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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.

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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.

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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
ff1d::/16
First address
ff1d::
Last address
ff1d: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
ff1d:0000:0000:0000:0000:0000:0000:0000
Type
Multicast ff00::/8
One-to-many traffic; replaces broadcast
Reverse DNS zone
d.1.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)

ff1d::/16 makes 65,536 subnets of /32; the first 256 are listed.

Subnets
#SubnetLast address
1ff1d::/32ff1d:0:ffff:ffff:ffff:ffff:ffff:ffff
2ff1d:1::/32ff1d:1:ffff:ffff:ffff:ffff:ffff:ffff
3ff1d:2::/32ff1d:2:ffff:ffff:ffff:ffff:ffff:ffff
4ff1d:3::/32ff1d:3:ffff:ffff:ffff:ffff:ffff:ffff
5ff1d:4::/32ff1d:4:ffff:ffff:ffff:ffff:ffff:ffff
6ff1d:5::/32ff1d:5:ffff:ffff:ffff:ffff:ffff:ffff
7ff1d:6::/32ff1d:6:ffff:ffff:ffff:ffff:ffff:ffff
8ff1d:7::/32ff1d:7:ffff:ffff:ffff:ffff:ffff:ffff
9ff1d:8::/32ff1d:8:ffff:ffff:ffff:ffff:ffff:ffff
10ff1d:9::/32ff1d:9:ffff:ffff:ffff:ffff:ffff:ffff
11ff1d:a::/32ff1d:a:ffff:ffff:ffff:ffff:ffff:ffff
12ff1d:b::/32ff1d:b:ffff:ffff:ffff:ffff:ffff:ffff
13ff1d:c::/32ff1d:c:ffff:ffff:ffff:ffff:ffff:ffff
14ff1d:d::/32ff1d:d:ffff:ffff:ffff:ffff:ffff:ffff
15ff1d:e::/32ff1d:e:ffff:ffff:ffff:ffff:ffff:ffff
16ff1d:f::/32ff1d:f:ffff:ffff:ffff:ffff:ffff:ffff
17ff1d:10::/32ff1d:10:ffff:ffff:ffff:ffff:ffff:ffff
18ff1d:11::/32ff1d:11:ffff:ffff:ffff:ffff:ffff:ffff
19ff1d:12::/32ff1d:12:ffff:ffff:ffff:ffff:ffff:ffff
20ff1d:13::/32ff1d:13:ffff:ffff:ffff:ffff:ffff:ffff
21ff1d:14::/32ff1d:14:ffff:ffff:ffff:ffff:ffff:ffff
22ff1d:15::/32ff1d:15:ffff:ffff:ffff:ffff:ffff:ffff
23ff1d:16::/32ff1d:16:ffff:ffff:ffff:ffff:ffff:ffff
24ff1d:17::/32ff1d:17:ffff:ffff:ffff:ffff:ffff:ffff
25ff1d:18::/32ff1d:18:ffff:ffff:ffff:ffff:ffff:ffff
26ff1d:19::/32ff1d:19:ffff:ffff:ffff:ffff:ffff:ffff
27ff1d:1a::/32ff1d:1a:ffff:ffff:ffff:ffff:ffff:ffff
28ff1d:1b::/32ff1d:1b:ffff:ffff:ffff:ffff:ffff:ffff
29ff1d:1c::/32ff1d:1c:ffff:ffff:ffff:ffff:ffff:ffff
30ff1d:1d::/32ff1d:1d:ffff:ffff:ffff:ffff:ffff:ffff
31ff1d:1e::/32ff1d:1e:ffff:ffff:ffff:ffff:ffff:ffff
32ff1d:1f::/32ff1d:1f:ffff:ffff:ffff:ffff:ffff:ffff
33ff1d:20::/32ff1d:20:ffff:ffff:ffff:ffff:ffff:ffff
34ff1d:21::/32ff1d:21:ffff:ffff:ffff:ffff:ffff:ffff
35ff1d:22::/32ff1d:22:ffff:ffff:ffff:ffff:ffff:ffff
36ff1d:23::/32ff1d:23:ffff:ffff:ffff:ffff:ffff:ffff
37ff1d:24::/32ff1d:24:ffff:ffff:ffff:ffff:ffff:ffff
38ff1d:25::/32ff1d:25:ffff:ffff:ffff:ffff:ffff:ffff
39ff1d:26::/32ff1d:26:ffff:ffff:ffff:ffff:ffff:ffff
40ff1d:27::/32ff1d:27:ffff:ffff:ffff:ffff:ffff:ffff
41ff1d:28::/32ff1d:28:ffff:ffff:ffff:ffff:ffff:ffff
42ff1d:29::/32ff1d:29:ffff:ffff:ffff:ffff:ffff:ffff
43ff1d:2a::/32ff1d:2a:ffff:ffff:ffff:ffff:ffff:ffff
44ff1d:2b::/32ff1d:2b:ffff:ffff:ffff:ffff:ffff:ffff
45ff1d:2c::/32ff1d:2c:ffff:ffff:ffff:ffff:ffff:ffff
46ff1d:2d::/32ff1d:2d:ffff:ffff:ffff:ffff:ffff:ffff
47ff1d:2e::/32ff1d:2e:ffff:ffff:ffff:ffff:ffff:ffff
48ff1d:2f::/32ff1d:2f:ffff:ffff:ffff:ffff:ffff:ffff
49ff1d:30::/32ff1d:30:ffff:ffff:ffff:ffff:ffff:ffff
50ff1d:31::/32ff1d:31:ffff:ffff:ffff:ffff:ffff:ffff
51ff1d:32::/32ff1d:32:ffff:ffff:ffff:ffff:ffff:ffff
52ff1d:33::/32ff1d:33:ffff:ffff:ffff:ffff:ffff:ffff
53ff1d:34::/32ff1d:34:ffff:ffff:ffff:ffff:ffff:ffff
54ff1d:35::/32ff1d:35:ffff:ffff:ffff:ffff:ffff:ffff
55ff1d:36::/32ff1d:36:ffff:ffff:ffff:ffff:ffff:ffff
56ff1d:37::/32ff1d:37:ffff:ffff:ffff:ffff:ffff:ffff
57ff1d:38::/32ff1d:38:ffff:ffff:ffff:ffff:ffff:ffff
58ff1d:39::/32ff1d:39:ffff:ffff:ffff:ffff:ffff:ffff
59ff1d:3a::/32ff1d:3a:ffff:ffff:ffff:ffff:ffff:ffff
60ff1d:3b::/32ff1d:3b:ffff:ffff:ffff:ffff:ffff:ffff
61ff1d:3c::/32ff1d:3c:ffff:ffff:ffff:ffff:ffff:ffff
62ff1d:3d::/32ff1d:3d:ffff:ffff:ffff:ffff:ffff:ffff
63ff1d:3e::/32ff1d:3e:ffff:ffff:ffff:ffff:ffff:ffff
64ff1d:3f::/32ff1d:3f:ffff:ffff:ffff:ffff:ffff:ffff
65ff1d:40::/32ff1d:40:ffff:ffff:ffff:ffff:ffff:ffff
66ff1d:41::/32ff1d:41:ffff:ffff:ffff:ffff:ffff:ffff
67ff1d:42::/32ff1d:42:ffff:ffff:ffff:ffff:ffff:ffff
68ff1d:43::/32ff1d:43:ffff:ffff:ffff:ffff:ffff:ffff
69ff1d:44::/32ff1d:44:ffff:ffff:ffff:ffff:ffff:ffff
70ff1d:45::/32ff1d:45:ffff:ffff:ffff:ffff:ffff:ffff
71ff1d:46::/32ff1d:46:ffff:ffff:ffff:ffff:ffff:ffff
72ff1d:47::/32ff1d:47:ffff:ffff:ffff:ffff:ffff:ffff
73ff1d:48::/32ff1d:48:ffff:ffff:ffff:ffff:ffff:ffff
74ff1d:49::/32ff1d:49:ffff:ffff:ffff:ffff:ffff:ffff
75ff1d:4a::/32ff1d:4a:ffff:ffff:ffff:ffff:ffff:ffff
76ff1d:4b::/32ff1d:4b:ffff:ffff:ffff:ffff:ffff:ffff
77ff1d:4c::/32ff1d:4c:ffff:ffff:ffff:ffff:ffff:ffff
78ff1d:4d::/32ff1d:4d:ffff:ffff:ffff:ffff:ffff:ffff
79ff1d:4e::/32ff1d:4e:ffff:ffff:ffff:ffff:ffff:ffff
80ff1d:4f::/32ff1d:4f:ffff:ffff:ffff:ffff:ffff:ffff
81ff1d:50::/32ff1d:50:ffff:ffff:ffff:ffff:ffff:ffff
82ff1d:51::/32ff1d:51:ffff:ffff:ffff:ffff:ffff:ffff
83ff1d:52::/32ff1d:52:ffff:ffff:ffff:ffff:ffff:ffff
84ff1d:53::/32ff1d:53:ffff:ffff:ffff:ffff:ffff:ffff
85ff1d:54::/32ff1d:54:ffff:ffff:ffff:ffff:ffff:ffff
86ff1d:55::/32ff1d:55:ffff:ffff:ffff:ffff:ffff:ffff
87ff1d:56::/32ff1d:56:ffff:ffff:ffff:ffff:ffff:ffff
88ff1d:57::/32ff1d:57:ffff:ffff:ffff:ffff:ffff:ffff
89ff1d:58::/32ff1d:58:ffff:ffff:ffff:ffff:ffff:ffff
90ff1d:59::/32ff1d:59:ffff:ffff:ffff:ffff:ffff:ffff
91ff1d:5a::/32ff1d:5a:ffff:ffff:ffff:ffff:ffff:ffff
92ff1d:5b::/32ff1d:5b:ffff:ffff:ffff:ffff:ffff:ffff
93ff1d:5c::/32ff1d:5c:ffff:ffff:ffff:ffff:ffff:ffff
94ff1d:5d::/32ff1d:5d:ffff:ffff:ffff:ffff:ffff:ffff
95ff1d:5e::/32ff1d:5e:ffff:ffff:ffff:ffff:ffff:ffff
96ff1d:5f::/32ff1d:5f:ffff:ffff:ffff:ffff:ffff:ffff
97ff1d:60::/32ff1d:60:ffff:ffff:ffff:ffff:ffff:ffff
98ff1d:61::/32ff1d:61:ffff:ffff:ffff:ffff:ffff:ffff
99ff1d:62::/32ff1d:62:ffff:ffff:ffff:ffff:ffff:ffff
100ff1d:63::/32ff1d:63:ffff:ffff:ffff:ffff:ffff:ffff
101ff1d:64::/32ff1d:64:ffff:ffff:ffff:ffff:ffff:ffff
102ff1d:65::/32ff1d:65:ffff:ffff:ffff:ffff:ffff:ffff
103ff1d:66::/32ff1d:66:ffff:ffff:ffff:ffff:ffff:ffff
104ff1d:67::/32ff1d:67:ffff:ffff:ffff:ffff:ffff:ffff
105ff1d:68::/32ff1d:68:ffff:ffff:ffff:ffff:ffff:ffff
106ff1d:69::/32ff1d:69:ffff:ffff:ffff:ffff:ffff:ffff
107ff1d:6a::/32ff1d:6a:ffff:ffff:ffff:ffff:ffff:ffff
108ff1d:6b::/32ff1d:6b:ffff:ffff:ffff:ffff:ffff:ffff
109ff1d:6c::/32ff1d:6c:ffff:ffff:ffff:ffff:ffff:ffff
110ff1d:6d::/32ff1d:6d:ffff:ffff:ffff:ffff:ffff:ffff
111ff1d:6e::/32ff1d:6e:ffff:ffff:ffff:ffff:ffff:ffff
112ff1d:6f::/32ff1d:6f:ffff:ffff:ffff:ffff:ffff:ffff
113ff1d:70::/32ff1d:70:ffff:ffff:ffff:ffff:ffff:ffff
114ff1d:71::/32ff1d:71:ffff:ffff:ffff:ffff:ffff:ffff
115ff1d:72::/32ff1d:72:ffff:ffff:ffff:ffff:ffff:ffff
116ff1d:73::/32ff1d:73:ffff:ffff:ffff:ffff:ffff:ffff
117ff1d:74::/32ff1d:74:ffff:ffff:ffff:ffff:ffff:ffff
118ff1d:75::/32ff1d:75:ffff:ffff:ffff:ffff:ffff:ffff
119ff1d:76::/32ff1d:76:ffff:ffff:ffff:ffff:ffff:ffff
120ff1d:77::/32ff1d:77:ffff:ffff:ffff:ffff:ffff:ffff
121ff1d:78::/32ff1d:78:ffff:ffff:ffff:ffff:ffff:ffff
122ff1d:79::/32ff1d:79:ffff:ffff:ffff:ffff:ffff:ffff
123ff1d:7a::/32ff1d:7a:ffff:ffff:ffff:ffff:ffff:ffff
124ff1d:7b::/32ff1d:7b:ffff:ffff:ffff:ffff:ffff:ffff
125ff1d:7c::/32ff1d:7c:ffff:ffff:ffff:ffff:ffff:ffff
126ff1d:7d::/32ff1d:7d:ffff:ffff:ffff:ffff:ffff:ffff
127ff1d:7e::/32ff1d:7e:ffff:ffff:ffff:ffff:ffff:ffff
128ff1d:7f::/32ff1d:7f:ffff:ffff:ffff:ffff:ffff:ffff
129ff1d:80::/32ff1d:80:ffff:ffff:ffff:ffff:ffff:ffff
130ff1d:81::/32ff1d:81:ffff:ffff:ffff:ffff:ffff:ffff
131ff1d:82::/32ff1d:82:ffff:ffff:ffff:ffff:ffff:ffff
132ff1d:83::/32ff1d:83:ffff:ffff:ffff:ffff:ffff:ffff
133ff1d:84::/32ff1d:84:ffff:ffff:ffff:ffff:ffff:ffff
134ff1d:85::/32ff1d:85:ffff:ffff:ffff:ffff:ffff:ffff
135ff1d:86::/32ff1d:86:ffff:ffff:ffff:ffff:ffff:ffff
136ff1d:87::/32ff1d:87:ffff:ffff:ffff:ffff:ffff:ffff
137ff1d:88::/32ff1d:88:ffff:ffff:ffff:ffff:ffff:ffff
138ff1d:89::/32ff1d:89:ffff:ffff:ffff:ffff:ffff:ffff
139ff1d:8a::/32ff1d:8a:ffff:ffff:ffff:ffff:ffff:ffff
140ff1d:8b::/32ff1d:8b:ffff:ffff:ffff:ffff:ffff:ffff
141ff1d:8c::/32ff1d:8c:ffff:ffff:ffff:ffff:ffff:ffff
142ff1d:8d::/32ff1d:8d:ffff:ffff:ffff:ffff:ffff:ffff
143ff1d:8e::/32ff1d:8e:ffff:ffff:ffff:ffff:ffff:ffff
144ff1d:8f::/32ff1d:8f:ffff:ffff:ffff:ffff:ffff:ffff
145ff1d:90::/32ff1d:90:ffff:ffff:ffff:ffff:ffff:ffff
146ff1d:91::/32ff1d:91:ffff:ffff:ffff:ffff:ffff:ffff
147ff1d:92::/32ff1d:92:ffff:ffff:ffff:ffff:ffff:ffff
148ff1d:93::/32ff1d:93:ffff:ffff:ffff:ffff:ffff:ffff
149ff1d:94::/32ff1d:94:ffff:ffff:ffff:ffff:ffff:ffff
150ff1d:95::/32ff1d:95:ffff:ffff:ffff:ffff:ffff:ffff
151ff1d:96::/32ff1d:96:ffff:ffff:ffff:ffff:ffff:ffff
152ff1d:97::/32ff1d:97:ffff:ffff:ffff:ffff:ffff:ffff
153ff1d:98::/32ff1d:98:ffff:ffff:ffff:ffff:ffff:ffff
154ff1d:99::/32ff1d:99:ffff:ffff:ffff:ffff:ffff:ffff
155ff1d:9a::/32ff1d:9a:ffff:ffff:ffff:ffff:ffff:ffff
156ff1d:9b::/32ff1d:9b:ffff:ffff:ffff:ffff:ffff:ffff
157ff1d:9c::/32ff1d:9c:ffff:ffff:ffff:ffff:ffff:ffff
158ff1d:9d::/32ff1d:9d:ffff:ffff:ffff:ffff:ffff:ffff
159ff1d:9e::/32ff1d:9e:ffff:ffff:ffff:ffff:ffff:ffff
160ff1d:9f::/32ff1d:9f:ffff:ffff:ffff:ffff:ffff:ffff
161ff1d:a0::/32ff1d:a0:ffff:ffff:ffff:ffff:ffff:ffff
162ff1d:a1::/32ff1d:a1:ffff:ffff:ffff:ffff:ffff:ffff
163ff1d:a2::/32ff1d:a2:ffff:ffff:ffff:ffff:ffff:ffff
164ff1d:a3::/32ff1d:a3:ffff:ffff:ffff:ffff:ffff:ffff
165ff1d:a4::/32ff1d:a4:ffff:ffff:ffff:ffff:ffff:ffff
166ff1d:a5::/32ff1d:a5:ffff:ffff:ffff:ffff:ffff:ffff
167ff1d:a6::/32ff1d:a6:ffff:ffff:ffff:ffff:ffff:ffff
168ff1d:a7::/32ff1d:a7:ffff:ffff:ffff:ffff:ffff:ffff
169ff1d:a8::/32ff1d:a8:ffff:ffff:ffff:ffff:ffff:ffff
170ff1d:a9::/32ff1d:a9:ffff:ffff:ffff:ffff:ffff:ffff
171ff1d:aa::/32ff1d:aa:ffff:ffff:ffff:ffff:ffff:ffff
172ff1d:ab::/32ff1d:ab:ffff:ffff:ffff:ffff:ffff:ffff
173ff1d:ac::/32ff1d:ac:ffff:ffff:ffff:ffff:ffff:ffff
174ff1d:ad::/32ff1d:ad:ffff:ffff:ffff:ffff:ffff:ffff
175ff1d:ae::/32ff1d:ae:ffff:ffff:ffff:ffff:ffff:ffff
176ff1d:af::/32ff1d:af:ffff:ffff:ffff:ffff:ffff:ffff
177ff1d:b0::/32ff1d:b0:ffff:ffff:ffff:ffff:ffff:ffff
178ff1d:b1::/32ff1d:b1:ffff:ffff:ffff:ffff:ffff:ffff
179ff1d:b2::/32ff1d:b2:ffff:ffff:ffff:ffff:ffff:ffff
180ff1d:b3::/32ff1d:b3:ffff:ffff:ffff:ffff:ffff:ffff
181ff1d:b4::/32ff1d:b4:ffff:ffff:ffff:ffff:ffff:ffff
182ff1d:b5::/32ff1d:b5:ffff:ffff:ffff:ffff:ffff:ffff
183ff1d:b6::/32ff1d:b6:ffff:ffff:ffff:ffff:ffff:ffff
184ff1d:b7::/32ff1d:b7:ffff:ffff:ffff:ffff:ffff:ffff
185ff1d:b8::/32ff1d:b8:ffff:ffff:ffff:ffff:ffff:ffff
186ff1d:b9::/32ff1d:b9:ffff:ffff:ffff:ffff:ffff:ffff
187ff1d:ba::/32ff1d:ba:ffff:ffff:ffff:ffff:ffff:ffff
188ff1d:bb::/32ff1d:bb:ffff:ffff:ffff:ffff:ffff:ffff
189ff1d:bc::/32ff1d:bc:ffff:ffff:ffff:ffff:ffff:ffff
190ff1d:bd::/32ff1d:bd:ffff:ffff:ffff:ffff:ffff:ffff
191ff1d:be::/32ff1d:be:ffff:ffff:ffff:ffff:ffff:ffff
192ff1d:bf::/32ff1d:bf:ffff:ffff:ffff:ffff:ffff:ffff
193ff1d:c0::/32ff1d:c0:ffff:ffff:ffff:ffff:ffff:ffff
194ff1d:c1::/32ff1d:c1:ffff:ffff:ffff:ffff:ffff:ffff
195ff1d:c2::/32ff1d:c2:ffff:ffff:ffff:ffff:ffff:ffff
196ff1d:c3::/32ff1d:c3:ffff:ffff:ffff:ffff:ffff:ffff
197ff1d:c4::/32ff1d:c4:ffff:ffff:ffff:ffff:ffff:ffff
198ff1d:c5::/32ff1d:c5:ffff:ffff:ffff:ffff:ffff:ffff
199ff1d:c6::/32ff1d:c6:ffff:ffff:ffff:ffff:ffff:ffff
200ff1d:c7::/32ff1d:c7:ffff:ffff:ffff:ffff:ffff:ffff
201ff1d:c8::/32ff1d:c8:ffff:ffff:ffff:ffff:ffff:ffff
202ff1d:c9::/32ff1d:c9:ffff:ffff:ffff:ffff:ffff:ffff
203ff1d:ca::/32ff1d:ca:ffff:ffff:ffff:ffff:ffff:ffff
204ff1d:cb::/32ff1d:cb:ffff:ffff:ffff:ffff:ffff:ffff
205ff1d:cc::/32ff1d:cc:ffff:ffff:ffff:ffff:ffff:ffff
206ff1d:cd::/32ff1d:cd:ffff:ffff:ffff:ffff:ffff:ffff
207ff1d:ce::/32ff1d:ce:ffff:ffff:ffff:ffff:ffff:ffff
208ff1d:cf::/32ff1d:cf:ffff:ffff:ffff:ffff:ffff:ffff
209ff1d:d0::/32ff1d:d0:ffff:ffff:ffff:ffff:ffff:ffff
210ff1d:d1::/32ff1d:d1:ffff:ffff:ffff:ffff:ffff:ffff
211ff1d:d2::/32ff1d:d2:ffff:ffff:ffff:ffff:ffff:ffff
212ff1d:d3::/32ff1d:d3:ffff:ffff:ffff:ffff:ffff:ffff
213ff1d:d4::/32ff1d:d4:ffff:ffff:ffff:ffff:ffff:ffff
214ff1d:d5::/32ff1d:d5:ffff:ffff:ffff:ffff:ffff:ffff
215ff1d:d6::/32ff1d:d6:ffff:ffff:ffff:ffff:ffff:ffff
216ff1d:d7::/32ff1d:d7:ffff:ffff:ffff:ffff:ffff:ffff
217ff1d:d8::/32ff1d:d8:ffff:ffff:ffff:ffff:ffff:ffff
218ff1d:d9::/32ff1d:d9:ffff:ffff:ffff:ffff:ffff:ffff
219ff1d:da::/32ff1d:da:ffff:ffff:ffff:ffff:ffff:ffff
220ff1d:db::/32ff1d:db:ffff:ffff:ffff:ffff:ffff:ffff
221ff1d:dc::/32ff1d:dc:ffff:ffff:ffff:ffff:ffff:ffff
222ff1d:dd::/32ff1d:dd:ffff:ffff:ffff:ffff:ffff:ffff
223ff1d:de::/32ff1d:de:ffff:ffff:ffff:ffff:ffff:ffff
224ff1d:df::/32ff1d:df:ffff:ffff:ffff:ffff:ffff:ffff
225ff1d:e0::/32ff1d:e0:ffff:ffff:ffff:ffff:ffff:ffff
226ff1d:e1::/32ff1d:e1:ffff:ffff:ffff:ffff:ffff:ffff
227ff1d:e2::/32ff1d:e2:ffff:ffff:ffff:ffff:ffff:ffff
228ff1d:e3::/32ff1d:e3:ffff:ffff:ffff:ffff:ffff:ffff
229ff1d:e4::/32ff1d:e4:ffff:ffff:ffff:ffff:ffff:ffff
230ff1d:e5::/32ff1d:e5:ffff:ffff:ffff:ffff:ffff:ffff
231ff1d:e6::/32ff1d:e6:ffff:ffff:ffff:ffff:ffff:ffff
232ff1d:e7::/32ff1d:e7:ffff:ffff:ffff:ffff:ffff:ffff
233ff1d:e8::/32ff1d:e8:ffff:ffff:ffff:ffff:ffff:ffff
234ff1d:e9::/32ff1d:e9:ffff:ffff:ffff:ffff:ffff:ffff
235ff1d:ea::/32ff1d:ea:ffff:ffff:ffff:ffff:ffff:ffff
236ff1d:eb::/32ff1d:eb:ffff:ffff:ffff:ffff:ffff:ffff
237ff1d:ec::/32ff1d:ec:ffff:ffff:ffff:ffff:ffff:ffff
238ff1d:ed::/32ff1d:ed:ffff:ffff:ffff:ffff:ffff:ffff
239ff1d:ee::/32ff1d:ee:ffff:ffff:ffff:ffff:ffff:ffff
240ff1d:ef::/32ff1d:ef:ffff:ffff:ffff:ffff:ffff:ffff
241ff1d:f0::/32ff1d:f0:ffff:ffff:ffff:ffff:ffff:ffff
242ff1d:f1::/32ff1d:f1:ffff:ffff:ffff:ffff:ffff:ffff
243ff1d:f2::/32ff1d:f2:ffff:ffff:ffff:ffff:ffff:ffff
244ff1d:f3::/32ff1d:f3:ffff:ffff:ffff:ffff:ffff:ffff
245ff1d:f4::/32ff1d:f4:ffff:ffff:ffff:ffff:ffff:ffff
246ff1d:f5::/32ff1d:f5:ffff:ffff:ffff:ffff:ffff:ffff
247ff1d:f6::/32ff1d:f6:ffff:ffff:ffff:ffff:ffff:ffff
248ff1d:f7::/32ff1d:f7:ffff:ffff:ffff:ffff:ffff:ffff
249ff1d:f8::/32ff1d:f8:ffff:ffff:ffff:ffff:ffff:ffff
250ff1d:f9::/32ff1d:f9:ffff:ffff:ffff:ffff:ffff:ffff
251ff1d:fa::/32ff1d:fa:ffff:ffff:ffff:ffff:ffff:ffff
252ff1d:fb::/32ff1d:fb:ffff:ffff:ffff:ffff:ffff:ffff
253ff1d:fc::/32ff1d:fc:ffff:ffff:ffff:ffff:ffff:ffff
254ff1d:fd::/32ff1d:fd:ffff:ffff:ffff:ffff:ffff:ffff
255ff1d:fe::/32ff1d:fe:ffff:ffff:ffff:ffff:ffff:ffff
256ff1d:ff::/32ff1d: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.