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
fcaf::/16
First address
fcaf::
Last address
fcaf: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
fcaf:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zone
f.a.c.f.ip6.arpa
Split into smaller subnets/32
/17 (2)/18 (4)/19 (8)/20 (16)/24 (256)/28 (4,096)/32 (65,536)

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

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