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/28
Addresses2^100
/64 networks2^36
Network
2002:bc0::/28
First address
2002:bc0::
Last address
2002:bcf:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
1,267,650,600,228,229,401,496,703,205,376 (2^100)
/64 networks (LANs)
68,719,476,736 (2^36)
Full form
2002:0bc0:0000:0000:0000:0000:0000:0000
Type
6to4 2002::/16
IPv6 tunnelled over IPv4 (largely retired)
Reverse DNS zone
c.b.0.2.0.0.2.ip6.arpa
Split into smaller subnets/36
/29 (2)/30 (4)/31 (8)/32 (16)/36 (256)/40 (4,096)/44 (65,536)

2002:bc0::/28 makes 256 subnets of /36.

Subnets
#SubnetLast address
12002:bc0::/362002:bc0:fff:ffff:ffff:ffff:ffff:ffff
22002:bc0:1000::/362002:bc0:1fff:ffff:ffff:ffff:ffff:ffff
32002:bc0:2000::/362002:bc0:2fff:ffff:ffff:ffff:ffff:ffff
42002:bc0:3000::/362002:bc0:3fff:ffff:ffff:ffff:ffff:ffff
52002:bc0:4000::/362002:bc0:4fff:ffff:ffff:ffff:ffff:ffff
62002:bc0:5000::/362002:bc0:5fff:ffff:ffff:ffff:ffff:ffff
72002:bc0:6000::/362002:bc0:6fff:ffff:ffff:ffff:ffff:ffff
82002:bc0:7000::/362002:bc0:7fff:ffff:ffff:ffff:ffff:ffff
92002:bc0:8000::/362002:bc0:8fff:ffff:ffff:ffff:ffff:ffff
102002:bc0:9000::/362002:bc0:9fff:ffff:ffff:ffff:ffff:ffff
112002:bc0:a000::/362002:bc0:afff:ffff:ffff:ffff:ffff:ffff
122002:bc0:b000::/362002:bc0:bfff:ffff:ffff:ffff:ffff:ffff
132002:bc0:c000::/362002:bc0:cfff:ffff:ffff:ffff:ffff:ffff
142002:bc0:d000::/362002:bc0:dfff:ffff:ffff:ffff:ffff:ffff
152002:bc0:e000::/362002:bc0:efff:ffff:ffff:ffff:ffff:ffff
162002:bc0:f000::/362002:bc0:ffff:ffff:ffff:ffff:ffff:ffff
172002:bc1::/362002:bc1:fff:ffff:ffff:ffff:ffff:ffff
182002:bc1:1000::/362002:bc1:1fff:ffff:ffff:ffff:ffff:ffff
192002:bc1:2000::/362002:bc1:2fff:ffff:ffff:ffff:ffff:ffff
202002:bc1:3000::/362002:bc1:3fff:ffff:ffff:ffff:ffff:ffff
212002:bc1:4000::/362002:bc1:4fff:ffff:ffff:ffff:ffff:ffff
222002:bc1:5000::/362002:bc1:5fff:ffff:ffff:ffff:ffff:ffff
232002:bc1:6000::/362002:bc1:6fff:ffff:ffff:ffff:ffff:ffff
242002:bc1:7000::/362002:bc1:7fff:ffff:ffff:ffff:ffff:ffff
252002:bc1:8000::/362002:bc1:8fff:ffff:ffff:ffff:ffff:ffff
262002:bc1:9000::/362002:bc1:9fff:ffff:ffff:ffff:ffff:ffff
272002:bc1:a000::/362002:bc1:afff:ffff:ffff:ffff:ffff:ffff
282002:bc1:b000::/362002:bc1:bfff:ffff:ffff:ffff:ffff:ffff
292002:bc1:c000::/362002:bc1:cfff:ffff:ffff:ffff:ffff:ffff
302002:bc1:d000::/362002:bc1:dfff:ffff:ffff:ffff:ffff:ffff
312002:bc1:e000::/362002:bc1:efff:ffff:ffff:ffff:ffff:ffff
322002:bc1:f000::/362002:bc1:ffff:ffff:ffff:ffff:ffff:ffff
332002:bc2::/362002:bc2:fff:ffff:ffff:ffff:ffff:ffff
342002:bc2:1000::/362002:bc2:1fff:ffff:ffff:ffff:ffff:ffff
352002:bc2:2000::/362002:bc2:2fff:ffff:ffff:ffff:ffff:ffff
362002:bc2:3000::/362002:bc2:3fff:ffff:ffff:ffff:ffff:ffff
372002:bc2:4000::/362002:bc2:4fff:ffff:ffff:ffff:ffff:ffff
382002:bc2:5000::/362002:bc2:5fff:ffff:ffff:ffff:ffff:ffff
392002:bc2:6000::/362002:bc2:6fff:ffff:ffff:ffff:ffff:ffff
402002:bc2:7000::/362002:bc2:7fff:ffff:ffff:ffff:ffff:ffff
412002:bc2:8000::/362002:bc2:8fff:ffff:ffff:ffff:ffff:ffff
422002:bc2:9000::/362002:bc2:9fff:ffff:ffff:ffff:ffff:ffff
432002:bc2:a000::/362002:bc2:afff:ffff:ffff:ffff:ffff:ffff
442002:bc2:b000::/362002:bc2:bfff:ffff:ffff:ffff:ffff:ffff
452002:bc2:c000::/362002:bc2:cfff:ffff:ffff:ffff:ffff:ffff
462002:bc2:d000::/362002:bc2:dfff:ffff:ffff:ffff:ffff:ffff
472002:bc2:e000::/362002:bc2:efff:ffff:ffff:ffff:ffff:ffff
482002:bc2:f000::/362002:bc2:ffff:ffff:ffff:ffff:ffff:ffff
492002:bc3::/362002:bc3:fff:ffff:ffff:ffff:ffff:ffff
502002:bc3:1000::/362002:bc3:1fff:ffff:ffff:ffff:ffff:ffff
512002:bc3:2000::/362002:bc3:2fff:ffff:ffff:ffff:ffff:ffff
522002:bc3:3000::/362002:bc3:3fff:ffff:ffff:ffff:ffff:ffff
532002:bc3:4000::/362002:bc3:4fff:ffff:ffff:ffff:ffff:ffff
542002:bc3:5000::/362002:bc3:5fff:ffff:ffff:ffff:ffff:ffff
552002:bc3:6000::/362002:bc3:6fff:ffff:ffff:ffff:ffff:ffff
562002:bc3:7000::/362002:bc3:7fff:ffff:ffff:ffff:ffff:ffff
572002:bc3:8000::/362002:bc3:8fff:ffff:ffff:ffff:ffff:ffff
582002:bc3:9000::/362002:bc3:9fff:ffff:ffff:ffff:ffff:ffff
592002:bc3:a000::/362002:bc3:afff:ffff:ffff:ffff:ffff:ffff
602002:bc3:b000::/362002:bc3:bfff:ffff:ffff:ffff:ffff:ffff
612002:bc3:c000::/362002:bc3:cfff:ffff:ffff:ffff:ffff:ffff
622002:bc3:d000::/362002:bc3:dfff:ffff:ffff:ffff:ffff:ffff
632002:bc3:e000::/362002:bc3:efff:ffff:ffff:ffff:ffff:ffff
642002:bc3:f000::/362002:bc3:ffff:ffff:ffff:ffff:ffff:ffff
652002:bc4::/362002:bc4:fff:ffff:ffff:ffff:ffff:ffff
662002:bc4:1000::/362002:bc4:1fff:ffff:ffff:ffff:ffff:ffff
672002:bc4:2000::/362002:bc4:2fff:ffff:ffff:ffff:ffff:ffff
682002:bc4:3000::/362002:bc4:3fff:ffff:ffff:ffff:ffff:ffff
692002:bc4:4000::/362002:bc4:4fff:ffff:ffff:ffff:ffff:ffff
702002:bc4:5000::/362002:bc4:5fff:ffff:ffff:ffff:ffff:ffff
712002:bc4:6000::/362002:bc4:6fff:ffff:ffff:ffff:ffff:ffff
722002:bc4:7000::/362002:bc4:7fff:ffff:ffff:ffff:ffff:ffff
732002:bc4:8000::/362002:bc4:8fff:ffff:ffff:ffff:ffff:ffff
742002:bc4:9000::/362002:bc4:9fff:ffff:ffff:ffff:ffff:ffff
752002:bc4:a000::/362002:bc4:afff:ffff:ffff:ffff:ffff:ffff
762002:bc4:b000::/362002:bc4:bfff:ffff:ffff:ffff:ffff:ffff
772002:bc4:c000::/362002:bc4:cfff:ffff:ffff:ffff:ffff:ffff
782002:bc4:d000::/362002:bc4:dfff:ffff:ffff:ffff:ffff:ffff
792002:bc4:e000::/362002:bc4:efff:ffff:ffff:ffff:ffff:ffff
802002:bc4:f000::/362002:bc4:ffff:ffff:ffff:ffff:ffff:ffff
812002:bc5::/362002:bc5:fff:ffff:ffff:ffff:ffff:ffff
822002:bc5:1000::/362002:bc5:1fff:ffff:ffff:ffff:ffff:ffff
832002:bc5:2000::/362002:bc5:2fff:ffff:ffff:ffff:ffff:ffff
842002:bc5:3000::/362002:bc5:3fff:ffff:ffff:ffff:ffff:ffff
852002:bc5:4000::/362002:bc5:4fff:ffff:ffff:ffff:ffff:ffff
862002:bc5:5000::/362002:bc5:5fff:ffff:ffff:ffff:ffff:ffff
872002:bc5:6000::/362002:bc5:6fff:ffff:ffff:ffff:ffff:ffff
882002:bc5:7000::/362002:bc5:7fff:ffff:ffff:ffff:ffff:ffff
892002:bc5:8000::/362002:bc5:8fff:ffff:ffff:ffff:ffff:ffff
902002:bc5:9000::/362002:bc5:9fff:ffff:ffff:ffff:ffff:ffff
912002:bc5:a000::/362002:bc5:afff:ffff:ffff:ffff:ffff:ffff
922002:bc5:b000::/362002:bc5:bfff:ffff:ffff:ffff:ffff:ffff
932002:bc5:c000::/362002:bc5:cfff:ffff:ffff:ffff:ffff:ffff
942002:bc5:d000::/362002:bc5:dfff:ffff:ffff:ffff:ffff:ffff
952002:bc5:e000::/362002:bc5:efff:ffff:ffff:ffff:ffff:ffff
962002:bc5:f000::/362002:bc5:ffff:ffff:ffff:ffff:ffff:ffff
972002:bc6::/362002:bc6:fff:ffff:ffff:ffff:ffff:ffff
982002:bc6:1000::/362002:bc6:1fff:ffff:ffff:ffff:ffff:ffff
992002:bc6:2000::/362002:bc6:2fff:ffff:ffff:ffff:ffff:ffff
1002002:bc6:3000::/362002:bc6:3fff:ffff:ffff:ffff:ffff:ffff
1012002:bc6:4000::/362002:bc6:4fff:ffff:ffff:ffff:ffff:ffff
1022002:bc6:5000::/362002:bc6:5fff:ffff:ffff:ffff:ffff:ffff
1032002:bc6:6000::/362002:bc6:6fff:ffff:ffff:ffff:ffff:ffff
1042002:bc6:7000::/362002:bc6:7fff:ffff:ffff:ffff:ffff:ffff
1052002:bc6:8000::/362002:bc6:8fff:ffff:ffff:ffff:ffff:ffff
1062002:bc6:9000::/362002:bc6:9fff:ffff:ffff:ffff:ffff:ffff
1072002:bc6:a000::/362002:bc6:afff:ffff:ffff:ffff:ffff:ffff
1082002:bc6:b000::/362002:bc6:bfff:ffff:ffff:ffff:ffff:ffff
1092002:bc6:c000::/362002:bc6:cfff:ffff:ffff:ffff:ffff:ffff
1102002:bc6:d000::/362002:bc6:dfff:ffff:ffff:ffff:ffff:ffff
1112002:bc6:e000::/362002:bc6:efff:ffff:ffff:ffff:ffff:ffff
1122002:bc6:f000::/362002:bc6:ffff:ffff:ffff:ffff:ffff:ffff
1132002:bc7::/362002:bc7:fff:ffff:ffff:ffff:ffff:ffff
1142002:bc7:1000::/362002:bc7:1fff:ffff:ffff:ffff:ffff:ffff
1152002:bc7:2000::/362002:bc7:2fff:ffff:ffff:ffff:ffff:ffff
1162002:bc7:3000::/362002:bc7:3fff:ffff:ffff:ffff:ffff:ffff
1172002:bc7:4000::/362002:bc7:4fff:ffff:ffff:ffff:ffff:ffff
1182002:bc7:5000::/362002:bc7:5fff:ffff:ffff:ffff:ffff:ffff
1192002:bc7:6000::/362002:bc7:6fff:ffff:ffff:ffff:ffff:ffff
1202002:bc7:7000::/362002:bc7:7fff:ffff:ffff:ffff:ffff:ffff
1212002:bc7:8000::/362002:bc7:8fff:ffff:ffff:ffff:ffff:ffff
1222002:bc7:9000::/362002:bc7:9fff:ffff:ffff:ffff:ffff:ffff
1232002:bc7:a000::/362002:bc7:afff:ffff:ffff:ffff:ffff:ffff
1242002:bc7:b000::/362002:bc7:bfff:ffff:ffff:ffff:ffff:ffff
1252002:bc7:c000::/362002:bc7:cfff:ffff:ffff:ffff:ffff:ffff
1262002:bc7:d000::/362002:bc7:dfff:ffff:ffff:ffff:ffff:ffff
1272002:bc7:e000::/362002:bc7:efff:ffff:ffff:ffff:ffff:ffff
1282002:bc7:f000::/362002:bc7:ffff:ffff:ffff:ffff:ffff:ffff
1292002:bc8::/362002:bc8:fff:ffff:ffff:ffff:ffff:ffff
1302002:bc8:1000::/362002:bc8:1fff:ffff:ffff:ffff:ffff:ffff
1312002:bc8:2000::/362002:bc8:2fff:ffff:ffff:ffff:ffff:ffff
1322002:bc8:3000::/362002:bc8:3fff:ffff:ffff:ffff:ffff:ffff
1332002:bc8:4000::/362002:bc8:4fff:ffff:ffff:ffff:ffff:ffff
1342002:bc8:5000::/362002:bc8:5fff:ffff:ffff:ffff:ffff:ffff
1352002:bc8:6000::/362002:bc8:6fff:ffff:ffff:ffff:ffff:ffff
1362002:bc8:7000::/362002:bc8:7fff:ffff:ffff:ffff:ffff:ffff
1372002:bc8:8000::/362002:bc8:8fff:ffff:ffff:ffff:ffff:ffff
1382002:bc8:9000::/362002:bc8:9fff:ffff:ffff:ffff:ffff:ffff
1392002:bc8:a000::/362002:bc8:afff:ffff:ffff:ffff:ffff:ffff
1402002:bc8:b000::/362002:bc8:bfff:ffff:ffff:ffff:ffff:ffff
1412002:bc8:c000::/362002:bc8:cfff:ffff:ffff:ffff:ffff:ffff
1422002:bc8:d000::/362002:bc8:dfff:ffff:ffff:ffff:ffff:ffff
1432002:bc8:e000::/362002:bc8:efff:ffff:ffff:ffff:ffff:ffff
1442002:bc8:f000::/362002:bc8:ffff:ffff:ffff:ffff:ffff:ffff
1452002:bc9::/362002:bc9:fff:ffff:ffff:ffff:ffff:ffff
1462002:bc9:1000::/362002:bc9:1fff:ffff:ffff:ffff:ffff:ffff
1472002:bc9:2000::/362002:bc9:2fff:ffff:ffff:ffff:ffff:ffff
1482002:bc9:3000::/362002:bc9:3fff:ffff:ffff:ffff:ffff:ffff
1492002:bc9:4000::/362002:bc9:4fff:ffff:ffff:ffff:ffff:ffff
1502002:bc9:5000::/362002:bc9:5fff:ffff:ffff:ffff:ffff:ffff
1512002:bc9:6000::/362002:bc9:6fff:ffff:ffff:ffff:ffff:ffff
1522002:bc9:7000::/362002:bc9:7fff:ffff:ffff:ffff:ffff:ffff
1532002:bc9:8000::/362002:bc9:8fff:ffff:ffff:ffff:ffff:ffff
1542002:bc9:9000::/362002:bc9:9fff:ffff:ffff:ffff:ffff:ffff
1552002:bc9:a000::/362002:bc9:afff:ffff:ffff:ffff:ffff:ffff
1562002:bc9:b000::/362002:bc9:bfff:ffff:ffff:ffff:ffff:ffff
1572002:bc9:c000::/362002:bc9:cfff:ffff:ffff:ffff:ffff:ffff
1582002:bc9:d000::/362002:bc9:dfff:ffff:ffff:ffff:ffff:ffff
1592002:bc9:e000::/362002:bc9:efff:ffff:ffff:ffff:ffff:ffff
1602002:bc9:f000::/362002:bc9:ffff:ffff:ffff:ffff:ffff:ffff
1612002:bca::/362002:bca:fff:ffff:ffff:ffff:ffff:ffff
1622002:bca:1000::/362002:bca:1fff:ffff:ffff:ffff:ffff:ffff
1632002:bca:2000::/362002:bca:2fff:ffff:ffff:ffff:ffff:ffff
1642002:bca:3000::/362002:bca:3fff:ffff:ffff:ffff:ffff:ffff
1652002:bca:4000::/362002:bca:4fff:ffff:ffff:ffff:ffff:ffff
1662002:bca:5000::/362002:bca:5fff:ffff:ffff:ffff:ffff:ffff
1672002:bca:6000::/362002:bca:6fff:ffff:ffff:ffff:ffff:ffff
1682002:bca:7000::/362002:bca:7fff:ffff:ffff:ffff:ffff:ffff
1692002:bca:8000::/362002:bca:8fff:ffff:ffff:ffff:ffff:ffff
1702002:bca:9000::/362002:bca:9fff:ffff:ffff:ffff:ffff:ffff
1712002:bca:a000::/362002:bca:afff:ffff:ffff:ffff:ffff:ffff
1722002:bca:b000::/362002:bca:bfff:ffff:ffff:ffff:ffff:ffff
1732002:bca:c000::/362002:bca:cfff:ffff:ffff:ffff:ffff:ffff
1742002:bca:d000::/362002:bca:dfff:ffff:ffff:ffff:ffff:ffff
1752002:bca:e000::/362002:bca:efff:ffff:ffff:ffff:ffff:ffff
1762002:bca:f000::/362002:bca:ffff:ffff:ffff:ffff:ffff:ffff
1772002:bcb::/362002:bcb:fff:ffff:ffff:ffff:ffff:ffff
1782002:bcb:1000::/362002:bcb:1fff:ffff:ffff:ffff:ffff:ffff
1792002:bcb:2000::/362002:bcb:2fff:ffff:ffff:ffff:ffff:ffff
1802002:bcb:3000::/362002:bcb:3fff:ffff:ffff:ffff:ffff:ffff
1812002:bcb:4000::/362002:bcb:4fff:ffff:ffff:ffff:ffff:ffff
1822002:bcb:5000::/362002:bcb:5fff:ffff:ffff:ffff:ffff:ffff
1832002:bcb:6000::/362002:bcb:6fff:ffff:ffff:ffff:ffff:ffff
1842002:bcb:7000::/362002:bcb:7fff:ffff:ffff:ffff:ffff:ffff
1852002:bcb:8000::/362002:bcb:8fff:ffff:ffff:ffff:ffff:ffff
1862002:bcb:9000::/362002:bcb:9fff:ffff:ffff:ffff:ffff:ffff
1872002:bcb:a000::/362002:bcb:afff:ffff:ffff:ffff:ffff:ffff
1882002:bcb:b000::/362002:bcb:bfff:ffff:ffff:ffff:ffff:ffff
1892002:bcb:c000::/362002:bcb:cfff:ffff:ffff:ffff:ffff:ffff
1902002:bcb:d000::/362002:bcb:dfff:ffff:ffff:ffff:ffff:ffff
1912002:bcb:e000::/362002:bcb:efff:ffff:ffff:ffff:ffff:ffff
1922002:bcb:f000::/362002:bcb:ffff:ffff:ffff:ffff:ffff:ffff
1932002:bcc::/362002:bcc:fff:ffff:ffff:ffff:ffff:ffff
1942002:bcc:1000::/362002:bcc:1fff:ffff:ffff:ffff:ffff:ffff
1952002:bcc:2000::/362002:bcc:2fff:ffff:ffff:ffff:ffff:ffff
1962002:bcc:3000::/362002:bcc:3fff:ffff:ffff:ffff:ffff:ffff
1972002:bcc:4000::/362002:bcc:4fff:ffff:ffff:ffff:ffff:ffff
1982002:bcc:5000::/362002:bcc:5fff:ffff:ffff:ffff:ffff:ffff
1992002:bcc:6000::/362002:bcc:6fff:ffff:ffff:ffff:ffff:ffff
2002002:bcc:7000::/362002:bcc:7fff:ffff:ffff:ffff:ffff:ffff
2012002:bcc:8000::/362002:bcc:8fff:ffff:ffff:ffff:ffff:ffff
2022002:bcc:9000::/362002:bcc:9fff:ffff:ffff:ffff:ffff:ffff
2032002:bcc:a000::/362002:bcc:afff:ffff:ffff:ffff:ffff:ffff
2042002:bcc:b000::/362002:bcc:bfff:ffff:ffff:ffff:ffff:ffff
2052002:bcc:c000::/362002:bcc:cfff:ffff:ffff:ffff:ffff:ffff
2062002:bcc:d000::/362002:bcc:dfff:ffff:ffff:ffff:ffff:ffff
2072002:bcc:e000::/362002:bcc:efff:ffff:ffff:ffff:ffff:ffff
2082002:bcc:f000::/362002:bcc:ffff:ffff:ffff:ffff:ffff:ffff
2092002:bcd::/362002:bcd:fff:ffff:ffff:ffff:ffff:ffff
2102002:bcd:1000::/362002:bcd:1fff:ffff:ffff:ffff:ffff:ffff
2112002:bcd:2000::/362002:bcd:2fff:ffff:ffff:ffff:ffff:ffff
2122002:bcd:3000::/362002:bcd:3fff:ffff:ffff:ffff:ffff:ffff
2132002:bcd:4000::/362002:bcd:4fff:ffff:ffff:ffff:ffff:ffff
2142002:bcd:5000::/362002:bcd:5fff:ffff:ffff:ffff:ffff:ffff
2152002:bcd:6000::/362002:bcd:6fff:ffff:ffff:ffff:ffff:ffff
2162002:bcd:7000::/362002:bcd:7fff:ffff:ffff:ffff:ffff:ffff
2172002:bcd:8000::/362002:bcd:8fff:ffff:ffff:ffff:ffff:ffff
2182002:bcd:9000::/362002:bcd:9fff:ffff:ffff:ffff:ffff:ffff
2192002:bcd:a000::/362002:bcd:afff:ffff:ffff:ffff:ffff:ffff
2202002:bcd:b000::/362002:bcd:bfff:ffff:ffff:ffff:ffff:ffff
2212002:bcd:c000::/362002:bcd:cfff:ffff:ffff:ffff:ffff:ffff
2222002:bcd:d000::/362002:bcd:dfff:ffff:ffff:ffff:ffff:ffff
2232002:bcd:e000::/362002:bcd:efff:ffff:ffff:ffff:ffff:ffff
2242002:bcd:f000::/362002:bcd:ffff:ffff:ffff:ffff:ffff:ffff
2252002:bce::/362002:bce:fff:ffff:ffff:ffff:ffff:ffff
2262002:bce:1000::/362002:bce:1fff:ffff:ffff:ffff:ffff:ffff
2272002:bce:2000::/362002:bce:2fff:ffff:ffff:ffff:ffff:ffff
2282002:bce:3000::/362002:bce:3fff:ffff:ffff:ffff:ffff:ffff
2292002:bce:4000::/362002:bce:4fff:ffff:ffff:ffff:ffff:ffff
2302002:bce:5000::/362002:bce:5fff:ffff:ffff:ffff:ffff:ffff
2312002:bce:6000::/362002:bce:6fff:ffff:ffff:ffff:ffff:ffff
2322002:bce:7000::/362002:bce:7fff:ffff:ffff:ffff:ffff:ffff
2332002:bce:8000::/362002:bce:8fff:ffff:ffff:ffff:ffff:ffff
2342002:bce:9000::/362002:bce:9fff:ffff:ffff:ffff:ffff:ffff
2352002:bce:a000::/362002:bce:afff:ffff:ffff:ffff:ffff:ffff
2362002:bce:b000::/362002:bce:bfff:ffff:ffff:ffff:ffff:ffff
2372002:bce:c000::/362002:bce:cfff:ffff:ffff:ffff:ffff:ffff
2382002:bce:d000::/362002:bce:dfff:ffff:ffff:ffff:ffff:ffff
2392002:bce:e000::/362002:bce:efff:ffff:ffff:ffff:ffff:ffff
2402002:bce:f000::/362002:bce:ffff:ffff:ffff:ffff:ffff:ffff
2412002:bcf::/362002:bcf:fff:ffff:ffff:ffff:ffff:ffff
2422002:bcf:1000::/362002:bcf:1fff:ffff:ffff:ffff:ffff:ffff
2432002:bcf:2000::/362002:bcf:2fff:ffff:ffff:ffff:ffff:ffff
2442002:bcf:3000::/362002:bcf:3fff:ffff:ffff:ffff:ffff:ffff
2452002:bcf:4000::/362002:bcf:4fff:ffff:ffff:ffff:ffff:ffff
2462002:bcf:5000::/362002:bcf:5fff:ffff:ffff:ffff:ffff:ffff
2472002:bcf:6000::/362002:bcf:6fff:ffff:ffff:ffff:ffff:ffff
2482002:bcf:7000::/362002:bcf:7fff:ffff:ffff:ffff:ffff:ffff
2492002:bcf:8000::/362002:bcf:8fff:ffff:ffff:ffff:ffff:ffff
2502002:bcf:9000::/362002:bcf:9fff:ffff:ffff:ffff:ffff:ffff
2512002:bcf:a000::/362002:bcf:afff:ffff:ffff:ffff:ffff:ffff
2522002:bcf:b000::/362002:bcf:bfff:ffff:ffff:ffff:ffff:ffff
2532002:bcf:c000::/362002:bcf:cfff:ffff:ffff:ffff:ffff:ffff
2542002:bcf:d000::/362002:bcf:dfff:ffff:ffff:ffff:ffff:ffff
2552002:bcf:e000::/362002:bcf:efff:ffff:ffff:ffff:ffff:ffff
2562002:bcf:f000::/362002:bcf: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.