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.

Network200.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
200.0.0.0
Broadcast address
201.255.255.255
First usable
200.0.0.1
Last usable
201.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
C (default /24)
As numbers
Hex C8000000 · Integer 3355443200 to 3388997631
Reverse DNS zones
200.in-addr.arpa
201.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11001000.00000000.00000000.00000000200.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network11001000.00000000.00000000.00000000200.0.0.0
Broadcast11001001.11111111.11111111.11111111201.255.255.255
Split into smaller subnets/18
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

200.0.0.0/7 makes 2,048 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1200.0.0.0/18200.0.0.1 to 200.0.63.254200.0.63.25516,382
2200.0.64.0/18200.0.64.1 to 200.0.127.254200.0.127.25516,382
3200.0.128.0/18200.0.128.1 to 200.0.191.254200.0.191.25516,382
4200.0.192.0/18200.0.192.1 to 200.0.255.254200.0.255.25516,382
5200.1.0.0/18200.1.0.1 to 200.1.63.254200.1.63.25516,382
6200.1.64.0/18200.1.64.1 to 200.1.127.254200.1.127.25516,382
7200.1.128.0/18200.1.128.1 to 200.1.191.254200.1.191.25516,382
8200.1.192.0/18200.1.192.1 to 200.1.255.254200.1.255.25516,382
9200.2.0.0/18200.2.0.1 to 200.2.63.254200.2.63.25516,382
10200.2.64.0/18200.2.64.1 to 200.2.127.254200.2.127.25516,382
11200.2.128.0/18200.2.128.1 to 200.2.191.254200.2.191.25516,382
12200.2.192.0/18200.2.192.1 to 200.2.255.254200.2.255.25516,382
13200.3.0.0/18200.3.0.1 to 200.3.63.254200.3.63.25516,382
14200.3.64.0/18200.3.64.1 to 200.3.127.254200.3.127.25516,382
15200.3.128.0/18200.3.128.1 to 200.3.191.254200.3.191.25516,382
16200.3.192.0/18200.3.192.1 to 200.3.255.254200.3.255.25516,382
17200.4.0.0/18200.4.0.1 to 200.4.63.254200.4.63.25516,382
18200.4.64.0/18200.4.64.1 to 200.4.127.254200.4.127.25516,382
19200.4.128.0/18200.4.128.1 to 200.4.191.254200.4.191.25516,382
20200.4.192.0/18200.4.192.1 to 200.4.255.254200.4.255.25516,382
21200.5.0.0/18200.5.0.1 to 200.5.63.254200.5.63.25516,382
22200.5.64.0/18200.5.64.1 to 200.5.127.254200.5.127.25516,382
23200.5.128.0/18200.5.128.1 to 200.5.191.254200.5.191.25516,382
24200.5.192.0/18200.5.192.1 to 200.5.255.254200.5.255.25516,382
25200.6.0.0/18200.6.0.1 to 200.6.63.254200.6.63.25516,382
26200.6.64.0/18200.6.64.1 to 200.6.127.254200.6.127.25516,382
27200.6.128.0/18200.6.128.1 to 200.6.191.254200.6.191.25516,382
28200.6.192.0/18200.6.192.1 to 200.6.255.254200.6.255.25516,382
29200.7.0.0/18200.7.0.1 to 200.7.63.254200.7.63.25516,382
30200.7.64.0/18200.7.64.1 to 200.7.127.254200.7.127.25516,382
31200.7.128.0/18200.7.128.1 to 200.7.191.254200.7.191.25516,382
32200.7.192.0/18200.7.192.1 to 200.7.255.254200.7.255.25516,382
33200.8.0.0/18200.8.0.1 to 200.8.63.254200.8.63.25516,382
34200.8.64.0/18200.8.64.1 to 200.8.127.254200.8.127.25516,382
35200.8.128.0/18200.8.128.1 to 200.8.191.254200.8.191.25516,382
36200.8.192.0/18200.8.192.1 to 200.8.255.254200.8.255.25516,382
37200.9.0.0/18200.9.0.1 to 200.9.63.254200.9.63.25516,382
38200.9.64.0/18200.9.64.1 to 200.9.127.254200.9.127.25516,382
39200.9.128.0/18200.9.128.1 to 200.9.191.254200.9.191.25516,382
40200.9.192.0/18200.9.192.1 to 200.9.255.254200.9.255.25516,382
41200.10.0.0/18200.10.0.1 to 200.10.63.254200.10.63.25516,382
42200.10.64.0/18200.10.64.1 to 200.10.127.254200.10.127.25516,382
43200.10.128.0/18200.10.128.1 to 200.10.191.254200.10.191.25516,382
44200.10.192.0/18200.10.192.1 to 200.10.255.254200.10.255.25516,382
45200.11.0.0/18200.11.0.1 to 200.11.63.254200.11.63.25516,382
46200.11.64.0/18200.11.64.1 to 200.11.127.254200.11.127.25516,382
47200.11.128.0/18200.11.128.1 to 200.11.191.254200.11.191.25516,382
48200.11.192.0/18200.11.192.1 to 200.11.255.254200.11.255.25516,382
49200.12.0.0/18200.12.0.1 to 200.12.63.254200.12.63.25516,382
50200.12.64.0/18200.12.64.1 to 200.12.127.254200.12.127.25516,382
51200.12.128.0/18200.12.128.1 to 200.12.191.254200.12.191.25516,382
52200.12.192.0/18200.12.192.1 to 200.12.255.254200.12.255.25516,382
53200.13.0.0/18200.13.0.1 to 200.13.63.254200.13.63.25516,382
54200.13.64.0/18200.13.64.1 to 200.13.127.254200.13.127.25516,382
55200.13.128.0/18200.13.128.1 to 200.13.191.254200.13.191.25516,382
56200.13.192.0/18200.13.192.1 to 200.13.255.254200.13.255.25516,382
57200.14.0.0/18200.14.0.1 to 200.14.63.254200.14.63.25516,382
58200.14.64.0/18200.14.64.1 to 200.14.127.254200.14.127.25516,382
59200.14.128.0/18200.14.128.1 to 200.14.191.254200.14.191.25516,382
60200.14.192.0/18200.14.192.1 to 200.14.255.254200.14.255.25516,382
61200.15.0.0/18200.15.0.1 to 200.15.63.254200.15.63.25516,382
62200.15.64.0/18200.15.64.1 to 200.15.127.254200.15.127.25516,382
63200.15.128.0/18200.15.128.1 to 200.15.191.254200.15.191.25516,382
64200.15.192.0/18200.15.192.1 to 200.15.255.254200.15.255.25516,382
65200.16.0.0/18200.16.0.1 to 200.16.63.254200.16.63.25516,382
66200.16.64.0/18200.16.64.1 to 200.16.127.254200.16.127.25516,382
67200.16.128.0/18200.16.128.1 to 200.16.191.254200.16.191.25516,382
68200.16.192.0/18200.16.192.1 to 200.16.255.254200.16.255.25516,382
69200.17.0.0/18200.17.0.1 to 200.17.63.254200.17.63.25516,382
70200.17.64.0/18200.17.64.1 to 200.17.127.254200.17.127.25516,382
71200.17.128.0/18200.17.128.1 to 200.17.191.254200.17.191.25516,382
72200.17.192.0/18200.17.192.1 to 200.17.255.254200.17.255.25516,382
73200.18.0.0/18200.18.0.1 to 200.18.63.254200.18.63.25516,382
74200.18.64.0/18200.18.64.1 to 200.18.127.254200.18.127.25516,382
75200.18.128.0/18200.18.128.1 to 200.18.191.254200.18.191.25516,382
76200.18.192.0/18200.18.192.1 to 200.18.255.254200.18.255.25516,382
77200.19.0.0/18200.19.0.1 to 200.19.63.254200.19.63.25516,382
78200.19.64.0/18200.19.64.1 to 200.19.127.254200.19.127.25516,382
79200.19.128.0/18200.19.128.1 to 200.19.191.254200.19.191.25516,382
80200.19.192.0/18200.19.192.1 to 200.19.255.254200.19.255.25516,382
81200.20.0.0/18200.20.0.1 to 200.20.63.254200.20.63.25516,382
82200.20.64.0/18200.20.64.1 to 200.20.127.254200.20.127.25516,382
83200.20.128.0/18200.20.128.1 to 200.20.191.254200.20.191.25516,382
84200.20.192.0/18200.20.192.1 to 200.20.255.254200.20.255.25516,382
85200.21.0.0/18200.21.0.1 to 200.21.63.254200.21.63.25516,382
86200.21.64.0/18200.21.64.1 to 200.21.127.254200.21.127.25516,382
87200.21.128.0/18200.21.128.1 to 200.21.191.254200.21.191.25516,382
88200.21.192.0/18200.21.192.1 to 200.21.255.254200.21.255.25516,382
89200.22.0.0/18200.22.0.1 to 200.22.63.254200.22.63.25516,382
90200.22.64.0/18200.22.64.1 to 200.22.127.254200.22.127.25516,382
91200.22.128.0/18200.22.128.1 to 200.22.191.254200.22.191.25516,382
92200.22.192.0/18200.22.192.1 to 200.22.255.254200.22.255.25516,382
93200.23.0.0/18200.23.0.1 to 200.23.63.254200.23.63.25516,382
94200.23.64.0/18200.23.64.1 to 200.23.127.254200.23.127.25516,382
95200.23.128.0/18200.23.128.1 to 200.23.191.254200.23.191.25516,382
96200.23.192.0/18200.23.192.1 to 200.23.255.254200.23.255.25516,382
97200.24.0.0/18200.24.0.1 to 200.24.63.254200.24.63.25516,382
98200.24.64.0/18200.24.64.1 to 200.24.127.254200.24.127.25516,382
99200.24.128.0/18200.24.128.1 to 200.24.191.254200.24.191.25516,382
100200.24.192.0/18200.24.192.1 to 200.24.255.254200.24.255.25516,382
101200.25.0.0/18200.25.0.1 to 200.25.63.254200.25.63.25516,382
102200.25.64.0/18200.25.64.1 to 200.25.127.254200.25.127.25516,382
103200.25.128.0/18200.25.128.1 to 200.25.191.254200.25.191.25516,382
104200.25.192.0/18200.25.192.1 to 200.25.255.254200.25.255.25516,382
105200.26.0.0/18200.26.0.1 to 200.26.63.254200.26.63.25516,382
106200.26.64.0/18200.26.64.1 to 200.26.127.254200.26.127.25516,382
107200.26.128.0/18200.26.128.1 to 200.26.191.254200.26.191.25516,382
108200.26.192.0/18200.26.192.1 to 200.26.255.254200.26.255.25516,382
109200.27.0.0/18200.27.0.1 to 200.27.63.254200.27.63.25516,382
110200.27.64.0/18200.27.64.1 to 200.27.127.254200.27.127.25516,382
111200.27.128.0/18200.27.128.1 to 200.27.191.254200.27.191.25516,382
112200.27.192.0/18200.27.192.1 to 200.27.255.254200.27.255.25516,382
113200.28.0.0/18200.28.0.1 to 200.28.63.254200.28.63.25516,382
114200.28.64.0/18200.28.64.1 to 200.28.127.254200.28.127.25516,382
115200.28.128.0/18200.28.128.1 to 200.28.191.254200.28.191.25516,382
116200.28.192.0/18200.28.192.1 to 200.28.255.254200.28.255.25516,382
117200.29.0.0/18200.29.0.1 to 200.29.63.254200.29.63.25516,382
118200.29.64.0/18200.29.64.1 to 200.29.127.254200.29.127.25516,382
119200.29.128.0/18200.29.128.1 to 200.29.191.254200.29.191.25516,382
120200.29.192.0/18200.29.192.1 to 200.29.255.254200.29.255.25516,382
121200.30.0.0/18200.30.0.1 to 200.30.63.254200.30.63.25516,382
122200.30.64.0/18200.30.64.1 to 200.30.127.254200.30.127.25516,382
123200.30.128.0/18200.30.128.1 to 200.30.191.254200.30.191.25516,382
124200.30.192.0/18200.30.192.1 to 200.30.255.254200.30.255.25516,382
125200.31.0.0/18200.31.0.1 to 200.31.63.254200.31.63.25516,382
126200.31.64.0/18200.31.64.1 to 200.31.127.254200.31.127.25516,382
127200.31.128.0/18200.31.128.1 to 200.31.191.254200.31.191.25516,382
128200.31.192.0/18200.31.192.1 to 200.31.255.254200.31.255.25516,382
129200.32.0.0/18200.32.0.1 to 200.32.63.254200.32.63.25516,382
130200.32.64.0/18200.32.64.1 to 200.32.127.254200.32.127.25516,382
131200.32.128.0/18200.32.128.1 to 200.32.191.254200.32.191.25516,382
132200.32.192.0/18200.32.192.1 to 200.32.255.254200.32.255.25516,382
133200.33.0.0/18200.33.0.1 to 200.33.63.254200.33.63.25516,382
134200.33.64.0/18200.33.64.1 to 200.33.127.254200.33.127.25516,382
135200.33.128.0/18200.33.128.1 to 200.33.191.254200.33.191.25516,382
136200.33.192.0/18200.33.192.1 to 200.33.255.254200.33.255.25516,382
137200.34.0.0/18200.34.0.1 to 200.34.63.254200.34.63.25516,382
138200.34.64.0/18200.34.64.1 to 200.34.127.254200.34.127.25516,382
139200.34.128.0/18200.34.128.1 to 200.34.191.254200.34.191.25516,382
140200.34.192.0/18200.34.192.1 to 200.34.255.254200.34.255.25516,382
141200.35.0.0/18200.35.0.1 to 200.35.63.254200.35.63.25516,382
142200.35.64.0/18200.35.64.1 to 200.35.127.254200.35.127.25516,382
143200.35.128.0/18200.35.128.1 to 200.35.191.254200.35.191.25516,382
144200.35.192.0/18200.35.192.1 to 200.35.255.254200.35.255.25516,382
145200.36.0.0/18200.36.0.1 to 200.36.63.254200.36.63.25516,382
146200.36.64.0/18200.36.64.1 to 200.36.127.254200.36.127.25516,382
147200.36.128.0/18200.36.128.1 to 200.36.191.254200.36.191.25516,382
148200.36.192.0/18200.36.192.1 to 200.36.255.254200.36.255.25516,382
149200.37.0.0/18200.37.0.1 to 200.37.63.254200.37.63.25516,382
150200.37.64.0/18200.37.64.1 to 200.37.127.254200.37.127.25516,382
151200.37.128.0/18200.37.128.1 to 200.37.191.254200.37.191.25516,382
152200.37.192.0/18200.37.192.1 to 200.37.255.254200.37.255.25516,382
153200.38.0.0/18200.38.0.1 to 200.38.63.254200.38.63.25516,382
154200.38.64.0/18200.38.64.1 to 200.38.127.254200.38.127.25516,382
155200.38.128.0/18200.38.128.1 to 200.38.191.254200.38.191.25516,382
156200.38.192.0/18200.38.192.1 to 200.38.255.254200.38.255.25516,382
157200.39.0.0/18200.39.0.1 to 200.39.63.254200.39.63.25516,382
158200.39.64.0/18200.39.64.1 to 200.39.127.254200.39.127.25516,382
159200.39.128.0/18200.39.128.1 to 200.39.191.254200.39.191.25516,382
160200.39.192.0/18200.39.192.1 to 200.39.255.254200.39.255.25516,382
161200.40.0.0/18200.40.0.1 to 200.40.63.254200.40.63.25516,382
162200.40.64.0/18200.40.64.1 to 200.40.127.254200.40.127.25516,382
163200.40.128.0/18200.40.128.1 to 200.40.191.254200.40.191.25516,382
164200.40.192.0/18200.40.192.1 to 200.40.255.254200.40.255.25516,382
165200.41.0.0/18200.41.0.1 to 200.41.63.254200.41.63.25516,382
166200.41.64.0/18200.41.64.1 to 200.41.127.254200.41.127.25516,382
167200.41.128.0/18200.41.128.1 to 200.41.191.254200.41.191.25516,382
168200.41.192.0/18200.41.192.1 to 200.41.255.254200.41.255.25516,382
169200.42.0.0/18200.42.0.1 to 200.42.63.254200.42.63.25516,382
170200.42.64.0/18200.42.64.1 to 200.42.127.254200.42.127.25516,382
171200.42.128.0/18200.42.128.1 to 200.42.191.254200.42.191.25516,382
172200.42.192.0/18200.42.192.1 to 200.42.255.254200.42.255.25516,382
173200.43.0.0/18200.43.0.1 to 200.43.63.254200.43.63.25516,382
174200.43.64.0/18200.43.64.1 to 200.43.127.254200.43.127.25516,382
175200.43.128.0/18200.43.128.1 to 200.43.191.254200.43.191.25516,382
176200.43.192.0/18200.43.192.1 to 200.43.255.254200.43.255.25516,382
177200.44.0.0/18200.44.0.1 to 200.44.63.254200.44.63.25516,382
178200.44.64.0/18200.44.64.1 to 200.44.127.254200.44.127.25516,382
179200.44.128.0/18200.44.128.1 to 200.44.191.254200.44.191.25516,382
180200.44.192.0/18200.44.192.1 to 200.44.255.254200.44.255.25516,382
181200.45.0.0/18200.45.0.1 to 200.45.63.254200.45.63.25516,382
182200.45.64.0/18200.45.64.1 to 200.45.127.254200.45.127.25516,382
183200.45.128.0/18200.45.128.1 to 200.45.191.254200.45.191.25516,382
184200.45.192.0/18200.45.192.1 to 200.45.255.254200.45.255.25516,382
185200.46.0.0/18200.46.0.1 to 200.46.63.254200.46.63.25516,382
186200.46.64.0/18200.46.64.1 to 200.46.127.254200.46.127.25516,382
187200.46.128.0/18200.46.128.1 to 200.46.191.254200.46.191.25516,382
188200.46.192.0/18200.46.192.1 to 200.46.255.254200.46.255.25516,382
189200.47.0.0/18200.47.0.1 to 200.47.63.254200.47.63.25516,382
190200.47.64.0/18200.47.64.1 to 200.47.127.254200.47.127.25516,382
191200.47.128.0/18200.47.128.1 to 200.47.191.254200.47.191.25516,382
192200.47.192.0/18200.47.192.1 to 200.47.255.254200.47.255.25516,382
193200.48.0.0/18200.48.0.1 to 200.48.63.254200.48.63.25516,382
194200.48.64.0/18200.48.64.1 to 200.48.127.254200.48.127.25516,382
195200.48.128.0/18200.48.128.1 to 200.48.191.254200.48.191.25516,382
196200.48.192.0/18200.48.192.1 to 200.48.255.254200.48.255.25516,382
197200.49.0.0/18200.49.0.1 to 200.49.63.254200.49.63.25516,382
198200.49.64.0/18200.49.64.1 to 200.49.127.254200.49.127.25516,382
199200.49.128.0/18200.49.128.1 to 200.49.191.254200.49.191.25516,382
200200.49.192.0/18200.49.192.1 to 200.49.255.254200.49.255.25516,382
201200.50.0.0/18200.50.0.1 to 200.50.63.254200.50.63.25516,382
202200.50.64.0/18200.50.64.1 to 200.50.127.254200.50.127.25516,382
203200.50.128.0/18200.50.128.1 to 200.50.191.254200.50.191.25516,382
204200.50.192.0/18200.50.192.1 to 200.50.255.254200.50.255.25516,382
205200.51.0.0/18200.51.0.1 to 200.51.63.254200.51.63.25516,382
206200.51.64.0/18200.51.64.1 to 200.51.127.254200.51.127.25516,382
207200.51.128.0/18200.51.128.1 to 200.51.191.254200.51.191.25516,382
208200.51.192.0/18200.51.192.1 to 200.51.255.254200.51.255.25516,382
209200.52.0.0/18200.52.0.1 to 200.52.63.254200.52.63.25516,382
210200.52.64.0/18200.52.64.1 to 200.52.127.254200.52.127.25516,382
211200.52.128.0/18200.52.128.1 to 200.52.191.254200.52.191.25516,382
212200.52.192.0/18200.52.192.1 to 200.52.255.254200.52.255.25516,382
213200.53.0.0/18200.53.0.1 to 200.53.63.254200.53.63.25516,382
214200.53.64.0/18200.53.64.1 to 200.53.127.254200.53.127.25516,382
215200.53.128.0/18200.53.128.1 to 200.53.191.254200.53.191.25516,382
216200.53.192.0/18200.53.192.1 to 200.53.255.254200.53.255.25516,382
217200.54.0.0/18200.54.0.1 to 200.54.63.254200.54.63.25516,382
218200.54.64.0/18200.54.64.1 to 200.54.127.254200.54.127.25516,382
219200.54.128.0/18200.54.128.1 to 200.54.191.254200.54.191.25516,382
220200.54.192.0/18200.54.192.1 to 200.54.255.254200.54.255.25516,382
221200.55.0.0/18200.55.0.1 to 200.55.63.254200.55.63.25516,382
222200.55.64.0/18200.55.64.1 to 200.55.127.254200.55.127.25516,382
223200.55.128.0/18200.55.128.1 to 200.55.191.254200.55.191.25516,382
224200.55.192.0/18200.55.192.1 to 200.55.255.254200.55.255.25516,382
225200.56.0.0/18200.56.0.1 to 200.56.63.254200.56.63.25516,382
226200.56.64.0/18200.56.64.1 to 200.56.127.254200.56.127.25516,382
227200.56.128.0/18200.56.128.1 to 200.56.191.254200.56.191.25516,382
228200.56.192.0/18200.56.192.1 to 200.56.255.254200.56.255.25516,382
229200.57.0.0/18200.57.0.1 to 200.57.63.254200.57.63.25516,382
230200.57.64.0/18200.57.64.1 to 200.57.127.254200.57.127.25516,382
231200.57.128.0/18200.57.128.1 to 200.57.191.254200.57.191.25516,382
232200.57.192.0/18200.57.192.1 to 200.57.255.254200.57.255.25516,382
233200.58.0.0/18200.58.0.1 to 200.58.63.254200.58.63.25516,382
234200.58.64.0/18200.58.64.1 to 200.58.127.254200.58.127.25516,382
235200.58.128.0/18200.58.128.1 to 200.58.191.254200.58.191.25516,382
236200.58.192.0/18200.58.192.1 to 200.58.255.254200.58.255.25516,382
237200.59.0.0/18200.59.0.1 to 200.59.63.254200.59.63.25516,382
238200.59.64.0/18200.59.64.1 to 200.59.127.254200.59.127.25516,382
239200.59.128.0/18200.59.128.1 to 200.59.191.254200.59.191.25516,382
240200.59.192.0/18200.59.192.1 to 200.59.255.254200.59.255.25516,382
241200.60.0.0/18200.60.0.1 to 200.60.63.254200.60.63.25516,382
242200.60.64.0/18200.60.64.1 to 200.60.127.254200.60.127.25516,382
243200.60.128.0/18200.60.128.1 to 200.60.191.254200.60.191.25516,382
244200.60.192.0/18200.60.192.1 to 200.60.255.254200.60.255.25516,382
245200.61.0.0/18200.61.0.1 to 200.61.63.254200.61.63.25516,382
246200.61.64.0/18200.61.64.1 to 200.61.127.254200.61.127.25516,382
247200.61.128.0/18200.61.128.1 to 200.61.191.254200.61.191.25516,382
248200.61.192.0/18200.61.192.1 to 200.61.255.254200.61.255.25516,382
249200.62.0.0/18200.62.0.1 to 200.62.63.254200.62.63.25516,382
250200.62.64.0/18200.62.64.1 to 200.62.127.254200.62.127.25516,382
251200.62.128.0/18200.62.128.1 to 200.62.191.254200.62.191.25516,382
252200.62.192.0/18200.62.192.1 to 200.62.255.254200.62.255.25516,382
253200.63.0.0/18200.63.0.1 to 200.63.63.254200.63.63.25516,382
254200.63.64.0/18200.63.64.1 to 200.63.127.254200.63.127.25516,382
255200.63.128.0/18200.63.128.1 to 200.63.191.254200.63.191.25516,382
256200.63.192.0/18200.63.192.1 to 200.63.255.254200.63.255.25516,382

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.