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.

Network217.2.0.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
217.2.0.0
Broadcast address
217.2.63.255
First usable
217.2.0.1
Last usable
217.2.63.254
Usable hosts
16,382 (16,384 less the network and broadcast addresses)
Subnet mask
255.255.192.0
Wildcard mask
0.0.63.255 (Cisco ACLs, OSPF)
Prefix length
/18
Type
Public public
Old class
C (default /24)
As numbers
Hex D9020000 · Integer 3640786944 to 3640803327
Reverse DNS zones
0.2.217.in-addr.arpa
1.2.217.in-addr.arpa
2.2.217.in-addr.arpa
3.2.217.in-addr.arpa
4.2.217.in-addr.arpa
5.2.217.in-addr.arpa
6.2.217.in-addr.arpa
7.2.217.in-addr.arpa
8.2.217.in-addr.arpa
9.2.217.in-addr.arpa
10.2.217.in-addr.arpa
11.2.217.in-addr.arpa
12.2.217.in-addr.arpa
13.2.217.in-addr.arpa
14.2.217.in-addr.arpa
15.2.217.in-addr.arpa
and 48 more
/18 is not on a 8-bit boundary, so it takes 64 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11011001.00000010.00000000.00000000217.2.0.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network11011001.00000010.00000000.00000000217.2.0.0
Broadcast11011001.00000010.00111111.11111111217.2.63.255
Split into smaller subnets/26
/19 (2)/20 (4)/21 (8)/22 (16)/23 (32)/24 (64)/25 (128)/26 (256)/27 (512)/28 (1,024)/29 (2,048)/30 (4,096)

217.2.0.0/18 makes 256 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1217.2.0.0/26217.2.0.1 to 217.2.0.62217.2.0.6362
2217.2.0.64/26217.2.0.65 to 217.2.0.126217.2.0.12762
3217.2.0.128/26217.2.0.129 to 217.2.0.190217.2.0.19162
4217.2.0.192/26217.2.0.193 to 217.2.0.254217.2.0.25562
5217.2.1.0/26217.2.1.1 to 217.2.1.62217.2.1.6362
6217.2.1.64/26217.2.1.65 to 217.2.1.126217.2.1.12762
7217.2.1.128/26217.2.1.129 to 217.2.1.190217.2.1.19162
8217.2.1.192/26217.2.1.193 to 217.2.1.254217.2.1.25562
9217.2.2.0/26217.2.2.1 to 217.2.2.62217.2.2.6362
10217.2.2.64/26217.2.2.65 to 217.2.2.126217.2.2.12762
11217.2.2.128/26217.2.2.129 to 217.2.2.190217.2.2.19162
12217.2.2.192/26217.2.2.193 to 217.2.2.254217.2.2.25562
13217.2.3.0/26217.2.3.1 to 217.2.3.62217.2.3.6362
14217.2.3.64/26217.2.3.65 to 217.2.3.126217.2.3.12762
15217.2.3.128/26217.2.3.129 to 217.2.3.190217.2.3.19162
16217.2.3.192/26217.2.3.193 to 217.2.3.254217.2.3.25562
17217.2.4.0/26217.2.4.1 to 217.2.4.62217.2.4.6362
18217.2.4.64/26217.2.4.65 to 217.2.4.126217.2.4.12762
19217.2.4.128/26217.2.4.129 to 217.2.4.190217.2.4.19162
20217.2.4.192/26217.2.4.193 to 217.2.4.254217.2.4.25562
21217.2.5.0/26217.2.5.1 to 217.2.5.62217.2.5.6362
22217.2.5.64/26217.2.5.65 to 217.2.5.126217.2.5.12762
23217.2.5.128/26217.2.5.129 to 217.2.5.190217.2.5.19162
24217.2.5.192/26217.2.5.193 to 217.2.5.254217.2.5.25562
25217.2.6.0/26217.2.6.1 to 217.2.6.62217.2.6.6362
26217.2.6.64/26217.2.6.65 to 217.2.6.126217.2.6.12762
27217.2.6.128/26217.2.6.129 to 217.2.6.190217.2.6.19162
28217.2.6.192/26217.2.6.193 to 217.2.6.254217.2.6.25562
29217.2.7.0/26217.2.7.1 to 217.2.7.62217.2.7.6362
30217.2.7.64/26217.2.7.65 to 217.2.7.126217.2.7.12762
31217.2.7.128/26217.2.7.129 to 217.2.7.190217.2.7.19162
32217.2.7.192/26217.2.7.193 to 217.2.7.254217.2.7.25562
33217.2.8.0/26217.2.8.1 to 217.2.8.62217.2.8.6362
34217.2.8.64/26217.2.8.65 to 217.2.8.126217.2.8.12762
35217.2.8.128/26217.2.8.129 to 217.2.8.190217.2.8.19162
36217.2.8.192/26217.2.8.193 to 217.2.8.254217.2.8.25562
37217.2.9.0/26217.2.9.1 to 217.2.9.62217.2.9.6362
38217.2.9.64/26217.2.9.65 to 217.2.9.126217.2.9.12762
39217.2.9.128/26217.2.9.129 to 217.2.9.190217.2.9.19162
40217.2.9.192/26217.2.9.193 to 217.2.9.254217.2.9.25562
41217.2.10.0/26217.2.10.1 to 217.2.10.62217.2.10.6362
42217.2.10.64/26217.2.10.65 to 217.2.10.126217.2.10.12762
43217.2.10.128/26217.2.10.129 to 217.2.10.190217.2.10.19162
44217.2.10.192/26217.2.10.193 to 217.2.10.254217.2.10.25562
45217.2.11.0/26217.2.11.1 to 217.2.11.62217.2.11.6362
46217.2.11.64/26217.2.11.65 to 217.2.11.126217.2.11.12762
47217.2.11.128/26217.2.11.129 to 217.2.11.190217.2.11.19162
48217.2.11.192/26217.2.11.193 to 217.2.11.254217.2.11.25562
49217.2.12.0/26217.2.12.1 to 217.2.12.62217.2.12.6362
50217.2.12.64/26217.2.12.65 to 217.2.12.126217.2.12.12762
51217.2.12.128/26217.2.12.129 to 217.2.12.190217.2.12.19162
52217.2.12.192/26217.2.12.193 to 217.2.12.254217.2.12.25562
53217.2.13.0/26217.2.13.1 to 217.2.13.62217.2.13.6362
54217.2.13.64/26217.2.13.65 to 217.2.13.126217.2.13.12762
55217.2.13.128/26217.2.13.129 to 217.2.13.190217.2.13.19162
56217.2.13.192/26217.2.13.193 to 217.2.13.254217.2.13.25562
57217.2.14.0/26217.2.14.1 to 217.2.14.62217.2.14.6362
58217.2.14.64/26217.2.14.65 to 217.2.14.126217.2.14.12762
59217.2.14.128/26217.2.14.129 to 217.2.14.190217.2.14.19162
60217.2.14.192/26217.2.14.193 to 217.2.14.254217.2.14.25562
61217.2.15.0/26217.2.15.1 to 217.2.15.62217.2.15.6362
62217.2.15.64/26217.2.15.65 to 217.2.15.126217.2.15.12762
63217.2.15.128/26217.2.15.129 to 217.2.15.190217.2.15.19162
64217.2.15.192/26217.2.15.193 to 217.2.15.254217.2.15.25562
65217.2.16.0/26217.2.16.1 to 217.2.16.62217.2.16.6362
66217.2.16.64/26217.2.16.65 to 217.2.16.126217.2.16.12762
67217.2.16.128/26217.2.16.129 to 217.2.16.190217.2.16.19162
68217.2.16.192/26217.2.16.193 to 217.2.16.254217.2.16.25562
69217.2.17.0/26217.2.17.1 to 217.2.17.62217.2.17.6362
70217.2.17.64/26217.2.17.65 to 217.2.17.126217.2.17.12762
71217.2.17.128/26217.2.17.129 to 217.2.17.190217.2.17.19162
72217.2.17.192/26217.2.17.193 to 217.2.17.254217.2.17.25562
73217.2.18.0/26217.2.18.1 to 217.2.18.62217.2.18.6362
74217.2.18.64/26217.2.18.65 to 217.2.18.126217.2.18.12762
75217.2.18.128/26217.2.18.129 to 217.2.18.190217.2.18.19162
76217.2.18.192/26217.2.18.193 to 217.2.18.254217.2.18.25562
77217.2.19.0/26217.2.19.1 to 217.2.19.62217.2.19.6362
78217.2.19.64/26217.2.19.65 to 217.2.19.126217.2.19.12762
79217.2.19.128/26217.2.19.129 to 217.2.19.190217.2.19.19162
80217.2.19.192/26217.2.19.193 to 217.2.19.254217.2.19.25562
81217.2.20.0/26217.2.20.1 to 217.2.20.62217.2.20.6362
82217.2.20.64/26217.2.20.65 to 217.2.20.126217.2.20.12762
83217.2.20.128/26217.2.20.129 to 217.2.20.190217.2.20.19162
84217.2.20.192/26217.2.20.193 to 217.2.20.254217.2.20.25562
85217.2.21.0/26217.2.21.1 to 217.2.21.62217.2.21.6362
86217.2.21.64/26217.2.21.65 to 217.2.21.126217.2.21.12762
87217.2.21.128/26217.2.21.129 to 217.2.21.190217.2.21.19162
88217.2.21.192/26217.2.21.193 to 217.2.21.254217.2.21.25562
89217.2.22.0/26217.2.22.1 to 217.2.22.62217.2.22.6362
90217.2.22.64/26217.2.22.65 to 217.2.22.126217.2.22.12762
91217.2.22.128/26217.2.22.129 to 217.2.22.190217.2.22.19162
92217.2.22.192/26217.2.22.193 to 217.2.22.254217.2.22.25562
93217.2.23.0/26217.2.23.1 to 217.2.23.62217.2.23.6362
94217.2.23.64/26217.2.23.65 to 217.2.23.126217.2.23.12762
95217.2.23.128/26217.2.23.129 to 217.2.23.190217.2.23.19162
96217.2.23.192/26217.2.23.193 to 217.2.23.254217.2.23.25562
97217.2.24.0/26217.2.24.1 to 217.2.24.62217.2.24.6362
98217.2.24.64/26217.2.24.65 to 217.2.24.126217.2.24.12762
99217.2.24.128/26217.2.24.129 to 217.2.24.190217.2.24.19162
100217.2.24.192/26217.2.24.193 to 217.2.24.254217.2.24.25562
101217.2.25.0/26217.2.25.1 to 217.2.25.62217.2.25.6362
102217.2.25.64/26217.2.25.65 to 217.2.25.126217.2.25.12762
103217.2.25.128/26217.2.25.129 to 217.2.25.190217.2.25.19162
104217.2.25.192/26217.2.25.193 to 217.2.25.254217.2.25.25562
105217.2.26.0/26217.2.26.1 to 217.2.26.62217.2.26.6362
106217.2.26.64/26217.2.26.65 to 217.2.26.126217.2.26.12762
107217.2.26.128/26217.2.26.129 to 217.2.26.190217.2.26.19162
108217.2.26.192/26217.2.26.193 to 217.2.26.254217.2.26.25562
109217.2.27.0/26217.2.27.1 to 217.2.27.62217.2.27.6362
110217.2.27.64/26217.2.27.65 to 217.2.27.126217.2.27.12762
111217.2.27.128/26217.2.27.129 to 217.2.27.190217.2.27.19162
112217.2.27.192/26217.2.27.193 to 217.2.27.254217.2.27.25562
113217.2.28.0/26217.2.28.1 to 217.2.28.62217.2.28.6362
114217.2.28.64/26217.2.28.65 to 217.2.28.126217.2.28.12762
115217.2.28.128/26217.2.28.129 to 217.2.28.190217.2.28.19162
116217.2.28.192/26217.2.28.193 to 217.2.28.254217.2.28.25562
117217.2.29.0/26217.2.29.1 to 217.2.29.62217.2.29.6362
118217.2.29.64/26217.2.29.65 to 217.2.29.126217.2.29.12762
119217.2.29.128/26217.2.29.129 to 217.2.29.190217.2.29.19162
120217.2.29.192/26217.2.29.193 to 217.2.29.254217.2.29.25562
121217.2.30.0/26217.2.30.1 to 217.2.30.62217.2.30.6362
122217.2.30.64/26217.2.30.65 to 217.2.30.126217.2.30.12762
123217.2.30.128/26217.2.30.129 to 217.2.30.190217.2.30.19162
124217.2.30.192/26217.2.30.193 to 217.2.30.254217.2.30.25562
125217.2.31.0/26217.2.31.1 to 217.2.31.62217.2.31.6362
126217.2.31.64/26217.2.31.65 to 217.2.31.126217.2.31.12762
127217.2.31.128/26217.2.31.129 to 217.2.31.190217.2.31.19162
128217.2.31.192/26217.2.31.193 to 217.2.31.254217.2.31.25562
129217.2.32.0/26217.2.32.1 to 217.2.32.62217.2.32.6362
130217.2.32.64/26217.2.32.65 to 217.2.32.126217.2.32.12762
131217.2.32.128/26217.2.32.129 to 217.2.32.190217.2.32.19162
132217.2.32.192/26217.2.32.193 to 217.2.32.254217.2.32.25562
133217.2.33.0/26217.2.33.1 to 217.2.33.62217.2.33.6362
134217.2.33.64/26217.2.33.65 to 217.2.33.126217.2.33.12762
135217.2.33.128/26217.2.33.129 to 217.2.33.190217.2.33.19162
136217.2.33.192/26217.2.33.193 to 217.2.33.254217.2.33.25562
137217.2.34.0/26217.2.34.1 to 217.2.34.62217.2.34.6362
138217.2.34.64/26217.2.34.65 to 217.2.34.126217.2.34.12762
139217.2.34.128/26217.2.34.129 to 217.2.34.190217.2.34.19162
140217.2.34.192/26217.2.34.193 to 217.2.34.254217.2.34.25562
141217.2.35.0/26217.2.35.1 to 217.2.35.62217.2.35.6362
142217.2.35.64/26217.2.35.65 to 217.2.35.126217.2.35.12762
143217.2.35.128/26217.2.35.129 to 217.2.35.190217.2.35.19162
144217.2.35.192/26217.2.35.193 to 217.2.35.254217.2.35.25562
145217.2.36.0/26217.2.36.1 to 217.2.36.62217.2.36.6362
146217.2.36.64/26217.2.36.65 to 217.2.36.126217.2.36.12762
147217.2.36.128/26217.2.36.129 to 217.2.36.190217.2.36.19162
148217.2.36.192/26217.2.36.193 to 217.2.36.254217.2.36.25562
149217.2.37.0/26217.2.37.1 to 217.2.37.62217.2.37.6362
150217.2.37.64/26217.2.37.65 to 217.2.37.126217.2.37.12762
151217.2.37.128/26217.2.37.129 to 217.2.37.190217.2.37.19162
152217.2.37.192/26217.2.37.193 to 217.2.37.254217.2.37.25562
153217.2.38.0/26217.2.38.1 to 217.2.38.62217.2.38.6362
154217.2.38.64/26217.2.38.65 to 217.2.38.126217.2.38.12762
155217.2.38.128/26217.2.38.129 to 217.2.38.190217.2.38.19162
156217.2.38.192/26217.2.38.193 to 217.2.38.254217.2.38.25562
157217.2.39.0/26217.2.39.1 to 217.2.39.62217.2.39.6362
158217.2.39.64/26217.2.39.65 to 217.2.39.126217.2.39.12762
159217.2.39.128/26217.2.39.129 to 217.2.39.190217.2.39.19162
160217.2.39.192/26217.2.39.193 to 217.2.39.254217.2.39.25562
161217.2.40.0/26217.2.40.1 to 217.2.40.62217.2.40.6362
162217.2.40.64/26217.2.40.65 to 217.2.40.126217.2.40.12762
163217.2.40.128/26217.2.40.129 to 217.2.40.190217.2.40.19162
164217.2.40.192/26217.2.40.193 to 217.2.40.254217.2.40.25562
165217.2.41.0/26217.2.41.1 to 217.2.41.62217.2.41.6362
166217.2.41.64/26217.2.41.65 to 217.2.41.126217.2.41.12762
167217.2.41.128/26217.2.41.129 to 217.2.41.190217.2.41.19162
168217.2.41.192/26217.2.41.193 to 217.2.41.254217.2.41.25562
169217.2.42.0/26217.2.42.1 to 217.2.42.62217.2.42.6362
170217.2.42.64/26217.2.42.65 to 217.2.42.126217.2.42.12762
171217.2.42.128/26217.2.42.129 to 217.2.42.190217.2.42.19162
172217.2.42.192/26217.2.42.193 to 217.2.42.254217.2.42.25562
173217.2.43.0/26217.2.43.1 to 217.2.43.62217.2.43.6362
174217.2.43.64/26217.2.43.65 to 217.2.43.126217.2.43.12762
175217.2.43.128/26217.2.43.129 to 217.2.43.190217.2.43.19162
176217.2.43.192/26217.2.43.193 to 217.2.43.254217.2.43.25562
177217.2.44.0/26217.2.44.1 to 217.2.44.62217.2.44.6362
178217.2.44.64/26217.2.44.65 to 217.2.44.126217.2.44.12762
179217.2.44.128/26217.2.44.129 to 217.2.44.190217.2.44.19162
180217.2.44.192/26217.2.44.193 to 217.2.44.254217.2.44.25562
181217.2.45.0/26217.2.45.1 to 217.2.45.62217.2.45.6362
182217.2.45.64/26217.2.45.65 to 217.2.45.126217.2.45.12762
183217.2.45.128/26217.2.45.129 to 217.2.45.190217.2.45.19162
184217.2.45.192/26217.2.45.193 to 217.2.45.254217.2.45.25562
185217.2.46.0/26217.2.46.1 to 217.2.46.62217.2.46.6362
186217.2.46.64/26217.2.46.65 to 217.2.46.126217.2.46.12762
187217.2.46.128/26217.2.46.129 to 217.2.46.190217.2.46.19162
188217.2.46.192/26217.2.46.193 to 217.2.46.254217.2.46.25562
189217.2.47.0/26217.2.47.1 to 217.2.47.62217.2.47.6362
190217.2.47.64/26217.2.47.65 to 217.2.47.126217.2.47.12762
191217.2.47.128/26217.2.47.129 to 217.2.47.190217.2.47.19162
192217.2.47.192/26217.2.47.193 to 217.2.47.254217.2.47.25562
193217.2.48.0/26217.2.48.1 to 217.2.48.62217.2.48.6362
194217.2.48.64/26217.2.48.65 to 217.2.48.126217.2.48.12762
195217.2.48.128/26217.2.48.129 to 217.2.48.190217.2.48.19162
196217.2.48.192/26217.2.48.193 to 217.2.48.254217.2.48.25562
197217.2.49.0/26217.2.49.1 to 217.2.49.62217.2.49.6362
198217.2.49.64/26217.2.49.65 to 217.2.49.126217.2.49.12762
199217.2.49.128/26217.2.49.129 to 217.2.49.190217.2.49.19162
200217.2.49.192/26217.2.49.193 to 217.2.49.254217.2.49.25562
201217.2.50.0/26217.2.50.1 to 217.2.50.62217.2.50.6362
202217.2.50.64/26217.2.50.65 to 217.2.50.126217.2.50.12762
203217.2.50.128/26217.2.50.129 to 217.2.50.190217.2.50.19162
204217.2.50.192/26217.2.50.193 to 217.2.50.254217.2.50.25562
205217.2.51.0/26217.2.51.1 to 217.2.51.62217.2.51.6362
206217.2.51.64/26217.2.51.65 to 217.2.51.126217.2.51.12762
207217.2.51.128/26217.2.51.129 to 217.2.51.190217.2.51.19162
208217.2.51.192/26217.2.51.193 to 217.2.51.254217.2.51.25562
209217.2.52.0/26217.2.52.1 to 217.2.52.62217.2.52.6362
210217.2.52.64/26217.2.52.65 to 217.2.52.126217.2.52.12762
211217.2.52.128/26217.2.52.129 to 217.2.52.190217.2.52.19162
212217.2.52.192/26217.2.52.193 to 217.2.52.254217.2.52.25562
213217.2.53.0/26217.2.53.1 to 217.2.53.62217.2.53.6362
214217.2.53.64/26217.2.53.65 to 217.2.53.126217.2.53.12762
215217.2.53.128/26217.2.53.129 to 217.2.53.190217.2.53.19162
216217.2.53.192/26217.2.53.193 to 217.2.53.254217.2.53.25562
217217.2.54.0/26217.2.54.1 to 217.2.54.62217.2.54.6362
218217.2.54.64/26217.2.54.65 to 217.2.54.126217.2.54.12762
219217.2.54.128/26217.2.54.129 to 217.2.54.190217.2.54.19162
220217.2.54.192/26217.2.54.193 to 217.2.54.254217.2.54.25562
221217.2.55.0/26217.2.55.1 to 217.2.55.62217.2.55.6362
222217.2.55.64/26217.2.55.65 to 217.2.55.126217.2.55.12762
223217.2.55.128/26217.2.55.129 to 217.2.55.190217.2.55.19162
224217.2.55.192/26217.2.55.193 to 217.2.55.254217.2.55.25562
225217.2.56.0/26217.2.56.1 to 217.2.56.62217.2.56.6362
226217.2.56.64/26217.2.56.65 to 217.2.56.126217.2.56.12762
227217.2.56.128/26217.2.56.129 to 217.2.56.190217.2.56.19162
228217.2.56.192/26217.2.56.193 to 217.2.56.254217.2.56.25562
229217.2.57.0/26217.2.57.1 to 217.2.57.62217.2.57.6362
230217.2.57.64/26217.2.57.65 to 217.2.57.126217.2.57.12762
231217.2.57.128/26217.2.57.129 to 217.2.57.190217.2.57.19162
232217.2.57.192/26217.2.57.193 to 217.2.57.254217.2.57.25562
233217.2.58.0/26217.2.58.1 to 217.2.58.62217.2.58.6362
234217.2.58.64/26217.2.58.65 to 217.2.58.126217.2.58.12762
235217.2.58.128/26217.2.58.129 to 217.2.58.190217.2.58.19162
236217.2.58.192/26217.2.58.193 to 217.2.58.254217.2.58.25562
237217.2.59.0/26217.2.59.1 to 217.2.59.62217.2.59.6362
238217.2.59.64/26217.2.59.65 to 217.2.59.126217.2.59.12762
239217.2.59.128/26217.2.59.129 to 217.2.59.190217.2.59.19162
240217.2.59.192/26217.2.59.193 to 217.2.59.254217.2.59.25562
241217.2.60.0/26217.2.60.1 to 217.2.60.62217.2.60.6362
242217.2.60.64/26217.2.60.65 to 217.2.60.126217.2.60.12762
243217.2.60.128/26217.2.60.129 to 217.2.60.190217.2.60.19162
244217.2.60.192/26217.2.60.193 to 217.2.60.254217.2.60.25562
245217.2.61.0/26217.2.61.1 to 217.2.61.62217.2.61.6362
246217.2.61.64/26217.2.61.65 to 217.2.61.126217.2.61.12762
247217.2.61.128/26217.2.61.129 to 217.2.61.190217.2.61.19162
248217.2.61.192/26217.2.61.193 to 217.2.61.254217.2.61.25562
249217.2.62.0/26217.2.62.1 to 217.2.62.62217.2.62.6362
250217.2.62.64/26217.2.62.65 to 217.2.62.126217.2.62.12762
251217.2.62.128/26217.2.62.129 to 217.2.62.190217.2.62.19162
252217.2.62.192/26217.2.62.193 to 217.2.62.254217.2.62.25562
253217.2.63.0/26217.2.63.1 to 217.2.63.62217.2.63.6362
254217.2.63.64/26217.2.63.65 to 217.2.63.126217.2.63.12762
255217.2.63.128/26217.2.63.129 to 217.2.63.190217.2.63.19162
256217.2.63.192/26217.2.63.193 to 217.2.63.254217.2.63.25562

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.