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/100
Addresses268,435,456
/64 networksPart of one
Network
2001:db8::470f:9000:0/100
First address
2001:db8::470f:9000:0
Last address
2001:db8::470f:9fff:ffff
Addresses
268,435,456
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
2001:0db8:0000:0000:0000:470f:9000:0000
Type
Documentation 2001:db8::/32
For examples; never used on a network
Reverse DNS zone
9.f.0.7.4.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
Split into smaller subnets/116
/101 (2)/102 (4)/103 (8)/104 (16)/108 (256)/112 (4,096)/116 (65,536)

2001:db8::470f:9000:0/100 makes 65,536 subnets of /116; the first 256 are listed.

Subnets
#SubnetLast address
12001:db8::470f:9000:0/1162001:db8::470f:9000:fff
22001:db8::470f:9000:1000/1162001:db8::470f:9000:1fff
32001:db8::470f:9000:2000/1162001:db8::470f:9000:2fff
42001:db8::470f:9000:3000/1162001:db8::470f:9000:3fff
52001:db8::470f:9000:4000/1162001:db8::470f:9000:4fff
62001:db8::470f:9000:5000/1162001:db8::470f:9000:5fff
72001:db8::470f:9000:6000/1162001:db8::470f:9000:6fff
82001:db8::470f:9000:7000/1162001:db8::470f:9000:7fff
92001:db8::470f:9000:8000/1162001:db8::470f:9000:8fff
102001:db8::470f:9000:9000/1162001:db8::470f:9000:9fff
112001:db8::470f:9000:a000/1162001:db8::470f:9000:afff
122001:db8::470f:9000:b000/1162001:db8::470f:9000:bfff
132001:db8::470f:9000:c000/1162001:db8::470f:9000:cfff
142001:db8::470f:9000:d000/1162001:db8::470f:9000:dfff
152001:db8::470f:9000:e000/1162001:db8::470f:9000:efff
162001:db8::470f:9000:f000/1162001:db8::470f:9000:ffff
172001:db8::470f:9001:0/1162001:db8::470f:9001:fff
182001:db8::470f:9001:1000/1162001:db8::470f:9001:1fff
192001:db8::470f:9001:2000/1162001:db8::470f:9001:2fff
202001:db8::470f:9001:3000/1162001:db8::470f:9001:3fff
212001:db8::470f:9001:4000/1162001:db8::470f:9001:4fff
222001:db8::470f:9001:5000/1162001:db8::470f:9001:5fff
232001:db8::470f:9001:6000/1162001:db8::470f:9001:6fff
242001:db8::470f:9001:7000/1162001:db8::470f:9001:7fff
252001:db8::470f:9001:8000/1162001:db8::470f:9001:8fff
262001:db8::470f:9001:9000/1162001:db8::470f:9001:9fff
272001:db8::470f:9001:a000/1162001:db8::470f:9001:afff
282001:db8::470f:9001:b000/1162001:db8::470f:9001:bfff
292001:db8::470f:9001:c000/1162001:db8::470f:9001:cfff
302001:db8::470f:9001:d000/1162001:db8::470f:9001:dfff
312001:db8::470f:9001:e000/1162001:db8::470f:9001:efff
322001:db8::470f:9001:f000/1162001:db8::470f:9001:ffff
332001:db8::470f:9002:0/1162001:db8::470f:9002:fff
342001:db8::470f:9002:1000/1162001:db8::470f:9002:1fff
352001:db8::470f:9002:2000/1162001:db8::470f:9002:2fff
362001:db8::470f:9002:3000/1162001:db8::470f:9002:3fff
372001:db8::470f:9002:4000/1162001:db8::470f:9002:4fff
382001:db8::470f:9002:5000/1162001:db8::470f:9002:5fff
392001:db8::470f:9002:6000/1162001:db8::470f:9002:6fff
402001:db8::470f:9002:7000/1162001:db8::470f:9002:7fff
412001:db8::470f:9002:8000/1162001:db8::470f:9002:8fff
422001:db8::470f:9002:9000/1162001:db8::470f:9002:9fff
432001:db8::470f:9002:a000/1162001:db8::470f:9002:afff
442001:db8::470f:9002:b000/1162001:db8::470f:9002:bfff
452001:db8::470f:9002:c000/1162001:db8::470f:9002:cfff
462001:db8::470f:9002:d000/1162001:db8::470f:9002:dfff
472001:db8::470f:9002:e000/1162001:db8::470f:9002:efff
482001:db8::470f:9002:f000/1162001:db8::470f:9002:ffff
492001:db8::470f:9003:0/1162001:db8::470f:9003:fff
502001:db8::470f:9003:1000/1162001:db8::470f:9003:1fff
512001:db8::470f:9003:2000/1162001:db8::470f:9003:2fff
522001:db8::470f:9003:3000/1162001:db8::470f:9003:3fff
532001:db8::470f:9003:4000/1162001:db8::470f:9003:4fff
542001:db8::470f:9003:5000/1162001:db8::470f:9003:5fff
552001:db8::470f:9003:6000/1162001:db8::470f:9003:6fff
562001:db8::470f:9003:7000/1162001:db8::470f:9003:7fff
572001:db8::470f:9003:8000/1162001:db8::470f:9003:8fff
582001:db8::470f:9003:9000/1162001:db8::470f:9003:9fff
592001:db8::470f:9003:a000/1162001:db8::470f:9003:afff
602001:db8::470f:9003:b000/1162001:db8::470f:9003:bfff
612001:db8::470f:9003:c000/1162001:db8::470f:9003:cfff
622001:db8::470f:9003:d000/1162001:db8::470f:9003:dfff
632001:db8::470f:9003:e000/1162001:db8::470f:9003:efff
642001:db8::470f:9003:f000/1162001:db8::470f:9003:ffff
652001:db8::470f:9004:0/1162001:db8::470f:9004:fff
662001:db8::470f:9004:1000/1162001:db8::470f:9004:1fff
672001:db8::470f:9004:2000/1162001:db8::470f:9004:2fff
682001:db8::470f:9004:3000/1162001:db8::470f:9004:3fff
692001:db8::470f:9004:4000/1162001:db8::470f:9004:4fff
702001:db8::470f:9004:5000/1162001:db8::470f:9004:5fff
712001:db8::470f:9004:6000/1162001:db8::470f:9004:6fff
722001:db8::470f:9004:7000/1162001:db8::470f:9004:7fff
732001:db8::470f:9004:8000/1162001:db8::470f:9004:8fff
742001:db8::470f:9004:9000/1162001:db8::470f:9004:9fff
752001:db8::470f:9004:a000/1162001:db8::470f:9004:afff
762001:db8::470f:9004:b000/1162001:db8::470f:9004:bfff
772001:db8::470f:9004:c000/1162001:db8::470f:9004:cfff
782001:db8::470f:9004:d000/1162001:db8::470f:9004:dfff
792001:db8::470f:9004:e000/1162001:db8::470f:9004:efff
802001:db8::470f:9004:f000/1162001:db8::470f:9004:ffff
812001:db8::470f:9005:0/1162001:db8::470f:9005:fff
822001:db8::470f:9005:1000/1162001:db8::470f:9005:1fff
832001:db8::470f:9005:2000/1162001:db8::470f:9005:2fff
842001:db8::470f:9005:3000/1162001:db8::470f:9005:3fff
852001:db8::470f:9005:4000/1162001:db8::470f:9005:4fff
862001:db8::470f:9005:5000/1162001:db8::470f:9005:5fff
872001:db8::470f:9005:6000/1162001:db8::470f:9005:6fff
882001:db8::470f:9005:7000/1162001:db8::470f:9005:7fff
892001:db8::470f:9005:8000/1162001:db8::470f:9005:8fff
902001:db8::470f:9005:9000/1162001:db8::470f:9005:9fff
912001:db8::470f:9005:a000/1162001:db8::470f:9005:afff
922001:db8::470f:9005:b000/1162001:db8::470f:9005:bfff
932001:db8::470f:9005:c000/1162001:db8::470f:9005:cfff
942001:db8::470f:9005:d000/1162001:db8::470f:9005:dfff
952001:db8::470f:9005:e000/1162001:db8::470f:9005:efff
962001:db8::470f:9005:f000/1162001:db8::470f:9005:ffff
972001:db8::470f:9006:0/1162001:db8::470f:9006:fff
982001:db8::470f:9006:1000/1162001:db8::470f:9006:1fff
992001:db8::470f:9006:2000/1162001:db8::470f:9006:2fff
1002001:db8::470f:9006:3000/1162001:db8::470f:9006:3fff
1012001:db8::470f:9006:4000/1162001:db8::470f:9006:4fff
1022001:db8::470f:9006:5000/1162001:db8::470f:9006:5fff
1032001:db8::470f:9006:6000/1162001:db8::470f:9006:6fff
1042001:db8::470f:9006:7000/1162001:db8::470f:9006:7fff
1052001:db8::470f:9006:8000/1162001:db8::470f:9006:8fff
1062001:db8::470f:9006:9000/1162001:db8::470f:9006:9fff
1072001:db8::470f:9006:a000/1162001:db8::470f:9006:afff
1082001:db8::470f:9006:b000/1162001:db8::470f:9006:bfff
1092001:db8::470f:9006:c000/1162001:db8::470f:9006:cfff
1102001:db8::470f:9006:d000/1162001:db8::470f:9006:dfff
1112001:db8::470f:9006:e000/1162001:db8::470f:9006:efff
1122001:db8::470f:9006:f000/1162001:db8::470f:9006:ffff
1132001:db8::470f:9007:0/1162001:db8::470f:9007:fff
1142001:db8::470f:9007:1000/1162001:db8::470f:9007:1fff
1152001:db8::470f:9007:2000/1162001:db8::470f:9007:2fff
1162001:db8::470f:9007:3000/1162001:db8::470f:9007:3fff
1172001:db8::470f:9007:4000/1162001:db8::470f:9007:4fff
1182001:db8::470f:9007:5000/1162001:db8::470f:9007:5fff
1192001:db8::470f:9007:6000/1162001:db8::470f:9007:6fff
1202001:db8::470f:9007:7000/1162001:db8::470f:9007:7fff
1212001:db8::470f:9007:8000/1162001:db8::470f:9007:8fff
1222001:db8::470f:9007:9000/1162001:db8::470f:9007:9fff
1232001:db8::470f:9007:a000/1162001:db8::470f:9007:afff
1242001:db8::470f:9007:b000/1162001:db8::470f:9007:bfff
1252001:db8::470f:9007:c000/1162001:db8::470f:9007:cfff
1262001:db8::470f:9007:d000/1162001:db8::470f:9007:dfff
1272001:db8::470f:9007:e000/1162001:db8::470f:9007:efff
1282001:db8::470f:9007:f000/1162001:db8::470f:9007:ffff
1292001:db8::470f:9008:0/1162001:db8::470f:9008:fff
1302001:db8::470f:9008:1000/1162001:db8::470f:9008:1fff
1312001:db8::470f:9008:2000/1162001:db8::470f:9008:2fff
1322001:db8::470f:9008:3000/1162001:db8::470f:9008:3fff
1332001:db8::470f:9008:4000/1162001:db8::470f:9008:4fff
1342001:db8::470f:9008:5000/1162001:db8::470f:9008:5fff
1352001:db8::470f:9008:6000/1162001:db8::470f:9008:6fff
1362001:db8::470f:9008:7000/1162001:db8::470f:9008:7fff
1372001:db8::470f:9008:8000/1162001:db8::470f:9008:8fff
1382001:db8::470f:9008:9000/1162001:db8::470f:9008:9fff
1392001:db8::470f:9008:a000/1162001:db8::470f:9008:afff
1402001:db8::470f:9008:b000/1162001:db8::470f:9008:bfff
1412001:db8::470f:9008:c000/1162001:db8::470f:9008:cfff
1422001:db8::470f:9008:d000/1162001:db8::470f:9008:dfff
1432001:db8::470f:9008:e000/1162001:db8::470f:9008:efff
1442001:db8::470f:9008:f000/1162001:db8::470f:9008:ffff
1452001:db8::470f:9009:0/1162001:db8::470f:9009:fff
1462001:db8::470f:9009:1000/1162001:db8::470f:9009:1fff
1472001:db8::470f:9009:2000/1162001:db8::470f:9009:2fff
1482001:db8::470f:9009:3000/1162001:db8::470f:9009:3fff
1492001:db8::470f:9009:4000/1162001:db8::470f:9009:4fff
1502001:db8::470f:9009:5000/1162001:db8::470f:9009:5fff
1512001:db8::470f:9009:6000/1162001:db8::470f:9009:6fff
1522001:db8::470f:9009:7000/1162001:db8::470f:9009:7fff
1532001:db8::470f:9009:8000/1162001:db8::470f:9009:8fff
1542001:db8::470f:9009:9000/1162001:db8::470f:9009:9fff
1552001:db8::470f:9009:a000/1162001:db8::470f:9009:afff
1562001:db8::470f:9009:b000/1162001:db8::470f:9009:bfff
1572001:db8::470f:9009:c000/1162001:db8::470f:9009:cfff
1582001:db8::470f:9009:d000/1162001:db8::470f:9009:dfff
1592001:db8::470f:9009:e000/1162001:db8::470f:9009:efff
1602001:db8::470f:9009:f000/1162001:db8::470f:9009:ffff
1612001:db8::470f:900a:0/1162001:db8::470f:900a:fff
1622001:db8::470f:900a:1000/1162001:db8::470f:900a:1fff
1632001:db8::470f:900a:2000/1162001:db8::470f:900a:2fff
1642001:db8::470f:900a:3000/1162001:db8::470f:900a:3fff
1652001:db8::470f:900a:4000/1162001:db8::470f:900a:4fff
1662001:db8::470f:900a:5000/1162001:db8::470f:900a:5fff
1672001:db8::470f:900a:6000/1162001:db8::470f:900a:6fff
1682001:db8::470f:900a:7000/1162001:db8::470f:900a:7fff
1692001:db8::470f:900a:8000/1162001:db8::470f:900a:8fff
1702001:db8::470f:900a:9000/1162001:db8::470f:900a:9fff
1712001:db8::470f:900a:a000/1162001:db8::470f:900a:afff
1722001:db8::470f:900a:b000/1162001:db8::470f:900a:bfff
1732001:db8::470f:900a:c000/1162001:db8::470f:900a:cfff
1742001:db8::470f:900a:d000/1162001:db8::470f:900a:dfff
1752001:db8::470f:900a:e000/1162001:db8::470f:900a:efff
1762001:db8::470f:900a:f000/1162001:db8::470f:900a:ffff
1772001:db8::470f:900b:0/1162001:db8::470f:900b:fff
1782001:db8::470f:900b:1000/1162001:db8::470f:900b:1fff
1792001:db8::470f:900b:2000/1162001:db8::470f:900b:2fff
1802001:db8::470f:900b:3000/1162001:db8::470f:900b:3fff
1812001:db8::470f:900b:4000/1162001:db8::470f:900b:4fff
1822001:db8::470f:900b:5000/1162001:db8::470f:900b:5fff
1832001:db8::470f:900b:6000/1162001:db8::470f:900b:6fff
1842001:db8::470f:900b:7000/1162001:db8::470f:900b:7fff
1852001:db8::470f:900b:8000/1162001:db8::470f:900b:8fff
1862001:db8::470f:900b:9000/1162001:db8::470f:900b:9fff
1872001:db8::470f:900b:a000/1162001:db8::470f:900b:afff
1882001:db8::470f:900b:b000/1162001:db8::470f:900b:bfff
1892001:db8::470f:900b:c000/1162001:db8::470f:900b:cfff
1902001:db8::470f:900b:d000/1162001:db8::470f:900b:dfff
1912001:db8::470f:900b:e000/1162001:db8::470f:900b:efff
1922001:db8::470f:900b:f000/1162001:db8::470f:900b:ffff
1932001:db8::470f:900c:0/1162001:db8::470f:900c:fff
1942001:db8::470f:900c:1000/1162001:db8::470f:900c:1fff
1952001:db8::470f:900c:2000/1162001:db8::470f:900c:2fff
1962001:db8::470f:900c:3000/1162001:db8::470f:900c:3fff
1972001:db8::470f:900c:4000/1162001:db8::470f:900c:4fff
1982001:db8::470f:900c:5000/1162001:db8::470f:900c:5fff
1992001:db8::470f:900c:6000/1162001:db8::470f:900c:6fff
2002001:db8::470f:900c:7000/1162001:db8::470f:900c:7fff
2012001:db8::470f:900c:8000/1162001:db8::470f:900c:8fff
2022001:db8::470f:900c:9000/1162001:db8::470f:900c:9fff
2032001:db8::470f:900c:a000/1162001:db8::470f:900c:afff
2042001:db8::470f:900c:b000/1162001:db8::470f:900c:bfff
2052001:db8::470f:900c:c000/1162001:db8::470f:900c:cfff
2062001:db8::470f:900c:d000/1162001:db8::470f:900c:dfff
2072001:db8::470f:900c:e000/1162001:db8::470f:900c:efff
2082001:db8::470f:900c:f000/1162001:db8::470f:900c:ffff
2092001:db8::470f:900d:0/1162001:db8::470f:900d:fff
2102001:db8::470f:900d:1000/1162001:db8::470f:900d:1fff
2112001:db8::470f:900d:2000/1162001:db8::470f:900d:2fff
2122001:db8::470f:900d:3000/1162001:db8::470f:900d:3fff
2132001:db8::470f:900d:4000/1162001:db8::470f:900d:4fff
2142001:db8::470f:900d:5000/1162001:db8::470f:900d:5fff
2152001:db8::470f:900d:6000/1162001:db8::470f:900d:6fff
2162001:db8::470f:900d:7000/1162001:db8::470f:900d:7fff
2172001:db8::470f:900d:8000/1162001:db8::470f:900d:8fff
2182001:db8::470f:900d:9000/1162001:db8::470f:900d:9fff
2192001:db8::470f:900d:a000/1162001:db8::470f:900d:afff
2202001:db8::470f:900d:b000/1162001:db8::470f:900d:bfff
2212001:db8::470f:900d:c000/1162001:db8::470f:900d:cfff
2222001:db8::470f:900d:d000/1162001:db8::470f:900d:dfff
2232001:db8::470f:900d:e000/1162001:db8::470f:900d:efff
2242001:db8::470f:900d:f000/1162001:db8::470f:900d:ffff
2252001:db8::470f:900e:0/1162001:db8::470f:900e:fff
2262001:db8::470f:900e:1000/1162001:db8::470f:900e:1fff
2272001:db8::470f:900e:2000/1162001:db8::470f:900e:2fff
2282001:db8::470f:900e:3000/1162001:db8::470f:900e:3fff
2292001:db8::470f:900e:4000/1162001:db8::470f:900e:4fff
2302001:db8::470f:900e:5000/1162001:db8::470f:900e:5fff
2312001:db8::470f:900e:6000/1162001:db8::470f:900e:6fff
2322001:db8::470f:900e:7000/1162001:db8::470f:900e:7fff
2332001:db8::470f:900e:8000/1162001:db8::470f:900e:8fff
2342001:db8::470f:900e:9000/1162001:db8::470f:900e:9fff
2352001:db8::470f:900e:a000/1162001:db8::470f:900e:afff
2362001:db8::470f:900e:b000/1162001:db8::470f:900e:bfff
2372001:db8::470f:900e:c000/1162001:db8::470f:900e:cfff
2382001:db8::470f:900e:d000/1162001:db8::470f:900e:dfff
2392001:db8::470f:900e:e000/1162001:db8::470f:900e:efff
2402001:db8::470f:900e:f000/1162001:db8::470f:900e:ffff
2412001:db8::470f:900f:0/1162001:db8::470f:900f:fff
2422001:db8::470f:900f:1000/1162001:db8::470f:900f:1fff
2432001:db8::470f:900f:2000/1162001:db8::470f:900f:2fff
2442001:db8::470f:900f:3000/1162001:db8::470f:900f:3fff
2452001:db8::470f:900f:4000/1162001:db8::470f:900f:4fff
2462001:db8::470f:900f:5000/1162001:db8::470f:900f:5fff
2472001:db8::470f:900f:6000/1162001:db8::470f:900f:6fff
2482001:db8::470f:900f:7000/1162001:db8::470f:900f:7fff
2492001:db8::470f:900f:8000/1162001:db8::470f:900f:8fff
2502001:db8::470f:900f:9000/1162001:db8::470f:900f:9fff
2512001:db8::470f:900f:a000/1162001:db8::470f:900f:afff
2522001:db8::470f:900f:b000/1162001:db8::470f:900f:bfff
2532001:db8::470f:900f:c000/1162001:db8::470f:900f:cfff
2542001:db8::470f:900f:d000/1162001:db8::470f:900f:dfff
2552001:db8::470f:900f:e000/1162001:db8::470f:900f:efff
2562001:db8::470f:900f:f000/1162001:db8::470f:900f: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.