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
fcbf::/16
First address
fcbf::
Last address
fcbf: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
fcbf: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.b.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)

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

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