3.5.158254.3.5.15930
46254.3.5.160/27254.3.5.161 to 254.3.5.190254.3.5.19130
47254.3.5.192/27254.3.5.193 to 254.3.5.222254.3.5.22330
48254.3.5.224/27254.3.5.225 to 254.3.5.254254.3.5.25530
49254.3.6.0/27254.3.6.1 to 254.3.6.30254.3.6.3130
50254.3.6.32/27254.3.6.33 to 254.3.6.62254.3.6.6330
51254.3.6.64/27254.3.6.65 to 254.3.6.94254.3.6.9530
52254.3.6.96/27254.3.6.97 to 254.3.6.126254.3.6.12730
53254.3.6.128/27254.3.6.129 to 254.3.6.158254.3.6.15930
54254.3.6.160/27254.3.6.161 to 254.3.6.190254.3.6.19130
55254.3.6.192/27254.3.6.193 to 254.3.6.222254.3.6.22330
56254.3.6.224/27254.3.6.225 to 254.3.6.254254.3.6.25530
57254.3.7.0/27254.3.7.1 to 254.3.7.30254.3.7.3130
58254.3.7.32/27254.3.7.33 to 254.3.7.62254.3.7.6330
59254.3.7.64/27254.3.7.65 to 254.3.7.94254.3.7.9530
60254.3.7.96/27254.3.7.97 to 254.3.7.126254.3.7.12730
61254.3.7.128/27254.3.7.129 to 254.3.7.158254.3.7.15930
62254.3.7.160/27254.3.7.161 to 254.3.7.190254.3.7.19130
63254.3.7.192/27254.3.7.193 to 254.3.7.222254.3.7.22330
64254.3.7.224/27254.3.7.225 to 254.3.7.254254.3.7.25530
65254.3.8.0/27254.3.8.1 to 254.3.8.30254.3.8.3130
66254.3.8.32/27254.3.8.33 to 254.3.8.62254.3.8.6330
67254.3.8.64/27254.3.8.65 to 254.3.8.94254.3.8.9530
68254.3.8.96/27254.3.8.97 to 254.3.8.126254.3.8.12730
69254.3.8.128/27254.3.8.129 to 254.3.8.158254.3.8.15930
70254.3.8.160/27254.3.8.161 to 254.3.8.190254.3.8.19130
71254.3.8.192/27254.3.8.193 to 254.3.8.222254.3.8.22330
72254.3.8.224/27254.3.8.225 to 254.3.8.254254.3.8.25530
73254.3.9.0/27254.3.9.1 to 254.3.9.30254.3.9.3130
74254.3.9.32/27254.3.9.33 to 254.3.9.62254.3.9.6330
75254.3.9.64/27254.3.9.65 to 254.3.9.94254.3.9.9530
76254.3.9.96/27254.3.9.97 to 254.3.9.126254.3.9.12730
77254.3.9.128/27254.3.9.129 to 254.3.9.158254.3.9.15930
78254.3.9.160/27254.3.9.161 to 254.3.9.190254.3.9.19130
79254.3.9.192/27254.3.9.193 to 254.3.9.222254.3.9.22330
80254.3.9.224/27254.3.9.225 to 254.3.9.254254.3.9.25530
81254.3.10.0/27254.3.10.1 to 254.3.10.30254.3.10.3130
82254.3.10.32/27254.3.10.33 to 254.3.10.62254.3.10.6330
83254.3.10.64/27254.3.10.65 to 254.3.10.94254.3.10.9530
84254.3.10.96/27254.3.10.97 to 254.3.10.126254.3.10.12730
85254.3.10.128/27254.3.10.129 to 254.3.10.158254.3.10.15930
86254.3.10.160/27254.3.10.161 to 254.3.10.190254.3.10.19130
87254.3.10.192/27254.3.10.193 to 254.3.10.222254.3.10.22330
88254.3.10.224/27254.3.10.225 to 254.3.10.254254.3.10.25530
89254.3.11.0/27254.3.11.1 to 254.3.11.30254.3.11.3130
90254.3.11.32/27254.3.11.33 to 254.3.11.62254.3.11.6330
91254.3.11.64/27254.3.11.65 to 254.3.11.94254.3.11.9530
92254.3.11.96/27254.3.11.97 to 254.3.11.126254.3.11.12730
93254.3.11.128/27254.3.11.129 to 254.3.11.158254.3.11.15930
94254.3.11.160/27254.3.11.161 to 254.3.11.190254.3.11.19130
95254.3.11.192/27254.3.11.193 to 254.3.11.222254.3.11.22330
96254.3.11.224/27254.3.11.225 to 254.3.11.254254.3.11.25530
97254.3.12.0/27254.3.12.1 to 254.3.12.30254.3.12.3130
98254.3.12.32/27254.3.12.33 to 254.3.12.62254.3.12.6330
99254.3.12.64/27254.3.12.65 to 254.3.12.94254.3.12.9530
100254.3.12.96/27254.3.12.97 to 254.3.12.126254.3.12.12730
101254.3.12.128/27254.3.12.129 to 254.3.12.158254.3.12.15930
102254.3.12.160/27254.3.12.161 to 254.3.12.190254.3.12.19130
103254.3.12.192/27254.3.12.193 to 254.3.12.222254.3.12.22330
104254.3.12.224/27254.3.12.225 to 254.3.12.254254.3.12.25530
105254.3.13.0/27254.3.13.1 to 254.3.13.30254.3.13.3130
106254.3.13.32/27254.3.13.33 to 254.3.13.62254.3.13.6330
107254.3.13.64/27254.3.13.65 to 254.3.13.94254.3.13.9530
108254.3.13.96/27254.3.13.97 to 254.3.13.126254.3.13.12730
109254.3.13.128/27254.3.13.129 to 254.3.13.158254.3.13.15930
110254.3.13.160/27254.3.13.161 to 254.3.13.190254.3.13.19130
111254.3.13.192/27254.3.13.193 to 254.3.13.222254.3.13.22330
112254.3.13.224/27254.3.13.225 to 254.3.13.254254.3.13.25530
113254.3.14.0/27254.3.14.1 to 254.3.14.30254.3.14.3130
114254.3.14.32/27254.3.14.33 to 254.3.14.62254.3.14.6330
115254.3.14.64/27254.3.14.65 to 254.3.14.94254.3.14.9530
116254.3.14.96/27254.3.14.97 to 254.3.14.126254.3.14.12730
117254.3.14.128/27254.3.14.129 to 254.3.14.158254.3.14.15930
118254.3.14.160/27254.3.14.161 to 254.3.14.190254.3.14.19130
119254.3.14.192/27254.3.14.193 to 254.3.14.222254.3.14.22330
120254.3.14.224/27254.3.14.225 to 254.3.14.254254.3.14.25530
121254.3.15.0/27254.3.15.1 to 254.3.15.30254.3.15.3130
122254.3.15.32/27254.3.15.33 to 254.3.15.62254.3.15.6330
123254.3.15.64/27254.3.15.65 to 254.3.15.94254.3.15.9530
124254.3.15.96/27254.3.15.97 to 254.3.15.126254.3.15.12730
125254.3.15.128/27254.3.15.129 to 254.3.15.158254.3.15.15930
126254.3.15.160/27254.3.15.161 to 254.3.15.190254.3.15.19130
127254.3.15.192/27254.3.15.193 to 254.3.15.222254.3.15.22330
128254.3.15.224/27254.3.15.225 to 254.3.15.254254.3.15.25530
129254.3.16.0/27254.3.16.1 to 254.3.16.30254.3.16.3130
130254.3.16.32/27254.3.16.33 to 254.3.16.62254.3.16.6330
131254.3.16.64/27254.3.16.65 to 254.3.16.94254.3.16.9530
132254.3.16.96/27254.3.16.97 to 254.3.16.126254.3.16.12730
133254.3.16.128/27254.3.16.129 to 254.3.16.158254.3.16.15930
134254.3.16.160/27254.3.16.161 to 254.3.16.190254.3.16.19130
135254.3.16.192/27254.3.16.193 to 254.3.16.222254.3.16.22330
136254.3.16.224/27254.3.16.225 to 254.3.16.254254.3.16.25530
137254.3.17.0/27254.3.17.1 to 254.3.17.30254.3.17.3130
138254.3.17.32/27254.3.17.33 to 254.3.17.62254.3.17.6330
139254.3.17.64/27254.3.17.65 to 254.3.17.94254.3.17.9530
140254.3.17.96/27254.3.17.97 to 254.3.17.126254.3.17.12730
141254.3.17.128/27254.3.17.129 to 254.3.17.158254.3.17.15930
142254.3.17.160/27254.3.17.161 to 254.3.17.190254.3.17.19130
143254.3.17.192/27254.3.17.193 to 254.3.17.222254.3.17.22330
144254.3.17.224/27254.3.17.225 to 254.3.17.254254.3.17.25530
145254.3.18.0/27254.3.18.1 to 254.3.18.30254.3.18.3130
146254.3.18.32/27254.3.18.33 to 254.3.18.62254.3.18.6330
147254.3.18.64/27254.3.18.65 to 254.3.18.94254.3.18.9530
148254.3.18.96/27254.3.18.97 to 254.3.18.126254.3.18.12730
149254.3.18.128/27254.3.18.129 to 254.3.18.158254.3.18.15930
150254.3.18.160/27254.3.18.161 to 254.3.18.190254.3.18.19130
151254.3.18.192/27254.3.18.193 to 254.3.18.222254.3.18.22330
152254.3.18.224/27254.3.18.225 to 254.3.18.254254.3.18.25530
153254.3.19.0/27254.3.19.1 to 254.3.19.30254.3.19.3130
154254.3.19.32/27254.3.19.33 to 254.3.19.62254.3.19.6330
155254.3.19.64/27254.3.19.65 to 254.3.19.94254.3.19.9530
156254.3.19.96/27254.3.19.97 to 254.3.19.126254.3.19.12730
157254.3.19.128/27254.3.19.129 to 254.3.19.158254.3.19.15930
158254.3.19.160/27254.3.19.161 to 254.3.19.190254.3.19.19130
159254.3.19.192/27254.3.19.193 to 254.3.19.222254.3.19.22330
160254.3.19.224/27254.3.19.225 to 254.3.19.254254.3.19.25530
161254.3.20.0/27254.3.20.1 to 254.3.20.30254.3.20.3130
162254.3.20.32/27254.3.20.33 to 254.3.20.62254.3.20.6330
163254.3.20.64/27254.3.20.65 to 254.3.20.94254.3.20.9530
164254.3.20.96/27254.3.20.97 to 254.3.20.126254.3.20.12730
165254.3.20.128/27254.3.20.129 to 254.3.20.158254.3.20.15930
166254.3.20.160/27254.3.20.161 to 254.3.20.190254.3.20.19130
167254.3.20.192/27254.3.20.193 to 254.3.20.222254.3.20.22330
168254.3.20.224/27254.3.20.225 to 254.3.20.254254.3.20.25530
169254.3.21.0/27254.3.21.1 to 254.3.21.30254.3.21.3130
170254.3.21.32/27254.3.21.33 to 254.3.21.62254.3.21.6330
171254.3.21.64/27254.3.21.65 to 254.3.21.94254.3.21.9530
172254.3.21.96/27254.3.21.97 to 254.3.21.126254.3.21.12730
173254.3.21.128/27254.3.21.129 to 254.3.21.158254.3.21.15930
174254.3.21.160/27254.3.21.161 to 254.3.21.190254.3.21.19130
175254.3.21.192/27254.3.21.193 to 254.3.21.222254.3.21.22330
176254.3.21.224/27254.3.21.225 to 254.3.21.254254.3.21.25530
177254.3.22.0/27254.3.22.1 to 254.3.22.30254.3.22.3130
178254.3.22.32/27254.3.22.33 to 254.3.22.62254.3.22.6330
179254.3.22.64/27254.3.22.65 to 254.3.22.94254.3.22.9530
180254.3.22.96/27254.3.22.97 to 254.3.22.126254.3.22.12730
181254.3.22.128/27254.3.22.129 to 254.3.22.158254.3.22.15930
182254.3.22.160/27254.3.22.161 to 254.3.22.190254.3.22.19130
183254.3.22.192/27254.3.22.193 to 254.3.22.222254.3.22.22330
184254.3.22.224/27254.3.22.225 to 254.3.22.254254.3.22.25530
185254.3.23.0/27254.3.23.1 to 254.3.23.30254.3.23.3130
186254.3.23.32/27254.3.23.33 to 254.3.23.62254.3.23.6330
187254.3.23.64/27254.3.23.65 to 254.3.23.94254.3.23.9530
188254.3.23.96/27254.3.23.97 to 254.3.23.126254.3.23.12730
189254.3.23.128/27254.3.23.129 to 254.3.23.158254.3.23.15930
190254.3.23.160/27254.3.23.161 to 254.3.23.190254.3.23.19130
191254.3.23.192/27254.3.23.193 to 254.3.23.222254.3.23.22330
192254.3.23.224/27254.3.23.225 to 254.3.23.254254.3.23.25530
193254.3.24.0/27254.3.24.1 to 254.3.24.30254.3.24.3130
194254.3.24.32/27254.3.24.33 to 254.3.24.62254.3.24.6330
195254.3.24.64/27254.3.24.65 to 254.3.24.94254.3.24.9530
196254.3.24.96/27254.3.24.97 to 254.3.24.126254.3.24.12730
197254.3.24.128/27254.3.24.129 to 254.3.24.158254.3.24.15930
198254.3.24.160/27254.3.24.161 to 254.3.24.190254.3.24.19130
199254.3.24.192/27254.3.24.193 to 254.3.24.222254.3.24.22330
200254.3.24.224/27254.3.24.225 to 254.3.24.254254.3.24.25530
201254.3.25.0/27254.3.25.1 to 254.3.25.30254.3.25.3130
202254.3.25.32/27254.3.25.33 to 254.3.25.62254.3.25.6330
203254.3.25.64/27254.3.25.65 to 254.3.25.94254.3.25.9530
204254.3.25.96/27254.3.25.97 to 254.3.25.126254.3.25.12730
205254.3.25.128/27254.3.25.129 to 254.3.25.158254.3.25.15930
206254.3.25.160/27254.3.25.161 to 254.3.25.190254.3.25.19130
207254.3.25.192/27254.3.25.193 to 254.3.25.222254.3.25.22330
208254.3.25.224/27254.3.25.225 to 254.3.25.254254.3.25.25530
209254.3.26.0/27254.3.26.1 to 254.3.26.30254.3.26.3130
210254.3.26.32/27254.3.26.33 to 254.3.26.62254.3.26.6330
211254.3.26.64/27254.3.26.65 to 254.3.26.94254.3.26.9530
212254.3.26.96/27254.3.26.97 to 254.3.26.126254.3.26.12730
213254.3.26.128/27254.3.26.129 to 254.3.26.158254.3.26.15930
214254.3.26.160/27254.3.26.161 to 254.3.26.190254.3.26.19130
215254.3.26.192/27254.3.26.193 to 254.3.26.222254.3.26.22330
216254.3.26.224/27254.3.26.225 to 254.3.26.254254.3.26.25530
217254.3.27.0/27254.3.27.1 to 254.3.27.30254.3.27.3130
218254.3.27.32/27254.3.27.33 to 254.3.27.62254.3.27.6330
219254.3.27.64/27254.3.27.65 to 254.3.27.94254.3.27.9530
220254.3.27.96/27254.3.27.97 to 254.3.27.126254.3.27.12730
221254.3.27.128/27254.3.27.129 to 254.3.27.158254.3.27.15930
222254.3.27.160/27254.3.27.161 to 254.3.27.190254.3.27.19130
223254.3.27.192/27254.3.27.193 to 254.3.27.222254.3.27.22330
224254.3.27.224/27254.3.27.225 to 254.3.27.254254.3.27.25530
225254.3.28.0/27254.3.28.1 to 254.3.28.30254.3.28.3130
226254.3.28.32/27254.3.28.33 to 254.3.28.62254.3.28.6330
227254.3.28.64/27254.3.28.65 to 254.3.28.94254.3.28.9530
228254.3.28.96/27254.3.28.97 to 254.3.28.126254.3.28.12730
229254.3.28.128/27254.3.28.129 to 254.3.28.158254.3.28.15930
230254.3.28.160/27254.3.28.161 to 254.3.28.190254.3.28.19130
231254.3.28.192/27254.3.28.193 to 254.3.28.222254.3.28.22330
232254.3.28.224/27254.3.28.225 to 254.3.28.254254.3.28.25530
233254.3.29.0/27254.3.29.1 to 254.3.29.30254.3.29.3130
234254.3.29.32/27254.3.29.33 to 254.3.29.62254.3.29.6330
235254.3.29.64/27254.3.29.65 to 254.3.29.94254.3.29.9530
236254.3.29.96/27254.3.29.97 to 254.3.29.126254.3.29.12730
237254.3.29.128/27254.3.29.129 to 254.3.29.158254.3.29.15930
238254.3.29.160/27254.3.29.161 to 254.3.29.190254.3.29.19130
239254.3.29.192/27254.3.29.193 to 254.3.29.222254.3.29.22330
240254.3.29.224/27254.3.29.225 to 254.3.29.254254.3.29.25530
241254.3.30.0/27254.3.30.1 to 254.3.30.30254.3.30.3130
242254.3.30.32/27254.3.30.33 to 254.3.30.62254.3.30.6330
243254.3.30.64/27254.3.30.65 to 254.3.30.94254.3.30.9530
244254.3.30.96/27254.3.30.97 to 254.3.30.126254.3.30.12730
245254.3.30.128/27254.3.30.129 to 254.3.30.158254.3.30.15930
246254.3.30.160/27254.3.30.161 to 254.3.30.190254.3.30.19130
247254.3.30.192/27254.3.30.193 to 254.3.30.222254.3.30.22330
248254.3.30.224/27254.3.30.225 to 254.3.30.254254.3.30.25530
249254.3.31.0/27254.3.31.1 to 254.3.31.30254.3.31.3130
250254.3.31.32/27254.3.31.33 to 254.3.31.62254.3.31.6330
251254.3.31.64/27254.3.31.65 to 254.3.31.94254.3.31.9530
252254.3.31.96/27254.3.31.97 to 254.3.31.126254.3.31.12730
253254.3.31.128/27254.3.31.129 to 254.3.31.158254.3.31.15930
254254.3.31.160/27254.3.31.161 to 254.3.31.190254.3.31.19130
255254.3.31.192/27254.3.31.193 to 254.3.31.222254.3.31.22330
256254.3.31.224/27254.3.31.225 to 254.3.31.254254.3.31.25530

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.