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
fca1::/16
First address
fca1::
Last address
fca1: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
fca1:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zone
1.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)

fca1::/16 makes 256 subnets of /24.

Subnets
#SubnetLast address
1fca1::/24fca1:ff:ffff:ffff:ffff:ffff:ffff:ffff
2fca1:100::/24fca1:1ff:ffff:ffff:ffff:ffff:ffff:ffff
3fca1:200::/24fca1:2ff:ffff:ffff:ffff:ffff:ffff:ffff
4fca1:300::/24fca1:3ff:ffff:ffff:ffff:ffff:ffff:ffff
5fca1:400::/24fca1:4ff:ffff:ffff:ffff:ffff:ffff:ffff
6fca1:500::/24fca1:5ff:ffff:ffff:ffff:ffff:ffff:ffff
7fca1:600::/24fca1:6ff:ffff:ffff:ffff:ffff:ffff:ffff
8fca1:700::/24fca1:7ff:ffff:ffff:ffff:ffff:ffff:ffff
9fca1:800::/24fca1:8ff:ffff:ffff:ffff:ffff:ffff:ffff
10fca1:900::/24fca1:9ff:ffff:ffff:ffff:ffff:ffff:ffff
11fca1:a00::/24fca1:aff:ffff:ffff:ffff:ffff:ffff:ffff
12fca1:b00::/24fca1:bff:ffff:ffff:ffff:ffff:ffff:ffff
13fca1:c00::/24fca1:cff:ffff:ffff:ffff:ffff:ffff:ffff
14fca1:d00::/24fca1:dff:ffff:ffff:ffff:ffff:ffff:ffff
15fca1:e00::/24fca1:eff:ffff:ffff:ffff:ffff:ffff:ffff
16fca1:f00::/24fca1:fff:ffff:ffff:ffff:ffff:ffff:ffff
17fca1:1000::/24fca1:10ff:ffff:ffff:ffff:ffff:ffff:ffff
18fca1:1100::/24fca1:11ff:ffff:ffff:ffff:ffff:ffff:ffff
19fca1:1200::/24fca1:12ff:ffff:ffff:ffff:ffff:ffff:ffff
20fca1:1300::/24fca1:13ff:ffff:ffff:ffff:ffff:ffff:ffff
21fca1:1400::/24fca1:14ff:ffff:ffff:ffff:ffff:ffff:ffff
22fca1:1500::/24fca1:15ff:ffff:ffff:ffff:ffff:ffff:ffff
23fca1:1600::/24fca1:16ff:ffff:ffff:ffff:ffff:ffff:ffff
24fca1:1700::/24fca1:17ff:ffff:ffff:ffff:ffff:ffff:ffff
25fca1:1800::/24fca1:18ff:ffff:ffff:ffff:ffff:ffff:ffff
26fca1:1900::/24fca1:19ff:ffff:ffff:ffff:ffff:ffff:ffff
27fca1:1a00::/24fca1:1aff:ffff:ffff:ffff:ffff:ffff:ffff
28fca1:1b00::/24fca1:1bff:ffff:ffff:ffff:ffff:ffff:ffff
29fca1:1c00::/24fca1:1cff:ffff:ffff:ffff:ffff:ffff:ffff
30fca1:1d00::/24fca1:1dff:ffff:ffff:ffff:ffff:ffff:ffff
31fca1:1e00::/24fca1:1eff:ffff:ffff:ffff:ffff:ffff:ffff
32fca1:1f00::/24fca1:1fff:ffff:ffff:ffff:ffff:ffff:ffff
33fca1:2000::/24fca1:20ff:ffff:ffff:ffff:ffff:ffff:ffff
34fca1:2100::/24fca1:21ff:ffff:ffff:ffff:ffff:ffff:ffff
35fca1:2200::/24fca1:22ff:ffff:ffff:ffff:ffff:ffff:ffff
36fca1:2300::/24fca1:23ff:ffff:ffff:ffff:ffff:ffff:ffff
37fca1:2400::/24fca1:24ff:ffff:ffff:ffff:ffff:ffff:ffff
38fca1:2500::/24fca1:25ff:ffff:ffff:ffff:ffff:ffff:ffff
39fca1:2600::/24fca1:26ff:ffff:ffff:ffff:ffff:ffff:ffff
40fca1:2700::/24fca1:27ff:ffff:ffff:ffff:ffff:ffff:ffff
41fca1:2800::/24fca1:28ff:ffff:ffff:ffff:ffff:ffff:ffff
42fca1:2900::/24fca1:29ff:ffff:ffff:ffff:ffff:ffff:ffff
43fca1:2a00::/24fca1:2aff:ffff:ffff:ffff:ffff:ffff:ffff
44fca1:2b00::/24fca1:2bff:ffff:ffff:ffff:ffff:ffff:ffff
45fca1:2c00::/24fca1:2cff:ffff:ffff:ffff:ffff:ffff:ffff
46fca1:2d00::/24fca1:2dff:ffff:ffff:ffff:ffff:ffff:ffff
47fca1:2e00::/24fca1:2eff:ffff:ffff:ffff:ffff:ffff:ffff
48fca1:2f00::/24fca1:2fff:ffff:ffff:ffff:ffff:ffff:ffff
49fca1:3000::/24fca1:30ff:ffff:ffff:ffff:ffff:ffff:ffff
50fca1:3100::/24fca1:31ff:ffff:ffff:ffff:ffff:ffff:ffff
51fca1:3200::/24fca1:32ff:ffff:ffff:ffff:ffff:ffff:ffff
52fca1:3300::/24fca1:33ff:ffff:ffff:ffff:ffff:ffff:ffff
53fca1:3400::/24fca1:34ff:ffff:ffff:ffff:ffff:ffff:ffff
54fca1:3500::/24fca1:35ff:ffff:ffff:ffff:ffff:ffff:ffff
55fca1:3600::/24fca1:36ff:ffff:ffff:ffff:ffff:ffff:ffff
56fca1:3700::/24fca1:37ff:ffff:ffff:ffff:ffff:ffff:ffff
57fca1:3800::/24fca1:38ff:ffff:ffff:ffff:ffff:ffff:ffff
58fca1:3900::/24fca1:39ff:ffff:ffff:ffff:ffff:ffff:ffff
59fca1:3a00::/24fca1:3aff:ffff:ffff:ffff:ffff:ffff:ffff
60fca1:3b00::/24fca1:3bff:ffff:ffff:ffff:ffff:ffff:ffff
61fca1:3c00::/24fca1:3cff:ffff:ffff:ffff:ffff:ffff:ffff
62fca1:3d00::/24fca1:3dff:ffff:ffff:ffff:ffff:ffff:ffff
63fca1:3e00::/24fca1:3eff:ffff:ffff:ffff:ffff:ffff:ffff
64fca1:3f00::/24fca1:3fff:ffff:ffff:ffff:ffff:ffff:ffff
65fca1:4000::/24fca1:40ff:ffff:ffff:ffff:ffff:ffff:ffff
66fca1:4100::/24fca1:41ff:ffff:ffff:ffff:ffff:ffff:ffff
67fca1:4200::/24fca1:42ff:ffff:ffff:ffff:ffff:ffff:ffff
68fca1:4300::/24fca1:43ff:ffff:ffff:ffff:ffff:ffff:ffff
69fca1:4400::/24fca1:44ff:ffff:ffff:ffff:ffff:ffff:ffff
70fca1:4500::/24fca1:45ff:ffff:ffff:ffff:ffff:ffff:ffff
71fca1:4600::/24fca1:46ff:ffff:ffff:ffff:ffff:ffff:ffff
72fca1:4700::/24fca1:47ff:ffff:ffff:ffff:ffff:ffff:ffff
73fca1:4800::/24fca1:48ff:ffff:ffff:ffff:ffff:ffff:ffff
74fca1:4900::/24fca1:49ff:ffff:ffff:ffff:ffff:ffff:ffff
75fca1:4a00::/24fca1:4aff:ffff:ffff:ffff:ffff:ffff:ffff
76fca1:4b00::/24fca1:4bff:ffff:ffff:ffff:ffff:ffff:ffff
77fca1:4c00::/24fca1:4cff:ffff:ffff:ffff:ffff:ffff:ffff
78fca1:4d00::/24fca1:4dff:ffff:ffff:ffff:ffff:ffff:ffff
79fca1:4e00::/24fca1:4eff:ffff:ffff:ffff:ffff:ffff:ffff
80fca1:4f00::/24fca1:4fff:ffff:ffff:ffff:ffff:ffff:ffff
81fca1:5000::/24fca1:50ff:ffff:ffff:ffff:ffff:ffff:ffff
82fca1:5100::/24fca1:51ff:ffff:ffff:ffff:ffff:ffff:ffff
83fca1:5200::/24fca1:52ff:ffff:ffff:ffff:ffff:ffff:ffff
84fca1:5300::/24fca1:53ff:ffff:ffff:ffff:ffff:ffff:ffff
85fca1:5400::/24fca1:54ff:ffff:ffff:ffff:ffff:ffff:ffff
86fca1:5500::/24fca1:55ff:ffff:ffff:ffff:ffff:ffff:ffff
87fca1:5600::/24fca1:56ff:ffff:ffff:ffff:ffff:ffff:ffff
88fca1:5700::/24fca1:57ff:ffff:ffff:ffff:ffff:ffff:ffff
89fca1:5800::/24fca1:58ff:ffff:ffff:ffff:ffff:ffff:ffff
90fca1:5900::/24fca1:59ff:ffff:ffff:ffff:ffff:ffff:ffff
91fca1:5a00::/24fca1:5aff:ffff:ffff:ffff:ffff:ffff:ffff
92fca1:5b00::/24fca1:5bff:ffff:ffff:ffff:ffff:ffff:ffff
93fca1:5c00::/24fca1:5cff:ffff:ffff:ffff:ffff:ffff:ffff
94fca1:5d00::/24fca1:5dff:ffff:ffff:ffff:ffff:ffff:ffff
95fca1:5e00::/24fca1:5eff:ffff:ffff:ffff:ffff:ffff:ffff
96fca1:5f00::/24fca1:5fff:ffff:ffff:ffff:ffff:ffff:ffff
97fca1:6000::/24fca1:60ff:ffff:ffff:ffff:ffff:ffff:ffff
98fca1:6100::/24fca1:61ff:ffff:ffff:ffff:ffff:ffff:ffff
99fca1:6200::/24fca1:62ff:ffff:ffff:ffff:ffff:ffff:ffff
100fca1:6300::/24fca1:63ff:ffff:ffff:ffff:ffff:ffff:ffff
101fca1:6400::/24fca1:64ff:ffff:ffff:ffff:ffff:ffff:ffff
102fca1:6500::/24fca1:65ff:ffff:ffff:ffff:ffff:ffff:ffff
103fca1:6600::/24fca1:66ff:ffff:ffff:ffff:ffff:ffff:ffff
104fca1:6700::/24fca1:67ff:ffff:ffff:ffff:ffff:ffff:ffff
105fca1:6800::/24fca1:68ff:ffff:ffff:ffff:ffff:ffff:ffff
106fca1:6900::/24fca1:69ff:ffff:ffff:ffff:ffff:ffff:ffff
107fca1:6a00::/24fca1:6aff:ffff:ffff:ffff:ffff:ffff:ffff
108fca1:6b00::/24fca1:6bff:ffff:ffff:ffff:ffff:ffff:ffff
109fca1:6c00::/24fca1:6cff:ffff:ffff:ffff:ffff:ffff:ffff
110fca1:6d00::/24fca1:6dff:ffff:ffff:ffff:ffff:ffff:ffff
111fca1:6e00::/24fca1:6eff:ffff:ffff:ffff:ffff:ffff:ffff
112fca1:6f00::/24fca1:6fff:ffff:ffff:ffff:ffff:ffff:ffff
113fca1:7000::/24fca1:70ff:ffff:ffff:ffff:ffff:ffff:ffff
114fca1:7100::/24fca1:71ff:ffff:ffff:ffff:ffff:ffff:ffff
115fca1:7200::/24fca1:72ff:ffff:ffff:ffff:ffff:ffff:ffff
116fca1:7300::/24fca1:73ff:ffff:ffff:ffff:ffff:ffff:ffff
117fca1:7400::/24fca1:74ff:ffff:ffff:ffff:ffff:ffff:ffff
118fca1:7500::/24fca1:75ff:ffff:ffff:ffff:ffff:ffff:ffff
119fca1:7600::/24fca1:76ff:ffff:ffff:ffff:ffff:ffff:ffff
120fca1:7700::/24fca1:77ff:ffff:ffff:ffff:ffff:ffff:ffff
121fca1:7800::/24fca1:78ff:ffff:ffff:ffff:ffff:ffff:ffff
122fca1:7900::/24fca1:79ff:ffff:ffff:ffff:ffff:ffff:ffff
123fca1:7a00::/24fca1:7aff:ffff:ffff:ffff:ffff:ffff:ffff
124fca1:7b00::/24fca1:7bff:ffff:ffff:ffff:ffff:ffff:ffff
125fca1:7c00::/24fca1:7cff:ffff:ffff:ffff:ffff:ffff:ffff
126fca1:7d00::/24fca1:7dff:ffff:ffff:ffff:ffff:ffff:ffff
127fca1:7e00::/24fca1:7eff:ffff:ffff:ffff:ffff:ffff:ffff
128fca1:7f00::/24fca1:7fff:ffff:ffff:ffff:ffff:ffff:ffff
129fca1:8000::/24fca1:80ff:ffff:ffff:ffff:ffff:ffff:ffff
130fca1:8100::/24fca1:81ff:ffff:ffff:ffff:ffff:ffff:ffff
131fca1:8200::/24fca1:82ff:ffff:ffff:ffff:ffff:ffff:ffff
132fca1:8300::/24fca1:83ff:ffff:ffff:ffff:ffff:ffff:ffff
133fca1:8400::/24fca1:84ff:ffff:ffff:ffff:ffff:ffff:ffff
134fca1:8500::/24fca1:85ff:ffff:ffff:ffff:ffff:ffff:ffff
135fca1:8600::/24fca1:86ff:ffff:ffff:ffff:ffff:ffff:ffff
136fca1:8700::/24fca1:87ff:ffff:ffff:ffff:ffff:ffff:ffff
137fca1:8800::/24fca1:88ff:ffff:ffff:ffff:ffff:ffff:ffff
138fca1:8900::/24fca1:89ff:ffff:ffff:ffff:ffff:ffff:ffff
139fca1:8a00::/24fca1:8aff:ffff:ffff:ffff:ffff:ffff:ffff
140fca1:8b00::/24fca1:8bff:ffff:ffff:ffff:ffff:ffff:ffff
141fca1:8c00::/24fca1:8cff:ffff:ffff:ffff:ffff:ffff:ffff
142fca1:8d00::/24fca1:8dff:ffff:ffff:ffff:ffff:ffff:ffff
143fca1:8e00::/24fca1:8eff:ffff:ffff:ffff:ffff:ffff:ffff
144fca1:8f00::/24fca1:8fff:ffff:ffff:ffff:ffff:ffff:ffff
145fca1:9000::/24fca1:90ff:ffff:ffff:ffff:ffff:ffff:ffff
146fca1:9100::/24fca1:91ff:ffff:ffff:ffff:ffff:ffff:ffff
147fca1:9200::/24fca1:92ff:ffff:ffff:ffff:ffff:ffff:ffff
148fca1:9300::/24fca1:93ff:ffff:ffff:ffff:ffff:ffff:ffff
149fca1:9400::/24fca1:94ff:ffff:ffff:ffff:ffff:ffff:ffff
150fca1:9500::/24fca1:95ff:ffff:ffff:ffff:ffff:ffff:ffff
151fca1:9600::/24fca1:96ff:ffff:ffff:ffff:ffff:ffff:ffff
152fca1:9700::/24fca1:97ff:ffff:ffff:ffff:ffff:ffff:ffff
153fca1:9800::/24fca1:98ff:ffff:ffff:ffff:ffff:ffff:ffff
154fca1:9900::/24fca1:99ff:ffff:ffff:ffff:ffff:ffff:ffff
155fca1:9a00::/24fca1:9aff:ffff:ffff:ffff:ffff:ffff:ffff
156fca1:9b00::/24fca1:9bff:ffff:ffff:ffff:ffff:ffff:ffff
157fca1:9c00::/24fca1:9cff:ffff:ffff:ffff:ffff:ffff:ffff
158fca1:9d00::/24fca1:9dff:ffff:ffff:ffff:ffff:ffff:ffff
159fca1:9e00::/24fca1:9eff:ffff:ffff:ffff:ffff:ffff:ffff
160fca1:9f00::/24fca1:9fff:ffff:ffff:ffff:ffff:ffff:ffff
161fca1:a000::/24fca1:a0ff:ffff:ffff:ffff:ffff:ffff:ffff
162fca1:a100::/24fca1:a1ff:ffff:ffff:ffff:ffff:ffff:ffff
163fca1:a200::/24fca1:a2ff:ffff:ffff:ffff:ffff:ffff:ffff
164fca1:a300::/24fca1:a3ff:ffff:ffff:ffff:ffff:ffff:ffff
165fca1:a400::/24fca1:a4ff:ffff:ffff:ffff:ffff:ffff:ffff
166fca1:a500::/24fca1:a5ff:ffff:ffff:ffff:ffff:ffff:ffff
167fca1:a600::/24fca1:a6ff:ffff:ffff:ffff:ffff:ffff:ffff
168fca1:a700::/24fca1:a7ff:ffff:ffff:ffff:ffff:ffff:ffff
169fca1:a800::/24fca1:a8ff:ffff:ffff:ffff:ffff:ffff:ffff
170fca1:a900::/24fca1:a9ff:ffff:ffff:ffff:ffff:ffff:ffff
171fca1:aa00::/24fca1:aaff:ffff:ffff:ffff:ffff:ffff:ffff
172fca1:ab00::/24fca1:abff:ffff:ffff:ffff:ffff:ffff:ffff
173fca1:ac00::/24fca1:acff:ffff:ffff:ffff:ffff:ffff:ffff
174fca1:ad00::/24fca1:adff:ffff:ffff:ffff:ffff:ffff:ffff
175fca1:ae00::/24fca1:aeff:ffff:ffff:ffff:ffff:ffff:ffff
176fca1:af00::/24fca1:afff:ffff:ffff:ffff:ffff:ffff:ffff
177fca1:b000::/24fca1:b0ff:ffff:ffff:ffff:ffff:ffff:ffff
178fca1:b100::/24fca1:b1ff:ffff:ffff:ffff:ffff:ffff:ffff
179fca1:b200::/24fca1:b2ff:ffff:ffff:ffff:ffff:ffff:ffff
180fca1:b300::/24fca1:b3ff:ffff:ffff:ffff:ffff:ffff:ffff
181fca1:b400::/24fca1:b4ff:ffff:ffff:ffff:ffff:ffff:ffff
182fca1:b500::/24fca1:b5ff:ffff:ffff:ffff:ffff:ffff:ffff
183fca1:b600::/24fca1:b6ff:ffff:ffff:ffff:ffff:ffff:ffff
184fca1:b700::/24fca1:b7ff:ffff:ffff:ffff:ffff:ffff:ffff
185fca1:b800::/24fca1:b8ff:ffff:ffff:ffff:ffff:ffff:ffff
186fca1:b900::/24fca1:b9ff:ffff:ffff:ffff:ffff:ffff:ffff
187fca1:ba00::/24fca1:baff:ffff:ffff:ffff:ffff:ffff:ffff
188fca1:bb00::/24fca1:bbff:ffff:ffff:ffff:ffff:ffff:ffff
189fca1:bc00::/24fca1:bcff:ffff:ffff:ffff:ffff:ffff:ffff
190fca1:bd00::/24fca1:bdff:ffff:ffff:ffff:ffff:ffff:ffff
191fca1:be00::/24fca1:beff:ffff:ffff:ffff:ffff:ffff:ffff
192fca1:bf00::/24fca1:bfff:ffff:ffff:ffff:ffff:ffff:ffff
193fca1:c000::/24fca1:c0ff:ffff:ffff:ffff:ffff:ffff:ffff
194fca1:c100::/24fca1:c1ff:ffff:ffff:ffff:ffff:ffff:ffff
195fca1:c200::/24fca1:c2ff:ffff:ffff:ffff:ffff:ffff:ffff
196fca1:c300::/24fca1:c3ff:ffff:ffff:ffff:ffff:ffff:ffff
197fca1:c400::/24fca1:c4ff:ffff:ffff:ffff:ffff:ffff:ffff
198fca1:c500::/24fca1:c5ff:ffff:ffff:ffff:ffff:ffff:ffff
199fca1:c600::/24fca1:c6ff:ffff:ffff:ffff:ffff:ffff:ffff
200fca1:c700::/24fca1:c7ff:ffff:ffff:ffff:ffff:ffff:ffff
201fca1:c800::/24fca1:c8ff:ffff:ffff:ffff:ffff:ffff:ffff
202fca1:c900::/24fca1:c9ff:ffff:ffff:ffff:ffff:ffff:ffff
203fca1:ca00::/24fca1:caff:ffff:ffff:ffff:ffff:ffff:ffff
204fca1:cb00::/24fca1:cbff:ffff:ffff:ffff:ffff:ffff:ffff
205fca1:cc00::/24fca1:ccff:ffff:ffff:ffff:ffff:ffff:ffff
206fca1:cd00::/24fca1:cdff:ffff:ffff:ffff:ffff:ffff:ffff
207fca1:ce00::/24fca1:ceff:ffff:ffff:ffff:ffff:ffff:ffff
208fca1:cf00::/24fca1:cfff:ffff:ffff:ffff:ffff:ffff:ffff
209fca1:d000::/24fca1:d0ff:ffff:ffff:ffff:ffff:ffff:ffff
210fca1:d100::/24fca1:d1ff:ffff:ffff:ffff:ffff:ffff:ffff
211fca1:d200::/24fca1:d2ff:ffff:ffff:ffff:ffff:ffff:ffff
212fca1:d300::/24fca1:d3ff:ffff:ffff:ffff:ffff:ffff:ffff
213fca1:d400::/24fca1:d4ff:ffff:ffff:ffff:ffff:ffff:ffff
214fca1:d500::/24fca1:d5ff:ffff:ffff:ffff:ffff:ffff:ffff
215fca1:d600::/24fca1:d6ff:ffff:ffff:ffff:ffff:ffff:ffff
216fca1:d700::/24fca1:d7ff:ffff:ffff:ffff:ffff:ffff:ffff
217fca1:d800::/24fca1:d8ff:ffff:ffff:ffff:ffff:ffff:ffff
218fca1:d900::/24fca1:d9ff:ffff:ffff:ffff:ffff:ffff:ffff
219fca1:da00::/24fca1:daff:ffff:ffff:ffff:ffff:ffff:ffff
220fca1:db00::/24fca1:dbff:ffff:ffff:ffff:ffff:ffff:ffff
221fca1:dc00::/24fca1:dcff:ffff:ffff:ffff:ffff:ffff:ffff
222fca1:dd00::/24fca1:ddff:ffff:ffff:ffff:ffff:ffff:ffff
223fca1:de00::/24fca1:deff:ffff:ffff:ffff:ffff:ffff:ffff
224fca1:df00::/24fca1:dfff:ffff:ffff:ffff:ffff:ffff:ffff
225fca1:e000::/24fca1:e0ff:ffff:ffff:ffff:ffff:ffff:ffff
226fca1:e100::/24fca1:e1ff:ffff:ffff:ffff:ffff:ffff:ffff
227fca1:e200::/24fca1:e2ff:ffff:ffff:ffff:ffff:ffff:ffff
228fca1:e300::/24fca1:e3ff:ffff:ffff:ffff:ffff:ffff:ffff
229fca1:e400::/24fca1:e4ff:ffff:ffff:ffff:ffff:ffff:ffff
230fca1:e500::/24fca1:e5ff:ffff:ffff:ffff:ffff:ffff:ffff
231fca1:e600::/24fca1:e6ff:ffff:ffff:ffff:ffff:ffff:ffff
232fca1:e700::/24fca1:e7ff:ffff:ffff:ffff:ffff:ffff:ffff
233fca1:e800::/24fca1:e8ff:ffff:ffff:ffff:ffff:ffff:ffff
234fca1:e900::/24fca1:e9ff:ffff:ffff:ffff:ffff:ffff:ffff
235fca1:ea00::/24fca1:eaff:ffff:ffff:ffff:ffff:ffff:ffff
236fca1:eb00::/24fca1:ebff:ffff:ffff:ffff:ffff:ffff:ffff
237fca1:ec00::/24fca1:ecff:ffff:ffff:ffff:ffff:ffff:ffff
238fca1:ed00::/24fca1:edff:ffff:ffff:ffff:ffff:ffff:ffff
239fca1:ee00::/24fca1:eeff:ffff:ffff:ffff:ffff:ffff:ffff
240fca1:ef00::/24fca1:efff:ffff:ffff:ffff:ffff:ffff:ffff
241fca1:f000::/24fca1:f0ff:ffff:ffff:ffff:ffff:ffff:ffff
242fca1:f100::/24fca1:f1ff:ffff:ffff:ffff:ffff:ffff:ffff
243fca1:f200::/24fca1:f2ff:ffff:ffff:ffff:ffff:ffff:ffff
244fca1:f300::/24fca1:f3ff:ffff:ffff:ffff:ffff:ffff:ffff
245fca1:f400::/24fca1:f4ff:ffff:ffff:ffff:ffff:ffff:ffff
246fca1:f500::/24fca1:f5ff:ffff:ffff:ffff:ffff:ffff:ffff
247fca1:f600::/24fca1:f6ff:ffff:ffff:ffff:ffff:ffff:ffff
248fca1:f700::/24fca1:f7ff:ffff:ffff:ffff:ffff:ffff:ffff
249fca1:f800::/24fca1:f8ff:ffff:ffff:ffff:ffff:ffff:ffff
250fca1:f900::/24fca1:f9ff:ffff:ffff:ffff:ffff:ffff:ffff
251fca1:fa00::/24fca1:faff:ffff:ffff:ffff:ffff:ffff:ffff
252fca1:fb00::/24fca1:fbff:ffff:ffff:ffff:ffff:ffff:ffff
253fca1:fc00::/24fca1:fcff:ffff:ffff:ffff:ffff:ffff:ffff
254fca1:fd00::/24fca1:fdff:ffff:ffff:ffff:ffff:ffff:ffff
255fca1:fe00::/24fca1:feff:ffff:ffff:ffff:ffff:ffff:ffff
256fca1:ff00::/24fca1: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.