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

fcaa::/16 makes 256 subnets of /24.

Subnets
#SubnetLast address
1fcaa::/24fcaa:ff:ffff:ffff:ffff:ffff:ffff:ffff
2fcaa:100::/24fcaa:1ff:ffff:ffff:ffff:ffff:ffff:ffff
3fcaa:200::/24fcaa:2ff:ffff:ffff:ffff:ffff:ffff:ffff
4fcaa:300::/24fcaa:3ff:ffff:ffff:ffff:ffff:ffff:ffff
5fcaa:400::/24fcaa:4ff:ffff:ffff:ffff:ffff:ffff:ffff
6fcaa:500::/24fcaa:5ff:ffff:ffff:ffff:ffff:ffff:ffff
7fcaa:600::/24fcaa:6ff:ffff:ffff:ffff:ffff:ffff:ffff
8fcaa:700::/24fcaa:7ff:ffff:ffff:ffff:ffff:ffff:ffff
9fcaa:800::/24fcaa:8ff:ffff:ffff:ffff:ffff:ffff:ffff
10fcaa:900::/24fcaa:9ff:ffff:ffff:ffff:ffff:ffff:ffff
11fcaa:a00::/24fcaa:aff:ffff:ffff:ffff:ffff:ffff:ffff
12fcaa:b00::/24fcaa:bff:ffff:ffff:ffff:ffff:ffff:ffff
13fcaa:c00::/24fcaa:cff:ffff:ffff:ffff:ffff:ffff:ffff
14fcaa:d00::/24fcaa:dff:ffff:ffff:ffff:ffff:ffff:ffff
15fcaa:e00::/24fcaa:eff:ffff:ffff:ffff:ffff:ffff:ffff
16fcaa:f00::/24fcaa:fff:ffff:ffff:ffff:ffff:ffff:ffff
17fcaa:1000::/24fcaa:10ff:ffff:ffff:ffff:ffff:ffff:ffff
18fcaa:1100::/24fcaa:11ff:ffff:ffff:ffff:ffff:ffff:ffff
19fcaa:1200::/24fcaa:12ff:ffff:ffff:ffff:ffff:ffff:ffff
20fcaa:1300::/24fcaa:13ff:ffff:ffff:ffff:ffff:ffff:ffff
21fcaa:1400::/24fcaa:14ff:ffff:ffff:ffff:ffff:ffff:ffff
22fcaa:1500::/24fcaa:15ff:ffff:ffff:ffff:ffff:ffff:ffff
23fcaa:1600::/24fcaa:16ff:ffff:ffff:ffff:ffff:ffff:ffff
24fcaa:1700::/24fcaa:17ff:ffff:ffff:ffff:ffff:ffff:ffff
25fcaa:1800::/24fcaa:18ff:ffff:ffff:ffff:ffff:ffff:ffff
26fcaa:1900::/24fcaa:19ff:ffff:ffff:ffff:ffff:ffff:ffff
27fcaa:1a00::/24fcaa:1aff:ffff:ffff:ffff:ffff:ffff:ffff
28fcaa:1b00::/24fcaa:1bff:ffff:ffff:ffff:ffff:ffff:ffff
29fcaa:1c00::/24fcaa:1cff:ffff:ffff:ffff:ffff:ffff:ffff
30fcaa:1d00::/24fcaa:1dff:ffff:ffff:ffff:ffff:ffff:ffff
31fcaa:1e00::/24fcaa:1eff:ffff:ffff:ffff:ffff:ffff:ffff
32fcaa:1f00::/24fcaa:1fff:ffff:ffff:ffff:ffff:ffff:ffff
33fcaa:2000::/24fcaa:20ff:ffff:ffff:ffff:ffff:ffff:ffff
34fcaa:2100::/24fcaa:21ff:ffff:ffff:ffff:ffff:ffff:ffff
35fcaa:2200::/24fcaa:22ff:ffff:ffff:ffff:ffff:ffff:ffff
36fcaa:2300::/24fcaa:23ff:ffff:ffff:ffff:ffff:ffff:ffff
37fcaa:2400::/24fcaa:24ff:ffff:ffff:ffff:ffff:ffff:ffff
38fcaa:2500::/24fcaa:25ff:ffff:ffff:ffff:ffff:ffff:ffff
39fcaa:2600::/24fcaa:26ff:ffff:ffff:ffff:ffff:ffff:ffff
40fcaa:2700::/24fcaa:27ff:ffff:ffff:ffff:ffff:ffff:ffff
41fcaa:2800::/24fcaa:28ff:ffff:ffff:ffff:ffff:ffff:ffff
42fcaa:2900::/24fcaa:29ff:ffff:ffff:ffff:ffff:ffff:ffff
43fcaa:2a00::/24fcaa:2aff:ffff:ffff:ffff:ffff:ffff:ffff
44fcaa:2b00::/24fcaa:2bff:ffff:ffff:ffff:ffff:ffff:ffff
45fcaa:2c00::/24fcaa:2cff:ffff:ffff:ffff:ffff:ffff:ffff
46fcaa:2d00::/24fcaa:2dff:ffff:ffff:ffff:ffff:ffff:ffff
47fcaa:2e00::/24fcaa:2eff:ffff:ffff:ffff:ffff:ffff:ffff
48fcaa:2f00::/24fcaa:2fff:ffff:ffff:ffff:ffff:ffff:ffff
49fcaa:3000::/24fcaa:30ff:ffff:ffff:ffff:ffff:ffff:ffff
50fcaa:3100::/24fcaa:31ff:ffff:ffff:ffff:ffff:ffff:ffff
51fcaa:3200::/24fcaa:32ff:ffff:ffff:ffff:ffff:ffff:ffff
52fcaa:3300::/24fcaa:33ff:ffff:ffff:ffff:ffff:ffff:ffff
53fcaa:3400::/24fcaa:34ff:ffff:ffff:ffff:ffff:ffff:ffff
54fcaa:3500::/24fcaa:35ff:ffff:ffff:ffff:ffff:ffff:ffff
55fcaa:3600::/24fcaa:36ff:ffff:ffff:ffff:ffff:ffff:ffff
56fcaa:3700::/24fcaa:37ff:ffff:ffff:ffff:ffff:ffff:ffff
57fcaa:3800::/24fcaa:38ff:ffff:ffff:ffff:ffff:ffff:ffff
58fcaa:3900::/24fcaa:39ff:ffff:ffff:ffff:ffff:ffff:ffff
59fcaa:3a00::/24fcaa:3aff:ffff:ffff:ffff:ffff:ffff:ffff
60fcaa:3b00::/24fcaa:3bff:ffff:ffff:ffff:ffff:ffff:ffff
61fcaa:3c00::/24fcaa:3cff:ffff:ffff:ffff:ffff:ffff:ffff
62fcaa:3d00::/24fcaa:3dff:ffff:ffff:ffff:ffff:ffff:ffff
63fcaa:3e00::/24fcaa:3eff:ffff:ffff:ffff:ffff:ffff:ffff
64fcaa:3f00::/24fcaa:3fff:ffff:ffff:ffff:ffff:ffff:ffff
65fcaa:4000::/24fcaa:40ff:ffff:ffff:ffff:ffff:ffff:ffff
66fcaa:4100::/24fcaa:41ff:ffff:ffff:ffff:ffff:ffff:ffff
67fcaa:4200::/24fcaa:42ff:ffff:ffff:ffff:ffff:ffff:ffff
68fcaa:4300::/24fcaa:43ff:ffff:ffff:ffff:ffff:ffff:ffff
69fcaa:4400::/24fcaa:44ff:ffff:ffff:ffff:ffff:ffff:ffff
70fcaa:4500::/24fcaa:45ff:ffff:ffff:ffff:ffff:ffff:ffff
71fcaa:4600::/24fcaa:46ff:ffff:ffff:ffff:ffff:ffff:ffff
72fcaa:4700::/24fcaa:47ff:ffff:ffff:ffff:ffff:ffff:ffff
73fcaa:4800::/24fcaa:48ff:ffff:ffff:ffff:ffff:ffff:ffff
74fcaa:4900::/24fcaa:49ff:ffff:ffff:ffff:ffff:ffff:ffff
75fcaa:4a00::/24fcaa:4aff:ffff:ffff:ffff:ffff:ffff:ffff
76fcaa:4b00::/24fcaa:4bff:ffff:ffff:ffff:ffff:ffff:ffff
77fcaa:4c00::/24fcaa:4cff:ffff:ffff:ffff:ffff:ffff:ffff
78fcaa:4d00::/24fcaa:4dff:ffff:ffff:ffff:ffff:ffff:ffff
79fcaa:4e00::/24fcaa:4eff:ffff:ffff:ffff:ffff:ffff:ffff
80fcaa:4f00::/24fcaa:4fff:ffff:ffff:ffff:ffff:ffff:ffff
81fcaa:5000::/24fcaa:50ff:ffff:ffff:ffff:ffff:ffff:ffff
82fcaa:5100::/24fcaa:51ff:ffff:ffff:ffff:ffff:ffff:ffff
83fcaa:5200::/24fcaa:52ff:ffff:ffff:ffff:ffff:ffff:ffff
84fcaa:5300::/24fcaa:53ff:ffff:ffff:ffff:ffff:ffff:ffff
85fcaa:5400::/24fcaa:54ff:ffff:ffff:ffff:ffff:ffff:ffff
86fcaa:5500::/24fcaa:55ff:ffff:ffff:ffff:ffff:ffff:ffff
87fcaa:5600::/24fcaa:56ff:ffff:ffff:ffff:ffff:ffff:ffff
88fcaa:5700::/24fcaa:57ff:ffff:ffff:ffff:ffff:ffff:ffff
89fcaa:5800::/24fcaa:58ff:ffff:ffff:ffff:ffff:ffff:ffff
90fcaa:5900::/24fcaa:59ff:ffff:ffff:ffff:ffff:ffff:ffff
91fcaa:5a00::/24fcaa:5aff:ffff:ffff:ffff:ffff:ffff:ffff
92fcaa:5b00::/24fcaa:5bff:ffff:ffff:ffff:ffff:ffff:ffff
93fcaa:5c00::/24fcaa:5cff:ffff:ffff:ffff:ffff:ffff:ffff
94fcaa:5d00::/24fcaa:5dff:ffff:ffff:ffff:ffff:ffff:ffff
95fcaa:5e00::/24fcaa:5eff:ffff:ffff:ffff:ffff:ffff:ffff
96fcaa:5f00::/24fcaa:5fff:ffff:ffff:ffff:ffff:ffff:ffff
97fcaa:6000::/24fcaa:60ff:ffff:ffff:ffff:ffff:ffff:ffff
98fcaa:6100::/24fcaa:61ff:ffff:ffff:ffff:ffff:ffff:ffff
99fcaa:6200::/24fcaa:62ff:ffff:ffff:ffff:ffff:ffff:ffff
100fcaa:6300::/24fcaa:63ff:ffff:ffff:ffff:ffff:ffff:ffff
101fcaa:6400::/24fcaa:64ff:ffff:ffff:ffff:ffff:ffff:ffff
102fcaa:6500::/24fcaa:65ff:ffff:ffff:ffff:ffff:ffff:ffff
103fcaa:6600::/24fcaa:66ff:ffff:ffff:ffff:ffff:ffff:ffff
104fcaa:6700::/24fcaa:67ff:ffff:ffff:ffff:ffff:ffff:ffff
105fcaa:6800::/24fcaa:68ff:ffff:ffff:ffff:ffff:ffff:ffff
106fcaa:6900::/24fcaa:69ff:ffff:ffff:ffff:ffff:ffff:ffff
107fcaa:6a00::/24fcaa:6aff:ffff:ffff:ffff:ffff:ffff:ffff
108fcaa:6b00::/24fcaa:6bff:ffff:ffff:ffff:ffff:ffff:ffff
109fcaa:6c00::/24fcaa:6cff:ffff:ffff:ffff:ffff:ffff:ffff
110fcaa:6d00::/24fcaa:6dff:ffff:ffff:ffff:ffff:ffff:ffff
111fcaa:6e00::/24fcaa:6eff:ffff:ffff:ffff:ffff:ffff:ffff
112fcaa:6f00::/24fcaa:6fff:ffff:ffff:ffff:ffff:ffff:ffff
113fcaa:7000::/24fcaa:70ff:ffff:ffff:ffff:ffff:ffff:ffff
114fcaa:7100::/24fcaa:71ff:ffff:ffff:ffff:ffff:ffff:ffff
115fcaa:7200::/24fcaa:72ff:ffff:ffff:ffff:ffff:ffff:ffff
116fcaa:7300::/24fcaa:73ff:ffff:ffff:ffff:ffff:ffff:ffff
117fcaa:7400::/24fcaa:74ff:ffff:ffff:ffff:ffff:ffff:ffff
118fcaa:7500::/24fcaa:75ff:ffff:ffff:ffff:ffff:ffff:ffff
119fcaa:7600::/24fcaa:76ff:ffff:ffff:ffff:ffff:ffff:ffff
120fcaa:7700::/24fcaa:77ff:ffff:ffff:ffff:ffff:ffff:ffff
121fcaa:7800::/24fcaa:78ff:ffff:ffff:ffff:ffff:ffff:ffff
122fcaa:7900::/24fcaa:79ff:ffff:ffff:ffff:ffff:ffff:ffff
123fcaa:7a00::/24fcaa:7aff:ffff:ffff:ffff:ffff:ffff:ffff
124fcaa:7b00::/24fcaa:7bff:ffff:ffff:ffff:ffff:ffff:ffff
125fcaa:7c00::/24fcaa:7cff:ffff:ffff:ffff:ffff:ffff:ffff
126fcaa:7d00::/24fcaa:7dff:ffff:ffff:ffff:ffff:ffff:ffff
127fcaa:7e00::/24fcaa:7eff:ffff:ffff:ffff:ffff:ffff:ffff
128fcaa:7f00::/24fcaa:7fff:ffff:ffff:ffff:ffff:ffff:ffff
129fcaa:8000::/24fcaa:80ff:ffff:ffff:ffff:ffff:ffff:ffff
130fcaa:8100::/24fcaa:81ff:ffff:ffff:ffff:ffff:ffff:ffff
131fcaa:8200::/24fcaa:82ff:ffff:ffff:ffff:ffff:ffff:ffff
132fcaa:8300::/24fcaa:83ff:ffff:ffff:ffff:ffff:ffff:ffff
133fcaa:8400::/24fcaa:84ff:ffff:ffff:ffff:ffff:ffff:ffff
134fcaa:8500::/24fcaa:85ff:ffff:ffff:ffff:ffff:ffff:ffff
135fcaa:8600::/24fcaa:86ff:ffff:ffff:ffff:ffff:ffff:ffff
136fcaa:8700::/24fcaa:87ff:ffff:ffff:ffff:ffff:ffff:ffff
137fcaa:8800::/24fcaa:88ff:ffff:ffff:ffff:ffff:ffff:ffff
138fcaa:8900::/24fcaa:89ff:ffff:ffff:ffff:ffff:ffff:ffff
139fcaa:8a00::/24fcaa:8aff:ffff:ffff:ffff:ffff:ffff:ffff
140fcaa:8b00::/24fcaa:8bff:ffff:ffff:ffff:ffff:ffff:ffff
141fcaa:8c00::/24fcaa:8cff:ffff:ffff:ffff:ffff:ffff:ffff
142fcaa:8d00::/24fcaa:8dff:ffff:ffff:ffff:ffff:ffff:ffff
143fcaa:8e00::/24fcaa:8eff:ffff:ffff:ffff:ffff:ffff:ffff
144fcaa:8f00::/24fcaa:8fff:ffff:ffff:ffff:ffff:ffff:ffff
145fcaa:9000::/24fcaa:90ff:ffff:ffff:ffff:ffff:ffff:ffff
146fcaa:9100::/24fcaa:91ff:ffff:ffff:ffff:ffff:ffff:ffff
147fcaa:9200::/24fcaa:92ff:ffff:ffff:ffff:ffff:ffff:ffff
148fcaa:9300::/24fcaa:93ff:ffff:ffff:ffff:ffff:ffff:ffff
149fcaa:9400::/24fcaa:94ff:ffff:ffff:ffff:ffff:ffff:ffff
150fcaa:9500::/24fcaa:95ff:ffff:ffff:ffff:ffff:ffff:ffff
151fcaa:9600::/24fcaa:96ff:ffff:ffff:ffff:ffff:ffff:ffff
152fcaa:9700::/24fcaa:97ff:ffff:ffff:ffff:ffff:ffff:ffff
153fcaa:9800::/24fcaa:98ff:ffff:ffff:ffff:ffff:ffff:ffff
154fcaa:9900::/24fcaa:99ff:ffff:ffff:ffff:ffff:ffff:ffff
155fcaa:9a00::/24fcaa:9aff:ffff:ffff:ffff:ffff:ffff:ffff
156fcaa:9b00::/24fcaa:9bff:ffff:ffff:ffff:ffff:ffff:ffff
157fcaa:9c00::/24fcaa:9cff:ffff:ffff:ffff:ffff:ffff:ffff
158fcaa:9d00::/24fcaa:9dff:ffff:ffff:ffff:ffff:ffff:ffff
159fcaa:9e00::/24fcaa:9eff:ffff:ffff:ffff:ffff:ffff:ffff
160fcaa:9f00::/24fcaa:9fff:ffff:ffff:ffff:ffff:ffff:ffff
161fcaa:a000::/24fcaa:a0ff:ffff:ffff:ffff:ffff:ffff:ffff
162fcaa:a100::/24fcaa:a1ff:ffff:ffff:ffff:ffff:ffff:ffff
163fcaa:a200::/24fcaa:a2ff:ffff:ffff:ffff:ffff:ffff:ffff
164fcaa:a300::/24fcaa:a3ff:ffff:ffff:ffff:ffff:ffff:ffff
165fcaa:a400::/24fcaa:a4ff:ffff:ffff:ffff:ffff:ffff:ffff
166fcaa:a500::/24fcaa:a5ff:ffff:ffff:ffff:ffff:ffff:ffff
167fcaa:a600::/24fcaa:a6ff:ffff:ffff:ffff:ffff:ffff:ffff
168fcaa:a700::/24fcaa:a7ff:ffff:ffff:ffff:ffff:ffff:ffff
169fcaa:a800::/24fcaa:a8ff:ffff:ffff:ffff:ffff:ffff:ffff
170fcaa:a900::/24fcaa:a9ff:ffff:ffff:ffff:ffff:ffff:ffff
171fcaa:aa00::/24fcaa:aaff:ffff:ffff:ffff:ffff:ffff:ffff
172fcaa:ab00::/24fcaa:abff:ffff:ffff:ffff:ffff:ffff:ffff
173fcaa:ac00::/24fcaa:acff:ffff:ffff:ffff:ffff:ffff:ffff
174fcaa:ad00::/24fcaa:adff:ffff:ffff:ffff:ffff:ffff:ffff
175fcaa:ae00::/24fcaa:aeff:ffff:ffff:ffff:ffff:ffff:ffff
176fcaa:af00::/24fcaa:afff:ffff:ffff:ffff:ffff:ffff:ffff
177fcaa:b000::/24fcaa:b0ff:ffff:ffff:ffff:ffff:ffff:ffff
178fcaa:b100::/24fcaa:b1ff:ffff:ffff:ffff:ffff:ffff:ffff
179fcaa:b200::/24fcaa:b2ff:ffff:ffff:ffff:ffff:ffff:ffff
180fcaa:b300::/24fcaa:b3ff:ffff:ffff:ffff:ffff:ffff:ffff
181fcaa:b400::/24fcaa:b4ff:ffff:ffff:ffff:ffff:ffff:ffff
182fcaa:b500::/24fcaa:b5ff:ffff:ffff:ffff:ffff:ffff:ffff
183fcaa:b600::/24fcaa:b6ff:ffff:ffff:ffff:ffff:ffff:ffff
184fcaa:b700::/24fcaa:b7ff:ffff:ffff:ffff:ffff:ffff:ffff
185fcaa:b800::/24fcaa:b8ff:ffff:ffff:ffff:ffff:ffff:ffff
186fcaa:b900::/24fcaa:b9ff:ffff:ffff:ffff:ffff:ffff:ffff
187fcaa:ba00::/24fcaa:baff:ffff:ffff:ffff:ffff:ffff:ffff
188fcaa:bb00::/24fcaa:bbff:ffff:ffff:ffff:ffff:ffff:ffff
189fcaa:bc00::/24fcaa:bcff:ffff:ffff:ffff:ffff:ffff:ffff
190fcaa:bd00::/24fcaa:bdff:ffff:ffff:ffff:ffff:ffff:ffff
191fcaa:be00::/24fcaa:beff:ffff:ffff:ffff:ffff:ffff:ffff
192fcaa:bf00::/24fcaa:bfff:ffff:ffff:ffff:ffff:ffff:ffff
193fcaa:c000::/24fcaa:c0ff:ffff:ffff:ffff:ffff:ffff:ffff
194fcaa:c100::/24fcaa:c1ff:ffff:ffff:ffff:ffff:ffff:ffff
195fcaa:c200::/24fcaa:c2ff:ffff:ffff:ffff:ffff:ffff:ffff
196fcaa:c300::/24fcaa:c3ff:ffff:ffff:ffff:ffff:ffff:ffff
197fcaa:c400::/24fcaa:c4ff:ffff:ffff:ffff:ffff:ffff:ffff
198fcaa:c500::/24fcaa:c5ff:ffff:ffff:ffff:ffff:ffff:ffff
199fcaa:c600::/24fcaa:c6ff:ffff:ffff:ffff:ffff:ffff:ffff
200fcaa:c700::/24fcaa:c7ff:ffff:ffff:ffff:ffff:ffff:ffff
201fcaa:c800::/24fcaa:c8ff:ffff:ffff:ffff:ffff:ffff:ffff
202fcaa:c900::/24fcaa:c9ff:ffff:ffff:ffff:ffff:ffff:ffff
203fcaa:ca00::/24fcaa:caff:ffff:ffff:ffff:ffff:ffff:ffff
204fcaa:cb00::/24fcaa:cbff:ffff:ffff:ffff:ffff:ffff:ffff
205fcaa:cc00::/24fcaa:ccff:ffff:ffff:ffff:ffff:ffff:ffff
206fcaa:cd00::/24fcaa:cdff:ffff:ffff:ffff:ffff:ffff:ffff
207fcaa:ce00::/24fcaa:ceff:ffff:ffff:ffff:ffff:ffff:ffff
208fcaa:cf00::/24fcaa:cfff:ffff:ffff:ffff:ffff:ffff:ffff
209fcaa:d000::/24fcaa:d0ff:ffff:ffff:ffff:ffff:ffff:ffff
210fcaa:d100::/24fcaa:d1ff:ffff:ffff:ffff:ffff:ffff:ffff
211fcaa:d200::/24fcaa:d2ff:ffff:ffff:ffff:ffff:ffff:ffff
212fcaa:d300::/24fcaa:d3ff:ffff:ffff:ffff:ffff:ffff:ffff
213fcaa:d400::/24fcaa:d4ff:ffff:ffff:ffff:ffff:ffff:ffff
214fcaa:d500::/24fcaa:d5ff:ffff:ffff:ffff:ffff:ffff:ffff
215fcaa:d600::/24fcaa:d6ff:ffff:ffff:ffff:ffff:ffff:ffff
216fcaa:d700::/24fcaa:d7ff:ffff:ffff:ffff:ffff:ffff:ffff
217fcaa:d800::/24fcaa:d8ff:ffff:ffff:ffff:ffff:ffff:ffff
218fcaa:d900::/24fcaa:d9ff:ffff:ffff:ffff:ffff:ffff:ffff
219fcaa:da00::/24fcaa:daff:ffff:ffff:ffff:ffff:ffff:ffff
220fcaa:db00::/24fcaa:dbff:ffff:ffff:ffff:ffff:ffff:ffff
221fcaa:dc00::/24fcaa:dcff:ffff:ffff:ffff:ffff:ffff:ffff
222fcaa:dd00::/24fcaa:ddff:ffff:ffff:ffff:ffff:ffff:ffff
223fcaa:de00::/24fcaa:deff:ffff:ffff:ffff:ffff:ffff:ffff
224fcaa:df00::/24fcaa:dfff:ffff:ffff:ffff:ffff:ffff:ffff
225fcaa:e000::/24fcaa:e0ff:ffff:ffff:ffff:ffff:ffff:ffff
226fcaa:e100::/24fcaa:e1ff:ffff:ffff:ffff:ffff:ffff:ffff
227fcaa:e200::/24fcaa:e2ff:ffff:ffff:ffff:ffff:ffff:ffff
228fcaa:e300::/24fcaa:e3ff:ffff:ffff:ffff:ffff:ffff:ffff
229fcaa:e400::/24fcaa:e4ff:ffff:ffff:ffff:ffff:ffff:ffff
230fcaa:e500::/24fcaa:e5ff:ffff:ffff:ffff:ffff:ffff:ffff
231fcaa:e600::/24fcaa:e6ff:ffff:ffff:ffff:ffff:ffff:ffff
232fcaa:e700::/24fcaa:e7ff:ffff:ffff:ffff:ffff:ffff:ffff
233fcaa:e800::/24fcaa:e8ff:ffff:ffff:ffff:ffff:ffff:ffff
234fcaa:e900::/24fcaa:e9ff:ffff:ffff:ffff:ffff:ffff:ffff
235fcaa:ea00::/24fcaa:eaff:ffff:ffff:ffff:ffff:ffff:ffff
236fcaa:eb00::/24fcaa:ebff:ffff:ffff:ffff:ffff:ffff:ffff
237fcaa:ec00::/24fcaa:ecff:ffff:ffff:ffff:ffff:ffff:ffff
238fcaa:ed00::/24fcaa:edff:ffff:ffff:ffff:ffff:ffff:ffff
239fcaa:ee00::/24fcaa:eeff:ffff:ffff:ffff:ffff:ffff:ffff
240fcaa:ef00::/24fcaa:efff:ffff:ffff:ffff:ffff:ffff:ffff
241fcaa:f000::/24fcaa:f0ff:ffff:ffff:ffff:ffff:ffff:ffff
242fcaa:f100::/24fcaa:f1ff:ffff:ffff:ffff:ffff:ffff:ffff
243fcaa:f200::/24fcaa:f2ff:ffff:ffff:ffff:ffff:ffff:ffff
244fcaa:f300::/24fcaa:f3ff:ffff:ffff:ffff:ffff:ffff:ffff
245fcaa:f400::/24fcaa:f4ff:ffff:ffff:ffff:ffff:ffff:ffff
246fcaa:f500::/24fcaa:f5ff:ffff:ffff:ffff:ffff:ffff:ffff
247fcaa:f600::/24fcaa:f6ff:ffff:ffff:ffff:ffff:ffff:ffff
248fcaa:f700::/24fcaa:f7ff:ffff:ffff:ffff:ffff:ffff:ffff
249fcaa:f800::/24fcaa:f8ff:ffff:ffff:ffff:ffff:ffff:ffff
250fcaa:f900::/24fcaa:f9ff:ffff:ffff:ffff:ffff:ffff:ffff
251fcaa:fa00::/24fcaa:faff:ffff:ffff:ffff:ffff:ffff:ffff
252fcaa:fb00::/24fcaa:fbff:ffff:ffff:ffff:ffff:ffff:ffff
253fcaa:fc00::/24fcaa:fcff:ffff:ffff:ffff:ffff:ffff:ffff
254fcaa:fd00::/24fcaa:fdff:ffff:ffff:ffff:ffff:ffff:ffff
255fcaa:fe00::/24fcaa:feff:ffff:ffff:ffff:ffff:ffff:ffff
256fcaa:ff00::/24fcaa:ffff: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.