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
fc79::/16
First address
fc79::
Last address
fc79: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
fc79:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zone
9.7.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)

fc79::/16 makes 4,096 subnets of /28; the first 256 are listed.

Subnets
#SubnetLast address
1fc79::/28fc79:f:ffff:ffff:ffff:ffff:ffff:ffff
2fc79:10::/28fc79:1f:ffff:ffff:ffff:ffff:ffff:ffff
3fc79:20::/28fc79:2f:ffff:ffff:ffff:ffff:ffff:ffff
4fc79:30::/28fc79:3f:ffff:ffff:ffff:ffff:ffff:ffff
5fc79:40::/28fc79:4f:ffff:ffff:ffff:ffff:ffff:ffff
6fc79:50::/28fc79:5f:ffff:ffff:ffff:ffff:ffff:ffff
7fc79:60::/28fc79:6f:ffff:ffff:ffff:ffff:ffff:ffff
8fc79:70::/28fc79:7f:ffff:ffff:ffff:ffff:ffff:ffff
9fc79:80::/28fc79:8f:ffff:ffff:ffff:ffff:ffff:ffff
10fc79:90::/28fc79:9f:ffff:ffff:ffff:ffff:ffff:ffff
11fc79:a0::/28fc79:af:ffff:ffff:ffff:ffff:ffff:ffff
12fc79:b0::/28fc79:bf:ffff:ffff:ffff:ffff:ffff:ffff
13fc79:c0::/28fc79:cf:ffff:ffff:ffff:ffff:ffff:ffff
14fc79:d0::/28fc79:df:ffff:ffff:ffff:ffff:ffff:ffff
15fc79:e0::/28fc79:ef:ffff:ffff:ffff:ffff:ffff:ffff
16fc79:f0::/28fc79:ff:ffff:ffff:ffff:ffff:ffff:ffff
17fc79:100::/28fc79:10f:ffff:ffff:ffff:ffff:ffff:ffff
18fc79:110::/28fc79:11f:ffff:ffff:ffff:ffff:ffff:ffff
19fc79:120::/28fc79:12f:ffff:ffff:ffff:ffff:ffff:ffff
20fc79:130::/28fc79:13f:ffff:ffff:ffff:ffff:ffff:ffff
21fc79:140::/28fc79:14f:ffff:ffff:ffff:ffff:ffff:ffff
22fc79:150::/28fc79:15f:ffff:ffff:ffff:ffff:ffff:ffff
23fc79:160::/28fc79:16f:ffff:ffff:ffff:ffff:ffff:ffff
24fc79:170::/28fc79:17f:ffff:ffff:ffff:ffff:ffff:ffff
25fc79:180::/28fc79:18f:ffff:ffff:ffff:ffff:ffff:ffff
26fc79:190::/28fc79:19f:ffff:ffff:ffff:ffff:ffff:ffff
27fc79:1a0::/28fc79:1af:ffff:ffff:ffff:ffff:ffff:ffff
28fc79:1b0::/28fc79:1bf:ffff:ffff:ffff:ffff:ffff:ffff
29fc79:1c0::/28fc79:1cf:ffff:ffff:ffff:ffff:ffff:ffff
30fc79:1d0::/28fc79:1df:ffff:ffff:ffff:ffff:ffff:ffff
31fc79:1e0::/28fc79:1ef:ffff:ffff:ffff:ffff:ffff:ffff
32fc79:1f0::/28fc79:1ff:ffff:ffff:ffff:ffff:ffff:ffff
33fc79:200::/28fc79:20f:ffff:ffff:ffff:ffff:ffff:ffff
34fc79:210::/28fc79:21f:ffff:ffff:ffff:ffff:ffff:ffff
35fc79:220::/28fc79:22f:ffff:ffff:ffff:ffff:ffff:ffff
36fc79:230::/28fc79:23f:ffff:ffff:ffff:ffff:ffff:ffff
37fc79:240::/28fc79:24f:ffff:ffff:ffff:ffff:ffff:ffff
38fc79:250::/28fc79:25f:ffff:ffff:ffff:ffff:ffff:ffff
39fc79:260::/28fc79:26f:ffff:ffff:ffff:ffff:ffff:ffff
40fc79:270::/28fc79:27f:ffff:ffff:ffff:ffff:ffff:ffff
41fc79:280::/28fc79:28f:ffff:ffff:ffff:ffff:ffff:ffff
42fc79:290::/28fc79:29f:ffff:ffff:ffff:ffff:ffff:ffff
43fc79:2a0::/28fc79:2af:ffff:ffff:ffff:ffff:ffff:ffff
44fc79:2b0::/28fc79:2bf:ffff:ffff:ffff:ffff:ffff:ffff
45fc79:2c0::/28fc79:2cf:ffff:ffff:ffff:ffff:ffff:ffff
46fc79:2d0::/28fc79:2df:ffff:ffff:ffff:ffff:ffff:ffff
47fc79:2e0::/28fc79:2ef:ffff:ffff:ffff:ffff:ffff:ffff
48fc79:2f0::/28fc79:2ff:ffff:ffff:ffff:ffff:ffff:ffff
49fc79:300::/28fc79:30f:ffff:ffff:ffff:ffff:ffff:ffff
50fc79:310::/28fc79:31f:ffff:ffff:ffff:ffff:ffff:ffff
51fc79:320::/28fc79:32f:ffff:ffff:ffff:ffff:ffff:ffff
52fc79:330::/28fc79:33f:ffff:ffff:ffff:ffff:ffff:ffff
53fc79:340::/28fc79:34f:ffff:ffff:ffff:ffff:ffff:ffff
54fc79:350::/28fc79:35f:ffff:ffff:ffff:ffff:ffff:ffff
55fc79:360::/28fc79:36f:ffff:ffff:ffff:ffff:ffff:ffff
56fc79:370::/28fc79:37f:ffff:ffff:ffff:ffff:ffff:ffff
57fc79:380::/28fc79:38f:ffff:ffff:ffff:ffff:ffff:ffff
58fc79:390::/28fc79:39f:ffff:ffff:ffff:ffff:ffff:ffff
59fc79:3a0::/28fc79:3af:ffff:ffff:ffff:ffff:ffff:ffff
60fc79:3b0::/28fc79:3bf:ffff:ffff:ffff:ffff:ffff:ffff
61fc79:3c0::/28fc79:3cf:ffff:ffff:ffff:ffff:ffff:ffff
62fc79:3d0::/28fc79:3df:ffff:ffff:ffff:ffff:ffff:ffff
63fc79:3e0::/28fc79:3ef:ffff:ffff:ffff:ffff:ffff:ffff
64fc79:3f0::/28fc79:3ff:ffff:ffff:ffff:ffff:ffff:ffff
65fc79:400::/28fc79:40f:ffff:ffff:ffff:ffff:ffff:ffff
66fc79:410::/28fc79:41f:ffff:ffff:ffff:ffff:ffff:ffff
67fc79:420::/28fc79:42f:ffff:ffff:ffff:ffff:ffff:ffff
68fc79:430::/28fc79:43f:ffff:ffff:ffff:ffff:ffff:ffff
69fc79:440::/28fc79:44f:ffff:ffff:ffff:ffff:ffff:ffff
70fc79:450::/28fc79:45f:ffff:ffff:ffff:ffff:ffff:ffff
71fc79:460::/28fc79:46f:ffff:ffff:ffff:ffff:ffff:ffff
72fc79:470::/28fc79:47f:ffff:ffff:ffff:ffff:ffff:ffff
73fc79:480::/28fc79:48f:ffff:ffff:ffff:ffff:ffff:ffff
74fc79:490::/28fc79:49f:ffff:ffff:ffff:ffff:ffff:ffff
75fc79:4a0::/28fc79:4af:ffff:ffff:ffff:ffff:ffff:ffff
76fc79:4b0::/28fc79:4bf:ffff:ffff:ffff:ffff:ffff:ffff
77fc79:4c0::/28fc79:4cf:ffff:ffff:ffff:ffff:ffff:ffff
78fc79:4d0::/28fc79:4df:ffff:ffff:ffff:ffff:ffff:ffff
79fc79:4e0::/28fc79:4ef:ffff:ffff:ffff:ffff:ffff:ffff
80fc79:4f0::/28fc79:4ff:ffff:ffff:ffff:ffff:ffff:ffff
81fc79:500::/28fc79:50f:ffff:ffff:ffff:ffff:ffff:ffff
82fc79:510::/28fc79:51f:ffff:ffff:ffff:ffff:ffff:ffff
83fc79:520::/28fc79:52f:ffff:ffff:ffff:ffff:ffff:ffff
84fc79:530::/28fc79:53f:ffff:ffff:ffff:ffff:ffff:ffff
85fc79:540::/28fc79:54f:ffff:ffff:ffff:ffff:ffff:ffff
86fc79:550::/28fc79:55f:ffff:ffff:ffff:ffff:ffff:ffff
87fc79:560::/28fc79:56f:ffff:ffff:ffff:ffff:ffff:ffff
88fc79:570::/28fc79:57f:ffff:ffff:ffff:ffff:ffff:ffff
89fc79:580::/28fc79:58f:ffff:ffff:ffff:ffff:ffff:ffff
90fc79:590::/28fc79:59f:ffff:ffff:ffff:ffff:ffff:ffff
91fc79:5a0::/28fc79:5af:ffff:ffff:ffff:ffff:ffff:ffff
92fc79:5b0::/28fc79:5bf:ffff:ffff:ffff:ffff:ffff:ffff
93fc79:5c0::/28fc79:5cf:ffff:ffff:ffff:ffff:ffff:ffff
94fc79:5d0::/28fc79:5df:ffff:ffff:ffff:ffff:ffff:ffff
95fc79:5e0::/28fc79:5ef:ffff:ffff:ffff:ffff:ffff:ffff
96fc79:5f0::/28fc79:5ff:ffff:ffff:ffff:ffff:ffff:ffff
97fc79:600::/28fc79:60f:ffff:ffff:ffff:ffff:ffff:ffff
98fc79:610::/28fc79:61f:ffff:ffff:ffff:ffff:ffff:ffff
99fc79:620::/28fc79:62f:ffff:ffff:ffff:ffff:ffff:ffff
100fc79:630::/28fc79:63f:ffff:ffff:ffff:ffff:ffff:ffff
101fc79:640::/28fc79:64f:ffff:ffff:ffff:ffff:ffff:ffff
102fc79:650::/28fc79:65f:ffff:ffff:ffff:ffff:ffff:ffff
103fc79:660::/28fc79:66f:ffff:ffff:ffff:ffff:ffff:ffff
104fc79:670::/28fc79:67f:ffff:ffff:ffff:ffff:ffff:ffff
105fc79:680::/28fc79:68f:ffff:ffff:ffff:ffff:ffff:ffff
106fc79:690::/28fc79:69f:ffff:ffff:ffff:ffff:ffff:ffff
107fc79:6a0::/28fc79:6af:ffff:ffff:ffff:ffff:ffff:ffff
108fc79:6b0::/28fc79:6bf:ffff:ffff:ffff:ffff:ffff:ffff
109fc79:6c0::/28fc79:6cf:ffff:ffff:ffff:ffff:ffff:ffff
110fc79:6d0::/28fc79:6df:ffff:ffff:ffff:ffff:ffff:ffff
111fc79:6e0::/28fc79:6ef:ffff:ffff:ffff:ffff:ffff:ffff
112fc79:6f0::/28fc79:6ff:ffff:ffff:ffff:ffff:ffff:ffff
113fc79:700::/28fc79:70f:ffff:ffff:ffff:ffff:ffff:ffff
114fc79:710::/28fc79:71f:ffff:ffff:ffff:ffff:ffff:ffff
115fc79:720::/28fc79:72f:ffff:ffff:ffff:ffff:ffff:ffff
116fc79:730::/28fc79:73f:ffff:ffff:ffff:ffff:ffff:ffff
117fc79:740::/28fc79:74f:ffff:ffff:ffff:ffff:ffff:ffff
118fc79:750::/28fc79:75f:ffff:ffff:ffff:ffff:ffff:ffff
119fc79:760::/28fc79:76f:ffff:ffff:ffff:ffff:ffff:ffff
120fc79:770::/28fc79:77f:ffff:ffff:ffff:ffff:ffff:ffff
121fc79:780::/28fc79:78f:ffff:ffff:ffff:ffff:ffff:ffff
122fc79:790::/28fc79:79f:ffff:ffff:ffff:ffff:ffff:ffff
123fc79:7a0::/28fc79:7af:ffff:ffff:ffff:ffff:ffff:ffff
124fc79:7b0::/28fc79:7bf:ffff:ffff:ffff:ffff:ffff:ffff
125fc79:7c0::/28fc79:7cf:ffff:ffff:ffff:ffff:ffff:ffff
126fc79:7d0::/28fc79:7df:ffff:ffff:ffff:ffff:ffff:ffff
127fc79:7e0::/28fc79:7ef:ffff:ffff:ffff:ffff:ffff:ffff
128fc79:7f0::/28fc79:7ff:ffff:ffff:ffff:ffff:ffff:ffff
129fc79:800::/28fc79:80f:ffff:ffff:ffff:ffff:ffff:ffff
130fc79:810::/28fc79:81f:ffff:ffff:ffff:ffff:ffff:ffff
131fc79:820::/28fc79:82f:ffff:ffff:ffff:ffff:ffff:ffff
132fc79:830::/28fc79:83f:ffff:ffff:ffff:ffff:ffff:ffff
133fc79:840::/28fc79:84f:ffff:ffff:ffff:ffff:ffff:ffff
134fc79:850::/28fc79:85f:ffff:ffff:ffff:ffff:ffff:ffff
135fc79:860::/28fc79:86f:ffff:ffff:ffff:ffff:ffff:ffff
136fc79:870::/28fc79:87f:ffff:ffff:ffff:ffff:ffff:ffff
137fc79:880::/28fc79:88f:ffff:ffff:ffff:ffff:ffff:ffff
138fc79:890::/28fc79:89f:ffff:ffff:ffff:ffff:ffff:ffff
139fc79:8a0::/28fc79:8af:ffff:ffff:ffff:ffff:ffff:ffff
140fc79:8b0::/28fc79:8bf:ffff:ffff:ffff:ffff:ffff:ffff
141fc79:8c0::/28fc79:8cf:ffff:ffff:ffff:ffff:ffff:ffff
142fc79:8d0::/28fc79:8df:ffff:ffff:ffff:ffff:ffff:ffff
143fc79:8e0::/28fc79:8ef:ffff:ffff:ffff:ffff:ffff:ffff
144fc79:8f0::/28fc79:8ff:ffff:ffff:ffff:ffff:ffff:ffff
145fc79:900::/28fc79:90f:ffff:ffff:ffff:ffff:ffff:ffff
146fc79:910::/28fc79:91f:ffff:ffff:ffff:ffff:ffff:ffff
147fc79:920::/28fc79:92f:ffff:ffff:ffff:ffff:ffff:ffff
148fc79:930::/28fc79:93f:ffff:ffff:ffff:ffff:ffff:ffff
149fc79:940::/28fc79:94f:ffff:ffff:ffff:ffff:ffff:ffff
150fc79:950::/28fc79:95f:ffff:ffff:ffff:ffff:ffff:ffff
151fc79:960::/28fc79:96f:ffff:ffff:ffff:ffff:ffff:ffff
152fc79:970::/28fc79:97f:ffff:ffff:ffff:ffff:ffff:ffff
153fc79:980::/28fc79:98f:ffff:ffff:ffff:ffff:ffff:ffff
154fc79:990::/28fc79:99f:ffff:ffff:ffff:ffff:ffff:ffff
155fc79:9a0::/28fc79:9af:ffff:ffff:ffff:ffff:ffff:ffff
156fc79:9b0::/28fc79:9bf:ffff:ffff:ffff:ffff:ffff:ffff
157fc79:9c0::/28fc79:9cf:ffff:ffff:ffff:ffff:ffff:ffff
158fc79:9d0::/28fc79:9df:ffff:ffff:ffff:ffff:ffff:ffff
159fc79:9e0::/28fc79:9ef:ffff:ffff:ffff:ffff:ffff:ffff
160fc79:9f0::/28fc79:9ff:ffff:ffff:ffff:ffff:ffff:ffff
161fc79:a00::/28fc79:a0f:ffff:ffff:ffff:ffff:ffff:ffff
162fc79:a10::/28fc79:a1f:ffff:ffff:ffff:ffff:ffff:ffff
163fc79:a20::/28fc79:a2f:ffff:ffff:ffff:ffff:ffff:ffff
164fc79:a30::/28fc79:a3f:ffff:ffff:ffff:ffff:ffff:ffff
165fc79:a40::/28fc79:a4f:ffff:ffff:ffff:ffff:ffff:ffff
166fc79:a50::/28fc79:a5f:ffff:ffff:ffff:ffff:ffff:ffff
167fc79:a60::/28fc79:a6f:ffff:ffff:ffff:ffff:ffff:ffff
168fc79:a70::/28fc79:a7f:ffff:ffff:ffff:ffff:ffff:ffff
169fc79:a80::/28fc79:a8f:ffff:ffff:ffff:ffff:ffff:ffff
170fc79:a90::/28fc79:a9f:ffff:ffff:ffff:ffff:ffff:ffff
171fc79:aa0::/28fc79:aaf:ffff:ffff:ffff:ffff:ffff:ffff
172fc79:ab0::/28fc79:abf:ffff:ffff:ffff:ffff:ffff:ffff
173fc79:ac0::/28fc79:acf:ffff:ffff:ffff:ffff:ffff:ffff
174fc79:ad0::/28fc79:adf:ffff:ffff:ffff:ffff:ffff:ffff
175fc79:ae0::/28fc79:aef:ffff:ffff:ffff:ffff:ffff:ffff
176fc79:af0::/28fc79:aff:ffff:ffff:ffff:ffff:ffff:ffff
177fc79:b00::/28fc79:b0f:ffff:ffff:ffff:ffff:ffff:ffff
178fc79:b10::/28fc79:b1f:ffff:ffff:ffff:ffff:ffff:ffff
179fc79:b20::/28fc79:b2f:ffff:ffff:ffff:ffff:ffff:ffff
180fc79:b30::/28fc79:b3f:ffff:ffff:ffff:ffff:ffff:ffff
181fc79:b40::/28fc79:b4f:ffff:ffff:ffff:ffff:ffff:ffff
182fc79:b50::/28fc79:b5f:ffff:ffff:ffff:ffff:ffff:ffff
183fc79:b60::/28fc79:b6f:ffff:ffff:ffff:ffff:ffff:ffff
184fc79:b70::/28fc79:b7f:ffff:ffff:ffff:ffff:ffff:ffff
185fc79:b80::/28fc79:b8f:ffff:ffff:ffff:ffff:ffff:ffff
186fc79:b90::/28fc79:b9f:ffff:ffff:ffff:ffff:ffff:ffff
187fc79:ba0::/28fc79:baf:ffff:ffff:ffff:ffff:ffff:ffff
188fc79:bb0::/28fc79:bbf:ffff:ffff:ffff:ffff:ffff:ffff
189fc79:bc0::/28fc79:bcf:ffff:ffff:ffff:ffff:ffff:ffff
190fc79:bd0::/28fc79:bdf:ffff:ffff:ffff:ffff:ffff:ffff
191fc79:be0::/28fc79:bef:ffff:ffff:ffff:ffff:ffff:ffff
192fc79:bf0::/28fc79:bff:ffff:ffff:ffff:ffff:ffff:ffff
193fc79:c00::/28fc79:c0f:ffff:ffff:ffff:ffff:ffff:ffff
194fc79:c10::/28fc79:c1f:ffff:ffff:ffff:ffff:ffff:ffff
195fc79:c20::/28fc79:c2f:ffff:ffff:ffff:ffff:ffff:ffff
196fc79:c30::/28fc79:c3f:ffff:ffff:ffff:ffff:ffff:ffff
197fc79:c40::/28fc79:c4f:ffff:ffff:ffff:ffff:ffff:ffff
198fc79:c50::/28fc79:c5f:ffff:ffff:ffff:ffff:ffff:ffff
199fc79:c60::/28fc79:c6f:ffff:ffff:ffff:ffff:ffff:ffff
200fc79:c70::/28fc79:c7f:ffff:ffff:ffff:ffff:ffff:ffff
201fc79:c80::/28fc79:c8f:ffff:ffff:ffff:ffff:ffff:ffff
202fc79:c90::/28fc79:c9f:ffff:ffff:ffff:ffff:ffff:ffff
203fc79:ca0::/28fc79:caf:ffff:ffff:ffff:ffff:ffff:ffff
204fc79:cb0::/28fc79:cbf:ffff:ffff:ffff:ffff:ffff:ffff
205fc79:cc0::/28fc79:ccf:ffff:ffff:ffff:ffff:ffff:ffff
206fc79:cd0::/28fc79:cdf:ffff:ffff:ffff:ffff:ffff:ffff
207fc79:ce0::/28fc79:cef:ffff:ffff:ffff:ffff:ffff:ffff
208fc79:cf0::/28fc79:cff:ffff:ffff:ffff:ffff:ffff:ffff
209fc79:d00::/28fc79:d0f:ffff:ffff:ffff:ffff:ffff:ffff
210fc79:d10::/28fc79:d1f:ffff:ffff:ffff:ffff:ffff:ffff
211fc79:d20::/28fc79:d2f:ffff:ffff:ffff:ffff:ffff:ffff
212fc79:d30::/28fc79:d3f:ffff:ffff:ffff:ffff:ffff:ffff
213fc79:d40::/28fc79:d4f:ffff:ffff:ffff:ffff:ffff:ffff
214fc79:d50::/28fc79:d5f:ffff:ffff:ffff:ffff:ffff:ffff
215fc79:d60::/28fc79:d6f:ffff:ffff:ffff:ffff:ffff:ffff
216fc79:d70::/28fc79:d7f:ffff:ffff:ffff:ffff:ffff:ffff
217fc79:d80::/28fc79:d8f:ffff:ffff:ffff:ffff:ffff:ffff
218fc79:d90::/28fc79:d9f:ffff:ffff:ffff:ffff:ffff:ffff
219fc79:da0::/28fc79:daf:ffff:ffff:ffff:ffff:ffff:ffff
220fc79:db0::/28fc79:dbf:ffff:ffff:ffff:ffff:ffff:ffff
221fc79:dc0::/28fc79:dcf:ffff:ffff:ffff:ffff:ffff:ffff
222fc79:dd0::/28fc79:ddf:ffff:ffff:ffff:ffff:ffff:ffff
223fc79:de0::/28fc79:def:ffff:ffff:ffff:ffff:ffff:ffff
224fc79:df0::/28fc79:dff:ffff:ffff:ffff:ffff:ffff:ffff
225fc79:e00::/28fc79:e0f:ffff:ffff:ffff:ffff:ffff:ffff
226fc79:e10::/28fc79:e1f:ffff:ffff:ffff:ffff:ffff:ffff
227fc79:e20::/28fc79:e2f:ffff:ffff:ffff:ffff:ffff:ffff
228fc79:e30::/28fc79:e3f:ffff:ffff:ffff:ffff:ffff:ffff
229fc79:e40::/28fc79:e4f:ffff:ffff:ffff:ffff:ffff:ffff
230fc79:e50::/28fc79:e5f:ffff:ffff:ffff:ffff:ffff:ffff
231fc79:e60::/28fc79:e6f:ffff:ffff:ffff:ffff:ffff:ffff
232fc79:e70::/28fc79:e7f:ffff:ffff:ffff:ffff:ffff:ffff
233fc79:e80::/28fc79:e8f:ffff:ffff:ffff:ffff:ffff:ffff
234fc79:e90::/28fc79:e9f:ffff:ffff:ffff:ffff:ffff:ffff
235fc79:ea0::/28fc79:eaf:ffff:ffff:ffff:ffff:ffff:ffff
236fc79:eb0::/28fc79:ebf:ffff:ffff:ffff:ffff:ffff:ffff
237fc79:ec0::/28fc79:ecf:ffff:ffff:ffff:ffff:ffff:ffff
238fc79:ed0::/28fc79:edf:ffff:ffff:ffff:ffff:ffff:ffff
239fc79:ee0::/28fc79:eef:ffff:ffff:ffff:ffff:ffff:ffff
240fc79:ef0::/28fc79:eff:ffff:ffff:ffff:ffff:ffff:ffff
241fc79:f00::/28fc79:f0f:ffff:ffff:ffff:ffff:ffff:ffff
242fc79:f10::/28fc79:f1f:ffff:ffff:ffff:ffff:ffff:ffff
243fc79:f20::/28fc79:f2f:ffff:ffff:ffff:ffff:ffff:ffff
244fc79:f30::/28fc79:f3f:ffff:ffff:ffff:ffff:ffff:ffff
245fc79:f40::/28fc79:f4f:ffff:ffff:ffff:ffff:ffff:ffff
246fc79:f50::/28fc79:f5f:ffff:ffff:ffff:ffff:ffff:ffff
247fc79:f60::/28fc79:f6f:ffff:ffff:ffff:ffff:ffff:ffff
248fc79:f70::/28fc79:f7f:ffff:ffff:ffff:ffff:ffff:ffff
249fc79:f80::/28fc79:f8f:ffff:ffff:ffff:ffff:ffff:ffff
250fc79:f90::/28fc79:f9f:ffff:ffff:ffff:ffff:ffff:ffff
251fc79:fa0::/28fc79:faf:ffff:ffff:ffff:ffff:ffff:ffff
252fc79:fb0::/28fc79:fbf:ffff:ffff:ffff:ffff:ffff:ffff
253fc79:fc0::/28fc79:fcf:ffff:ffff:ffff:ffff:ffff:ffff
254fc79:fd0::/28fc79:fdf:ffff:ffff:ffff:ffff:ffff:ffff
255fc79:fe0::/28fc79:fef:ffff:ffff:ffff:ffff:ffff:ffff
256fc79:ff0::/28fc79: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.