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.

Network252.192.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
252.192.0.0
Broadcast address
252.255.255.255
First usable
252.192.0.1
Last usable
252.255.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex FCC00000 · Integer 4240441344 to 4244635647
Reverse DNS zones
192.252.in-addr.arpa
193.252.in-addr.arpa
194.252.in-addr.arpa
195.252.in-addr.arpa
196.252.in-addr.arpa
197.252.in-addr.arpa
198.252.in-addr.arpa
199.252.in-addr.arpa
200.252.in-addr.arpa
201.252.in-addr.arpa
202.252.in-addr.arpa
203.252.in-addr.arpa
204.252.in-addr.arpa
205.252.in-addr.arpa
206.252.in-addr.arpa
207.252.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11111100.11000000.00000000.00000000252.192.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network11111100.11000000.00000000.00000000252.192.0.0
Broadcast11111100.11111111.11111111.11111111252.255.255.255
Split into smaller subnets/19
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

252.192.0.0/10 makes 512 subnets of /19; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1252.192.0.0/19252.192.0.1 to 252.192.31.254252.192.31.2558,190
2252.192.32.0/19252.192.32.1 to 252.192.63.254252.192.63.2558,190
3252.192.64.0/19252.192.64.1 to 252.192.95.254252.192.95.2558,190
4252.192.96.0/19252.192.96.1 to 252.192.127.254252.192.127.2558,190
5252.192.128.0/19252.192.128.1 to 252.192.159.254252.192.159.2558,190
6252.192.160.0/19252.192.160.1 to 252.192.191.254252.192.191.2558,190
7252.192.192.0/19252.192.192.1 to 252.192.223.254252.192.223.2558,190
8252.192.224.0/19252.192.224.1 to 252.192.255.254252.192.255.2558,190
9252.193.0.0/19252.193.0.1 to 252.193.31.254252.193.31.2558,190
10252.193.32.0/19252.193.32.1 to 252.193.63.254252.193.63.2558,190
11252.193.64.0/19252.193.64.1 to 252.193.95.254252.193.95.2558,190
12252.193.96.0/19252.193.96.1 to 252.193.127.254252.193.127.2558,190
13252.193.128.0/19252.193.128.1 to 252.193.159.254252.193.159.2558,190
14252.193.160.0/19252.193.160.1 to 252.193.191.254252.193.191.2558,190
15252.193.192.0/19252.193.192.1 to 252.193.223.254252.193.223.2558,190
16252.193.224.0/19252.193.224.1 to 252.193.255.254252.193.255.2558,190
17252.194.0.0/19252.194.0.1 to 252.194.31.254252.194.31.2558,190
18252.194.32.0/19252.194.32.1 to 252.194.63.254252.194.63.2558,190
19252.194.64.0/19252.194.64.1 to 252.194.95.254252.194.95.2558,190
20252.194.96.0/19252.194.96.1 to 252.194.127.254252.194.127.2558,190
21252.194.128.0/19252.194.128.1 to 252.194.159.254252.194.159.2558,190
22252.194.160.0/19252.194.160.1 to 252.194.191.254252.194.191.2558,190
23252.194.192.0/19252.194.192.1 to 252.194.223.254252.194.223.2558,190
24252.194.224.0/19252.194.224.1 to 252.194.255.254252.194.255.2558,190
25252.195.0.0/19252.195.0.1 to 252.195.31.254252.195.31.2558,190
26252.195.32.0/19252.195.32.1 to 252.195.63.254252.195.63.2558,190
27252.195.64.0/19252.195.64.1 to 252.195.95.254252.195.95.2558,190
28252.195.96.0/19252.195.96.1 to 252.195.127.254252.195.127.2558,190
29252.195.128.0/19252.195.128.1 to 252.195.159.254252.195.159.2558,190
30252.195.160.0/19252.195.160.1 to 252.195.191.254252.195.191.2558,190
31252.195.192.0/19252.195.192.1 to 252.195.223.254252.195.223.2558,190
32252.195.224.0/19252.195.224.1 to 252.195.255.254252.195.255.2558,190
33252.196.0.0/19252.196.0.1 to 252.196.31.254252.196.31.2558,190
34252.196.32.0/19252.196.32.1 to 252.196.63.254252.196.63.2558,190
35252.196.64.0/19252.196.64.1 to 252.196.95.254252.196.95.2558,190
36252.196.96.0/19252.196.96.1 to 252.196.127.254252.196.127.2558,190
37252.196.128.0/19252.196.128.1 to 252.196.159.254252.196.159.2558,190
38252.196.160.0/19252.196.160.1 to 252.196.191.254252.196.191.2558,190
39252.196.192.0/19252.196.192.1 to 252.196.223.254252.196.223.2558,190
40252.196.224.0/19252.196.224.1 to 252.196.255.254252.196.255.2558,190
41252.197.0.0/19252.197.0.1 to 252.197.31.254252.197.31.2558,190
42252.197.32.0/19252.197.32.1 to 252.197.63.254252.197.63.2558,190
43252.197.64.0/19252.197.64.1 to 252.197.95.254252.197.95.2558,190
44252.197.96.0/19252.197.96.1 to 252.197.127.254252.197.127.2558,190
45252.197.128.0/19252.197.128.1 to 252.197.159.254252.197.159.2558,190
46252.197.160.0/19252.197.160.1 to 252.197.191.254252.197.191.2558,190
47252.197.192.0/19252.197.192.1 to 252.197.223.254252.197.223.2558,190
48252.197.224.0/19252.197.224.1 to 252.197.255.254252.197.255.2558,190
49252.198.0.0/19252.198.0.1 to 252.198.31.254252.198.31.2558,190
50252.198.32.0/19252.198.32.1 to 252.198.63.254252.198.63.2558,190
51252.198.64.0/19252.198.64.1 to 252.198.95.254252.198.95.2558,190
52252.198.96.0/19252.198.96.1 to 252.198.127.254252.198.127.2558,190
53252.198.128.0/19252.198.128.1 to 252.198.159.254252.198.159.2558,190
54252.198.160.0/19252.198.160.1 to 252.198.191.254252.198.191.2558,190
55252.198.192.0/19252.198.192.1 to 252.198.223.254252.198.223.2558,190
56252.198.224.0/19252.198.224.1 to 252.198.255.254252.198.255.2558,190
57252.199.0.0/19252.199.0.1 to 252.199.31.254252.199.31.2558,190
58252.199.32.0/19252.199.32.1 to 252.199.63.254252.199.63.2558,190
59252.199.64.0/19252.199.64.1 to 252.199.95.254252.199.95.2558,190
60252.199.96.0/19252.199.96.1 to 252.199.127.254252.199.127.2558,190
61252.199.128.0/19252.199.128.1 to 252.199.159.254252.199.159.2558,190
62252.199.160.0/19252.199.160.1 to 252.199.191.254252.199.191.2558,190
63252.199.192.0/19252.199.192.1 to 252.199.223.254252.199.223.2558,190
64252.199.224.0/19252.199.224.1 to 252.199.255.254252.199.255.2558,190
65252.200.0.0/19252.200.0.1 to 252.200.31.254252.200.31.2558,190
66252.200.32.0/19252.200.32.1 to 252.200.63.254252.200.63.2558,190
67252.200.64.0/19252.200.64.1 to 252.200.95.254252.200.95.2558,190
68252.200.96.0/19252.200.96.1 to 252.200.127.254252.200.127.2558,190
69252.200.128.0/19252.200.128.1 to 252.200.159.254252.200.159.2558,190
70252.200.160.0/19252.200.160.1 to 252.200.191.254252.200.191.2558,190
71252.200.192.0/19252.200.192.1 to 252.200.223.254252.200.223.2558,190
72252.200.224.0/19252.200.224.1 to 252.200.255.254252.200.255.2558,190
73252.201.0.0/19252.201.0.1 to 252.201.31.254252.201.31.2558,190
74252.201.32.0/19252.201.32.1 to 252.201.63.254252.201.63.2558,190
75252.201.64.0/19252.201.64.1 to 252.201.95.254252.201.95.2558,190
76252.201.96.0/19252.201.96.1 to 252.201.127.254252.201.127.2558,190
77252.201.128.0/19252.201.128.1 to 252.201.159.254252.201.159.2558,190
78252.201.160.0/19252.201.160.1 to 252.201.191.254252.201.191.2558,190
79252.201.192.0/19252.201.192.1 to 252.201.223.254252.201.223.2558,190
80252.201.224.0/19252.201.224.1 to 252.201.255.254252.201.255.2558,190
81252.202.0.0/19252.202.0.1 to 252.202.31.254252.202.31.2558,190
82252.202.32.0/19252.202.32.1 to 252.202.63.254252.202.63.2558,190
83252.202.64.0/19252.202.64.1 to 252.202.95.254252.202.95.2558,190
84252.202.96.0/19252.202.96.1 to 252.202.127.254252.202.127.2558,190
85252.202.128.0/19252.202.128.1 to 252.202.159.254252.202.159.2558,190
86252.202.160.0/19252.202.160.1 to 252.202.191.254252.202.191.2558,190
87252.202.192.0/19252.202.192.1 to 252.202.223.254252.202.223.2558,190
88252.202.224.0/19252.202.224.1 to 252.202.255.254252.202.255.2558,190
89252.203.0.0/19252.203.0.1 to 252.203.31.254252.203.31.2558,190
90252.203.32.0/19252.203.32.1 to 252.203.63.254252.203.63.2558,190
91252.203.64.0/19252.203.64.1 to 252.203.95.254252.203.95.2558,190
92252.203.96.0/19252.203.96.1 to 252.203.127.254252.203.127.2558,190
93252.203.128.0/19252.203.128.1 to 252.203.159.254252.203.159.2558,190
94252.203.160.0/19252.203.160.1 to 252.203.191.254252.203.191.2558,190
95252.203.192.0/19252.203.192.1 to 252.203.223.254252.203.223.2558,190
96252.203.224.0/19252.203.224.1 to 252.203.255.254252.203.255.2558,190
97252.204.0.0/19252.204.0.1 to 252.204.31.254252.204.31.2558,190
98252.204.32.0/19252.204.32.1 to 252.204.63.254252.204.63.2558,190
99252.204.64.0/19252.204.64.1 to 252.204.95.254252.204.95.2558,190
100252.204.96.0/19252.204.96.1 to 252.204.127.254252.204.127.2558,190
101252.204.128.0/19252.204.128.1 to 252.204.159.254252.204.159.2558,190
102252.204.160.0/19252.204.160.1 to 252.204.191.254252.204.191.2558,190
103252.204.192.0/19252.204.192.1 to 252.204.223.254252.204.223.2558,190
104252.204.224.0/19252.204.224.1 to 252.204.255.254252.204.255.2558,190
105252.205.0.0/19252.205.0.1 to 252.205.31.254252.205.31.2558,190
106252.205.32.0/19252.205.32.1 to 252.205.63.254252.205.63.2558,190
107252.205.64.0/19252.205.64.1 to 252.205.95.254252.205.95.2558,190
108252.205.96.0/19252.205.96.1 to 252.205.127.254252.205.127.2558,190
109252.205.128.0/19252.205.128.1 to 252.205.159.254252.205.159.2558,190
110252.205.160.0/19252.205.160.1 to 252.205.191.254252.205.191.2558,190
111252.205.192.0/19252.205.192.1 to 252.205.223.254252.205.223.2558,190
112252.205.224.0/19252.205.224.1 to 252.205.255.254252.205.255.2558,190
113252.206.0.0/19252.206.0.1 to 252.206.31.254252.206.31.2558,190
114252.206.32.0/19252.206.32.1 to 252.206.63.254252.206.63.2558,190
115252.206.64.0/19252.206.64.1 to 252.206.95.254252.206.95.2558,190
116252.206.96.0/19252.206.96.1 to 252.206.127.254252.206.127.2558,190
117252.206.128.0/19252.206.128.1 to 252.206.159.254252.206.159.2558,190
118252.206.160.0/19252.206.160.1 to 252.206.191.254252.206.191.2558,190
119252.206.192.0/19252.206.192.1 to 252.206.223.254252.206.223.2558,190
120252.206.224.0/19252.206.224.1 to 252.206.255.254252.206.255.2558,190
121252.207.0.0/19252.207.0.1 to 252.207.31.254252.207.31.2558,190
122252.207.32.0/19252.207.32.1 to 252.207.63.254252.207.63.2558,190
123252.207.64.0/19252.207.64.1 to 252.207.95.254252.207.95.2558,190
124252.207.96.0/19252.207.96.1 to 252.207.127.254252.207.127.2558,190
125252.207.128.0/19252.207.128.1 to 252.207.159.254252.207.159.2558,190
126252.207.160.0/19252.207.160.1 to 252.207.191.254252.207.191.2558,190
127252.207.192.0/19252.207.192.1 to 252.207.223.254252.207.223.2558,190
128252.207.224.0/19252.207.224.1 to 252.207.255.254252.207.255.2558,190
129252.208.0.0/19252.208.0.1 to 252.208.31.254252.208.31.2558,190
130252.208.32.0/19252.208.32.1 to 252.208.63.254252.208.63.2558,190
131252.208.64.0/19252.208.64.1 to 252.208.95.254252.208.95.2558,190
132252.208.96.0/19252.208.96.1 to 252.208.127.254252.208.127.2558,190
133252.208.128.0/19252.208.128.1 to 252.208.159.254252.208.159.2558,190
134252.208.160.0/19252.208.160.1 to 252.208.191.254252.208.191.2558,190
135252.208.192.0/19252.208.192.1 to 252.208.223.254252.208.223.2558,190
136252.208.224.0/19252.208.224.1 to 252.208.255.254252.208.255.2558,190
137252.209.0.0/19252.209.0.1 to 252.209.31.254252.209.31.2558,190
138252.209.32.0/19252.209.32.1 to 252.209.63.254252.209.63.2558,190
139252.209.64.0/19252.209.64.1 to 252.209.95.254252.209.95.2558,190
140252.209.96.0/19252.209.96.1 to 252.209.127.254252.209.127.2558,190
141252.209.128.0/19252.209.128.1 to 252.209.159.254252.209.159.2558,190
142252.209.160.0/19252.209.160.1 to 252.209.191.254252.209.191.2558,190
143252.209.192.0/19252.209.192.1 to 252.209.223.254252.209.223.2558,190
144252.209.224.0/19252.209.224.1 to 252.209.255.254252.209.255.2558,190
145252.210.0.0/19252.210.0.1 to 252.210.31.254252.210.31.2558,190
146252.210.32.0/19252.210.32.1 to 252.210.63.254252.210.63.2558,190
147252.210.64.0/19252.210.64.1 to 252.210.95.254252.210.95.2558,190
148252.210.96.0/19252.210.96.1 to 252.210.127.254252.210.127.2558,190
149252.210.128.0/19252.210.128.1 to 252.210.159.254252.210.159.2558,190
150252.210.160.0/19252.210.160.1 to 252.210.191.254252.210.191.2558,190
151252.210.192.0/19252.210.192.1 to 252.210.223.254252.210.223.2558,190
152252.210.224.0/19252.210.224.1 to 252.210.255.254252.210.255.2558,190
153252.211.0.0/19252.211.0.1 to 252.211.31.254252.211.31.2558,190
154252.211.32.0/19252.211.32.1 to 252.211.63.254252.211.63.2558,190
155252.211.64.0/19252.211.64.1 to 252.211.95.254252.211.95.2558,190
156252.211.96.0/19252.211.96.1 to 252.211.127.254252.211.127.2558,190
157252.211.128.0/19252.211.128.1 to 252.211.159.254252.211.159.2558,190
158252.211.160.0/19252.211.160.1 to 252.211.191.254252.211.191.2558,190
159252.211.192.0/19252.211.192.1 to 252.211.223.254252.211.223.2558,190
160252.211.224.0/19252.211.224.1 to 252.211.255.254252.211.255.2558,190
161252.212.0.0/19252.212.0.1 to 252.212.31.254252.212.31.2558,190
162252.212.32.0/19252.212.32.1 to 252.212.63.254252.212.63.2558,190
163252.212.64.0/19252.212.64.1 to 252.212.95.254252.212.95.2558,190
164252.212.96.0/19252.212.96.1 to 252.212.127.254252.212.127.2558,190
165252.212.128.0/19252.212.128.1 to 252.212.159.254252.212.159.2558,190
166252.212.160.0/19252.212.160.1 to 252.212.191.254252.212.191.2558,190
167252.212.192.0/19252.212.192.1 to 252.212.223.254252.212.223.2558,190
168252.212.224.0/19252.212.224.1 to 252.212.255.254252.212.255.2558,190
169252.213.0.0/19252.213.0.1 to 252.213.31.254252.213.31.2558,190
170252.213.32.0/19252.213.32.1 to 252.213.63.254252.213.63.2558,190
171252.213.64.0/19252.213.64.1 to 252.213.95.254252.213.95.2558,190
172252.213.96.0/19252.213.96.1 to 252.213.127.254252.213.127.2558,190
173252.213.128.0/19252.213.128.1 to 252.213.159.254252.213.159.2558,190
174252.213.160.0/19252.213.160.1 to 252.213.191.254252.213.191.2558,190
175252.213.192.0/19252.213.192.1 to 252.213.223.254252.213.223.2558,190
176252.213.224.0/19252.213.224.1 to 252.213.255.254252.213.255.2558,190
177252.214.0.0/19252.214.0.1 to 252.214.31.254252.214.31.2558,190
178252.214.32.0/19252.214.32.1 to 252.214.63.254252.214.63.2558,190
179252.214.64.0/19252.214.64.1 to 252.214.95.254252.214.95.2558,190
180252.214.96.0/19252.214.96.1 to 252.214.127.254252.214.127.2558,190
181252.214.128.0/19252.214.128.1 to 252.214.159.254252.214.159.2558,190
182252.214.160.0/19252.214.160.1 to 252.214.191.254252.214.191.2558,190
183252.214.192.0/19252.214.192.1 to 252.214.223.254252.214.223.2558,190
184252.214.224.0/19252.214.224.1 to 252.214.255.254252.214.255.2558,190
185252.215.0.0/19252.215.0.1 to 252.215.31.254252.215.31.2558,190
186252.215.32.0/19252.215.32.1 to 252.215.63.254252.215.63.2558,190
187252.215.64.0/19252.215.64.1 to 252.215.95.254252.215.95.2558,190
188252.215.96.0/19252.215.96.1 to 252.215.127.254252.215.127.2558,190
189252.215.128.0/19252.215.128.1 to 252.215.159.254252.215.159.2558,190
190252.215.160.0/19252.215.160.1 to 252.215.191.254252.215.191.2558,190
191252.215.192.0/19252.215.192.1 to 252.215.223.254252.215.223.2558,190
192252.215.224.0/19252.215.224.1 to 252.215.255.254252.215.255.2558,190
193252.216.0.0/19252.216.0.1 to 252.216.31.254252.216.31.2558,190
194252.216.32.0/19252.216.32.1 to 252.216.63.254252.216.63.2558,190
195252.216.64.0/19252.216.64.1 to 252.216.95.254252.216.95.2558,190
196252.216.96.0/19252.216.96.1 to 252.216.127.254252.216.127.2558,190
197252.216.128.0/19252.216.128.1 to 252.216.159.254252.216.159.2558,190
198252.216.160.0/19252.216.160.1 to 252.216.191.254252.216.191.2558,190
199252.216.192.0/19252.216.192.1 to 252.216.223.254252.216.223.2558,190
200252.216.224.0/19252.216.224.1 to 252.216.255.254252.216.255.2558,190
201252.217.0.0/19252.217.0.1 to 252.217.31.254252.217.31.2558,190
202252.217.32.0/19252.217.32.1 to 252.217.63.254252.217.63.2558,190
203252.217.64.0/19252.217.64.1 to 252.217.95.254252.217.95.2558,190
204252.217.96.0/19252.217.96.1 to 252.217.127.254252.217.127.2558,190
205252.217.128.0/19252.217.128.1 to 252.217.159.254252.217.159.2558,190
206252.217.160.0/19252.217.160.1 to 252.217.191.254252.217.191.2558,190
207252.217.192.0/19252.217.192.1 to 252.217.223.254252.217.223.2558,190
208252.217.224.0/19252.217.224.1 to 252.217.255.254252.217.255.2558,190
209252.218.0.0/19252.218.0.1 to 252.218.31.254252.218.31.2558,190
210252.218.32.0/19252.218.32.1 to 252.218.63.254252.218.63.2558,190
211252.218.64.0/19252.218.64.1 to 252.218.95.254252.218.95.2558,190
212252.218.96.0/19252.218.96.1 to 252.218.127.254252.218.127.2558,190
213252.218.128.0/19252.218.128.1 to 252.218.159.254252.218.159.2558,190
214252.218.160.0/19252.218.160.1 to 252.218.191.254252.218.191.2558,190
215252.218.192.0/19252.218.192.1 to 252.218.223.254252.218.223.2558,190
216252.218.224.0/19252.218.224.1 to 252.218.255.254252.218.255.2558,190
217252.219.0.0/19252.219.0.1 to 252.219.31.254252.219.31.2558,190
218252.219.32.0/19252.219.32.1 to 252.219.63.254252.219.63.2558,190
219252.219.64.0/19252.219.64.1 to 252.219.95.254252.219.95.2558,190
220252.219.96.0/19252.219.96.1 to 252.219.127.254252.219.127.2558,190
221252.219.128.0/19252.219.128.1 to 252.219.159.254252.219.159.2558,190
222252.219.160.0/19252.219.160.1 to 252.219.191.254252.219.191.2558,190
223252.219.192.0/19252.219.192.1 to 252.219.223.254252.219.223.2558,190
224252.219.224.0/19252.219.224.1 to 252.219.255.254252.219.255.2558,190
225252.220.0.0/19252.220.0.1 to 252.220.31.254252.220.31.2558,190
226252.220.32.0/19252.220.32.1 to 252.220.63.254252.220.63.2558,190
227252.220.64.0/19252.220.64.1 to 252.220.95.254252.220.95.2558,190
228252.220.96.0/19252.220.96.1 to 252.220.127.254252.220.127.2558,190
229252.220.128.0/19252.220.128.1 to 252.220.159.254252.220.159.2558,190
230252.220.160.0/19252.220.160.1 to 252.220.191.254252.220.191.2558,190
231252.220.192.0/19252.220.192.1 to 252.220.223.254252.220.223.2558,190
232252.220.224.0/19252.220.224.1 to 252.220.255.254252.220.255.2558,190
233252.221.0.0/19252.221.0.1 to 252.221.31.254252.221.31.2558,190
234252.221.32.0/19252.221.32.1 to 252.221.63.254252.221.63.2558,190
235252.221.64.0/19252.221.64.1 to 252.221.95.254252.221.95.2558,190
236252.221.96.0/19252.221.96.1 to 252.221.127.254252.221.127.2558,190
237252.221.128.0/19252.221.128.1 to 252.221.159.254252.221.159.2558,190
238252.221.160.0/19252.221.160.1 to 252.221.191.254252.221.191.2558,190
239252.221.192.0/19252.221.192.1 to 252.221.223.254252.221.223.2558,190
240252.221.224.0/19252.221.224.1 to 252.221.255.254252.221.255.2558,190
241252.222.0.0/19252.222.0.1 to 252.222.31.254252.222.31.2558,190
242252.222.32.0/19252.222.32.1 to 252.222.63.254252.222.63.2558,190
243252.222.64.0/19252.222.64.1 to 252.222.95.254252.222.95.2558,190
244252.222.96.0/19252.222.96.1 to 252.222.127.254252.222.127.2558,190
245252.222.128.0/19252.222.128.1 to 252.222.159.254252.222.159.2558,190
246252.222.160.0/19252.222.160.1 to 252.222.191.254252.222.191.2558,190
247252.222.192.0/19252.222.192.1 to 252.222.223.254252.222.223.2558,190
248252.222.224.0/19252.222.224.1 to 252.222.255.254252.222.255.2558,190
249252.223.0.0/19252.223.0.1 to 252.223.31.254252.223.31.2558,190
250252.223.32.0/19252.223.32.1 to 252.223.63.254252.223.63.2558,190
251252.223.64.0/19252.223.64.1 to 252.223.95.254252.223.95.2558,190
252252.223.96.0/19252.223.96.1 to 252.223.127.254252.223.127.2558,190
253252.223.128.0/19252.223.128.1 to 252.223.159.254252.223.159.2558,190
254252.223.160.0/19252.223.160.1 to 252.223.191.254252.223.191.2558,190
255252.223.192.0/19252.223.192.1 to 252.223.223.254252.223.223.2558,190
256252.223.224.0/19252.223.224.1 to 252.223.255.254252.223.255.2558,190

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.