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
fcb4::/16
First address
fcb4::
Last address
fcb4: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
fcb4:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zone
4.b.c.f.ip6.arpa
Split into smaller subnets/28
/17 (2)/18 (4)/19 (8)/20 (16)/24 (256)/28 (4,096)/32 (65,536)

fcb4::/16 makes 4,096 subnets of /28; the first 256 are listed.

Subnets
#SubnetLast address
1fcb4::/28fcb4:f:ffff:ffff:ffff:ffff:ffff:ffff
2fcb4:10::/28fcb4:1f:ffff:ffff:ffff:ffff:ffff:ffff
3fcb4:20::/28fcb4:2f:ffff:ffff:ffff:ffff:ffff:ffff
4fcb4:30::/28fcb4:3f:ffff:ffff:ffff:ffff:ffff:ffff
5fcb4:40::/28fcb4:4f:ffff:ffff:ffff:ffff:ffff:ffff
6fcb4:50::/28fcb4:5f:ffff:ffff:ffff:ffff:ffff:ffff
7fcb4:60::/28fcb4:6f:ffff:ffff:ffff:ffff:ffff:ffff
8fcb4:70::/28fcb4:7f:ffff:ffff:ffff:ffff:ffff:ffff
9fcb4:80::/28fcb4:8f:ffff:ffff:ffff:ffff:ffff:ffff
10fcb4:90::/28fcb4:9f:ffff:ffff:ffff:ffff:ffff:ffff
11fcb4:a0::/28fcb4:af:ffff:ffff:ffff:ffff:ffff:ffff
12fcb4:b0::/28fcb4:bf:ffff:ffff:ffff:ffff:ffff:ffff
13fcb4:c0::/28fcb4:cf:ffff:ffff:ffff:ffff:ffff:ffff
14fcb4:d0::/28fcb4:df:ffff:ffff:ffff:ffff:ffff:ffff
15fcb4:e0::/28fcb4:ef:ffff:ffff:ffff:ffff:ffff:ffff
16fcb4:f0::/28fcb4:ff:ffff:ffff:ffff:ffff:ffff:ffff
17fcb4:100::/28fcb4:10f:ffff:ffff:ffff:ffff:ffff:ffff
18fcb4:110::/28fcb4:11f:ffff:ffff:ffff:ffff:ffff:ffff
19fcb4:120::/28fcb4:12f:ffff:ffff:ffff:ffff:ffff:ffff
20fcb4:130::/28fcb4:13f:ffff:ffff:ffff:ffff:ffff:ffff
21fcb4:140::/28fcb4:14f:ffff:ffff:ffff:ffff:ffff:ffff
22fcb4:150::/28fcb4:15f:ffff:ffff:ffff:ffff:ffff:ffff
23fcb4:160::/28fcb4:16f:ffff:ffff:ffff:ffff:ffff:ffff
24fcb4:170::/28fcb4:17f:ffff:ffff:ffff:ffff:ffff:ffff
25fcb4:180::/28fcb4:18f:ffff:ffff:ffff:ffff:ffff:ffff
26fcb4:190::/28fcb4:19f:ffff:ffff:ffff:ffff:ffff:ffff
27fcb4:1a0::/28fcb4:1af:ffff:ffff:ffff:ffff:ffff:ffff
28fcb4:1b0::/28fcb4:1bf:ffff:ffff:ffff:ffff:ffff:ffff
29fcb4:1c0::/28fcb4:1cf:ffff:ffff:ffff:ffff:ffff:ffff
30fcb4:1d0::/28fcb4:1df:ffff:ffff:ffff:ffff:ffff:ffff
31fcb4:1e0::/28fcb4:1ef:ffff:ffff:ffff:ffff:ffff:ffff
32fcb4:1f0::/28fcb4:1ff:ffff:ffff:ffff:ffff:ffff:ffff
33fcb4:200::/28fcb4:20f:ffff:ffff:ffff:ffff:ffff:ffff
34fcb4:210::/28fcb4:21f:ffff:ffff:ffff:ffff:ffff:ffff
35fcb4:220::/28fcb4:22f:ffff:ffff:ffff:ffff:ffff:ffff
36fcb4:230::/28fcb4:23f:ffff:ffff:ffff:ffff:ffff:ffff
37fcb4:240::/28fcb4:24f:ffff:ffff:ffff:ffff:ffff:ffff
38fcb4:250::/28fcb4:25f:ffff:ffff:ffff:ffff:ffff:ffff
39fcb4:260::/28fcb4:26f:ffff:ffff:ffff:ffff:ffff:ffff
40fcb4:270::/28fcb4:27f:ffff:ffff:ffff:ffff:ffff:ffff
41fcb4:280::/28fcb4:28f:ffff:ffff:ffff:ffff:ffff:ffff
42fcb4:290::/28fcb4:29f:ffff:ffff:ffff:ffff:ffff:ffff
43fcb4:2a0::/28fcb4:2af:ffff:ffff:ffff:ffff:ffff:ffff
44fcb4:2b0::/28fcb4:2bf:ffff:ffff:ffff:ffff:ffff:ffff
45fcb4:2c0::/28fcb4:2cf:ffff:ffff:ffff:ffff:ffff:ffff
46fcb4:2d0::/28fcb4:2df:ffff:ffff:ffff:ffff:ffff:ffff
47fcb4:2e0::/28fcb4:2ef:ffff:ffff:ffff:ffff:ffff:ffff
48fcb4:2f0::/28fcb4:2ff:ffff:ffff:ffff:ffff:ffff:ffff
49fcb4:300::/28fcb4:30f:ffff:ffff:ffff:ffff:ffff:ffff
50fcb4:310::/28fcb4:31f:ffff:ffff:ffff:ffff:ffff:ffff
51fcb4:320::/28fcb4:32f:ffff:ffff:ffff:ffff:ffff:ffff
52fcb4:330::/28fcb4:33f:ffff:ffff:ffff:ffff:ffff:ffff
53fcb4:340::/28fcb4:34f:ffff:ffff:ffff:ffff:ffff:ffff
54fcb4:350::/28fcb4:35f:ffff:ffff:ffff:ffff:ffff:ffff
55fcb4:360::/28fcb4:36f:ffff:ffff:ffff:ffff:ffff:ffff
56fcb4:370::/28fcb4:37f:ffff:ffff:ffff:ffff:ffff:ffff
57fcb4:380::/28fcb4:38f:ffff:ffff:ffff:ffff:ffff:ffff
58fcb4:390::/28fcb4:39f:ffff:ffff:ffff:ffff:ffff:ffff
59fcb4:3a0::/28fcb4:3af:ffff:ffff:ffff:ffff:ffff:ffff
60fcb4:3b0::/28fcb4:3bf:ffff:ffff:ffff:ffff:ffff:ffff
61fcb4:3c0::/28fcb4:3cf:ffff:ffff:ffff:ffff:ffff:ffff
62fcb4:3d0::/28fcb4:3df:ffff:ffff:ffff:ffff:ffff:ffff
63fcb4:3e0::/28fcb4:3ef:ffff:ffff:ffff:ffff:ffff:ffff
64fcb4:3f0::/28fcb4:3ff:ffff:ffff:ffff:ffff:ffff:ffff
65fcb4:400::/28fcb4:40f:ffff:ffff:ffff:ffff:ffff:ffff
66fcb4:410::/28fcb4:41f:ffff:ffff:ffff:ffff:ffff:ffff
67fcb4:420::/28fcb4:42f:ffff:ffff:ffff:ffff:ffff:ffff
68fcb4:430::/28fcb4:43f:ffff:ffff:ffff:ffff:ffff:ffff
69fcb4:440::/28fcb4:44f:ffff:ffff:ffff:ffff:ffff:ffff
70fcb4:450::/28fcb4:45f:ffff:ffff:ffff:ffff:ffff:ffff
71fcb4:460::/28fcb4:46f:ffff:ffff:ffff:ffff:ffff:ffff
72fcb4:470::/28fcb4:47f:ffff:ffff:ffff:ffff:ffff:ffff
73fcb4:480::/28fcb4:48f:ffff:ffff:ffff:ffff:ffff:ffff
74fcb4:490::/28fcb4:49f:ffff:ffff:ffff:ffff:ffff:ffff
75fcb4:4a0::/28fcb4:4af:ffff:ffff:ffff:ffff:ffff:ffff
76fcb4:4b0::/28fcb4:4bf:ffff:ffff:ffff:ffff:ffff:ffff
77fcb4:4c0::/28fcb4:4cf:ffff:ffff:ffff:ffff:ffff:ffff
78fcb4:4d0::/28fcb4:4df:ffff:ffff:ffff:ffff:ffff:ffff
79fcb4:4e0::/28fcb4:4ef:ffff:ffff:ffff:ffff:ffff:ffff
80fcb4:4f0::/28fcb4:4ff:ffff:ffff:ffff:ffff:ffff:ffff
81fcb4:500::/28fcb4:50f:ffff:ffff:ffff:ffff:ffff:ffff
82fcb4:510::/28fcb4:51f:ffff:ffff:ffff:ffff:ffff:ffff
83fcb4:520::/28fcb4:52f:ffff:ffff:ffff:ffff:ffff:ffff
84fcb4:530::/28fcb4:53f:ffff:ffff:ffff:ffff:ffff:ffff
85fcb4:540::/28fcb4:54f:ffff:ffff:ffff:ffff:ffff:ffff
86fcb4:550::/28fcb4:55f:ffff:ffff:ffff:ffff:ffff:ffff
87fcb4:560::/28fcb4:56f:ffff:ffff:ffff:ffff:ffff:ffff
88fcb4:570::/28fcb4:57f:ffff:ffff:ffff:ffff:ffff:ffff
89fcb4:580::/28fcb4:58f:ffff:ffff:ffff:ffff:ffff:ffff
90fcb4:590::/28fcb4:59f:ffff:ffff:ffff:ffff:ffff:ffff
91fcb4:5a0::/28fcb4:5af:ffff:ffff:ffff:ffff:ffff:ffff
92fcb4:5b0::/28fcb4:5bf:ffff:ffff:ffff:ffff:ffff:ffff
93fcb4:5c0::/28fcb4:5cf:ffff:ffff:ffff:ffff:ffff:ffff
94fcb4:5d0::/28fcb4:5df:ffff:ffff:ffff:ffff:ffff:ffff
95fcb4:5e0::/28fcb4:5ef:ffff:ffff:ffff:ffff:ffff:ffff
96fcb4:5f0::/28fcb4:5ff:ffff:ffff:ffff:ffff:ffff:ffff
97fcb4:600::/28fcb4:60f:ffff:ffff:ffff:ffff:ffff:ffff
98fcb4:610::/28fcb4:61f:ffff:ffff:ffff:ffff:ffff:ffff
99fcb4:620::/28fcb4:62f:ffff:ffff:ffff:ffff:ffff:ffff
100fcb4:630::/28fcb4:63f:ffff:ffff:ffff:ffff:ffff:ffff
101fcb4:640::/28fcb4:64f:ffff:ffff:ffff:ffff:ffff:ffff
102fcb4:650::/28fcb4:65f:ffff:ffff:ffff:ffff:ffff:ffff
103fcb4:660::/28fcb4:66f:ffff:ffff:ffff:ffff:ffff:ffff
104fcb4:670::/28fcb4:67f:ffff:ffff:ffff:ffff:ffff:ffff
105fcb4:680::/28fcb4:68f:ffff:ffff:ffff:ffff:ffff:ffff
106fcb4:690::/28fcb4:69f:ffff:ffff:ffff:ffff:ffff:ffff
107fcb4:6a0::/28fcb4:6af:ffff:ffff:ffff:ffff:ffff:ffff
108fcb4:6b0::/28fcb4:6bf:ffff:ffff:ffff:ffff:ffff:ffff
109fcb4:6c0::/28fcb4:6cf:ffff:ffff:ffff:ffff:ffff:ffff
110fcb4:6d0::/28fcb4:6df:ffff:ffff:ffff:ffff:ffff:ffff
111fcb4:6e0::/28fcb4:6ef:ffff:ffff:ffff:ffff:ffff:ffff
112fcb4:6f0::/28fcb4:6ff:ffff:ffff:ffff:ffff:ffff:ffff
113fcb4:700::/28fcb4:70f:ffff:ffff:ffff:ffff:ffff:ffff
114fcb4:710::/28fcb4:71f:ffff:ffff:ffff:ffff:ffff:ffff
115fcb4:720::/28fcb4:72f:ffff:ffff:ffff:ffff:ffff:ffff
116fcb4:730::/28fcb4:73f:ffff:ffff:ffff:ffff:ffff:ffff
117fcb4:740::/28fcb4:74f:ffff:ffff:ffff:ffff:ffff:ffff
118fcb4:750::/28fcb4:75f:ffff:ffff:ffff:ffff:ffff:ffff
119fcb4:760::/28fcb4:76f:ffff:ffff:ffff:ffff:ffff:ffff
120fcb4:770::/28fcb4:77f:ffff:ffff:ffff:ffff:ffff:ffff
121fcb4:780::/28fcb4:78f:ffff:ffff:ffff:ffff:ffff:ffff
122fcb4:790::/28fcb4:79f:ffff:ffff:ffff:ffff:ffff:ffff
123fcb4:7a0::/28fcb4:7af:ffff:ffff:ffff:ffff:ffff:ffff
124fcb4:7b0::/28fcb4:7bf:ffff:ffff:ffff:ffff:ffff:ffff
125fcb4:7c0::/28fcb4:7cf:ffff:ffff:ffff:ffff:ffff:ffff
126fcb4:7d0::/28fcb4:7df:ffff:ffff:ffff:ffff:ffff:ffff
127fcb4:7e0::/28fcb4:7ef:ffff:ffff:ffff:ffff:ffff:ffff
128fcb4:7f0::/28fcb4:7ff:ffff:ffff:ffff:ffff:ffff:ffff
129fcb4:800::/28fcb4:80f:ffff:ffff:ffff:ffff:ffff:ffff
130fcb4:810::/28fcb4:81f:ffff:ffff:ffff:ffff:ffff:ffff
131fcb4:820::/28fcb4:82f:ffff:ffff:ffff:ffff:ffff:ffff
132fcb4:830::/28fcb4:83f:ffff:ffff:ffff:ffff:ffff:ffff
133fcb4:840::/28fcb4:84f:ffff:ffff:ffff:ffff:ffff:ffff
134fcb4:850::/28fcb4:85f:ffff:ffff:ffff:ffff:ffff:ffff
135fcb4:860::/28fcb4:86f:ffff:ffff:ffff:ffff:ffff:ffff
136fcb4:870::/28fcb4:87f:ffff:ffff:ffff:ffff:ffff:ffff
137fcb4:880::/28fcb4:88f:ffff:ffff:ffff:ffff:ffff:ffff
138fcb4:890::/28fcb4:89f:ffff:ffff:ffff:ffff:ffff:ffff
139fcb4:8a0::/28fcb4:8af:ffff:ffff:ffff:ffff:ffff:ffff
140fcb4:8b0::/28fcb4:8bf:ffff:ffff:ffff:ffff:ffff:ffff
141fcb4:8c0::/28fcb4:8cf:ffff:ffff:ffff:ffff:ffff:ffff
142fcb4:8d0::/28fcb4:8df:ffff:ffff:ffff:ffff:ffff:ffff
143fcb4:8e0::/28fcb4:8ef:ffff:ffff:ffff:ffff:ffff:ffff
144fcb4:8f0::/28fcb4:8ff:ffff:ffff:ffff:ffff:ffff:ffff
145fcb4:900::/28fcb4:90f:ffff:ffff:ffff:ffff:ffff:ffff
146fcb4:910::/28fcb4:91f:ffff:ffff:ffff:ffff:ffff:ffff
147fcb4:920::/28fcb4:92f:ffff:ffff:ffff:ffff:ffff:ffff
148fcb4:930::/28fcb4:93f:ffff:ffff:ffff:ffff:ffff:ffff
149fcb4:940::/28fcb4:94f:ffff:ffff:ffff:ffff:ffff:ffff
150fcb4:950::/28fcb4:95f:ffff:ffff:ffff:ffff:ffff:ffff
151fcb4:960::/28fcb4:96f:ffff:ffff:ffff:ffff:ffff:ffff
152fcb4:970::/28fcb4:97f:ffff:ffff:ffff:ffff:ffff:ffff
153fcb4:980::/28fcb4:98f:ffff:ffff:ffff:ffff:ffff:ffff
154fcb4:990::/28fcb4:99f:ffff:ffff:ffff:ffff:ffff:ffff
155fcb4:9a0::/28fcb4:9af:ffff:ffff:ffff:ffff:ffff:ffff
156fcb4:9b0::/28fcb4:9bf:ffff:ffff:ffff:ffff:ffff:ffff
157fcb4:9c0::/28fcb4:9cf:ffff:ffff:ffff:ffff:ffff:ffff
158fcb4:9d0::/28fcb4:9df:ffff:ffff:ffff:ffff:ffff:ffff
159fcb4:9e0::/28fcb4:9ef:ffff:ffff:ffff:ffff:ffff:ffff
160fcb4:9f0::/28fcb4:9ff:ffff:ffff:ffff:ffff:ffff:ffff
161fcb4:a00::/28fcb4:a0f:ffff:ffff:ffff:ffff:ffff:ffff
162fcb4:a10::/28fcb4:a1f:ffff:ffff:ffff:ffff:ffff:ffff
163fcb4:a20::/28fcb4:a2f:ffff:ffff:ffff:ffff:ffff:ffff
164fcb4:a30::/28fcb4:a3f:ffff:ffff:ffff:ffff:ffff:ffff
165fcb4:a40::/28fcb4:a4f:ffff:ffff:ffff:ffff:ffff:ffff
166fcb4:a50::/28fcb4:a5f:ffff:ffff:ffff:ffff:ffff:ffff
167fcb4:a60::/28fcb4:a6f:ffff:ffff:ffff:ffff:ffff:ffff
168fcb4:a70::/28fcb4:a7f:ffff:ffff:ffff:ffff:ffff:ffff
169fcb4:a80::/28fcb4:a8f:ffff:ffff:ffff:ffff:ffff:ffff
170fcb4:a90::/28fcb4:a9f:ffff:ffff:ffff:ffff:ffff:ffff
171fcb4:aa0::/28fcb4:aaf:ffff:ffff:ffff:ffff:ffff:ffff
172fcb4:ab0::/28fcb4:abf:ffff:ffff:ffff:ffff:ffff:ffff
173fcb4:ac0::/28fcb4:acf:ffff:ffff:ffff:ffff:ffff:ffff
174fcb4:ad0::/28fcb4:adf:ffff:ffff:ffff:ffff:ffff:ffff
175fcb4:ae0::/28fcb4:aef:ffff:ffff:ffff:ffff:ffff:ffff
176fcb4:af0::/28fcb4:aff:ffff:ffff:ffff:ffff:ffff:ffff
177fcb4:b00::/28fcb4:b0f:ffff:ffff:ffff:ffff:ffff:ffff
178fcb4:b10::/28fcb4:b1f:ffff:ffff:ffff:ffff:ffff:ffff
179fcb4:b20::/28fcb4:b2f:ffff:ffff:ffff:ffff:ffff:ffff
180fcb4:b30::/28fcb4:b3f:ffff:ffff:ffff:ffff:ffff:ffff
181fcb4:b40::/28fcb4:b4f:ffff:ffff:ffff:ffff:ffff:ffff
182fcb4:b50::/28fcb4:b5f:ffff:ffff:ffff:ffff:ffff:ffff
183fcb4:b60::/28fcb4:b6f:ffff:ffff:ffff:ffff:ffff:ffff
184fcb4:b70::/28fcb4:b7f:ffff:ffff:ffff:ffff:ffff:ffff
185fcb4:b80::/28fcb4:b8f:ffff:ffff:ffff:ffff:ffff:ffff
186fcb4:b90::/28fcb4:b9f:ffff:ffff:ffff:ffff:ffff:ffff
187fcb4:ba0::/28fcb4:baf:ffff:ffff:ffff:ffff:ffff:ffff
188fcb4:bb0::/28fcb4:bbf:ffff:ffff:ffff:ffff:ffff:ffff
189fcb4:bc0::/28fcb4:bcf:ffff:ffff:ffff:ffff:ffff:ffff
190fcb4:bd0::/28fcb4:bdf:ffff:ffff:ffff:ffff:ffff:ffff
191fcb4:be0::/28fcb4:bef:ffff:ffff:ffff:ffff:ffff:ffff
192fcb4:bf0::/28fcb4:bff:ffff:ffff:ffff:ffff:ffff:ffff
193fcb4:c00::/28fcb4:c0f:ffff:ffff:ffff:ffff:ffff:ffff
194fcb4:c10::/28fcb4:c1f:ffff:ffff:ffff:ffff:ffff:ffff
195fcb4:c20::/28fcb4:c2f:ffff:ffff:ffff:ffff:ffff:ffff
196fcb4:c30::/28fcb4:c3f:ffff:ffff:ffff:ffff:ffff:ffff
197fcb4:c40::/28fcb4:c4f:ffff:ffff:ffff:ffff:ffff:ffff
198fcb4:c50::/28fcb4:c5f:ffff:ffff:ffff:ffff:ffff:ffff
199fcb4:c60::/28fcb4:c6f:ffff:ffff:ffff:ffff:ffff:ffff
200fcb4:c70::/28fcb4:c7f:ffff:ffff:ffff:ffff:ffff:ffff
201fcb4:c80::/28fcb4:c8f:ffff:ffff:ffff:ffff:ffff:ffff
202fcb4:c90::/28fcb4:c9f:ffff:ffff:ffff:ffff:ffff:ffff
203fcb4:ca0::/28fcb4:caf:ffff:ffff:ffff:ffff:ffff:ffff
204fcb4:cb0::/28fcb4:cbf:ffff:ffff:ffff:ffff:ffff:ffff
205fcb4:cc0::/28fcb4:ccf:ffff:ffff:ffff:ffff:ffff:ffff
206fcb4:cd0::/28fcb4:cdf:ffff:ffff:ffff:ffff:ffff:ffff
207fcb4:ce0::/28fcb4:cef:ffff:ffff:ffff:ffff:ffff:ffff
208fcb4:cf0::/28fcb4:cff:ffff:ffff:ffff:ffff:ffff:ffff
209fcb4:d00::/28fcb4:d0f:ffff:ffff:ffff:ffff:ffff:ffff
210fcb4:d10::/28fcb4:d1f:ffff:ffff:ffff:ffff:ffff:ffff
211fcb4:d20::/28fcb4:d2f:ffff:ffff:ffff:ffff:ffff:ffff
212fcb4:d30::/28fcb4:d3f:ffff:ffff:ffff:ffff:ffff:ffff
213fcb4:d40::/28fcb4:d4f:ffff:ffff:ffff:ffff:ffff:ffff
214fcb4:d50::/28fcb4:d5f:ffff:ffff:ffff:ffff:ffff:ffff
215fcb4:d60::/28fcb4:d6f:ffff:ffff:ffff:ffff:ffff:ffff
216fcb4:d70::/28fcb4:d7f:ffff:ffff:ffff:ffff:ffff:ffff
217fcb4:d80::/28fcb4:d8f:ffff:ffff:ffff:ffff:ffff:ffff
218fcb4:d90::/28fcb4:d9f:ffff:ffff:ffff:ffff:ffff:ffff
219fcb4:da0::/28fcb4:daf:ffff:ffff:ffff:ffff:ffff:ffff
220fcb4:db0::/28fcb4:dbf:ffff:ffff:ffff:ffff:ffff:ffff
221fcb4:dc0::/28fcb4:dcf:ffff:ffff:ffff:ffff:ffff:ffff
222fcb4:dd0::/28fcb4:ddf:ffff:ffff:ffff:ffff:ffff:ffff
223fcb4:de0::/28fcb4:def:ffff:ffff:ffff:ffff:ffff:ffff
224fcb4:df0::/28fcb4:dff:ffff:ffff:ffff:ffff:ffff:ffff
225fcb4:e00::/28fcb4:e0f:ffff:ffff:ffff:ffff:ffff:ffff
226fcb4:e10::/28fcb4:e1f:ffff:ffff:ffff:ffff:ffff:ffff
227fcb4:e20::/28fcb4:e2f:ffff:ffff:ffff:ffff:ffff:ffff
228fcb4:e30::/28fcb4:e3f:ffff:ffff:ffff:ffff:ffff:ffff
229fcb4:e40::/28fcb4:e4f:ffff:ffff:ffff:ffff:ffff:ffff
230fcb4:e50::/28fcb4:e5f:ffff:ffff:ffff:ffff:ffff:ffff
231fcb4:e60::/28fcb4:e6f:ffff:ffff:ffff:ffff:ffff:ffff
232fcb4:e70::/28fcb4:e7f:ffff:ffff:ffff:ffff:ffff:ffff
233fcb4:e80::/28fcb4:e8f:ffff:ffff:ffff:ffff:ffff:ffff
234fcb4:e90::/28fcb4:e9f:ffff:ffff:ffff:ffff:ffff:ffff
235fcb4:ea0::/28fcb4:eaf:ffff:ffff:ffff:ffff:ffff:ffff
236fcb4:eb0::/28fcb4:ebf:ffff:ffff:ffff:ffff:ffff:ffff
237fcb4:ec0::/28fcb4:ecf:ffff:ffff:ffff:ffff:ffff:ffff
238fcb4:ed0::/28fcb4:edf:ffff:ffff:ffff:ffff:ffff:ffff
239fcb4:ee0::/28fcb4:eef:ffff:ffff:ffff:ffff:ffff:ffff
240fcb4:ef0::/28fcb4:eff:ffff:ffff:ffff:ffff:ffff:ffff
241fcb4:f00::/28fcb4:f0f:ffff:ffff:ffff:ffff:ffff:ffff
242fcb4:f10::/28fcb4:f1f:ffff:ffff:ffff:ffff:ffff:ffff
243fcb4:f20::/28fcb4:f2f:ffff:ffff:ffff:ffff:ffff:ffff
244fcb4:f30::/28fcb4:f3f:ffff:ffff:ffff:ffff:ffff:ffff
245fcb4:f40::/28fcb4:f4f:ffff:ffff:ffff:ffff:ffff:ffff
246fcb4:f50::/28fcb4:f5f:ffff:ffff:ffff:ffff:ffff:ffff
247fcb4:f60::/28fcb4:f6f:ffff:ffff:ffff:ffff:ffff:ffff
248fcb4:f70::/28fcb4:f7f:ffff:ffff:ffff:ffff:ffff:ffff
249fcb4:f80::/28fcb4:f8f:ffff:ffff:ffff:ffff:ffff:ffff
250fcb4:f90::/28fcb4:f9f:ffff:ffff:ffff:ffff:ffff:ffff
251fcb4:fa0::/28fcb4:faf:ffff:ffff:ffff:ffff:ffff:ffff
252fcb4:fb0::/28fcb4:fbf:ffff:ffff:ffff:ffff:ffff:ffff
253fcb4:fc0::/28fcb4:fcf:ffff:ffff:ffff:ffff:ffff:ffff
254fcb4:fd0::/28fcb4:fdf:ffff:ffff:ffff:ffff:ffff:ffff
255fcb4:fe0::/28fcb4:fef:ffff:ffff:ffff:ffff:ffff:ffff
256fcb4:ff0::/28fcb4: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.