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.

Network238.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
238.0.0.0
Broadcast address
238.127.255.255
First usable
238.0.0.1
Last usable
238.127.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex EE000000 · Integer 3992977408 to 4001366015
Reverse DNS zones
0.238.in-addr.arpa
1.238.in-addr.arpa
2.238.in-addr.arpa
3.238.in-addr.arpa
4.238.in-addr.arpa
5.238.in-addr.arpa
6.238.in-addr.arpa
7.238.in-addr.arpa
8.238.in-addr.arpa
9.238.in-addr.arpa
10.238.in-addr.arpa
11.238.in-addr.arpa
12.238.in-addr.arpa
13.238.in-addr.arpa
14.238.in-addr.arpa
15.238.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11101110.00000000.00000000.00000000238.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network11101110.00000000.00000000.00000000238.0.0.0
Broadcast11101110.01111111.11111111.11111111238.127.255.255
Split into smaller subnets/19
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

238.0.0.0/9 makes 1,024 subnets of /19; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1238.0.0.0/19238.0.0.1 to 238.0.31.254238.0.31.2558,190
2238.0.32.0/19238.0.32.1 to 238.0.63.254238.0.63.2558,190
3238.0.64.0/19238.0.64.1 to 238.0.95.254238.0.95.2558,190
4238.0.96.0/19238.0.96.1 to 238.0.127.254238.0.127.2558,190
5238.0.128.0/19238.0.128.1 to 238.0.159.254238.0.159.2558,190
6238.0.160.0/19238.0.160.1 to 238.0.191.254238.0.191.2558,190
7238.0.192.0/19238.0.192.1 to 238.0.223.254238.0.223.2558,190
8238.0.224.0/19238.0.224.1 to 238.0.255.254238.0.255.2558,190
9238.1.0.0/19238.1.0.1 to 238.1.31.254238.1.31.2558,190
10238.1.32.0/19238.1.32.1 to 238.1.63.254238.1.63.2558,190
11238.1.64.0/19238.1.64.1 to 238.1.95.254238.1.95.2558,190
12238.1.96.0/19238.1.96.1 to 238.1.127.254238.1.127.2558,190
13238.1.128.0/19238.1.128.1 to 238.1.159.254238.1.159.2558,190
14238.1.160.0/19238.1.160.1 to 238.1.191.254238.1.191.2558,190
15238.1.192.0/19238.1.192.1 to 238.1.223.254238.1.223.2558,190
16238.1.224.0/19238.1.224.1 to 238.1.255.254238.1.255.2558,190
17238.2.0.0/19238.2.0.1 to 238.2.31.254238.2.31.2558,190
18238.2.32.0/19238.2.32.1 to 238.2.63.254238.2.63.2558,190
19238.2.64.0/19238.2.64.1 to 238.2.95.254238.2.95.2558,190
20238.2.96.0/19238.2.96.1 to 238.2.127.254238.2.127.2558,190
21238.2.128.0/19238.2.128.1 to 238.2.159.254238.2.159.2558,190
22238.2.160.0/19238.2.160.1 to 238.2.191.254238.2.191.2558,190
23238.2.192.0/19238.2.192.1 to 238.2.223.254238.2.223.2558,190
24238.2.224.0/19238.2.224.1 to 238.2.255.254238.2.255.2558,190
25238.3.0.0/19238.3.0.1 to 238.3.31.254238.3.31.2558,190
26238.3.32.0/19238.3.32.1 to 238.3.63.254238.3.63.2558,190
27238.3.64.0/19238.3.64.1 to 238.3.95.254238.3.95.2558,190
28238.3.96.0/19238.3.96.1 to 238.3.127.254238.3.127.2558,190
29238.3.128.0/19238.3.128.1 to 238.3.159.254238.3.159.2558,190
30238.3.160.0/19238.3.160.1 to 238.3.191.254238.3.191.2558,190
31238.3.192.0/19238.3.192.1 to 238.3.223.254238.3.223.2558,190
32238.3.224.0/19238.3.224.1 to 238.3.255.254238.3.255.2558,190
33238.4.0.0/19238.4.0.1 to 238.4.31.254238.4.31.2558,190
34238.4.32.0/19238.4.32.1 to 238.4.63.254238.4.63.2558,190
35238.4.64.0/19238.4.64.1 to 238.4.95.254238.4.95.2558,190
36238.4.96.0/19238.4.96.1 to 238.4.127.254238.4.127.2558,190
37238.4.128.0/19238.4.128.1 to 238.4.159.254238.4.159.2558,190
38238.4.160.0/19238.4.160.1 to 238.4.191.254238.4.191.2558,190
39238.4.192.0/19238.4.192.1 to 238.4.223.254238.4.223.2558,190
40238.4.224.0/19238.4.224.1 to 238.4.255.254238.4.255.2558,190
41238.5.0.0/19238.5.0.1 to 238.5.31.254238.5.31.2558,190
42238.5.32.0/19238.5.32.1 to 238.5.63.254238.5.63.2558,190
43238.5.64.0/19238.5.64.1 to 238.5.95.254238.5.95.2558,190
44238.5.96.0/19238.5.96.1 to 238.5.127.254238.5.127.2558,190
45238.5.128.0/19238.5.128.1 to 238.5.159.254238.5.159.2558,190
46238.5.160.0/19238.5.160.1 to 238.5.191.254238.5.191.2558,190
47238.5.192.0/19238.5.192.1 to 238.5.223.254238.5.223.2558,190
48238.5.224.0/19238.5.224.1 to 238.5.255.254238.5.255.2558,190
49238.6.0.0/19238.6.0.1 to 238.6.31.254238.6.31.2558,190
50238.6.32.0/19238.6.32.1 to 238.6.63.254238.6.63.2558,190
51238.6.64.0/19238.6.64.1 to 238.6.95.254238.6.95.2558,190
52238.6.96.0/19238.6.96.1 to 238.6.127.254238.6.127.2558,190
53238.6.128.0/19238.6.128.1 to 238.6.159.254238.6.159.2558,190
54238.6.160.0/19238.6.160.1 to 238.6.191.254238.6.191.2558,190
55238.6.192.0/19238.6.192.1 to 238.6.223.254238.6.223.2558,190
56238.6.224.0/19238.6.224.1 to 238.6.255.254238.6.255.2558,190
57238.7.0.0/19238.7.0.1 to 238.7.31.254238.7.31.2558,190
58238.7.32.0/19238.7.32.1 to 238.7.63.254238.7.63.2558,190
59238.7.64.0/19238.7.64.1 to 238.7.95.254238.7.95.2558,190
60238.7.96.0/19238.7.96.1 to 238.7.127.254238.7.127.2558,190
61238.7.128.0/19238.7.128.1 to 238.7.159.254238.7.159.2558,190
62238.7.160.0/19238.7.160.1 to 238.7.191.254238.7.191.2558,190
63238.7.192.0/19238.7.192.1 to 238.7.223.254238.7.223.2558,190
64238.7.224.0/19238.7.224.1 to 238.7.255.254238.7.255.2558,190
65238.8.0.0/19238.8.0.1 to 238.8.31.254238.8.31.2558,190
66238.8.32.0/19238.8.32.1 to 238.8.63.254238.8.63.2558,190
67238.8.64.0/19238.8.64.1 to 238.8.95.254238.8.95.2558,190
68238.8.96.0/19238.8.96.1 to 238.8.127.254238.8.127.2558,190
69238.8.128.0/19238.8.128.1 to 238.8.159.254238.8.159.2558,190
70238.8.160.0/19238.8.160.1 to 238.8.191.254238.8.191.2558,190
71238.8.192.0/19238.8.192.1 to 238.8.223.254238.8.223.2558,190
72238.8.224.0/19238.8.224.1 to 238.8.255.254238.8.255.2558,190
73238.9.0.0/19238.9.0.1 to 238.9.31.254238.9.31.2558,190
74238.9.32.0/19238.9.32.1 to 238.9.63.254238.9.63.2558,190
75238.9.64.0/19238.9.64.1 to 238.9.95.254238.9.95.2558,190
76238.9.96.0/19238.9.96.1 to 238.9.127.254238.9.127.2558,190
77238.9.128.0/19238.9.128.1 to 238.9.159.254238.9.159.2558,190
78238.9.160.0/19238.9.160.1 to 238.9.191.254238.9.191.2558,190
79238.9.192.0/19238.9.192.1 to 238.9.223.254238.9.223.2558,190
80238.9.224.0/19238.9.224.1 to 238.9.255.254238.9.255.2558,190
81238.10.0.0/19238.10.0.1 to 238.10.31.254238.10.31.2558,190
82238.10.32.0/19238.10.32.1 to 238.10.63.254238.10.63.2558,190
83238.10.64.0/19238.10.64.1 to 238.10.95.254238.10.95.2558,190
84238.10.96.0/19238.10.96.1 to 238.10.127.254238.10.127.2558,190
85238.10.128.0/19238.10.128.1 to 238.10.159.254238.10.159.2558,190
86238.10.160.0/19238.10.160.1 to 238.10.191.254238.10.191.2558,190
87238.10.192.0/19238.10.192.1 to 238.10.223.254238.10.223.2558,190
88238.10.224.0/19238.10.224.1 to 238.10.255.254238.10.255.2558,190
89238.11.0.0/19238.11.0.1 to 238.11.31.254238.11.31.2558,190
90238.11.32.0/19238.11.32.1 to 238.11.63.254238.11.63.2558,190
91238.11.64.0/19238.11.64.1 to 238.11.95.254238.11.95.2558,190
92238.11.96.0/19238.11.96.1 to 238.11.127.254238.11.127.2558,190
93238.11.128.0/19238.11.128.1 to 238.11.159.254238.11.159.2558,190
94238.11.160.0/19238.11.160.1 to 238.11.191.254238.11.191.2558,190
95238.11.192.0/19238.11.192.1 to 238.11.223.254238.11.223.2558,190
96238.11.224.0/19238.11.224.1 to 238.11.255.254238.11.255.2558,190
97238.12.0.0/19238.12.0.1 to 238.12.31.254238.12.31.2558,190
98238.12.32.0/19238.12.32.1 to 238.12.63.254238.12.63.2558,190
99238.12.64.0/19238.12.64.1 to 238.12.95.254238.12.95.2558,190
100238.12.96.0/19238.12.96.1 to 238.12.127.254238.12.127.2558,190
101238.12.128.0/19238.12.128.1 to 238.12.159.254238.12.159.2558,190
102238.12.160.0/19238.12.160.1 to 238.12.191.254238.12.191.2558,190
103238.12.192.0/19238.12.192.1 to 238.12.223.254238.12.223.2558,190
104238.12.224.0/19238.12.224.1 to 238.12.255.254238.12.255.2558,190
105238.13.0.0/19238.13.0.1 to 238.13.31.254238.13.31.2558,190
106238.13.32.0/19238.13.32.1 to 238.13.63.254238.13.63.2558,190
107238.13.64.0/19238.13.64.1 to 238.13.95.254238.13.95.2558,190
108238.13.96.0/19238.13.96.1 to 238.13.127.254238.13.127.2558,190
109238.13.128.0/19238.13.128.1 to 238.13.159.254238.13.159.2558,190
110238.13.160.0/19238.13.160.1 to 238.13.191.254238.13.191.2558,190
111238.13.192.0/19238.13.192.1 to 238.13.223.254238.13.223.2558,190
112238.13.224.0/19238.13.224.1 to 238.13.255.254238.13.255.2558,190
113238.14.0.0/19238.14.0.1 to 238.14.31.254238.14.31.2558,190
114238.14.32.0/19238.14.32.1 to 238.14.63.254238.14.63.2558,190
115238.14.64.0/19238.14.64.1 to 238.14.95.254238.14.95.2558,190
116238.14.96.0/19238.14.96.1 to 238.14.127.254238.14.127.2558,190
117238.14.128.0/19238.14.128.1 to 238.14.159.254238.14.159.2558,190
118238.14.160.0/19238.14.160.1 to 238.14.191.254238.14.191.2558,190
119238.14.192.0/19238.14.192.1 to 238.14.223.254238.14.223.2558,190
120238.14.224.0/19238.14.224.1 to 238.14.255.254238.14.255.2558,190
121238.15.0.0/19238.15.0.1 to 238.15.31.254238.15.31.2558,190
122238.15.32.0/19238.15.32.1 to 238.15.63.254238.15.63.2558,190
123238.15.64.0/19238.15.64.1 to 238.15.95.254238.15.95.2558,190
124238.15.96.0/19238.15.96.1 to 238.15.127.254238.15.127.2558,190
125238.15.128.0/19238.15.128.1 to 238.15.159.254238.15.159.2558,190
126238.15.160.0/19238.15.160.1 to 238.15.191.254238.15.191.2558,190
127238.15.192.0/19238.15.192.1 to 238.15.223.254238.15.223.2558,190
128238.15.224.0/19238.15.224.1 to 238.15.255.254238.15.255.2558,190
129238.16.0.0/19238.16.0.1 to 238.16.31.254238.16.31.2558,190
130238.16.32.0/19238.16.32.1 to 238.16.63.254238.16.63.2558,190
131238.16.64.0/19238.16.64.1 to 238.16.95.254238.16.95.2558,190
132238.16.96.0/19238.16.96.1 to 238.16.127.254238.16.127.2558,190
133238.16.128.0/19238.16.128.1 to 238.16.159.254238.16.159.2558,190
134238.16.160.0/19238.16.160.1 to 238.16.191.254238.16.191.2558,190
135238.16.192.0/19238.16.192.1 to 238.16.223.254238.16.223.2558,190
136238.16.224.0/19238.16.224.1 to 238.16.255.254238.16.255.2558,190
137238.17.0.0/19238.17.0.1 to 238.17.31.254238.17.31.2558,190
138238.17.32.0/19238.17.32.1 to 238.17.63.254238.17.63.2558,190
139238.17.64.0/19238.17.64.1 to 238.17.95.254238.17.95.2558,190
140238.17.96.0/19238.17.96.1 to 238.17.127.254238.17.127.2558,190
141238.17.128.0/19238.17.128.1 to 238.17.159.254238.17.159.2558,190
142238.17.160.0/19238.17.160.1 to 238.17.191.254238.17.191.2558,190
143238.17.192.0/19238.17.192.1 to 238.17.223.254238.17.223.2558,190
144238.17.224.0/19238.17.224.1 to 238.17.255.254238.17.255.2558,190
145238.18.0.0/19238.18.0.1 to 238.18.31.254238.18.31.2558,190
146238.18.32.0/19238.18.32.1 to 238.18.63.254238.18.63.2558,190
147238.18.64.0/19238.18.64.1 to 238.18.95.254238.18.95.2558,190
148238.18.96.0/19238.18.96.1 to 238.18.127.254238.18.127.2558,190
149238.18.128.0/19238.18.128.1 to 238.18.159.254238.18.159.2558,190
150238.18.160.0/19238.18.160.1 to 238.18.191.254238.18.191.2558,190
151238.18.192.0/19238.18.192.1 to 238.18.223.254238.18.223.2558,190
152238.18.224.0/19238.18.224.1 to 238.18.255.254238.18.255.2558,190
153238.19.0.0/19238.19.0.1 to 238.19.31.254238.19.31.2558,190
154238.19.32.0/19238.19.32.1 to 238.19.63.254238.19.63.2558,190
155238.19.64.0/19238.19.64.1 to 238.19.95.254238.19.95.2558,190
156238.19.96.0/19238.19.96.1 to 238.19.127.254238.19.127.2558,190
157238.19.128.0/19238.19.128.1 to 238.19.159.254238.19.159.2558,190
158238.19.160.0/19238.19.160.1 to 238.19.191.254238.19.191.2558,190
159238.19.192.0/19238.19.192.1 to 238.19.223.254238.19.223.2558,190
160238.19.224.0/19238.19.224.1 to 238.19.255.254238.19.255.2558,190
161238.20.0.0/19238.20.0.1 to 238.20.31.254238.20.31.2558,190
162238.20.32.0/19238.20.32.1 to 238.20.63.254238.20.63.2558,190
163238.20.64.0/19238.20.64.1 to 238.20.95.254238.20.95.2558,190
164238.20.96.0/19238.20.96.1 to 238.20.127.254238.20.127.2558,190
165238.20.128.0/19238.20.128.1 to 238.20.159.254238.20.159.2558,190
166238.20.160.0/19238.20.160.1 to 238.20.191.254238.20.191.2558,190
167238.20.192.0/19238.20.192.1 to 238.20.223.254238.20.223.2558,190
168238.20.224.0/19238.20.224.1 to 238.20.255.254238.20.255.2558,190
169238.21.0.0/19238.21.0.1 to 238.21.31.254238.21.31.2558,190
170238.21.32.0/19238.21.32.1 to 238.21.63.254238.21.63.2558,190
171238.21.64.0/19238.21.64.1 to 238.21.95.254238.21.95.2558,190
172238.21.96.0/19238.21.96.1 to 238.21.127.254238.21.127.2558,190
173238.21.128.0/19238.21.128.1 to 238.21.159.254238.21.159.2558,190
174238.21.160.0/19238.21.160.1 to 238.21.191.254238.21.191.2558,190
175238.21.192.0/19238.21.192.1 to 238.21.223.254238.21.223.2558,190
176238.21.224.0/19238.21.224.1 to 238.21.255.254238.21.255.2558,190
177238.22.0.0/19238.22.0.1 to 238.22.31.254238.22.31.2558,190
178238.22.32.0/19238.22.32.1 to 238.22.63.254238.22.63.2558,190
179238.22.64.0/19238.22.64.1 to 238.22.95.254238.22.95.2558,190
180238.22.96.0/19238.22.96.1 to 238.22.127.254238.22.127.2558,190
181238.22.128.0/19238.22.128.1 to 238.22.159.254238.22.159.2558,190
182238.22.160.0/19238.22.160.1 to 238.22.191.254238.22.191.2558,190
183238.22.192.0/19238.22.192.1 to 238.22.223.254238.22.223.2558,190
184238.22.224.0/19238.22.224.1 to 238.22.255.254238.22.255.2558,190
185238.23.0.0/19238.23.0.1 to 238.23.31.254238.23.31.2558,190
186238.23.32.0/19238.23.32.1 to 238.23.63.254238.23.63.2558,190
187238.23.64.0/19238.23.64.1 to 238.23.95.254238.23.95.2558,190
188238.23.96.0/19238.23.96.1 to 238.23.127.254238.23.127.2558,190
189238.23.128.0/19238.23.128.1 to 238.23.159.254238.23.159.2558,190
190238.23.160.0/19238.23.160.1 to 238.23.191.254238.23.191.2558,190
191238.23.192.0/19238.23.192.1 to 238.23.223.254238.23.223.2558,190
192238.23.224.0/19238.23.224.1 to 238.23.255.254238.23.255.2558,190
193238.24.0.0/19238.24.0.1 to 238.24.31.254238.24.31.2558,190
194238.24.32.0/19238.24.32.1 to 238.24.63.254238.24.63.2558,190
195238.24.64.0/19238.24.64.1 to 238.24.95.254238.24.95.2558,190
196238.24.96.0/19238.24.96.1 to 238.24.127.254238.24.127.2558,190
197238.24.128.0/19238.24.128.1 to 238.24.159.254238.24.159.2558,190
198238.24.160.0/19238.24.160.1 to 238.24.191.254238.24.191.2558,190
199238.24.192.0/19238.24.192.1 to 238.24.223.254238.24.223.2558,190
200238.24.224.0/19238.24.224.1 to 238.24.255.254238.24.255.2558,190
201238.25.0.0/19238.25.0.1 to 238.25.31.254238.25.31.2558,190
202238.25.32.0/19238.25.32.1 to 238.25.63.254238.25.63.2558,190
203238.25.64.0/19238.25.64.1 to 238.25.95.254238.25.95.2558,190
204238.25.96.0/19238.25.96.1 to 238.25.127.254238.25.127.2558,190
205238.25.128.0/19238.25.128.1 to 238.25.159.254238.25.159.2558,190
206238.25.160.0/19238.25.160.1 to 238.25.191.254238.25.191.2558,190
207238.25.192.0/19238.25.192.1 to 238.25.223.254238.25.223.2558,190
208238.25.224.0/19238.25.224.1 to 238.25.255.254238.25.255.2558,190
209238.26.0.0/19238.26.0.1 to 238.26.31.254238.26.31.2558,190
210238.26.32.0/19238.26.32.1 to 238.26.63.254238.26.63.2558,190
211238.26.64.0/19238.26.64.1 to 238.26.95.254238.26.95.2558,190
212238.26.96.0/19238.26.96.1 to 238.26.127.254238.26.127.2558,190
213238.26.128.0/19238.26.128.1 to 238.26.159.254238.26.159.2558,190
214238.26.160.0/19238.26.160.1 to 238.26.191.254238.26.191.2558,190
215238.26.192.0/19238.26.192.1 to 238.26.223.254238.26.223.2558,190
216238.26.224.0/19238.26.224.1 to 238.26.255.254238.26.255.2558,190
217238.27.0.0/19238.27.0.1 to 238.27.31.254238.27.31.2558,190
218238.27.32.0/19238.27.32.1 to 238.27.63.254238.27.63.2558,190
219238.27.64.0/19238.27.64.1 to 238.27.95.254238.27.95.2558,190
220238.27.96.0/19238.27.96.1 to 238.27.127.254238.27.127.2558,190
221238.27.128.0/19238.27.128.1 to 238.27.159.254238.27.159.2558,190
222238.27.160.0/19238.27.160.1 to 238.27.191.254238.27.191.2558,190
223238.27.192.0/19238.27.192.1 to 238.27.223.254238.27.223.2558,190
224238.27.224.0/19238.27.224.1 to 238.27.255.254238.27.255.2558,190
225238.28.0.0/19238.28.0.1 to 238.28.31.254238.28.31.2558,190
226238.28.32.0/19238.28.32.1 to 238.28.63.254238.28.63.2558,190
227238.28.64.0/19238.28.64.1 to 238.28.95.254238.28.95.2558,190
228238.28.96.0/19238.28.96.1 to 238.28.127.254238.28.127.2558,190
229238.28.128.0/19238.28.128.1 to 238.28.159.254238.28.159.2558,190
230238.28.160.0/19238.28.160.1 to 238.28.191.254238.28.191.2558,190
231238.28.192.0/19238.28.192.1 to 238.28.223.254238.28.223.2558,190
232238.28.224.0/19238.28.224.1 to 238.28.255.254238.28.255.2558,190
233238.29.0.0/19238.29.0.1 to 238.29.31.254238.29.31.2558,190
234238.29.32.0/19238.29.32.1 to 238.29.63.254238.29.63.2558,190
235238.29.64.0/19238.29.64.1 to 238.29.95.254238.29.95.2558,190
236238.29.96.0/19238.29.96.1 to 238.29.127.254238.29.127.2558,190
237238.29.128.0/19238.29.128.1 to 238.29.159.254238.29.159.2558,190
238238.29.160.0/19238.29.160.1 to 238.29.191.254238.29.191.2558,190
239238.29.192.0/19238.29.192.1 to 238.29.223.254238.29.223.2558,190
240238.29.224.0/19238.29.224.1 to 238.29.255.254238.29.255.2558,190
241238.30.0.0/19238.30.0.1 to 238.30.31.254238.30.31.2558,190
242238.30.32.0/19238.30.32.1 to 238.30.63.254238.30.63.2558,190
243238.30.64.0/19238.30.64.1 to 238.30.95.254238.30.95.2558,190
244238.30.96.0/19238.30.96.1 to 238.30.127.254238.30.127.2558,190
245238.30.128.0/19238.30.128.1 to 238.30.159.254238.30.159.2558,190
246238.30.160.0/19238.30.160.1 to 238.30.191.254238.30.191.2558,190
247238.30.192.0/19238.30.192.1 to 238.30.223.254238.30.223.2558,190
248238.30.224.0/19238.30.224.1 to 238.30.255.254238.30.255.2558,190
249238.31.0.0/19238.31.0.1 to 238.31.31.254238.31.31.2558,190
250238.31.32.0/19238.31.32.1 to 238.31.63.254238.31.63.2558,190
251238.31.64.0/19238.31.64.1 to 238.31.95.254238.31.95.2558,190
252238.31.96.0/19238.31.96.1 to 238.31.127.254238.31.127.2558,190
253238.31.128.0/19238.31.128.1 to 238.31.159.254238.31.159.2558,190
254238.31.160.0/19238.31.160.1 to 238.31.191.254238.31.191.2558,190
255238.31.192.0/19238.31.192.1 to 238.31.223.254238.31.223.2558,190
256238.31.224.0/19238.31.224.1 to 238.31.255.254238.31.255.2558,190

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.