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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.

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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.

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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/12
Addresses2^116
/64 networks2^52
Network
2000::/12
First address
2000::
Last address
200f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
83,076,749,736,557,242,056,487,941,267,521,536 (2^116)
/64 networks (LANs)
4,503,599,627,370,496 (2^52)
Full form
2000:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
0.0.2.ip6.arpa
Split into smaller subnets/20
/13 (2)/14 (4)/15 (8)/16 (16)/20 (256)/24 (4,096)/28 (65,536)

2000::/12 makes 256 subnets of /20.

Subnets
#SubnetLast address
12000::/202000:fff:ffff:ffff:ffff:ffff:ffff:ffff
22000:1000::/202000:1fff:ffff:ffff:ffff:ffff:ffff:ffff
32000:2000::/202000:2fff:ffff:ffff:ffff:ffff:ffff:ffff
42000:3000::/202000:3fff:ffff:ffff:ffff:ffff:ffff:ffff
52000:4000::/202000:4fff:ffff:ffff:ffff:ffff:ffff:ffff
62000:5000::/202000:5fff:ffff:ffff:ffff:ffff:ffff:ffff
72000:6000::/202000:6fff:ffff:ffff:ffff:ffff:ffff:ffff
82000:7000::/202000:7fff:ffff:ffff:ffff:ffff:ffff:ffff
92000:8000::/202000:8fff:ffff:ffff:ffff:ffff:ffff:ffff
102000:9000::/202000:9fff:ffff:ffff:ffff:ffff:ffff:ffff
112000:a000::/202000:afff:ffff:ffff:ffff:ffff:ffff:ffff
122000:b000::/202000:bfff:ffff:ffff:ffff:ffff:ffff:ffff
132000:c000::/202000:cfff:ffff:ffff:ffff:ffff:ffff:ffff
142000:d000::/202000:dfff:ffff:ffff:ffff:ffff:ffff:ffff
152000:e000::/202000:efff:ffff:ffff:ffff:ffff:ffff:ffff
162000:f000::/202000:ffff:ffff:ffff:ffff:ffff:ffff:ffff
172001::/202001:fff:ffff:ffff:ffff:ffff:ffff:ffff
182001:1000::/202001:1fff:ffff:ffff:ffff:ffff:ffff:ffff
192001:2000::/202001:2fff:ffff:ffff:ffff:ffff:ffff:ffff
202001:3000::/202001:3fff:ffff:ffff:ffff:ffff:ffff:ffff
212001:4000::/202001:4fff:ffff:ffff:ffff:ffff:ffff:ffff
222001:5000::/202001:5fff:ffff:ffff:ffff:ffff:ffff:ffff
232001:6000::/202001:6fff:ffff:ffff:ffff:ffff:ffff:ffff
242001:7000::/202001:7fff:ffff:ffff:ffff:ffff:ffff:ffff
252001:8000::/202001:8fff:ffff:ffff:ffff:ffff:ffff:ffff
262001:9000::/202001:9fff:ffff:ffff:ffff:ffff:ffff:ffff
272001:a000::/202001:afff:ffff:ffff:ffff:ffff:ffff:ffff
282001:b000::/202001:bfff:ffff:ffff:ffff:ffff:ffff:ffff
292001:c000::/202001:cfff:ffff:ffff:ffff:ffff:ffff:ffff
302001:d000::/202001:dfff:ffff:ffff:ffff:ffff:ffff:ffff
312001:e000::/202001:efff:ffff:ffff:ffff:ffff:ffff:ffff
322001:f000::/202001:ffff:ffff:ffff:ffff:ffff:ffff:ffff
332002::/202002:fff:ffff:ffff:ffff:ffff:ffff:ffff
342002:1000::/202002:1fff:ffff:ffff:ffff:ffff:ffff:ffff
352002:2000::/202002:2fff:ffff:ffff:ffff:ffff:ffff:ffff
362002:3000::/202002:3fff:ffff:ffff:ffff:ffff:ffff:ffff
372002:4000::/202002:4fff:ffff:ffff:ffff:ffff:ffff:ffff
382002:5000::/202002:5fff:ffff:ffff:ffff:ffff:ffff:ffff
392002:6000::/202002:6fff:ffff:ffff:ffff:ffff:ffff:ffff
402002:7000::/202002:7fff:ffff:ffff:ffff:ffff:ffff:ffff
412002:8000::/202002:8fff:ffff:ffff:ffff:ffff:ffff:ffff
422002:9000::/202002:9fff:ffff:ffff:ffff:ffff:ffff:ffff
432002:a000::/202002:afff:ffff:ffff:ffff:ffff:ffff:ffff
442002:b000::/202002:bfff:ffff:ffff:ffff:ffff:ffff:ffff
452002:c000::/202002:cfff:ffff:ffff:ffff:ffff:ffff:ffff
462002:d000::/202002:dfff:ffff:ffff:ffff:ffff:ffff:ffff
472002:e000::/202002:efff:ffff:ffff:ffff:ffff:ffff:ffff
482002:f000::/202002:ffff:ffff:ffff:ffff:ffff:ffff:ffff
492003::/202003:fff:ffff:ffff:ffff:ffff:ffff:ffff
502003:1000::/202003:1fff:ffff:ffff:ffff:ffff:ffff:ffff
512003:2000::/202003:2fff:ffff:ffff:ffff:ffff:ffff:ffff
522003:3000::/202003:3fff:ffff:ffff:ffff:ffff:ffff:ffff
532003:4000::/202003:4fff:ffff:ffff:ffff:ffff:ffff:ffff
542003:5000::/202003:5fff:ffff:ffff:ffff:ffff:ffff:ffff
552003:6000::/202003:6fff:ffff:ffff:ffff:ffff:ffff:ffff
562003:7000::/202003:7fff:ffff:ffff:ffff:ffff:ffff:ffff
572003:8000::/202003:8fff:ffff:ffff:ffff:ffff:ffff:ffff
582003:9000::/202003:9fff:ffff:ffff:ffff:ffff:ffff:ffff
592003:a000::/202003:afff:ffff:ffff:ffff:ffff:ffff:ffff
602003:b000::/202003:bfff:ffff:ffff:ffff:ffff:ffff:ffff
612003:c000::/202003:cfff:ffff:ffff:ffff:ffff:ffff:ffff
622003:d000::/202003:dfff:ffff:ffff:ffff:ffff:ffff:ffff
632003:e000::/202003:efff:ffff:ffff:ffff:ffff:ffff:ffff
642003:f000::/202003:ffff:ffff:ffff:ffff:ffff:ffff:ffff
652004::/202004:fff:ffff:ffff:ffff:ffff:ffff:ffff
662004:1000::/202004:1fff:ffff:ffff:ffff:ffff:ffff:ffff
672004:2000::/202004:2fff:ffff:ffff:ffff:ffff:ffff:ffff
682004:3000::/202004:3fff:ffff:ffff:ffff:ffff:ffff:ffff
692004:4000::/202004:4fff:ffff:ffff:ffff:ffff:ffff:ffff
702004:5000::/202004:5fff:ffff:ffff:ffff:ffff:ffff:ffff
712004:6000::/202004:6fff:ffff:ffff:ffff:ffff:ffff:ffff
722004:7000::/202004:7fff:ffff:ffff:ffff:ffff:ffff:ffff
732004:8000::/202004:8fff:ffff:ffff:ffff:ffff:ffff:ffff
742004:9000::/202004:9fff:ffff:ffff:ffff:ffff:ffff:ffff
752004:a000::/202004:afff:ffff:ffff:ffff:ffff:ffff:ffff
762004:b000::/202004:bfff:ffff:ffff:ffff:ffff:ffff:ffff
772004:c000::/202004:cfff:ffff:ffff:ffff:ffff:ffff:ffff
782004:d000::/202004:dfff:ffff:ffff:ffff:ffff:ffff:ffff
792004:e000::/202004:efff:ffff:ffff:ffff:ffff:ffff:ffff
802004:f000::/202004:ffff:ffff:ffff:ffff:ffff:ffff:ffff
812005::/202005:fff:ffff:ffff:ffff:ffff:ffff:ffff
822005:1000::/202005:1fff:ffff:ffff:ffff:ffff:ffff:ffff
832005:2000::/202005:2fff:ffff:ffff:ffff:ffff:ffff:ffff
842005:3000::/202005:3fff:ffff:ffff:ffff:ffff:ffff:ffff
852005:4000::/202005:4fff:ffff:ffff:ffff:ffff:ffff:ffff
862005:5000::/202005:5fff:ffff:ffff:ffff:ffff:ffff:ffff
872005:6000::/202005:6fff:ffff:ffff:ffff:ffff:ffff:ffff
882005:7000::/202005:7fff:ffff:ffff:ffff:ffff:ffff:ffff
892005:8000::/202005:8fff:ffff:ffff:ffff:ffff:ffff:ffff
902005:9000::/202005:9fff:ffff:ffff:ffff:ffff:ffff:ffff
912005:a000::/202005:afff:ffff:ffff:ffff:ffff:ffff:ffff
922005:b000::/202005:bfff:ffff:ffff:ffff:ffff:ffff:ffff
932005:c000::/202005:cfff:ffff:ffff:ffff:ffff:ffff:ffff
942005:d000::/202005:dfff:ffff:ffff:ffff:ffff:ffff:ffff
952005:e000::/202005:efff:ffff:ffff:ffff:ffff:ffff:ffff
962005:f000::/202005:ffff:ffff:ffff:ffff:ffff:ffff:ffff
972006::/202006:fff:ffff:ffff:ffff:ffff:ffff:ffff
982006:1000::/202006:1fff:ffff:ffff:ffff:ffff:ffff:ffff
992006:2000::/202006:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1002006:3000::/202006:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1012006:4000::/202006:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1022006:5000::/202006:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1032006:6000::/202006:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1042006:7000::/202006:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1052006:8000::/202006:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1062006:9000::/202006:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1072006:a000::/202006:afff:ffff:ffff:ffff:ffff:ffff:ffff
1082006:b000::/202006:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1092006:c000::/202006:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1102006:d000::/202006:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1112006:e000::/202006:efff:ffff:ffff:ffff:ffff:ffff:ffff
1122006:f000::/202006:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1132007::/202007:fff:ffff:ffff:ffff:ffff:ffff:ffff
1142007:1000::/202007:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1152007:2000::/202007:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1162007:3000::/202007:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1172007:4000::/202007:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1182007:5000::/202007:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1192007:6000::/202007:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1202007:7000::/202007:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1212007:8000::/202007:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1222007:9000::/202007:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1232007:a000::/202007:afff:ffff:ffff:ffff:ffff:ffff:ffff
1242007:b000::/202007:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1252007:c000::/202007:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1262007:d000::/202007:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1272007:e000::/202007:efff:ffff:ffff:ffff:ffff:ffff:ffff
1282007:f000::/202007:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1292008::/202008:fff:ffff:ffff:ffff:ffff:ffff:ffff
1302008:1000::/202008:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1312008:2000::/202008:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1322008:3000::/202008:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1332008:4000::/202008:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1342008:5000::/202008:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1352008:6000::/202008:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1362008:7000::/202008:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1372008:8000::/202008:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1382008:9000::/202008:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1392008:a000::/202008:afff:ffff:ffff:ffff:ffff:ffff:ffff
1402008:b000::/202008:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1412008:c000::/202008:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1422008:d000::/202008:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1432008:e000::/202008:efff:ffff:ffff:ffff:ffff:ffff:ffff
1442008:f000::/202008:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1452009::/202009:fff:ffff:ffff:ffff:ffff:ffff:ffff
1462009:1000::/202009:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1472009:2000::/202009:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1482009:3000::/202009:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1492009:4000::/202009:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1502009:5000::/202009:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1512009:6000::/202009:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1522009:7000::/202009:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1532009:8000::/202009:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1542009:9000::/202009:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1552009:a000::/202009:afff:ffff:ffff:ffff:ffff:ffff:ffff
1562009:b000::/202009:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1572009:c000::/202009:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1582009:d000::/202009:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1592009:e000::/202009:efff:ffff:ffff:ffff:ffff:ffff:ffff
1602009:f000::/202009:ffff:ffff:ffff:ffff:ffff:ffff:ffff
161200a::/20200a:fff:ffff:ffff:ffff:ffff:ffff:ffff
162200a:1000::/20200a:1fff:ffff:ffff:ffff:ffff:ffff:ffff
163200a:2000::/20200a:2fff:ffff:ffff:ffff:ffff:ffff:ffff
164200a:3000::/20200a:3fff:ffff:ffff:ffff:ffff:ffff:ffff
165200a:4000::/20200a:4fff:ffff:ffff:ffff:ffff:ffff:ffff
166200a:5000::/20200a:5fff:ffff:ffff:ffff:ffff:ffff:ffff
167200a:6000::/20200a:6fff:ffff:ffff:ffff:ffff:ffff:ffff
168200a:7000::/20200a:7fff:ffff:ffff:ffff:ffff:ffff:ffff
169200a:8000::/20200a:8fff:ffff:ffff:ffff:ffff:ffff:ffff
170200a:9000::/20200a:9fff:ffff:ffff:ffff:ffff:ffff:ffff
171200a:a000::/20200a:afff:ffff:ffff:ffff:ffff:ffff:ffff
172200a:b000::/20200a:bfff:ffff:ffff:ffff:ffff:ffff:ffff
173200a:c000::/20200a:cfff:ffff:ffff:ffff:ffff:ffff:ffff
174200a:d000::/20200a:dfff:ffff:ffff:ffff:ffff:ffff:ffff
175200a:e000::/20200a:efff:ffff:ffff:ffff:ffff:ffff:ffff
176200a:f000::/20200a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
177200b::/20200b:fff:ffff:ffff:ffff:ffff:ffff:ffff
178200b:1000::/20200b:1fff:ffff:ffff:ffff:ffff:ffff:ffff
179200b:2000::/20200b:2fff:ffff:ffff:ffff:ffff:ffff:ffff
180200b:3000::/20200b:3fff:ffff:ffff:ffff:ffff:ffff:ffff
181200b:4000::/20200b:4fff:ffff:ffff:ffff:ffff:ffff:ffff
182200b:5000::/20200b:5fff:ffff:ffff:ffff:ffff:ffff:ffff
183200b:6000::/20200b:6fff:ffff:ffff:ffff:ffff:ffff:ffff
184200b:7000::/20200b:7fff:ffff:ffff:ffff:ffff:ffff:ffff
185200b:8000::/20200b:8fff:ffff:ffff:ffff:ffff:ffff:ffff
186200b:9000::/20200b:9fff:ffff:ffff:ffff:ffff:ffff:ffff
187200b:a000::/20200b:afff:ffff:ffff:ffff:ffff:ffff:ffff
188200b:b000::/20200b:bfff:ffff:ffff:ffff:ffff:ffff:ffff
189200b:c000::/20200b:cfff:ffff:ffff:ffff:ffff:ffff:ffff
190200b:d000::/20200b:dfff:ffff:ffff:ffff:ffff:ffff:ffff
191200b:e000::/20200b:efff:ffff:ffff:ffff:ffff:ffff:ffff
192200b:f000::/20200b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
193200c::/20200c:fff:ffff:ffff:ffff:ffff:ffff:ffff
194200c:1000::/20200c:1fff:ffff:ffff:ffff:ffff:ffff:ffff
195200c:2000::/20200c:2fff:ffff:ffff:ffff:ffff:ffff:ffff
196200c:3000::/20200c:3fff:ffff:ffff:ffff:ffff:ffff:ffff
197200c:4000::/20200c:4fff:ffff:ffff:ffff:ffff:ffff:ffff
198200c:5000::/20200c:5fff:ffff:ffff:ffff:ffff:ffff:ffff
199200c:6000::/20200c:6fff:ffff:ffff:ffff:ffff:ffff:ffff
200200c:7000::/20200c:7fff:ffff:ffff:ffff:ffff:ffff:ffff
201200c:8000::/20200c:8fff:ffff:ffff:ffff:ffff:ffff:ffff
202200c:9000::/20200c:9fff:ffff:ffff:ffff:ffff:ffff:ffff
203200c:a000::/20200c:afff:ffff:ffff:ffff:ffff:ffff:ffff
204200c:b000::/20200c:bfff:ffff:ffff:ffff:ffff:ffff:ffff
205200c:c000::/20200c:cfff:ffff:ffff:ffff:ffff:ffff:ffff
206200c:d000::/20200c:dfff:ffff:ffff:ffff:ffff:ffff:ffff
207200c:e000::/20200c:efff:ffff:ffff:ffff:ffff:ffff:ffff
208200c:f000::/20200c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
209200d::/20200d:fff:ffff:ffff:ffff:ffff:ffff:ffff
210200d:1000::/20200d:1fff:ffff:ffff:ffff:ffff:ffff:ffff
211200d:2000::/20200d:2fff:ffff:ffff:ffff:ffff:ffff:ffff
212200d:3000::/20200d:3fff:ffff:ffff:ffff:ffff:ffff:ffff
213200d:4000::/20200d:4fff:ffff:ffff:ffff:ffff:ffff:ffff
214200d:5000::/20200d:5fff:ffff:ffff:ffff:ffff:ffff:ffff
215200d:6000::/20200d:6fff:ffff:ffff:ffff:ffff:ffff:ffff
216200d:7000::/20200d:7fff:ffff:ffff:ffff:ffff:ffff:ffff
217200d:8000::/20200d:8fff:ffff:ffff:ffff:ffff:ffff:ffff
218200d:9000::/20200d:9fff:ffff:ffff:ffff:ffff:ffff:ffff
219200d:a000::/20200d:afff:ffff:ffff:ffff:ffff:ffff:ffff
220200d:b000::/20200d:bfff:ffff:ffff:ffff:ffff:ffff:ffff
221200d:c000::/20200d:cfff:ffff:ffff:ffff:ffff:ffff:ffff
222200d:d000::/20200d:dfff:ffff:ffff:ffff:ffff:ffff:ffff
223200d:e000::/20200d:efff:ffff:ffff:ffff:ffff:ffff:ffff
224200d:f000::/20200d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
225200e::/20200e:fff:ffff:ffff:ffff:ffff:ffff:ffff
226200e:1000::/20200e:1fff:ffff:ffff:ffff:ffff:ffff:ffff
227200e:2000::/20200e:2fff:ffff:ffff:ffff:ffff:ffff:ffff
228200e:3000::/20200e:3fff:ffff:ffff:ffff:ffff:ffff:ffff
229200e:4000::/20200e:4fff:ffff:ffff:ffff:ffff:ffff:ffff
230200e:5000::/20200e:5fff:ffff:ffff:ffff:ffff:ffff:ffff
231200e:6000::/20200e:6fff:ffff:ffff:ffff:ffff:ffff:ffff
232200e:7000::/20200e:7fff:ffff:ffff:ffff:ffff:ffff:ffff
233200e:8000::/20200e:8fff:ffff:ffff:ffff:ffff:ffff:ffff
234200e:9000::/20200e:9fff:ffff:ffff:ffff:ffff:ffff:ffff
235200e:a000::/20200e:afff:ffff:ffff:ffff:ffff:ffff:ffff
236200e:b000::/20200e:bfff:ffff:ffff:ffff:ffff:ffff:ffff
237200e:c000::/20200e:cfff:ffff:ffff:ffff:ffff:ffff:ffff
238200e:d000::/20200e:dfff:ffff:ffff:ffff:ffff:ffff:ffff
239200e:e000::/20200e:efff:ffff:ffff:ffff:ffff:ffff:ffff
240200e:f000::/20200e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
241200f::/20200f:fff:ffff:ffff:ffff:ffff:ffff:ffff
242200f:1000::/20200f:1fff:ffff:ffff:ffff:ffff:ffff:ffff
243200f:2000::/20200f:2fff:ffff:ffff:ffff:ffff:ffff:ffff
244200f:3000::/20200f:3fff:ffff:ffff:ffff:ffff:ffff:ffff
245200f:4000::/20200f:4fff:ffff:ffff:ffff:ffff:ffff:ffff
246200f:5000::/20200f:5fff:ffff:ffff:ffff:ffff:ffff:ffff
247200f:6000::/20200f:6fff:ffff:ffff:ffff:ffff:ffff:ffff
248200f:7000::/20200f:7fff:ffff:ffff:ffff:ffff:ffff:ffff
249200f:8000::/20200f:8fff:ffff:ffff:ffff:ffff:ffff:ffff
250200f:9000::/20200f:9fff:ffff:ffff:ffff:ffff:ffff:ffff
251200f:a000::/20200f:afff:ffff:ffff:ffff:ffff:ffff:ffff
252200f:b000::/20200f:bfff:ffff:ffff:ffff:ffff:ffff:ffff
253200f:c000::/20200f:cfff:ffff:ffff:ffff:ffff:ffff:ffff
254200f:d000::/20200f:dfff:ffff:ffff:ffff:ffff:ffff:ffff
255200f:e000::/20200f:efff:ffff:ffff:ffff:ffff:ffff:ffff
256200f:f000::/20200f: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.