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
3200::/7
First address
3200::
Last address
33ff: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
3200:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zones
2.3.ip6.arpa
3.3.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)

3200::/7 makes 8,192 subnets of /20; the first 256 are listed.

Subnets
#SubnetLast address
13200::/203200:fff:ffff:ffff:ffff:ffff:ffff:ffff
23200:1000::/203200:1fff:ffff:ffff:ffff:ffff:ffff:ffff
33200:2000::/203200:2fff:ffff:ffff:ffff:ffff:ffff:ffff
43200:3000::/203200:3fff:ffff:ffff:ffff:ffff:ffff:ffff
53200:4000::/203200:4fff:ffff:ffff:ffff:ffff:ffff:ffff
63200:5000::/203200:5fff:ffff:ffff:ffff:ffff:ffff:ffff
73200:6000::/203200:6fff:ffff:ffff:ffff:ffff:ffff:ffff
83200:7000::/203200:7fff:ffff:ffff:ffff:ffff:ffff:ffff
93200:8000::/203200:8fff:ffff:ffff:ffff:ffff:ffff:ffff
103200:9000::/203200:9fff:ffff:ffff:ffff:ffff:ffff:ffff
113200:a000::/203200:afff:ffff:ffff:ffff:ffff:ffff:ffff
123200:b000::/203200:bfff:ffff:ffff:ffff:ffff:ffff:ffff
133200:c000::/203200:cfff:ffff:ffff:ffff:ffff:ffff:ffff
143200:d000::/203200:dfff:ffff:ffff:ffff:ffff:ffff:ffff
153200:e000::/203200:efff:ffff:ffff:ffff:ffff:ffff:ffff
163200:f000::/203200:ffff:ffff:ffff:ffff:ffff:ffff:ffff
173201::/203201:fff:ffff:ffff:ffff:ffff:ffff:ffff
183201:1000::/203201:1fff:ffff:ffff:ffff:ffff:ffff:ffff
193201:2000::/203201:2fff:ffff:ffff:ffff:ffff:ffff:ffff
203201:3000::/203201:3fff:ffff:ffff:ffff:ffff:ffff:ffff
213201:4000::/203201:4fff:ffff:ffff:ffff:ffff:ffff:ffff
223201:5000::/203201:5fff:ffff:ffff:ffff:ffff:ffff:ffff
233201:6000::/203201:6fff:ffff:ffff:ffff:ffff:ffff:ffff
243201:7000::/203201:7fff:ffff:ffff:ffff:ffff:ffff:ffff
253201:8000::/203201:8fff:ffff:ffff:ffff:ffff:ffff:ffff
263201:9000::/203201:9fff:ffff:ffff:ffff:ffff:ffff:ffff
273201:a000::/203201:afff:ffff:ffff:ffff:ffff:ffff:ffff
283201:b000::/203201:bfff:ffff:ffff:ffff:ffff:ffff:ffff
293201:c000::/203201:cfff:ffff:ffff:ffff:ffff:ffff:ffff
303201:d000::/203201:dfff:ffff:ffff:ffff:ffff:ffff:ffff
313201:e000::/203201:efff:ffff:ffff:ffff:ffff:ffff:ffff
323201:f000::/203201:ffff:ffff:ffff:ffff:ffff:ffff:ffff
333202::/203202:fff:ffff:ffff:ffff:ffff:ffff:ffff
343202:1000::/203202:1fff:ffff:ffff:ffff:ffff:ffff:ffff
353202:2000::/203202:2fff:ffff:ffff:ffff:ffff:ffff:ffff
363202:3000::/203202:3fff:ffff:ffff:ffff:ffff:ffff:ffff
373202:4000::/203202:4fff:ffff:ffff:ffff:ffff:ffff:ffff
383202:5000::/203202:5fff:ffff:ffff:ffff:ffff:ffff:ffff
393202:6000::/203202:6fff:ffff:ffff:ffff:ffff:ffff:ffff
403202:7000::/203202:7fff:ffff:ffff:ffff:ffff:ffff:ffff
413202:8000::/203202:8fff:ffff:ffff:ffff:ffff:ffff:ffff
423202:9000::/203202:9fff:ffff:ffff:ffff:ffff:ffff:ffff
433202:a000::/203202:afff:ffff:ffff:ffff:ffff:ffff:ffff
443202:b000::/203202:bfff:ffff:ffff:ffff:ffff:ffff:ffff
453202:c000::/203202:cfff:ffff:ffff:ffff:ffff:ffff:ffff
463202:d000::/203202:dfff:ffff:ffff:ffff:ffff:ffff:ffff
473202:e000::/203202:efff:ffff:ffff:ffff:ffff:ffff:ffff
483202:f000::/203202:ffff:ffff:ffff:ffff:ffff:ffff:ffff
493203::/203203:fff:ffff:ffff:ffff:ffff:ffff:ffff
503203:1000::/203203:1fff:ffff:ffff:ffff:ffff:ffff:ffff
513203:2000::/203203:2fff:ffff:ffff:ffff:ffff:ffff:ffff
523203:3000::/203203:3fff:ffff:ffff:ffff:ffff:ffff:ffff
533203:4000::/203203:4fff:ffff:ffff:ffff:ffff:ffff:ffff
543203:5000::/203203:5fff:ffff:ffff:ffff:ffff:ffff:ffff
553203:6000::/203203:6fff:ffff:ffff:ffff:ffff:ffff:ffff
563203:7000::/203203:7fff:ffff:ffff:ffff:ffff:ffff:ffff
573203:8000::/203203:8fff:ffff:ffff:ffff:ffff:ffff:ffff
583203:9000::/203203:9fff:ffff:ffff:ffff:ffff:ffff:ffff
593203:a000::/203203:afff:ffff:ffff:ffff:ffff:ffff:ffff
603203:b000::/203203:bfff:ffff:ffff:ffff:ffff:ffff:ffff
613203:c000::/203203:cfff:ffff:ffff:ffff:ffff:ffff:ffff
623203:d000::/203203:dfff:ffff:ffff:ffff:ffff:ffff:ffff
633203:e000::/203203:efff:ffff:ffff:ffff:ffff:ffff:ffff
643203:f000::/203203:ffff:ffff:ffff:ffff:ffff:ffff:ffff
653204::/203204:fff:ffff:ffff:ffff:ffff:ffff:ffff
663204:1000::/203204:1fff:ffff:ffff:ffff:ffff:ffff:ffff
673204:2000::/203204:2fff:ffff:ffff:ffff:ffff:ffff:ffff
683204:3000::/203204:3fff:ffff:ffff:ffff:ffff:ffff:ffff
693204:4000::/203204:4fff:ffff:ffff:ffff:ffff:ffff:ffff
703204:5000::/203204:5fff:ffff:ffff:ffff:ffff:ffff:ffff
713204:6000::/203204:6fff:ffff:ffff:ffff:ffff:ffff:ffff
723204:7000::/203204:7fff:ffff:ffff:ffff:ffff:ffff:ffff
733204:8000::/203204:8fff:ffff:ffff:ffff:ffff:ffff:ffff
743204:9000::/203204:9fff:ffff:ffff:ffff:ffff:ffff:ffff
753204:a000::/203204:afff:ffff:ffff:ffff:ffff:ffff:ffff
763204:b000::/203204:bfff:ffff:ffff:ffff:ffff:ffff:ffff
773204:c000::/203204:cfff:ffff:ffff:ffff:ffff:ffff:ffff
783204:d000::/203204:dfff:ffff:ffff:ffff:ffff:ffff:ffff
793204:e000::/203204:efff:ffff:ffff:ffff:ffff:ffff:ffff
803204:f000::/203204:ffff:ffff:ffff:ffff:ffff:ffff:ffff
813205::/203205:fff:ffff:ffff:ffff:ffff:ffff:ffff
823205:1000::/203205:1fff:ffff:ffff:ffff:ffff:ffff:ffff
833205:2000::/203205:2fff:ffff:ffff:ffff:ffff:ffff:ffff
843205:3000::/203205:3fff:ffff:ffff:ffff:ffff:ffff:ffff
853205:4000::/203205:4fff:ffff:ffff:ffff:ffff:ffff:ffff
863205:5000::/203205:5fff:ffff:ffff:ffff:ffff:ffff:ffff
873205:6000::/203205:6fff:ffff:ffff:ffff:ffff:ffff:ffff
883205:7000::/203205:7fff:ffff:ffff:ffff:ffff:ffff:ffff
893205:8000::/203205:8fff:ffff:ffff:ffff:ffff:ffff:ffff
903205:9000::/203205:9fff:ffff:ffff:ffff:ffff:ffff:ffff
913205:a000::/203205:afff:ffff:ffff:ffff:ffff:ffff:ffff
923205:b000::/203205:bfff:ffff:ffff:ffff:ffff:ffff:ffff
933205:c000::/203205:cfff:ffff:ffff:ffff:ffff:ffff:ffff
943205:d000::/203205:dfff:ffff:ffff:ffff:ffff:ffff:ffff
953205:e000::/203205:efff:ffff:ffff:ffff:ffff:ffff:ffff
963205:f000::/203205:ffff:ffff:ffff:ffff:ffff:ffff:ffff
973206::/203206:fff:ffff:ffff:ffff:ffff:ffff:ffff
983206:1000::/203206:1fff:ffff:ffff:ffff:ffff:ffff:ffff
993206:2000::/203206:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1003206:3000::/203206:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1013206:4000::/203206:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1023206:5000::/203206:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1033206:6000::/203206:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1043206:7000::/203206:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1053206:8000::/203206:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1063206:9000::/203206:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1073206:a000::/203206:afff:ffff:ffff:ffff:ffff:ffff:ffff
1083206:b000::/203206:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1093206:c000::/203206:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1103206:d000::/203206:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1113206:e000::/203206:efff:ffff:ffff:ffff:ffff:ffff:ffff
1123206:f000::/203206:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1133207::/203207:fff:ffff:ffff:ffff:ffff:ffff:ffff
1143207:1000::/203207:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1153207:2000::/203207:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1163207:3000::/203207:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1173207:4000::/203207:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1183207:5000::/203207:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1193207:6000::/203207:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1203207:7000::/203207:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1213207:8000::/203207:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1223207:9000::/203207:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1233207:a000::/203207:afff:ffff:ffff:ffff:ffff:ffff:ffff
1243207:b000::/203207:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1253207:c000::/203207:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1263207:d000::/203207:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1273207:e000::/203207:efff:ffff:ffff:ffff:ffff:ffff:ffff
1283207:f000::/203207:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1293208::/203208:fff:ffff:ffff:ffff:ffff:ffff:ffff
1303208:1000::/203208:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1313208:2000::/203208:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1323208:3000::/203208:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1333208:4000::/203208:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1343208:5000::/203208:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1353208:6000::/203208:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1363208:7000::/203208:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1373208:8000::/203208:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1383208:9000::/203208:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1393208:a000::/203208:afff:ffff:ffff:ffff:ffff:ffff:ffff
1403208:b000::/203208:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1413208:c000::/203208:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1423208:d000::/203208:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1433208:e000::/203208:efff:ffff:ffff:ffff:ffff:ffff:ffff
1443208:f000::/203208:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1453209::/203209:fff:ffff:ffff:ffff:ffff:ffff:ffff
1463209:1000::/203209:1fff:ffff:ffff:ffff:ffff:ffff:ffff
1473209:2000::/203209:2fff:ffff:ffff:ffff:ffff:ffff:ffff
1483209:3000::/203209:3fff:ffff:ffff:ffff:ffff:ffff:ffff
1493209:4000::/203209:4fff:ffff:ffff:ffff:ffff:ffff:ffff
1503209:5000::/203209:5fff:ffff:ffff:ffff:ffff:ffff:ffff
1513209:6000::/203209:6fff:ffff:ffff:ffff:ffff:ffff:ffff
1523209:7000::/203209:7fff:ffff:ffff:ffff:ffff:ffff:ffff
1533209:8000::/203209:8fff:ffff:ffff:ffff:ffff:ffff:ffff
1543209:9000::/203209:9fff:ffff:ffff:ffff:ffff:ffff:ffff
1553209:a000::/203209:afff:ffff:ffff:ffff:ffff:ffff:ffff
1563209:b000::/203209:bfff:ffff:ffff:ffff:ffff:ffff:ffff
1573209:c000::/203209:cfff:ffff:ffff:ffff:ffff:ffff:ffff
1583209:d000::/203209:dfff:ffff:ffff:ffff:ffff:ffff:ffff
1593209:e000::/203209:efff:ffff:ffff:ffff:ffff:ffff:ffff
1603209:f000::/203209:ffff:ffff:ffff:ffff:ffff:ffff:ffff
161320a::/20320a:fff:ffff:ffff:ffff:ffff:ffff:ffff
162320a:1000::/20320a:1fff:ffff:ffff:ffff:ffff:ffff:ffff
163320a:2000::/20320a:2fff:ffff:ffff:ffff:ffff:ffff:ffff
164320a:3000::/20320a:3fff:ffff:ffff:ffff:ffff:ffff:ffff
165320a:4000::/20320a:4fff:ffff:ffff:ffff:ffff:ffff:ffff
166320a:5000::/20320a:5fff:ffff:ffff:ffff:ffff:ffff:ffff
167320a:6000::/20320a:6fff:ffff:ffff:ffff:ffff:ffff:ffff
168320a:7000::/20320a:7fff:ffff:ffff:ffff:ffff:ffff:ffff
169320a:8000::/20320a:8fff:ffff:ffff:ffff:ffff:ffff:ffff
170320a:9000::/20320a:9fff:ffff:ffff:ffff:ffff:ffff:ffff
171320a:a000::/20320a:afff:ffff:ffff:ffff:ffff:ffff:ffff
172320a:b000::/20320a:bfff:ffff:ffff:ffff:ffff:ffff:ffff
173320a:c000::/20320a:cfff:ffff:ffff:ffff:ffff:ffff:ffff
174320a:d000::/20320a:dfff:ffff:ffff:ffff:ffff:ffff:ffff
175320a:e000::/20320a:efff:ffff:ffff:ffff:ffff:ffff:ffff
176320a:f000::/20320a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
177320b::/20320b:fff:ffff:ffff:ffff:ffff:ffff:ffff
178320b:1000::/20320b:1fff:ffff:ffff:ffff:ffff:ffff:ffff
179320b:2000::/20320b:2fff:ffff:ffff:ffff:ffff:ffff:ffff
180320b:3000::/20320b:3fff:ffff:ffff:ffff:ffff:ffff:ffff
181320b:4000::/20320b:4fff:ffff:ffff:ffff:ffff:ffff:ffff
182320b:5000::/20320b:5fff:ffff:ffff:ffff:ffff:ffff:ffff
183320b:6000::/20320b:6fff:ffff:ffff:ffff:ffff:ffff:ffff
184320b:7000::/20320b:7fff:ffff:ffff:ffff:ffff:ffff:ffff
185320b:8000::/20320b:8fff:ffff:ffff:ffff:ffff:ffff:ffff
186320b:9000::/20320b:9fff:ffff:ffff:ffff:ffff:ffff:ffff
187320b:a000::/20320b:afff:ffff:ffff:ffff:ffff:ffff:ffff
188320b:b000::/20320b:bfff:ffff:ffff:ffff:ffff:ffff:ffff
189320b:c000::/20320b:cfff:ffff:ffff:ffff:ffff:ffff:ffff
190320b:d000::/20320b:dfff:ffff:ffff:ffff:ffff:ffff:ffff
191320b:e000::/20320b:efff:ffff:ffff:ffff:ffff:ffff:ffff
192320b:f000::/20320b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
193320c::/20320c:fff:ffff:ffff:ffff:ffff:ffff:ffff
194320c:1000::/20320c:1fff:ffff:ffff:ffff:ffff:ffff:ffff
195320c:2000::/20320c:2fff:ffff:ffff:ffff:ffff:ffff:ffff
196320c:3000::/20320c:3fff:ffff:ffff:ffff:ffff:ffff:ffff
197320c:4000::/20320c:4fff:ffff:ffff:ffff:ffff:ffff:ffff
198320c:5000::/20320c:5fff:ffff:ffff:ffff:ffff:ffff:ffff
199320c:6000::/20320c:6fff:ffff:ffff:ffff:ffff:ffff:ffff
200320c:7000::/20320c:7fff:ffff:ffff:ffff:ffff:ffff:ffff
201320c:8000::/20320c:8fff:ffff:ffff:ffff:ffff:ffff:ffff
202320c:9000::/20320c:9fff:ffff:ffff:ffff:ffff:ffff:ffff
203320c:a000::/20320c:afff:ffff:ffff:ffff:ffff:ffff:ffff
204320c:b000::/20320c:bfff:ffff:ffff:ffff:ffff:ffff:ffff
205320c:c000::/20320c:cfff:ffff:ffff:ffff:ffff:ffff:ffff
206320c:d000::/20320c:dfff:ffff:ffff:ffff:ffff:ffff:ffff
207320c:e000::/20320c:efff:ffff:ffff:ffff:ffff:ffff:ffff
208320c:f000::/20320c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
209320d::/20320d:fff:ffff:ffff:ffff:ffff:ffff:ffff
210320d:1000::/20320d:1fff:ffff:ffff:ffff:ffff:ffff:ffff
211320d:2000::/20320d:2fff:ffff:ffff:ffff:ffff:ffff:ffff
212320d:3000::/20320d:3fff:ffff:ffff:ffff:ffff:ffff:ffff
213320d:4000::/20320d:4fff:ffff:ffff:ffff:ffff:ffff:ffff
214320d:5000::/20320d:5fff:ffff:ffff:ffff:ffff:ffff:ffff
215320d:6000::/20320d:6fff:ffff:ffff:ffff:ffff:ffff:ffff
216320d:7000::/20320d:7fff:ffff:ffff:ffff:ffff:ffff:ffff
217320d:8000::/20320d:8fff:ffff:ffff:ffff:ffff:ffff:ffff
218320d:9000::/20320d:9fff:ffff:ffff:ffff:ffff:ffff:ffff
219320d:a000::/20320d:afff:ffff:ffff:ffff:ffff:ffff:ffff
220320d:b000::/20320d:bfff:ffff:ffff:ffff:ffff:ffff:ffff
221320d:c000::/20320d:cfff:ffff:ffff:ffff:ffff:ffff:ffff
222320d:d000::/20320d:dfff:ffff:ffff:ffff:ffff:ffff:ffff
223320d:e000::/20320d:efff:ffff:ffff:ffff:ffff:ffff:ffff
224320d:f000::/20320d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
225320e::/20320e:fff:ffff:ffff:ffff:ffff:ffff:ffff
226320e:1000::/20320e:1fff:ffff:ffff:ffff:ffff:ffff:ffff
227320e:2000::/20320e:2fff:ffff:ffff:ffff:ffff:ffff:ffff
228320e:3000::/20320e:3fff:ffff:ffff:ffff:ffff:ffff:ffff
229320e:4000::/20320e:4fff:ffff:ffff:ffff:ffff:ffff:ffff
230320e:5000::/20320e:5fff:ffff:ffff:ffff:ffff:ffff:ffff
231320e:6000::/20320e:6fff:ffff:ffff:ffff:ffff:ffff:ffff
232320e:7000::/20320e:7fff:ffff:ffff:ffff:ffff:ffff:ffff
233320e:8000::/20320e:8fff:ffff:ffff:ffff:ffff:ffff:ffff
234320e:9000::/20320e:9fff:ffff:ffff:ffff:ffff:ffff:ffff
235320e:a000::/20320e:afff:ffff:ffff:ffff:ffff:ffff:ffff
236320e:b000::/20320e:bfff:ffff:ffff:ffff:ffff:ffff:ffff
237320e:c000::/20320e:cfff:ffff:ffff:ffff:ffff:ffff:ffff
238320e:d000::/20320e:dfff:ffff:ffff:ffff:ffff:ffff:ffff
239320e:e000::/20320e:efff:ffff:ffff:ffff:ffff:ffff:ffff
240320e:f000::/20320e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
241320f::/20320f:fff:ffff:ffff:ffff:ffff:ffff:ffff
242320f:1000::/20320f:1fff:ffff:ffff:ffff:ffff:ffff:ffff
243320f:2000::/20320f:2fff:ffff:ffff:ffff:ffff:ffff:ffff
244320f:3000::/20320f:3fff:ffff:ffff:ffff:ffff:ffff:ffff
245320f:4000::/20320f:4fff:ffff:ffff:ffff:ffff:ffff:ffff
246320f:5000::/20320f:5fff:ffff:ffff:ffff:ffff:ffff:ffff
247320f:6000::/20320f:6fff:ffff:ffff:ffff:ffff:ffff:ffff
248320f:7000::/20320f:7fff:ffff:ffff:ffff:ffff:ffff:ffff
249320f:8000::/20320f:8fff:ffff:ffff:ffff:ffff:ffff:ffff
250320f:9000::/20320f:9fff:ffff:ffff:ffff:ffff:ffff:ffff
251320f:a000::/20320f:afff:ffff:ffff:ffff:ffff:ffff:ffff
252320f:b000::/20320f:bfff:ffff:ffff:ffff:ffff:ffff:ffff
253320f:c000::/20320f:cfff:ffff:ffff:ffff:ffff:ffff:ffff
254320f:d000::/20320f:dfff:ffff:ffff:ffff:ffff:ffff:ffff
255320f:e000::/20320f:efff:ffff:ffff:ffff:ffff:ffff:ffff
256320f:f000::/20320f: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.