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/88
Addresses2^40
/64 networksPart of one
Network
100::950:d600:0:0/88
First address
100::950:d600:0:0
Last address
100::950:d6ff:ffff:ffff
Addresses
1,099,511,627,776 (2^40)
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
0100:0000:0000:0000:0950:d600:0000:0000
Type
Discard only 100::/64
Traffic sent here is dropped (RFC 6666)
Reverse DNS zone
6.d.0.5.9.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.ip6.arpa
Split into smaller subnets/104
/89 (2)/90 (4)/91 (8)/92 (16)/96 (256)/100 (4,096)/104 (65,536)

100::950:d600:0:0/88 makes 65,536 subnets of /104; the first 256 are listed.

Subnets
#SubnetLast address
1100::950:d600:0:0/104100::950:d600:ff:ffff
2100::950:d600:100:0/104100::950:d600:1ff:ffff
3100::950:d600:200:0/104100::950:d600:2ff:ffff
4100::950:d600:300:0/104100::950:d600:3ff:ffff
5100::950:d600:400:0/104100::950:d600:4ff:ffff
6100::950:d600:500:0/104100::950:d600:5ff:ffff
7100::950:d600:600:0/104100::950:d600:6ff:ffff
8100::950:d600:700:0/104100::950:d600:7ff:ffff
9100::950:d600:800:0/104100::950:d600:8ff:ffff
10100::950:d600:900:0/104100::950:d600:9ff:ffff
11100::950:d600:a00:0/104100::950:d600:aff:ffff
12100::950:d600:b00:0/104100::950:d600:bff:ffff
13100::950:d600:c00:0/104100::950:d600:cff:ffff
14100::950:d600:d00:0/104100::950:d600:dff:ffff
15100::950:d600:e00:0/104100::950:d600:eff:ffff
16100::950:d600:f00:0/104100::950:d600:fff:ffff
17100::950:d600:1000:0/104100::950:d600:10ff:ffff
18100::950:d600:1100:0/104100::950:d600:11ff:ffff
19100::950:d600:1200:0/104100::950:d600:12ff:ffff
20100::950:d600:1300:0/104100::950:d600:13ff:ffff
21100::950:d600:1400:0/104100::950:d600:14ff:ffff
22100::950:d600:1500:0/104100::950:d600:15ff:ffff
23100::950:d600:1600:0/104100::950:d600:16ff:ffff
24100::950:d600:1700:0/104100::950:d600:17ff:ffff
25100::950:d600:1800:0/104100::950:d600:18ff:ffff
26100::950:d600:1900:0/104100::950:d600:19ff:ffff
27100::950:d600:1a00:0/104100::950:d600:1aff:ffff
28100::950:d600:1b00:0/104100::950:d600:1bff:ffff
29100::950:d600:1c00:0/104100::950:d600:1cff:ffff
30100::950:d600:1d00:0/104100::950:d600:1dff:ffff
31100::950:d600:1e00:0/104100::950:d600:1eff:ffff
32100::950:d600:1f00:0/104100::950:d600:1fff:ffff
33100::950:d600:2000:0/104100::950:d600:20ff:ffff
34100::950:d600:2100:0/104100::950:d600:21ff:ffff
35100::950:d600:2200:0/104100::950:d600:22ff:ffff
36100::950:d600:2300:0/104100::950:d600:23ff:ffff
37100::950:d600:2400:0/104100::950:d600:24ff:ffff
38100::950:d600:2500:0/104100::950:d600:25ff:ffff
39100::950:d600:2600:0/104100::950:d600:26ff:ffff
40100::950:d600:2700:0/104100::950:d600:27ff:ffff
41100::950:d600:2800:0/104100::950:d600:28ff:ffff
42100::950:d600:2900:0/104100::950:d600:29ff:ffff
43100::950:d600:2a00:0/104100::950:d600:2aff:ffff
44100::950:d600:2b00:0/104100::950:d600:2bff:ffff
45100::950:d600:2c00:0/104100::950:d600:2cff:ffff
46100::950:d600:2d00:0/104100::950:d600:2dff:ffff
47100::950:d600:2e00:0/104100::950:d600:2eff:ffff
48100::950:d600:2f00:0/104100::950:d600:2fff:ffff
49100::950:d600:3000:0/104100::950:d600:30ff:ffff
50100::950:d600:3100:0/104100::950:d600:31ff:ffff
51100::950:d600:3200:0/104100::950:d600:32ff:ffff
52100::950:d600:3300:0/104100::950:d600:33ff:ffff
53100::950:d600:3400:0/104100::950:d600:34ff:ffff
54100::950:d600:3500:0/104100::950:d600:35ff:ffff
55100::950:d600:3600:0/104100::950:d600:36ff:ffff
56100::950:d600:3700:0/104100::950:d600:37ff:ffff
57100::950:d600:3800:0/104100::950:d600:38ff:ffff
58100::950:d600:3900:0/104100::950:d600:39ff:ffff
59100::950:d600:3a00:0/104100::950:d600:3aff:ffff
60100::950:d600:3b00:0/104100::950:d600:3bff:ffff
61100::950:d600:3c00:0/104100::950:d600:3cff:ffff
62100::950:d600:3d00:0/104100::950:d600:3dff:ffff
63100::950:d600:3e00:0/104100::950:d600:3eff:ffff
64100::950:d600:3f00:0/104100::950:d600:3fff:ffff
65100::950:d600:4000:0/104100::950:d600:40ff:ffff
66100::950:d600:4100:0/104100::950:d600:41ff:ffff
67100::950:d600:4200:0/104100::950:d600:42ff:ffff
68100::950:d600:4300:0/104100::950:d600:43ff:ffff
69100::950:d600:4400:0/104100::950:d600:44ff:ffff
70100::950:d600:4500:0/104100::950:d600:45ff:ffff
71100::950:d600:4600:0/104100::950:d600:46ff:ffff
72100::950:d600:4700:0/104100::950:d600:47ff:ffff
73100::950:d600:4800:0/104100::950:d600:48ff:ffff
74100::950:d600:4900:0/104100::950:d600:49ff:ffff
75100::950:d600:4a00:0/104100::950:d600:4aff:ffff
76100::950:d600:4b00:0/104100::950:d600:4bff:ffff
77100::950:d600:4c00:0/104100::950:d600:4cff:ffff
78100::950:d600:4d00:0/104100::950:d600:4dff:ffff
79100::950:d600:4e00:0/104100::950:d600:4eff:ffff
80100::950:d600:4f00:0/104100::950:d600:4fff:ffff
81100::950:d600:5000:0/104100::950:d600:50ff:ffff
82100::950:d600:5100:0/104100::950:d600:51ff:ffff
83100::950:d600:5200:0/104100::950:d600:52ff:ffff
84100::950:d600:5300:0/104100::950:d600:53ff:ffff
85100::950:d600:5400:0/104100::950:d600:54ff:ffff
86100::950:d600:5500:0/104100::950:d600:55ff:ffff
87100::950:d600:5600:0/104100::950:d600:56ff:ffff
88100::950:d600:5700:0/104100::950:d600:57ff:ffff
89100::950:d600:5800:0/104100::950:d600:58ff:ffff
90100::950:d600:5900:0/104100::950:d600:59ff:ffff
91100::950:d600:5a00:0/104100::950:d600:5aff:ffff
92100::950:d600:5b00:0/104100::950:d600:5bff:ffff
93100::950:d600:5c00:0/104100::950:d600:5cff:ffff
94100::950:d600:5d00:0/104100::950:d600:5dff:ffff
95100::950:d600:5e00:0/104100::950:d600:5eff:ffff
96100::950:d600:5f00:0/104100::950:d600:5fff:ffff
97100::950:d600:6000:0/104100::950:d600:60ff:ffff
98100::950:d600:6100:0/104100::950:d600:61ff:ffff
99100::950:d600:6200:0/104100::950:d600:62ff:ffff
100100::950:d600:6300:0/104100::950:d600:63ff:ffff
101100::950:d600:6400:0/104100::950:d600:64ff:ffff
102100::950:d600:6500:0/104100::950:d600:65ff:ffff
103100::950:d600:6600:0/104100::950:d600:66ff:ffff
104100::950:d600:6700:0/104100::950:d600:67ff:ffff
105100::950:d600:6800:0/104100::950:d600:68ff:ffff
106100::950:d600:6900:0/104100::950:d600:69ff:ffff
107100::950:d600:6a00:0/104100::950:d600:6aff:ffff
108100::950:d600:6b00:0/104100::950:d600:6bff:ffff
109100::950:d600:6c00:0/104100::950:d600:6cff:ffff
110100::950:d600:6d00:0/104100::950:d600:6dff:ffff
111100::950:d600:6e00:0/104100::950:d600:6eff:ffff
112100::950:d600:6f00:0/104100::950:d600:6fff:ffff
113100::950:d600:7000:0/104100::950:d600:70ff:ffff
114100::950:d600:7100:0/104100::950:d600:71ff:ffff
115100::950:d600:7200:0/104100::950:d600:72ff:ffff
116100::950:d600:7300:0/104100::950:d600:73ff:ffff
117100::950:d600:7400:0/104100::950:d600:74ff:ffff
118100::950:d600:7500:0/104100::950:d600:75ff:ffff
119100::950:d600:7600:0/104100::950:d600:76ff:ffff
120100::950:d600:7700:0/104100::950:d600:77ff:ffff
121100::950:d600:7800:0/104100::950:d600:78ff:ffff
122100::950:d600:7900:0/104100::950:d600:79ff:ffff
123100::950:d600:7a00:0/104100::950:d600:7aff:ffff
124100::950:d600:7b00:0/104100::950:d600:7bff:ffff
125100::950:d600:7c00:0/104100::950:d600:7cff:ffff
126100::950:d600:7d00:0/104100::950:d600:7dff:ffff
127100::950:d600:7e00:0/104100::950:d600:7eff:ffff
128100::950:d600:7f00:0/104100::950:d600:7fff:ffff
129100::950:d600:8000:0/104100::950:d600:80ff:ffff
130100::950:d600:8100:0/104100::950:d600:81ff:ffff
131100::950:d600:8200:0/104100::950:d600:82ff:ffff
132100::950:d600:8300:0/104100::950:d600:83ff:ffff
133100::950:d600:8400:0/104100::950:d600:84ff:ffff
134100::950:d600:8500:0/104100::950:d600:85ff:ffff
135100::950:d600:8600:0/104100::950:d600:86ff:ffff
136100::950:d600:8700:0/104100::950:d600:87ff:ffff
137100::950:d600:8800:0/104100::950:d600:88ff:ffff
138100::950:d600:8900:0/104100::950:d600:89ff:ffff
139100::950:d600:8a00:0/104100::950:d600:8aff:ffff
140100::950:d600:8b00:0/104100::950:d600:8bff:ffff
141100::950:d600:8c00:0/104100::950:d600:8cff:ffff
142100::950:d600:8d00:0/104100::950:d600:8dff:ffff
143100::950:d600:8e00:0/104100::950:d600:8eff:ffff
144100::950:d600:8f00:0/104100::950:d600:8fff:ffff
145100::950:d600:9000:0/104100::950:d600:90ff:ffff
146100::950:d600:9100:0/104100::950:d600:91ff:ffff
147100::950:d600:9200:0/104100::950:d600:92ff:ffff
148100::950:d600:9300:0/104100::950:d600:93ff:ffff
149100::950:d600:9400:0/104100::950:d600:94ff:ffff
150100::950:d600:9500:0/104100::950:d600:95ff:ffff
151100::950:d600:9600:0/104100::950:d600:96ff:ffff
152100::950:d600:9700:0/104100::950:d600:97ff:ffff
153100::950:d600:9800:0/104100::950:d600:98ff:ffff
154100::950:d600:9900:0/104100::950:d600:99ff:ffff
155100::950:d600:9a00:0/104100::950:d600:9aff:ffff
156100::950:d600:9b00:0/104100::950:d600:9bff:ffff
157100::950:d600:9c00:0/104100::950:d600:9cff:ffff
158100::950:d600:9d00:0/104100::950:d600:9dff:ffff
159100::950:d600:9e00:0/104100::950:d600:9eff:ffff
160100::950:d600:9f00:0/104100::950:d600:9fff:ffff
161100::950:d600:a000:0/104100::950:d600:a0ff:ffff
162100::950:d600:a100:0/104100::950:d600:a1ff:ffff
163100::950:d600:a200:0/104100::950:d600:a2ff:ffff
164100::950:d600:a300:0/104100::950:d600:a3ff:ffff
165100::950:d600:a400:0/104100::950:d600:a4ff:ffff
166100::950:d600:a500:0/104100::950:d600:a5ff:ffff
167100::950:d600:a600:0/104100::950:d600:a6ff:ffff
168100::950:d600:a700:0/104100::950:d600:a7ff:ffff
169100::950:d600:a800:0/104100::950:d600:a8ff:ffff
170100::950:d600:a900:0/104100::950:d600:a9ff:ffff
171100::950:d600:aa00:0/104100::950:d600:aaff:ffff
172100::950:d600:ab00:0/104100::950:d600:abff:ffff
173100::950:d600:ac00:0/104100::950:d600:acff:ffff
174100::950:d600:ad00:0/104100::950:d600:adff:ffff
175100::950:d600:ae00:0/104100::950:d600:aeff:ffff
176100::950:d600:af00:0/104100::950:d600:afff:ffff
177100::950:d600:b000:0/104100::950:d600:b0ff:ffff
178100::950:d600:b100:0/104100::950:d600:b1ff:ffff
179100::950:d600:b200:0/104100::950:d600:b2ff:ffff
180100::950:d600:b300:0/104100::950:d600:b3ff:ffff
181100::950:d600:b400:0/104100::950:d600:b4ff:ffff
182100::950:d600:b500:0/104100::950:d600:b5ff:ffff
183100::950:d600:b600:0/104100::950:d600:b6ff:ffff
184100::950:d600:b700:0/104100::950:d600:b7ff:ffff
185100::950:d600:b800:0/104100::950:d600:b8ff:ffff
186100::950:d600:b900:0/104100::950:d600:b9ff:ffff
187100::950:d600:ba00:0/104100::950:d600:baff:ffff
188100::950:d600:bb00:0/104100::950:d600:bbff:ffff
189100::950:d600:bc00:0/104100::950:d600:bcff:ffff
190100::950:d600:bd00:0/104100::950:d600:bdff:ffff
191100::950:d600:be00:0/104100::950:d600:beff:ffff
192100::950:d600:bf00:0/104100::950:d600:bfff:ffff
193100::950:d600:c000:0/104100::950:d600:c0ff:ffff
194100::950:d600:c100:0/104100::950:d600:c1ff:ffff
195100::950:d600:c200:0/104100::950:d600:c2ff:ffff
196100::950:d600:c300:0/104100::950:d600:c3ff:ffff
197100::950:d600:c400:0/104100::950:d600:c4ff:ffff
198100::950:d600:c500:0/104100::950:d600:c5ff:ffff
199100::950:d600:c600:0/104100::950:d600:c6ff:ffff
200100::950:d600:c700:0/104100::950:d600:c7ff:ffff
201100::950:d600:c800:0/104100::950:d600:c8ff:ffff
202100::950:d600:c900:0/104100::950:d600:c9ff:ffff
203100::950:d600:ca00:0/104100::950:d600:caff:ffff
204100::950:d600:cb00:0/104100::950:d600:cbff:ffff
205100::950:d600:cc00:0/104100::950:d600:ccff:ffff
206100::950:d600:cd00:0/104100::950:d600:cdff:ffff
207100::950:d600:ce00:0/104100::950:d600:ceff:ffff
208100::950:d600:cf00:0/104100::950:d600:cfff:ffff
209100::950:d600:d000:0/104100::950:d600:d0ff:ffff
210100::950:d600:d100:0/104100::950:d600:d1ff:ffff
211100::950:d600:d200:0/104100::950:d600:d2ff:ffff
212100::950:d600:d300:0/104100::950:d600:d3ff:ffff
213100::950:d600:d400:0/104100::950:d600:d4ff:ffff
214100::950:d600:d500:0/104100::950:d600:d5ff:ffff
215100::950:d600:d600:0/104100::950:d600:d6ff:ffff
216100::950:d600:d700:0/104100::950:d600:d7ff:ffff
217100::950:d600:d800:0/104100::950:d600:d8ff:ffff
218100::950:d600:d900:0/104100::950:d600:d9ff:ffff
219100::950:d600:da00:0/104100::950:d600:daff:ffff
220100::950:d600:db00:0/104100::950:d600:dbff:ffff
221100::950:d600:dc00:0/104100::950:d600:dcff:ffff
222100::950:d600:dd00:0/104100::950:d600:ddff:ffff
223100::950:d600:de00:0/104100::950:d600:deff:ffff
224100::950:d600:df00:0/104100::950:d600:dfff:ffff
225100::950:d600:e000:0/104100::950:d600:e0ff:ffff
226100::950:d600:e100:0/104100::950:d600:e1ff:ffff
227100::950:d600:e200:0/104100::950:d600:e2ff:ffff
228100::950:d600:e300:0/104100::950:d600:e3ff:ffff
229100::950:d600:e400:0/104100::950:d600:e4ff:ffff
230100::950:d600:e500:0/104100::950:d600:e5ff:ffff
231100::950:d600:e600:0/104100::950:d600:e6ff:ffff
232100::950:d600:e700:0/104100::950:d600:e7ff:ffff
233100::950:d600:e800:0/104100::950:d600:e8ff:ffff
234100::950:d600:e900:0/104100::950:d600:e9ff:ffff
235100::950:d600:ea00:0/104100::950:d600:eaff:ffff
236100::950:d600:eb00:0/104100::950:d600:ebff:ffff
237100::950:d600:ec00:0/104100::950:d600:ecff:ffff
238100::950:d600:ed00:0/104100::950:d600:edff:ffff
239100::950:d600:ee00:0/104100::950:d600:eeff:ffff
240100::950:d600:ef00:0/104100::950:d600:efff:ffff
241100::950:d600:f000:0/104100::950:d600:f0ff:ffff
242100::950:d600:f100:0/104100::950:d600:f1ff:ffff
243100::950:d600:f200:0/104100::950:d600:f2ff:ffff
244100::950:d600:f300:0/104100::950:d600:f3ff:ffff
245100::950:d600:f400:0/104100::950:d600:f4ff:ffff
246100::950:d600:f500:0/104100::950:d600:f5ff:ffff
247100::950:d600:f600:0/104100::950:d600:f6ff:ffff
248100::950:d600:f700:0/104100::950:d600:f7ff:ffff
249100::950:d600:f800:0/104100::950:d600:f8ff:ffff
250100::950:d600:f900:0/104100::950:d600:f9ff:ffff
251100::950:d600:fa00:0/104100::950:d600:faff:ffff
252100::950:d600:fb00:0/104100::950:d600:fbff:ffff
253100::950:d600:fc00:0/104100::950:d600:fcff:ffff
254100::950:d600:fd00:0/104100::950:d600:fdff:ffff
255100::950:d600:fe00:0/104100::950:d600:feff:ffff
256100::950:d600:ff00:0/104100::950:d600: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.