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.

Network161.0.0.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
161.0.0.0
Broadcast address
161.0.31.255
First usable
161.0.0.1
Last usable
161.0.31.254
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
Public public
Old class
B (default /16)
As numbers
Hex A1000000 · Integer 2701131776 to 2701139967
Reverse DNS zones
0.0.161.in-addr.arpa
1.0.161.in-addr.arpa
2.0.161.in-addr.arpa
3.0.161.in-addr.arpa
4.0.161.in-addr.arpa
5.0.161.in-addr.arpa
6.0.161.in-addr.arpa
7.0.161.in-addr.arpa
8.0.161.in-addr.arpa
9.0.161.in-addr.arpa
10.0.161.in-addr.arpa
11.0.161.in-addr.arpa
12.0.161.in-addr.arpa
13.0.161.in-addr.arpa
14.0.161.in-addr.arpa
15.0.161.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
Address10100001.00000000.00000000.00000000161.0.0.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network10100001.00000000.00000000.00000000161.0.0.0
Broadcast10100001.00000000.00011111.11111111161.0.31.255
Split into smaller subnets/29
/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)

161.0.0.0/19 makes 1,024 subnets of /29; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1161.0.0.0/29161.0.0.1 to 161.0.0.6161.0.0.76
2161.0.0.8/29161.0.0.9 to 161.0.0.14161.0.0.156
3161.0.0.16/29161.0.0.17 to 161.0.0.22161.0.0.236
4161.0.0.24/29161.0.0.25 to 161.0.0.30161.0.0.316
5161.0.0.32/29161.0.0.33 to 161.0.0.38161.0.0.396
6161.0.0.40/29161.0.0.41 to 161.0.0.46161.0.0.476
7161.0.0.48/29161.0.0.49 to 161.0.0.54161.0.0.556
8161.0.0.56/29161.0.0.57 to 161.0.0.62161.0.0.636
9161.0.0.64/29161.0.0.65 to 161.0.0.70161.0.0.716
10161.0.0.72/29161.0.0.73 to 161.0.0.78161.0.0.796
11161.0.0.80/29161.0.0.81 to 161.0.0.86161.0.0.876
12161.0.0.88/29161.0.0.89 to 161.0.0.94161.0.0.956
13161.0.0.96/29161.0.0.97 to 161.0.0.102161.0.0.1036
14161.0.0.104/29161.0.0.105 to 161.0.0.110161.0.0.1116
15161.0.0.112/29161.0.0.113 to 161.0.0.118161.0.0.1196
16161.0.0.120/29161.0.0.121 to 161.0.0.126161.0.0.1276
17161.0.0.128/29161.0.0.129 to 161.0.0.134161.0.0.1356
18161.0.0.136/29161.0.0.137 to 161.0.0.142161.0.0.1436
19161.0.0.144/29161.0.0.145 to 161.0.0.150161.0.0.1516
20161.0.0.152/29161.0.0.153 to 161.0.0.158161.0.0.1596
21161.0.0.160/29161.0.0.161 to 161.0.0.166161.0.0.1676
22161.0.0.168/29161.0.0.169 to 161.0.0.174161.0.0.1756
23161.0.0.176/29161.0.0.177 to 161.0.0.182161.0.0.1836
24161.0.0.184/29161.0.0.185 to 161.0.0.190161.0.0.1916
25161.0.0.192/29161.0.0.193 to 161.0.0.198161.0.0.1996
26161.0.0.200/29161.0.0.201 to 161.0.0.206161.0.0.2076
27161.0.0.208/29161.0.0.209 to 161.0.0.214161.0.0.2156
28161.0.0.216/29161.0.0.217 to 161.0.0.222161.0.0.2236
29161.0.0.224/29161.0.0.225 to 161.0.0.230161.0.0.2316
30161.0.0.232/29161.0.0.233 to 161.0.0.238161.0.0.2396
31161.0.0.240/29161.0.0.241 to 161.0.0.246161.0.0.2476
32161.0.0.248/29161.0.0.249 to 161.0.0.254161.0.0.2556
33161.0.1.0/29161.0.1.1 to 161.0.1.6161.0.1.76
34161.0.1.8/29161.0.1.9 to 161.0.1.14161.0.1.156
35161.0.1.16/29161.0.1.17 to 161.0.1.22161.0.1.236
36161.0.1.24/29161.0.1.25 to 161.0.1.30161.0.1.316
37161.0.1.32/29161.0.1.33 to 161.0.1.38161.0.1.396
38161.0.1.40/29161.0.1.41 to 161.0.1.46161.0.1.476
39161.0.1.48/29161.0.1.49 to 161.0.1.54161.0.1.556
40161.0.1.56/29161.0.1.57 to 161.0.1.62161.0.1.636
41161.0.1.64/29161.0.1.65 to 161.0.1.70161.0.1.716
42161.0.1.72/29161.0.1.73 to 161.0.1.78161.0.1.796
43161.0.1.80/29161.0.1.81 to 161.0.1.86161.0.1.876
44161.0.1.88/29161.0.1.89 to 161.0.1.94161.0.1.956
45161.0.1.96/29161.0.1.97 to 161.0.1.102161.0.1.1036
46161.0.1.104/29161.0.1.105 to 161.0.1.110161.0.1.1116
47161.0.1.112/29161.0.1.113 to 161.0.1.118161.0.1.1196
48161.0.1.120/29161.0.1.121 to 161.0.1.126161.0.1.1276
49161.0.1.128/29161.0.1.129 to 161.0.1.134161.0.1.1356
50161.0.1.136/29161.0.1.137 to 161.0.1.142161.0.1.1436
51161.0.1.144/29161.0.1.145 to 161.0.1.150161.0.1.1516
52161.0.1.152/29161.0.1.153 to 161.0.1.158161.0.1.1596
53161.0.1.160/29161.0.1.161 to 161.0.1.166161.0.1.1676
54161.0.1.168/29161.0.1.169 to 161.0.1.174161.0.1.1756
55161.0.1.176/29161.0.1.177 to 161.0.1.182161.0.1.1836
56161.0.1.184/29161.0.1.185 to 161.0.1.190161.0.1.1916
57161.0.1.192/29161.0.1.193 to 161.0.1.198161.0.1.1996
58161.0.1.200/29161.0.1.201 to 161.0.1.206161.0.1.2076
59161.0.1.208/29161.0.1.209 to 161.0.1.214161.0.1.2156
60161.0.1.216/29161.0.1.217 to 161.0.1.222161.0.1.2236
61161.0.1.224/29161.0.1.225 to 161.0.1.230161.0.1.2316
62161.0.1.232/29161.0.1.233 to 161.0.1.238161.0.1.2396
63161.0.1.240/29161.0.1.241 to 161.0.1.246161.0.1.2476
64161.0.1.248/29161.0.1.249 to 161.0.1.254161.0.1.2556
65161.0.2.0/29161.0.2.1 to 161.0.2.6161.0.2.76
66161.0.2.8/29161.0.2.9 to 161.0.2.14161.0.2.156
67161.0.2.16/29161.0.2.17 to 161.0.2.22161.0.2.236
68161.0.2.24/29161.0.2.25 to 161.0.2.30161.0.2.316
69161.0.2.32/29161.0.2.33 to 161.0.2.38161.0.2.396
70161.0.2.40/29161.0.2.41 to 161.0.2.46161.0.2.476
71161.0.2.48/29161.0.2.49 to 161.0.2.54161.0.2.556
72161.0.2.56/29161.0.2.57 to 161.0.2.62161.0.2.636
73161.0.2.64/29161.0.2.65 to 161.0.2.70161.0.2.716
74161.0.2.72/29161.0.2.73 to 161.0.2.78161.0.2.796
75161.0.2.80/29161.0.2.81 to 161.0.2.86161.0.2.876
76161.0.2.88/29161.0.2.89 to 161.0.2.94161.0.2.956
77161.0.2.96/29161.0.2.97 to 161.0.2.102161.0.2.1036
78161.0.2.104/29161.0.2.105 to 161.0.2.110161.0.2.1116
79161.0.2.112/29161.0.2.113 to 161.0.2.118161.0.2.1196
80161.0.2.120/29161.0.2.121 to 161.0.2.126161.0.2.1276
81161.0.2.128/29161.0.2.129 to 161.0.2.134161.0.2.1356
82161.0.2.136/29161.0.2.137 to 161.0.2.142161.0.2.1436
83161.0.2.144/29161.0.2.145 to 161.0.2.150161.0.2.1516
84161.0.2.152/29161.0.2.153 to 161.0.2.158161.0.2.1596
85161.0.2.160/29161.0.2.161 to 161.0.2.166161.0.2.1676
86161.0.2.168/29161.0.2.169 to 161.0.2.174161.0.2.1756
87161.0.2.176/29161.0.2.177 to 161.0.2.182161.0.2.1836
88161.0.2.184/29161.0.2.185 to 161.0.2.190161.0.2.1916
89161.0.2.192/29161.0.2.193 to 161.0.2.198161.0.2.1996
90161.0.2.200/29161.0.2.201 to 161.0.2.206161.0.2.2076
91161.0.2.208/29161.0.2.209 to 161.0.2.214161.0.2.2156
92161.0.2.216/29161.0.2.217 to 161.0.2.222161.0.2.2236
93161.0.2.224/29161.0.2.225 to 161.0.2.230161.0.2.2316
94161.0.2.232/29161.0.2.233 to 161.0.2.238161.0.2.2396
95161.0.2.240/29161.0.2.241 to 161.0.2.246161.0.2.2476
96161.0.2.248/29161.0.2.249 to 161.0.2.254161.0.2.2556
97161.0.3.0/29161.0.3.1 to 161.0.3.6161.0.3.76
98161.0.3.8/29161.0.3.9 to 161.0.3.14161.0.3.156
99161.0.3.16/29161.0.3.17 to 161.0.3.22161.0.3.236
100161.0.3.24/29161.0.3.25 to 161.0.3.30161.0.3.316
101161.0.3.32/29161.0.3.33 to 161.0.3.38161.0.3.396
102161.0.3.40/29161.0.3.41 to 161.0.3.46161.0.3.476
103161.0.3.48/29161.0.3.49 to 161.0.3.54161.0.3.556
104161.0.3.56/29161.0.3.57 to 161.0.3.62161.0.3.636
105161.0.3.64/29161.0.3.65 to 161.0.3.70161.0.3.716
106161.0.3.72/29161.0.3.73 to 161.0.3.78161.0.3.796
107161.0.3.80/29161.0.3.81 to 161.0.3.86161.0.3.876
108161.0.3.88/29161.0.3.89 to 161.0.3.94161.0.3.956
109161.0.3.96/29161.0.3.97 to 161.0.3.102161.0.3.1036
110161.0.3.104/29161.0.3.105 to 161.0.3.110161.0.3.1116
111161.0.3.112/29161.0.3.113 to 161.0.3.118161.0.3.1196
112161.0.3.120/29161.0.3.121 to 161.0.3.126161.0.3.1276
113161.0.3.128/29161.0.3.129 to 161.0.3.134161.0.3.1356
114161.0.3.136/29161.0.3.137 to 161.0.3.142161.0.3.1436
115161.0.3.144/29161.0.3.145 to 161.0.3.150161.0.3.1516
116161.0.3.152/29161.0.3.153 to 161.0.3.158161.0.3.1596
117161.0.3.160/29161.0.3.161 to 161.0.3.166161.0.3.1676
118161.0.3.168/29161.0.3.169 to 161.0.3.174161.0.3.1756
119161.0.3.176/29161.0.3.177 to 161.0.3.182161.0.3.1836
120161.0.3.184/29161.0.3.185 to 161.0.3.190161.0.3.1916
121161.0.3.192/29161.0.3.193 to 161.0.3.198161.0.3.1996
122161.0.3.200/29161.0.3.201 to 161.0.3.206161.0.3.2076
123161.0.3.208/29161.0.3.209 to 161.0.3.214161.0.3.2156
124161.0.3.216/29161.0.3.217 to 161.0.3.222161.0.3.2236
125161.0.3.224/29161.0.3.225 to 161.0.3.230161.0.3.2316
126161.0.3.232/29161.0.3.233 to 161.0.3.238161.0.3.2396
127161.0.3.240/29161.0.3.241 to 161.0.3.246161.0.3.2476
128161.0.3.248/29161.0.3.249 to 161.0.3.254161.0.3.2556
129161.0.4.0/29161.0.4.1 to 161.0.4.6161.0.4.76
130161.0.4.8/29161.0.4.9 to 161.0.4.14161.0.4.156
131161.0.4.16/29161.0.4.17 to 161.0.4.22161.0.4.236
132161.0.4.24/29161.0.4.25 to 161.0.4.30161.0.4.316
133161.0.4.32/29161.0.4.33 to 161.0.4.38161.0.4.396
134161.0.4.40/29161.0.4.41 to 161.0.4.46161.0.4.476
135161.0.4.48/29161.0.4.49 to 161.0.4.54161.0.4.556
136161.0.4.56/29161.0.4.57 to 161.0.4.62161.0.4.636
137161.0.4.64/29161.0.4.65 to 161.0.4.70161.0.4.716
138161.0.4.72/29161.0.4.73 to 161.0.4.78161.0.4.796
139161.0.4.80/29161.0.4.81 to 161.0.4.86161.0.4.876
140161.0.4.88/29161.0.4.89 to 161.0.4.94161.0.4.956
141161.0.4.96/29161.0.4.97 to 161.0.4.102161.0.4.1036
142161.0.4.104/29161.0.4.105 to 161.0.4.110161.0.4.1116
143161.0.4.112/29161.0.4.113 to 161.0.4.118161.0.4.1196
144161.0.4.120/29161.0.4.121 to 161.0.4.126161.0.4.1276
145161.0.4.128/29161.0.4.129 to 161.0.4.134161.0.4.1356
146161.0.4.136/29161.0.4.137 to 161.0.4.142161.0.4.1436
147161.0.4.144/29161.0.4.145 to 161.0.4.150161.0.4.1516
148161.0.4.152/29161.0.4.153 to 161.0.4.158161.0.4.1596
149161.0.4.160/29161.0.4.161 to 161.0.4.166161.0.4.1676
150161.0.4.168/29161.0.4.169 to 161.0.4.174161.0.4.1756
151161.0.4.176/29161.0.4.177 to 161.0.4.182161.0.4.1836
152161.0.4.184/29161.0.4.185 to 161.0.4.190161.0.4.1916
153161.0.4.192/29161.0.4.193 to 161.0.4.198161.0.4.1996
154161.0.4.200/29161.0.4.201 to 161.0.4.206161.0.4.2076
155161.0.4.208/29161.0.4.209 to 161.0.4.214161.0.4.2156
156161.0.4.216/29161.0.4.217 to 161.0.4.222161.0.4.2236
157161.0.4.224/29161.0.4.225 to 161.0.4.230161.0.4.2316
158161.0.4.232/29161.0.4.233 to 161.0.4.238161.0.4.2396
159161.0.4.240/29161.0.4.241 to 161.0.4.246161.0.4.2476
160161.0.4.248/29161.0.4.249 to 161.0.4.254161.0.4.2556
161161.0.5.0/29161.0.5.1 to 161.0.5.6161.0.5.76
162161.0.5.8/29161.0.5.9 to 161.0.5.14161.0.5.156
163161.0.5.16/29161.0.5.17 to 161.0.5.22161.0.5.236
164161.0.5.24/29161.0.5.25 to 161.0.5.30161.0.5.316
165161.0.5.32/29161.0.5.33 to 161.0.5.38161.0.5.396
166161.0.5.40/29161.0.5.41 to 161.0.5.46161.0.5.476
167161.0.5.48/29161.0.5.49 to 161.0.5.54161.0.5.556
168161.0.5.56/29161.0.5.57 to 161.0.5.62161.0.5.636
169161.0.5.64/29161.0.5.65 to 161.0.5.70161.0.5.716
170161.0.5.72/29161.0.5.73 to 161.0.5.78161.0.5.796
171161.0.5.80/29161.0.5.81 to 161.0.5.86161.0.5.876
172161.0.5.88/29161.0.5.89 to 161.0.5.94161.0.5.956
173161.0.5.96/29161.0.5.97 to 161.0.5.102161.0.5.1036
174161.0.5.104/29161.0.5.105 to 161.0.5.110161.0.5.1116
175161.0.5.112/29161.0.5.113 to 161.0.5.118161.0.5.1196
176161.0.5.120/29161.0.5.121 to 161.0.5.126161.0.5.1276
177161.0.5.128/29161.0.5.129 to 161.0.5.134161.0.5.1356
178161.0.5.136/29161.0.5.137 to 161.0.5.142161.0.5.1436
179161.0.5.144/29161.0.5.145 to 161.0.5.150161.0.5.1516
180161.0.5.152/29161.0.5.153 to 161.0.5.158161.0.5.1596
181161.0.5.160/29161.0.5.161 to 161.0.5.166161.0.5.1676
182161.0.5.168/29161.0.5.169 to 161.0.5.174161.0.5.1756
183161.0.5.176/29161.0.5.177 to 161.0.5.182161.0.5.1836
184161.0.5.184/29161.0.5.185 to 161.0.5.190161.0.5.1916
185161.0.5.192/29161.0.5.193 to 161.0.5.198161.0.5.1996
186161.0.5.200/29161.0.5.201 to 161.0.5.206161.0.5.2076
187161.0.5.208/29161.0.5.209 to 161.0.5.214161.0.5.2156
188161.0.5.216/29161.0.5.217 to 161.0.5.222161.0.5.2236
189161.0.5.224/29161.0.5.225 to 161.0.5.230161.0.5.2316
190161.0.5.232/29161.0.5.233 to 161.0.5.238161.0.5.2396
191161.0.5.240/29161.0.5.241 to 161.0.5.246161.0.5.2476
192161.0.5.248/29161.0.5.249 to 161.0.5.254161.0.5.2556
193161.0.6.0/29161.0.6.1 to 161.0.6.6161.0.6.76
194161.0.6.8/29161.0.6.9 to 161.0.6.14161.0.6.156
195161.0.6.16/29161.0.6.17 to 161.0.6.22161.0.6.236
196161.0.6.24/29161.0.6.25 to 161.0.6.30161.0.6.316
197161.0.6.32/29161.0.6.33 to 161.0.6.38161.0.6.396
198161.0.6.40/29161.0.6.41 to 161.0.6.46161.0.6.476
199161.0.6.48/29161.0.6.49 to 161.0.6.54161.0.6.556
200161.0.6.56/29161.0.6.57 to 161.0.6.62161.0.6.636
201161.0.6.64/29161.0.6.65 to 161.0.6.70161.0.6.716
202161.0.6.72/29161.0.6.73 to 161.0.6.78161.0.6.796
203161.0.6.80/29161.0.6.81 to 161.0.6.86161.0.6.876
204161.0.6.88/29161.0.6.89 to 161.0.6.94161.0.6.956
205161.0.6.96/29161.0.6.97 to 161.0.6.102161.0.6.1036
206161.0.6.104/29161.0.6.105 to 161.0.6.110161.0.6.1116
207161.0.6.112/29161.0.6.113 to 161.0.6.118161.0.6.1196
208161.0.6.120/29161.0.6.121 to 161.0.6.126161.0.6.1276
209161.0.6.128/29161.0.6.129 to 161.0.6.134161.0.6.1356
210161.0.6.136/29161.0.6.137 to 161.0.6.142161.0.6.1436
211161.0.6.144/29161.0.6.145 to 161.0.6.150161.0.6.1516
212161.0.6.152/29161.0.6.153 to 161.0.6.158161.0.6.1596
213161.0.6.160/29161.0.6.161 to 161.0.6.166161.0.6.1676
214161.0.6.168/29161.0.6.169 to 161.0.6.174161.0.6.1756
215161.0.6.176/29161.0.6.177 to 161.0.6.182161.0.6.1836
216161.0.6.184/29161.0.6.185 to 161.0.6.190161.0.6.1916
217161.0.6.192/29161.0.6.193 to 161.0.6.198161.0.6.1996
218161.0.6.200/29161.0.6.201 to 161.0.6.206161.0.6.2076
219161.0.6.208/29161.0.6.209 to 161.0.6.214161.0.6.2156
220161.0.6.216/29161.0.6.217 to 161.0.6.222161.0.6.2236
221161.0.6.224/29161.0.6.225 to 161.0.6.230161.0.6.2316
222161.0.6.232/29161.0.6.233 to 161.0.6.238161.0.6.2396
223161.0.6.240/29161.0.6.241 to 161.0.6.246161.0.6.2476
224161.0.6.248/29161.0.6.249 to 161.0.6.254161.0.6.2556
225161.0.7.0/29161.0.7.1 to 161.0.7.6161.0.7.76
226161.0.7.8/29161.0.7.9 to 161.0.7.14161.0.7.156
227161.0.7.16/29161.0.7.17 to 161.0.7.22161.0.7.236
228161.0.7.24/29161.0.7.25 to 161.0.7.30161.0.7.316
229161.0.7.32/29161.0.7.33 to 161.0.7.38161.0.7.396
230161.0.7.40/29161.0.7.41 to 161.0.7.46161.0.7.476
231161.0.7.48/29161.0.7.49 to 161.0.7.54161.0.7.556
232161.0.7.56/29161.0.7.57 to 161.0.7.62161.0.7.636
233161.0.7.64/29161.0.7.65 to 161.0.7.70161.0.7.716
234161.0.7.72/29161.0.7.73 to 161.0.7.78161.0.7.796
235161.0.7.80/29161.0.7.81 to 161.0.7.86161.0.7.876
236161.0.7.88/29161.0.7.89 to 161.0.7.94161.0.7.956
237161.0.7.96/29161.0.7.97 to 161.0.7.102161.0.7.1036
238161.0.7.104/29161.0.7.105 to 161.0.7.110161.0.7.1116
239161.0.7.112/29161.0.7.113 to 161.0.7.118161.0.7.1196
240161.0.7.120/29161.0.7.121 to 161.0.7.126161.0.7.1276
241161.0.7.128/29161.0.7.129 to 161.0.7.134161.0.7.1356
242161.0.7.136/29161.0.7.137 to 161.0.7.142161.0.7.1436
243161.0.7.144/29161.0.7.145 to 161.0.7.150161.0.7.1516
244161.0.7.152/29161.0.7.153 to 161.0.7.158161.0.7.1596
245161.0.7.160/29161.0.7.161 to 161.0.7.166161.0.7.1676
246161.0.7.168/29161.0.7.169 to 161.0.7.174161.0.7.1756
247161.0.7.176/29161.0.7.177 to 161.0.7.182161.0.7.1836
248161.0.7.184/29161.0.7.185 to 161.0.7.190161.0.7.1916
249161.0.7.192/29161.0.7.193 to 161.0.7.198161.0.7.1996
250161.0.7.200/29161.0.7.201 to 161.0.7.206161.0.7.2076
251161.0.7.208/29161.0.7.209 to 161.0.7.214161.0.7.2156
252161.0.7.216/29161.0.7.217 to 161.0.7.222161.0.7.2236
253161.0.7.224/29161.0.7.225 to 161.0.7.230161.0.7.2316
254161.0.7.232/29161.0.7.233 to 161.0.7.238161.0.7.2396
255161.0.7.240/29161.0.7.241 to 161.0.7.246161.0.7.2476
256161.0.7.248/29161.0.7.249 to 161.0.7.254161.0.7.2556

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.