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.

Prefix/16
Addresses2^112
/64 networks2^48
Network
ff7b::/16
First address
ff7b::
Last address
ff7b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
5,192,296,858,534,827,628,530,496,329,220,096 (2^112)
/64 networks (LANs)
281,474,976,710,656 (2^48)
Full form
ff7b:0000:0000:0000:0000:0000:0000:0000
Type
Multicast ff00::/8
One-to-many traffic; replaces broadcast
Reverse DNS zone
b.7.f.f.ip6.arpa
Split into smaller subnets/32
/17 (2)/18 (4)/19 (8)/20 (16)/24 (256)/28 (4,096)/32 (65,536)

ff7b::/16 makes 65,536 subnets of /32; the first 256 are listed.

Subnets
#SubnetLast address
1ff7b::/32ff7b:0:ffff:ffff:ffff:ffff:ffff:ffff
2ff7b:1::/32ff7b:1:ffff:ffff:ffff:ffff:ffff:ffff
3ff7b:2::/32ff7b:2:ffff:ffff:ffff:ffff:ffff:ffff
4ff7b:3::/32ff7b:3:ffff:ffff:ffff:ffff:ffff:ffff
5ff7b:4::/32ff7b:4:ffff:ffff:ffff:ffff:ffff:ffff
6ff7b:5::/32ff7b:5:ffff:ffff:ffff:ffff:ffff:ffff
7ff7b:6::/32ff7b:6:ffff:ffff:ffff:ffff:ffff:ffff
8ff7b:7::/32ff7b:7:ffff:ffff:ffff:ffff:ffff:ffff
9ff7b:8::/32ff7b:8:ffff:ffff:ffff:ffff:ffff:ffff
10ff7b:9::/32ff7b:9:ffff:ffff:ffff:ffff:ffff:ffff
11ff7b:a::/32ff7b:a:ffff:ffff:ffff:ffff:ffff:ffff
12ff7b:b::/32ff7b:b:ffff:ffff:ffff:ffff:ffff:ffff
13ff7b:c::/32ff7b:c:ffff:ffff:ffff:ffff:ffff:ffff
14ff7b:d::/32ff7b:d:ffff:ffff:ffff:ffff:ffff:ffff
15ff7b:e::/32ff7b:e:ffff:ffff:ffff:ffff:ffff:ffff
16ff7b:f::/32ff7b:f:ffff:ffff:ffff:ffff:ffff:ffff
17ff7b:10::/32ff7b:10:ffff:ffff:ffff:ffff:ffff:ffff
18ff7b:11::/32ff7b:11:ffff:ffff:ffff:ffff:ffff:ffff
19ff7b:12::/32ff7b:12:ffff:ffff:ffff:ffff:ffff:ffff
20ff7b:13::/32ff7b:13:ffff:ffff:ffff:ffff:ffff:ffff
21ff7b:14::/32ff7b:14:ffff:ffff:ffff:ffff:ffff:ffff
22ff7b:15::/32ff7b:15:ffff:ffff:ffff:ffff:ffff:ffff
23ff7b:16::/32ff7b:16:ffff:ffff:ffff:ffff:ffff:ffff
24ff7b:17::/32ff7b:17:ffff:ffff:ffff:ffff:ffff:ffff
25ff7b:18::/32ff7b:18:ffff:ffff:ffff:ffff:ffff:ffff
26ff7b:19::/32ff7b:19:ffff:ffff:ffff:ffff:ffff:ffff
27ff7b:1a::/32ff7b:1a:ffff:ffff:ffff:ffff:ffff:ffff
28ff7b:1b::/32ff7b:1b:ffff:ffff:ffff:ffff:ffff:ffff
29ff7b:1c::/32ff7b:1c:ffff:ffff:ffff:ffff:ffff:ffff
30ff7b:1d::/32ff7b:1d:ffff:ffff:ffff:ffff:ffff:ffff
31ff7b:1e::/32ff7b:1e:ffff:ffff:ffff:ffff:ffff:ffff
32ff7b:1f::/32ff7b:1f:ffff:ffff:ffff:ffff:ffff:ffff
33ff7b:20::/32ff7b:20:ffff:ffff:ffff:ffff:ffff:ffff
34ff7b:21::/32ff7b:21:ffff:ffff:ffff:ffff:ffff:ffff
35ff7b:22::/32ff7b:22:ffff:ffff:ffff:ffff:ffff:ffff
36ff7b:23::/32ff7b:23:ffff:ffff:ffff:ffff:ffff:ffff
37ff7b:24::/32ff7b:24:ffff:ffff:ffff:ffff:ffff:ffff
38ff7b:25::/32ff7b:25:ffff:ffff:ffff:ffff:ffff:ffff
39ff7b:26::/32ff7b:26:ffff:ffff:ffff:ffff:ffff:ffff
40ff7b:27::/32ff7b:27:ffff:ffff:ffff:ffff:ffff:ffff
41ff7b:28::/32ff7b:28:ffff:ffff:ffff:ffff:ffff:ffff
42ff7b:29::/32ff7b:29:ffff:ffff:ffff:ffff:ffff:ffff
43ff7b:2a::/32ff7b:2a:ffff:ffff:ffff:ffff:ffff:ffff
44ff7b:2b::/32ff7b:2b:ffff:ffff:ffff:ffff:ffff:ffff
45ff7b:2c::/32ff7b:2c:ffff:ffff:ffff:ffff:ffff:ffff
46ff7b:2d::/32ff7b:2d:ffff:ffff:ffff:ffff:ffff:ffff
47ff7b:2e::/32ff7b:2e:ffff:ffff:ffff:ffff:ffff:ffff
48ff7b:2f::/32ff7b:2f:ffff:ffff:ffff:ffff:ffff:ffff
49ff7b:30::/32ff7b:30:ffff:ffff:ffff:ffff:ffff:ffff
50ff7b:31::/32ff7b:31:ffff:ffff:ffff:ffff:ffff:ffff
51ff7b:32::/32ff7b:32:ffff:ffff:ffff:ffff:ffff:ffff
52ff7b:33::/32ff7b:33:ffff:ffff:ffff:ffff:ffff:ffff
53ff7b:34::/32ff7b:34:ffff:ffff:ffff:ffff:ffff:ffff
54ff7b:35::/32ff7b:35:ffff:ffff:ffff:ffff:ffff:ffff
55ff7b:36::/32ff7b:36:ffff:ffff:ffff:ffff:ffff:ffff
56ff7b:37::/32ff7b:37:ffff:ffff:ffff:ffff:ffff:ffff
57ff7b:38::/32ff7b:38:ffff:ffff:ffff:ffff:ffff:ffff
58ff7b:39::/32ff7b:39:ffff:ffff:ffff:ffff:ffff:ffff
59ff7b:3a::/32ff7b:3a:ffff:ffff:ffff:ffff:ffff:ffff
60ff7b:3b::/32ff7b:3b:ffff:ffff:ffff:ffff:ffff:ffff
61ff7b:3c::/32ff7b:3c:ffff:ffff:ffff:ffff:ffff:ffff
62ff7b:3d::/32ff7b:3d:ffff:ffff:ffff:ffff:ffff:ffff
63ff7b:3e::/32ff7b:3e:ffff:ffff:ffff:ffff:ffff:ffff
64ff7b:3f::/32ff7b:3f:ffff:ffff:ffff:ffff:ffff:ffff
65ff7b:40::/32ff7b:40:ffff:ffff:ffff:ffff:ffff:ffff
66ff7b:41::/32ff7b:41:ffff:ffff:ffff:ffff:ffff:ffff
67ff7b:42::/32ff7b:42:ffff:ffff:ffff:ffff:ffff:ffff
68ff7b:43::/32ff7b:43:ffff:ffff:ffff:ffff:ffff:ffff
69ff7b:44::/32ff7b:44:ffff:ffff:ffff:ffff:ffff:ffff
70ff7b:45::/32ff7b:45:ffff:ffff:ffff:ffff:ffff:ffff
71ff7b:46::/32ff7b:46:ffff:ffff:ffff:ffff:ffff:ffff
72ff7b:47::/32ff7b:47:ffff:ffff:ffff:ffff:ffff:ffff
73ff7b:48::/32ff7b:48:ffff:ffff:ffff:ffff:ffff:ffff
74ff7b:49::/32ff7b:49:ffff:ffff:ffff:ffff:ffff:ffff
75ff7b:4a::/32ff7b:4a:ffff:ffff:ffff:ffff:ffff:ffff
76ff7b:4b::/32ff7b:4b:ffff:ffff:ffff:ffff:ffff:ffff
77ff7b:4c::/32ff7b:4c:ffff:ffff:ffff:ffff:ffff:ffff
78ff7b:4d::/32ff7b:4d:ffff:ffff:ffff:ffff:ffff:ffff
79ff7b:4e::/32ff7b:4e:ffff:ffff:ffff:ffff:ffff:ffff
80ff7b:4f::/32ff7b:4f:ffff:ffff:ffff:ffff:ffff:ffff
81ff7b:50::/32ff7b:50:ffff:ffff:ffff:ffff:ffff:ffff
82ff7b:51::/32ff7b:51:ffff:ffff:ffff:ffff:ffff:ffff
83ff7b:52::/32ff7b:52:ffff:ffff:ffff:ffff:ffff:ffff
84ff7b:53::/32ff7b:53:ffff:ffff:ffff:ffff:ffff:ffff
85ff7b:54::/32ff7b:54:ffff:ffff:ffff:ffff:ffff:ffff
86ff7b:55::/32ff7b:55:ffff:ffff:ffff:ffff:ffff:ffff
87ff7b:56::/32ff7b:56:ffff:ffff:ffff:ffff:ffff:ffff
88ff7b:57::/32ff7b:57:ffff:ffff:ffff:ffff:ffff:ffff
89ff7b:58::/32ff7b:58:ffff:ffff:ffff:ffff:ffff:ffff
90ff7b:59::/32ff7b:59:ffff:ffff:ffff:ffff:ffff:ffff
91ff7b:5a::/32ff7b:5a:ffff:ffff:ffff:ffff:ffff:ffff
92ff7b:5b::/32ff7b:5b:ffff:ffff:ffff:ffff:ffff:ffff
93ff7b:5c::/32ff7b:5c:ffff:ffff:ffff:ffff:ffff:ffff
94ff7b:5d::/32ff7b:5d:ffff:ffff:ffff:ffff:ffff:ffff
95ff7b:5e::/32ff7b:5e:ffff:ffff:ffff:ffff:ffff:ffff
96ff7b:5f::/32ff7b:5f:ffff:ffff:ffff:ffff:ffff:ffff
97ff7b:60::/32ff7b:60:ffff:ffff:ffff:ffff:ffff:ffff
98ff7b:61::/32ff7b:61:ffff:ffff:ffff:ffff:ffff:ffff
99ff7b:62::/32ff7b:62:ffff:ffff:ffff:ffff:ffff:ffff
100ff7b:63::/32ff7b:63:ffff:ffff:ffff:ffff:ffff:ffff
101ff7b:64::/32ff7b:64:ffff:ffff:ffff:ffff:ffff:ffff
102ff7b:65::/32ff7b:65:ffff:ffff:ffff:ffff:ffff:ffff
103ff7b:66::/32ff7b:66:ffff:ffff:ffff:ffff:ffff:ffff
104ff7b:67::/32ff7b:67:ffff:ffff:ffff:ffff:ffff:ffff
105ff7b:68::/32ff7b:68:ffff:ffff:ffff:ffff:ffff:ffff
106ff7b:69::/32ff7b:69:ffff:ffff:ffff:ffff:ffff:ffff
107ff7b:6a::/32ff7b:6a:ffff:ffff:ffff:ffff:ffff:ffff
108ff7b:6b::/32ff7b:6b:ffff:ffff:ffff:ffff:ffff:ffff
109ff7b:6c::/32ff7b:6c:ffff:ffff:ffff:ffff:ffff:ffff
110ff7b:6d::/32ff7b:6d:ffff:ffff:ffff:ffff:ffff:ffff
111ff7b:6e::/32ff7b:6e:ffff:ffff:ffff:ffff:ffff:ffff
112ff7b:6f::/32ff7b:6f:ffff:ffff:ffff:ffff:ffff:ffff
113ff7b:70::/32ff7b:70:ffff:ffff:ffff:ffff:ffff:ffff
114ff7b:71::/32ff7b:71:ffff:ffff:ffff:ffff:ffff:ffff
115ff7b:72::/32ff7b:72:ffff:ffff:ffff:ffff:ffff:ffff
116ff7b:73::/32ff7b:73:ffff:ffff:ffff:ffff:ffff:ffff
117ff7b:74::/32ff7b:74:ffff:ffff:ffff:ffff:ffff:ffff
118ff7b:75::/32ff7b:75:ffff:ffff:ffff:ffff:ffff:ffff
119ff7b:76::/32ff7b:76:ffff:ffff:ffff:ffff:ffff:ffff
120ff7b:77::/32ff7b:77:ffff:ffff:ffff:ffff:ffff:ffff
121ff7b:78::/32ff7b:78:ffff:ffff:ffff:ffff:ffff:ffff
122ff7b:79::/32ff7b:79:ffff:ffff:ffff:ffff:ffff:ffff
123ff7b:7a::/32ff7b:7a:ffff:ffff:ffff:ffff:ffff:ffff
124ff7b:7b::/32ff7b:7b:ffff:ffff:ffff:ffff:ffff:ffff
125ff7b:7c::/32ff7b:7c:ffff:ffff:ffff:ffff:ffff:ffff
126ff7b:7d::/32ff7b:7d:ffff:ffff:ffff:ffff:ffff:ffff
127ff7b:7e::/32ff7b:7e:ffff:ffff:ffff:ffff:ffff:ffff
128ff7b:7f::/32ff7b:7f:ffff:ffff:ffff:ffff:ffff:ffff
129ff7b:80::/32ff7b:80:ffff:ffff:ffff:ffff:ffff:ffff
130ff7b:81::/32ff7b:81:ffff:ffff:ffff:ffff:ffff:ffff
131ff7b:82::/32ff7b:82:ffff:ffff:ffff:ffff:ffff:ffff
132ff7b:83::/32ff7b:83:ffff:ffff:ffff:ffff:ffff:ffff
133ff7b:84::/32ff7b:84:ffff:ffff:ffff:ffff:ffff:ffff
134ff7b:85::/32ff7b:85:ffff:ffff:ffff:ffff:ffff:ffff
135ff7b:86::/32ff7b:86:ffff:ffff:ffff:ffff:ffff:ffff
136ff7b:87::/32ff7b:87:ffff:ffff:ffff:ffff:ffff:ffff
137ff7b:88::/32ff7b:88:ffff:ffff:ffff:ffff:ffff:ffff
138ff7b:89::/32ff7b:89:ffff:ffff:ffff:ffff:ffff:ffff
139ff7b:8a::/32ff7b:8a:ffff:ffff:ffff:ffff:ffff:ffff
140ff7b:8b::/32ff7b:8b:ffff:ffff:ffff:ffff:ffff:ffff
141ff7b:8c::/32ff7b:8c:ffff:ffff:ffff:ffff:ffff:ffff
142ff7b:8d::/32ff7b:8d:ffff:ffff:ffff:ffff:ffff:ffff
143ff7b:8e::/32ff7b:8e:ffff:ffff:ffff:ffff:ffff:ffff
144ff7b:8f::/32ff7b:8f:ffff:ffff:ffff:ffff:ffff:ffff
145ff7b:90::/32ff7b:90:ffff:ffff:ffff:ffff:ffff:ffff
146ff7b:91::/32ff7b:91:ffff:ffff:ffff:ffff:ffff:ffff
147ff7b:92::/32ff7b:92:ffff:ffff:ffff:ffff:ffff:ffff
148ff7b:93::/32ff7b:93:ffff:ffff:ffff:ffff:ffff:ffff
149ff7b:94::/32ff7b:94:ffff:ffff:ffff:ffff:ffff:ffff
150ff7b:95::/32ff7b:95:ffff:ffff:ffff:ffff:ffff:ffff
151ff7b:96::/32ff7b:96:ffff:ffff:ffff:ffff:ffff:ffff
152ff7b:97::/32ff7b:97:ffff:ffff:ffff:ffff:ffff:ffff
153ff7b:98::/32ff7b:98:ffff:ffff:ffff:ffff:ffff:ffff
154ff7b:99::/32ff7b:99:ffff:ffff:ffff:ffff:ffff:ffff
155ff7b:9a::/32ff7b:9a:ffff:ffff:ffff:ffff:ffff:ffff
156ff7b:9b::/32ff7b:9b:ffff:ffff:ffff:ffff:ffff:ffff
157ff7b:9c::/32ff7b:9c:ffff:ffff:ffff:ffff:ffff:ffff
158ff7b:9d::/32ff7b:9d:ffff:ffff:ffff:ffff:ffff:ffff
159ff7b:9e::/32ff7b:9e:ffff:ffff:ffff:ffff:ffff:ffff
160ff7b:9f::/32ff7b:9f:ffff:ffff:ffff:ffff:ffff:ffff
161ff7b:a0::/32ff7b:a0:ffff:ffff:ffff:ffff:ffff:ffff
162ff7b:a1::/32ff7b:a1:ffff:ffff:ffff:ffff:ffff:ffff
163ff7b:a2::/32ff7b:a2:ffff:ffff:ffff:ffff:ffff:ffff
164ff7b:a3::/32ff7b:a3:ffff:ffff:ffff:ffff:ffff:ffff
165ff7b:a4::/32ff7b:a4:ffff:ffff:ffff:ffff:ffff:ffff
166ff7b:a5::/32ff7b:a5:ffff:ffff:ffff:ffff:ffff:ffff
167ff7b:a6::/32ff7b:a6:ffff:ffff:ffff:ffff:ffff:ffff
168ff7b:a7::/32ff7b:a7:ffff:ffff:ffff:ffff:ffff:ffff
169ff7b:a8::/32ff7b:a8:ffff:ffff:ffff:ffff:ffff:ffff
170ff7b:a9::/32ff7b:a9:ffff:ffff:ffff:ffff:ffff:ffff
171ff7b:aa::/32ff7b:aa:ffff:ffff:ffff:ffff:ffff:ffff
172ff7b:ab::/32ff7b:ab:ffff:ffff:ffff:ffff:ffff:ffff
173ff7b:ac::/32ff7b:ac:ffff:ffff:ffff:ffff:ffff:ffff
174ff7b:ad::/32ff7b:ad:ffff:ffff:ffff:ffff:ffff:ffff
175ff7b:ae::/32ff7b:ae:ffff:ffff:ffff:ffff:ffff:ffff
176ff7b:af::/32ff7b:af:ffff:ffff:ffff:ffff:ffff:ffff
177ff7b:b0::/32ff7b:b0:ffff:ffff:ffff:ffff:ffff:ffff
178ff7b:b1::/32ff7b:b1:ffff:ffff:ffff:ffff:ffff:ffff
179ff7b:b2::/32ff7b:b2:ffff:ffff:ffff:ffff:ffff:ffff
180ff7b:b3::/32ff7b:b3:ffff:ffff:ffff:ffff:ffff:ffff
181ff7b:b4::/32ff7b:b4:ffff:ffff:ffff:ffff:ffff:ffff
182ff7b:b5::/32ff7b:b5:ffff:ffff:ffff:ffff:ffff:ffff
183ff7b:b6::/32ff7b:b6:ffff:ffff:ffff:ffff:ffff:ffff
184ff7b:b7::/32ff7b:b7:ffff:ffff:ffff:ffff:ffff:ffff
185ff7b:b8::/32ff7b:b8:ffff:ffff:ffff:ffff:ffff:ffff
186ff7b:b9::/32ff7b:b9:ffff:ffff:ffff:ffff:ffff:ffff
187ff7b:ba::/32ff7b:ba:ffff:ffff:ffff:ffff:ffff:ffff
188ff7b:bb::/32ff7b:bb:ffff:ffff:ffff:ffff:ffff:ffff
189ff7b:bc::/32ff7b:bc:ffff:ffff:ffff:ffff:ffff:ffff
190ff7b:bd::/32ff7b:bd:ffff:ffff:ffff:ffff:ffff:ffff
191ff7b:be::/32ff7b:be:ffff:ffff:ffff:ffff:ffff:ffff
192ff7b:bf::/32ff7b:bf:ffff:ffff:ffff:ffff:ffff:ffff
193ff7b:c0::/32ff7b:c0:ffff:ffff:ffff:ffff:ffff:ffff
194ff7b:c1::/32ff7b:c1:ffff:ffff:ffff:ffff:ffff:ffff
195ff7b:c2::/32ff7b:c2:ffff:ffff:ffff:ffff:ffff:ffff
196ff7b:c3::/32ff7b:c3:ffff:ffff:ffff:ffff:ffff:ffff
197ff7b:c4::/32ff7b:c4:ffff:ffff:ffff:ffff:ffff:ffff
198ff7b:c5::/32ff7b:c5:ffff:ffff:ffff:ffff:ffff:ffff
199ff7b:c6::/32ff7b:c6:ffff:ffff:ffff:ffff:ffff:ffff
200ff7b:c7::/32ff7b:c7:ffff:ffff:ffff:ffff:ffff:ffff
201ff7b:c8::/32ff7b:c8:ffff:ffff:ffff:ffff:ffff:ffff
202ff7b:c9::/32ff7b:c9:ffff:ffff:ffff:ffff:ffff:ffff
203ff7b:ca::/32ff7b:ca:ffff:ffff:ffff:ffff:ffff:ffff
204ff7b:cb::/32ff7b:cb:ffff:ffff:ffff:ffff:ffff:ffff
205ff7b:cc::/32ff7b:cc:ffff:ffff:ffff:ffff:ffff:ffff
206ff7b:cd::/32ff7b:cd:ffff:ffff:ffff:ffff:ffff:ffff
207ff7b:ce::/32ff7b:ce:ffff:ffff:ffff:ffff:ffff:ffff
208ff7b:cf::/32ff7b:cf:ffff:ffff:ffff:ffff:ffff:ffff
209ff7b:d0::/32ff7b:d0:ffff:ffff:ffff:ffff:ffff:ffff
210ff7b:d1::/32ff7b:d1:ffff:ffff:ffff:ffff:ffff:ffff
211ff7b:d2::/32ff7b:d2:ffff:ffff:ffff:ffff:ffff:ffff
212ff7b:d3::/32ff7b:d3:ffff:ffff:ffff:ffff:ffff:ffff
213ff7b:d4::/32ff7b:d4:ffff:ffff:ffff:ffff:ffff:ffff
214ff7b:d5::/32ff7b:d5:ffff:ffff:ffff:ffff:ffff:ffff
215ff7b:d6::/32ff7b:d6:ffff:ffff:ffff:ffff:ffff:ffff
216ff7b:d7::/32ff7b:d7:ffff:ffff:ffff:ffff:ffff:ffff
217ff7b:d8::/32ff7b:d8:ffff:ffff:ffff:ffff:ffff:ffff
218ff7b:d9::/32ff7b:d9:ffff:ffff:ffff:ffff:ffff:ffff
219ff7b:da::/32ff7b:da:ffff:ffff:ffff:ffff:ffff:ffff
220ff7b:db::/32ff7b:db:ffff:ffff:ffff:ffff:ffff:ffff
221ff7b:dc::/32ff7b:dc:ffff:ffff:ffff:ffff:ffff:ffff
222ff7b:dd::/32ff7b:dd:ffff:ffff:ffff:ffff:ffff:ffff
223ff7b:de::/32ff7b:de:ffff:ffff:ffff:ffff:ffff:ffff
224ff7b:df::/32ff7b:df:ffff:ffff:ffff:ffff:ffff:ffff
225ff7b:e0::/32ff7b:e0:ffff:ffff:ffff:ffff:ffff:ffff
226ff7b:e1::/32ff7b:e1:ffff:ffff:ffff:ffff:ffff:ffff
227ff7b:e2::/32ff7b:e2:ffff:ffff:ffff:ffff:ffff:ffff
228ff7b:e3::/32ff7b:e3:ffff:ffff:ffff:ffff:ffff:ffff
229ff7b:e4::/32ff7b:e4:ffff:ffff:ffff:ffff:ffff:ffff
230ff7b:e5::/32ff7b:e5:ffff:ffff:ffff:ffff:ffff:ffff
231ff7b:e6::/32ff7b:e6:ffff:ffff:ffff:ffff:ffff:ffff
232ff7b:e7::/32ff7b:e7:ffff:ffff:ffff:ffff:ffff:ffff
233ff7b:e8::/32ff7b:e8:ffff:ffff:ffff:ffff:ffff:ffff
234ff7b:e9::/32ff7b:e9:ffff:ffff:ffff:ffff:ffff:ffff
235ff7b:ea::/32ff7b:ea:ffff:ffff:ffff:ffff:ffff:ffff
236ff7b:eb::/32ff7b:eb:ffff:ffff:ffff:ffff:ffff:ffff
237ff7b:ec::/32ff7b:ec:ffff:ffff:ffff:ffff:ffff:ffff
238ff7b:ed::/32ff7b:ed:ffff:ffff:ffff:ffff:ffff:ffff
239ff7b:ee::/32ff7b:ee:ffff:ffff:ffff:ffff:ffff:ffff
240ff7b:ef::/32ff7b:ef:ffff:ffff:ffff:ffff:ffff:ffff
241ff7b:f0::/32ff7b:f0:ffff:ffff:ffff:ffff:ffff:ffff
242ff7b:f1::/32ff7b:f1:ffff:ffff:ffff:ffff:ffff:ffff
243ff7b:f2::/32ff7b:f2:ffff:ffff:ffff:ffff:ffff:ffff
244ff7b:f3::/32ff7b:f3:ffff:ffff:ffff:ffff:ffff:ffff
245ff7b:f4::/32ff7b:f4:ffff:ffff:ffff:ffff:ffff:ffff
246ff7b:f5::/32ff7b:f5:ffff:ffff:ffff:ffff:ffff:ffff
247ff7b:f6::/32ff7b:f6:ffff:ffff:ffff:ffff:ffff:ffff
248ff7b:f7::/32ff7b:f7:ffff:ffff:ffff:ffff:ffff:ffff
249ff7b:f8::/32ff7b:f8:ffff:ffff:ffff:ffff:ffff:ffff
250ff7b:f9::/32ff7b:f9:ffff:ffff:ffff:ffff:ffff:ffff
251ff7b:fa::/32ff7b:fa:ffff:ffff:ffff:ffff:ffff:ffff
252ff7b:fb::/32ff7b:fb:ffff:ffff:ffff:ffff:ffff:ffff
253ff7b:fc::/32ff7b:fc:ffff:ffff:ffff:ffff:ffff:ffff
254ff7b:fd::/32ff7b:fd:ffff:ffff:ffff:ffff:ffff:ffff
255ff7b:fe::/32ff7b:fe:ffff:ffff:ffff:ffff:ffff:ffff
256ff7b:ff::/32ff7b:ff:ffff:ffff:ffff:ffff:ffff:ffff

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.