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
261d::/16
First address
261d::
Last address
261d: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
261d:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
d.1.6.2.ip6.arpa
Split into smaller subnets/28
/17 (2)/18 (4)/19 (8)/20 (16)/24 (256)/28 (4,096)/32 (65,536)

261d::/16 makes 4,096 subnets of /28; the first 256 are listed.

Subnets
#SubnetLast address
1261d::/28261d:f:ffff:ffff:ffff:ffff:ffff:ffff
2261d:10::/28261d:1f:ffff:ffff:ffff:ffff:ffff:ffff
3261d:20::/28261d:2f:ffff:ffff:ffff:ffff:ffff:ffff
4261d:30::/28261d:3f:ffff:ffff:ffff:ffff:ffff:ffff
5261d:40::/28261d:4f:ffff:ffff:ffff:ffff:ffff:ffff
6261d:50::/28261d:5f:ffff:ffff:ffff:ffff:ffff:ffff
7261d:60::/28261d:6f:ffff:ffff:ffff:ffff:ffff:ffff
8261d:70::/28261d:7f:ffff:ffff:ffff:ffff:ffff:ffff
9261d:80::/28261d:8f:ffff:ffff:ffff:ffff:ffff:ffff
10261d:90::/28261d:9f:ffff:ffff:ffff:ffff:ffff:ffff
11261d:a0::/28261d:af:ffff:ffff:ffff:ffff:ffff:ffff
12261d:b0::/28261d:bf:ffff:ffff:ffff:ffff:ffff:ffff
13261d:c0::/28261d:cf:ffff:ffff:ffff:ffff:ffff:ffff
14261d:d0::/28261d:df:ffff:ffff:ffff:ffff:ffff:ffff
15261d:e0::/28261d:ef:ffff:ffff:ffff:ffff:ffff:ffff
16261d:f0::/28261d:ff:ffff:ffff:ffff:ffff:ffff:ffff
17261d:100::/28261d:10f:ffff:ffff:ffff:ffff:ffff:ffff
18261d:110::/28261d:11f:ffff:ffff:ffff:ffff:ffff:ffff
19261d:120::/28261d:12f:ffff:ffff:ffff:ffff:ffff:ffff
20261d:130::/28261d:13f:ffff:ffff:ffff:ffff:ffff:ffff
21261d:140::/28261d:14f:ffff:ffff:ffff:ffff:ffff:ffff
22261d:150::/28261d:15f:ffff:ffff:ffff:ffff:ffff:ffff
23261d:160::/28261d:16f:ffff:ffff:ffff:ffff:ffff:ffff
24261d:170::/28261d:17f:ffff:ffff:ffff:ffff:ffff:ffff
25261d:180::/28261d:18f:ffff:ffff:ffff:ffff:ffff:ffff
26261d:190::/28261d:19f:ffff:ffff:ffff:ffff:ffff:ffff
27261d:1a0::/28261d:1af:ffff:ffff:ffff:ffff:ffff:ffff
28261d:1b0::/28261d:1bf:ffff:ffff:ffff:ffff:ffff:ffff
29261d:1c0::/28261d:1cf:ffff:ffff:ffff:ffff:ffff:ffff
30261d:1d0::/28261d:1df:ffff:ffff:ffff:ffff:ffff:ffff
31261d:1e0::/28261d:1ef:ffff:ffff:ffff:ffff:ffff:ffff
32261d:1f0::/28261d:1ff:ffff:ffff:ffff:ffff:ffff:ffff
33261d:200::/28261d:20f:ffff:ffff:ffff:ffff:ffff:ffff
34261d:210::/28261d:21f:ffff:ffff:ffff:ffff:ffff:ffff
35261d:220::/28261d:22f:ffff:ffff:ffff:ffff:ffff:ffff
36261d:230::/28261d:23f:ffff:ffff:ffff:ffff:ffff:ffff
37261d:240::/28261d:24f:ffff:ffff:ffff:ffff:ffff:ffff
38261d:250::/28261d:25f:ffff:ffff:ffff:ffff:ffff:ffff
39261d:260::/28261d:26f:ffff:ffff:ffff:ffff:ffff:ffff
40261d:270::/28261d:27f:ffff:ffff:ffff:ffff:ffff:ffff
41261d:280::/28261d:28f:ffff:ffff:ffff:ffff:ffff:ffff
42261d:290::/28261d:29f:ffff:ffff:ffff:ffff:ffff:ffff
43261d:2a0::/28261d:2af:ffff:ffff:ffff:ffff:ffff:ffff
44261d:2b0::/28261d:2bf:ffff:ffff:ffff:ffff:ffff:ffff
45261d:2c0::/28261d:2cf:ffff:ffff:ffff:ffff:ffff:ffff
46261d:2d0::/28261d:2df:ffff:ffff:ffff:ffff:ffff:ffff
47261d:2e0::/28261d:2ef:ffff:ffff:ffff:ffff:ffff:ffff
48261d:2f0::/28261d:2ff:ffff:ffff:ffff:ffff:ffff:ffff
49261d:300::/28261d:30f:ffff:ffff:ffff:ffff:ffff:ffff
50261d:310::/28261d:31f:ffff:ffff:ffff:ffff:ffff:ffff
51261d:320::/28261d:32f:ffff:ffff:ffff:ffff:ffff:ffff
52261d:330::/28261d:33f:ffff:ffff:ffff:ffff:ffff:ffff
53261d:340::/28261d:34f:ffff:ffff:ffff:ffff:ffff:ffff
54261d:350::/28261d:35f:ffff:ffff:ffff:ffff:ffff:ffff
55261d:360::/28261d:36f:ffff:ffff:ffff:ffff:ffff:ffff
56261d:370::/28261d:37f:ffff:ffff:ffff:ffff:ffff:ffff
57261d:380::/28261d:38f:ffff:ffff:ffff:ffff:ffff:ffff
58261d:390::/28261d:39f:ffff:ffff:ffff:ffff:ffff:ffff
59261d:3a0::/28261d:3af:ffff:ffff:ffff:ffff:ffff:ffff
60261d:3b0::/28261d:3bf:ffff:ffff:ffff:ffff:ffff:ffff
61261d:3c0::/28261d:3cf:ffff:ffff:ffff:ffff:ffff:ffff
62261d:3d0::/28261d:3df:ffff:ffff:ffff:ffff:ffff:ffff
63261d:3e0::/28261d:3ef:ffff:ffff:ffff:ffff:ffff:ffff
64261d:3f0::/28261d:3ff:ffff:ffff:ffff:ffff:ffff:ffff
65261d:400::/28261d:40f:ffff:ffff:ffff:ffff:ffff:ffff
66261d:410::/28261d:41f:ffff:ffff:ffff:ffff:ffff:ffff
67261d:420::/28261d:42f:ffff:ffff:ffff:ffff:ffff:ffff
68261d:430::/28261d:43f:ffff:ffff:ffff:ffff:ffff:ffff
69261d:440::/28261d:44f:ffff:ffff:ffff:ffff:ffff:ffff
70261d:450::/28261d:45f:ffff:ffff:ffff:ffff:ffff:ffff
71261d:460::/28261d:46f:ffff:ffff:ffff:ffff:ffff:ffff
72261d:470::/28261d:47f:ffff:ffff:ffff:ffff:ffff:ffff
73261d:480::/28261d:48f:ffff:ffff:ffff:ffff:ffff:ffff
74261d:490::/28261d:49f:ffff:ffff:ffff:ffff:ffff:ffff
75261d:4a0::/28261d:4af:ffff:ffff:ffff:ffff:ffff:ffff
76261d:4b0::/28261d:4bf:ffff:ffff:ffff:ffff:ffff:ffff
77261d:4c0::/28261d:4cf:ffff:ffff:ffff:ffff:ffff:ffff
78261d:4d0::/28261d:4df:ffff:ffff:ffff:ffff:ffff:ffff
79261d:4e0::/28261d:4ef:ffff:ffff:ffff:ffff:ffff:ffff
80261d:4f0::/28261d:4ff:ffff:ffff:ffff:ffff:ffff:ffff
81261d:500::/28261d:50f:ffff:ffff:ffff:ffff:ffff:ffff
82261d:510::/28261d:51f:ffff:ffff:ffff:ffff:ffff:ffff
83261d:520::/28261d:52f:ffff:ffff:ffff:ffff:ffff:ffff
84261d:530::/28261d:53f:ffff:ffff:ffff:ffff:ffff:ffff
85261d:540::/28261d:54f:ffff:ffff:ffff:ffff:ffff:ffff
86261d:550::/28261d:55f:ffff:ffff:ffff:ffff:ffff:ffff
87261d:560::/28261d:56f:ffff:ffff:ffff:ffff:ffff:ffff
88261d:570::/28261d:57f:ffff:ffff:ffff:ffff:ffff:ffff
89261d:580::/28261d:58f:ffff:ffff:ffff:ffff:ffff:ffff
90261d:590::/28261d:59f:ffff:ffff:ffff:ffff:ffff:ffff
91261d:5a0::/28261d:5af:ffff:ffff:ffff:ffff:ffff:ffff
92261d:5b0::/28261d:5bf:ffff:ffff:ffff:ffff:ffff:ffff
93261d:5c0::/28261d:5cf:ffff:ffff:ffff:ffff:ffff:ffff
94261d:5d0::/28261d:5df:ffff:ffff:ffff:ffff:ffff:ffff
95261d:5e0::/28261d:5ef:ffff:ffff:ffff:ffff:ffff:ffff
96261d:5f0::/28261d:5ff:ffff:ffff:ffff:ffff:ffff:ffff
97261d:600::/28261d:60f:ffff:ffff:ffff:ffff:ffff:ffff
98261d:610::/28261d:61f:ffff:ffff:ffff:ffff:ffff:ffff
99261d:620::/28261d:62f:ffff:ffff:ffff:ffff:ffff:ffff
100261d:630::/28261d:63f:ffff:ffff:ffff:ffff:ffff:ffff
101261d:640::/28261d:64f:ffff:ffff:ffff:ffff:ffff:ffff
102261d:650::/28261d:65f:ffff:ffff:ffff:ffff:ffff:ffff
103261d:660::/28261d:66f:ffff:ffff:ffff:ffff:ffff:ffff
104261d:670::/28261d:67f:ffff:ffff:ffff:ffff:ffff:ffff
105261d:680::/28261d:68f:ffff:ffff:ffff:ffff:ffff:ffff
106261d:690::/28261d:69f:ffff:ffff:ffff:ffff:ffff:ffff
107261d:6a0::/28261d:6af:ffff:ffff:ffff:ffff:ffff:ffff
108261d:6b0::/28261d:6bf:ffff:ffff:ffff:ffff:ffff:ffff
109261d:6c0::/28261d:6cf:ffff:ffff:ffff:ffff:ffff:ffff
110261d:6d0::/28261d:6df:ffff:ffff:ffff:ffff:ffff:ffff
111261d:6e0::/28261d:6ef:ffff:ffff:ffff:ffff:ffff:ffff
112261d:6f0::/28261d:6ff:ffff:ffff:ffff:ffff:ffff:ffff
113261d:700::/28261d:70f:ffff:ffff:ffff:ffff:ffff:ffff
114261d:710::/28261d:71f:ffff:ffff:ffff:ffff:ffff:ffff
115261d:720::/28261d:72f:ffff:ffff:ffff:ffff:ffff:ffff
116261d:730::/28261d:73f:ffff:ffff:ffff:ffff:ffff:ffff
117261d:740::/28261d:74f:ffff:ffff:ffff:ffff:ffff:ffff
118261d:750::/28261d:75f:ffff:ffff:ffff:ffff:ffff:ffff
119261d:760::/28261d:76f:ffff:ffff:ffff:ffff:ffff:ffff
120261d:770::/28261d:77f:ffff:ffff:ffff:ffff:ffff:ffff
121261d:780::/28261d:78f:ffff:ffff:ffff:ffff:ffff:ffff
122261d:790::/28261d:79f:ffff:ffff:ffff:ffff:ffff:ffff
123261d:7a0::/28261d:7af:ffff:ffff:ffff:ffff:ffff:ffff
124261d:7b0::/28261d:7bf:ffff:ffff:ffff:ffff:ffff:ffff
125261d:7c0::/28261d:7cf:ffff:ffff:ffff:ffff:ffff:ffff
126261d:7d0::/28261d:7df:ffff:ffff:ffff:ffff:ffff:ffff
127261d:7e0::/28261d:7ef:ffff:ffff:ffff:ffff:ffff:ffff
128261d:7f0::/28261d:7ff:ffff:ffff:ffff:ffff:ffff:ffff
129261d:800::/28261d:80f:ffff:ffff:ffff:ffff:ffff:ffff
130261d:810::/28261d:81f:ffff:ffff:ffff:ffff:ffff:ffff
131261d:820::/28261d:82f:ffff:ffff:ffff:ffff:ffff:ffff
132261d:830::/28261d:83f:ffff:ffff:ffff:ffff:ffff:ffff
133261d:840::/28261d:84f:ffff:ffff:ffff:ffff:ffff:ffff
134261d:850::/28261d:85f:ffff:ffff:ffff:ffff:ffff:ffff
135261d:860::/28261d:86f:ffff:ffff:ffff:ffff:ffff:ffff
136261d:870::/28261d:87f:ffff:ffff:ffff:ffff:ffff:ffff
137261d:880::/28261d:88f:ffff:ffff:ffff:ffff:ffff:ffff
138261d:890::/28261d:89f:ffff:ffff:ffff:ffff:ffff:ffff
139261d:8a0::/28261d:8af:ffff:ffff:ffff:ffff:ffff:ffff
140261d:8b0::/28261d:8bf:ffff:ffff:ffff:ffff:ffff:ffff
141261d:8c0::/28261d:8cf:ffff:ffff:ffff:ffff:ffff:ffff
142261d:8d0::/28261d:8df:ffff:ffff:ffff:ffff:ffff:ffff
143261d:8e0::/28261d:8ef:ffff:ffff:ffff:ffff:ffff:ffff
144261d:8f0::/28261d:8ff:ffff:ffff:ffff:ffff:ffff:ffff
145261d:900::/28261d:90f:ffff:ffff:ffff:ffff:ffff:ffff
146261d:910::/28261d:91f:ffff:ffff:ffff:ffff:ffff:ffff
147261d:920::/28261d:92f:ffff:ffff:ffff:ffff:ffff:ffff
148261d:930::/28261d:93f:ffff:ffff:ffff:ffff:ffff:ffff
149261d:940::/28261d:94f:ffff:ffff:ffff:ffff:ffff:ffff
150261d:950::/28261d:95f:ffff:ffff:ffff:ffff:ffff:ffff
151261d:960::/28261d:96f:ffff:ffff:ffff:ffff:ffff:ffff
152261d:970::/28261d:97f:ffff:ffff:ffff:ffff:ffff:ffff
153261d:980::/28261d:98f:ffff:ffff:ffff:ffff:ffff:ffff
154261d:990::/28261d:99f:ffff:ffff:ffff:ffff:ffff:ffff
155261d:9a0::/28261d:9af:ffff:ffff:ffff:ffff:ffff:ffff
156261d:9b0::/28261d:9bf:ffff:ffff:ffff:ffff:ffff:ffff
157261d:9c0::/28261d:9cf:ffff:ffff:ffff:ffff:ffff:ffff
158261d:9d0::/28261d:9df:ffff:ffff:ffff:ffff:ffff:ffff
159261d:9e0::/28261d:9ef:ffff:ffff:ffff:ffff:ffff:ffff
160261d:9f0::/28261d:9ff:ffff:ffff:ffff:ffff:ffff:ffff
161261d:a00::/28261d:a0f:ffff:ffff:ffff:ffff:ffff:ffff
162261d:a10::/28261d:a1f:ffff:ffff:ffff:ffff:ffff:ffff
163261d:a20::/28261d:a2f:ffff:ffff:ffff:ffff:ffff:ffff
164261d:a30::/28261d:a3f:ffff:ffff:ffff:ffff:ffff:ffff
165261d:a40::/28261d:a4f:ffff:ffff:ffff:ffff:ffff:ffff
166261d:a50::/28261d:a5f:ffff:ffff:ffff:ffff:ffff:ffff
167261d:a60::/28261d:a6f:ffff:ffff:ffff:ffff:ffff:ffff
168261d:a70::/28261d:a7f:ffff:ffff:ffff:ffff:ffff:ffff
169261d:a80::/28261d:a8f:ffff:ffff:ffff:ffff:ffff:ffff
170261d:a90::/28261d:a9f:ffff:ffff:ffff:ffff:ffff:ffff
171261d:aa0::/28261d:aaf:ffff:ffff:ffff:ffff:ffff:ffff
172261d:ab0::/28261d:abf:ffff:ffff:ffff:ffff:ffff:ffff
173261d:ac0::/28261d:acf:ffff:ffff:ffff:ffff:ffff:ffff
174261d:ad0::/28261d:adf:ffff:ffff:ffff:ffff:ffff:ffff
175261d:ae0::/28261d:aef:ffff:ffff:ffff:ffff:ffff:ffff
176261d:af0::/28261d:aff:ffff:ffff:ffff:ffff:ffff:ffff
177261d:b00::/28261d:b0f:ffff:ffff:ffff:ffff:ffff:ffff
178261d:b10::/28261d:b1f:ffff:ffff:ffff:ffff:ffff:ffff
179261d:b20::/28261d:b2f:ffff:ffff:ffff:ffff:ffff:ffff
180261d:b30::/28261d:b3f:ffff:ffff:ffff:ffff:ffff:ffff
181261d:b40::/28261d:b4f:ffff:ffff:ffff:ffff:ffff:ffff
182261d:b50::/28261d:b5f:ffff:ffff:ffff:ffff:ffff:ffff
183261d:b60::/28261d:b6f:ffff:ffff:ffff:ffff:ffff:ffff
184261d:b70::/28261d:b7f:ffff:ffff:ffff:ffff:ffff:ffff
185261d:b80::/28261d:b8f:ffff:ffff:ffff:ffff:ffff:ffff
186261d:b90::/28261d:b9f:ffff:ffff:ffff:ffff:ffff:ffff
187261d:ba0::/28261d:baf:ffff:ffff:ffff:ffff:ffff:ffff
188261d:bb0::/28261d:bbf:ffff:ffff:ffff:ffff:ffff:ffff
189261d:bc0::/28261d:bcf:ffff:ffff:ffff:ffff:ffff:ffff
190261d:bd0::/28261d:bdf:ffff:ffff:ffff:ffff:ffff:ffff
191261d:be0::/28261d:bef:ffff:ffff:ffff:ffff:ffff:ffff
192261d:bf0::/28261d:bff:ffff:ffff:ffff:ffff:ffff:ffff
193261d:c00::/28261d:c0f:ffff:ffff:ffff:ffff:ffff:ffff
194261d:c10::/28261d:c1f:ffff:ffff:ffff:ffff:ffff:ffff
195261d:c20::/28261d:c2f:ffff:ffff:ffff:ffff:ffff:ffff
196261d:c30::/28261d:c3f:ffff:ffff:ffff:ffff:ffff:ffff
197261d:c40::/28261d:c4f:ffff:ffff:ffff:ffff:ffff:ffff
198261d:c50::/28261d:c5f:ffff:ffff:ffff:ffff:ffff:ffff
199261d:c60::/28261d:c6f:ffff:ffff:ffff:ffff:ffff:ffff
200261d:c70::/28261d:c7f:ffff:ffff:ffff:ffff:ffff:ffff
201261d:c80::/28261d:c8f:ffff:ffff:ffff:ffff:ffff:ffff
202261d:c90::/28261d:c9f:ffff:ffff:ffff:ffff:ffff:ffff
203261d:ca0::/28261d:caf:ffff:ffff:ffff:ffff:ffff:ffff
204261d:cb0::/28261d:cbf:ffff:ffff:ffff:ffff:ffff:ffff
205261d:cc0::/28261d:ccf:ffff:ffff:ffff:ffff:ffff:ffff
206261d:cd0::/28261d:cdf:ffff:ffff:ffff:ffff:ffff:ffff
207261d:ce0::/28261d:cef:ffff:ffff:ffff:ffff:ffff:ffff
208261d:cf0::/28261d:cff:ffff:ffff:ffff:ffff:ffff:ffff
209261d:d00::/28261d:d0f:ffff:ffff:ffff:ffff:ffff:ffff
210261d:d10::/28261d:d1f:ffff:ffff:ffff:ffff:ffff:ffff
211261d:d20::/28261d:d2f:ffff:ffff:ffff:ffff:ffff:ffff
212261d:d30::/28261d:d3f:ffff:ffff:ffff:ffff:ffff:ffff
213261d:d40::/28261d:d4f:ffff:ffff:ffff:ffff:ffff:ffff
214261d:d50::/28261d:d5f:ffff:ffff:ffff:ffff:ffff:ffff
215261d:d60::/28261d:d6f:ffff:ffff:ffff:ffff:ffff:ffff
216261d:d70::/28261d:d7f:ffff:ffff:ffff:ffff:ffff:ffff
217261d:d80::/28261d:d8f:ffff:ffff:ffff:ffff:ffff:ffff
218261d:d90::/28261d:d9f:ffff:ffff:ffff:ffff:ffff:ffff
219261d:da0::/28261d:daf:ffff:ffff:ffff:ffff:ffff:ffff
220261d:db0::/28261d:dbf:ffff:ffff:ffff:ffff:ffff:ffff
221261d:dc0::/28261d:dcf:ffff:ffff:ffff:ffff:ffff:ffff
222261d:dd0::/28261d:ddf:ffff:ffff:ffff:ffff:ffff:ffff
223261d:de0::/28261d:def:ffff:ffff:ffff:ffff:ffff:ffff
224261d:df0::/28261d:dff:ffff:ffff:ffff:ffff:ffff:ffff
225261d:e00::/28261d:e0f:ffff:ffff:ffff:ffff:ffff:ffff
226261d:e10::/28261d:e1f:ffff:ffff:ffff:ffff:ffff:ffff
227261d:e20::/28261d:e2f:ffff:ffff:ffff:ffff:ffff:ffff
228261d:e30::/28261d:e3f:ffff:ffff:ffff:ffff:ffff:ffff
229261d:e40::/28261d:e4f:ffff:ffff:ffff:ffff:ffff:ffff
230261d:e50::/28261d:e5f:ffff:ffff:ffff:ffff:ffff:ffff
231261d:e60::/28261d:e6f:ffff:ffff:ffff:ffff:ffff:ffff
232261d:e70::/28261d:e7f:ffff:ffff:ffff:ffff:ffff:ffff
233261d:e80::/28261d:e8f:ffff:ffff:ffff:ffff:ffff:ffff
234261d:e90::/28261d:e9f:ffff:ffff:ffff:ffff:ffff:ffff
235261d:ea0::/28261d:eaf:ffff:ffff:ffff:ffff:ffff:ffff
236261d:eb0::/28261d:ebf:ffff:ffff:ffff:ffff:ffff:ffff
237261d:ec0::/28261d:ecf:ffff:ffff:ffff:ffff:ffff:ffff
238261d:ed0::/28261d:edf:ffff:ffff:ffff:ffff:ffff:ffff
239261d:ee0::/28261d:eef:ffff:ffff:ffff:ffff:ffff:ffff
240261d:ef0::/28261d:eff:ffff:ffff:ffff:ffff:ffff:ffff
241261d:f00::/28261d:f0f:ffff:ffff:ffff:ffff:ffff:ffff
242261d:f10::/28261d:f1f:ffff:ffff:ffff:ffff:ffff:ffff
243261d:f20::/28261d:f2f:ffff:ffff:ffff:ffff:ffff:ffff
244261d:f30::/28261d:f3f:ffff:ffff:ffff:ffff:ffff:ffff
245261d:f40::/28261d:f4f:ffff:ffff:ffff:ffff:ffff:ffff
246261d:f50::/28261d:f5f:ffff:ffff:ffff:ffff:ffff:ffff
247261d:f60::/28261d:f6f:ffff:ffff:ffff:ffff:ffff:ffff
248261d:f70::/28261d:f7f:ffff:ffff:ffff:ffff:ffff:ffff
249261d:f80::/28261d:f8f:ffff:ffff:ffff:ffff:ffff:ffff
250261d:f90::/28261d:f9f:ffff:ffff:ffff:ffff:ffff:ffff
251261d:fa0::/28261d:faf:ffff:ffff:ffff:ffff:ffff:ffff
252261d:fb0::/28261d:fbf:ffff:ffff:ffff:ffff:ffff:ffff
253261d:fc0::/28261d:fcf:ffff:ffff:ffff:ffff:ffff:ffff
254261d:fd0::/28261d:fdf:ffff:ffff:ffff:ffff:ffff:ffff
255261d:fe0::/28261d:fef:ffff:ffff:ffff:ffff:ffff:ffff
256261d:ff0::/28261d: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.