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/40
Addresses2^88
/64 networks16,777,216
Network
fc3f:dd:ec00::/40
First address
fc3f:dd:ec00::
Last address
fc3f:dd:ecff:ffff:ffff:ffff:ffff:ffff
Addresses
309,485,009,821,345,068,724,781,056 (2^88)
/64 networks (LANs)
16,777,216
Full form
fc3f:00dd:ec00:0000:0000:0000:0000:0000
Type
Unique local (ULA) fc00::/7
Private IPv6, like RFC 1918; usually fd00::/8
Reverse DNS zone
c.e.d.d.0.0.f.3.c.f.ip6.arpa
Split into smaller subnets/52
/41 (2)/42 (4)/43 (8)/44 (16)/48 (256)/52 (4,096)/56 (65,536)

fc3f:dd:ec00::/40 makes 4,096 subnets of /52; the first 256 are listed.

Subnets
#SubnetLast address
1fc3f:dd:ec00::/52fc3f:dd:ec00:fff:ffff:ffff:ffff:ffff
2fc3f:dd:ec00:1000::/52fc3f:dd:ec00:1fff:ffff:ffff:ffff:ffff
3fc3f:dd:ec00:2000::/52fc3f:dd:ec00:2fff:ffff:ffff:ffff:ffff
4fc3f:dd:ec00:3000::/52fc3f:dd:ec00:3fff:ffff:ffff:ffff:ffff
5fc3f:dd:ec00:4000::/52fc3f:dd:ec00:4fff:ffff:ffff:ffff:ffff
6fc3f:dd:ec00:5000::/52fc3f:dd:ec00:5fff:ffff:ffff:ffff:ffff
7fc3f:dd:ec00:6000::/52fc3f:dd:ec00:6fff:ffff:ffff:ffff:ffff
8fc3f:dd:ec00:7000::/52fc3f:dd:ec00:7fff:ffff:ffff:ffff:ffff
9fc3f:dd:ec00:8000::/52fc3f:dd:ec00:8fff:ffff:ffff:ffff:ffff
10fc3f:dd:ec00:9000::/52fc3f:dd:ec00:9fff:ffff:ffff:ffff:ffff
11fc3f:dd:ec00:a000::/52fc3f:dd:ec00:afff:ffff:ffff:ffff:ffff
12fc3f:dd:ec00:b000::/52fc3f:dd:ec00:bfff:ffff:ffff:ffff:ffff
13fc3f:dd:ec00:c000::/52fc3f:dd:ec00:cfff:ffff:ffff:ffff:ffff
14fc3f:dd:ec00:d000::/52fc3f:dd:ec00:dfff:ffff:ffff:ffff:ffff
15fc3f:dd:ec00:e000::/52fc3f:dd:ec00:efff:ffff:ffff:ffff:ffff
16fc3f:dd:ec00:f000::/52fc3f:dd:ec00:ffff:ffff:ffff:ffff:ffff
17fc3f:dd:ec01::/52fc3f:dd:ec01:fff:ffff:ffff:ffff:ffff
18fc3f:dd:ec01:1000::/52fc3f:dd:ec01:1fff:ffff:ffff:ffff:ffff
19fc3f:dd:ec01:2000::/52fc3f:dd:ec01:2fff:ffff:ffff:ffff:ffff
20fc3f:dd:ec01:3000::/52fc3f:dd:ec01:3fff:ffff:ffff:ffff:ffff
21fc3f:dd:ec01:4000::/52fc3f:dd:ec01:4fff:ffff:ffff:ffff:ffff
22fc3f:dd:ec01:5000::/52fc3f:dd:ec01:5fff:ffff:ffff:ffff:ffff
23fc3f:dd:ec01:6000::/52fc3f:dd:ec01:6fff:ffff:ffff:ffff:ffff
24fc3f:dd:ec01:7000::/52fc3f:dd:ec01:7fff:ffff:ffff:ffff:ffff
25fc3f:dd:ec01:8000::/52fc3f:dd:ec01:8fff:ffff:ffff:ffff:ffff
26fc3f:dd:ec01:9000::/52fc3f:dd:ec01:9fff:ffff:ffff:ffff:ffff
27fc3f:dd:ec01:a000::/52fc3f:dd:ec01:afff:ffff:ffff:ffff:ffff
28fc3f:dd:ec01:b000::/52fc3f:dd:ec01:bfff:ffff:ffff:ffff:ffff
29fc3f:dd:ec01:c000::/52fc3f:dd:ec01:cfff:ffff:ffff:ffff:ffff
30fc3f:dd:ec01:d000::/52fc3f:dd:ec01:dfff:ffff:ffff:ffff:ffff
31fc3f:dd:ec01:e000::/52fc3f:dd:ec01:efff:ffff:ffff:ffff:ffff
32fc3f:dd:ec01:f000::/52fc3f:dd:ec01:ffff:ffff:ffff:ffff:ffff
33fc3f:dd:ec02::/52fc3f:dd:ec02:fff:ffff:ffff:ffff:ffff
34fc3f:dd:ec02:1000::/52fc3f:dd:ec02:1fff:ffff:ffff:ffff:ffff
35fc3f:dd:ec02:2000::/52fc3f:dd:ec02:2fff:ffff:ffff:ffff:ffff
36fc3f:dd:ec02:3000::/52fc3f:dd:ec02:3fff:ffff:ffff:ffff:ffff
37fc3f:dd:ec02:4000::/52fc3f:dd:ec02:4fff:ffff:ffff:ffff:ffff
38fc3f:dd:ec02:5000::/52fc3f:dd:ec02:5fff:ffff:ffff:ffff:ffff
39fc3f:dd:ec02:6000::/52fc3f:dd:ec02:6fff:ffff:ffff:ffff:ffff
40fc3f:dd:ec02:7000::/52fc3f:dd:ec02:7fff:ffff:ffff:ffff:ffff
41fc3f:dd:ec02:8000::/52fc3f:dd:ec02:8fff:ffff:ffff:ffff:ffff
42fc3f:dd:ec02:9000::/52fc3f:dd:ec02:9fff:ffff:ffff:ffff:ffff
43fc3f:dd:ec02:a000::/52fc3f:dd:ec02:afff:ffff:ffff:ffff:ffff
44fc3f:dd:ec02:b000::/52fc3f:dd:ec02:bfff:ffff:ffff:ffff:ffff
45fc3f:dd:ec02:c000::/52fc3f:dd:ec02:cfff:ffff:ffff:ffff:ffff
46fc3f:dd:ec02:d000::/52fc3f:dd:ec02:dfff:ffff:ffff:ffff:ffff
47fc3f:dd:ec02:e000::/52fc3f:dd:ec02:efff:ffff:ffff:ffff:ffff
48fc3f:dd:ec02:f000::/52fc3f:dd:ec02:ffff:ffff:ffff:ffff:ffff
49fc3f:dd:ec03::/52fc3f:dd:ec03:fff:ffff:ffff:ffff:ffff
50fc3f:dd:ec03:1000::/52fc3f:dd:ec03:1fff:ffff:ffff:ffff:ffff
51fc3f:dd:ec03:2000::/52fc3f:dd:ec03:2fff:ffff:ffff:ffff:ffff
52fc3f:dd:ec03:3000::/52fc3f:dd:ec03:3fff:ffff:ffff:ffff:ffff
53fc3f:dd:ec03:4000::/52fc3f:dd:ec03:4fff:ffff:ffff:ffff:ffff
54fc3f:dd:ec03:5000::/52fc3f:dd:ec03:5fff:ffff:ffff:ffff:ffff
55fc3f:dd:ec03:6000::/52fc3f:dd:ec03:6fff:ffff:ffff:ffff:ffff
56fc3f:dd:ec03:7000::/52fc3f:dd:ec03:7fff:ffff:ffff:ffff:ffff
57fc3f:dd:ec03:8000::/52fc3f:dd:ec03:8fff:ffff:ffff:ffff:ffff
58fc3f:dd:ec03:9000::/52fc3f:dd:ec03:9fff:ffff:ffff:ffff:ffff
59fc3f:dd:ec03:a000::/52fc3f:dd:ec03:afff:ffff:ffff:ffff:ffff
60fc3f:dd:ec03:b000::/52fc3f:dd:ec03:bfff:ffff:ffff:ffff:ffff
61fc3f:dd:ec03:c000::/52fc3f:dd:ec03:cfff:ffff:ffff:ffff:ffff
62fc3f:dd:ec03:d000::/52fc3f:dd:ec03:dfff:ffff:ffff:ffff:ffff
63fc3f:dd:ec03:e000::/52fc3f:dd:ec03:efff:ffff:ffff:ffff:ffff
64fc3f:dd:ec03:f000::/52fc3f:dd:ec03:ffff:ffff:ffff:ffff:ffff
65fc3f:dd:ec04::/52fc3f:dd:ec04:fff:ffff:ffff:ffff:ffff
66fc3f:dd:ec04:1000::/52fc3f:dd:ec04:1fff:ffff:ffff:ffff:ffff
67fc3f:dd:ec04:2000::/52fc3f:dd:ec04:2fff:ffff:ffff:ffff:ffff
68fc3f:dd:ec04:3000::/52fc3f:dd:ec04:3fff:ffff:ffff:ffff:ffff
69fc3f:dd:ec04:4000::/52fc3f:dd:ec04:4fff:ffff:ffff:ffff:ffff
70fc3f:dd:ec04:5000::/52fc3f:dd:ec04:5fff:ffff:ffff:ffff:ffff
71fc3f:dd:ec04:6000::/52fc3f:dd:ec04:6fff:ffff:ffff:ffff:ffff
72fc3f:dd:ec04:7000::/52fc3f:dd:ec04:7fff:ffff:ffff:ffff:ffff
73fc3f:dd:ec04:8000::/52fc3f:dd:ec04:8fff:ffff:ffff:ffff:ffff
74fc3f:dd:ec04:9000::/52fc3f:dd:ec04:9fff:ffff:ffff:ffff:ffff
75fc3f:dd:ec04:a000::/52fc3f:dd:ec04:afff:ffff:ffff:ffff:ffff
76fc3f:dd:ec04:b000::/52fc3f:dd:ec04:bfff:ffff:ffff:ffff:ffff
77fc3f:dd:ec04:c000::/52fc3f:dd:ec04:cfff:ffff:ffff:ffff:ffff
78fc3f:dd:ec04:d000::/52fc3f:dd:ec04:dfff:ffff:ffff:ffff:ffff
79fc3f:dd:ec04:e000::/52fc3f:dd:ec04:efff:ffff:ffff:ffff:ffff
80fc3f:dd:ec04:f000::/52fc3f:dd:ec04:ffff:ffff:ffff:ffff:ffff
81fc3f:dd:ec05::/52fc3f:dd:ec05:fff:ffff:ffff:ffff:ffff
82fc3f:dd:ec05:1000::/52fc3f:dd:ec05:1fff:ffff:ffff:ffff:ffff
83fc3f:dd:ec05:2000::/52fc3f:dd:ec05:2fff:ffff:ffff:ffff:ffff
84fc3f:dd:ec05:3000::/52fc3f:dd:ec05:3fff:ffff:ffff:ffff:ffff
85fc3f:dd:ec05:4000::/52fc3f:dd:ec05:4fff:ffff:ffff:ffff:ffff
86fc3f:dd:ec05:5000::/52fc3f:dd:ec05:5fff:ffff:ffff:ffff:ffff
87fc3f:dd:ec05:6000::/52fc3f:dd:ec05:6fff:ffff:ffff:ffff:ffff
88fc3f:dd:ec05:7000::/52fc3f:dd:ec05:7fff:ffff:ffff:ffff:ffff
89fc3f:dd:ec05:8000::/52fc3f:dd:ec05:8fff:ffff:ffff:ffff:ffff
90fc3f:dd:ec05:9000::/52fc3f:dd:ec05:9fff:ffff:ffff:ffff:ffff
91fc3f:dd:ec05:a000::/52fc3f:dd:ec05:afff:ffff:ffff:ffff:ffff
92fc3f:dd:ec05:b000::/52fc3f:dd:ec05:bfff:ffff:ffff:ffff:ffff
93fc3f:dd:ec05:c000::/52fc3f:dd:ec05:cfff:ffff:ffff:ffff:ffff
94fc3f:dd:ec05:d000::/52fc3f:dd:ec05:dfff:ffff:ffff:ffff:ffff
95fc3f:dd:ec05:e000::/52fc3f:dd:ec05:efff:ffff:ffff:ffff:ffff
96fc3f:dd:ec05:f000::/52fc3f:dd:ec05:ffff:ffff:ffff:ffff:ffff
97fc3f:dd:ec06::/52fc3f:dd:ec06:fff:ffff:ffff:ffff:ffff
98fc3f:dd:ec06:1000::/52fc3f:dd:ec06:1fff:ffff:ffff:ffff:ffff
99fc3f:dd:ec06:2000::/52fc3f:dd:ec06:2fff:ffff:ffff:ffff:ffff
100fc3f:dd:ec06:3000::/52fc3f:dd:ec06:3fff:ffff:ffff:ffff:ffff
101fc3f:dd:ec06:4000::/52fc3f:dd:ec06:4fff:ffff:ffff:ffff:ffff
102fc3f:dd:ec06:5000::/52fc3f:dd:ec06:5fff:ffff:ffff:ffff:ffff
103fc3f:dd:ec06:6000::/52fc3f:dd:ec06:6fff:ffff:ffff:ffff:ffff
104fc3f:dd:ec06:7000::/52fc3f:dd:ec06:7fff:ffff:ffff:ffff:ffff
105fc3f:dd:ec06:8000::/52fc3f:dd:ec06:8fff:ffff:ffff:ffff:ffff
106fc3f:dd:ec06:9000::/52fc3f:dd:ec06:9fff:ffff:ffff:ffff:ffff
107fc3f:dd:ec06:a000::/52fc3f:dd:ec06:afff:ffff:ffff:ffff:ffff
108fc3f:dd:ec06:b000::/52fc3f:dd:ec06:bfff:ffff:ffff:ffff:ffff
109fc3f:dd:ec06:c000::/52fc3f:dd:ec06:cfff:ffff:ffff:ffff:ffff
110fc3f:dd:ec06:d000::/52fc3f:dd:ec06:dfff:ffff:ffff:ffff:ffff
111fc3f:dd:ec06:e000::/52fc3f:dd:ec06:efff:ffff:ffff:ffff:ffff
112fc3f:dd:ec06:f000::/52fc3f:dd:ec06:ffff:ffff:ffff:ffff:ffff
113fc3f:dd:ec07::/52fc3f:dd:ec07:fff:ffff:ffff:ffff:ffff
114fc3f:dd:ec07:1000::/52fc3f:dd:ec07:1fff:ffff:ffff:ffff:ffff
115fc3f:dd:ec07:2000::/52fc3f:dd:ec07:2fff:ffff:ffff:ffff:ffff
116fc3f:dd:ec07:3000::/52fc3f:dd:ec07:3fff:ffff:ffff:ffff:ffff
117fc3f:dd:ec07:4000::/52fc3f:dd:ec07:4fff:ffff:ffff:ffff:ffff
118fc3f:dd:ec07:5000::/52fc3f:dd:ec07:5fff:ffff:ffff:ffff:ffff
119fc3f:dd:ec07:6000::/52fc3f:dd:ec07:6fff:ffff:ffff:ffff:ffff
120fc3f:dd:ec07:7000::/52fc3f:dd:ec07:7fff:ffff:ffff:ffff:ffff
121fc3f:dd:ec07:8000::/52fc3f:dd:ec07:8fff:ffff:ffff:ffff:ffff
122fc3f:dd:ec07:9000::/52fc3f:dd:ec07:9fff:ffff:ffff:ffff:ffff
123fc3f:dd:ec07:a000::/52fc3f:dd:ec07:afff:ffff:ffff:ffff:ffff
124fc3f:dd:ec07:b000::/52fc3f:dd:ec07:bfff:ffff:ffff:ffff:ffff
125fc3f:dd:ec07:c000::/52fc3f:dd:ec07:cfff:ffff:ffff:ffff:ffff
126fc3f:dd:ec07:d000::/52fc3f:dd:ec07:dfff:ffff:ffff:ffff:ffff
127fc3f:dd:ec07:e000::/52fc3f:dd:ec07:efff:ffff:ffff:ffff:ffff
128fc3f:dd:ec07:f000::/52fc3f:dd:ec07:ffff:ffff:ffff:ffff:ffff
129fc3f:dd:ec08::/52fc3f:dd:ec08:fff:ffff:ffff:ffff:ffff
130fc3f:dd:ec08:1000::/52fc3f:dd:ec08:1fff:ffff:ffff:ffff:ffff
131fc3f:dd:ec08:2000::/52fc3f:dd:ec08:2fff:ffff:ffff:ffff:ffff
132fc3f:dd:ec08:3000::/52fc3f:dd:ec08:3fff:ffff:ffff:ffff:ffff
133fc3f:dd:ec08:4000::/52fc3f:dd:ec08:4fff:ffff:ffff:ffff:ffff
134fc3f:dd:ec08:5000::/52fc3f:dd:ec08:5fff:ffff:ffff:ffff:ffff
135fc3f:dd:ec08:6000::/52fc3f:dd:ec08:6fff:ffff:ffff:ffff:ffff
136fc3f:dd:ec08:7000::/52fc3f:dd:ec08:7fff:ffff:ffff:ffff:ffff
137fc3f:dd:ec08:8000::/52fc3f:dd:ec08:8fff:ffff:ffff:ffff:ffff
138fc3f:dd:ec08:9000::/52fc3f:dd:ec08:9fff:ffff:ffff:ffff:ffff
139fc3f:dd:ec08:a000::/52fc3f:dd:ec08:afff:ffff:ffff:ffff:ffff
140fc3f:dd:ec08:b000::/52fc3f:dd:ec08:bfff:ffff:ffff:ffff:ffff
141fc3f:dd:ec08:c000::/52fc3f:dd:ec08:cfff:ffff:ffff:ffff:ffff
142fc3f:dd:ec08:d000::/52fc3f:dd:ec08:dfff:ffff:ffff:ffff:ffff
143fc3f:dd:ec08:e000::/52fc3f:dd:ec08:efff:ffff:ffff:ffff:ffff
144fc3f:dd:ec08:f000::/52fc3f:dd:ec08:ffff:ffff:ffff:ffff:ffff
145fc3f:dd:ec09::/52fc3f:dd:ec09:fff:ffff:ffff:ffff:ffff
146fc3f:dd:ec09:1000::/52fc3f:dd:ec09:1fff:ffff:ffff:ffff:ffff
147fc3f:dd:ec09:2000::/52fc3f:dd:ec09:2fff:ffff:ffff:ffff:ffff
148fc3f:dd:ec09:3000::/52fc3f:dd:ec09:3fff:ffff:ffff:ffff:ffff
149fc3f:dd:ec09:4000::/52fc3f:dd:ec09:4fff:ffff:ffff:ffff:ffff
150fc3f:dd:ec09:5000::/52fc3f:dd:ec09:5fff:ffff:ffff:ffff:ffff
151fc3f:dd:ec09:6000::/52fc3f:dd:ec09:6fff:ffff:ffff:ffff:ffff
152fc3f:dd:ec09:7000::/52fc3f:dd:ec09:7fff:ffff:ffff:ffff:ffff
153fc3f:dd:ec09:8000::/52fc3f:dd:ec09:8fff:ffff:ffff:ffff:ffff
154fc3f:dd:ec09:9000::/52fc3f:dd:ec09:9fff:ffff:ffff:ffff:ffff
155fc3f:dd:ec09:a000::/52fc3f:dd:ec09:afff:ffff:ffff:ffff:ffff
156fc3f:dd:ec09:b000::/52fc3f:dd:ec09:bfff:ffff:ffff:ffff:ffff
157fc3f:dd:ec09:c000::/52fc3f:dd:ec09:cfff:ffff:ffff:ffff:ffff
158fc3f:dd:ec09:d000::/52fc3f:dd:ec09:dfff:ffff:ffff:ffff:ffff
159fc3f:dd:ec09:e000::/52fc3f:dd:ec09:efff:ffff:ffff:ffff:ffff
160fc3f:dd:ec09:f000::/52fc3f:dd:ec09:ffff:ffff:ffff:ffff:ffff
161fc3f:dd:ec0a::/52fc3f:dd:ec0a:fff:ffff:ffff:ffff:ffff
162fc3f:dd:ec0a:1000::/52fc3f:dd:ec0a:1fff:ffff:ffff:ffff:ffff
163fc3f:dd:ec0a:2000::/52fc3f:dd:ec0a:2fff:ffff:ffff:ffff:ffff
164fc3f:dd:ec0a:3000::/52fc3f:dd:ec0a:3fff:ffff:ffff:ffff:ffff
165fc3f:dd:ec0a:4000::/52fc3f:dd:ec0a:4fff:ffff:ffff:ffff:ffff
166fc3f:dd:ec0a:5000::/52fc3f:dd:ec0a:5fff:ffff:ffff:ffff:ffff
167fc3f:dd:ec0a:6000::/52fc3f:dd:ec0a:6fff:ffff:ffff:ffff:ffff
168fc3f:dd:ec0a:7000::/52fc3f:dd:ec0a:7fff:ffff:ffff:ffff:ffff
169fc3f:dd:ec0a:8000::/52fc3f:dd:ec0a:8fff:ffff:ffff:ffff:ffff
170fc3f:dd:ec0a:9000::/52fc3f:dd:ec0a:9fff:ffff:ffff:ffff:ffff
171fc3f:dd:ec0a:a000::/52fc3f:dd:ec0a:afff:ffff:ffff:ffff:ffff
172fc3f:dd:ec0a:b000::/52fc3f:dd:ec0a:bfff:ffff:ffff:ffff:ffff
173fc3f:dd:ec0a:c000::/52fc3f:dd:ec0a:cfff:ffff:ffff:ffff:ffff
174fc3f:dd:ec0a:d000::/52fc3f:dd:ec0a:dfff:ffff:ffff:ffff:ffff
175fc3f:dd:ec0a:e000::/52fc3f:dd:ec0a:efff:ffff:ffff:ffff:ffff
176fc3f:dd:ec0a:f000::/52fc3f:dd:ec0a:ffff:ffff:ffff:ffff:ffff
177fc3f:dd:ec0b::/52fc3f:dd:ec0b:fff:ffff:ffff:ffff:ffff
178fc3f:dd:ec0b:1000::/52fc3f:dd:ec0b:1fff:ffff:ffff:ffff:ffff
179fc3f:dd:ec0b:2000::/52fc3f:dd:ec0b:2fff:ffff:ffff:ffff:ffff
180fc3f:dd:ec0b:3000::/52fc3f:dd:ec0b:3fff:ffff:ffff:ffff:ffff
181fc3f:dd:ec0b:4000::/52fc3f:dd:ec0b:4fff:ffff:ffff:ffff:ffff
182fc3f:dd:ec0b:5000::/52fc3f:dd:ec0b:5fff:ffff:ffff:ffff:ffff
183fc3f:dd:ec0b:6000::/52fc3f:dd:ec0b:6fff:ffff:ffff:ffff:ffff
184fc3f:dd:ec0b:7000::/52fc3f:dd:ec0b:7fff:ffff:ffff:ffff:ffff
185fc3f:dd:ec0b:8000::/52fc3f:dd:ec0b:8fff:ffff:ffff:ffff:ffff
186fc3f:dd:ec0b:9000::/52fc3f:dd:ec0b:9fff:ffff:ffff:ffff:ffff
187fc3f:dd:ec0b:a000::/52fc3f:dd:ec0b:afff:ffff:ffff:ffff:ffff
188fc3f:dd:ec0b:b000::/52fc3f:dd:ec0b:bfff:ffff:ffff:ffff:ffff
189fc3f:dd:ec0b:c000::/52fc3f:dd:ec0b:cfff:ffff:ffff:ffff:ffff
190fc3f:dd:ec0b:d000::/52fc3f:dd:ec0b:dfff:ffff:ffff:ffff:ffff
191fc3f:dd:ec0b:e000::/52fc3f:dd:ec0b:efff:ffff:ffff:ffff:ffff
192fc3f:dd:ec0b:f000::/52fc3f:dd:ec0b:ffff:ffff:ffff:ffff:ffff
193fc3f:dd:ec0c::/52fc3f:dd:ec0c:fff:ffff:ffff:ffff:ffff
194fc3f:dd:ec0c:1000::/52fc3f:dd:ec0c:1fff:ffff:ffff:ffff:ffff
195fc3f:dd:ec0c:2000::/52fc3f:dd:ec0c:2fff:ffff:ffff:ffff:ffff
196fc3f:dd:ec0c:3000::/52fc3f:dd:ec0c:3fff:ffff:ffff:ffff:ffff
197fc3f:dd:ec0c:4000::/52fc3f:dd:ec0c:4fff:ffff:ffff:ffff:ffff
198fc3f:dd:ec0c:5000::/52fc3f:dd:ec0c:5fff:ffff:ffff:ffff:ffff
199fc3f:dd:ec0c:6000::/52fc3f:dd:ec0c:6fff:ffff:ffff:ffff:ffff
200fc3f:dd:ec0c:7000::/52fc3f:dd:ec0c:7fff:ffff:ffff:ffff:ffff
201fc3f:dd:ec0c:8000::/52fc3f:dd:ec0c:8fff:ffff:ffff:ffff:ffff
202fc3f:dd:ec0c:9000::/52fc3f:dd:ec0c:9fff:ffff:ffff:ffff:ffff
203fc3f:dd:ec0c:a000::/52fc3f:dd:ec0c:afff:ffff:ffff:ffff:ffff
204fc3f:dd:ec0c:b000::/52fc3f:dd:ec0c:bfff:ffff:ffff:ffff:ffff
205fc3f:dd:ec0c:c000::/52fc3f:dd:ec0c:cfff:ffff:ffff:ffff:ffff
206fc3f:dd:ec0c:d000::/52fc3f:dd:ec0c:dfff:ffff:ffff:ffff:ffff
207fc3f:dd:ec0c:e000::/52fc3f:dd:ec0c:efff:ffff:ffff:ffff:ffff
208fc3f:dd:ec0c:f000::/52fc3f:dd:ec0c:ffff:ffff:ffff:ffff:ffff
209fc3f:dd:ec0d::/52fc3f:dd:ec0d:fff:ffff:ffff:ffff:ffff
210fc3f:dd:ec0d:1000::/52fc3f:dd:ec0d:1fff:ffff:ffff:ffff:ffff
211fc3f:dd:ec0d:2000::/52fc3f:dd:ec0d:2fff:ffff:ffff:ffff:ffff
212fc3f:dd:ec0d:3000::/52fc3f:dd:ec0d:3fff:ffff:ffff:ffff:ffff
213fc3f:dd:ec0d:4000::/52fc3f:dd:ec0d:4fff:ffff:ffff:ffff:ffff
214fc3f:dd:ec0d:5000::/52fc3f:dd:ec0d:5fff:ffff:ffff:ffff:ffff
215fc3f:dd:ec0d:6000::/52fc3f:dd:ec0d:6fff:ffff:ffff:ffff:ffff
216fc3f:dd:ec0d:7000::/52fc3f:dd:ec0d:7fff:ffff:ffff:ffff:ffff
217fc3f:dd:ec0d:8000::/52fc3f:dd:ec0d:8fff:ffff:ffff:ffff:ffff
218fc3f:dd:ec0d:9000::/52fc3f:dd:ec0d:9fff:ffff:ffff:ffff:ffff
219fc3f:dd:ec0d:a000::/52fc3f:dd:ec0d:afff:ffff:ffff:ffff:ffff
220fc3f:dd:ec0d:b000::/52fc3f:dd:ec0d:bfff:ffff:ffff:ffff:ffff
221fc3f:dd:ec0d:c000::/52fc3f:dd:ec0d:cfff:ffff:ffff:ffff:ffff
222fc3f:dd:ec0d:d000::/52fc3f:dd:ec0d:dfff:ffff:ffff:ffff:ffff
223fc3f:dd:ec0d:e000::/52fc3f:dd:ec0d:efff:ffff:ffff:ffff:ffff
224fc3f:dd:ec0d:f000::/52fc3f:dd:ec0d:ffff:ffff:ffff:ffff:ffff
225fc3f:dd:ec0e::/52fc3f:dd:ec0e:fff:ffff:ffff:ffff:ffff
226fc3f:dd:ec0e:1000::/52fc3f:dd:ec0e:1fff:ffff:ffff:ffff:ffff
227fc3f:dd:ec0e:2000::/52fc3f:dd:ec0e:2fff:ffff:ffff:ffff:ffff
228fc3f:dd:ec0e:3000::/52fc3f:dd:ec0e:3fff:ffff:ffff:ffff:ffff
229fc3f:dd:ec0e:4000::/52fc3f:dd:ec0e:4fff:ffff:ffff:ffff:ffff
230fc3f:dd:ec0e:5000::/52fc3f:dd:ec0e:5fff:ffff:ffff:ffff:ffff
231fc3f:dd:ec0e:6000::/52fc3f:dd:ec0e:6fff:ffff:ffff:ffff:ffff
232fc3f:dd:ec0e:7000::/52fc3f:dd:ec0e:7fff:ffff:ffff:ffff:ffff
233fc3f:dd:ec0e:8000::/52fc3f:dd:ec0e:8fff:ffff:ffff:ffff:ffff
234fc3f:dd:ec0e:9000::/52fc3f:dd:ec0e:9fff:ffff:ffff:ffff:ffff
235fc3f:dd:ec0e:a000::/52fc3f:dd:ec0e:afff:ffff:ffff:ffff:ffff
236fc3f:dd:ec0e:b000::/52fc3f:dd:ec0e:bfff:ffff:ffff:ffff:ffff
237fc3f:dd:ec0e:c000::/52fc3f:dd:ec0e:cfff:ffff:ffff:ffff:ffff
238fc3f:dd:ec0e:d000::/52fc3f:dd:ec0e:dfff:ffff:ffff:ffff:ffff
239fc3f:dd:ec0e:e000::/52fc3f:dd:ec0e:efff:ffff:ffff:ffff:ffff
240fc3f:dd:ec0e:f000::/52fc3f:dd:ec0e:ffff:ffff:ffff:ffff:ffff
241fc3f:dd:ec0f::/52fc3f:dd:ec0f:fff:ffff:ffff:ffff:ffff
242fc3f:dd:ec0f:1000::/52fc3f:dd:ec0f:1fff:ffff:ffff:ffff:ffff
243fc3f:dd:ec0f:2000::/52fc3f:dd:ec0f:2fff:ffff:ffff:ffff:ffff
244fc3f:dd:ec0f:3000::/52fc3f:dd:ec0f:3fff:ffff:ffff:ffff:ffff
245fc3f:dd:ec0f:4000::/52fc3f:dd:ec0f:4fff:ffff:ffff:ffff:ffff
246fc3f:dd:ec0f:5000::/52fc3f:dd:ec0f:5fff:ffff:ffff:ffff:ffff
247fc3f:dd:ec0f:6000::/52fc3f:dd:ec0f:6fff:ffff:ffff:ffff:ffff
248fc3f:dd:ec0f:7000::/52fc3f:dd:ec0f:7fff:ffff:ffff:ffff:ffff
249fc3f:dd:ec0f:8000::/52fc3f:dd:ec0f:8fff:ffff:ffff:ffff:ffff
250fc3f:dd:ec0f:9000::/52fc3f:dd:ec0f:9fff:ffff:ffff:ffff:ffff
251fc3f:dd:ec0f:a000::/52fc3f:dd:ec0f:afff:ffff:ffff:ffff:ffff
252fc3f:dd:ec0f:b000::/52fc3f:dd:ec0f:bfff:ffff:ffff:ffff:ffff
253fc3f:dd:ec0f:c000::/52fc3f:dd:ec0f:cfff:ffff:ffff:ffff:ffff
254fc3f:dd:ec0f:d000::/52fc3f:dd:ec0f:dfff:ffff:ffff:ffff:ffff
255fc3f:dd:ec0f:e000::/52fc3f:dd:ec0f:efff:ffff:ffff:ffff:ffff
256fc3f:dd:ec0f:f000::/52fc3f:dd:ec0f: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.