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/18
/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 512 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1238.0.0.0/18238.0.0.1 to 238.0.63.254238.0.63.25516,382
2238.0.64.0/18238.0.64.1 to 238.0.127.254238.0.127.25516,382
3238.0.128.0/18238.0.128.1 to 238.0.191.254238.0.191.25516,382
4238.0.192.0/18238.0.192.1 to 238.0.255.254238.0.255.25516,382
5238.1.0.0/18238.1.0.1 to 238.1.63.254238.1.63.25516,382
6238.1.64.0/18238.1.64.1 to 238.1.127.254238.1.127.25516,382
7238.1.128.0/18238.1.128.1 to 238.1.191.254238.1.191.25516,382
8238.1.192.0/18238.1.192.1 to 238.1.255.254238.1.255.25516,382
9238.2.0.0/18238.2.0.1 to 238.2.63.254238.2.63.25516,382
10238.2.64.0/18238.2.64.1 to 238.2.127.254238.2.127.25516,382
11238.2.128.0/18238.2.128.1 to 238.2.191.254238.2.191.25516,382
12238.2.192.0/18238.2.192.1 to 238.2.255.254238.2.255.25516,382
13238.3.0.0/18238.3.0.1 to 238.3.63.254238.3.63.25516,382
14238.3.64.0/18238.3.64.1 to 238.3.127.254238.3.127.25516,382
15238.3.128.0/18238.3.128.1 to 238.3.191.254238.3.191.25516,382
16238.3.192.0/18238.3.192.1 to 238.3.255.254238.3.255.25516,382
17238.4.0.0/18238.4.0.1 to 238.4.63.254238.4.63.25516,382
18238.4.64.0/18238.4.64.1 to 238.4.127.254238.4.127.25516,382
19238.4.128.0/18238.4.128.1 to 238.4.191.254238.4.191.25516,382
20238.4.192.0/18238.4.192.1 to 238.4.255.254238.4.255.25516,382
21238.5.0.0/18238.5.0.1 to 238.5.63.254238.5.63.25516,382
22238.5.64.0/18238.5.64.1 to 238.5.127.254238.5.127.25516,382
23238.5.128.0/18238.5.128.1 to 238.5.191.254238.5.191.25516,382
24238.5.192.0/18238.5.192.1 to 238.5.255.254238.5.255.25516,382
25238.6.0.0/18238.6.0.1 to 238.6.63.254238.6.63.25516,382
26238.6.64.0/18238.6.64.1 to 238.6.127.254238.6.127.25516,382
27238.6.128.0/18238.6.128.1 to 238.6.191.254238.6.191.25516,382
28238.6.192.0/18238.6.192.1 to 238.6.255.254238.6.255.25516,382
29238.7.0.0/18238.7.0.1 to 238.7.63.254238.7.63.25516,382
30238.7.64.0/18238.7.64.1 to 238.7.127.254238.7.127.25516,382
31238.7.128.0/18238.7.128.1 to 238.7.191.254238.7.191.25516,382
32238.7.192.0/18238.7.192.1 to 238.7.255.254238.7.255.25516,382
33238.8.0.0/18238.8.0.1 to 238.8.63.254238.8.63.25516,382
34238.8.64.0/18238.8.64.1 to 238.8.127.254238.8.127.25516,382
35238.8.128.0/18238.8.128.1 to 238.8.191.254238.8.191.25516,382
36238.8.192.0/18238.8.192.1 to 238.8.255.254238.8.255.25516,382
37238.9.0.0/18238.9.0.1 to 238.9.63.254238.9.63.25516,382
38238.9.64.0/18238.9.64.1 to 238.9.127.254238.9.127.25516,382
39238.9.128.0/18238.9.128.1 to 238.9.191.254238.9.191.25516,382
40238.9.192.0/18238.9.192.1 to 238.9.255.254238.9.255.25516,382
41238.10.0.0/18238.10.0.1 to 238.10.63.254238.10.63.25516,382
42238.10.64.0/18238.10.64.1 to 238.10.127.254238.10.127.25516,382
43238.10.128.0/18238.10.128.1 to 238.10.191.254238.10.191.25516,382
44238.10.192.0/18238.10.192.1 to 238.10.255.254238.10.255.25516,382
45238.11.0.0/18238.11.0.1 to 238.11.63.254238.11.63.25516,382
46238.11.64.0/18238.11.64.1 to 238.11.127.254238.11.127.25516,382
47238.11.128.0/18238.11.128.1 to 238.11.191.254238.11.191.25516,382
48238.11.192.0/18238.11.192.1 to 238.11.255.254238.11.255.25516,382
49238.12.0.0/18238.12.0.1 to 238.12.63.254238.12.63.25516,382
50238.12.64.0/18238.12.64.1 to 238.12.127.254238.12.127.25516,382
51238.12.128.0/18238.12.128.1 to 238.12.191.254238.12.191.25516,382
52238.12.192.0/18238.12.192.1 to 238.12.255.254238.12.255.25516,382
53238.13.0.0/18238.13.0.1 to 238.13.63.254238.13.63.25516,382
54238.13.64.0/18238.13.64.1 to 238.13.127.254238.13.127.25516,382
55238.13.128.0/18238.13.128.1 to 238.13.191.254238.13.191.25516,382
56238.13.192.0/18238.13.192.1 to 238.13.255.254238.13.255.25516,382
57238.14.0.0/18238.14.0.1 to 238.14.63.254238.14.63.25516,382
58238.14.64.0/18238.14.64.1 to 238.14.127.254238.14.127.25516,382
59238.14.128.0/18238.14.128.1 to 238.14.191.254238.14.191.25516,382
60238.14.192.0/18238.14.192.1 to 238.14.255.254238.14.255.25516,382
61238.15.0.0/18238.15.0.1 to 238.15.63.254238.15.63.25516,382
62238.15.64.0/18238.15.64.1 to 238.15.127.254238.15.127.25516,382
63238.15.128.0/18238.15.128.1 to 238.15.191.254238.15.191.25516,382
64238.15.192.0/18238.15.192.1 to 238.15.255.254238.15.255.25516,382
65238.16.0.0/18238.16.0.1 to 238.16.63.254238.16.63.25516,382
66238.16.64.0/18238.16.64.1 to 238.16.127.254238.16.127.25516,382
67238.16.128.0/18238.16.128.1 to 238.16.191.254238.16.191.25516,382
68238.16.192.0/18238.16.192.1 to 238.16.255.254238.16.255.25516,382
69238.17.0.0/18238.17.0.1 to 238.17.63.254238.17.63.25516,382
70238.17.64.0/18238.17.64.1 to 238.17.127.254238.17.127.25516,382
71238.17.128.0/18238.17.128.1 to 238.17.191.254238.17.191.25516,382
72238.17.192.0/18238.17.192.1 to 238.17.255.254238.17.255.25516,382
73238.18.0.0/18238.18.0.1 to 238.18.63.254238.18.63.25516,382
74238.18.64.0/18238.18.64.1 to 238.18.127.254238.18.127.25516,382
75238.18.128.0/18238.18.128.1 to 238.18.191.254238.18.191.25516,382
76238.18.192.0/18238.18.192.1 to 238.18.255.254238.18.255.25516,382
77238.19.0.0/18238.19.0.1 to 238.19.63.254238.19.63.25516,382
78238.19.64.0/18238.19.64.1 to 238.19.127.254238.19.127.25516,382
79238.19.128.0/18238.19.128.1 to 238.19.191.254238.19.191.25516,382
80238.19.192.0/18238.19.192.1 to 238.19.255.254238.19.255.25516,382
81238.20.0.0/18238.20.0.1 to 238.20.63.254238.20.63.25516,382
82238.20.64.0/18238.20.64.1 to 238.20.127.254238.20.127.25516,382
83238.20.128.0/18238.20.128.1 to 238.20.191.254238.20.191.25516,382
84238.20.192.0/18238.20.192.1 to 238.20.255.254238.20.255.25516,382
85238.21.0.0/18238.21.0.1 to 238.21.63.254238.21.63.25516,382
86238.21.64.0/18238.21.64.1 to 238.21.127.254238.21.127.25516,382
87238.21.128.0/18238.21.128.1 to 238.21.191.254238.21.191.25516,382
88238.21.192.0/18238.21.192.1 to 238.21.255.254238.21.255.25516,382
89238.22.0.0/18238.22.0.1 to 238.22.63.254238.22.63.25516,382
90238.22.64.0/18238.22.64.1 to 238.22.127.254238.22.127.25516,382
91238.22.128.0/18238.22.128.1 to 238.22.191.254238.22.191.25516,382
92238.22.192.0/18238.22.192.1 to 238.22.255.254238.22.255.25516,382
93238.23.0.0/18238.23.0.1 to 238.23.63.254238.23.63.25516,382
94238.23.64.0/18238.23.64.1 to 238.23.127.254238.23.127.25516,382
95238.23.128.0/18238.23.128.1 to 238.23.191.254238.23.191.25516,382
96238.23.192.0/18238.23.192.1 to 238.23.255.254238.23.255.25516,382
97238.24.0.0/18238.24.0.1 to 238.24.63.254238.24.63.25516,382
98238.24.64.0/18238.24.64.1 to 238.24.127.254238.24.127.25516,382
99238.24.128.0/18238.24.128.1 to 238.24.191.254238.24.191.25516,382
100238.24.192.0/18238.24.192.1 to 238.24.255.254238.24.255.25516,382
101238.25.0.0/18238.25.0.1 to 238.25.63.254238.25.63.25516,382
102238.25.64.0/18238.25.64.1 to 238.25.127.254238.25.127.25516,382
103238.25.128.0/18238.25.128.1 to 238.25.191.254238.25.191.25516,382
104238.25.192.0/18238.25.192.1 to 238.25.255.254238.25.255.25516,382
105238.26.0.0/18238.26.0.1 to 238.26.63.254238.26.63.25516,382
106238.26.64.0/18238.26.64.1 to 238.26.127.254238.26.127.25516,382
107238.26.128.0/18238.26.128.1 to 238.26.191.254238.26.191.25516,382
108238.26.192.0/18238.26.192.1 to 238.26.255.254238.26.255.25516,382
109238.27.0.0/18238.27.0.1 to 238.27.63.254238.27.63.25516,382
110238.27.64.0/18238.27.64.1 to 238.27.127.254238.27.127.25516,382
111238.27.128.0/18238.27.128.1 to 238.27.191.254238.27.191.25516,382
112238.27.192.0/18238.27.192.1 to 238.27.255.254238.27.255.25516,382
113238.28.0.0/18238.28.0.1 to 238.28.63.254238.28.63.25516,382
114238.28.64.0/18238.28.64.1 to 238.28.127.254238.28.127.25516,382
115238.28.128.0/18238.28.128.1 to 238.28.191.254238.28.191.25516,382
116238.28.192.0/18238.28.192.1 to 238.28.255.254238.28.255.25516,382
117238.29.0.0/18238.29.0.1 to 238.29.63.254238.29.63.25516,382
118238.29.64.0/18238.29.64.1 to 238.29.127.254238.29.127.25516,382
119238.29.128.0/18238.29.128.1 to 238.29.191.254238.29.191.25516,382
120238.29.192.0/18238.29.192.1 to 238.29.255.254238.29.255.25516,382
121238.30.0.0/18238.30.0.1 to 238.30.63.254238.30.63.25516,382
122238.30.64.0/18238.30.64.1 to 238.30.127.254238.30.127.25516,382
123238.30.128.0/18238.30.128.1 to 238.30.191.254238.30.191.25516,382
124238.30.192.0/18238.30.192.1 to 238.30.255.254238.30.255.25516,382
125238.31.0.0/18238.31.0.1 to 238.31.63.254238.31.63.25516,382
126238.31.64.0/18238.31.64.1 to 238.31.127.254238.31.127.25516,382
127238.31.128.0/18238.31.128.1 to 238.31.191.254238.31.191.25516,382
128238.31.192.0/18238.31.192.1 to 238.31.255.254238.31.255.25516,382
129238.32.0.0/18238.32.0.1 to 238.32.63.254238.32.63.25516,382
130238.32.64.0/18238.32.64.1 to 238.32.127.254238.32.127.25516,382
131238.32.128.0/18238.32.128.1 to 238.32.191.254238.32.191.25516,382
132238.32.192.0/18238.32.192.1 to 238.32.255.254238.32.255.25516,382
133238.33.0.0/18238.33.0.1 to 238.33.63.254238.33.63.25516,382
134238.33.64.0/18238.33.64.1 to 238.33.127.254238.33.127.25516,382
135238.33.128.0/18238.33.128.1 to 238.33.191.254238.33.191.25516,382
136238.33.192.0/18238.33.192.1 to 238.33.255.254238.33.255.25516,382
137238.34.0.0/18238.34.0.1 to 238.34.63.254238.34.63.25516,382
138238.34.64.0/18238.34.64.1 to 238.34.127.254238.34.127.25516,382
139238.34.128.0/18238.34.128.1 to 238.34.191.254238.34.191.25516,382
140238.34.192.0/18238.34.192.1 to 238.34.255.254238.34.255.25516,382
141238.35.0.0/18238.35.0.1 to 238.35.63.254238.35.63.25516,382
142238.35.64.0/18238.35.64.1 to 238.35.127.254238.35.127.25516,382
143238.35.128.0/18238.35.128.1 to 238.35.191.254238.35.191.25516,382
144238.35.192.0/18238.35.192.1 to 238.35.255.254238.35.255.25516,382
145238.36.0.0/18238.36.0.1 to 238.36.63.254238.36.63.25516,382
146238.36.64.0/18238.36.64.1 to 238.36.127.254238.36.127.25516,382
147238.36.128.0/18238.36.128.1 to 238.36.191.254238.36.191.25516,382
148238.36.192.0/18238.36.192.1 to 238.36.255.254238.36.255.25516,382
149238.37.0.0/18238.37.0.1 to 238.37.63.254238.37.63.25516,382
150238.37.64.0/18238.37.64.1 to 238.37.127.254238.37.127.25516,382
151238.37.128.0/18238.37.128.1 to 238.37.191.254238.37.191.25516,382
152238.37.192.0/18238.37.192.1 to 238.37.255.254238.37.255.25516,382
153238.38.0.0/18238.38.0.1 to 238.38.63.254238.38.63.25516,382
154238.38.64.0/18238.38.64.1 to 238.38.127.254238.38.127.25516,382
155238.38.128.0/18238.38.128.1 to 238.38.191.254238.38.191.25516,382
156238.38.192.0/18238.38.192.1 to 238.38.255.254238.38.255.25516,382
157238.39.0.0/18238.39.0.1 to 238.39.63.254238.39.63.25516,382
158238.39.64.0/18238.39.64.1 to 238.39.127.254238.39.127.25516,382
159238.39.128.0/18238.39.128.1 to 238.39.191.254238.39.191.25516,382
160238.39.192.0/18238.39.192.1 to 238.39.255.254238.39.255.25516,382
161238.40.0.0/18238.40.0.1 to 238.40.63.254238.40.63.25516,382
162238.40.64.0/18238.40.64.1 to 238.40.127.254238.40.127.25516,382
163238.40.128.0/18238.40.128.1 to 238.40.191.254238.40.191.25516,382
164238.40.192.0/18238.40.192.1 to 238.40.255.254238.40.255.25516,382
165238.41.0.0/18238.41.0.1 to 238.41.63.254238.41.63.25516,382
166238.41.64.0/18238.41.64.1 to 238.41.127.254238.41.127.25516,382
167238.41.128.0/18238.41.128.1 to 238.41.191.254238.41.191.25516,382
168238.41.192.0/18238.41.192.1 to 238.41.255.254238.41.255.25516,382
169238.42.0.0/18238.42.0.1 to 238.42.63.254238.42.63.25516,382
170238.42.64.0/18238.42.64.1 to 238.42.127.254238.42.127.25516,382
171238.42.128.0/18238.42.128.1 to 238.42.191.254238.42.191.25516,382
172238.42.192.0/18238.42.192.1 to 238.42.255.254238.42.255.25516,382
173238.43.0.0/18238.43.0.1 to 238.43.63.254238.43.63.25516,382
174238.43.64.0/18238.43.64.1 to 238.43.127.254238.43.127.25516,382
175238.43.128.0/18238.43.128.1 to 238.43.191.254238.43.191.25516,382
176238.43.192.0/18238.43.192.1 to 238.43.255.254238.43.255.25516,382
177238.44.0.0/18238.44.0.1 to 238.44.63.254238.44.63.25516,382
178238.44.64.0/18238.44.64.1 to 238.44.127.254238.44.127.25516,382
179238.44.128.0/18238.44.128.1 to 238.44.191.254238.44.191.25516,382
180238.44.192.0/18238.44.192.1 to 238.44.255.254238.44.255.25516,382
181238.45.0.0/18238.45.0.1 to 238.45.63.254238.45.63.25516,382
182238.45.64.0/18238.45.64.1 to 238.45.127.254238.45.127.25516,382
183238.45.128.0/18238.45.128.1 to 238.45.191.254238.45.191.25516,382
184238.45.192.0/18238.45.192.1 to 238.45.255.254238.45.255.25516,382
185238.46.0.0/18238.46.0.1 to 238.46.63.254238.46.63.25516,382
186238.46.64.0/18238.46.64.1 to 238.46.127.254238.46.127.25516,382
187238.46.128.0/18238.46.128.1 to 238.46.191.254238.46.191.25516,382
188238.46.192.0/18238.46.192.1 to 238.46.255.254238.46.255.25516,382
189238.47.0.0/18238.47.0.1 to 238.47.63.254238.47.63.25516,382
190238.47.64.0/18238.47.64.1 to 238.47.127.254238.47.127.25516,382
191238.47.128.0/18238.47.128.1 to 238.47.191.254238.47.191.25516,382
192238.47.192.0/18238.47.192.1 to 238.47.255.254238.47.255.25516,382
193238.48.0.0/18238.48.0.1 to 238.48.63.254238.48.63.25516,382
194238.48.64.0/18238.48.64.1 to 238.48.127.254238.48.127.25516,382
195238.48.128.0/18238.48.128.1 to 238.48.191.254238.48.191.25516,382
196238.48.192.0/18238.48.192.1 to 238.48.255.254238.48.255.25516,382
197238.49.0.0/18238.49.0.1 to 238.49.63.254238.49.63.25516,382
198238.49.64.0/18238.49.64.1 to 238.49.127.254238.49.127.25516,382
199238.49.128.0/18238.49.128.1 to 238.49.191.254238.49.191.25516,382
200238.49.192.0/18238.49.192.1 to 238.49.255.254238.49.255.25516,382
201238.50.0.0/18238.50.0.1 to 238.50.63.254238.50.63.25516,382
202238.50.64.0/18238.50.64.1 to 238.50.127.254238.50.127.25516,382
203238.50.128.0/18238.50.128.1 to 238.50.191.254238.50.191.25516,382
204238.50.192.0/18238.50.192.1 to 238.50.255.254238.50.255.25516,382
205238.51.0.0/18238.51.0.1 to 238.51.63.254238.51.63.25516,382
206238.51.64.0/18238.51.64.1 to 238.51.127.254238.51.127.25516,382
207238.51.128.0/18238.51.128.1 to 238.51.191.254238.51.191.25516,382
208238.51.192.0/18238.51.192.1 to 238.51.255.254238.51.255.25516,382
209238.52.0.0/18238.52.0.1 to 238.52.63.254238.52.63.25516,382
210238.52.64.0/18238.52.64.1 to 238.52.127.254238.52.127.25516,382
211238.52.128.0/18238.52.128.1 to 238.52.191.254238.52.191.25516,382
212238.52.192.0/18238.52.192.1 to 238.52.255.254238.52.255.25516,382
213238.53.0.0/18238.53.0.1 to 238.53.63.254238.53.63.25516,382
214238.53.64.0/18238.53.64.1 to 238.53.127.254238.53.127.25516,382
215238.53.128.0/18238.53.128.1 to 238.53.191.254238.53.191.25516,382
216238.53.192.0/18238.53.192.1 to 238.53.255.254238.53.255.25516,382
217238.54.0.0/18238.54.0.1 to 238.54.63.254238.54.63.25516,382
218238.54.64.0/18238.54.64.1 to 238.54.127.254238.54.127.25516,382
219238.54.128.0/18238.54.128.1 to 238.54.191.254238.54.191.25516,382
220238.54.192.0/18238.54.192.1 to 238.54.255.254238.54.255.25516,382
221238.55.0.0/18238.55.0.1 to 238.55.63.254238.55.63.25516,382
222238.55.64.0/18238.55.64.1 to 238.55.127.254238.55.127.25516,382
223238.55.128.0/18238.55.128.1 to 238.55.191.254238.55.191.25516,382
224238.55.192.0/18238.55.192.1 to 238.55.255.254238.55.255.25516,382
225238.56.0.0/18238.56.0.1 to 238.56.63.254238.56.63.25516,382
226238.56.64.0/18238.56.64.1 to 238.56.127.254238.56.127.25516,382
227238.56.128.0/18238.56.128.1 to 238.56.191.254238.56.191.25516,382
228238.56.192.0/18238.56.192.1 to 238.56.255.254238.56.255.25516,382
229238.57.0.0/18238.57.0.1 to 238.57.63.254238.57.63.25516,382
230238.57.64.0/18238.57.64.1 to 238.57.127.254238.57.127.25516,382
231238.57.128.0/18238.57.128.1 to 238.57.191.254238.57.191.25516,382
232238.57.192.0/18238.57.192.1 to 238.57.255.254238.57.255.25516,382
233238.58.0.0/18238.58.0.1 to 238.58.63.254238.58.63.25516,382
234238.58.64.0/18238.58.64.1 to 238.58.127.254238.58.127.25516,382
235238.58.128.0/18238.58.128.1 to 238.58.191.254238.58.191.25516,382
236238.58.192.0/18238.58.192.1 to 238.58.255.254238.58.255.25516,382
237238.59.0.0/18238.59.0.1 to 238.59.63.254238.59.63.25516,382
238238.59.64.0/18238.59.64.1 to 238.59.127.254238.59.127.25516,382
239238.59.128.0/18238.59.128.1 to 238.59.191.254238.59.191.25516,382
240238.59.192.0/18238.59.192.1 to 238.59.255.254238.59.255.25516,382
241238.60.0.0/18238.60.0.1 to 238.60.63.254238.60.63.25516,382
242238.60.64.0/18238.60.64.1 to 238.60.127.254238.60.127.25516,382
243238.60.128.0/18238.60.128.1 to 238.60.191.254238.60.191.25516,382
244238.60.192.0/18238.60.192.1 to 238.60.255.254238.60.255.25516,382
245238.61.0.0/18238.61.0.1 to 238.61.63.254238.61.63.25516,382
246238.61.64.0/18238.61.64.1 to 238.61.127.254238.61.127.25516,382
247238.61.128.0/18238.61.128.1 to 238.61.191.254238.61.191.25516,382
248238.61.192.0/18238.61.192.1 to 238.61.255.254238.61.255.25516,382
249238.62.0.0/18238.62.0.1 to 238.62.63.254238.62.63.25516,382
250238.62.64.0/18238.62.64.1 to 238.62.127.254238.62.127.25516,382
251238.62.128.0/18238.62.128.1 to 238.62.191.254238.62.191.25516,382
252238.62.192.0/18238.62.192.1 to 238.62.255.254238.62.255.25516,382
253238.63.0.0/18238.63.0.1 to 238.63.63.254238.63.63.25516,382
254238.63.64.0/18238.63.64.1 to 238.63.127.254238.63.127.25516,382
255238.63.128.0/18238.63.128.1 to 238.63.191.254238.63.191.25516,382
256238.63.192.0/18238.63.192.1 to 238.63.255.254238.63.255.25516,382

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.