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/18
Addresses2^110
/64 networks2^46
Network
fcdd::/18
First address
fcdd::
Last address
fcdd:3fff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
1,298,074,214,633,706,907,132,624,082,305,024 (2^110)
/64 networks (LANs)
70,368,744,177,664 (2^46)
Full form
fcdd:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zones
0.d.d.c.f.ip6.arpa
1.d.d.c.f.ip6.arpa
2.d.d.c.f.ip6.arpa
3.d.d.c.f.ip6.arpa
/18 is not on a 4-bit boundary, so it takes 4 /20 zones.
Split into smaller subnets/32
/19 (2)/20 (4)/21 (8)/22 (16)/24 (64)/28 (1,024)/32 (16,384)

fcdd::/18 makes 16,384 subnets of /32; the first 256 are listed.

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