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/7
Addresses2^121
/64 networks2^57
Network
3400::/7
First address
3400::
Last address
35ff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
2,658,455,991,569,831,745,807,614,120,560,689,152 (2^121)
/64 networks (LANs)
144,115,188,075,855,872 (2^57)
Full form
3400:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zones
4.3.ip6.arpa
5.3.ip6.arpa
/7 is not on a 4-bit boundary, so it takes 2 /8 zones.
Split into smaller subnets/20
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/16 (512)/20 (8,192)

3400::/7 makes 8,192 subnets of /20; the first 256 are listed.

Subnets
#SubnetLast address
13400::/203400:fff:ffff:ffff:ffff:ffff:ffff:ffff
23400:1000::/203400:1fff:ffff:ffff:ffff:ffff:ffff:ffff
33400:2000::/203400:2fff:ffff:ffff:ffff:ffff:ffff:ffff
43400:3000::/203400:3fff:ffff:ffff:ffff:ffff:ffff:ffff
53400:4000::/203400:4fff:ffff:ffff:ffff:ffff:ffff:ffff
63400:5000::/203400:5fff:ffff:ffff:ffff:ffff:ffff:ffff
73400:6000::/203400:6fff:ffff:ffff:ffff:ffff:ffff:ffff
83400:7000::/203400:7fff:ffff:ffff:ffff:ffff:ffff:ffff
93400:8000::/203400:8fff:ffff:ffff:ffff:ffff:ffff:ffff
103400:9000::/203400:9fff:ffff:ffff:ffff:ffff:ffff:ffff
113400:a000::/203400:afff:ffff:ffff:ffff:ffff:ffff:ffff
123400:b000::/203400:bfff:ffff:ffff:ffff:ffff:ffff:ffff
133400:c000::/203400:cfff:ffff:ffff:ffff:ffff:ffff:ffff
143400:d000::/203400:dfff:ffff:ffff:ffff:ffff:ffff:ffff
153400:e000::/203400:efff:ffff:ffff:ffff:ffff:ffff:ffff
163400:f000::/203400:ffff:ffff:ffff:ffff:ffff:ffff:ffff
173401::/203401:fff:ffff:ffff:ffff:ffff:ffff:ffff
183401:1000::/203401:1fff:ffff:ffff:ffff:ffff:ffff:ffff
193401:2000::/203401:2fff:ffff:ffff:ffff:ffff:ffff:ffff
203401:3000::/203401:3fff:ffff:ffff:ffff:ffff:ffff:ffff
213401:4000::/203401:4fff:ffff:ffff:ffff:ffff:ffff:ffff
223401:5000::/203401:5fff:ffff:ffff:ffff:ffff:ffff:ffff
233401:6000::/203401:6fff:ffff:ffff:ffff:ffff:ffff:ffff
243401:7000::/203401:7fff:ffff:ffff:ffff:ffff:ffff:ffff
253401:8000::/203401:8fff:ffff:ffff:ffff:ffff:ffff:ffff
263401:9000::/203401:9fff:ffff:ffff:ffff:ffff:ffff:ffff
273401:a000::/203401:afff:ffff:ffff:ffff:ffff:ffff:ffff
283401:b000::/203401:bfff:ffff:ffff:ffff:ffff:ffff:ffff
293401:c000::/203401:cfff:ffff:ffff:ffff:ffff:ffff:ffff
303401:d000::/203401:dfff:ffff:ffff:ffff:ffff:ffff:ffff
313401:e000::/203401:efff:ffff:ffff:ffff:ffff:ffff:ffff
323401:f000::/203401:ffff:ffff:ffff:ffff:ffff:ffff:ffff
333402::/203402:fff:ffff:ffff:ffff:ffff:ffff:ffff
343402:1000::/203402:1fff:ffff:ffff:ffff:ffff:ffff:ffff
353402:2000::/203402:2fff:ffff:ffff:ffff:ffff:ffff:ffff
363402:3000::/203402:3fff:ffff:ffff:ffff:ffff:ffff:ffff
373402:4000::/203402:4fff:ffff:ffff:ffff:ffff:ffff:ffff
383402:5000::/203402:5fff:ffff:ffff:ffff:ffff:ffff:ffff
393402:6000::/203402:6fff:ffff:ffff:ffff:ffff:ffff:ffff
403402:7000::/203402:7fff:ffff:ffff:ffff:ffff:ffff:ffff
413402:8000::/203402:8fff:ffff:ffff:ffff:ffff:ffff:ffff
423402:9000::/203402:9fff:ffff:ffff:ffff:ffff:ffff:ffff
433402:a000::/203402:afff:ffff:ffff:ffff:ffff:ffff:ffff
443402:b000::/203402:bfff:ffff:ffff:ffff:ffff:ffff:ffff
453402:c000::/203402:cfff:ffff:ffff:ffff:ffff:ffff:ffff
463402:d000::/203402:dfff:ffff:ffff:ffff:ffff:ffff:ffff
473402:e000::/203402:efff:ffff:ffff:ffff:ffff:ffff:ffff
483402:f000::/203402:ffff:ffff:ffff:ffff:ffff:ffff:ffff
493403::/203403:fff:ffff:ffff:ffff:ffff:ffff:ffff
503403:1000::/203403:1fff:ffff:ffff:ffff:ffff:ffff:ffff
513403:2000::/203403:2fff:ffff:ffff:ffff:ffff:ffff:ffff
523403:3000::/203403:3fff:ffff:ffff:ffff:ffff:ffff:ffff
533403:4000::/203403:4fff:ffff:ffff:ffff:ffff:ffff:ffff
543403:5000::/203403:5fff:ffff:ffff:ffff:ffff:ffff:ffff
553403:6000::/203403:6fff:ffff:ffff:ffff:ffff:ffff:ffff
563403:7000::/203403:7fff:ffff:ffff:ffff:ffff:ffff:ffff
573403:8000::/203403:8fff:ffff:ffff:ffff:ffff:ffff:ffff
583403:9000::/203403:9fff:ffff:ffff:ffff:ffff:ffff:ffff
593403:a000::/203403:afff:ffff:ffff:ffff:ffff:ffff:ffff
603403:b000::/203403:bfff:ffff:ffff:ffff:ffff:ffff:ffff
613403:c000::/203403:cfff:ffff:ffff:ffff:ffff:ffff:ffff
623403:d000::/203403:dfff:ffff:ffff:ffff:ffff:ffff:ffff
633403:e000::/203403:efff:ffff:ffff:ffff:ffff:ffff:ffff
643403:f000::/203403:ffff:ffff:ffff:ffff:ffff:ffff:ffff
653404::/203404:fff:ffff:ffff:ffff:ffff:ffff:ffff
663404:1000::/203404:1fff:ffff:ffff:ffff:ffff:ffff:ffff
673404:2000::/203404:2fff:ffff:ffff:ffff:ffff:ffff:ffff
683404:3000::/203404:3fff:ffff:ffff:ffff:ffff:ffff:ffff
693404:4000::/203404:4fff:ffff:ffff:ffff:ffff:ffff:ffff
703404:5000::/203404:5fff:ffff:ffff:ffff:ffff:ffff:ffff
713404:6000::/203404:6fff:ffff:ffff:ffff:ffff:ffff:ffff
723404:7000::/203404:7fff:ffff:ffff:ffff:ffff:ffff:ffff
733404:8000::/203404:8fff:ffff:ffff:ffff:ffff:ffff:ffff
743404:9000::/203404:9fff:ffff:ffff:ffff:ffff:ffff:ffff
753404:a000::/203404:afff:ffff:ffff:ffff:ffff:ffff:ffff
763404:b000::/203404:bfff:ffff:ffff:ffff:ffff:ffff:ffff
773404:c000::/203404:cfff:ffff:ffff:ffff:ffff:ffff:ffff
783404:d000::/203404:dfff:ffff:ffff:ffff:ffff:ffff:ffff
793404:e000::/203404:efff:ffff:ffff:ffff:ffff:ffff:ffff
803404:f000::/203404:ffff:ffff:ffff:ffff:ffff:ffff:ffff
813405::/203405:fff:ffff:ffff:ffff:ffff:ffff:ffff
823405:1000::/203405:1fff:ffff:ffff:ffff:ffff:ffff:ffff
833405:2000::/203405:2fff:ffff:ffff:ffff:ffff:ffff:ffff
843405:3000::/203405:3fff:ffff:ffff:ffff:ffff:ffff:ffff
853405:4000::/203405:4fff:ffff:ffff:ffff:ffff:ffff:ffff
863405:5000::/203405:5fff:ffff:ffff:ffff:ffff:ffff:ffff
873405:6000::/203405:6fff:ffff:ffff:ffff:ffff:ffff:ffff
883405:7000::/203405:7fff:ffff:ffff:ffff:ffff:ffff:ffff
893405:8000::/203405:8fff:ffff:ffff:ffff:ffff:ffff:ffff
903405:9000::/203405:9fff:ffff:ffff:ffff:ffff:ffff:ffff
913405:a000::/203405:afff:ffff:ffff:ffff:ffff:ffff:ffff
923405:b000::/203405:bfff:ffff:ffff:ffff:ffff:ffff:ffff
933405:c000::/203405:cfff:ffff:ffff:ffff:ffff:ffff:ffff
943405:d000::/203405:dfff:ffff:ffff:ffff:ffff:ffff:ffff
953405:e000::/203405:efff:ffff:ffff:ffff:ffff:ffff:ffff
963405:f000::/203405:ffff:ffff:ffff:ffff:ffff:ffff:ffff
973406::/203406:fff:ffff:ffff:ffff:ffff:ffff:ffff
983406:1000::/203406:1fff:ffff:ffff:ffff:ffff:ffff:ffff
993406:2000::/203406:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1003406:3000::/203406:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1013406:4000::/203406:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1023406:5000::/203406:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1033406:6000::/203406:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1043406:7000::/203406:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1053406:8000::/203406:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1063406:9000::/203406:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1073406:a000::/203406:afff:ffff:ffff:ffff:ffff:ffff:ffff
1083406:b000::/203406:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1093406:c000::/203406:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1103406:d000::/203406:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1113406:e000::/203406:efff:ffff:ffff:ffff:ffff:ffff:ffff
1123406:f000::/203406:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1133407::/203407:fff:ffff:ffff:ffff:ffff:ffff:ffff
1143407:1000::/203407:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1153407:2000::/203407:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1163407:3000::/203407:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1173407:4000::/203407:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1183407:5000::/203407:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1193407:6000::/203407:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1203407:7000::/203407:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1213407:8000::/203407:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1223407:9000::/203407:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1233407:a000::/203407:afff:ffff:ffff:ffff:ffff:ffff:ffff
1243407:b000::/203407:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1253407:c000::/203407:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1263407:d000::/203407:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1273407:e000::/203407:efff:ffff:ffff:ffff:ffff:ffff:ffff
1283407:f000::/203407:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1293408::/203408:fff:ffff:ffff:ffff:ffff:ffff:ffff
1303408:1000::/203408:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1313408:2000::/203408:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1323408:3000::/203408:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1333408:4000::/203408:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1343408:5000::/203408:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1353408:6000::/203408:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1363408:7000::/203408:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1373408:8000::/203408:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1383408:9000::/203408:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1393408:a000::/203408:afff:ffff:ffff:ffff:ffff:ffff:ffff
1403408:b000::/203408:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1413408:c000::/203408:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1423408:d000::/203408:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1433408:e000::/203408:efff:ffff:ffff:ffff:ffff:ffff:ffff
1443408:f000::/203408:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1453409::/203409:fff:ffff:ffff:ffff:ffff:ffff:ffff
1463409:1000::/203409:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1473409:2000::/203409:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1483409:3000::/203409:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1493409:4000::/203409:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1503409:5000::/203409:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1513409:6000::/203409:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1523409:7000::/203409:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1533409:8000::/203409:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1543409:9000::/203409:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1553409:a000::/203409:afff:ffff:ffff:ffff:ffff:ffff:ffff
1563409:b000::/203409:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1573409:c000::/203409:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1583409:d000::/203409:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1593409:e000::/203409:efff:ffff:ffff:ffff:ffff:ffff:ffff
1603409:f000::/203409:ffff:ffff:ffff:ffff:ffff:ffff:ffff
161340a::/20340a:fff:ffff:ffff:ffff:ffff:ffff:ffff
162340a:1000::/20340a:1fff:ffff:ffff:ffff:ffff:ffff:ffff
163340a:2000::/20340a:2fff:ffff:ffff:ffff:ffff:ffff:ffff
164340a:3000::/20340a:3fff:ffff:ffff:ffff:ffff:ffff:ffff
165340a:4000::/20340a:4fff:ffff:ffff:ffff:ffff:ffff:ffff
166340a:5000::/20340a:5fff:ffff:ffff:ffff:ffff:ffff:ffff
167340a:6000::/20340a:6fff:ffff:ffff:ffff:ffff:ffff:ffff
168340a:7000::/20340a:7fff:ffff:ffff:ffff:ffff:ffff:ffff
169340a:8000::/20340a:8fff:ffff:ffff:ffff:ffff:ffff:ffff
170340a:9000::/20340a:9fff:ffff:ffff:ffff:ffff:ffff:ffff
171340a:a000::/20340a:afff:ffff:ffff:ffff:ffff:ffff:ffff
172340a:b000::/20340a:bfff:ffff:ffff:ffff:ffff:ffff:ffff
173340a:c000::/20340a:cfff:ffff:ffff:ffff:ffff:ffff:ffff
174340a:d000::/20340a:dfff:ffff:ffff:ffff:ffff:ffff:ffff
175340a:e000::/20340a:efff:ffff:ffff:ffff:ffff:ffff:ffff
176340a:f000::/20340a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
177340b::/20340b:fff:ffff:ffff:ffff:ffff:ffff:ffff
178340b:1000::/20340b:1fff:ffff:ffff:ffff:ffff:ffff:ffff
179340b:2000::/20340b:2fff:ffff:ffff:ffff:ffff:ffff:ffff
180340b:3000::/20340b:3fff:ffff:ffff:ffff:ffff:ffff:ffff
181340b:4000::/20340b:4fff:ffff:ffff:ffff:ffff:ffff:ffff
182340b:5000::/20340b:5fff:ffff:ffff:ffff:ffff:ffff:ffff
183340b:6000::/20340b:6fff:ffff:ffff:ffff:ffff:ffff:ffff
184340b:7000::/20340b:7fff:ffff:ffff:ffff:ffff:ffff:ffff
185340b:8000::/20340b:8fff:ffff:ffff:ffff:ffff:ffff:ffff
186340b:9000::/20340b:9fff:ffff:ffff:ffff:ffff:ffff:ffff
187340b:a000::/20340b:afff:ffff:ffff:ffff:ffff:ffff:ffff
188340b:b000::/20340b:bfff:ffff:ffff:ffff:ffff:ffff:ffff
189340b:c000::/20340b:cfff:ffff:ffff:ffff:ffff:ffff:ffff
190340b:d000::/20340b:dfff:ffff:ffff:ffff:ffff:ffff:ffff
191340b:e000::/20340b:efff:ffff:ffff:ffff:ffff:ffff:ffff
192340b:f000::/20340b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
193340c::/20340c:fff:ffff:ffff:ffff:ffff:ffff:ffff
194340c:1000::/20340c:1fff:ffff:ffff:ffff:ffff:ffff:ffff
195340c:2000::/20340c:2fff:ffff:ffff:ffff:ffff:ffff:ffff
196340c:3000::/20340c:3fff:ffff:ffff:ffff:ffff:ffff:ffff
197340c:4000::/20340c:4fff:ffff:ffff:ffff:ffff:ffff:ffff
198340c:5000::/20340c:5fff:ffff:ffff:ffff:ffff:ffff:ffff
199340c:6000::/20340c:6fff:ffff:ffff:ffff:ffff:ffff:ffff
200340c:7000::/20340c:7fff:ffff:ffff:ffff:ffff:ffff:ffff
201340c:8000::/20340c:8fff:ffff:ffff:ffff:ffff:ffff:ffff
202340c:9000::/20340c:9fff:ffff:ffff:ffff:ffff:ffff:ffff
203340c:a000::/20340c:afff:ffff:ffff:ffff:ffff:ffff:ffff
204340c:b000::/20340c:bfff:ffff:ffff:ffff:ffff:ffff:ffff
205340c:c000::/20340c:cfff:ffff:ffff:ffff:ffff:ffff:ffff
206340c:d000::/20340c:dfff:ffff:ffff:ffff:ffff:ffff:ffff
207340c:e000::/20340c:efff:ffff:ffff:ffff:ffff:ffff:ffff
208340c:f000::/20340c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
209340d::/20340d:fff:ffff:ffff:ffff:ffff:ffff:ffff
210340d:1000::/20340d:1fff:ffff:ffff:ffff:ffff:ffff:ffff
211340d:2000::/20340d:2fff:ffff:ffff:ffff:ffff:ffff:ffff
212340d:3000::/20340d:3fff:ffff:ffff:ffff:ffff:ffff:ffff
213340d:4000::/20340d:4fff:ffff:ffff:ffff:ffff:ffff:ffff
214340d:5000::/20340d:5fff:ffff:ffff:ffff:ffff:ffff:ffff
215340d:6000::/20340d:6fff:ffff:ffff:ffff:ffff:ffff:ffff
216340d:7000::/20340d:7fff:ffff:ffff:ffff:ffff:ffff:ffff
217340d:8000::/20340d:8fff:ffff:ffff:ffff:ffff:ffff:ffff
218340d:9000::/20340d:9fff:ffff:ffff:ffff:ffff:ffff:ffff
219340d:a000::/20340d:afff:ffff:ffff:ffff:ffff:ffff:ffff
220340d:b000::/20340d:bfff:ffff:ffff:ffff:ffff:ffff:ffff
221340d:c000::/20340d:cfff:ffff:ffff:ffff:ffff:ffff:ffff
222340d:d000::/20340d:dfff:ffff:ffff:ffff:ffff:ffff:ffff
223340d:e000::/20340d:efff:ffff:ffff:ffff:ffff:ffff:ffff
224340d:f000::/20340d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
225340e::/20340e:fff:ffff:ffff:ffff:ffff:ffff:ffff
226340e:1000::/20340e:1fff:ffff:ffff:ffff:ffff:ffff:ffff
227340e:2000::/20340e:2fff:ffff:ffff:ffff:ffff:ffff:ffff
228340e:3000::/20340e:3fff:ffff:ffff:ffff:ffff:ffff:ffff
229340e:4000::/20340e:4fff:ffff:ffff:ffff:ffff:ffff:ffff
230340e:5000::/20340e:5fff:ffff:ffff:ffff:ffff:ffff:ffff
231340e:6000::/20340e:6fff:ffff:ffff:ffff:ffff:ffff:ffff
232340e:7000::/20340e:7fff:ffff:ffff:ffff:ffff:ffff:ffff
233340e:8000::/20340e:8fff:ffff:ffff:ffff:ffff:ffff:ffff
234340e:9000::/20340e:9fff:ffff:ffff:ffff:ffff:ffff:ffff
235340e:a000::/20340e:afff:ffff:ffff:ffff:ffff:ffff:ffff
236340e:b000::/20340e:bfff:ffff:ffff:ffff:ffff:ffff:ffff
237340e:c000::/20340e:cfff:ffff:ffff:ffff:ffff:ffff:ffff
238340e:d000::/20340e:dfff:ffff:ffff:ffff:ffff:ffff:ffff
239340e:e000::/20340e:efff:ffff:ffff:ffff:ffff:ffff:ffff
240340e:f000::/20340e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
241340f::/20340f:fff:ffff:ffff:ffff:ffff:ffff:ffff
242340f:1000::/20340f:1fff:ffff:ffff:ffff:ffff:ffff:ffff
243340f:2000::/20340f:2fff:ffff:ffff:ffff:ffff:ffff:ffff
244340f:3000::/20340f:3fff:ffff:ffff:ffff:ffff:ffff:ffff
245340f:4000::/20340f:4fff:ffff:ffff:ffff:ffff:ffff:ffff
246340f:5000::/20340f:5fff:ffff:ffff:ffff:ffff:ffff:ffff
247340f:6000::/20340f:6fff:ffff:ffff:ffff:ffff:ffff:ffff
248340f:7000::/20340f:7fff:ffff:ffff:ffff:ffff:ffff:ffff
249340f:8000::/20340f:8fff:ffff:ffff:ffff:ffff:ffff:ffff
250340f:9000::/20340f:9fff:ffff:ffff:ffff:ffff:ffff:ffff
251340f:a000::/20340f:afff:ffff:ffff:ffff:ffff:ffff:ffff
252340f:b000::/20340f:bfff:ffff:ffff:ffff:ffff:ffff:ffff
253340f:c000::/20340f:cfff:ffff:ffff:ffff:ffff:ffff:ffff
254340f:d000::/20340f:dfff:ffff:ffff:ffff:ffff:ffff:ffff
255340f:e000::/20340f:efff:ffff:ffff:ffff:ffff:ffff:ffff
256340f:f000::/20340f: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.