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.

Network238.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
238.128.0.0
Broadcast address
238.255.255.255
First usable
238.128.0.1
Last usable
238.255.255.254
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 EE800000 · Integer 4001366016 to 4009754623
Reverse DNS zones
128.238.in-addr.arpa
129.238.in-addr.arpa
130.238.in-addr.arpa
131.238.in-addr.arpa
132.238.in-addr.arpa
133.238.in-addr.arpa
134.238.in-addr.arpa
135.238.in-addr.arpa
136.238.in-addr.arpa
137.238.in-addr.arpa
138.238.in-addr.arpa
139.238.in-addr.arpa
140.238.in-addr.arpa
141.238.in-addr.arpa
142.238.in-addr.arpa
143.238.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
Address11101110.10000000.00000000.00000000238.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network11101110.10000000.00000000.00000000238.128.0.0
Broadcast11101110.11111111.11111111.11111111238.255.255.255
Split into smaller subnets/21
/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)

238.128.0.0/9 makes 4,096 subnets of /21; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1238.128.0.0/21238.128.0.1 to 238.128.7.254238.128.7.2552,046
2238.128.8.0/21238.128.8.1 to 238.128.15.254238.128.15.2552,046
3238.128.16.0/21238.128.16.1 to 238.128.23.254238.128.23.2552,046
4238.128.24.0/21238.128.24.1 to 238.128.31.254238.128.31.2552,046
5238.128.32.0/21238.128.32.1 to 238.128.39.254238.128.39.2552,046
6238.128.40.0/21238.128.40.1 to 238.128.47.254238.128.47.2552,046
7238.128.48.0/21238.128.48.1 to 238.128.55.254238.128.55.2552,046
8238.128.56.0/21238.128.56.1 to 238.128.63.254238.128.63.2552,046
9238.128.64.0/21238.128.64.1 to 238.128.71.254238.128.71.2552,046
10238.128.72.0/21238.128.72.1 to 238.128.79.254238.128.79.2552,046
11238.128.80.0/21238.128.80.1 to 238.128.87.254238.128.87.2552,046
12238.128.88.0/21238.128.88.1 to 238.128.95.254238.128.95.2552,046
13238.128.96.0/21238.128.96.1 to 238.128.103.254238.128.103.2552,046
14238.128.104.0/21238.128.104.1 to 238.128.111.254238.128.111.2552,046
15238.128.112.0/21238.128.112.1 to 238.128.119.254238.128.119.2552,046
16238.128.120.0/21238.128.120.1 to 238.128.127.254238.128.127.2552,046
17238.128.128.0/21238.128.128.1 to 238.128.135.254238.128.135.2552,046
18238.128.136.0/21238.128.136.1 to 238.128.143.254238.128.143.2552,046
19238.128.144.0/21238.128.144.1 to 238.128.151.254238.128.151.2552,046
20238.128.152.0/21238.128.152.1 to 238.128.159.254238.128.159.2552,046
21238.128.160.0/21238.128.160.1 to 238.128.167.254238.128.167.2552,046
22238.128.168.0/21238.128.168.1 to 238.128.175.254238.128.175.2552,046
23238.128.176.0/21238.128.176.1 to 238.128.183.254238.128.183.2552,046
24238.128.184.0/21238.128.184.1 to 238.128.191.254238.128.191.2552,046
25238.128.192.0/21238.128.192.1 to 238.128.199.254238.128.199.2552,046
26238.128.200.0/21238.128.200.1 to 238.128.207.254238.128.207.2552,046
27238.128.208.0/21238.128.208.1 to 238.128.215.254238.128.215.2552,046
28238.128.216.0/21238.128.216.1 to 238.128.223.254238.128.223.2552,046
29238.128.224.0/21238.128.224.1 to 238.128.231.254238.128.231.2552,046
30238.128.232.0/21238.128.232.1 to 238.128.239.254238.128.239.2552,046
31238.128.240.0/21238.128.240.1 to 238.128.247.254238.128.247.2552,046
32238.128.248.0/21238.128.248.1 to 238.128.255.254238.128.255.2552,046
33238.129.0.0/21238.129.0.1 to 238.129.7.254238.129.7.2552,046
34238.129.8.0/21238.129.8.1 to 238.129.15.254238.129.15.2552,046
35238.129.16.0/21238.129.16.1 to 238.129.23.254238.129.23.2552,046
36238.129.24.0/21238.129.24.1 to 238.129.31.254238.129.31.2552,046
37238.129.32.0/21238.129.32.1 to 238.129.39.254238.129.39.2552,046
38238.129.40.0/21238.129.40.1 to 238.129.47.254238.129.47.2552,046
39238.129.48.0/21238.129.48.1 to 238.129.55.254238.129.55.2552,046
40238.129.56.0/21238.129.56.1 to 238.129.63.254238.129.63.2552,046
41238.129.64.0/21238.129.64.1 to 238.129.71.254238.129.71.2552,046
42238.129.72.0/21238.129.72.1 to 238.129.79.254238.129.79.2552,046
43238.129.80.0/21238.129.80.1 to 238.129.87.254238.129.87.2552,046
44238.129.88.0/21238.129.88.1 to 238.129.95.254238.129.95.2552,046
45238.129.96.0/21238.129.96.1 to 238.129.103.254238.129.103.2552,046
46238.129.104.0/21238.129.104.1 to 238.129.111.254238.129.111.2552,046
47238.129.112.0/21238.129.112.1 to 238.129.119.254238.129.119.2552,046
48238.129.120.0/21238.129.120.1 to 238.129.127.254238.129.127.2552,046
49238.129.128.0/21238.129.128.1 to 238.129.135.254238.129.135.2552,046
50238.129.136.0/21238.129.136.1 to 238.129.143.254238.129.143.2552,046
51238.129.144.0/21238.129.144.1 to 238.129.151.254238.129.151.2552,046
52238.129.152.0/21238.129.152.1 to 238.129.159.254238.129.159.2552,046
53238.129.160.0/21238.129.160.1 to 238.129.167.254238.129.167.2552,046
54238.129.168.0/21238.129.168.1 to 238.129.175.254238.129.175.2552,046
55238.129.176.0/21238.129.176.1 to 238.129.183.254238.129.183.2552,046
56238.129.184.0/21238.129.184.1 to 238.129.191.254238.129.191.2552,046
57238.129.192.0/21238.129.192.1 to 238.129.199.254238.129.199.2552,046
58238.129.200.0/21238.129.200.1 to 238.129.207.254238.129.207.2552,046
59238.129.208.0/21238.129.208.1 to 238.129.215.254238.129.215.2552,046
60238.129.216.0/21238.129.216.1 to 238.129.223.254238.129.223.2552,046
61238.129.224.0/21238.129.224.1 to 238.129.231.254238.129.231.2552,046
62238.129.232.0/21238.129.232.1 to 238.129.239.254238.129.239.2552,046
63238.129.240.0/21238.129.240.1 to 238.129.247.254238.129.247.2552,046
64238.129.248.0/21238.129.248.1 to 238.129.255.254238.129.255.2552,046
65238.130.0.0/21238.130.0.1 to 238.130.7.254238.130.7.2552,046
66238.130.8.0/21238.130.8.1 to 238.130.15.254238.130.15.2552,046
67238.130.16.0/21238.130.16.1 to 238.130.23.254238.130.23.2552,046
68238.130.24.0/21238.130.24.1 to 238.130.31.254238.130.31.2552,046
69238.130.32.0/21238.130.32.1 to 238.130.39.254238.130.39.2552,046
70238.130.40.0/21238.130.40.1 to 238.130.47.254238.130.47.2552,046
71238.130.48.0/21238.130.48.1 to 238.130.55.254238.130.55.2552,046
72238.130.56.0/21238.130.56.1 to 238.130.63.254238.130.63.2552,046
73238.130.64.0/21238.130.64.1 to 238.130.71.254238.130.71.2552,046
74238.130.72.0/21238.130.72.1 to 238.130.79.254238.130.79.2552,046
75238.130.80.0/21238.130.80.1 to 238.130.87.254238.130.87.2552,046
76238.130.88.0/21238.130.88.1 to 238.130.95.254238.130.95.2552,046
77238.130.96.0/21238.130.96.1 to 238.130.103.254238.130.103.2552,046
78238.130.104.0/21238.130.104.1 to 238.130.111.254238.130.111.2552,046
79238.130.112.0/21238.130.112.1 to 238.130.119.254238.130.119.2552,046
80238.130.120.0/21238.130.120.1 to 238.130.127.254238.130.127.2552,046
81238.130.128.0/21238.130.128.1 to 238.130.135.254238.130.135.2552,046
82238.130.136.0/21238.130.136.1 to 238.130.143.254238.130.143.2552,046
83238.130.144.0/21238.130.144.1 to 238.130.151.254238.130.151.2552,046
84238.130.152.0/21238.130.152.1 to 238.130.159.254238.130.159.2552,046
85238.130.160.0/21238.130.160.1 to 238.130.167.254238.130.167.2552,046
86238.130.168.0/21238.130.168.1 to 238.130.175.254238.130.175.2552,046
87238.130.176.0/21238.130.176.1 to 238.130.183.254238.130.183.2552,046
88238.130.184.0/21238.130.184.1 to 238.130.191.254238.130.191.2552,046
89238.130.192.0/21238.130.192.1 to 238.130.199.254238.130.199.2552,046
90238.130.200.0/21238.130.200.1 to 238.130.207.254238.130.207.2552,046
91238.130.208.0/21238.130.208.1 to 238.130.215.254238.130.215.2552,046
92238.130.216.0/21238.130.216.1 to 238.130.223.254238.130.223.2552,046
93238.130.224.0/21238.130.224.1 to 238.130.231.254238.130.231.2552,046
94238.130.232.0/21238.130.232.1 to 238.130.239.254238.130.239.2552,046
95238.130.240.0/21238.130.240.1 to 238.130.247.254238.130.247.2552,046
96238.130.248.0/21238.130.248.1 to 238.130.255.254238.130.255.2552,046
97238.131.0.0/21238.131.0.1 to 238.131.7.254238.131.7.2552,046
98238.131.8.0/21238.131.8.1 to 238.131.15.254238.131.15.2552,046
99238.131.16.0/21238.131.16.1 to 238.131.23.254238.131.23.2552,046
100238.131.24.0/21238.131.24.1 to 238.131.31.254238.131.31.2552,046
101238.131.32.0/21238.131.32.1 to 238.131.39.254238.131.39.2552,046
102238.131.40.0/21238.131.40.1 to 238.131.47.254238.131.47.2552,046
103238.131.48.0/21238.131.48.1 to 238.131.55.254238.131.55.2552,046
104238.131.56.0/21238.131.56.1 to 238.131.63.254238.131.63.2552,046
105238.131.64.0/21238.131.64.1 to 238.131.71.254238.131.71.2552,046
106238.131.72.0/21238.131.72.1 to 238.131.79.254238.131.79.2552,046
107238.131.80.0/21238.131.80.1 to 238.131.87.254238.131.87.2552,046
108238.131.88.0/21238.131.88.1 to 238.131.95.254238.131.95.2552,046
109238.131.96.0/21238.131.96.1 to 238.131.103.254238.131.103.2552,046
110238.131.104.0/21238.131.104.1 to 238.131.111.254238.131.111.2552,046
111238.131.112.0/21238.131.112.1 to 238.131.119.254238.131.119.2552,046
112238.131.120.0/21238.131.120.1 to 238.131.127.254238.131.127.2552,046
113238.131.128.0/21238.131.128.1 to 238.131.135.254238.131.135.2552,046
114238.131.136.0/21238.131.136.1 to 238.131.143.254238.131.143.2552,046
115238.131.144.0/21238.131.144.1 to 238.131.151.254238.131.151.2552,046
116238.131.152.0/21238.131.152.1 to 238.131.159.254238.131.159.2552,046
117238.131.160.0/21238.131.160.1 to 238.131.167.254238.131.167.2552,046
118238.131.168.0/21238.131.168.1 to 238.131.175.254238.131.175.2552,046
119238.131.176.0/21238.131.176.1 to 238.131.183.254238.131.183.2552,046
120238.131.184.0/21238.131.184.1 to 238.131.191.254238.131.191.2552,046
121238.131.192.0/21238.131.192.1 to 238.131.199.254238.131.199.2552,046
122238.131.200.0/21238.131.200.1 to 238.131.207.254238.131.207.2552,046
123238.131.208.0/21238.131.208.1 to 238.131.215.254238.131.215.2552,046
124238.131.216.0/21238.131.216.1 to 238.131.223.254238.131.223.2552,046
125238.131.224.0/21238.131.224.1 to 238.131.231.254238.131.231.2552,046
126238.131.232.0/21238.131.232.1 to 238.131.239.254238.131.239.2552,046
127238.131.240.0/21238.131.240.1 to 238.131.247.254238.131.247.2552,046
128238.131.248.0/21238.131.248.1 to 238.131.255.254238.131.255.2552,046
129238.132.0.0/21238.132.0.1 to 238.132.7.254238.132.7.2552,046
130238.132.8.0/21238.132.8.1 to 238.132.15.254238.132.15.2552,046
131238.132.16.0/21238.132.16.1 to 238.132.23.254238.132.23.2552,046
132238.132.24.0/21238.132.24.1 to 238.132.31.254238.132.31.2552,046
133238.132.32.0/21238.132.32.1 to 238.132.39.254238.132.39.2552,046
134238.132.40.0/21238.132.40.1 to 238.132.47.254238.132.47.2552,046
135238.132.48.0/21238.132.48.1 to 238.132.55.254238.132.55.2552,046
136238.132.56.0/21238.132.56.1 to 238.132.63.254238.132.63.2552,046
137238.132.64.0/21238.132.64.1 to 238.132.71.254238.132.71.2552,046
138238.132.72.0/21238.132.72.1 to 238.132.79.254238.132.79.2552,046
139238.132.80.0/21238.132.80.1 to 238.132.87.254238.132.87.2552,046
140238.132.88.0/21238.132.88.1 to 238.132.95.254238.132.95.2552,046
141238.132.96.0/21238.132.96.1 to 238.132.103.254238.132.103.2552,046
142238.132.104.0/21238.132.104.1 to 238.132.111.254238.132.111.2552,046
143238.132.112.0/21238.132.112.1 to 238.132.119.254238.132.119.2552,046
144238.132.120.0/21238.132.120.1 to 238.132.127.254238.132.127.2552,046
145238.132.128.0/21238.132.128.1 to 238.132.135.254238.132.135.2552,046
146238.132.136.0/21238.132.136.1 to 238.132.143.254238.132.143.2552,046
147238.132.144.0/21238.132.144.1 to 238.132.151.254238.132.151.2552,046
148238.132.152.0/21238.132.152.1 to 238.132.159.254238.132.159.2552,046
149238.132.160.0/21238.132.160.1 to 238.132.167.254238.132.167.2552,046
150238.132.168.0/21238.132.168.1 to 238.132.175.254238.132.175.2552,046
151238.132.176.0/21238.132.176.1 to 238.132.183.254238.132.183.2552,046
152238.132.184.0/21238.132.184.1 to 238.132.191.254238.132.191.2552,046
153238.132.192.0/21238.132.192.1 to 238.132.199.254238.132.199.2552,046
154238.132.200.0/21238.132.200.1 to 238.132.207.254238.132.207.2552,046
155238.132.208.0/21238.132.208.1 to 238.132.215.254238.132.215.2552,046
156238.132.216.0/21238.132.216.1 to 238.132.223.254238.132.223.2552,046
157238.132.224.0/21238.132.224.1 to 238.132.231.254238.132.231.2552,046
158238.132.232.0/21238.132.232.1 to 238.132.239.254238.132.239.2552,046
159238.132.240.0/21238.132.240.1 to 238.132.247.254238.132.247.2552,046
160238.132.248.0/21238.132.248.1 to 238.132.255.254238.132.255.2552,046
161238.133.0.0/21238.133.0.1 to 238.133.7.254238.133.7.2552,046
162238.133.8.0/21238.133.8.1 to 238.133.15.254238.133.15.2552,046
163238.133.16.0/21238.133.16.1 to 238.133.23.254238.133.23.2552,046
164238.133.24.0/21238.133.24.1 to 238.133.31.254238.133.31.2552,046
165238.133.32.0/21238.133.32.1 to 238.133.39.254238.133.39.2552,046
166238.133.40.0/21238.133.40.1 to 238.133.47.254238.133.47.2552,046
167238.133.48.0/21238.133.48.1 to 238.133.55.254238.133.55.2552,046
168238.133.56.0/21238.133.56.1 to 238.133.63.254238.133.63.2552,046
169238.133.64.0/21238.133.64.1 to 238.133.71.254238.133.71.2552,046
170238.133.72.0/21238.133.72.1 to 238.133.79.254238.133.79.2552,046
171238.133.80.0/21238.133.80.1 to 238.133.87.254238.133.87.2552,046
172238.133.88.0/21238.133.88.1 to 238.133.95.254238.133.95.2552,046
173238.133.96.0/21238.133.96.1 to 238.133.103.254238.133.103.2552,046
174238.133.104.0/21238.133.104.1 to 238.133.111.254238.133.111.2552,046
175238.133.112.0/21238.133.112.1 to 238.133.119.254238.133.119.2552,046
176238.133.120.0/21238.133.120.1 to 238.133.127.254238.133.127.2552,046
177238.133.128.0/21238.133.128.1 to 238.133.135.254238.133.135.2552,046
178238.133.136.0/21238.133.136.1 to 238.133.143.254238.133.143.2552,046
179238.133.144.0/21238.133.144.1 to 238.133.151.254238.133.151.2552,046
180238.133.152.0/21238.133.152.1 to 238.133.159.254238.133.159.2552,046
181238.133.160.0/21238.133.160.1 to 238.133.167.254238.133.167.2552,046
182238.133.168.0/21238.133.168.1 to 238.133.175.254238.133.175.2552,046
183238.133.176.0/21238.133.176.1 to 238.133.183.254238.133.183.2552,046
184238.133.184.0/21238.133.184.1 to 238.133.191.254238.133.191.2552,046
185238.133.192.0/21238.133.192.1 to 238.133.199.254238.133.199.2552,046
186238.133.200.0/21238.133.200.1 to 238.133.207.254238.133.207.2552,046
187238.133.208.0/21238.133.208.1 to 238.133.215.254238.133.215.2552,046
188238.133.216.0/21238.133.216.1 to 238.133.223.254238.133.223.2552,046
189238.133.224.0/21238.133.224.1 to 238.133.231.254238.133.231.2552,046
190238.133.232.0/21238.133.232.1 to 238.133.239.254238.133.239.2552,046
191238.133.240.0/21238.133.240.1 to 238.133.247.254238.133.247.2552,046
192238.133.248.0/21238.133.248.1 to 238.133.255.254238.133.255.2552,046
193238.134.0.0/21238.134.0.1 to 238.134.7.254238.134.7.2552,046
194238.134.8.0/21238.134.8.1 to 238.134.15.254238.134.15.2552,046
195238.134.16.0/21238.134.16.1 to 238.134.23.254238.134.23.2552,046
196238.134.24.0/21238.134.24.1 to 238.134.31.254238.134.31.2552,046
197238.134.32.0/21238.134.32.1 to 238.134.39.254238.134.39.2552,046
198238.134.40.0/21238.134.40.1 to 238.134.47.254238.134.47.2552,046
199238.134.48.0/21238.134.48.1 to 238.134.55.254238.134.55.2552,046
200238.134.56.0/21238.134.56.1 to 238.134.63.254238.134.63.2552,046
201238.134.64.0/21238.134.64.1 to 238.134.71.254238.134.71.2552,046
202238.134.72.0/21238.134.72.1 to 238.134.79.254238.134.79.2552,046
203238.134.80.0/21238.134.80.1 to 238.134.87.254238.134.87.2552,046
204238.134.88.0/21238.134.88.1 to 238.134.95.254238.134.95.2552,046
205238.134.96.0/21238.134.96.1 to 238.134.103.254238.134.103.2552,046
206238.134.104.0/21238.134.104.1 to 238.134.111.254238.134.111.2552,046
207238.134.112.0/21238.134.112.1 to 238.134.119.254238.134.119.2552,046
208238.134.120.0/21238.134.120.1 to 238.134.127.254238.134.127.2552,046
209238.134.128.0/21238.134.128.1 to 238.134.135.254238.134.135.2552,046
210238.134.136.0/21238.134.136.1 to 238.134.143.254238.134.143.2552,046
211238.134.144.0/21238.134.144.1 to 238.134.151.254238.134.151.2552,046
212238.134.152.0/21238.134.152.1 to 238.134.159.254238.134.159.2552,046
213238.134.160.0/21238.134.160.1 to 238.134.167.254238.134.167.2552,046
214238.134.168.0/21238.134.168.1 to 238.134.175.254238.134.175.2552,046
215238.134.176.0/21238.134.176.1 to 238.134.183.254238.134.183.2552,046
216238.134.184.0/21238.134.184.1 to 238.134.191.254238.134.191.2552,046
217238.134.192.0/21238.134.192.1 to 238.134.199.254238.134.199.2552,046
218238.134.200.0/21238.134.200.1 to 238.134.207.254238.134.207.2552,046
219238.134.208.0/21238.134.208.1 to 238.134.215.254238.134.215.2552,046
220238.134.216.0/21238.134.216.1 to 238.134.223.254238.134.223.2552,046
221238.134.224.0/21238.134.224.1 to 238.134.231.254238.134.231.2552,046
222238.134.232.0/21238.134.232.1 to 238.134.239.254238.134.239.2552,046
223238.134.240.0/21238.134.240.1 to 238.134.247.254238.134.247.2552,046
224238.134.248.0/21238.134.248.1 to 238.134.255.254238.134.255.2552,046
225238.135.0.0/21238.135.0.1 to 238.135.7.254238.135.7.2552,046
226238.135.8.0/21238.135.8.1 to 238.135.15.254238.135.15.2552,046
227238.135.16.0/21238.135.16.1 to 238.135.23.254238.135.23.2552,046
228238.135.24.0/21238.135.24.1 to 238.135.31.254238.135.31.2552,046
229238.135.32.0/21238.135.32.1 to 238.135.39.254238.135.39.2552,046
230238.135.40.0/21238.135.40.1 to 238.135.47.254238.135.47.2552,046
231238.135.48.0/21238.135.48.1 to 238.135.55.254238.135.55.2552,046
232238.135.56.0/21238.135.56.1 to 238.135.63.254238.135.63.2552,046
233238.135.64.0/21238.135.64.1 to 238.135.71.254238.135.71.2552,046
234238.135.72.0/21238.135.72.1 to 238.135.79.254238.135.79.2552,046
235238.135.80.0/21238.135.80.1 to 238.135.87.254238.135.87.2552,046
236238.135.88.0/21238.135.88.1 to 238.135.95.254238.135.95.2552,046
237238.135.96.0/21238.135.96.1 to 238.135.103.254238.135.103.2552,046
238238.135.104.0/21238.135.104.1 to 238.135.111.254238.135.111.2552,046
239238.135.112.0/21238.135.112.1 to 238.135.119.254238.135.119.2552,046
240238.135.120.0/21238.135.120.1 to 238.135.127.254238.135.127.2552,046
241238.135.128.0/21238.135.128.1 to 238.135.135.254238.135.135.2552,046
242238.135.136.0/21238.135.136.1 to 238.135.143.254238.135.143.2552,046
243238.135.144.0/21238.135.144.1 to 238.135.151.254238.135.151.2552,046
244238.135.152.0/21238.135.152.1 to 238.135.159.254238.135.159.2552,046
245238.135.160.0/21238.135.160.1 to 238.135.167.254238.135.167.2552,046
246238.135.168.0/21238.135.168.1 to 238.135.175.254238.135.175.2552,046
247238.135.176.0/21238.135.176.1 to 238.135.183.254238.135.183.2552,046
248238.135.184.0/21238.135.184.1 to 238.135.191.254238.135.191.2552,046
249238.135.192.0/21238.135.192.1 to 238.135.199.254238.135.199.2552,046
250238.135.200.0/21238.135.200.1 to 238.135.207.254238.135.207.2552,046
251238.135.208.0/21238.135.208.1 to 238.135.215.254238.135.215.2552,046
252238.135.216.0/21238.135.216.1 to 238.135.223.254238.135.223.2552,046
253238.135.224.0/21238.135.224.1 to 238.135.231.254238.135.231.2552,046
254238.135.232.0/21238.135.232.1 to 238.135.239.254238.135.239.2552,046
255238.135.240.0/21238.135.240.1 to 238.135.247.254238.135.247.2552,046
256238.135.248.0/21238.135.248.1 to 238.135.255.254238.135.255.2552,046

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.