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.

Network243.36.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
243.36.0.0
Broadcast address
243.36.127.255
First usable
243.36.0.1
Last usable
243.36.127.254
Usable hosts
32,766 (32,768 less the network and broadcast addresses)
Subnet mask
255.255.128.0
Wildcard mask
0.0.127.255 (Cisco ACLs, OSPF)
Prefix length
/17
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F3240000 · Integer 4079222784 to 4079255551
Reverse DNS zones
0.36.243.in-addr.arpa
1.36.243.in-addr.arpa
2.36.243.in-addr.arpa
3.36.243.in-addr.arpa
4.36.243.in-addr.arpa
5.36.243.in-addr.arpa
6.36.243.in-addr.arpa
7.36.243.in-addr.arpa
8.36.243.in-addr.arpa
9.36.243.in-addr.arpa
10.36.243.in-addr.arpa
11.36.243.in-addr.arpa
12.36.243.in-addr.arpa
13.36.243.in-addr.arpa
14.36.243.in-addr.arpa
15.36.243.in-addr.arpa
and 112 more
/17 is not on a 8-bit boundary, so it takes 128 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11110011.00100100.00000000.00000000243.36.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network11110011.00100100.00000000.00000000243.36.0.0
Broadcast11110011.00100100.01111111.11111111243.36.127.255
Split into smaller subnets/27
/18 (2)/19 (4)/20 (8)/21 (16)/22 (32)/23 (64)/24 (128)/25 (256)/26 (512)/27 (1,024)/28 (2,048)/29 (4,096)

243.36.0.0/17 makes 1,024 subnets of /27; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1243.36.0.0/27243.36.0.1 to 243.36.0.30243.36.0.3130
2243.36.0.32/27243.36.0.33 to 243.36.0.62243.36.0.6330
3243.36.0.64/27243.36.0.65 to 243.36.0.94243.36.0.9530
4243.36.0.96/27243.36.0.97 to 243.36.0.126243.36.0.12730
5243.36.0.128/27243.36.0.129 to 243.36.0.158243.36.0.15930
6243.36.0.160/27243.36.0.161 to 243.36.0.190243.36.0.19130
7243.36.0.192/27243.36.0.193 to 243.36.0.222243.36.0.22330
8243.36.0.224/27243.36.0.225 to 243.36.0.254243.36.0.25530
9243.36.1.0/27243.36.1.1 to 243.36.1.30243.36.1.3130
10243.36.1.32/27243.36.1.33 to 243.36.1.62243.36.1.6330
11243.36.1.64/27243.36.1.65 to 243.36.1.94243.36.1.9530
12243.36.1.96/27243.36.1.97 to 243.36.1.126243.36.1.12730
13243.36.1.128/27243.36.1.129 to 243.36.1.158243.36.1.15930
14243.36.1.160/27243.36.1.161 to 243.36.1.190243.36.1.19130
15243.36.1.192/27243.36.1.193 to 243.36.1.222243.36.1.22330
16243.36.1.224/27243.36.1.225 to 243.36.1.254243.36.1.25530
17243.36.2.0/27243.36.2.1 to 243.36.2.30243.36.2.3130
18243.36.2.32/27243.36.2.33 to 243.36.2.62243.36.2.6330
19243.36.2.64/27243.36.2.65 to 243.36.2.94243.36.2.9530
20243.36.2.96/27243.36.2.97 to 243.36.2.126243.36.2.12730
21243.36.2.128/27243.36.2.129 to 243.36.2.158243.36.2.15930
22243.36.2.160/27243.36.2.161 to 243.36.2.190243.36.2.19130
23243.36.2.192/27243.36.2.193 to 243.36.2.222243.36.2.22330
24243.36.2.224/27243.36.2.225 to 243.36.2.254243.36.2.25530
25243.36.3.0/27243.36.3.1 to 243.36.3.30243.36.3.3130
26243.36.3.32/27243.36.3.33 to 243.36.3.62243.36.3.6330
27243.36.3.64/27243.36.3.65 to 243.36.3.94243.36.3.9530
28243.36.3.96/27243.36.3.97 to 243.36.3.126243.36.3.12730
29243.36.3.128/27243.36.3.129 to 243.36.3.158243.36.3.15930
30243.36.3.160/27243.36.3.161 to 243.36.3.190243.36.3.19130
31243.36.3.192/27243.36.3.193 to 243.36.3.222243.36.3.22330
32243.36.3.224/27243.36.3.225 to 243.36.3.254243.36.3.25530
33243.36.4.0/27243.36.4.1 to 243.36.4.30243.36.4.3130
34243.36.4.32/27243.36.4.33 to 243.36.4.62243.36.4.6330
35243.36.4.64/27243.36.4.65 to 243.36.4.94243.36.4.9530
36243.36.4.96/27243.36.4.97 to 243.36.4.126243.36.4.12730
37243.36.4.128/27243.36.4.129 to 243.36.4.158243.36.4.15930
38243.36.4.160/27243.36.4.161 to 243.36.4.190243.36.4.19130
39243.36.4.192/27243.36.4.193 to 243.36.4.222243.36.4.22330
40243.36.4.224/27243.36.4.225 to 243.36.4.254243.36.4.25530
41243.36.5.0/27243.36.5.1 to 243.36.5.30243.36.5.3130
42243.36.5.32/27243.36.5.33 to 243.36.5.62243.36.5.6330
43243.36.5.64/27243.36.5.65 to 243.36.5.94243.36.5.9530
44243.36.5.96/27243.36.5.97 to 243.36.5.126243.36.5.12730
45243.36.5.128/27243.36.5.129 to 243.36.5.158243.36.5.15930
46243.36.5.160/27243.36.5.161 to 243.36.5.190243.36.5.19130
47243.36.5.192/27243.36.5.193 to 243.36.5.222243.36.5.22330
48243.36.5.224/27243.36.5.225 to 243.36.5.254243.36.5.25530
49243.36.6.0/27243.36.6.1 to 243.36.6.30243.36.6.3130
50243.36.6.32/27243.36.6.33 to 243.36.6.62243.36.6.6330
51243.36.6.64/27243.36.6.65 to 243.36.6.94243.36.6.9530
52243.36.6.96/27243.36.6.97 to 243.36.6.126243.36.6.12730
53243.36.6.128/27243.36.6.129 to 243.36.6.158243.36.6.15930
54243.36.6.160/27243.36.6.161 to 243.36.6.190243.36.6.19130
55243.36.6.192/27243.36.6.193 to 243.36.6.222243.36.6.22330
56243.36.6.224/27243.36.6.225 to 243.36.6.254243.36.6.25530
57243.36.7.0/27243.36.7.1 to 243.36.7.30243.36.7.3130
58243.36.7.32/27243.36.7.33 to 243.36.7.62243.36.7.6330
59243.36.7.64/27243.36.7.65 to 243.36.7.94243.36.7.9530
60243.36.7.96/27243.36.7.97 to 243.36.7.126243.36.7.12730
61243.36.7.128/27243.36.7.129 to 243.36.7.158243.36.7.15930
62243.36.7.160/27243.36.7.161 to 243.36.7.190243.36.7.19130
63243.36.7.192/27243.36.7.193 to 243.36.7.222243.36.7.22330
64243.36.7.224/27243.36.7.225 to 243.36.7.254243.36.7.25530
65243.36.8.0/27243.36.8.1 to 243.36.8.30243.36.8.3130
66243.36.8.32/27243.36.8.33 to 243.36.8.62243.36.8.6330
67243.36.8.64/27243.36.8.65 to 243.36.8.94243.36.8.9530
68243.36.8.96/27243.36.8.97 to 243.36.8.126243.36.8.12730
69243.36.8.128/27243.36.8.129 to 243.36.8.158243.36.8.15930
70243.36.8.160/27243.36.8.161 to 243.36.8.190243.36.8.19130
71243.36.8.192/27243.36.8.193 to 243.36.8.222243.36.8.22330
72243.36.8.224/27243.36.8.225 to 243.36.8.254243.36.8.25530
73243.36.9.0/27243.36.9.1 to 243.36.9.30243.36.9.3130
74243.36.9.32/27243.36.9.33 to 243.36.9.62243.36.9.6330
75243.36.9.64/27243.36.9.65 to 243.36.9.94243.36.9.9530
76243.36.9.96/27243.36.9.97 to 243.36.9.126243.36.9.12730
77243.36.9.128/27243.36.9.129 to 243.36.9.158243.36.9.15930
78243.36.9.160/27243.36.9.161 to 243.36.9.190243.36.9.19130
79243.36.9.192/27243.36.9.193 to 243.36.9.222243.36.9.22330
80243.36.9.224/27243.36.9.225 to 243.36.9.254243.36.9.25530
81243.36.10.0/27243.36.10.1 to 243.36.10.30243.36.10.3130
82243.36.10.32/27243.36.10.33 to 243.36.10.62243.36.10.6330
83243.36.10.64/27243.36.10.65 to 243.36.10.94243.36.10.9530
84243.36.10.96/27243.36.10.97 to 243.36.10.126243.36.10.12730
85243.36.10.128/27243.36.10.129 to 243.36.10.158243.36.10.15930
86243.36.10.160/27243.36.10.161 to 243.36.10.190243.36.10.19130
87243.36.10.192/27243.36.10.193 to 243.36.10.222243.36.10.22330
88243.36.10.224/27243.36.10.225 to 243.36.10.254243.36.10.25530
89243.36.11.0/27243.36.11.1 to 243.36.11.30243.36.11.3130
90243.36.11.32/27243.36.11.33 to 243.36.11.62243.36.11.6330
91243.36.11.64/27243.36.11.65 to 243.36.11.94243.36.11.9530
92243.36.11.96/27243.36.11.97 to 243.36.11.126243.36.11.12730
93243.36.11.128/27243.36.11.129 to 243.36.11.158243.36.11.15930
94243.36.11.160/27243.36.11.161 to 243.36.11.190243.36.11.19130
95243.36.11.192/27243.36.11.193 to 243.36.11.222243.36.11.22330
96243.36.11.224/27243.36.11.225 to 243.36.11.254243.36.11.25530
97243.36.12.0/27243.36.12.1 to 243.36.12.30243.36.12.3130
98243.36.12.32/27243.36.12.33 to 243.36.12.62243.36.12.6330
99243.36.12.64/27243.36.12.65 to 243.36.12.94243.36.12.9530
100243.36.12.96/27243.36.12.97 to 243.36.12.126243.36.12.12730
101243.36.12.128/27243.36.12.129 to 243.36.12.158243.36.12.15930
102243.36.12.160/27243.36.12.161 to 243.36.12.190243.36.12.19130
103243.36.12.192/27243.36.12.193 to 243.36.12.222243.36.12.22330
104243.36.12.224/27243.36.12.225 to 243.36.12.254243.36.12.25530
105243.36.13.0/27243.36.13.1 to 243.36.13.30243.36.13.3130
106243.36.13.32/27243.36.13.33 to 243.36.13.62243.36.13.6330
107243.36.13.64/27243.36.13.65 to 243.36.13.94243.36.13.9530
108243.36.13.96/27243.36.13.97 to 243.36.13.126243.36.13.12730
109243.36.13.128/27243.36.13.129 to 243.36.13.158243.36.13.15930
110243.36.13.160/27243.36.13.161 to 243.36.13.190243.36.13.19130
111243.36.13.192/27243.36.13.193 to 243.36.13.222243.36.13.22330
112243.36.13.224/27243.36.13.225 to 243.36.13.254243.36.13.25530
113243.36.14.0/27243.36.14.1 to 243.36.14.30243.36.14.3130
114243.36.14.32/27243.36.14.33 to 243.36.14.62243.36.14.6330
115243.36.14.64/27243.36.14.65 to 243.36.14.94243.36.14.9530
116243.36.14.96/27243.36.14.97 to 243.36.14.126243.36.14.12730
117243.36.14.128/27243.36.14.129 to 243.36.14.158243.36.14.15930
118243.36.14.160/27243.36.14.161 to 243.36.14.190243.36.14.19130
119243.36.14.192/27243.36.14.193 to 243.36.14.222243.36.14.22330
120243.36.14.224/27243.36.14.225 to 243.36.14.254243.36.14.25530
121243.36.15.0/27243.36.15.1 to 243.36.15.30243.36.15.3130
122243.36.15.32/27243.36.15.33 to 243.36.15.62243.36.15.6330
123243.36.15.64/27243.36.15.65 to 243.36.15.94243.36.15.9530
124243.36.15.96/27243.36.15.97 to 243.36.15.126243.36.15.12730
125243.36.15.128/27243.36.15.129 to 243.36.15.158243.36.15.15930
126243.36.15.160/27243.36.15.161 to 243.36.15.190243.36.15.19130
127243.36.15.192/27243.36.15.193 to 243.36.15.222243.36.15.22330
128243.36.15.224/27243.36.15.225 to 243.36.15.254243.36.15.25530
129243.36.16.0/27243.36.16.1 to 243.36.16.30243.36.16.3130
130243.36.16.32/27243.36.16.33 to 243.36.16.62243.36.16.6330
131243.36.16.64/27243.36.16.65 to 243.36.16.94243.36.16.9530
132243.36.16.96/27243.36.16.97 to 243.36.16.126243.36.16.12730
133243.36.16.128/27243.36.16.129 to 243.36.16.158243.36.16.15930
134243.36.16.160/27243.36.16.161 to 243.36.16.190243.36.16.19130
135243.36.16.192/27243.36.16.193 to 243.36.16.222243.36.16.22330
136243.36.16.224/27243.36.16.225 to 243.36.16.254243.36.16.25530
137243.36.17.0/27243.36.17.1 to 243.36.17.30243.36.17.3130
138243.36.17.32/27243.36.17.33 to 243.36.17.62243.36.17.6330
139243.36.17.64/27243.36.17.65 to 243.36.17.94243.36.17.9530
140243.36.17.96/27243.36.17.97 to 243.36.17.126243.36.17.12730
141243.36.17.128/27243.36.17.129 to 243.36.17.158243.36.17.15930
142243.36.17.160/27243.36.17.161 to 243.36.17.190243.36.17.19130
143243.36.17.192/27243.36.17.193 to 243.36.17.222243.36.17.22330
144243.36.17.224/27243.36.17.225 to 243.36.17.254243.36.17.25530
145243.36.18.0/27243.36.18.1 to 243.36.18.30243.36.18.3130
146243.36.18.32/27243.36.18.33 to 243.36.18.62243.36.18.6330
147243.36.18.64/27243.36.18.65 to 243.36.18.94243.36.18.9530
148243.36.18.96/27243.36.18.97 to 243.36.18.126243.36.18.12730
149243.36.18.128/27243.36.18.129 to 243.36.18.158243.36.18.15930
150243.36.18.160/27243.36.18.161 to 243.36.18.190243.36.18.19130
151243.36.18.192/27243.36.18.193 to 243.36.18.222243.36.18.22330
152243.36.18.224/27243.36.18.225 to 243.36.18.254243.36.18.25530
153243.36.19.0/27243.36.19.1 to 243.36.19.30243.36.19.3130
154243.36.19.32/27243.36.19.33 to 243.36.19.62243.36.19.6330
155243.36.19.64/27243.36.19.65 to 243.36.19.94243.36.19.9530
156243.36.19.96/27243.36.19.97 to 243.36.19.126243.36.19.12730
157243.36.19.128/27243.36.19.129 to 243.36.19.158243.36.19.15930
158243.36.19.160/27243.36.19.161 to 243.36.19.190243.36.19.19130
159243.36.19.192/27243.36.19.193 to 243.36.19.222243.36.19.22330
160243.36.19.224/27243.36.19.225 to 243.36.19.254243.36.19.25530
161243.36.20.0/27243.36.20.1 to 243.36.20.30243.36.20.3130
162243.36.20.32/27243.36.20.33 to 243.36.20.62243.36.20.6330
163243.36.20.64/27243.36.20.65 to 243.36.20.94243.36.20.9530
164243.36.20.96/27243.36.20.97 to 243.36.20.126243.36.20.12730
165243.36.20.128/27243.36.20.129 to 243.36.20.158243.36.20.15930
166243.36.20.160/27243.36.20.161 to 243.36.20.190243.36.20.19130
167243.36.20.192/27243.36.20.193 to 243.36.20.222243.36.20.22330
168243.36.20.224/27243.36.20.225 to 243.36.20.254243.36.20.25530
169243.36.21.0/27243.36.21.1 to 243.36.21.30243.36.21.3130
170243.36.21.32/27243.36.21.33 to 243.36.21.62243.36.21.6330
171243.36.21.64/27243.36.21.65 to 243.36.21.94243.36.21.9530
172243.36.21.96/27243.36.21.97 to 243.36.21.126243.36.21.12730
173243.36.21.128/27243.36.21.129 to 243.36.21.158243.36.21.15930
174243.36.21.160/27243.36.21.161 to 243.36.21.190243.36.21.19130
175243.36.21.192/27243.36.21.193 to 243.36.21.222243.36.21.22330
176243.36.21.224/27243.36.21.225 to 243.36.21.254243.36.21.25530
177243.36.22.0/27243.36.22.1 to 243.36.22.30243.36.22.3130
178243.36.22.32/27243.36.22.33 to 243.36.22.62243.36.22.6330
179243.36.22.64/27243.36.22.65 to 243.36.22.94243.36.22.9530
180243.36.22.96/27243.36.22.97 to 243.36.22.126243.36.22.12730
181243.36.22.128/27243.36.22.129 to 243.36.22.158243.36.22.15930
182243.36.22.160/27243.36.22.161 to 243.36.22.190243.36.22.19130
183243.36.22.192/27243.36.22.193 to 243.36.22.222243.36.22.22330
184243.36.22.224/27243.36.22.225 to 243.36.22.254243.36.22.25530
185243.36.23.0/27243.36.23.1 to 243.36.23.30243.36.23.3130
186243.36.23.32/27243.36.23.33 to 243.36.23.62243.36.23.6330
187243.36.23.64/27243.36.23.65 to 243.36.23.94243.36.23.9530
188243.36.23.96/27243.36.23.97 to 243.36.23.126243.36.23.12730
189243.36.23.128/27243.36.23.129 to 243.36.23.158243.36.23.15930
190243.36.23.160/27243.36.23.161 to 243.36.23.190243.36.23.19130
191243.36.23.192/27243.36.23.193 to 243.36.23.222243.36.23.22330
192243.36.23.224/27243.36.23.225 to 243.36.23.254243.36.23.25530
193243.36.24.0/27243.36.24.1 to 243.36.24.30243.36.24.3130
194243.36.24.32/27243.36.24.33 to 243.36.24.62243.36.24.6330
195243.36.24.64/27243.36.24.65 to 243.36.24.94243.36.24.9530
196243.36.24.96/27243.36.24.97 to 243.36.24.126243.36.24.12730
197243.36.24.128/27243.36.24.129 to 243.36.24.158243.36.24.15930
198243.36.24.160/27243.36.24.161 to 243.36.24.190243.36.24.19130
199243.36.24.192/27243.36.24.193 to 243.36.24.222243.36.24.22330
200243.36.24.224/27243.36.24.225 to 243.36.24.254243.36.24.25530
201243.36.25.0/27243.36.25.1 to 243.36.25.30243.36.25.3130
202243.36.25.32/27243.36.25.33 to 243.36.25.62243.36.25.6330
203243.36.25.64/27243.36.25.65 to 243.36.25.94243.36.25.9530
204243.36.25.96/27243.36.25.97 to 243.36.25.126243.36.25.12730
205243.36.25.128/27243.36.25.129 to 243.36.25.158243.36.25.15930
206243.36.25.160/27243.36.25.161 to 243.36.25.190243.36.25.19130
207243.36.25.192/27243.36.25.193 to 243.36.25.222243.36.25.22330
208243.36.25.224/27243.36.25.225 to 243.36.25.254243.36.25.25530
209243.36.26.0/27243.36.26.1 to 243.36.26.30243.36.26.3130
210243.36.26.32/27243.36.26.33 to 243.36.26.62243.36.26.6330
211243.36.26.64/27243.36.26.65 to 243.36.26.94243.36.26.9530
212243.36.26.96/27243.36.26.97 to 243.36.26.126243.36.26.12730
213243.36.26.128/27243.36.26.129 to 243.36.26.158243.36.26.15930
214243.36.26.160/27243.36.26.161 to 243.36.26.190243.36.26.19130
215243.36.26.192/27243.36.26.193 to 243.36.26.222243.36.26.22330
216243.36.26.224/27243.36.26.225 to 243.36.26.254243.36.26.25530
217243.36.27.0/27243.36.27.1 to 243.36.27.30243.36.27.3130
218243.36.27.32/27243.36.27.33 to 243.36.27.62243.36.27.6330
219243.36.27.64/27243.36.27.65 to 243.36.27.94243.36.27.9530
220243.36.27.96/27243.36.27.97 to 243.36.27.126243.36.27.12730
221243.36.27.128/27243.36.27.129 to 243.36.27.158243.36.27.15930
222243.36.27.160/27243.36.27.161 to 243.36.27.190243.36.27.19130
223243.36.27.192/27243.36.27.193 to 243.36.27.222243.36.27.22330
224243.36.27.224/27243.36.27.225 to 243.36.27.254243.36.27.25530
225243.36.28.0/27243.36.28.1 to 243.36.28.30243.36.28.3130
226243.36.28.32/27243.36.28.33 to 243.36.28.62243.36.28.6330
227243.36.28.64/27243.36.28.65 to 243.36.28.94243.36.28.9530
228243.36.28.96/27243.36.28.97 to 243.36.28.126243.36.28.12730
229243.36.28.128/27243.36.28.129 to 243.36.28.158243.36.28.15930
230243.36.28.160/27243.36.28.161 to 243.36.28.190243.36.28.19130
231243.36.28.192/27243.36.28.193 to 243.36.28.222243.36.28.22330
232243.36.28.224/27243.36.28.225 to 243.36.28.254243.36.28.25530
233243.36.29.0/27243.36.29.1 to 243.36.29.30243.36.29.3130
234243.36.29.32/27243.36.29.33 to 243.36.29.62243.36.29.6330
235243.36.29.64/27243.36.29.65 to 243.36.29.94243.36.29.9530
236243.36.29.96/27243.36.29.97 to 243.36.29.126243.36.29.12730
237243.36.29.128/27243.36.29.129 to 243.36.29.158243.36.29.15930
238243.36.29.160/27243.36.29.161 to 243.36.29.190243.36.29.19130
239243.36.29.192/27243.36.29.193 to 243.36.29.222243.36.29.22330
240243.36.29.224/27243.36.29.225 to 243.36.29.254243.36.29.25530
241243.36.30.0/27243.36.30.1 to 243.36.30.30243.36.30.3130
242243.36.30.32/27243.36.30.33 to 243.36.30.62243.36.30.6330
243243.36.30.64/27243.36.30.65 to 243.36.30.94243.36.30.9530
244243.36.30.96/27243.36.30.97 to 243.36.30.126243.36.30.12730
245243.36.30.128/27243.36.30.129 to 243.36.30.158243.36.30.15930
246243.36.30.160/27243.36.30.161 to 243.36.30.190243.36.30.19130
247243.36.30.192/27243.36.30.193 to 243.36.30.222243.36.30.22330
248243.36.30.224/27243.36.30.225 to 243.36.30.254243.36.30.25530
249243.36.31.0/27243.36.31.1 to 243.36.31.30243.36.31.3130
250243.36.31.32/27243.36.31.33 to 243.36.31.62243.36.31.6330
251243.36.31.64/27243.36.31.65 to 243.36.31.94243.36.31.9530
252243.36.31.96/27243.36.31.97 to 243.36.31.126243.36.31.12730
253243.36.31.128/27243.36.31.129 to 243.36.31.158243.36.31.15930
254243.36.31.160/27243.36.31.161 to 243.36.31.190243.36.31.19130
255243.36.31.192/27243.36.31.193 to 243.36.31.222243.36.31.22330
256243.36.31.224/27243.36.31.225 to 243.36.31.254243.36.31.25530

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.