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/20
Addresses2^108
/64 networks2^44
Network
fc6f::/20
First address
fc6f::
Last address
fc6f:fff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
324,518,553,658,426,726,783,156,020,576,256 (2^108)
/64 networks (LANs)
17,592,186,044,416 (2^44)
Full form
fc6f:0000:0000:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zone
0.f.6.c.f.ip6.arpa
Split into smaller subnets/36
/21 (2)/22 (4)/23 (8)/24 (16)/28 (256)/32 (4,096)/36 (65,536)

fc6f::/20 makes 65,536 subnets of /36; the first 256 are listed.

Subnets
#SubnetLast address
1fc6f::/36fc6f:0:fff:ffff:ffff:ffff:ffff:ffff
2fc6f:0:1000::/36fc6f:0:1fff:ffff:ffff:ffff:ffff:ffff
3fc6f:0:2000::/36fc6f:0:2fff:ffff:ffff:ffff:ffff:ffff
4fc6f:0:3000::/36fc6f:0:3fff:ffff:ffff:ffff:ffff:ffff
5fc6f:0:4000::/36fc6f:0:4fff:ffff:ffff:ffff:ffff:ffff
6fc6f:0:5000::/36fc6f:0:5fff:ffff:ffff:ffff:ffff:ffff
7fc6f:0:6000::/36fc6f:0:6fff:ffff:ffff:ffff:ffff:ffff
8fc6f:0:7000::/36fc6f:0:7fff:ffff:ffff:ffff:ffff:ffff
9fc6f:0:8000::/36fc6f:0:8fff:ffff:ffff:ffff:ffff:ffff
10fc6f:0:9000::/36fc6f:0:9fff:ffff:ffff:ffff:ffff:ffff
11fc6f:0:a000::/36fc6f:0:afff:ffff:ffff:ffff:ffff:ffff
12fc6f:0:b000::/36fc6f:0:bfff:ffff:ffff:ffff:ffff:ffff
13fc6f:0:c000::/36fc6f:0:cfff:ffff:ffff:ffff:ffff:ffff
14fc6f:0:d000::/36fc6f:0:dfff:ffff:ffff:ffff:ffff:ffff
15fc6f:0:e000::/36fc6f:0:efff:ffff:ffff:ffff:ffff:ffff
16fc6f:0:f000::/36fc6f:0:ffff:ffff:ffff:ffff:ffff:ffff
17fc6f:1::/36fc6f:1:fff:ffff:ffff:ffff:ffff:ffff
18fc6f:1:1000::/36fc6f:1:1fff:ffff:ffff:ffff:ffff:ffff
19fc6f:1:2000::/36fc6f:1:2fff:ffff:ffff:ffff:ffff:ffff
20fc6f:1:3000::/36fc6f:1:3fff:ffff:ffff:ffff:ffff:ffff
21fc6f:1:4000::/36fc6f:1:4fff:ffff:ffff:ffff:ffff:ffff
22fc6f:1:5000::/36fc6f:1:5fff:ffff:ffff:ffff:ffff:ffff
23fc6f:1:6000::/36fc6f:1:6fff:ffff:ffff:ffff:ffff:ffff
24fc6f:1:7000::/36fc6f:1:7fff:ffff:ffff:ffff:ffff:ffff
25fc6f:1:8000::/36fc6f:1:8fff:ffff:ffff:ffff:ffff:ffff
26fc6f:1:9000::/36fc6f:1:9fff:ffff:ffff:ffff:ffff:ffff
27fc6f:1:a000::/36fc6f:1:afff:ffff:ffff:ffff:ffff:ffff
28fc6f:1:b000::/36fc6f:1:bfff:ffff:ffff:ffff:ffff:ffff
29fc6f:1:c000::/36fc6f:1:cfff:ffff:ffff:ffff:ffff:ffff
30fc6f:1:d000::/36fc6f:1:dfff:ffff:ffff:ffff:ffff:ffff
31fc6f:1:e000::/36fc6f:1:efff:ffff:ffff:ffff:ffff:ffff
32fc6f:1:f000::/36fc6f:1:ffff:ffff:ffff:ffff:ffff:ffff
33fc6f:2::/36fc6f:2:fff:ffff:ffff:ffff:ffff:ffff
34fc6f:2:1000::/36fc6f:2:1fff:ffff:ffff:ffff:ffff:ffff
35fc6f:2:2000::/36fc6f:2:2fff:ffff:ffff:ffff:ffff:ffff
36fc6f:2:3000::/36fc6f:2:3fff:ffff:ffff:ffff:ffff:ffff
37fc6f:2:4000::/36fc6f:2:4fff:ffff:ffff:ffff:ffff:ffff
38fc6f:2:5000::/36fc6f:2:5fff:ffff:ffff:ffff:ffff:ffff
39fc6f:2:6000::/36fc6f:2:6fff:ffff:ffff:ffff:ffff:ffff
40fc6f:2:7000::/36fc6f:2:7fff:ffff:ffff:ffff:ffff:ffff
41fc6f:2:8000::/36fc6f:2:8fff:ffff:ffff:ffff:ffff:ffff
42fc6f:2:9000::/36fc6f:2:9fff:ffff:ffff:ffff:ffff:ffff
43fc6f:2:a000::/36fc6f:2:afff:ffff:ffff:ffff:ffff:ffff
44fc6f:2:b000::/36fc6f:2:bfff:ffff:ffff:ffff:ffff:ffff
45fc6f:2:c000::/36fc6f:2:cfff:ffff:ffff:ffff:ffff:ffff
46fc6f:2:d000::/36fc6f:2:dfff:ffff:ffff:ffff:ffff:ffff
47fc6f:2:e000::/36fc6f:2:efff:ffff:ffff:ffff:ffff:ffff
48fc6f:2:f000::/36fc6f:2:ffff:ffff:ffff:ffff:ffff:ffff
49fc6f:3::/36fc6f:3:fff:ffff:ffff:ffff:ffff:ffff
50fc6f:3:1000::/36fc6f:3:1fff:ffff:ffff:ffff:ffff:ffff
51fc6f:3:2000::/36fc6f:3:2fff:ffff:ffff:ffff:ffff:ffff
52fc6f:3:3000::/36fc6f:3:3fff:ffff:ffff:ffff:ffff:ffff
53fc6f:3:4000::/36fc6f:3:4fff:ffff:ffff:ffff:ffff:ffff
54fc6f:3:5000::/36fc6f:3:5fff:ffff:ffff:ffff:ffff:ffff
55fc6f:3:6000::/36fc6f:3:6fff:ffff:ffff:ffff:ffff:ffff
56fc6f:3:7000::/36fc6f:3:7fff:ffff:ffff:ffff:ffff:ffff
57fc6f:3:8000::/36fc6f:3:8fff:ffff:ffff:ffff:ffff:ffff
58fc6f:3:9000::/36fc6f:3:9fff:ffff:ffff:ffff:ffff:ffff
59fc6f:3:a000::/36fc6f:3:afff:ffff:ffff:ffff:ffff:ffff
60fc6f:3:b000::/36fc6f:3:bfff:ffff:ffff:ffff:ffff:ffff
61fc6f:3:c000::/36fc6f:3:cfff:ffff:ffff:ffff:ffff:ffff
62fc6f:3:d000::/36fc6f:3:dfff:ffff:ffff:ffff:ffff:ffff
63fc6f:3:e000::/36fc6f:3:efff:ffff:ffff:ffff:ffff:ffff
64fc6f:3:f000::/36fc6f:3:ffff:ffff:ffff:ffff:ffff:ffff
65fc6f:4::/36fc6f:4:fff:ffff:ffff:ffff:ffff:ffff
66fc6f:4:1000::/36fc6f:4:1fff:ffff:ffff:ffff:ffff:ffff
67fc6f:4:2000::/36fc6f:4:2fff:ffff:ffff:ffff:ffff:ffff
68fc6f:4:3000::/36fc6f:4:3fff:ffff:ffff:ffff:ffff:ffff
69fc6f:4:4000::/36fc6f:4:4fff:ffff:ffff:ffff:ffff:ffff
70fc6f:4:5000::/36fc6f:4:5fff:ffff:ffff:ffff:ffff:ffff
71fc6f:4:6000::/36fc6f:4:6fff:ffff:ffff:ffff:ffff:ffff
72fc6f:4:7000::/36fc6f:4:7fff:ffff:ffff:ffff:ffff:ffff
73fc6f:4:8000::/36fc6f:4:8fff:ffff:ffff:ffff:ffff:ffff
74fc6f:4:9000::/36fc6f:4:9fff:ffff:ffff:ffff:ffff:ffff
75fc6f:4:a000::/36fc6f:4:afff:ffff:ffff:ffff:ffff:ffff
76fc6f:4:b000::/36fc6f:4:bfff:ffff:ffff:ffff:ffff:ffff
77fc6f:4:c000::/36fc6f:4:cfff:ffff:ffff:ffff:ffff:ffff
78fc6f:4:d000::/36fc6f:4:dfff:ffff:ffff:ffff:ffff:ffff
79fc6f:4:e000::/36fc6f:4:efff:ffff:ffff:ffff:ffff:ffff
80fc6f:4:f000::/36fc6f:4:ffff:ffff:ffff:ffff:ffff:ffff
81fc6f:5::/36fc6f:5:fff:ffff:ffff:ffff:ffff:ffff
82fc6f:5:1000::/36fc6f:5:1fff:ffff:ffff:ffff:ffff:ffff
83fc6f:5:2000::/36fc6f:5:2fff:ffff:ffff:ffff:ffff:ffff
84fc6f:5:3000::/36fc6f:5:3fff:ffff:ffff:ffff:ffff:ffff
85fc6f:5:4000::/36fc6f:5:4fff:ffff:ffff:ffff:ffff:ffff
86fc6f:5:5000::/36fc6f:5:5fff:ffff:ffff:ffff:ffff:ffff
87fc6f:5:6000::/36fc6f:5:6fff:ffff:ffff:ffff:ffff:ffff
88fc6f:5:7000::/36fc6f:5:7fff:ffff:ffff:ffff:ffff:ffff
89fc6f:5:8000::/36fc6f:5:8fff:ffff:ffff:ffff:ffff:ffff
90fc6f:5:9000::/36fc6f:5:9fff:ffff:ffff:ffff:ffff:ffff
91fc6f:5:a000::/36fc6f:5:afff:ffff:ffff:ffff:ffff:ffff
92fc6f:5:b000::/36fc6f:5:bfff:ffff:ffff:ffff:ffff:ffff
93fc6f:5:c000::/36fc6f:5:cfff:ffff:ffff:ffff:ffff:ffff
94fc6f:5:d000::/36fc6f:5:dfff:ffff:ffff:ffff:ffff:ffff
95fc6f:5:e000::/36fc6f:5:efff:ffff:ffff:ffff:ffff:ffff
96fc6f:5:f000::/36fc6f:5:ffff:ffff:ffff:ffff:ffff:ffff
97fc6f:6::/36fc6f:6:fff:ffff:ffff:ffff:ffff:ffff
98fc6f:6:1000::/36fc6f:6:1fff:ffff:ffff:ffff:ffff:ffff
99fc6f:6:2000::/36fc6f:6:2fff:ffff:ffff:ffff:ffff:ffff
100fc6f:6:3000::/36fc6f:6:3fff:ffff:ffff:ffff:ffff:ffff
101fc6f:6:4000::/36fc6f:6:4fff:ffff:ffff:ffff:ffff:ffff
102fc6f:6:5000::/36fc6f:6:5fff:ffff:ffff:ffff:ffff:ffff
103fc6f:6:6000::/36fc6f:6:6fff:ffff:ffff:ffff:ffff:ffff
104fc6f:6:7000::/36fc6f:6:7fff:ffff:ffff:ffff:ffff:ffff
105fc6f:6:8000::/36fc6f:6:8fff:ffff:ffff:ffff:ffff:ffff
106fc6f:6:9000::/36fc6f:6:9fff:ffff:ffff:ffff:ffff:ffff
107fc6f:6:a000::/36fc6f:6:afff:ffff:ffff:ffff:ffff:ffff
108fc6f:6:b000::/36fc6f:6:bfff:ffff:ffff:ffff:ffff:ffff
109fc6f:6:c000::/36fc6f:6:cfff:ffff:ffff:ffff:ffff:ffff
110fc6f:6:d000::/36fc6f:6:dfff:ffff:ffff:ffff:ffff:ffff
111fc6f:6:e000::/36fc6f:6:efff:ffff:ffff:ffff:ffff:ffff
112fc6f:6:f000::/36fc6f:6:ffff:ffff:ffff:ffff:ffff:ffff
113fc6f:7::/36fc6f:7:fff:ffff:ffff:ffff:ffff:ffff
114fc6f:7:1000::/36fc6f:7:1fff:ffff:ffff:ffff:ffff:ffff
115fc6f:7:2000::/36fc6f:7:2fff:ffff:ffff:ffff:ffff:ffff
116fc6f:7:3000::/36fc6f:7:3fff:ffff:ffff:ffff:ffff:ffff
117fc6f:7:4000::/36fc6f:7:4fff:ffff:ffff:ffff:ffff:ffff
118fc6f:7:5000::/36fc6f:7:5fff:ffff:ffff:ffff:ffff:ffff
119fc6f:7:6000::/36fc6f:7:6fff:ffff:ffff:ffff:ffff:ffff
120fc6f:7:7000::/36fc6f:7:7fff:ffff:ffff:ffff:ffff:ffff
121fc6f:7:8000::/36fc6f:7:8fff:ffff:ffff:ffff:ffff:ffff
122fc6f:7:9000::/36fc6f:7:9fff:ffff:ffff:ffff:ffff:ffff
123fc6f:7:a000::/36fc6f:7:afff:ffff:ffff:ffff:ffff:ffff
124fc6f:7:b000::/36fc6f:7:bfff:ffff:ffff:ffff:ffff:ffff
125fc6f:7:c000::/36fc6f:7:cfff:ffff:ffff:ffff:ffff:ffff
126fc6f:7:d000::/36fc6f:7:dfff:ffff:ffff:ffff:ffff:ffff
127fc6f:7:e000::/36fc6f:7:efff:ffff:ffff:ffff:ffff:ffff
128fc6f:7:f000::/36fc6f:7:ffff:ffff:ffff:ffff:ffff:ffff
129fc6f:8::/36fc6f:8:fff:ffff:ffff:ffff:ffff:ffff
130fc6f:8:1000::/36fc6f:8:1fff:ffff:ffff:ffff:ffff:ffff
131fc6f:8:2000::/36fc6f:8:2fff:ffff:ffff:ffff:ffff:ffff
132fc6f:8:3000::/36fc6f:8:3fff:ffff:ffff:ffff:ffff:ffff
133fc6f:8:4000::/36fc6f:8:4fff:ffff:ffff:ffff:ffff:ffff
134fc6f:8:5000::/36fc6f:8:5fff:ffff:ffff:ffff:ffff:ffff
135fc6f:8:6000::/36fc6f:8:6fff:ffff:ffff:ffff:ffff:ffff
136fc6f:8:7000::/36fc6f:8:7fff:ffff:ffff:ffff:ffff:ffff
137fc6f:8:8000::/36fc6f:8:8fff:ffff:ffff:ffff:ffff:ffff
138fc6f:8:9000::/36fc6f:8:9fff:ffff:ffff:ffff:ffff:ffff
139fc6f:8:a000::/36fc6f:8:afff:ffff:ffff:ffff:ffff:ffff
140fc6f:8:b000::/36fc6f:8:bfff:ffff:ffff:ffff:ffff:ffff
141fc6f:8:c000::/36fc6f:8:cfff:ffff:ffff:ffff:ffff:ffff
142fc6f:8:d000::/36fc6f:8:dfff:ffff:ffff:ffff:ffff:ffff
143fc6f:8:e000::/36fc6f:8:efff:ffff:ffff:ffff:ffff:ffff
144fc6f:8:f000::/36fc6f:8:ffff:ffff:ffff:ffff:ffff:ffff
145fc6f:9::/36fc6f:9:fff:ffff:ffff:ffff:ffff:ffff
146fc6f:9:1000::/36fc6f:9:1fff:ffff:ffff:ffff:ffff:ffff
147fc6f:9:2000::/36fc6f:9:2fff:ffff:ffff:ffff:ffff:ffff
148fc6f:9:3000::/36fc6f:9:3fff:ffff:ffff:ffff:ffff:ffff
149fc6f:9:4000::/36fc6f:9:4fff:ffff:ffff:ffff:ffff:ffff
150fc6f:9:5000::/36fc6f:9:5fff:ffff:ffff:ffff:ffff:ffff
151fc6f:9:6000::/36fc6f:9:6fff:ffff:ffff:ffff:ffff:ffff
152fc6f:9:7000::/36fc6f:9:7fff:ffff:ffff:ffff:ffff:ffff
153fc6f:9:8000::/36fc6f:9:8fff:ffff:ffff:ffff:ffff:ffff
154fc6f:9:9000::/36fc6f:9:9fff:ffff:ffff:ffff:ffff:ffff
155fc6f:9:a000::/36fc6f:9:afff:ffff:ffff:ffff:ffff:ffff
156fc6f:9:b000::/36fc6f:9:bfff:ffff:ffff:ffff:ffff:ffff
157fc6f:9:c000::/36fc6f:9:cfff:ffff:ffff:ffff:ffff:ffff
158fc6f:9:d000::/36fc6f:9:dfff:ffff:ffff:ffff:ffff:ffff
159fc6f:9:e000::/36fc6f:9:efff:ffff:ffff:ffff:ffff:ffff
160fc6f:9:f000::/36fc6f:9:ffff:ffff:ffff:ffff:ffff:ffff
161fc6f:a::/36fc6f:a:fff:ffff:ffff:ffff:ffff:ffff
162fc6f:a:1000::/36fc6f:a:1fff:ffff:ffff:ffff:ffff:ffff
163fc6f:a:2000::/36fc6f:a:2fff:ffff:ffff:ffff:ffff:ffff
164fc6f:a:3000::/36fc6f:a:3fff:ffff:ffff:ffff:ffff:ffff
165fc6f:a:4000::/36fc6f:a:4fff:ffff:ffff:ffff:ffff:ffff
166fc6f:a:5000::/36fc6f:a:5fff:ffff:ffff:ffff:ffff:ffff
167fc6f:a:6000::/36fc6f:a:6fff:ffff:ffff:ffff:ffff:ffff
168fc6f:a:7000::/36fc6f:a:7fff:ffff:ffff:ffff:ffff:ffff
169fc6f:a:8000::/36fc6f:a:8fff:ffff:ffff:ffff:ffff:ffff
170fc6f:a:9000::/36fc6f:a:9fff:ffff:ffff:ffff:ffff:ffff
171fc6f:a:a000::/36fc6f:a:afff:ffff:ffff:ffff:ffff:ffff
172fc6f:a:b000::/36fc6f:a:bfff:ffff:ffff:ffff:ffff:ffff
173fc6f:a:c000::/36fc6f:a:cfff:ffff:ffff:ffff:ffff:ffff
174fc6f:a:d000::/36fc6f:a:dfff:ffff:ffff:ffff:ffff:ffff
175fc6f:a:e000::/36fc6f:a:efff:ffff:ffff:ffff:ffff:ffff
176fc6f:a:f000::/36fc6f:a:ffff:ffff:ffff:ffff:ffff:ffff
177fc6f:b::/36fc6f:b:fff:ffff:ffff:ffff:ffff:ffff
178fc6f:b:1000::/36fc6f:b:1fff:ffff:ffff:ffff:ffff:ffff
179fc6f:b:2000::/36fc6f:b:2fff:ffff:ffff:ffff:ffff:ffff
180fc6f:b:3000::/36fc6f:b:3fff:ffff:ffff:ffff:ffff:ffff
181fc6f:b:4000::/36fc6f:b:4fff:ffff:ffff:ffff:ffff:ffff
182fc6f:b:5000::/36fc6f:b:5fff:ffff:ffff:ffff:ffff:ffff
183fc6f:b:6000::/36fc6f:b:6fff:ffff:ffff:ffff:ffff:ffff
184fc6f:b:7000::/36fc6f:b:7fff:ffff:ffff:ffff:ffff:ffff
185fc6f:b:8000::/36fc6f:b:8fff:ffff:ffff:ffff:ffff:ffff
186fc6f:b:9000::/36fc6f:b:9fff:ffff:ffff:ffff:ffff:ffff
187fc6f:b:a000::/36fc6f:b:afff:ffff:ffff:ffff:ffff:ffff
188fc6f:b:b000::/36fc6f:b:bfff:ffff:ffff:ffff:ffff:ffff
189fc6f:b:c000::/36fc6f:b:cfff:ffff:ffff:ffff:ffff:ffff
190fc6f:b:d000::/36fc6f:b:dfff:ffff:ffff:ffff:ffff:ffff
191fc6f:b:e000::/36fc6f:b:efff:ffff:ffff:ffff:ffff:ffff
192fc6f:b:f000::/36fc6f:b:ffff:ffff:ffff:ffff:ffff:ffff
193fc6f:c::/36fc6f:c:fff:ffff:ffff:ffff:ffff:ffff
194fc6f:c:1000::/36fc6f:c:1fff:ffff:ffff:ffff:ffff:ffff
195fc6f:c:2000::/36fc6f:c:2fff:ffff:ffff:ffff:ffff:ffff
196fc6f:c:3000::/36fc6f:c:3fff:ffff:ffff:ffff:ffff:ffff
197fc6f:c:4000::/36fc6f:c:4fff:ffff:ffff:ffff:ffff:ffff
198fc6f:c:5000::/36fc6f:c:5fff:ffff:ffff:ffff:ffff:ffff
199fc6f:c:6000::/36fc6f:c:6fff:ffff:ffff:ffff:ffff:ffff
200fc6f:c:7000::/36fc6f:c:7fff:ffff:ffff:ffff:ffff:ffff
201fc6f:c:8000::/36fc6f:c:8fff:ffff:ffff:ffff:ffff:ffff
202fc6f:c:9000::/36fc6f:c:9fff:ffff:ffff:ffff:ffff:ffff
203fc6f:c:a000::/36fc6f:c:afff:ffff:ffff:ffff:ffff:ffff
204fc6f:c:b000::/36fc6f:c:bfff:ffff:ffff:ffff:ffff:ffff
205fc6f:c:c000::/36fc6f:c:cfff:ffff:ffff:ffff:ffff:ffff
206fc6f:c:d000::/36fc6f:c:dfff:ffff:ffff:ffff:ffff:ffff
207fc6f:c:e000::/36fc6f:c:efff:ffff:ffff:ffff:ffff:ffff
208fc6f:c:f000::/36fc6f:c:ffff:ffff:ffff:ffff:ffff:ffff
209fc6f:d::/36fc6f:d:fff:ffff:ffff:ffff:ffff:ffff
210fc6f:d:1000::/36fc6f:d:1fff:ffff:ffff:ffff:ffff:ffff
211fc6f:d:2000::/36fc6f:d:2fff:ffff:ffff:ffff:ffff:ffff
212fc6f:d:3000::/36fc6f:d:3fff:ffff:ffff:ffff:ffff:ffff
213fc6f:d:4000::/36fc6f:d:4fff:ffff:ffff:ffff:ffff:ffff
214fc6f:d:5000::/36fc6f:d:5fff:ffff:ffff:ffff:ffff:ffff
215fc6f:d:6000::/36fc6f:d:6fff:ffff:ffff:ffff:ffff:ffff
216fc6f:d:7000::/36fc6f:d:7fff:ffff:ffff:ffff:ffff:ffff
217fc6f:d:8000::/36fc6f:d:8fff:ffff:ffff:ffff:ffff:ffff
218fc6f:d:9000::/36fc6f:d:9fff:ffff:ffff:ffff:ffff:ffff
219fc6f:d:a000::/36fc6f:d:afff:ffff:ffff:ffff:ffff:ffff
220fc6f:d:b000::/36fc6f:d:bfff:ffff:ffff:ffff:ffff:ffff
221fc6f:d:c000::/36fc6f:d:cfff:ffff:ffff:ffff:ffff:ffff
222fc6f:d:d000::/36fc6f:d:dfff:ffff:ffff:ffff:ffff:ffff
223fc6f:d:e000::/36fc6f:d:efff:ffff:ffff:ffff:ffff:ffff
224fc6f:d:f000::/36fc6f:d:ffff:ffff:ffff:ffff:ffff:ffff
225fc6f:e::/36fc6f:e:fff:ffff:ffff:ffff:ffff:ffff
226fc6f:e:1000::/36fc6f:e:1fff:ffff:ffff:ffff:ffff:ffff
227fc6f:e:2000::/36fc6f:e:2fff:ffff:ffff:ffff:ffff:ffff
228fc6f:e:3000::/36fc6f:e:3fff:ffff:ffff:ffff:ffff:ffff
229fc6f:e:4000::/36fc6f:e:4fff:ffff:ffff:ffff:ffff:ffff
230fc6f:e:5000::/36fc6f:e:5fff:ffff:ffff:ffff:ffff:ffff
231fc6f:e:6000::/36fc6f:e:6fff:ffff:ffff:ffff:ffff:ffff
232fc6f:e:7000::/36fc6f:e:7fff:ffff:ffff:ffff:ffff:ffff
233fc6f:e:8000::/36fc6f:e:8fff:ffff:ffff:ffff:ffff:ffff
234fc6f:e:9000::/36fc6f:e:9fff:ffff:ffff:ffff:ffff:ffff
235fc6f:e:a000::/36fc6f:e:afff:ffff:ffff:ffff:ffff:ffff
236fc6f:e:b000::/36fc6f:e:bfff:ffff:ffff:ffff:ffff:ffff
237fc6f:e:c000::/36fc6f:e:cfff:ffff:ffff:ffff:ffff:ffff
238fc6f:e:d000::/36fc6f:e:dfff:ffff:ffff:ffff:ffff:ffff
239fc6f:e:e000::/36fc6f:e:efff:ffff:ffff:ffff:ffff:ffff
240fc6f:e:f000::/36fc6f:e:ffff:ffff:ffff:ffff:ffff:ffff
241fc6f:f::/36fc6f:f:fff:ffff:ffff:ffff:ffff:ffff
242fc6f:f:1000::/36fc6f:f:1fff:ffff:ffff:ffff:ffff:ffff
243fc6f:f:2000::/36fc6f:f:2fff:ffff:ffff:ffff:ffff:ffff
244fc6f:f:3000::/36fc6f:f:3fff:ffff:ffff:ffff:ffff:ffff
245fc6f:f:4000::/36fc6f:f:4fff:ffff:ffff:ffff:ffff:ffff
246fc6f:f:5000::/36fc6f:f:5fff:ffff:ffff:ffff:ffff:ffff
247fc6f:f:6000::/36fc6f:f:6fff:ffff:ffff:ffff:ffff:ffff
248fc6f:f:7000::/36fc6f:f:7fff:ffff:ffff:ffff:ffff:ffff
249fc6f:f:8000::/36fc6f:f:8fff:ffff:ffff:ffff:ffff:ffff
250fc6f:f:9000::/36fc6f:f:9fff:ffff:ffff:ffff:ffff:ffff
251fc6f:f:a000::/36fc6f:f:afff:ffff:ffff:ffff:ffff:ffff
252fc6f:f:b000::/36fc6f:f:bfff:ffff:ffff:ffff:ffff:ffff
253fc6f:f:c000::/36fc6f:f:cfff:ffff:ffff:ffff:ffff:ffff
254fc6f:f:d000::/36fc6f:f:dfff:ffff:ffff:ffff:ffff:ffff
255fc6f:f:e000::/36fc6f:f:efff:ffff:ffff:ffff:ffff:ffff
256fc6f:f:f000::/36fc6f:f: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.