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.

Network191.26.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
191.26.0.0
Broadcast address
191.26.127.255
First usable
191.26.0.1
Last usable
191.26.127.254
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
Public public
Old class
B (default /16)
As numbers
Hex BF1A0000 · Integer 3206152192 to 3206184959
Reverse DNS zones
0.26.191.in-addr.arpa
1.26.191.in-addr.arpa
2.26.191.in-addr.arpa
3.26.191.in-addr.arpa
4.26.191.in-addr.arpa
5.26.191.in-addr.arpa
6.26.191.in-addr.arpa
7.26.191.in-addr.arpa
8.26.191.in-addr.arpa
9.26.191.in-addr.arpa
10.26.191.in-addr.arpa
11.26.191.in-addr.arpa
12.26.191.in-addr.arpa
13.26.191.in-addr.arpa
14.26.191.in-addr.arpa
15.26.191.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
Address10111111.00011010.00000000.00000000191.26.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network10111111.00011010.00000000.00000000191.26.0.0
Broadcast10111111.00011010.01111111.11111111191.26.127.255
Split into smaller subnets/28
/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)

191.26.0.0/17 makes 2,048 subnets of /28; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1191.26.0.0/28191.26.0.1 to 191.26.0.14191.26.0.1514
2191.26.0.16/28191.26.0.17 to 191.26.0.30191.26.0.3114
3191.26.0.32/28191.26.0.33 to 191.26.0.46191.26.0.4714
4191.26.0.48/28191.26.0.49 to 191.26.0.62191.26.0.6314
5191.26.0.64/28191.26.0.65 to 191.26.0.78191.26.0.7914
6191.26.0.80/28191.26.0.81 to 191.26.0.94191.26.0.9514
7191.26.0.96/28191.26.0.97 to 191.26.0.110191.26.0.11114
8191.26.0.112/28191.26.0.113 to 191.26.0.126191.26.0.12714
9191.26.0.128/28191.26.0.129 to 191.26.0.142191.26.0.14314
10191.26.0.144/28191.26.0.145 to 191.26.0.158191.26.0.15914
11191.26.0.160/28191.26.0.161 to 191.26.0.174191.26.0.17514
12191.26.0.176/28191.26.0.177 to 191.26.0.190191.26.0.19114
13191.26.0.192/28191.26.0.193 to 191.26.0.206191.26.0.20714
14191.26.0.208/28191.26.0.209 to 191.26.0.222191.26.0.22314
15191.26.0.224/28191.26.0.225 to 191.26.0.238191.26.0.23914
16191.26.0.240/28191.26.0.241 to 191.26.0.254191.26.0.25514
17191.26.1.0/28191.26.1.1 to 191.26.1.14191.26.1.1514
18191.26.1.16/28191.26.1.17 to 191.26.1.30191.26.1.3114
19191.26.1.32/28191.26.1.33 to 191.26.1.46191.26.1.4714
20191.26.1.48/28191.26.1.49 to 191.26.1.62191.26.1.6314
21191.26.1.64/28191.26.1.65 to 191.26.1.78191.26.1.7914
22191.26.1.80/28191.26.1.81 to 191.26.1.94191.26.1.9514
23191.26.1.96/28191.26.1.97 to 191.26.1.110191.26.1.11114
24191.26.1.112/28191.26.1.113 to 191.26.1.126191.26.1.12714
25191.26.1.128/28191.26.1.129 to 191.26.1.142191.26.1.14314
26191.26.1.144/28191.26.1.145 to 191.26.1.158191.26.1.15914
27191.26.1.160/28191.26.1.161 to 191.26.1.174191.26.1.17514
28191.26.1.176/28191.26.1.177 to 191.26.1.190191.26.1.19114
29191.26.1.192/28191.26.1.193 to 191.26.1.206191.26.1.20714
30191.26.1.208/28191.26.1.209 to 191.26.1.222191.26.1.22314
31191.26.1.224/28191.26.1.225 to 191.26.1.238191.26.1.23914
32191.26.1.240/28191.26.1.241 to 191.26.1.254191.26.1.25514
33191.26.2.0/28191.26.2.1 to 191.26.2.14191.26.2.1514
34191.26.2.16/28191.26.2.17 to 191.26.2.30191.26.2.3114
35191.26.2.32/28191.26.2.33 to 191.26.2.46191.26.2.4714
36191.26.2.48/28191.26.2.49 to 191.26.2.62191.26.2.6314
37191.26.2.64/28191.26.2.65 to 191.26.2.78191.26.2.7914
38191.26.2.80/28191.26.2.81 to 191.26.2.94191.26.2.9514
39191.26.2.96/28191.26.2.97 to 191.26.2.110191.26.2.11114
40191.26.2.112/28191.26.2.113 to 191.26.2.126191.26.2.12714
41191.26.2.128/28191.26.2.129 to 191.26.2.142191.26.2.14314
42191.26.2.144/28191.26.2.145 to 191.26.2.158191.26.2.15914
43191.26.2.160/28191.26.2.161 to 191.26.2.174191.26.2.17514
44191.26.2.176/28191.26.2.177 to 191.26.2.190191.26.2.19114
45191.26.2.192/28191.26.2.193 to 191.26.2.206191.26.2.20714
46191.26.2.208/28191.26.2.209 to 191.26.2.222191.26.2.22314
47191.26.2.224/28191.26.2.225 to 191.26.2.238191.26.2.23914
48191.26.2.240/28191.26.2.241 to 191.26.2.254191.26.2.25514
49191.26.3.0/28191.26.3.1 to 191.26.3.14191.26.3.1514
50191.26.3.16/28191.26.3.17 to 191.26.3.30191.26.3.3114
51191.26.3.32/28191.26.3.33 to 191.26.3.46191.26.3.4714
52191.26.3.48/28191.26.3.49 to 191.26.3.62191.26.3.6314
53191.26.3.64/28191.26.3.65 to 191.26.3.78191.26.3.7914
54191.26.3.80/28191.26.3.81 to 191.26.3.94191.26.3.9514
55191.26.3.96/28191.26.3.97 to 191.26.3.110191.26.3.11114
56191.26.3.112/28191.26.3.113 to 191.26.3.126191.26.3.12714
57191.26.3.128/28191.26.3.129 to 191.26.3.142191.26.3.14314
58191.26.3.144/28191.26.3.145 to 191.26.3.158191.26.3.15914
59191.26.3.160/28191.26.3.161 to 191.26.3.174191.26.3.17514
60191.26.3.176/28191.26.3.177 to 191.26.3.190191.26.3.19114
61191.26.3.192/28191.26.3.193 to 191.26.3.206191.26.3.20714
62191.26.3.208/28191.26.3.209 to 191.26.3.222191.26.3.22314
63191.26.3.224/28191.26.3.225 to 191.26.3.238191.26.3.23914
64191.26.3.240/28191.26.3.241 to 191.26.3.254191.26.3.25514
65191.26.4.0/28191.26.4.1 to 191.26.4.14191.26.4.1514
66191.26.4.16/28191.26.4.17 to 191.26.4.30191.26.4.3114
67191.26.4.32/28191.26.4.33 to 191.26.4.46191.26.4.4714
68191.26.4.48/28191.26.4.49 to 191.26.4.62191.26.4.6314
69191.26.4.64/28191.26.4.65 to 191.26.4.78191.26.4.7914
70191.26.4.80/28191.26.4.81 to 191.26.4.94191.26.4.9514
71191.26.4.96/28191.26.4.97 to 191.26.4.110191.26.4.11114
72191.26.4.112/28191.26.4.113 to 191.26.4.126191.26.4.12714
73191.26.4.128/28191.26.4.129 to 191.26.4.142191.26.4.14314
74191.26.4.144/28191.26.4.145 to 191.26.4.158191.26.4.15914
75191.26.4.160/28191.26.4.161 to 191.26.4.174191.26.4.17514
76191.26.4.176/28191.26.4.177 to 191.26.4.190191.26.4.19114
77191.26.4.192/28191.26.4.193 to 191.26.4.206191.26.4.20714
78191.26.4.208/28191.26.4.209 to 191.26.4.222191.26.4.22314
79191.26.4.224/28191.26.4.225 to 191.26.4.238191.26.4.23914
80191.26.4.240/28191.26.4.241 to 191.26.4.254191.26.4.25514
81191.26.5.0/28191.26.5.1 to 191.26.5.14191.26.5.1514
82191.26.5.16/28191.26.5.17 to 191.26.5.30191.26.5.3114
83191.26.5.32/28191.26.5.33 to 191.26.5.46191.26.5.4714
84191.26.5.48/28191.26.5.49 to 191.26.5.62191.26.5.6314
85191.26.5.64/28191.26.5.65 to 191.26.5.78191.26.5.7914
86191.26.5.80/28191.26.5.81 to 191.26.5.94191.26.5.9514
87191.26.5.96/28191.26.5.97 to 191.26.5.110191.26.5.11114
88191.26.5.112/28191.26.5.113 to 191.26.5.126191.26.5.12714
89191.26.5.128/28191.26.5.129 to 191.26.5.142191.26.5.14314
90191.26.5.144/28191.26.5.145 to 191.26.5.158191.26.5.15914
91191.26.5.160/28191.26.5.161 to 191.26.5.174191.26.5.17514
92191.26.5.176/28191.26.5.177 to 191.26.5.190191.26.5.19114
93191.26.5.192/28191.26.5.193 to 191.26.5.206191.26.5.20714
94191.26.5.208/28191.26.5.209 to 191.26.5.222191.26.5.22314
95191.26.5.224/28191.26.5.225 to 191.26.5.238191.26.5.23914
96191.26.5.240/28191.26.5.241 to 191.26.5.254191.26.5.25514
97191.26.6.0/28191.26.6.1 to 191.26.6.14191.26.6.1514
98191.26.6.16/28191.26.6.17 to 191.26.6.30191.26.6.3114
99191.26.6.32/28191.26.6.33 to 191.26.6.46191.26.6.4714
100191.26.6.48/28191.26.6.49 to 191.26.6.62191.26.6.6314
101191.26.6.64/28191.26.6.65 to 191.26.6.78191.26.6.7914
102191.26.6.80/28191.26.6.81 to 191.26.6.94191.26.6.9514
103191.26.6.96/28191.26.6.97 to 191.26.6.110191.26.6.11114
104191.26.6.112/28191.26.6.113 to 191.26.6.126191.26.6.12714
105191.26.6.128/28191.26.6.129 to 191.26.6.142191.26.6.14314
106191.26.6.144/28191.26.6.145 to 191.26.6.158191.26.6.15914
107191.26.6.160/28191.26.6.161 to 191.26.6.174191.26.6.17514
108191.26.6.176/28191.26.6.177 to 191.26.6.190191.26.6.19114
109191.26.6.192/28191.26.6.193 to 191.26.6.206191.26.6.20714
110191.26.6.208/28191.26.6.209 to 191.26.6.222191.26.6.22314
111191.26.6.224/28191.26.6.225 to 191.26.6.238191.26.6.23914
112191.26.6.240/28191.26.6.241 to 191.26.6.254191.26.6.25514
113191.26.7.0/28191.26.7.1 to 191.26.7.14191.26.7.1514
114191.26.7.16/28191.26.7.17 to 191.26.7.30191.26.7.3114
115191.26.7.32/28191.26.7.33 to 191.26.7.46191.26.7.4714
116191.26.7.48/28191.26.7.49 to 191.26.7.62191.26.7.6314
117191.26.7.64/28191.26.7.65 to 191.26.7.78191.26.7.7914
118191.26.7.80/28191.26.7.81 to 191.26.7.94191.26.7.9514
119191.26.7.96/28191.26.7.97 to 191.26.7.110191.26.7.11114
120191.26.7.112/28191.26.7.113 to 191.26.7.126191.26.7.12714
121191.26.7.128/28191.26.7.129 to 191.26.7.142191.26.7.14314
122191.26.7.144/28191.26.7.145 to 191.26.7.158191.26.7.15914
123191.26.7.160/28191.26.7.161 to 191.26.7.174191.26.7.17514
124191.26.7.176/28191.26.7.177 to 191.26.7.190191.26.7.19114
125191.26.7.192/28191.26.7.193 to 191.26.7.206191.26.7.20714
126191.26.7.208/28191.26.7.209 to 191.26.7.222191.26.7.22314
127191.26.7.224/28191.26.7.225 to 191.26.7.238191.26.7.23914
128191.26.7.240/28191.26.7.241 to 191.26.7.254191.26.7.25514
129191.26.8.0/28191.26.8.1 to 191.26.8.14191.26.8.1514
130191.26.8.16/28191.26.8.17 to 191.26.8.30191.26.8.3114
131191.26.8.32/28191.26.8.33 to 191.26.8.46191.26.8.4714
132191.26.8.48/28191.26.8.49 to 191.26.8.62191.26.8.6314
133191.26.8.64/28191.26.8.65 to 191.26.8.78191.26.8.7914
134191.26.8.80/28191.26.8.81 to 191.26.8.94191.26.8.9514
135191.26.8.96/28191.26.8.97 to 191.26.8.110191.26.8.11114
136191.26.8.112/28191.26.8.113 to 191.26.8.126191.26.8.12714
137191.26.8.128/28191.26.8.129 to 191.26.8.142191.26.8.14314
138191.26.8.144/28191.26.8.145 to 191.26.8.158191.26.8.15914
139191.26.8.160/28191.26.8.161 to 191.26.8.174191.26.8.17514
140191.26.8.176/28191.26.8.177 to 191.26.8.190191.26.8.19114
141191.26.8.192/28191.26.8.193 to 191.26.8.206191.26.8.20714
142191.26.8.208/28191.26.8.209 to 191.26.8.222191.26.8.22314
143191.26.8.224/28191.26.8.225 to 191.26.8.238191.26.8.23914
144191.26.8.240/28191.26.8.241 to 191.26.8.254191.26.8.25514
145191.26.9.0/28191.26.9.1 to 191.26.9.14191.26.9.1514
146191.26.9.16/28191.26.9.17 to 191.26.9.30191.26.9.3114
147191.26.9.32/28191.26.9.33 to 191.26.9.46191.26.9.4714
148191.26.9.48/28191.26.9.49 to 191.26.9.62191.26.9.6314
149191.26.9.64/28191.26.9.65 to 191.26.9.78191.26.9.7914
150191.26.9.80/28191.26.9.81 to 191.26.9.94191.26.9.9514
151191.26.9.96/28191.26.9.97 to 191.26.9.110191.26.9.11114
152191.26.9.112/28191.26.9.113 to 191.26.9.126191.26.9.12714
153191.26.9.128/28191.26.9.129 to 191.26.9.142191.26.9.14314
154191.26.9.144/28191.26.9.145 to 191.26.9.158191.26.9.15914
155191.26.9.160/28191.26.9.161 to 191.26.9.174191.26.9.17514
156191.26.9.176/28191.26.9.177 to 191.26.9.190191.26.9.19114
157191.26.9.192/28191.26.9.193 to 191.26.9.206191.26.9.20714
158191.26.9.208/28191.26.9.209 to 191.26.9.222191.26.9.22314
159191.26.9.224/28191.26.9.225 to 191.26.9.238191.26.9.23914
160191.26.9.240/28191.26.9.241 to 191.26.9.254191.26.9.25514
161191.26.10.0/28191.26.10.1 to 191.26.10.14191.26.10.1514
162191.26.10.16/28191.26.10.17 to 191.26.10.30191.26.10.3114
163191.26.10.32/28191.26.10.33 to 191.26.10.46191.26.10.4714
164191.26.10.48/28191.26.10.49 to 191.26.10.62191.26.10.6314
165191.26.10.64/28191.26.10.65 to 191.26.10.78191.26.10.7914
166191.26.10.80/28191.26.10.81 to 191.26.10.94191.26.10.9514
167191.26.10.96/28191.26.10.97 to 191.26.10.110191.26.10.11114
168191.26.10.112/28191.26.10.113 to 191.26.10.126191.26.10.12714
169191.26.10.128/28191.26.10.129 to 191.26.10.142191.26.10.14314
170191.26.10.144/28191.26.10.145 to 191.26.10.158191.26.10.15914
171191.26.10.160/28191.26.10.161 to 191.26.10.174191.26.10.17514
172191.26.10.176/28191.26.10.177 to 191.26.10.190191.26.10.19114
173191.26.10.192/28191.26.10.193 to 191.26.10.206191.26.10.20714
174191.26.10.208/28191.26.10.209 to 191.26.10.222191.26.10.22314
175191.26.10.224/28191.26.10.225 to 191.26.10.238191.26.10.23914
176191.26.10.240/28191.26.10.241 to 191.26.10.254191.26.10.25514
177191.26.11.0/28191.26.11.1 to 191.26.11.14191.26.11.1514
178191.26.11.16/28191.26.11.17 to 191.26.11.30191.26.11.3114
179191.26.11.32/28191.26.11.33 to 191.26.11.46191.26.11.4714
180191.26.11.48/28191.26.11.49 to 191.26.11.62191.26.11.6314
181191.26.11.64/28191.26.11.65 to 191.26.11.78191.26.11.7914
182191.26.11.80/28191.26.11.81 to 191.26.11.94191.26.11.9514
183191.26.11.96/28191.26.11.97 to 191.26.11.110191.26.11.11114
184191.26.11.112/28191.26.11.113 to 191.26.11.126191.26.11.12714
185191.26.11.128/28191.26.11.129 to 191.26.11.142191.26.11.14314
186191.26.11.144/28191.26.11.145 to 191.26.11.158191.26.11.15914
187191.26.11.160/28191.26.11.161 to 191.26.11.174191.26.11.17514
188191.26.11.176/28191.26.11.177 to 191.26.11.190191.26.11.19114
189191.26.11.192/28191.26.11.193 to 191.26.11.206191.26.11.20714
190191.26.11.208/28191.26.11.209 to 191.26.11.222191.26.11.22314
191191.26.11.224/28191.26.11.225 to 191.26.11.238191.26.11.23914
192191.26.11.240/28191.26.11.241 to 191.26.11.254191.26.11.25514
193191.26.12.0/28191.26.12.1 to 191.26.12.14191.26.12.1514
194191.26.12.16/28191.26.12.17 to 191.26.12.30191.26.12.3114
195191.26.12.32/28191.26.12.33 to 191.26.12.46191.26.12.4714
196191.26.12.48/28191.26.12.49 to 191.26.12.62191.26.12.6314
197191.26.12.64/28191.26.12.65 to 191.26.12.78191.26.12.7914
198191.26.12.80/28191.26.12.81 to 191.26.12.94191.26.12.9514
199191.26.12.96/28191.26.12.97 to 191.26.12.110191.26.12.11114
200191.26.12.112/28191.26.12.113 to 191.26.12.126191.26.12.12714
201191.26.12.128/28191.26.12.129 to 191.26.12.142191.26.12.14314
202191.26.12.144/28191.26.12.145 to 191.26.12.158191.26.12.15914
203191.26.12.160/28191.26.12.161 to 191.26.12.174191.26.12.17514
204191.26.12.176/28191.26.12.177 to 191.26.12.190191.26.12.19114
205191.26.12.192/28191.26.12.193 to 191.26.12.206191.26.12.20714
206191.26.12.208/28191.26.12.209 to 191.26.12.222191.26.12.22314
207191.26.12.224/28191.26.12.225 to 191.26.12.238191.26.12.23914
208191.26.12.240/28191.26.12.241 to 191.26.12.254191.26.12.25514
209191.26.13.0/28191.26.13.1 to 191.26.13.14191.26.13.1514
210191.26.13.16/28191.26.13.17 to 191.26.13.30191.26.13.3114
211191.26.13.32/28191.26.13.33 to 191.26.13.46191.26.13.4714
212191.26.13.48/28191.26.13.49 to 191.26.13.62191.26.13.6314
213191.26.13.64/28191.26.13.65 to 191.26.13.78191.26.13.7914
214191.26.13.80/28191.26.13.81 to 191.26.13.94191.26.13.9514
215191.26.13.96/28191.26.13.97 to 191.26.13.110191.26.13.11114
216191.26.13.112/28191.26.13.113 to 191.26.13.126191.26.13.12714
217191.26.13.128/28191.26.13.129 to 191.26.13.142191.26.13.14314
218191.26.13.144/28191.26.13.145 to 191.26.13.158191.26.13.15914
219191.26.13.160/28191.26.13.161 to 191.26.13.174191.26.13.17514
220191.26.13.176/28191.26.13.177 to 191.26.13.190191.26.13.19114
221191.26.13.192/28191.26.13.193 to 191.26.13.206191.26.13.20714
222191.26.13.208/28191.26.13.209 to 191.26.13.222191.26.13.22314
223191.26.13.224/28191.26.13.225 to 191.26.13.238191.26.13.23914
224191.26.13.240/28191.26.13.241 to 191.26.13.254191.26.13.25514
225191.26.14.0/28191.26.14.1 to 191.26.14.14191.26.14.1514
226191.26.14.16/28191.26.14.17 to 191.26.14.30191.26.14.3114
227191.26.14.32/28191.26.14.33 to 191.26.14.46191.26.14.4714
228191.26.14.48/28191.26.14.49 to 191.26.14.62191.26.14.6314
229191.26.14.64/28191.26.14.65 to 191.26.14.78191.26.14.7914
230191.26.14.80/28191.26.14.81 to 191.26.14.94191.26.14.9514
231191.26.14.96/28191.26.14.97 to 191.26.14.110191.26.14.11114
232191.26.14.112/28191.26.14.113 to 191.26.14.126191.26.14.12714
233191.26.14.128/28191.26.14.129 to 191.26.14.142191.26.14.14314
234191.26.14.144/28191.26.14.145 to 191.26.14.158191.26.14.15914
235191.26.14.160/28191.26.14.161 to 191.26.14.174191.26.14.17514
236191.26.14.176/28191.26.14.177 to 191.26.14.190191.26.14.19114
237191.26.14.192/28191.26.14.193 to 191.26.14.206191.26.14.20714
238191.26.14.208/28191.26.14.209 to 191.26.14.222191.26.14.22314
239191.26.14.224/28191.26.14.225 to 191.26.14.238191.26.14.23914
240191.26.14.240/28191.26.14.241 to 191.26.14.254191.26.14.25514
241191.26.15.0/28191.26.15.1 to 191.26.15.14191.26.15.1514
242191.26.15.16/28191.26.15.17 to 191.26.15.30191.26.15.3114
243191.26.15.32/28191.26.15.33 to 191.26.15.46191.26.15.4714
244191.26.15.48/28191.26.15.49 to 191.26.15.62191.26.15.6314
245191.26.15.64/28191.26.15.65 to 191.26.15.78191.26.15.7914
246191.26.15.80/28191.26.15.81 to 191.26.15.94191.26.15.9514
247191.26.15.96/28191.26.15.97 to 191.26.15.110191.26.15.11114
248191.26.15.112/28191.26.15.113 to 191.26.15.126191.26.15.12714
249191.26.15.128/28191.26.15.129 to 191.26.15.142191.26.15.14314
250191.26.15.144/28191.26.15.145 to 191.26.15.158191.26.15.15914
251191.26.15.160/28191.26.15.161 to 191.26.15.174191.26.15.17514
252191.26.15.176/28191.26.15.177 to 191.26.15.190191.26.15.19114
253191.26.15.192/28191.26.15.193 to 191.26.15.206191.26.15.20714
254191.26.15.208/28191.26.15.209 to 191.26.15.222191.26.15.22314
255191.26.15.224/28191.26.15.225 to 191.26.15.238191.26.15.23914
256191.26.15.240/28191.26.15.241 to 191.26.15.254191.26.15.25514

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.