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
fcb3::/16
First address
fcb3::
Last address
fcb3: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
fcb3:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zone
3.b.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)

fcb3::/16 makes 256 subnets of /24.

Subnets
#SubnetLast address
1fcb3::/24fcb3:ff:ffff:ffff:ffff:ffff:ffff:ffff
2fcb3:100::/24fcb3:1ff:ffff:ffff:ffff:ffff:ffff:ffff
3fcb3:200::/24fcb3:2ff:ffff:ffff:ffff:ffff:ffff:ffff
4fcb3:300::/24fcb3:3ff:ffff:ffff:ffff:ffff:ffff:ffff
5fcb3:400::/24fcb3:4ff:ffff:ffff:ffff:ffff:ffff:ffff
6fcb3:500::/24fcb3:5ff:ffff:ffff:ffff:ffff:ffff:ffff
7fcb3:600::/24fcb3:6ff:ffff:ffff:ffff:ffff:ffff:ffff
8fcb3:700::/24fcb3:7ff:ffff:ffff:ffff:ffff:ffff:ffff
9fcb3:800::/24fcb3:8ff:ffff:ffff:ffff:ffff:ffff:ffff
10fcb3:900::/24fcb3:9ff:ffff:ffff:ffff:ffff:ffff:ffff
11fcb3:a00::/24fcb3:aff:ffff:ffff:ffff:ffff:ffff:ffff
12fcb3:b00::/24fcb3:bff:ffff:ffff:ffff:ffff:ffff:ffff
13fcb3:c00::/24fcb3:cff:ffff:ffff:ffff:ffff:ffff:ffff
14fcb3:d00::/24fcb3:dff:ffff:ffff:ffff:ffff:ffff:ffff
15fcb3:e00::/24fcb3:eff:ffff:ffff:ffff:ffff:ffff:ffff
16fcb3:f00::/24fcb3:fff:ffff:ffff:ffff:ffff:ffff:ffff
17fcb3:1000::/24fcb3:10ff:ffff:ffff:ffff:ffff:ffff:ffff
18fcb3:1100::/24fcb3:11ff:ffff:ffff:ffff:ffff:ffff:ffff
19fcb3:1200::/24fcb3:12ff:ffff:ffff:ffff:ffff:ffff:ffff
20fcb3:1300::/24fcb3:13ff:ffff:ffff:ffff:ffff:ffff:ffff
21fcb3:1400::/24fcb3:14ff:ffff:ffff:ffff:ffff:ffff:ffff
22fcb3:1500::/24fcb3:15ff:ffff:ffff:ffff:ffff:ffff:ffff
23fcb3:1600::/24fcb3:16ff:ffff:ffff:ffff:ffff:ffff:ffff
24fcb3:1700::/24fcb3:17ff:ffff:ffff:ffff:ffff:ffff:ffff
25fcb3:1800::/24fcb3:18ff:ffff:ffff:ffff:ffff:ffff:ffff
26fcb3:1900::/24fcb3:19ff:ffff:ffff:ffff:ffff:ffff:ffff
27fcb3:1a00::/24fcb3:1aff:ffff:ffff:ffff:ffff:ffff:ffff
28fcb3:1b00::/24fcb3:1bff:ffff:ffff:ffff:ffff:ffff:ffff
29fcb3:1c00::/24fcb3:1cff:ffff:ffff:ffff:ffff:ffff:ffff
30fcb3:1d00::/24fcb3:1dff:ffff:ffff:ffff:ffff:ffff:ffff
31fcb3:1e00::/24fcb3:1eff:ffff:ffff:ffff:ffff:ffff:ffff
32fcb3:1f00::/24fcb3:1fff:ffff:ffff:ffff:ffff:ffff:ffff
33fcb3:2000::/24fcb3:20ff:ffff:ffff:ffff:ffff:ffff:ffff
34fcb3:2100::/24fcb3:21ff:ffff:ffff:ffff:ffff:ffff:ffff
35fcb3:2200::/24fcb3:22ff:ffff:ffff:ffff:ffff:ffff:ffff
36fcb3:2300::/24fcb3:23ff:ffff:ffff:ffff:ffff:ffff:ffff
37fcb3:2400::/24fcb3:24ff:ffff:ffff:ffff:ffff:ffff:ffff
38fcb3:2500::/24fcb3:25ff:ffff:ffff:ffff:ffff:ffff:ffff
39fcb3:2600::/24fcb3:26ff:ffff:ffff:ffff:ffff:ffff:ffff
40fcb3:2700::/24fcb3:27ff:ffff:ffff:ffff:ffff:ffff:ffff
41fcb3:2800::/24fcb3:28ff:ffff:ffff:ffff:ffff:ffff:ffff
42fcb3:2900::/24fcb3:29ff:ffff:ffff:ffff:ffff:ffff:ffff
43fcb3:2a00::/24fcb3:2aff:ffff:ffff:ffff:ffff:ffff:ffff
44fcb3:2b00::/24fcb3:2bff:ffff:ffff:ffff:ffff:ffff:ffff
45fcb3:2c00::/24fcb3:2cff:ffff:ffff:ffff:ffff:ffff:ffff
46fcb3:2d00::/24fcb3:2dff:ffff:ffff:ffff:ffff:ffff:ffff
47fcb3:2e00::/24fcb3:2eff:ffff:ffff:ffff:ffff:ffff:ffff
48fcb3:2f00::/24fcb3:2fff:ffff:ffff:ffff:ffff:ffff:ffff
49fcb3:3000::/24fcb3:30ff:ffff:ffff:ffff:ffff:ffff:ffff
50fcb3:3100::/24fcb3:31ff:ffff:ffff:ffff:ffff:ffff:ffff
51fcb3:3200::/24fcb3:32ff:ffff:ffff:ffff:ffff:ffff:ffff
52fcb3:3300::/24fcb3:33ff:ffff:ffff:ffff:ffff:ffff:ffff
53fcb3:3400::/24fcb3:34ff:ffff:ffff:ffff:ffff:ffff:ffff
54fcb3:3500::/24fcb3:35ff:ffff:ffff:ffff:ffff:ffff:ffff
55fcb3:3600::/24fcb3:36ff:ffff:ffff:ffff:ffff:ffff:ffff
56fcb3:3700::/24fcb3:37ff:ffff:ffff:ffff:ffff:ffff:ffff
57fcb3:3800::/24fcb3:38ff:ffff:ffff:ffff:ffff:ffff:ffff
58fcb3:3900::/24fcb3:39ff:ffff:ffff:ffff:ffff:ffff:ffff
59fcb3:3a00::/24fcb3:3aff:ffff:ffff:ffff:ffff:ffff:ffff
60fcb3:3b00::/24fcb3:3bff:ffff:ffff:ffff:ffff:ffff:ffff
61fcb3:3c00::/24fcb3:3cff:ffff:ffff:ffff:ffff:ffff:ffff
62fcb3:3d00::/24fcb3:3dff:ffff:ffff:ffff:ffff:ffff:ffff
63fcb3:3e00::/24fcb3:3eff:ffff:ffff:ffff:ffff:ffff:ffff
64fcb3:3f00::/24fcb3:3fff:ffff:ffff:ffff:ffff:ffff:ffff
65fcb3:4000::/24fcb3:40ff:ffff:ffff:ffff:ffff:ffff:ffff
66fcb3:4100::/24fcb3:41ff:ffff:ffff:ffff:ffff:ffff:ffff
67fcb3:4200::/24fcb3:42ff:ffff:ffff:ffff:ffff:ffff:ffff
68fcb3:4300::/24fcb3:43ff:ffff:ffff:ffff:ffff:ffff:ffff
69fcb3:4400::/24fcb3:44ff:ffff:ffff:ffff:ffff:ffff:ffff
70fcb3:4500::/24fcb3:45ff:ffff:ffff:ffff:ffff:ffff:ffff
71fcb3:4600::/24fcb3:46ff:ffff:ffff:ffff:ffff:ffff:ffff
72fcb3:4700::/24fcb3:47ff:ffff:ffff:ffff:ffff:ffff:ffff
73fcb3:4800::/24fcb3:48ff:ffff:ffff:ffff:ffff:ffff:ffff
74fcb3:4900::/24fcb3:49ff:ffff:ffff:ffff:ffff:ffff:ffff
75fcb3:4a00::/24fcb3:4aff:ffff:ffff:ffff:ffff:ffff:ffff
76fcb3:4b00::/24fcb3:4bff:ffff:ffff:ffff:ffff:ffff:ffff
77fcb3:4c00::/24fcb3:4cff:ffff:ffff:ffff:ffff:ffff:ffff
78fcb3:4d00::/24fcb3:4dff:ffff:ffff:ffff:ffff:ffff:ffff
79fcb3:4e00::/24fcb3:4eff:ffff:ffff:ffff:ffff:ffff:ffff
80fcb3:4f00::/24fcb3:4fff:ffff:ffff:ffff:ffff:ffff:ffff
81fcb3:5000::/24fcb3:50ff:ffff:ffff:ffff:ffff:ffff:ffff
82fcb3:5100::/24fcb3:51ff:ffff:ffff:ffff:ffff:ffff:ffff
83fcb3:5200::/24fcb3:52ff:ffff:ffff:ffff:ffff:ffff:ffff
84fcb3:5300::/24fcb3:53ff:ffff:ffff:ffff:ffff:ffff:ffff
85fcb3:5400::/24fcb3:54ff:ffff:ffff:ffff:ffff:ffff:ffff
86fcb3:5500::/24fcb3:55ff:ffff:ffff:ffff:ffff:ffff:ffff
87fcb3:5600::/24fcb3:56ff:ffff:ffff:ffff:ffff:ffff:ffff
88fcb3:5700::/24fcb3:57ff:ffff:ffff:ffff:ffff:ffff:ffff
89fcb3:5800::/24fcb3:58ff:ffff:ffff:ffff:ffff:ffff:ffff
90fcb3:5900::/24fcb3:59ff:ffff:ffff:ffff:ffff:ffff:ffff
91fcb3:5a00::/24fcb3:5aff:ffff:ffff:ffff:ffff:ffff:ffff
92fcb3:5b00::/24fcb3:5bff:ffff:ffff:ffff:ffff:ffff:ffff
93fcb3:5c00::/24fcb3:5cff:ffff:ffff:ffff:ffff:ffff:ffff
94fcb3:5d00::/24fcb3:5dff:ffff:ffff:ffff:ffff:ffff:ffff
95fcb3:5e00::/24fcb3:5eff:ffff:ffff:ffff:ffff:ffff:ffff
96fcb3:5f00::/24fcb3:5fff:ffff:ffff:ffff:ffff:ffff:ffff
97fcb3:6000::/24fcb3:60ff:ffff:ffff:ffff:ffff:ffff:ffff
98fcb3:6100::/24fcb3:61ff:ffff:ffff:ffff:ffff:ffff:ffff
99fcb3:6200::/24fcb3:62ff:ffff:ffff:ffff:ffff:ffff:ffff
100fcb3:6300::/24fcb3:63ff:ffff:ffff:ffff:ffff:ffff:ffff
101fcb3:6400::/24fcb3:64ff:ffff:ffff:ffff:ffff:ffff:ffff
102fcb3:6500::/24fcb3:65ff:ffff:ffff:ffff:ffff:ffff:ffff
103fcb3:6600::/24fcb3:66ff:ffff:ffff:ffff:ffff:ffff:ffff
104fcb3:6700::/24fcb3:67ff:ffff:ffff:ffff:ffff:ffff:ffff
105fcb3:6800::/24fcb3:68ff:ffff:ffff:ffff:ffff:ffff:ffff
106fcb3:6900::/24fcb3:69ff:ffff:ffff:ffff:ffff:ffff:ffff
107fcb3:6a00::/24fcb3:6aff:ffff:ffff:ffff:ffff:ffff:ffff
108fcb3:6b00::/24fcb3:6bff:ffff:ffff:ffff:ffff:ffff:ffff
109fcb3:6c00::/24fcb3:6cff:ffff:ffff:ffff:ffff:ffff:ffff
110fcb3:6d00::/24fcb3:6dff:ffff:ffff:ffff:ffff:ffff:ffff
111fcb3:6e00::/24fcb3:6eff:ffff:ffff:ffff:ffff:ffff:ffff
112fcb3:6f00::/24fcb3:6fff:ffff:ffff:ffff:ffff:ffff:ffff
113fcb3:7000::/24fcb3:70ff:ffff:ffff:ffff:ffff:ffff:ffff
114fcb3:7100::/24fcb3:71ff:ffff:ffff:ffff:ffff:ffff:ffff
115fcb3:7200::/24fcb3:72ff:ffff:ffff:ffff:ffff:ffff:ffff
116fcb3:7300::/24fcb3:73ff:ffff:ffff:ffff:ffff:ffff:ffff
117fcb3:7400::/24fcb3:74ff:ffff:ffff:ffff:ffff:ffff:ffff
118fcb3:7500::/24fcb3:75ff:ffff:ffff:ffff:ffff:ffff:ffff
119fcb3:7600::/24fcb3:76ff:ffff:ffff:ffff:ffff:ffff:ffff
120fcb3:7700::/24fcb3:77ff:ffff:ffff:ffff:ffff:ffff:ffff
121fcb3:7800::/24fcb3:78ff:ffff:ffff:ffff:ffff:ffff:ffff
122fcb3:7900::/24fcb3:79ff:ffff:ffff:ffff:ffff:ffff:ffff
123fcb3:7a00::/24fcb3:7aff:ffff:ffff:ffff:ffff:ffff:ffff
124fcb3:7b00::/24fcb3:7bff:ffff:ffff:ffff:ffff:ffff:ffff
125fcb3:7c00::/24fcb3:7cff:ffff:ffff:ffff:ffff:ffff:ffff
126fcb3:7d00::/24fcb3:7dff:ffff:ffff:ffff:ffff:ffff:ffff
127fcb3:7e00::/24fcb3:7eff:ffff:ffff:ffff:ffff:ffff:ffff
128fcb3:7f00::/24fcb3:7fff:ffff:ffff:ffff:ffff:ffff:ffff
129fcb3:8000::/24fcb3:80ff:ffff:ffff:ffff:ffff:ffff:ffff
130fcb3:8100::/24fcb3:81ff:ffff:ffff:ffff:ffff:ffff:ffff
131fcb3:8200::/24fcb3:82ff:ffff:ffff:ffff:ffff:ffff:ffff
132fcb3:8300::/24fcb3:83ff:ffff:ffff:ffff:ffff:ffff:ffff
133fcb3:8400::/24fcb3:84ff:ffff:ffff:ffff:ffff:ffff:ffff
134fcb3:8500::/24fcb3:85ff:ffff:ffff:ffff:ffff:ffff:ffff
135fcb3:8600::/24fcb3:86ff:ffff:ffff:ffff:ffff:ffff:ffff
136fcb3:8700::/24fcb3:87ff:ffff:ffff:ffff:ffff:ffff:ffff
137fcb3:8800::/24fcb3:88ff:ffff:ffff:ffff:ffff:ffff:ffff
138fcb3:8900::/24fcb3:89ff:ffff:ffff:ffff:ffff:ffff:ffff
139fcb3:8a00::/24fcb3:8aff:ffff:ffff:ffff:ffff:ffff:ffff
140fcb3:8b00::/24fcb3:8bff:ffff:ffff:ffff:ffff:ffff:ffff
141fcb3:8c00::/24fcb3:8cff:ffff:ffff:ffff:ffff:ffff:ffff
142fcb3:8d00::/24fcb3:8dff:ffff:ffff:ffff:ffff:ffff:ffff
143fcb3:8e00::/24fcb3:8eff:ffff:ffff:ffff:ffff:ffff:ffff
144fcb3:8f00::/24fcb3:8fff:ffff:ffff:ffff:ffff:ffff:ffff
145fcb3:9000::/24fcb3:90ff:ffff:ffff:ffff:ffff:ffff:ffff
146fcb3:9100::/24fcb3:91ff:ffff:ffff:ffff:ffff:ffff:ffff
147fcb3:9200::/24fcb3:92ff:ffff:ffff:ffff:ffff:ffff:ffff
148fcb3:9300::/24fcb3:93ff:ffff:ffff:ffff:ffff:ffff:ffff
149fcb3:9400::/24fcb3:94ff:ffff:ffff:ffff:ffff:ffff:ffff
150fcb3:9500::/24fcb3:95ff:ffff:ffff:ffff:ffff:ffff:ffff
151fcb3:9600::/24fcb3:96ff:ffff:ffff:ffff:ffff:ffff:ffff
152fcb3:9700::/24fcb3:97ff:ffff:ffff:ffff:ffff:ffff:ffff
153fcb3:9800::/24fcb3:98ff:ffff:ffff:ffff:ffff:ffff:ffff
154fcb3:9900::/24fcb3:99ff:ffff:ffff:ffff:ffff:ffff:ffff
155fcb3:9a00::/24fcb3:9aff:ffff:ffff:ffff:ffff:ffff:ffff
156fcb3:9b00::/24fcb3:9bff:ffff:ffff:ffff:ffff:ffff:ffff
157fcb3:9c00::/24fcb3:9cff:ffff:ffff:ffff:ffff:ffff:ffff
158fcb3:9d00::/24fcb3:9dff:ffff:ffff:ffff:ffff:ffff:ffff
159fcb3:9e00::/24fcb3:9eff:ffff:ffff:ffff:ffff:ffff:ffff
160fcb3:9f00::/24fcb3:9fff:ffff:ffff:ffff:ffff:ffff:ffff
161fcb3:a000::/24fcb3:a0ff:ffff:ffff:ffff:ffff:ffff:ffff
162fcb3:a100::/24fcb3:a1ff:ffff:ffff:ffff:ffff:ffff:ffff
163fcb3:a200::/24fcb3:a2ff:ffff:ffff:ffff:ffff:ffff:ffff
164fcb3:a300::/24fcb3:a3ff:ffff:ffff:ffff:ffff:ffff:ffff
165fcb3:a400::/24fcb3:a4ff:ffff:ffff:ffff:ffff:ffff:ffff
166fcb3:a500::/24fcb3:a5ff:ffff:ffff:ffff:ffff:ffff:ffff
167fcb3:a600::/24fcb3:a6ff:ffff:ffff:ffff:ffff:ffff:ffff
168fcb3:a700::/24fcb3:a7ff:ffff:ffff:ffff:ffff:ffff:ffff
169fcb3:a800::/24fcb3:a8ff:ffff:ffff:ffff:ffff:ffff:ffff
170fcb3:a900::/24fcb3:a9ff:ffff:ffff:ffff:ffff:ffff:ffff
171fcb3:aa00::/24fcb3:aaff:ffff:ffff:ffff:ffff:ffff:ffff
172fcb3:ab00::/24fcb3:abff:ffff:ffff:ffff:ffff:ffff:ffff
173fcb3:ac00::/24fcb3:acff:ffff:ffff:ffff:ffff:ffff:ffff
174fcb3:ad00::/24fcb3:adff:ffff:ffff:ffff:ffff:ffff:ffff
175fcb3:ae00::/24fcb3:aeff:ffff:ffff:ffff:ffff:ffff:ffff
176fcb3:af00::/24fcb3:afff:ffff:ffff:ffff:ffff:ffff:ffff
177fcb3:b000::/24fcb3:b0ff:ffff:ffff:ffff:ffff:ffff:ffff
178fcb3:b100::/24fcb3:b1ff:ffff:ffff:ffff:ffff:ffff:ffff
179fcb3:b200::/24fcb3:b2ff:ffff:ffff:ffff:ffff:ffff:ffff
180fcb3:b300::/24fcb3:b3ff:ffff:ffff:ffff:ffff:ffff:ffff
181fcb3:b400::/24fcb3:b4ff:ffff:ffff:ffff:ffff:ffff:ffff
182fcb3:b500::/24fcb3:b5ff:ffff:ffff:ffff:ffff:ffff:ffff
183fcb3:b600::/24fcb3:b6ff:ffff:ffff:ffff:ffff:ffff:ffff
184fcb3:b700::/24fcb3:b7ff:ffff:ffff:ffff:ffff:ffff:ffff
185fcb3:b800::/24fcb3:b8ff:ffff:ffff:ffff:ffff:ffff:ffff
186fcb3:b900::/24fcb3:b9ff:ffff:ffff:ffff:ffff:ffff:ffff
187fcb3:ba00::/24fcb3:baff:ffff:ffff:ffff:ffff:ffff:ffff
188fcb3:bb00::/24fcb3:bbff:ffff:ffff:ffff:ffff:ffff:ffff
189fcb3:bc00::/24fcb3:bcff:ffff:ffff:ffff:ffff:ffff:ffff
190fcb3:bd00::/24fcb3:bdff:ffff:ffff:ffff:ffff:ffff:ffff
191fcb3:be00::/24fcb3:beff:ffff:ffff:ffff:ffff:ffff:ffff
192fcb3:bf00::/24fcb3:bfff:ffff:ffff:ffff:ffff:ffff:ffff
193fcb3:c000::/24fcb3:c0ff:ffff:ffff:ffff:ffff:ffff:ffff
194fcb3:c100::/24fcb3:c1ff:ffff:ffff:ffff:ffff:ffff:ffff
195fcb3:c200::/24fcb3:c2ff:ffff:ffff:ffff:ffff:ffff:ffff
196fcb3:c300::/24fcb3:c3ff:ffff:ffff:ffff:ffff:ffff:ffff
197fcb3:c400::/24fcb3:c4ff:ffff:ffff:ffff:ffff:ffff:ffff
198fcb3:c500::/24fcb3:c5ff:ffff:ffff:ffff:ffff:ffff:ffff
199fcb3:c600::/24fcb3:c6ff:ffff:ffff:ffff:ffff:ffff:ffff
200fcb3:c700::/24fcb3:c7ff:ffff:ffff:ffff:ffff:ffff:ffff
201fcb3:c800::/24fcb3:c8ff:ffff:ffff:ffff:ffff:ffff:ffff
202fcb3:c900::/24fcb3:c9ff:ffff:ffff:ffff:ffff:ffff:ffff
203fcb3:ca00::/24fcb3:caff:ffff:ffff:ffff:ffff:ffff:ffff
204fcb3:cb00::/24fcb3:cbff:ffff:ffff:ffff:ffff:ffff:ffff
205fcb3:cc00::/24fcb3:ccff:ffff:ffff:ffff:ffff:ffff:ffff
206fcb3:cd00::/24fcb3:cdff:ffff:ffff:ffff:ffff:ffff:ffff
207fcb3:ce00::/24fcb3:ceff:ffff:ffff:ffff:ffff:ffff:ffff
208fcb3:cf00::/24fcb3:cfff:ffff:ffff:ffff:ffff:ffff:ffff
209fcb3:d000::/24fcb3:d0ff:ffff:ffff:ffff:ffff:ffff:ffff
210fcb3:d100::/24fcb3:d1ff:ffff:ffff:ffff:ffff:ffff:ffff
211fcb3:d200::/24fcb3:d2ff:ffff:ffff:ffff:ffff:ffff:ffff
212fcb3:d300::/24fcb3:d3ff:ffff:ffff:ffff:ffff:ffff:ffff
213fcb3:d400::/24fcb3:d4ff:ffff:ffff:ffff:ffff:ffff:ffff
214fcb3:d500::/24fcb3:d5ff:ffff:ffff:ffff:ffff:ffff:ffff
215fcb3:d600::/24fcb3:d6ff:ffff:ffff:ffff:ffff:ffff:ffff
216fcb3:d700::/24fcb3:d7ff:ffff:ffff:ffff:ffff:ffff:ffff
217fcb3:d800::/24fcb3:d8ff:ffff:ffff:ffff:ffff:ffff:ffff
218fcb3:d900::/24fcb3:d9ff:ffff:ffff:ffff:ffff:ffff:ffff
219fcb3:da00::/24fcb3:daff:ffff:ffff:ffff:ffff:ffff:ffff
220fcb3:db00::/24fcb3:dbff:ffff:ffff:ffff:ffff:ffff:ffff
221fcb3:dc00::/24fcb3:dcff:ffff:ffff:ffff:ffff:ffff:ffff
222fcb3:dd00::/24fcb3:ddff:ffff:ffff:ffff:ffff:ffff:ffff
223fcb3:de00::/24fcb3:deff:ffff:ffff:ffff:ffff:ffff:ffff
224fcb3:df00::/24fcb3:dfff:ffff:ffff:ffff:ffff:ffff:ffff
225fcb3:e000::/24fcb3:e0ff:ffff:ffff:ffff:ffff:ffff:ffff
226fcb3:e100::/24fcb3:e1ff:ffff:ffff:ffff:ffff:ffff:ffff
227fcb3:e200::/24fcb3:e2ff:ffff:ffff:ffff:ffff:ffff:ffff
228fcb3:e300::/24fcb3:e3ff:ffff:ffff:ffff:ffff:ffff:ffff
229fcb3:e400::/24fcb3:e4ff:ffff:ffff:ffff:ffff:ffff:ffff
230fcb3:e500::/24fcb3:e5ff:ffff:ffff:ffff:ffff:ffff:ffff
231fcb3:e600::/24fcb3:e6ff:ffff:ffff:ffff:ffff:ffff:ffff
232fcb3:e700::/24fcb3:e7ff:ffff:ffff:ffff:ffff:ffff:ffff
233fcb3:e800::/24fcb3:e8ff:ffff:ffff:ffff:ffff:ffff:ffff
234fcb3:e900::/24fcb3:e9ff:ffff:ffff:ffff:ffff:ffff:ffff
235fcb3:ea00::/24fcb3:eaff:ffff:ffff:ffff:ffff:ffff:ffff
236fcb3:eb00::/24fcb3:ebff:ffff:ffff:ffff:ffff:ffff:ffff
237fcb3:ec00::/24fcb3:ecff:ffff:ffff:ffff:ffff:ffff:ffff
238fcb3:ed00::/24fcb3:edff:ffff:ffff:ffff:ffff:ffff:ffff
239fcb3:ee00::/24fcb3:eeff:ffff:ffff:ffff:ffff:ffff:ffff
240fcb3:ef00::/24fcb3:efff:ffff:ffff:ffff:ffff:ffff:ffff
241fcb3:f000::/24fcb3:f0ff:ffff:ffff:ffff:ffff:ffff:ffff
242fcb3:f100::/24fcb3:f1ff:ffff:ffff:ffff:ffff:ffff:ffff
243fcb3:f200::/24fcb3:f2ff:ffff:ffff:ffff:ffff:ffff:ffff
244fcb3:f300::/24fcb3:f3ff:ffff:ffff:ffff:ffff:ffff:ffff
245fcb3:f400::/24fcb3:f4ff:ffff:ffff:ffff:ffff:ffff:ffff
246fcb3:f500::/24fcb3:f5ff:ffff:ffff:ffff:ffff:ffff:ffff
247fcb3:f600::/24fcb3:f6ff:ffff:ffff:ffff:ffff:ffff:ffff
248fcb3:f700::/24fcb3:f7ff:ffff:ffff:ffff:ffff:ffff:ffff
249fcb3:f800::/24fcb3:f8ff:ffff:ffff:ffff:ffff:ffff:ffff
250fcb3:f900::/24fcb3:f9ff:ffff:ffff:ffff:ffff:ffff:ffff
251fcb3:fa00::/24fcb3:faff:ffff:ffff:ffff:ffff:ffff:ffff
252fcb3:fb00::/24fcb3:fbff:ffff:ffff:ffff:ffff:ffff:ffff
253fcb3:fc00::/24fcb3:fcff:ffff:ffff:ffff:ffff:ffff:ffff
254fcb3:fd00::/24fcb3:fdff:ffff:ffff:ffff:ffff:ffff:ffff
255fcb3:fe00::/24fcb3:feff:ffff:ffff:ffff:ffff:ffff:ffff
256fcb3:ff00::/24fcb3: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.