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
fc71::/16
First address
fc71::
Last address
fc71: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
fc71:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zone
1.7.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)

fc71::/16 makes 4,096 subnets of /28; the first 256 are listed.

Subnets
#SubnetLast address
1fc71::/28fc71:f:ffff:ffff:ffff:ffff:ffff:ffff
2fc71:10::/28fc71:1f:ffff:ffff:ffff:ffff:ffff:ffff
3fc71:20::/28fc71:2f:ffff:ffff:ffff:ffff:ffff:ffff
4fc71:30::/28fc71:3f:ffff:ffff:ffff:ffff:ffff:ffff
5fc71:40::/28fc71:4f:ffff:ffff:ffff:ffff:ffff:ffff
6fc71:50::/28fc71:5f:ffff:ffff:ffff:ffff:ffff:ffff
7fc71:60::/28fc71:6f:ffff:ffff:ffff:ffff:ffff:ffff
8fc71:70::/28fc71:7f:ffff:ffff:ffff:ffff:ffff:ffff
9fc71:80::/28fc71:8f:ffff:ffff:ffff:ffff:ffff:ffff
10fc71:90::/28fc71:9f:ffff:ffff:ffff:ffff:ffff:ffff
11fc71:a0::/28fc71:af:ffff:ffff:ffff:ffff:ffff:ffff
12fc71:b0::/28fc71:bf:ffff:ffff:ffff:ffff:ffff:ffff
13fc71:c0::/28fc71:cf:ffff:ffff:ffff:ffff:ffff:ffff
14fc71:d0::/28fc71:df:ffff:ffff:ffff:ffff:ffff:ffff
15fc71:e0::/28fc71:ef:ffff:ffff:ffff:ffff:ffff:ffff
16fc71:f0::/28fc71:ff:ffff:ffff:ffff:ffff:ffff:ffff
17fc71:100::/28fc71:10f:ffff:ffff:ffff:ffff:ffff:ffff
18fc71:110::/28fc71:11f:ffff:ffff:ffff:ffff:ffff:ffff
19fc71:120::/28fc71:12f:ffff:ffff:ffff:ffff:ffff:ffff
20fc71:130::/28fc71:13f:ffff:ffff:ffff:ffff:ffff:ffff
21fc71:140::/28fc71:14f:ffff:ffff:ffff:ffff:ffff:ffff
22fc71:150::/28fc71:15f:ffff:ffff:ffff:ffff:ffff:ffff
23fc71:160::/28fc71:16f:ffff:ffff:ffff:ffff:ffff:ffff
24fc71:170::/28fc71:17f:ffff:ffff:ffff:ffff:ffff:ffff
25fc71:180::/28fc71:18f:ffff:ffff:ffff:ffff:ffff:ffff
26fc71:190::/28fc71:19f:ffff:ffff:ffff:ffff:ffff:ffff
27fc71:1a0::/28fc71:1af:ffff:ffff:ffff:ffff:ffff:ffff
28fc71:1b0::/28fc71:1bf:ffff:ffff:ffff:ffff:ffff:ffff
29fc71:1c0::/28fc71:1cf:ffff:ffff:ffff:ffff:ffff:ffff
30fc71:1d0::/28fc71:1df:ffff:ffff:ffff:ffff:ffff:ffff
31fc71:1e0::/28fc71:1ef:ffff:ffff:ffff:ffff:ffff:ffff
32fc71:1f0::/28fc71:1ff:ffff:ffff:ffff:ffff:ffff:ffff
33fc71:200::/28fc71:20f:ffff:ffff:ffff:ffff:ffff:ffff
34fc71:210::/28fc71:21f:ffff:ffff:ffff:ffff:ffff:ffff
35fc71:220::/28fc71:22f:ffff:ffff:ffff:ffff:ffff:ffff
36fc71:230::/28fc71:23f:ffff:ffff:ffff:ffff:ffff:ffff
37fc71:240::/28fc71:24f:ffff:ffff:ffff:ffff:ffff:ffff
38fc71:250::/28fc71:25f:ffff:ffff:ffff:ffff:ffff:ffff
39fc71:260::/28fc71:26f:ffff:ffff:ffff:ffff:ffff:ffff
40fc71:270::/28fc71:27f:ffff:ffff:ffff:ffff:ffff:ffff
41fc71:280::/28fc71:28f:ffff:ffff:ffff:ffff:ffff:ffff
42fc71:290::/28fc71:29f:ffff:ffff:ffff:ffff:ffff:ffff
43fc71:2a0::/28fc71:2af:ffff:ffff:ffff:ffff:ffff:ffff
44fc71:2b0::/28fc71:2bf:ffff:ffff:ffff:ffff:ffff:ffff
45fc71:2c0::/28fc71:2cf:ffff:ffff:ffff:ffff:ffff:ffff
46fc71:2d0::/28fc71:2df:ffff:ffff:ffff:ffff:ffff:ffff
47fc71:2e0::/28fc71:2ef:ffff:ffff:ffff:ffff:ffff:ffff
48fc71:2f0::/28fc71:2ff:ffff:ffff:ffff:ffff:ffff:ffff
49fc71:300::/28fc71:30f:ffff:ffff:ffff:ffff:ffff:ffff
50fc71:310::/28fc71:31f:ffff:ffff:ffff:ffff:ffff:ffff
51fc71:320::/28fc71:32f:ffff:ffff:ffff:ffff:ffff:ffff
52fc71:330::/28fc71:33f:ffff:ffff:ffff:ffff:ffff:ffff
53fc71:340::/28fc71:34f:ffff:ffff:ffff:ffff:ffff:ffff
54fc71:350::/28fc71:35f:ffff:ffff:ffff:ffff:ffff:ffff
55fc71:360::/28fc71:36f:ffff:ffff:ffff:ffff:ffff:ffff
56fc71:370::/28fc71:37f:ffff:ffff:ffff:ffff:ffff:ffff
57fc71:380::/28fc71:38f:ffff:ffff:ffff:ffff:ffff:ffff
58fc71:390::/28fc71:39f:ffff:ffff:ffff:ffff:ffff:ffff
59fc71:3a0::/28fc71:3af:ffff:ffff:ffff:ffff:ffff:ffff
60fc71:3b0::/28fc71:3bf:ffff:ffff:ffff:ffff:ffff:ffff
61fc71:3c0::/28fc71:3cf:ffff:ffff:ffff:ffff:ffff:ffff
62fc71:3d0::/28fc71:3df:ffff:ffff:ffff:ffff:ffff:ffff
63fc71:3e0::/28fc71:3ef:ffff:ffff:ffff:ffff:ffff:ffff
64fc71:3f0::/28fc71:3ff:ffff:ffff:ffff:ffff:ffff:ffff
65fc71:400::/28fc71:40f:ffff:ffff:ffff:ffff:ffff:ffff
66fc71:410::/28fc71:41f:ffff:ffff:ffff:ffff:ffff:ffff
67fc71:420::/28fc71:42f:ffff:ffff:ffff:ffff:ffff:ffff
68fc71:430::/28fc71:43f:ffff:ffff:ffff:ffff:ffff:ffff
69fc71:440::/28fc71:44f:ffff:ffff:ffff:ffff:ffff:ffff
70fc71:450::/28fc71:45f:ffff:ffff:ffff:ffff:ffff:ffff
71fc71:460::/28fc71:46f:ffff:ffff:ffff:ffff:ffff:ffff
72fc71:470::/28fc71:47f:ffff:ffff:ffff:ffff:ffff:ffff
73fc71:480::/28fc71:48f:ffff:ffff:ffff:ffff:ffff:ffff
74fc71:490::/28fc71:49f:ffff:ffff:ffff:ffff:ffff:ffff
75fc71:4a0::/28fc71:4af:ffff:ffff:ffff:ffff:ffff:ffff
76fc71:4b0::/28fc71:4bf:ffff:ffff:ffff:ffff:ffff:ffff
77fc71:4c0::/28fc71:4cf:ffff:ffff:ffff:ffff:ffff:ffff
78fc71:4d0::/28fc71:4df:ffff:ffff:ffff:ffff:ffff:ffff
79fc71:4e0::/28fc71:4ef:ffff:ffff:ffff:ffff:ffff:ffff
80fc71:4f0::/28fc71:4ff:ffff:ffff:ffff:ffff:ffff:ffff
81fc71:500::/28fc71:50f:ffff:ffff:ffff:ffff:ffff:ffff
82fc71:510::/28fc71:51f:ffff:ffff:ffff:ffff:ffff:ffff
83fc71:520::/28fc71:52f:ffff:ffff:ffff:ffff:ffff:ffff
84fc71:530::/28fc71:53f:ffff:ffff:ffff:ffff:ffff:ffff
85fc71:540::/28fc71:54f:ffff:ffff:ffff:ffff:ffff:ffff
86fc71:550::/28fc71:55f:ffff:ffff:ffff:ffff:ffff:ffff
87fc71:560::/28fc71:56f:ffff:ffff:ffff:ffff:ffff:ffff
88fc71:570::/28fc71:57f:ffff:ffff:ffff:ffff:ffff:ffff
89fc71:580::/28fc71:58f:ffff:ffff:ffff:ffff:ffff:ffff
90fc71:590::/28fc71:59f:ffff:ffff:ffff:ffff:ffff:ffff
91fc71:5a0::/28fc71:5af:ffff:ffff:ffff:ffff:ffff:ffff
92fc71:5b0::/28fc71:5bf:ffff:ffff:ffff:ffff:ffff:ffff
93fc71:5c0::/28fc71:5cf:ffff:ffff:ffff:ffff:ffff:ffff
94fc71:5d0::/28fc71:5df:ffff:ffff:ffff:ffff:ffff:ffff
95fc71:5e0::/28fc71:5ef:ffff:ffff:ffff:ffff:ffff:ffff
96fc71:5f0::/28fc71:5ff:ffff:ffff:ffff:ffff:ffff:ffff
97fc71:600::/28fc71:60f:ffff:ffff:ffff:ffff:ffff:ffff
98fc71:610::/28fc71:61f:ffff:ffff:ffff:ffff:ffff:ffff
99fc71:620::/28fc71:62f:ffff:ffff:ffff:ffff:ffff:ffff
100fc71:630::/28fc71:63f:ffff:ffff:ffff:ffff:ffff:ffff
101fc71:640::/28fc71:64f:ffff:ffff:ffff:ffff:ffff:ffff
102fc71:650::/28fc71:65f:ffff:ffff:ffff:ffff:ffff:ffff
103fc71:660::/28fc71:66f:ffff:ffff:ffff:ffff:ffff:ffff
104fc71:670::/28fc71:67f:ffff:ffff:ffff:ffff:ffff:ffff
105fc71:680::/28fc71:68f:ffff:ffff:ffff:ffff:ffff:ffff
106fc71:690::/28fc71:69f:ffff:ffff:ffff:ffff:ffff:ffff
107fc71:6a0::/28fc71:6af:ffff:ffff:ffff:ffff:ffff:ffff
108fc71:6b0::/28fc71:6bf:ffff:ffff:ffff:ffff:ffff:ffff
109fc71:6c0::/28fc71:6cf:ffff:ffff:ffff:ffff:ffff:ffff
110fc71:6d0::/28fc71:6df:ffff:ffff:ffff:ffff:ffff:ffff
111fc71:6e0::/28fc71:6ef:ffff:ffff:ffff:ffff:ffff:ffff
112fc71:6f0::/28fc71:6ff:ffff:ffff:ffff:ffff:ffff:ffff
113fc71:700::/28fc71:70f:ffff:ffff:ffff:ffff:ffff:ffff
114fc71:710::/28fc71:71f:ffff:ffff:ffff:ffff:ffff:ffff
115fc71:720::/28fc71:72f:ffff:ffff:ffff:ffff:ffff:ffff
116fc71:730::/28fc71:73f:ffff:ffff:ffff:ffff:ffff:ffff
117fc71:740::/28fc71:74f:ffff:ffff:ffff:ffff:ffff:ffff
118fc71:750::/28fc71:75f:ffff:ffff:ffff:ffff:ffff:ffff
119fc71:760::/28fc71:76f:ffff:ffff:ffff:ffff:ffff:ffff
120fc71:770::/28fc71:77f:ffff:ffff:ffff:ffff:ffff:ffff
121fc71:780::/28fc71:78f:ffff:ffff:ffff:ffff:ffff:ffff
122fc71:790::/28fc71:79f:ffff:ffff:ffff:ffff:ffff:ffff
123fc71:7a0::/28fc71:7af:ffff:ffff:ffff:ffff:ffff:ffff
124fc71:7b0::/28fc71:7bf:ffff:ffff:ffff:ffff:ffff:ffff
125fc71:7c0::/28fc71:7cf:ffff:ffff:ffff:ffff:ffff:ffff
126fc71:7d0::/28fc71:7df:ffff:ffff:ffff:ffff:ffff:ffff
127fc71:7e0::/28fc71:7ef:ffff:ffff:ffff:ffff:ffff:ffff
128fc71:7f0::/28fc71:7ff:ffff:ffff:ffff:ffff:ffff:ffff
129fc71:800::/28fc71:80f:ffff:ffff:ffff:ffff:ffff:ffff
130fc71:810::/28fc71:81f:ffff:ffff:ffff:ffff:ffff:ffff
131fc71:820::/28fc71:82f:ffff:ffff:ffff:ffff:ffff:ffff
132fc71:830::/28fc71:83f:ffff:ffff:ffff:ffff:ffff:ffff
133fc71:840::/28fc71:84f:ffff:ffff:ffff:ffff:ffff:ffff
134fc71:850::/28fc71:85f:ffff:ffff:ffff:ffff:ffff:ffff
135fc71:860::/28fc71:86f:ffff:ffff:ffff:ffff:ffff:ffff
136fc71:870::/28fc71:87f:ffff:ffff:ffff:ffff:ffff:ffff
137fc71:880::/28fc71:88f:ffff:ffff:ffff:ffff:ffff:ffff
138fc71:890::/28fc71:89f:ffff:ffff:ffff:ffff:ffff:ffff
139fc71:8a0::/28fc71:8af:ffff:ffff:ffff:ffff:ffff:ffff
140fc71:8b0::/28fc71:8bf:ffff:ffff:ffff:ffff:ffff:ffff
141fc71:8c0::/28fc71:8cf:ffff:ffff:ffff:ffff:ffff:ffff
142fc71:8d0::/28fc71:8df:ffff:ffff:ffff:ffff:ffff:ffff
143fc71:8e0::/28fc71:8ef:ffff:ffff:ffff:ffff:ffff:ffff
144fc71:8f0::/28fc71:8ff:ffff:ffff:ffff:ffff:ffff:ffff
145fc71:900::/28fc71:90f:ffff:ffff:ffff:ffff:ffff:ffff
146fc71:910::/28fc71:91f:ffff:ffff:ffff:ffff:ffff:ffff
147fc71:920::/28fc71:92f:ffff:ffff:ffff:ffff:ffff:ffff
148fc71:930::/28fc71:93f:ffff:ffff:ffff:ffff:ffff:ffff
149fc71:940::/28fc71:94f:ffff:ffff:ffff:ffff:ffff:ffff
150fc71:950::/28fc71:95f:ffff:ffff:ffff:ffff:ffff:ffff
151fc71:960::/28fc71:96f:ffff:ffff:ffff:ffff:ffff:ffff
152fc71:970::/28fc71:97f:ffff:ffff:ffff:ffff:ffff:ffff
153fc71:980::/28fc71:98f:ffff:ffff:ffff:ffff:ffff:ffff
154fc71:990::/28fc71:99f:ffff:ffff:ffff:ffff:ffff:ffff
155fc71:9a0::/28fc71:9af:ffff:ffff:ffff:ffff:ffff:ffff
156fc71:9b0::/28fc71:9bf:ffff:ffff:ffff:ffff:ffff:ffff
157fc71:9c0::/28fc71:9cf:ffff:ffff:ffff:ffff:ffff:ffff
158fc71:9d0::/28fc71:9df:ffff:ffff:ffff:ffff:ffff:ffff
159fc71:9e0::/28fc71:9ef:ffff:ffff:ffff:ffff:ffff:ffff
160fc71:9f0::/28fc71:9ff:ffff:ffff:ffff:ffff:ffff:ffff
161fc71:a00::/28fc71:a0f:ffff:ffff:ffff:ffff:ffff:ffff
162fc71:a10::/28fc71:a1f:ffff:ffff:ffff:ffff:ffff:ffff
163fc71:a20::/28fc71:a2f:ffff:ffff:ffff:ffff:ffff:ffff
164fc71:a30::/28fc71:a3f:ffff:ffff:ffff:ffff:ffff:ffff
165fc71:a40::/28fc71:a4f:ffff:ffff:ffff:ffff:ffff:ffff
166fc71:a50::/28fc71:a5f:ffff:ffff:ffff:ffff:ffff:ffff
167fc71:a60::/28fc71:a6f:ffff:ffff:ffff:ffff:ffff:ffff
168fc71:a70::/28fc71:a7f:ffff:ffff:ffff:ffff:ffff:ffff
169fc71:a80::/28fc71:a8f:ffff:ffff:ffff:ffff:ffff:ffff
170fc71:a90::/28fc71:a9f:ffff:ffff:ffff:ffff:ffff:ffff
171fc71:aa0::/28fc71:aaf:ffff:ffff:ffff:ffff:ffff:ffff
172fc71:ab0::/28fc71:abf:ffff:ffff:ffff:ffff:ffff:ffff
173fc71:ac0::/28fc71:acf:ffff:ffff:ffff:ffff:ffff:ffff
174fc71:ad0::/28fc71:adf:ffff:ffff:ffff:ffff:ffff:ffff
175fc71:ae0::/28fc71:aef:ffff:ffff:ffff:ffff:ffff:ffff
176fc71:af0::/28fc71:aff:ffff:ffff:ffff:ffff:ffff:ffff
177fc71:b00::/28fc71:b0f:ffff:ffff:ffff:ffff:ffff:ffff
178fc71:b10::/28fc71:b1f:ffff:ffff:ffff:ffff:ffff:ffff
179fc71:b20::/28fc71:b2f:ffff:ffff:ffff:ffff:ffff:ffff
180fc71:b30::/28fc71:b3f:ffff:ffff:ffff:ffff:ffff:ffff
181fc71:b40::/28fc71:b4f:ffff:ffff:ffff:ffff:ffff:ffff
182fc71:b50::/28fc71:b5f:ffff:ffff:ffff:ffff:ffff:ffff
183fc71:b60::/28fc71:b6f:ffff:ffff:ffff:ffff:ffff:ffff
184fc71:b70::/28fc71:b7f:ffff:ffff:ffff:ffff:ffff:ffff
185fc71:b80::/28fc71:b8f:ffff:ffff:ffff:ffff:ffff:ffff
186fc71:b90::/28fc71:b9f:ffff:ffff:ffff:ffff:ffff:ffff
187fc71:ba0::/28fc71:baf:ffff:ffff:ffff:ffff:ffff:ffff
188fc71:bb0::/28fc71:bbf:ffff:ffff:ffff:ffff:ffff:ffff
189fc71:bc0::/28fc71:bcf:ffff:ffff:ffff:ffff:ffff:ffff
190fc71:bd0::/28fc71:bdf:ffff:ffff:ffff:ffff:ffff:ffff
191fc71:be0::/28fc71:bef:ffff:ffff:ffff:ffff:ffff:ffff
192fc71:bf0::/28fc71:bff:ffff:ffff:ffff:ffff:ffff:ffff
193fc71:c00::/28fc71:c0f:ffff:ffff:ffff:ffff:ffff:ffff
194fc71:c10::/28fc71:c1f:ffff:ffff:ffff:ffff:ffff:ffff
195fc71:c20::/28fc71:c2f:ffff:ffff:ffff:ffff:ffff:ffff
196fc71:c30::/28fc71:c3f:ffff:ffff:ffff:ffff:ffff:ffff
197fc71:c40::/28fc71:c4f:ffff:ffff:ffff:ffff:ffff:ffff
198fc71:c50::/28fc71:c5f:ffff:ffff:ffff:ffff:ffff:ffff
199fc71:c60::/28fc71:c6f:ffff:ffff:ffff:ffff:ffff:ffff
200fc71:c70::/28fc71:c7f:ffff:ffff:ffff:ffff:ffff:ffff
201fc71:c80::/28fc71:c8f:ffff:ffff:ffff:ffff:ffff:ffff
202fc71:c90::/28fc71:c9f:ffff:ffff:ffff:ffff:ffff:ffff
203fc71:ca0::/28fc71:caf:ffff:ffff:ffff:ffff:ffff:ffff
204fc71:cb0::/28fc71:cbf:ffff:ffff:ffff:ffff:ffff:ffff
205fc71:cc0::/28fc71:ccf:ffff:ffff:ffff:ffff:ffff:ffff
206fc71:cd0::/28fc71:cdf:ffff:ffff:ffff:ffff:ffff:ffff
207fc71:ce0::/28fc71:cef:ffff:ffff:ffff:ffff:ffff:ffff
208fc71:cf0::/28fc71:cff:ffff:ffff:ffff:ffff:ffff:ffff
209fc71:d00::/28fc71:d0f:ffff:ffff:ffff:ffff:ffff:ffff
210fc71:d10::/28fc71:d1f:ffff:ffff:ffff:ffff:ffff:ffff
211fc71:d20::/28fc71:d2f:ffff:ffff:ffff:ffff:ffff:ffff
212fc71:d30::/28fc71:d3f:ffff:ffff:ffff:ffff:ffff:ffff
213fc71:d40::/28fc71:d4f:ffff:ffff:ffff:ffff:ffff:ffff
214fc71:d50::/28fc71:d5f:ffff:ffff:ffff:ffff:ffff:ffff
215fc71:d60::/28fc71:d6f:ffff:ffff:ffff:ffff:ffff:ffff
216fc71:d70::/28fc71:d7f:ffff:ffff:ffff:ffff:ffff:ffff
217fc71:d80::/28fc71:d8f:ffff:ffff:ffff:ffff:ffff:ffff
218fc71:d90::/28fc71:d9f:ffff:ffff:ffff:ffff:ffff:ffff
219fc71:da0::/28fc71:daf:ffff:ffff:ffff:ffff:ffff:ffff
220fc71:db0::/28fc71:dbf:ffff:ffff:ffff:ffff:ffff:ffff
221fc71:dc0::/28fc71:dcf:ffff:ffff:ffff:ffff:ffff:ffff
222fc71:dd0::/28fc71:ddf:ffff:ffff:ffff:ffff:ffff:ffff
223fc71:de0::/28fc71:def:ffff:ffff:ffff:ffff:ffff:ffff
224fc71:df0::/28fc71:dff:ffff:ffff:ffff:ffff:ffff:ffff
225fc71:e00::/28fc71:e0f:ffff:ffff:ffff:ffff:ffff:ffff
226fc71:e10::/28fc71:e1f:ffff:ffff:ffff:ffff:ffff:ffff
227fc71:e20::/28fc71:e2f:ffff:ffff:ffff:ffff:ffff:ffff
228fc71:e30::/28fc71:e3f:ffff:ffff:ffff:ffff:ffff:ffff
229fc71:e40::/28fc71:e4f:ffff:ffff:ffff:ffff:ffff:ffff
230fc71:e50::/28fc71:e5f:ffff:ffff:ffff:ffff:ffff:ffff
231fc71:e60::/28fc71:e6f:ffff:ffff:ffff:ffff:ffff:ffff
232fc71:e70::/28fc71:e7f:ffff:ffff:ffff:ffff:ffff:ffff
233fc71:e80::/28fc71:e8f:ffff:ffff:ffff:ffff:ffff:ffff
234fc71:e90::/28fc71:e9f:ffff:ffff:ffff:ffff:ffff:ffff
235fc71:ea0::/28fc71:eaf:ffff:ffff:ffff:ffff:ffff:ffff
236fc71:eb0::/28fc71:ebf:ffff:ffff:ffff:ffff:ffff:ffff
237fc71:ec0::/28fc71:ecf:ffff:ffff:ffff:ffff:ffff:ffff
238fc71:ed0::/28fc71:edf:ffff:ffff:ffff:ffff:ffff:ffff
239fc71:ee0::/28fc71:eef:ffff:ffff:ffff:ffff:ffff:ffff
240fc71:ef0::/28fc71:eff:ffff:ffff:ffff:ffff:ffff:ffff
241fc71:f00::/28fc71:f0f:ffff:ffff:ffff:ffff:ffff:ffff
242fc71:f10::/28fc71:f1f:ffff:ffff:ffff:ffff:ffff:ffff
243fc71:f20::/28fc71:f2f:ffff:ffff:ffff:ffff:ffff:ffff
244fc71:f30::/28fc71:f3f:ffff:ffff:ffff:ffff:ffff:ffff
245fc71:f40::/28fc71:f4f:ffff:ffff:ffff:ffff:ffff:ffff
246fc71:f50::/28fc71:f5f:ffff:ffff:ffff:ffff:ffff:ffff
247fc71:f60::/28fc71:f6f:ffff:ffff:ffff:ffff:ffff:ffff
248fc71:f70::/28fc71:f7f:ffff:ffff:ffff:ffff:ffff:ffff
249fc71:f80::/28fc71:f8f:ffff:ffff:ffff:ffff:ffff:ffff
250fc71:f90::/28fc71:f9f:ffff:ffff:ffff:ffff:ffff:ffff
251fc71:fa0::/28fc71:faf:ffff:ffff:ffff:ffff:ffff:ffff
252fc71:fb0::/28fc71:fbf:ffff:ffff:ffff:ffff:ffff:ffff
253fc71:fc0::/28fc71:fcf:ffff:ffff:ffff:ffff:ffff:ffff
254fc71:fd0::/28fc71:fdf:ffff:ffff:ffff:ffff:ffff:ffff
255fc71:fe0::/28fc71:fef:ffff:ffff:ffff:ffff:ffff:ffff
256fc71:ff0::/28fc71: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.