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
fc57::/16
First address
fc57::
Last address
fc57: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
fc57:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zone
7.5.c.f.ip6.arpa
Split into smaller subnets/32
/17 (2)/18 (4)/19 (8)/20 (16)/24 (256)/28 (4,096)/32 (65,536)

fc57::/16 makes 65,536 subnets of /32; the first 256 are listed.

Subnets
#SubnetLast address
1fc57::/32fc57:0:ffff:ffff:ffff:ffff:ffff:ffff
2fc57:1::/32fc57:1:ffff:ffff:ffff:ffff:ffff:ffff
3fc57:2::/32fc57:2:ffff:ffff:ffff:ffff:ffff:ffff
4fc57:3::/32fc57:3:ffff:ffff:ffff:ffff:ffff:ffff
5fc57:4::/32fc57:4:ffff:ffff:ffff:ffff:ffff:ffff
6fc57:5::/32fc57:5:ffff:ffff:ffff:ffff:ffff:ffff
7fc57:6::/32fc57:6:ffff:ffff:ffff:ffff:ffff:ffff
8fc57:7::/32fc57:7:ffff:ffff:ffff:ffff:ffff:ffff
9fc57:8::/32fc57:8:ffff:ffff:ffff:ffff:ffff:ffff
10fc57:9::/32fc57:9:ffff:ffff:ffff:ffff:ffff:ffff
11fc57:a::/32fc57:a:ffff:ffff:ffff:ffff:ffff:ffff
12fc57:b::/32fc57:b:ffff:ffff:ffff:ffff:ffff:ffff
13fc57:c::/32fc57:c:ffff:ffff:ffff:ffff:ffff:ffff
14fc57:d::/32fc57:d:ffff:ffff:ffff:ffff:ffff:ffff
15fc57:e::/32fc57:e:ffff:ffff:ffff:ffff:ffff:ffff
16fc57:f::/32fc57:f:ffff:ffff:ffff:ffff:ffff:ffff
17fc57:10::/32fc57:10:ffff:ffff:ffff:ffff:ffff:ffff
18fc57:11::/32fc57:11:ffff:ffff:ffff:ffff:ffff:ffff
19fc57:12::/32fc57:12:ffff:ffff:ffff:ffff:ffff:ffff
20fc57:13::/32fc57:13:ffff:ffff:ffff:ffff:ffff:ffff
21fc57:14::/32fc57:14:ffff:ffff:ffff:ffff:ffff:ffff
22fc57:15::/32fc57:15:ffff:ffff:ffff:ffff:ffff:ffff
23fc57:16::/32fc57:16:ffff:ffff:ffff:ffff:ffff:ffff
24fc57:17::/32fc57:17:ffff:ffff:ffff:ffff:ffff:ffff
25fc57:18::/32fc57:18:ffff:ffff:ffff:ffff:ffff:ffff
26fc57:19::/32fc57:19:ffff:ffff:ffff:ffff:ffff:ffff
27fc57:1a::/32fc57:1a:ffff:ffff:ffff:ffff:ffff:ffff
28fc57:1b::/32fc57:1b:ffff:ffff:ffff:ffff:ffff:ffff
29fc57:1c::/32fc57:1c:ffff:ffff:ffff:ffff:ffff:ffff
30fc57:1d::/32fc57:1d:ffff:ffff:ffff:ffff:ffff:ffff
31fc57:1e::/32fc57:1e:ffff:ffff:ffff:ffff:ffff:ffff
32fc57:1f::/32fc57:1f:ffff:ffff:ffff:ffff:ffff:ffff
33fc57:20::/32fc57:20:ffff:ffff:ffff:ffff:ffff:ffff
34fc57:21::/32fc57:21:ffff:ffff:ffff:ffff:ffff:ffff
35fc57:22::/32fc57:22:ffff:ffff:ffff:ffff:ffff:ffff
36fc57:23::/32fc57:23:ffff:ffff:ffff:ffff:ffff:ffff
37fc57:24::/32fc57:24:ffff:ffff:ffff:ffff:ffff:ffff
38fc57:25::/32fc57:25:ffff:ffff:ffff:ffff:ffff:ffff
39fc57:26::/32fc57:26:ffff:ffff:ffff:ffff:ffff:ffff
40fc57:27::/32fc57:27:ffff:ffff:ffff:ffff:ffff:ffff
41fc57:28::/32fc57:28:ffff:ffff:ffff:ffff:ffff:ffff
42fc57:29::/32fc57:29:ffff:ffff:ffff:ffff:ffff:ffff
43fc57:2a::/32fc57:2a:ffff:ffff:ffff:ffff:ffff:ffff
44fc57:2b::/32fc57:2b:ffff:ffff:ffff:ffff:ffff:ffff
45fc57:2c::/32fc57:2c:ffff:ffff:ffff:ffff:ffff:ffff
46fc57:2d::/32fc57:2d:ffff:ffff:ffff:ffff:ffff:ffff
47fc57:2e::/32fc57:2e:ffff:ffff:ffff:ffff:ffff:ffff
48fc57:2f::/32fc57:2f:ffff:ffff:ffff:ffff:ffff:ffff
49fc57:30::/32fc57:30:ffff:ffff:ffff:ffff:ffff:ffff
50fc57:31::/32fc57:31:ffff:ffff:ffff:ffff:ffff:ffff
51fc57:32::/32fc57:32:ffff:ffff:ffff:ffff:ffff:ffff
52fc57:33::/32fc57:33:ffff:ffff:ffff:ffff:ffff:ffff
53fc57:34::/32fc57:34:ffff:ffff:ffff:ffff:ffff:ffff
54fc57:35::/32fc57:35:ffff:ffff:ffff:ffff:ffff:ffff
55fc57:36::/32fc57:36:ffff:ffff:ffff:ffff:ffff:ffff
56fc57:37::/32fc57:37:ffff:ffff:ffff:ffff:ffff:ffff
57fc57:38::/32fc57:38:ffff:ffff:ffff:ffff:ffff:ffff
58fc57:39::/32fc57:39:ffff:ffff:ffff:ffff:ffff:ffff
59fc57:3a::/32fc57:3a:ffff:ffff:ffff:ffff:ffff:ffff
60fc57:3b::/32fc57:3b:ffff:ffff:ffff:ffff:ffff:ffff
61fc57:3c::/32fc57:3c:ffff:ffff:ffff:ffff:ffff:ffff
62fc57:3d::/32fc57:3d:ffff:ffff:ffff:ffff:ffff:ffff
63fc57:3e::/32fc57:3e:ffff:ffff:ffff:ffff:ffff:ffff
64fc57:3f::/32fc57:3f:ffff:ffff:ffff:ffff:ffff:ffff
65fc57:40::/32fc57:40:ffff:ffff:ffff:ffff:ffff:ffff
66fc57:41::/32fc57:41:ffff:ffff:ffff:ffff:ffff:ffff
67fc57:42::/32fc57:42:ffff:ffff:ffff:ffff:ffff:ffff
68fc57:43::/32fc57:43:ffff:ffff:ffff:ffff:ffff:ffff
69fc57:44::/32fc57:44:ffff:ffff:ffff:ffff:ffff:ffff
70fc57:45::/32fc57:45:ffff:ffff:ffff:ffff:ffff:ffff
71fc57:46::/32fc57:46:ffff:ffff:ffff:ffff:ffff:ffff
72fc57:47::/32fc57:47:ffff:ffff:ffff:ffff:ffff:ffff
73fc57:48::/32fc57:48:ffff:ffff:ffff:ffff:ffff:ffff
74fc57:49::/32fc57:49:ffff:ffff:ffff:ffff:ffff:ffff
75fc57:4a::/32fc57:4a:ffff:ffff:ffff:ffff:ffff:ffff
76fc57:4b::/32fc57:4b:ffff:ffff:ffff:ffff:ffff:ffff
77fc57:4c::/32fc57:4c:ffff:ffff:ffff:ffff:ffff:ffff
78fc57:4d::/32fc57:4d:ffff:ffff:ffff:ffff:ffff:ffff
79fc57:4e::/32fc57:4e:ffff:ffff:ffff:ffff:ffff:ffff
80fc57:4f::/32fc57:4f:ffff:ffff:ffff:ffff:ffff:ffff
81fc57:50::/32fc57:50:ffff:ffff:ffff:ffff:ffff:ffff
82fc57:51::/32fc57:51:ffff:ffff:ffff:ffff:ffff:ffff
83fc57:52::/32fc57:52:ffff:ffff:ffff:ffff:ffff:ffff
84fc57:53::/32fc57:53:ffff:ffff:ffff:ffff:ffff:ffff
85fc57:54::/32fc57:54:ffff:ffff:ffff:ffff:ffff:ffff
86fc57:55::/32fc57:55:ffff:ffff:ffff:ffff:ffff:ffff
87fc57:56::/32fc57:56:ffff:ffff:ffff:ffff:ffff:ffff
88fc57:57::/32fc57:57:ffff:ffff:ffff:ffff:ffff:ffff
89fc57:58::/32fc57:58:ffff:ffff:ffff:ffff:ffff:ffff
90fc57:59::/32fc57:59:ffff:ffff:ffff:ffff:ffff:ffff
91fc57:5a::/32fc57:5a:ffff:ffff:ffff:ffff:ffff:ffff
92fc57:5b::/32fc57:5b:ffff:ffff:ffff:ffff:ffff:ffff
93fc57:5c::/32fc57:5c:ffff:ffff:ffff:ffff:ffff:ffff
94fc57:5d::/32fc57:5d:ffff:ffff:ffff:ffff:ffff:ffff
95fc57:5e::/32fc57:5e:ffff:ffff:ffff:ffff:ffff:ffff
96fc57:5f::/32fc57:5f:ffff:ffff:ffff:ffff:ffff:ffff
97fc57:60::/32fc57:60:ffff:ffff:ffff:ffff:ffff:ffff
98fc57:61::/32fc57:61:ffff:ffff:ffff:ffff:ffff:ffff
99fc57:62::/32fc57:62:ffff:ffff:ffff:ffff:ffff:ffff
100fc57:63::/32fc57:63:ffff:ffff:ffff:ffff:ffff:ffff
101fc57:64::/32fc57:64:ffff:ffff:ffff:ffff:ffff:ffff
102fc57:65::/32fc57:65:ffff:ffff:ffff:ffff:ffff:ffff
103fc57:66::/32fc57:66:ffff:ffff:ffff:ffff:ffff:ffff
104fc57:67::/32fc57:67:ffff:ffff:ffff:ffff:ffff:ffff
105fc57:68::/32fc57:68:ffff:ffff:ffff:ffff:ffff:ffff
106fc57:69::/32fc57:69:ffff:ffff:ffff:ffff:ffff:ffff
107fc57:6a::/32fc57:6a:ffff:ffff:ffff:ffff:ffff:ffff
108fc57:6b::/32fc57:6b:ffff:ffff:ffff:ffff:ffff:ffff
109fc57:6c::/32fc57:6c:ffff:ffff:ffff:ffff:ffff:ffff
110fc57:6d::/32fc57:6d:ffff:ffff:ffff:ffff:ffff:ffff
111fc57:6e::/32fc57:6e:ffff:ffff:ffff:ffff:ffff:ffff
112fc57:6f::/32fc57:6f:ffff:ffff:ffff:ffff:ffff:ffff
113fc57:70::/32fc57:70:ffff:ffff:ffff:ffff:ffff:ffff
114fc57:71::/32fc57:71:ffff:ffff:ffff:ffff:ffff:ffff
115fc57:72::/32fc57:72:ffff:ffff:ffff:ffff:ffff:ffff
116fc57:73::/32fc57:73:ffff:ffff:ffff:ffff:ffff:ffff
117fc57:74::/32fc57:74:ffff:ffff:ffff:ffff:ffff:ffff
118fc57:75::/32fc57:75:ffff:ffff:ffff:ffff:ffff:ffff
119fc57:76::/32fc57:76:ffff:ffff:ffff:ffff:ffff:ffff
120fc57:77::/32fc57:77:ffff:ffff:ffff:ffff:ffff:ffff
121fc57:78::/32fc57:78:ffff:ffff:ffff:ffff:ffff:ffff
122fc57:79::/32fc57:79:ffff:ffff:ffff:ffff:ffff:ffff
123fc57:7a::/32fc57:7a:ffff:ffff:ffff:ffff:ffff:ffff
124fc57:7b::/32fc57:7b:ffff:ffff:ffff:ffff:ffff:ffff
125fc57:7c::/32fc57:7c:ffff:ffff:ffff:ffff:ffff:ffff
126fc57:7d::/32fc57:7d:ffff:ffff:ffff:ffff:ffff:ffff
127fc57:7e::/32fc57:7e:ffff:ffff:ffff:ffff:ffff:ffff
128fc57:7f::/32fc57:7f:ffff:ffff:ffff:ffff:ffff:ffff
129fc57:80::/32fc57:80:ffff:ffff:ffff:ffff:ffff:ffff
130fc57:81::/32fc57:81:ffff:ffff:ffff:ffff:ffff:ffff
131fc57:82::/32fc57:82:ffff:ffff:ffff:ffff:ffff:ffff
132fc57:83::/32fc57:83:ffff:ffff:ffff:ffff:ffff:ffff
133fc57:84::/32fc57:84:ffff:ffff:ffff:ffff:ffff:ffff
134fc57:85::/32fc57:85:ffff:ffff:ffff:ffff:ffff:ffff
135fc57:86::/32fc57:86:ffff:ffff:ffff:ffff:ffff:ffff
136fc57:87::/32fc57:87:ffff:ffff:ffff:ffff:ffff:ffff
137fc57:88::/32fc57:88:ffff:ffff:ffff:ffff:ffff:ffff
138fc57:89::/32fc57:89:ffff:ffff:ffff:ffff:ffff:ffff
139fc57:8a::/32fc57:8a:ffff:ffff:ffff:ffff:ffff:ffff
140fc57:8b::/32fc57:8b:ffff:ffff:ffff:ffff:ffff:ffff
141fc57:8c::/32fc57:8c:ffff:ffff:ffff:ffff:ffff:ffff
142fc57:8d::/32fc57:8d:ffff:ffff:ffff:ffff:ffff:ffff
143fc57:8e::/32fc57:8e:ffff:ffff:ffff:ffff:ffff:ffff
144fc57:8f::/32fc57:8f:ffff:ffff:ffff:ffff:ffff:ffff
145fc57:90::/32fc57:90:ffff:ffff:ffff:ffff:ffff:ffff
146fc57:91::/32fc57:91:ffff:ffff:ffff:ffff:ffff:ffff
147fc57:92::/32fc57:92:ffff:ffff:ffff:ffff:ffff:ffff
148fc57:93::/32fc57:93:ffff:ffff:ffff:ffff:ffff:ffff
149fc57:94::/32fc57:94:ffff:ffff:ffff:ffff:ffff:ffff
150fc57:95::/32fc57:95:ffff:ffff:ffff:ffff:ffff:ffff
151fc57:96::/32fc57:96:ffff:ffff:ffff:ffff:ffff:ffff
152fc57:97::/32fc57:97:ffff:ffff:ffff:ffff:ffff:ffff
153fc57:98::/32fc57:98:ffff:ffff:ffff:ffff:ffff:ffff
154fc57:99::/32fc57:99:ffff:ffff:ffff:ffff:ffff:ffff
155fc57:9a::/32fc57:9a:ffff:ffff:ffff:ffff:ffff:ffff
156fc57:9b::/32fc57:9b:ffff:ffff:ffff:ffff:ffff:ffff
157fc57:9c::/32fc57:9c:ffff:ffff:ffff:ffff:ffff:ffff
158fc57:9d::/32fc57:9d:ffff:ffff:ffff:ffff:ffff:ffff
159fc57:9e::/32fc57:9e:ffff:ffff:ffff:ffff:ffff:ffff
160fc57:9f::/32fc57:9f:ffff:ffff:ffff:ffff:ffff:ffff
161fc57:a0::/32fc57:a0:ffff:ffff:ffff:ffff:ffff:ffff
162fc57:a1::/32fc57:a1:ffff:ffff:ffff:ffff:ffff:ffff
163fc57:a2::/32fc57:a2:ffff:ffff:ffff:ffff:ffff:ffff
164fc57:a3::/32fc57:a3:ffff:ffff:ffff:ffff:ffff:ffff
165fc57:a4::/32fc57:a4:ffff:ffff:ffff:ffff:ffff:ffff
166fc57:a5::/32fc57:a5:ffff:ffff:ffff:ffff:ffff:ffff
167fc57:a6::/32fc57:a6:ffff:ffff:ffff:ffff:ffff:ffff
168fc57:a7::/32fc57:a7:ffff:ffff:ffff:ffff:ffff:ffff
169fc57:a8::/32fc57:a8:ffff:ffff:ffff:ffff:ffff:ffff
170fc57:a9::/32fc57:a9:ffff:ffff:ffff:ffff:ffff:ffff
171fc57:aa::/32fc57:aa:ffff:ffff:ffff:ffff:ffff:ffff
172fc57:ab::/32fc57:ab:ffff:ffff:ffff:ffff:ffff:ffff
173fc57:ac::/32fc57:ac:ffff:ffff:ffff:ffff:ffff:ffff
174fc57:ad::/32fc57:ad:ffff:ffff:ffff:ffff:ffff:ffff
175fc57:ae::/32fc57:ae:ffff:ffff:ffff:ffff:ffff:ffff
176fc57:af::/32fc57:af:ffff:ffff:ffff:ffff:ffff:ffff
177fc57:b0::/32fc57:b0:ffff:ffff:ffff:ffff:ffff:ffff
178fc57:b1::/32fc57:b1:ffff:ffff:ffff:ffff:ffff:ffff
179fc57:b2::/32fc57:b2:ffff:ffff:ffff:ffff:ffff:ffff
180fc57:b3::/32fc57:b3:ffff:ffff:ffff:ffff:ffff:ffff
181fc57:b4::/32fc57:b4:ffff:ffff:ffff:ffff:ffff:ffff
182fc57:b5::/32fc57:b5:ffff:ffff:ffff:ffff:ffff:ffff
183fc57:b6::/32fc57:b6:ffff:ffff:ffff:ffff:ffff:ffff
184fc57:b7::/32fc57:b7:ffff:ffff:ffff:ffff:ffff:ffff
185fc57:b8::/32fc57:b8:ffff:ffff:ffff:ffff:ffff:ffff
186fc57:b9::/32fc57:b9:ffff:ffff:ffff:ffff:ffff:ffff
187fc57:ba::/32fc57:ba:ffff:ffff:ffff:ffff:ffff:ffff
188fc57:bb::/32fc57:bb:ffff:ffff:ffff:ffff:ffff:ffff
189fc57:bc::/32fc57:bc:ffff:ffff:ffff:ffff:ffff:ffff
190fc57:bd::/32fc57:bd:ffff:ffff:ffff:ffff:ffff:ffff
191fc57:be::/32fc57:be:ffff:ffff:ffff:ffff:ffff:ffff
192fc57:bf::/32fc57:bf:ffff:ffff:ffff:ffff:ffff:ffff
193fc57:c0::/32fc57:c0:ffff:ffff:ffff:ffff:ffff:ffff
194fc57:c1::/32fc57:c1:ffff:ffff:ffff:ffff:ffff:ffff
195fc57:c2::/32fc57:c2:ffff:ffff:ffff:ffff:ffff:ffff
196fc57:c3::/32fc57:c3:ffff:ffff:ffff:ffff:ffff:ffff
197fc57:c4::/32fc57:c4:ffff:ffff:ffff:ffff:ffff:ffff
198fc57:c5::/32fc57:c5:ffff:ffff:ffff:ffff:ffff:ffff
199fc57:c6::/32fc57:c6:ffff:ffff:ffff:ffff:ffff:ffff
200fc57:c7::/32fc57:c7:ffff:ffff:ffff:ffff:ffff:ffff
201fc57:c8::/32fc57:c8:ffff:ffff:ffff:ffff:ffff:ffff
202fc57:c9::/32fc57:c9:ffff:ffff:ffff:ffff:ffff:ffff
203fc57:ca::/32fc57:ca:ffff:ffff:ffff:ffff:ffff:ffff
204fc57:cb::/32fc57:cb:ffff:ffff:ffff:ffff:ffff:ffff
205fc57:cc::/32fc57:cc:ffff:ffff:ffff:ffff:ffff:ffff
206fc57:cd::/32fc57:cd:ffff:ffff:ffff:ffff:ffff:ffff
207fc57:ce::/32fc57:ce:ffff:ffff:ffff:ffff:ffff:ffff
208fc57:cf::/32fc57:cf:ffff:ffff:ffff:ffff:ffff:ffff
209fc57:d0::/32fc57:d0:ffff:ffff:ffff:ffff:ffff:ffff
210fc57:d1::/32fc57:d1:ffff:ffff:ffff:ffff:ffff:ffff
211fc57:d2::/32fc57:d2:ffff:ffff:ffff:ffff:ffff:ffff
212fc57:d3::/32fc57:d3:ffff:ffff:ffff:ffff:ffff:ffff
213fc57:d4::/32fc57:d4:ffff:ffff:ffff:ffff:ffff:ffff
214fc57:d5::/32fc57:d5:ffff:ffff:ffff:ffff:ffff:ffff
215fc57:d6::/32fc57:d6:ffff:ffff:ffff:ffff:ffff:ffff
216fc57:d7::/32fc57:d7:ffff:ffff:ffff:ffff:ffff:ffff
217fc57:d8::/32fc57:d8:ffff:ffff:ffff:ffff:ffff:ffff
218fc57:d9::/32fc57:d9:ffff:ffff:ffff:ffff:ffff:ffff
219fc57:da::/32fc57:da:ffff:ffff:ffff:ffff:ffff:ffff
220fc57:db::/32fc57:db:ffff:ffff:ffff:ffff:ffff:ffff
221fc57:dc::/32fc57:dc:ffff:ffff:ffff:ffff:ffff:ffff
222fc57:dd::/32fc57:dd:ffff:ffff:ffff:ffff:ffff:ffff
223fc57:de::/32fc57:de:ffff:ffff:ffff:ffff:ffff:ffff
224fc57:df::/32fc57:df:ffff:ffff:ffff:ffff:ffff:ffff
225fc57:e0::/32fc57:e0:ffff:ffff:ffff:ffff:ffff:ffff
226fc57:e1::/32fc57:e1:ffff:ffff:ffff:ffff:ffff:ffff
227fc57:e2::/32fc57:e2:ffff:ffff:ffff:ffff:ffff:ffff
228fc57:e3::/32fc57:e3:ffff:ffff:ffff:ffff:ffff:ffff
229fc57:e4::/32fc57:e4:ffff:ffff:ffff:ffff:ffff:ffff
230fc57:e5::/32fc57:e5:ffff:ffff:ffff:ffff:ffff:ffff
231fc57:e6::/32fc57:e6:ffff:ffff:ffff:ffff:ffff:ffff
232fc57:e7::/32fc57:e7:ffff:ffff:ffff:ffff:ffff:ffff
233fc57:e8::/32fc57:e8:ffff:ffff:ffff:ffff:ffff:ffff
234fc57:e9::/32fc57:e9:ffff:ffff:ffff:ffff:ffff:ffff
235fc57:ea::/32fc57:ea:ffff:ffff:ffff:ffff:ffff:ffff
236fc57:eb::/32fc57:eb:ffff:ffff:ffff:ffff:ffff:ffff
237fc57:ec::/32fc57:ec:ffff:ffff:ffff:ffff:ffff:ffff
238fc57:ed::/32fc57:ed:ffff:ffff:ffff:ffff:ffff:ffff
239fc57:ee::/32fc57:ee:ffff:ffff:ffff:ffff:ffff:ffff
240fc57:ef::/32fc57:ef:ffff:ffff:ffff:ffff:ffff:ffff
241fc57:f0::/32fc57:f0:ffff:ffff:ffff:ffff:ffff:ffff
242fc57:f1::/32fc57:f1:ffff:ffff:ffff:ffff:ffff:ffff
243fc57:f2::/32fc57:f2:ffff:ffff:ffff:ffff:ffff:ffff
244fc57:f3::/32fc57:f3:ffff:ffff:ffff:ffff:ffff:ffff
245fc57:f4::/32fc57:f4:ffff:ffff:ffff:ffff:ffff:ffff
246fc57:f5::/32fc57:f5:ffff:ffff:ffff:ffff:ffff:ffff
247fc57:f6::/32fc57:f6:ffff:ffff:ffff:ffff:ffff:ffff
248fc57:f7::/32fc57:f7:ffff:ffff:ffff:ffff:ffff:ffff
249fc57:f8::/32fc57:f8:ffff:ffff:ffff:ffff:ffff:ffff
250fc57:f9::/32fc57:f9:ffff:ffff:ffff:ffff:ffff:ffff
251fc57:fa::/32fc57:fa:ffff:ffff:ffff:ffff:ffff:ffff
252fc57:fb::/32fc57:fb:ffff:ffff:ffff:ffff:ffff:ffff
253fc57:fc::/32fc57:fc:ffff:ffff:ffff:ffff:ffff:ffff
254fc57:fd::/32fc57:fd:ffff:ffff:ffff:ffff:ffff:ffff
255fc57:fe::/32fc57:fe:ffff:ffff:ffff:ffff:ffff:ffff
256fc57:ff::/32fc57: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.