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/8
Addresses2^120
/64 networks2^56
Network
2700::/8
First address
2700::
Last address
27ff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
1,329,227,995,784,915,872,903,807,060,280,344,576 (2^120)
/64 networks (LANs)
72,057,594,037,927,936 (2^56)
Full form
2700:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
7.2.ip6.arpa
Split into smaller subnets/20
/9 (2)/10 (4)/11 (8)/12 (16)/16 (256)/20 (4,096)/24 (65,536)

2700::/8 makes 4,096 subnets of /20; the first 256 are listed.

Subnets
#SubnetLast address
12700::/202700:fff:ffff:ffff:ffff:ffff:ffff:ffff
22700:1000::/202700:1fff:ffff:ffff:ffff:ffff:ffff:ffff
32700:2000::/202700:2fff:ffff:ffff:ffff:ffff:ffff:ffff
42700:3000::/202700:3fff:ffff:ffff:ffff:ffff:ffff:ffff
52700:4000::/202700:4fff:ffff:ffff:ffff:ffff:ffff:ffff
62700:5000::/202700:5fff:ffff:ffff:ffff:ffff:ffff:ffff
72700:6000::/202700:6fff:ffff:ffff:ffff:ffff:ffff:ffff
82700:7000::/202700:7fff:ffff:ffff:ffff:ffff:ffff:ffff
92700:8000::/202700:8fff:ffff:ffff:ffff:ffff:ffff:ffff
102700:9000::/202700:9fff:ffff:ffff:ffff:ffff:ffff:ffff
112700:a000::/202700:afff:ffff:ffff:ffff:ffff:ffff:ffff
122700:b000::/202700:bfff:ffff:ffff:ffff:ffff:ffff:ffff
132700:c000::/202700:cfff:ffff:ffff:ffff:ffff:ffff:ffff
142700:d000::/202700:dfff:ffff:ffff:ffff:ffff:ffff:ffff
152700:e000::/202700:efff:ffff:ffff:ffff:ffff:ffff:ffff
162700:f000::/202700:ffff:ffff:ffff:ffff:ffff:ffff:ffff
172701::/202701:fff:ffff:ffff:ffff:ffff:ffff:ffff
182701:1000::/202701:1fff:ffff:ffff:ffff:ffff:ffff:ffff
192701:2000::/202701:2fff:ffff:ffff:ffff:ffff:ffff:ffff
202701:3000::/202701:3fff:ffff:ffff:ffff:ffff:ffff:ffff
212701:4000::/202701:4fff:ffff:ffff:ffff:ffff:ffff:ffff
222701:5000::/202701:5fff:ffff:ffff:ffff:ffff:ffff:ffff
232701:6000::/202701:6fff:ffff:ffff:ffff:ffff:ffff:ffff
242701:7000::/202701:7fff:ffff:ffff:ffff:ffff:ffff:ffff
252701:8000::/202701:8fff:ffff:ffff:ffff:ffff:ffff:ffff
262701:9000::/202701:9fff:ffff:ffff:ffff:ffff:ffff:ffff
272701:a000::/202701:afff:ffff:ffff:ffff:ffff:ffff:ffff
282701:b000::/202701:bfff:ffff:ffff:ffff:ffff:ffff:ffff
292701:c000::/202701:cfff:ffff:ffff:ffff:ffff:ffff:ffff
302701:d000::/202701:dfff:ffff:ffff:ffff:ffff:ffff:ffff
312701:e000::/202701:efff:ffff:ffff:ffff:ffff:ffff:ffff
322701:f000::/202701:ffff:ffff:ffff:ffff:ffff:ffff:ffff
332702::/202702:fff:ffff:ffff:ffff:ffff:ffff:ffff
342702:1000::/202702:1fff:ffff:ffff:ffff:ffff:ffff:ffff
352702:2000::/202702:2fff:ffff:ffff:ffff:ffff:ffff:ffff
362702:3000::/202702:3fff:ffff:ffff:ffff:ffff:ffff:ffff
372702:4000::/202702:4fff:ffff:ffff:ffff:ffff:ffff:ffff
382702:5000::/202702:5fff:ffff:ffff:ffff:ffff:ffff:ffff
392702:6000::/202702:6fff:ffff:ffff:ffff:ffff:ffff:ffff
402702:7000::/202702:7fff:ffff:ffff:ffff:ffff:ffff:ffff
412702:8000::/202702:8fff:ffff:ffff:ffff:ffff:ffff:ffff
422702:9000::/202702:9fff:ffff:ffff:ffff:ffff:ffff:ffff
432702:a000::/202702:afff:ffff:ffff:ffff:ffff:ffff:ffff
442702:b000::/202702:bfff:ffff:ffff:ffff:ffff:ffff:ffff
452702:c000::/202702:cfff:ffff:ffff:ffff:ffff:ffff:ffff
462702:d000::/202702:dfff:ffff:ffff:ffff:ffff:ffff:ffff
472702:e000::/202702:efff:ffff:ffff:ffff:ffff:ffff:ffff
482702:f000::/202702:ffff:ffff:ffff:ffff:ffff:ffff:ffff
492703::/202703:fff:ffff:ffff:ffff:ffff:ffff:ffff
502703:1000::/202703:1fff:ffff:ffff:ffff:ffff:ffff:ffff
512703:2000::/202703:2fff:ffff:ffff:ffff:ffff:ffff:ffff
522703:3000::/202703:3fff:ffff:ffff:ffff:ffff:ffff:ffff
532703:4000::/202703:4fff:ffff:ffff:ffff:ffff:ffff:ffff
542703:5000::/202703:5fff:ffff:ffff:ffff:ffff:ffff:ffff
552703:6000::/202703:6fff:ffff:ffff:ffff:ffff:ffff:ffff
562703:7000::/202703:7fff:ffff:ffff:ffff:ffff:ffff:ffff
572703:8000::/202703:8fff:ffff:ffff:ffff:ffff:ffff:ffff
582703:9000::/202703:9fff:ffff:ffff:ffff:ffff:ffff:ffff
592703:a000::/202703:afff:ffff:ffff:ffff:ffff:ffff:ffff
602703:b000::/202703:bfff:ffff:ffff:ffff:ffff:ffff:ffff
612703:c000::/202703:cfff:ffff:ffff:ffff:ffff:ffff:ffff
622703:d000::/202703:dfff:ffff:ffff:ffff:ffff:ffff:ffff
632703:e000::/202703:efff:ffff:ffff:ffff:ffff:ffff:ffff
642703:f000::/202703:ffff:ffff:ffff:ffff:ffff:ffff:ffff
652704::/202704:fff:ffff:ffff:ffff:ffff:ffff:ffff
662704:1000::/202704:1fff:ffff:ffff:ffff:ffff:ffff:ffff
672704:2000::/202704:2fff:ffff:ffff:ffff:ffff:ffff:ffff
682704:3000::/202704:3fff:ffff:ffff:ffff:ffff:ffff:ffff
692704:4000::/202704:4fff:ffff:ffff:ffff:ffff:ffff:ffff
702704:5000::/202704:5fff:ffff:ffff:ffff:ffff:ffff:ffff
712704:6000::/202704:6fff:ffff:ffff:ffff:ffff:ffff:ffff
722704:7000::/202704:7fff:ffff:ffff:ffff:ffff:ffff:ffff
732704:8000::/202704:8fff:ffff:ffff:ffff:ffff:ffff:ffff
742704:9000::/202704:9fff:ffff:ffff:ffff:ffff:ffff:ffff
752704:a000::/202704:afff:ffff:ffff:ffff:ffff:ffff:ffff
762704:b000::/202704:bfff:ffff:ffff:ffff:ffff:ffff:ffff
772704:c000::/202704:cfff:ffff:ffff:ffff:ffff:ffff:ffff
782704:d000::/202704:dfff:ffff:ffff:ffff:ffff:ffff:ffff
792704:e000::/202704:efff:ffff:ffff:ffff:ffff:ffff:ffff
802704:f000::/202704:ffff:ffff:ffff:ffff:ffff:ffff:ffff
812705::/202705:fff:ffff:ffff:ffff:ffff:ffff:ffff
822705:1000::/202705:1fff:ffff:ffff:ffff:ffff:ffff:ffff
832705:2000::/202705:2fff:ffff:ffff:ffff:ffff:ffff:ffff
842705:3000::/202705:3fff:ffff:ffff:ffff:ffff:ffff:ffff
852705:4000::/202705:4fff:ffff:ffff:ffff:ffff:ffff:ffff
862705:5000::/202705:5fff:ffff:ffff:ffff:ffff:ffff:ffff
872705:6000::/202705:6fff:ffff:ffff:ffff:ffff:ffff:ffff
882705:7000::/202705:7fff:ffff:ffff:ffff:ffff:ffff:ffff
892705:8000::/202705:8fff:ffff:ffff:ffff:ffff:ffff:ffff
902705:9000::/202705:9fff:ffff:ffff:ffff:ffff:ffff:ffff
912705:a000::/202705:afff:ffff:ffff:ffff:ffff:ffff:ffff
922705:b000::/202705:bfff:ffff:ffff:ffff:ffff:ffff:ffff
932705:c000::/202705:cfff:ffff:ffff:ffff:ffff:ffff:ffff
942705:d000::/202705:dfff:ffff:ffff:ffff:ffff:ffff:ffff
952705:e000::/202705:efff:ffff:ffff:ffff:ffff:ffff:ffff
962705:f000::/202705:ffff:ffff:ffff:ffff:ffff:ffff:ffff
972706::/202706:fff:ffff:ffff:ffff:ffff:ffff:ffff
982706:1000::/202706:1fff:ffff:ffff:ffff:ffff:ffff:ffff
992706:2000::/202706:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1002706:3000::/202706:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1012706:4000::/202706:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1022706:5000::/202706:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1032706:6000::/202706:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1042706:7000::/202706:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1052706:8000::/202706:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1062706:9000::/202706:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1072706:a000::/202706:afff:ffff:ffff:ffff:ffff:ffff:ffff
1082706:b000::/202706:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1092706:c000::/202706:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1102706:d000::/202706:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1112706:e000::/202706:efff:ffff:ffff:ffff:ffff:ffff:ffff
1122706:f000::/202706:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1132707::/202707:fff:ffff:ffff:ffff:ffff:ffff:ffff
1142707:1000::/202707:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1152707:2000::/202707:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1162707:3000::/202707:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1172707:4000::/202707:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1182707:5000::/202707:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1192707:6000::/202707:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1202707:7000::/202707:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1212707:8000::/202707:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1222707:9000::/202707:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1232707:a000::/202707:afff:ffff:ffff:ffff:ffff:ffff:ffff
1242707:b000::/202707:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1252707:c000::/202707:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1262707:d000::/202707:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1272707:e000::/202707:efff:ffff:ffff:ffff:ffff:ffff:ffff
1282707:f000::/202707:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1292708::/202708:fff:ffff:ffff:ffff:ffff:ffff:ffff
1302708:1000::/202708:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1312708:2000::/202708:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1322708:3000::/202708:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1332708:4000::/202708:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1342708:5000::/202708:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1352708:6000::/202708:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1362708:7000::/202708:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1372708:8000::/202708:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1382708:9000::/202708:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1392708:a000::/202708:afff:ffff:ffff:ffff:ffff:ffff:ffff
1402708:b000::/202708:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1412708:c000::/202708:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1422708:d000::/202708:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1432708:e000::/202708:efff:ffff:ffff:ffff:ffff:ffff:ffff
1442708:f000::/202708:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1452709::/202709:fff:ffff:ffff:ffff:ffff:ffff:ffff
1462709:1000::/202709:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1472709:2000::/202709:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1482709:3000::/202709:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1492709:4000::/202709:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1502709:5000::/202709:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1512709:6000::/202709:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1522709:7000::/202709:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1532709:8000::/202709:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1542709:9000::/202709:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1552709:a000::/202709:afff:ffff:ffff:ffff:ffff:ffff:ffff
1562709:b000::/202709:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1572709:c000::/202709:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1582709:d000::/202709:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1592709:e000::/202709:efff:ffff:ffff:ffff:ffff:ffff:ffff
1602709:f000::/202709:ffff:ffff:ffff:ffff:ffff:ffff:ffff
161270a::/20270a:fff:ffff:ffff:ffff:ffff:ffff:ffff
162270a:1000::/20270a:1fff:ffff:ffff:ffff:ffff:ffff:ffff
163270a:2000::/20270a:2fff:ffff:ffff:ffff:ffff:ffff:ffff
164270a:3000::/20270a:3fff:ffff:ffff:ffff:ffff:ffff:ffff
165270a:4000::/20270a:4fff:ffff:ffff:ffff:ffff:ffff:ffff
166270a:5000::/20270a:5fff:ffff:ffff:ffff:ffff:ffff:ffff
167270a:6000::/20270a:6fff:ffff:ffff:ffff:ffff:ffff:ffff
168270a:7000::/20270a:7fff:ffff:ffff:ffff:ffff:ffff:ffff
169270a:8000::/20270a:8fff:ffff:ffff:ffff:ffff:ffff:ffff
170270a:9000::/20270a:9fff:ffff:ffff:ffff:ffff:ffff:ffff
171270a:a000::/20270a:afff:ffff:ffff:ffff:ffff:ffff:ffff
172270a:b000::/20270a:bfff:ffff:ffff:ffff:ffff:ffff:ffff
173270a:c000::/20270a:cfff:ffff:ffff:ffff:ffff:ffff:ffff
174270a:d000::/20270a:dfff:ffff:ffff:ffff:ffff:ffff:ffff
175270a:e000::/20270a:efff:ffff:ffff:ffff:ffff:ffff:ffff
176270a:f000::/20270a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
177270b::/20270b:fff:ffff:ffff:ffff:ffff:ffff:ffff
178270b:1000::/20270b:1fff:ffff:ffff:ffff:ffff:ffff:ffff
179270b:2000::/20270b:2fff:ffff:ffff:ffff:ffff:ffff:ffff
180270b:3000::/20270b:3fff:ffff:ffff:ffff:ffff:ffff:ffff
181270b:4000::/20270b:4fff:ffff:ffff:ffff:ffff:ffff:ffff
182270b:5000::/20270b:5fff:ffff:ffff:ffff:ffff:ffff:ffff
183270b:6000::/20270b:6fff:ffff:ffff:ffff:ffff:ffff:ffff
184270b:7000::/20270b:7fff:ffff:ffff:ffff:ffff:ffff:ffff
185270b:8000::/20270b:8fff:ffff:ffff:ffff:ffff:ffff:ffff
186270b:9000::/20270b:9fff:ffff:ffff:ffff:ffff:ffff:ffff
187270b:a000::/20270b:afff:ffff:ffff:ffff:ffff:ffff:ffff
188270b:b000::/20270b:bfff:ffff:ffff:ffff:ffff:ffff:ffff
189270b:c000::/20270b:cfff:ffff:ffff:ffff:ffff:ffff:ffff
190270b:d000::/20270b:dfff:ffff:ffff:ffff:ffff:ffff:ffff
191270b:e000::/20270b:efff:ffff:ffff:ffff:ffff:ffff:ffff
192270b:f000::/20270b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
193270c::/20270c:fff:ffff:ffff:ffff:ffff:ffff:ffff
194270c:1000::/20270c:1fff:ffff:ffff:ffff:ffff:ffff:ffff
195270c:2000::/20270c:2fff:ffff:ffff:ffff:ffff:ffff:ffff
196270c:3000::/20270c:3fff:ffff:ffff:ffff:ffff:ffff:ffff
197270c:4000::/20270c:4fff:ffff:ffff:ffff:ffff:ffff:ffff
198270c:5000::/20270c:5fff:ffff:ffff:ffff:ffff:ffff:ffff
199270c:6000::/20270c:6fff:ffff:ffff:ffff:ffff:ffff:ffff
200270c:7000::/20270c:7fff:ffff:ffff:ffff:ffff:ffff:ffff
201270c:8000::/20270c:8fff:ffff:ffff:ffff:ffff:ffff:ffff
202270c:9000::/20270c:9fff:ffff:ffff:ffff:ffff:ffff:ffff
203270c:a000::/20270c:afff:ffff:ffff:ffff:ffff:ffff:ffff
204270c:b000::/20270c:bfff:ffff:ffff:ffff:ffff:ffff:ffff
205270c:c000::/20270c:cfff:ffff:ffff:ffff:ffff:ffff:ffff
206270c:d000::/20270c:dfff:ffff:ffff:ffff:ffff:ffff:ffff
207270c:e000::/20270c:efff:ffff:ffff:ffff:ffff:ffff:ffff
208270c:f000::/20270c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
209270d::/20270d:fff:ffff:ffff:ffff:ffff:ffff:ffff
210270d:1000::/20270d:1fff:ffff:ffff:ffff:ffff:ffff:ffff
211270d:2000::/20270d:2fff:ffff:ffff:ffff:ffff:ffff:ffff
212270d:3000::/20270d:3fff:ffff:ffff:ffff:ffff:ffff:ffff
213270d:4000::/20270d:4fff:ffff:ffff:ffff:ffff:ffff:ffff
214270d:5000::/20270d:5fff:ffff:ffff:ffff:ffff:ffff:ffff
215270d:6000::/20270d:6fff:ffff:ffff:ffff:ffff:ffff:ffff
216270d:7000::/20270d:7fff:ffff:ffff:ffff:ffff:ffff:ffff
217270d:8000::/20270d:8fff:ffff:ffff:ffff:ffff:ffff:ffff
218270d:9000::/20270d:9fff:ffff:ffff:ffff:ffff:ffff:ffff
219270d:a000::/20270d:afff:ffff:ffff:ffff:ffff:ffff:ffff
220270d:b000::/20270d:bfff:ffff:ffff:ffff:ffff:ffff:ffff
221270d:c000::/20270d:cfff:ffff:ffff:ffff:ffff:ffff:ffff
222270d:d000::/20270d:dfff:ffff:ffff:ffff:ffff:ffff:ffff
223270d:e000::/20270d:efff:ffff:ffff:ffff:ffff:ffff:ffff
224270d:f000::/20270d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
225270e::/20270e:fff:ffff:ffff:ffff:ffff:ffff:ffff
226270e:1000::/20270e:1fff:ffff:ffff:ffff:ffff:ffff:ffff
227270e:2000::/20270e:2fff:ffff:ffff:ffff:ffff:ffff:ffff
228270e:3000::/20270e:3fff:ffff:ffff:ffff:ffff:ffff:ffff
229270e:4000::/20270e:4fff:ffff:ffff:ffff:ffff:ffff:ffff
230270e:5000::/20270e:5fff:ffff:ffff:ffff:ffff:ffff:ffff
231270e:6000::/20270e:6fff:ffff:ffff:ffff:ffff:ffff:ffff
232270e:7000::/20270e:7fff:ffff:ffff:ffff:ffff:ffff:ffff
233270e:8000::/20270e:8fff:ffff:ffff:ffff:ffff:ffff:ffff
234270e:9000::/20270e:9fff:ffff:ffff:ffff:ffff:ffff:ffff
235270e:a000::/20270e:afff:ffff:ffff:ffff:ffff:ffff:ffff
236270e:b000::/20270e:bfff:ffff:ffff:ffff:ffff:ffff:ffff
237270e:c000::/20270e:cfff:ffff:ffff:ffff:ffff:ffff:ffff
238270e:d000::/20270e:dfff:ffff:ffff:ffff:ffff:ffff:ffff
239270e:e000::/20270e:efff:ffff:ffff:ffff:ffff:ffff:ffff
240270e:f000::/20270e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
241270f::/20270f:fff:ffff:ffff:ffff:ffff:ffff:ffff
242270f:1000::/20270f:1fff:ffff:ffff:ffff:ffff:ffff:ffff
243270f:2000::/20270f:2fff:ffff:ffff:ffff:ffff:ffff:ffff
244270f:3000::/20270f:3fff:ffff:ffff:ffff:ffff:ffff:ffff
245270f:4000::/20270f:4fff:ffff:ffff:ffff:ffff:ffff:ffff
246270f:5000::/20270f:5fff:ffff:ffff:ffff:ffff:ffff:ffff
247270f:6000::/20270f:6fff:ffff:ffff:ffff:ffff:ffff:ffff
248270f:7000::/20270f:7fff:ffff:ffff:ffff:ffff:ffff:ffff
249270f:8000::/20270f:8fff:ffff:ffff:ffff:ffff:ffff:ffff
250270f:9000::/20270f:9fff:ffff:ffff:ffff:ffff:ffff:ffff
251270f:a000::/20270f:afff:ffff:ffff:ffff:ffff:ffff:ffff
252270f:b000::/20270f:bfff:ffff:ffff:ffff:ffff:ffff:ffff
253270f:c000::/20270f:cfff:ffff:ffff:ffff:ffff:ffff:ffff
254270f:d000::/20270f:dfff:ffff:ffff:ffff:ffff:ffff:ffff
255270f:e000::/20270f:efff:ffff:ffff:ffff:ffff:ffff:ffff
256270f:f000::/20270f:ffff: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.