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/14
Addresses2^114
/64 networks2^50
Network
fcac::/14
First address
fcac::
Last address
fcaf:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
20,769,187,434,139,310,514,121,985,316,880,384 (2^114)
/64 networks (LANs)
1,125,899,906,842,624 (2^50)
Full form
fcac:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zones
c.a.c.f.ip6.arpa
d.a.c.f.ip6.arpa
e.a.c.f.ip6.arpa
f.a.c.f.ip6.arpa
/14 is not on a 4-bit boundary, so it takes 4 /16 zones.
Split into smaller subnets/28
/15 (2)/16 (4)/17 (8)/18 (16)/20 (64)/24 (1,024)/28 (16,384)

fcac::/14 makes 16,384 subnets of /28; the first 256 are listed.

Subnets
#SubnetLast address
1fcac::/28fcac:f:ffff:ffff:ffff:ffff:ffff:ffff
2fcac:10::/28fcac:1f:ffff:ffff:ffff:ffff:ffff:ffff
3fcac:20::/28fcac:2f:ffff:ffff:ffff:ffff:ffff:ffff
4fcac:30::/28fcac:3f:ffff:ffff:ffff:ffff:ffff:ffff
5fcac:40::/28fcac:4f:ffff:ffff:ffff:ffff:ffff:ffff
6fcac:50::/28fcac:5f:ffff:ffff:ffff:ffff:ffff:ffff
7fcac:60::/28fcac:6f:ffff:ffff:ffff:ffff:ffff:ffff
8fcac:70::/28fcac:7f:ffff:ffff:ffff:ffff:ffff:ffff
9fcac:80::/28fcac:8f:ffff:ffff:ffff:ffff:ffff:ffff
10fcac:90::/28fcac:9f:ffff:ffff:ffff:ffff:ffff:ffff
11fcac:a0::/28fcac:af:ffff:ffff:ffff:ffff:ffff:ffff
12fcac:b0::/28fcac:bf:ffff:ffff:ffff:ffff:ffff:ffff
13fcac:c0::/28fcac:cf:ffff:ffff:ffff:ffff:ffff:ffff
14fcac:d0::/28fcac:df:ffff:ffff:ffff:ffff:ffff:ffff
15fcac:e0::/28fcac:ef:ffff:ffff:ffff:ffff:ffff:ffff
16fcac:f0::/28fcac:ff:ffff:ffff:ffff:ffff:ffff:ffff
17fcac:100::/28fcac:10f:ffff:ffff:ffff:ffff:ffff:ffff
18fcac:110::/28fcac:11f:ffff:ffff:ffff:ffff:ffff:ffff
19fcac:120::/28fcac:12f:ffff:ffff:ffff:ffff:ffff:ffff
20fcac:130::/28fcac:13f:ffff:ffff:ffff:ffff:ffff:ffff
21fcac:140::/28fcac:14f:ffff:ffff:ffff:ffff:ffff:ffff
22fcac:150::/28fcac:15f:ffff:ffff:ffff:ffff:ffff:ffff
23fcac:160::/28fcac:16f:ffff:ffff:ffff:ffff:ffff:ffff
24fcac:170::/28fcac:17f:ffff:ffff:ffff:ffff:ffff:ffff
25fcac:180::/28fcac:18f:ffff:ffff:ffff:ffff:ffff:ffff
26fcac:190::/28fcac:19f:ffff:ffff:ffff:ffff:ffff:ffff
27fcac:1a0::/28fcac:1af:ffff:ffff:ffff:ffff:ffff:ffff
28fcac:1b0::/28fcac:1bf:ffff:ffff:ffff:ffff:ffff:ffff
29fcac:1c0::/28fcac:1cf:ffff:ffff:ffff:ffff:ffff:ffff
30fcac:1d0::/28fcac:1df:ffff:ffff:ffff:ffff:ffff:ffff
31fcac:1e0::/28fcac:1ef:ffff:ffff:ffff:ffff:ffff:ffff
32fcac:1f0::/28fcac:1ff:ffff:ffff:ffff:ffff:ffff:ffff
33fcac:200::/28fcac:20f:ffff:ffff:ffff:ffff:ffff:ffff
34fcac:210::/28fcac:21f:ffff:ffff:ffff:ffff:ffff:ffff
35fcac:220::/28fcac:22f:ffff:ffff:ffff:ffff:ffff:ffff
36fcac:230::/28fcac:23f:ffff:ffff:ffff:ffff:ffff:ffff
37fcac:240::/28fcac:24f:ffff:ffff:ffff:ffff:ffff:ffff
38fcac:250::/28fcac:25f:ffff:ffff:ffff:ffff:ffff:ffff
39fcac:260::/28fcac:26f:ffff:ffff:ffff:ffff:ffff:ffff
40fcac:270::/28fcac:27f:ffff:ffff:ffff:ffff:ffff:ffff
41fcac:280::/28fcac:28f:ffff:ffff:ffff:ffff:ffff:ffff
42fcac:290::/28fcac:29f:ffff:ffff:ffff:ffff:ffff:ffff
43fcac:2a0::/28fcac:2af:ffff:ffff:ffff:ffff:ffff:ffff
44fcac:2b0::/28fcac:2bf:ffff:ffff:ffff:ffff:ffff:ffff
45fcac:2c0::/28fcac:2cf:ffff:ffff:ffff:ffff:ffff:ffff
46fcac:2d0::/28fcac:2df:ffff:ffff:ffff:ffff:ffff:ffff
47fcac:2e0::/28fcac:2ef:ffff:ffff:ffff:ffff:ffff:ffff
48fcac:2f0::/28fcac:2ff:ffff:ffff:ffff:ffff:ffff:ffff
49fcac:300::/28fcac:30f:ffff:ffff:ffff:ffff:ffff:ffff
50fcac:310::/28fcac:31f:ffff:ffff:ffff:ffff:ffff:ffff
51fcac:320::/28fcac:32f:ffff:ffff:ffff:ffff:ffff:ffff
52fcac:330::/28fcac:33f:ffff:ffff:ffff:ffff:ffff:ffff
53fcac:340::/28fcac:34f:ffff:ffff:ffff:ffff:ffff:ffff
54fcac:350::/28fcac:35f:ffff:ffff:ffff:ffff:ffff:ffff
55fcac:360::/28fcac:36f:ffff:ffff:ffff:ffff:ffff:ffff
56fcac:370::/28fcac:37f:ffff:ffff:ffff:ffff:ffff:ffff
57fcac:380::/28fcac:38f:ffff:ffff:ffff:ffff:ffff:ffff
58fcac:390::/28fcac:39f:ffff:ffff:ffff:ffff:ffff:ffff
59fcac:3a0::/28fcac:3af:ffff:ffff:ffff:ffff:ffff:ffff
60fcac:3b0::/28fcac:3bf:ffff:ffff:ffff:ffff:ffff:ffff
61fcac:3c0::/28fcac:3cf:ffff:ffff:ffff:ffff:ffff:ffff
62fcac:3d0::/28fcac:3df:ffff:ffff:ffff:ffff:ffff:ffff
63fcac:3e0::/28fcac:3ef:ffff:ffff:ffff:ffff:ffff:ffff
64fcac:3f0::/28fcac:3ff:ffff:ffff:ffff:ffff:ffff:ffff
65fcac:400::/28fcac:40f:ffff:ffff:ffff:ffff:ffff:ffff
66fcac:410::/28fcac:41f:ffff:ffff:ffff:ffff:ffff:ffff
67fcac:420::/28fcac:42f:ffff:ffff:ffff:ffff:ffff:ffff
68fcac:430::/28fcac:43f:ffff:ffff:ffff:ffff:ffff:ffff
69fcac:440::/28fcac:44f:ffff:ffff:ffff:ffff:ffff:ffff
70fcac:450::/28fcac:45f:ffff:ffff:ffff:ffff:ffff:ffff
71fcac:460::/28fcac:46f:ffff:ffff:ffff:ffff:ffff:ffff
72fcac:470::/28fcac:47f:ffff:ffff:ffff:ffff:ffff:ffff
73fcac:480::/28fcac:48f:ffff:ffff:ffff:ffff:ffff:ffff
74fcac:490::/28fcac:49f:ffff:ffff:ffff:ffff:ffff:ffff
75fcac:4a0::/28fcac:4af:ffff:ffff:ffff:ffff:ffff:ffff
76fcac:4b0::/28fcac:4bf:ffff:ffff:ffff:ffff:ffff:ffff
77fcac:4c0::/28fcac:4cf:ffff:ffff:ffff:ffff:ffff:ffff
78fcac:4d0::/28fcac:4df:ffff:ffff:ffff:ffff:ffff:ffff
79fcac:4e0::/28fcac:4ef:ffff:ffff:ffff:ffff:ffff:ffff
80fcac:4f0::/28fcac:4ff:ffff:ffff:ffff:ffff:ffff:ffff
81fcac:500::/28fcac:50f:ffff:ffff:ffff:ffff:ffff:ffff
82fcac:510::/28fcac:51f:ffff:ffff:ffff:ffff:ffff:ffff
83fcac:520::/28fcac:52f:ffff:ffff:ffff:ffff:ffff:ffff
84fcac:530::/28fcac:53f:ffff:ffff:ffff:ffff:ffff:ffff
85fcac:540::/28fcac:54f:ffff:ffff:ffff:ffff:ffff:ffff
86fcac:550::/28fcac:55f:ffff:ffff:ffff:ffff:ffff:ffff
87fcac:560::/28fcac:56f:ffff:ffff:ffff:ffff:ffff:ffff
88fcac:570::/28fcac:57f:ffff:ffff:ffff:ffff:ffff:ffff
89fcac:580::/28fcac:58f:ffff:ffff:ffff:ffff:ffff:ffff
90fcac:590::/28fcac:59f:ffff:ffff:ffff:ffff:ffff:ffff
91fcac:5a0::/28fcac:5af:ffff:ffff:ffff:ffff:ffff:ffff
92fcac:5b0::/28fcac:5bf:ffff:ffff:ffff:ffff:ffff:ffff
93fcac:5c0::/28fcac:5cf:ffff:ffff:ffff:ffff:ffff:ffff
94fcac:5d0::/28fcac:5df:ffff:ffff:ffff:ffff:ffff:ffff
95fcac:5e0::/28fcac:5ef:ffff:ffff:ffff:ffff:ffff:ffff
96fcac:5f0::/28fcac:5ff:ffff:ffff:ffff:ffff:ffff:ffff
97fcac:600::/28fcac:60f:ffff:ffff:ffff:ffff:ffff:ffff
98fcac:610::/28fcac:61f:ffff:ffff:ffff:ffff:ffff:ffff
99fcac:620::/28fcac:62f:ffff:ffff:ffff:ffff:ffff:ffff
100fcac:630::/28fcac:63f:ffff:ffff:ffff:ffff:ffff:ffff
101fcac:640::/28fcac:64f:ffff:ffff:ffff:ffff:ffff:ffff
102fcac:650::/28fcac:65f:ffff:ffff:ffff:ffff:ffff:ffff
103fcac:660::/28fcac:66f:ffff:ffff:ffff:ffff:ffff:ffff
104fcac:670::/28fcac:67f:ffff:ffff:ffff:ffff:ffff:ffff
105fcac:680::/28fcac:68f:ffff:ffff:ffff:ffff:ffff:ffff
106fcac:690::/28fcac:69f:ffff:ffff:ffff:ffff:ffff:ffff
107fcac:6a0::/28fcac:6af:ffff:ffff:ffff:ffff:ffff:ffff
108fcac:6b0::/28fcac:6bf:ffff:ffff:ffff:ffff:ffff:ffff
109fcac:6c0::/28fcac:6cf:ffff:ffff:ffff:ffff:ffff:ffff
110fcac:6d0::/28fcac:6df:ffff:ffff:ffff:ffff:ffff:ffff
111fcac:6e0::/28fcac:6ef:ffff:ffff:ffff:ffff:ffff:ffff
112fcac:6f0::/28fcac:6ff:ffff:ffff:ffff:ffff:ffff:ffff
113fcac:700::/28fcac:70f:ffff:ffff:ffff:ffff:ffff:ffff
114fcac:710::/28fcac:71f:ffff:ffff:ffff:ffff:ffff:ffff
115fcac:720::/28fcac:72f:ffff:ffff:ffff:ffff:ffff:ffff
116fcac:730::/28fcac:73f:ffff:ffff:ffff:ffff:ffff:ffff
117fcac:740::/28fcac:74f:ffff:ffff:ffff:ffff:ffff:ffff
118fcac:750::/28fcac:75f:ffff:ffff:ffff:ffff:ffff:ffff
119fcac:760::/28fcac:76f:ffff:ffff:ffff:ffff:ffff:ffff
120fcac:770::/28fcac:77f:ffff:ffff:ffff:ffff:ffff:ffff
121fcac:780::/28fcac:78f:ffff:ffff:ffff:ffff:ffff:ffff
122fcac:790::/28fcac:79f:ffff:ffff:ffff:ffff:ffff:ffff
123fcac:7a0::/28fcac:7af:ffff:ffff:ffff:ffff:ffff:ffff
124fcac:7b0::/28fcac:7bf:ffff:ffff:ffff:ffff:ffff:ffff
125fcac:7c0::/28fcac:7cf:ffff:ffff:ffff:ffff:ffff:ffff
126fcac:7d0::/28fcac:7df:ffff:ffff:ffff:ffff:ffff:ffff
127fcac:7e0::/28fcac:7ef:ffff:ffff:ffff:ffff:ffff:ffff
128fcac:7f0::/28fcac:7ff:ffff:ffff:ffff:ffff:ffff:ffff
129fcac:800::/28fcac:80f:ffff:ffff:ffff:ffff:ffff:ffff
130fcac:810::/28fcac:81f:ffff:ffff:ffff:ffff:ffff:ffff
131fcac:820::/28fcac:82f:ffff:ffff:ffff:ffff:ffff:ffff
132fcac:830::/28fcac:83f:ffff:ffff:ffff:ffff:ffff:ffff
133fcac:840::/28fcac:84f:ffff:ffff:ffff:ffff:ffff:ffff
134fcac:850::/28fcac:85f:ffff:ffff:ffff:ffff:ffff:ffff
135fcac:860::/28fcac:86f:ffff:ffff:ffff:ffff:ffff:ffff
136fcac:870::/28fcac:87f:ffff:ffff:ffff:ffff:ffff:ffff
137fcac:880::/28fcac:88f:ffff:ffff:ffff:ffff:ffff:ffff
138fcac:890::/28fcac:89f:ffff:ffff:ffff:ffff:ffff:ffff
139fcac:8a0::/28fcac:8af:ffff:ffff:ffff:ffff:ffff:ffff
140fcac:8b0::/28fcac:8bf:ffff:ffff:ffff:ffff:ffff:ffff
141fcac:8c0::/28fcac:8cf:ffff:ffff:ffff:ffff:ffff:ffff
142fcac:8d0::/28fcac:8df:ffff:ffff:ffff:ffff:ffff:ffff
143fcac:8e0::/28fcac:8ef:ffff:ffff:ffff:ffff:ffff:ffff
144fcac:8f0::/28fcac:8ff:ffff:ffff:ffff:ffff:ffff:ffff
145fcac:900::/28fcac:90f:ffff:ffff:ffff:ffff:ffff:ffff
146fcac:910::/28fcac:91f:ffff:ffff:ffff:ffff:ffff:ffff
147fcac:920::/28fcac:92f:ffff:ffff:ffff:ffff:ffff:ffff
148fcac:930::/28fcac:93f:ffff:ffff:ffff:ffff:ffff:ffff
149fcac:940::/28fcac:94f:ffff:ffff:ffff:ffff:ffff:ffff
150fcac:950::/28fcac:95f:ffff:ffff:ffff:ffff:ffff:ffff
151fcac:960::/28fcac:96f:ffff:ffff:ffff:ffff:ffff:ffff
152fcac:970::/28fcac:97f:ffff:ffff:ffff:ffff:ffff:ffff
153fcac:980::/28fcac:98f:ffff:ffff:ffff:ffff:ffff:ffff
154fcac:990::/28fcac:99f:ffff:ffff:ffff:ffff:ffff:ffff
155fcac:9a0::/28fcac:9af:ffff:ffff:ffff:ffff:ffff:ffff
156fcac:9b0::/28fcac:9bf:ffff:ffff:ffff:ffff:ffff:ffff
157fcac:9c0::/28fcac:9cf:ffff:ffff:ffff:ffff:ffff:ffff
158fcac:9d0::/28fcac:9df:ffff:ffff:ffff:ffff:ffff:ffff
159fcac:9e0::/28fcac:9ef:ffff:ffff:ffff:ffff:ffff:ffff
160fcac:9f0::/28fcac:9ff:ffff:ffff:ffff:ffff:ffff:ffff
161fcac:a00::/28fcac:a0f:ffff:ffff:ffff:ffff:ffff:ffff
162fcac:a10::/28fcac:a1f:ffff:ffff:ffff:ffff:ffff:ffff
163fcac:a20::/28fcac:a2f:ffff:ffff:ffff:ffff:ffff:ffff
164fcac:a30::/28fcac:a3f:ffff:ffff:ffff:ffff:ffff:ffff
165fcac:a40::/28fcac:a4f:ffff:ffff:ffff:ffff:ffff:ffff
166fcac:a50::/28fcac:a5f:ffff:ffff:ffff:ffff:ffff:ffff
167fcac:a60::/28fcac:a6f:ffff:ffff:ffff:ffff:ffff:ffff
168fcac:a70::/28fcac:a7f:ffff:ffff:ffff:ffff:ffff:ffff
169fcac:a80::/28fcac:a8f:ffff:ffff:ffff:ffff:ffff:ffff
170fcac:a90::/28fcac:a9f:ffff:ffff:ffff:ffff:ffff:ffff
171fcac:aa0::/28fcac:aaf:ffff:ffff:ffff:ffff:ffff:ffff
172fcac:ab0::/28fcac:abf:ffff:ffff:ffff:ffff:ffff:ffff
173fcac:ac0::/28fcac:acf:ffff:ffff:ffff:ffff:ffff:ffff
174fcac:ad0::/28fcac:adf:ffff:ffff:ffff:ffff:ffff:ffff
175fcac:ae0::/28fcac:aef:ffff:ffff:ffff:ffff:ffff:ffff
176fcac:af0::/28fcac:aff:ffff:ffff:ffff:ffff:ffff:ffff
177fcac:b00::/28fcac:b0f:ffff:ffff:ffff:ffff:ffff:ffff
178fcac:b10::/28fcac:b1f:ffff:ffff:ffff:ffff:ffff:ffff
179fcac:b20::/28fcac:b2f:ffff:ffff:ffff:ffff:ffff:ffff
180fcac:b30::/28fcac:b3f:ffff:ffff:ffff:ffff:ffff:ffff
181fcac:b40::/28fcac:b4f:ffff:ffff:ffff:ffff:ffff:ffff
182fcac:b50::/28fcac:b5f:ffff:ffff:ffff:ffff:ffff:ffff
183fcac:b60::/28fcac:b6f:ffff:ffff:ffff:ffff:ffff:ffff
184fcac:b70::/28fcac:b7f:ffff:ffff:ffff:ffff:ffff:ffff
185fcac:b80::/28fcac:b8f:ffff:ffff:ffff:ffff:ffff:ffff
186fcac:b90::/28fcac:b9f:ffff:ffff:ffff:ffff:ffff:ffff
187fcac:ba0::/28fcac:baf:ffff:ffff:ffff:ffff:ffff:ffff
188fcac:bb0::/28fcac:bbf:ffff:ffff:ffff:ffff:ffff:ffff
189fcac:bc0::/28fcac:bcf:ffff:ffff:ffff:ffff:ffff:ffff
190fcac:bd0::/28fcac:bdf:ffff:ffff:ffff:ffff:ffff:ffff
191fcac:be0::/28fcac:bef:ffff:ffff:ffff:ffff:ffff:ffff
192fcac:bf0::/28fcac:bff:ffff:ffff:ffff:ffff:ffff:ffff
193fcac:c00::/28fcac:c0f:ffff:ffff:ffff:ffff:ffff:ffff
194fcac:c10::/28fcac:c1f:ffff:ffff:ffff:ffff:ffff:ffff
195fcac:c20::/28fcac:c2f:ffff:ffff:ffff:ffff:ffff:ffff
196fcac:c30::/28fcac:c3f:ffff:ffff:ffff:ffff:ffff:ffff
197fcac:c40::/28fcac:c4f:ffff:ffff:ffff:ffff:ffff:ffff
198fcac:c50::/28fcac:c5f:ffff:ffff:ffff:ffff:ffff:ffff
199fcac:c60::/28fcac:c6f:ffff:ffff:ffff:ffff:ffff:ffff
200fcac:c70::/28fcac:c7f:ffff:ffff:ffff:ffff:ffff:ffff
201fcac:c80::/28fcac:c8f:ffff:ffff:ffff:ffff:ffff:ffff
202fcac:c90::/28fcac:c9f:ffff:ffff:ffff:ffff:ffff:ffff
203fcac:ca0::/28fcac:caf:ffff:ffff:ffff:ffff:ffff:ffff
204fcac:cb0::/28fcac:cbf:ffff:ffff:ffff:ffff:ffff:ffff
205fcac:cc0::/28fcac:ccf:ffff:ffff:ffff:ffff:ffff:ffff
206fcac:cd0::/28fcac:cdf:ffff:ffff:ffff:ffff:ffff:ffff
207fcac:ce0::/28fcac:cef:ffff:ffff:ffff:ffff:ffff:ffff
208fcac:cf0::/28fcac:cff:ffff:ffff:ffff:ffff:ffff:ffff
209fcac:d00::/28fcac:d0f:ffff:ffff:ffff:ffff:ffff:ffff
210fcac:d10::/28fcac:d1f:ffff:ffff:ffff:ffff:ffff:ffff
211fcac:d20::/28fcac:d2f:ffff:ffff:ffff:ffff:ffff:ffff
212fcac:d30::/28fcac:d3f:ffff:ffff:ffff:ffff:ffff:ffff
213fcac:d40::/28fcac:d4f:ffff:ffff:ffff:ffff:ffff:ffff
214fcac:d50::/28fcac:d5f:ffff:ffff:ffff:ffff:ffff:ffff
215fcac:d60::/28fcac:d6f:ffff:ffff:ffff:ffff:ffff:ffff
216fcac:d70::/28fcac:d7f:ffff:ffff:ffff:ffff:ffff:ffff
217fcac:d80::/28fcac:d8f:ffff:ffff:ffff:ffff:ffff:ffff
218fcac:d90::/28fcac:d9f:ffff:ffff:ffff:ffff:ffff:ffff
219fcac:da0::/28fcac:daf:ffff:ffff:ffff:ffff:ffff:ffff
220fcac:db0::/28fcac:dbf:ffff:ffff:ffff:ffff:ffff:ffff
221fcac:dc0::/28fcac:dcf:ffff:ffff:ffff:ffff:ffff:ffff
222fcac:dd0::/28fcac:ddf:ffff:ffff:ffff:ffff:ffff:ffff
223fcac:de0::/28fcac:def:ffff:ffff:ffff:ffff:ffff:ffff
224fcac:df0::/28fcac:dff:ffff:ffff:ffff:ffff:ffff:ffff
225fcac:e00::/28fcac:e0f:ffff:ffff:ffff:ffff:ffff:ffff
226fcac:e10::/28fcac:e1f:ffff:ffff:ffff:ffff:ffff:ffff
227fcac:e20::/28fcac:e2f:ffff:ffff:ffff:ffff:ffff:ffff
228fcac:e30::/28fcac:e3f:ffff:ffff:ffff:ffff:ffff:ffff
229fcac:e40::/28fcac:e4f:ffff:ffff:ffff:ffff:ffff:ffff
230fcac:e50::/28fcac:e5f:ffff:ffff:ffff:ffff:ffff:ffff
231fcac:e60::/28fcac:e6f:ffff:ffff:ffff:ffff:ffff:ffff
232fcac:e70::/28fcac:e7f:ffff:ffff:ffff:ffff:ffff:ffff
233fcac:e80::/28fcac:e8f:ffff:ffff:ffff:ffff:ffff:ffff
234fcac:e90::/28fcac:e9f:ffff:ffff:ffff:ffff:ffff:ffff
235fcac:ea0::/28fcac:eaf:ffff:ffff:ffff:ffff:ffff:ffff
236fcac:eb0::/28fcac:ebf:ffff:ffff:ffff:ffff:ffff:ffff
237fcac:ec0::/28fcac:ecf:ffff:ffff:ffff:ffff:ffff:ffff
238fcac:ed0::/28fcac:edf:ffff:ffff:ffff:ffff:ffff:ffff
239fcac:ee0::/28fcac:eef:ffff:ffff:ffff:ffff:ffff:ffff
240fcac:ef0::/28fcac:eff:ffff:ffff:ffff:ffff:ffff:ffff
241fcac:f00::/28fcac:f0f:ffff:ffff:ffff:ffff:ffff:ffff
242fcac:f10::/28fcac:f1f:ffff:ffff:ffff:ffff:ffff:ffff
243fcac:f20::/28fcac:f2f:ffff:ffff:ffff:ffff:ffff:ffff
244fcac:f30::/28fcac:f3f:ffff:ffff:ffff:ffff:ffff:ffff
245fcac:f40::/28fcac:f4f:ffff:ffff:ffff:ffff:ffff:ffff
246fcac:f50::/28fcac:f5f:ffff:ffff:ffff:ffff:ffff:ffff
247fcac:f60::/28fcac:f6f:ffff:ffff:ffff:ffff:ffff:ffff
248fcac:f70::/28fcac:f7f:ffff:ffff:ffff:ffff:ffff:ffff
249fcac:f80::/28fcac:f8f:ffff:ffff:ffff:ffff:ffff:ffff
250fcac:f90::/28fcac:f9f:ffff:ffff:ffff:ffff:ffff:ffff
251fcac:fa0::/28fcac:faf:ffff:ffff:ffff:ffff:ffff:ffff
252fcac:fb0::/28fcac:fbf:ffff:ffff:ffff:ffff:ffff:ffff
253fcac:fc0::/28fcac:fcf:ffff:ffff:ffff:ffff:ffff:ffff
254fcac:fd0::/28fcac:fdf:ffff:ffff:ffff:ffff:ffff:ffff
255fcac:fe0::/28fcac:fef:ffff:ffff:ffff:ffff:ffff:ffff
256fcac:ff0::/28fcac:fff: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.