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/104
Addresses16,777,216
/64 networksPart of one
Network
64:ff9b::b300:0/104
First address
64:ff9b::b300:0
Last address
64:ff9b::b3ff:ffff
Addresses
16,777,216
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
0064:ff9b:0000:0000:0000:0000:b300:0000
Type
NAT64 64:ff9b::/96
IPv4 addresses reached through a NAT64 gateway
Reverse DNS zone
3.b.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.b.9.f.f.4.6.0.0.ip6.arpa
Split into smaller subnets/112
/105 (2)/106 (4)/107 (8)/108 (16)/112 (256)/116 (4,096)/120 (65,536)

64:ff9b::b300:0/104 makes 256 subnets of /112.

Subnets
#SubnetLast address
164:ff9b::b300:0/11264:ff9b::b300:ffff
264:ff9b::b301:0/11264:ff9b::b301:ffff
364:ff9b::b302:0/11264:ff9b::b302:ffff
464:ff9b::b303:0/11264:ff9b::b303:ffff
564:ff9b::b304:0/11264:ff9b::b304:ffff
664:ff9b::b305:0/11264:ff9b::b305:ffff
764:ff9b::b306:0/11264:ff9b::b306:ffff
864:ff9b::b307:0/11264:ff9b::b307:ffff
964:ff9b::b308:0/11264:ff9b::b308:ffff
1064:ff9b::b309:0/11264:ff9b::b309:ffff
1164:ff9b::b30a:0/11264:ff9b::b30a:ffff
1264:ff9b::b30b:0/11264:ff9b::b30b:ffff
1364:ff9b::b30c:0/11264:ff9b::b30c:ffff
1464:ff9b::b30d:0/11264:ff9b::b30d:ffff
1564:ff9b::b30e:0/11264:ff9b::b30e:ffff
1664:ff9b::b30f:0/11264:ff9b::b30f:ffff
1764:ff9b::b310:0/11264:ff9b::b310:ffff
1864:ff9b::b311:0/11264:ff9b::b311:ffff
1964:ff9b::b312:0/11264:ff9b::b312:ffff
2064:ff9b::b313:0/11264:ff9b::b313:ffff
2164:ff9b::b314:0/11264:ff9b::b314:ffff
2264:ff9b::b315:0/11264:ff9b::b315:ffff
2364:ff9b::b316:0/11264:ff9b::b316:ffff
2464:ff9b::b317:0/11264:ff9b::b317:ffff
2564:ff9b::b318:0/11264:ff9b::b318:ffff
2664:ff9b::b319:0/11264:ff9b::b319:ffff
2764:ff9b::b31a:0/11264:ff9b::b31a:ffff
2864:ff9b::b31b:0/11264:ff9b::b31b:ffff
2964:ff9b::b31c:0/11264:ff9b::b31c:ffff
3064:ff9b::b31d:0/11264:ff9b::b31d:ffff
3164:ff9b::b31e:0/11264:ff9b::b31e:ffff
3264:ff9b::b31f:0/11264:ff9b::b31f:ffff
3364:ff9b::b320:0/11264:ff9b::b320:ffff
3464:ff9b::b321:0/11264:ff9b::b321:ffff
3564:ff9b::b322:0/11264:ff9b::b322:ffff
3664:ff9b::b323:0/11264:ff9b::b323:ffff
3764:ff9b::b324:0/11264:ff9b::b324:ffff
3864:ff9b::b325:0/11264:ff9b::b325:ffff
3964:ff9b::b326:0/11264:ff9b::b326:ffff
4064:ff9b::b327:0/11264:ff9b::b327:ffff
4164:ff9b::b328:0/11264:ff9b::b328:ffff
4264:ff9b::b329:0/11264:ff9b::b329:ffff
4364:ff9b::b32a:0/11264:ff9b::b32a:ffff
4464:ff9b::b32b:0/11264:ff9b::b32b:ffff
4564:ff9b::b32c:0/11264:ff9b::b32c:ffff
4664:ff9b::b32d:0/11264:ff9b::b32d:ffff
4764:ff9b::b32e:0/11264:ff9b::b32e:ffff
4864:ff9b::b32f:0/11264:ff9b::b32f:ffff
4964:ff9b::b330:0/11264:ff9b::b330:ffff
5064:ff9b::b331:0/11264:ff9b::b331:ffff
5164:ff9b::b332:0/11264:ff9b::b332:ffff
5264:ff9b::b333:0/11264:ff9b::b333:ffff
5364:ff9b::b334:0/11264:ff9b::b334:ffff
5464:ff9b::b335:0/11264:ff9b::b335:ffff
5564:ff9b::b336:0/11264:ff9b::b336:ffff
5664:ff9b::b337:0/11264:ff9b::b337:ffff
5764:ff9b::b338:0/11264:ff9b::b338:ffff
5864:ff9b::b339:0/11264:ff9b::b339:ffff
5964:ff9b::b33a:0/11264:ff9b::b33a:ffff
6064:ff9b::b33b:0/11264:ff9b::b33b:ffff
6164:ff9b::b33c:0/11264:ff9b::b33c:ffff
6264:ff9b::b33d:0/11264:ff9b::b33d:ffff
6364:ff9b::b33e:0/11264:ff9b::b33e:ffff
6464:ff9b::b33f:0/11264:ff9b::b33f:ffff
6564:ff9b::b340:0/11264:ff9b::b340:ffff
6664:ff9b::b341:0/11264:ff9b::b341:ffff
6764:ff9b::b342:0/11264:ff9b::b342:ffff
6864:ff9b::b343:0/11264:ff9b::b343:ffff
6964:ff9b::b344:0/11264:ff9b::b344:ffff
7064:ff9b::b345:0/11264:ff9b::b345:ffff
7164:ff9b::b346:0/11264:ff9b::b346:ffff
7264:ff9b::b347:0/11264:ff9b::b347:ffff
7364:ff9b::b348:0/11264:ff9b::b348:ffff
7464:ff9b::b349:0/11264:ff9b::b349:ffff
7564:ff9b::b34a:0/11264:ff9b::b34a:ffff
7664:ff9b::b34b:0/11264:ff9b::b34b:ffff
7764:ff9b::b34c:0/11264:ff9b::b34c:ffff
7864:ff9b::b34d:0/11264:ff9b::b34d:ffff
7964:ff9b::b34e:0/11264:ff9b::b34e:ffff
8064:ff9b::b34f:0/11264:ff9b::b34f:ffff
8164:ff9b::b350:0/11264:ff9b::b350:ffff
8264:ff9b::b351:0/11264:ff9b::b351:ffff
8364:ff9b::b352:0/11264:ff9b::b352:ffff
8464:ff9b::b353:0/11264:ff9b::b353:ffff
8564:ff9b::b354:0/11264:ff9b::b354:ffff
8664:ff9b::b355:0/11264:ff9b::b355:ffff
8764:ff9b::b356:0/11264:ff9b::b356:ffff
8864:ff9b::b357:0/11264:ff9b::b357:ffff
8964:ff9b::b358:0/11264:ff9b::b358:ffff
9064:ff9b::b359:0/11264:ff9b::b359:ffff
9164:ff9b::b35a:0/11264:ff9b::b35a:ffff
9264:ff9b::b35b:0/11264:ff9b::b35b:ffff
9364:ff9b::b35c:0/11264:ff9b::b35c:ffff
9464:ff9b::b35d:0/11264:ff9b::b35d:ffff
9564:ff9b::b35e:0/11264:ff9b::b35e:ffff
9664:ff9b::b35f:0/11264:ff9b::b35f:ffff
9764:ff9b::b360:0/11264:ff9b::b360:ffff
9864:ff9b::b361:0/11264:ff9b::b361:ffff
9964:ff9b::b362:0/11264:ff9b::b362:ffff
10064:ff9b::b363:0/11264:ff9b::b363:ffff
10164:ff9b::b364:0/11264:ff9b::b364:ffff
10264:ff9b::b365:0/11264:ff9b::b365:ffff
10364:ff9b::b366:0/11264:ff9b::b366:ffff
10464:ff9b::b367:0/11264:ff9b::b367:ffff
10564:ff9b::b368:0/11264:ff9b::b368:ffff
10664:ff9b::b369:0/11264:ff9b::b369:ffff
10764:ff9b::b36a:0/11264:ff9b::b36a:ffff
10864:ff9b::b36b:0/11264:ff9b::b36b:ffff
10964:ff9b::b36c:0/11264:ff9b::b36c:ffff
11064:ff9b::b36d:0/11264:ff9b::b36d:ffff
11164:ff9b::b36e:0/11264:ff9b::b36e:ffff
11264:ff9b::b36f:0/11264:ff9b::b36f:ffff
11364:ff9b::b370:0/11264:ff9b::b370:ffff
11464:ff9b::b371:0/11264:ff9b::b371:ffff
11564:ff9b::b372:0/11264:ff9b::b372:ffff
11664:ff9b::b373:0/11264:ff9b::b373:ffff
11764:ff9b::b374:0/11264:ff9b::b374:ffff
11864:ff9b::b375:0/11264:ff9b::b375:ffff
11964:ff9b::b376:0/11264:ff9b::b376:ffff
12064:ff9b::b377:0/11264:ff9b::b377:ffff
12164:ff9b::b378:0/11264:ff9b::b378:ffff
12264:ff9b::b379:0/11264:ff9b::b379:ffff
12364:ff9b::b37a:0/11264:ff9b::b37a:ffff
12464:ff9b::b37b:0/11264:ff9b::b37b:ffff
12564:ff9b::b37c:0/11264:ff9b::b37c:ffff
12664:ff9b::b37d:0/11264:ff9b::b37d:ffff
12764:ff9b::b37e:0/11264:ff9b::b37e:ffff
12864:ff9b::b37f:0/11264:ff9b::b37f:ffff
12964:ff9b::b380:0/11264:ff9b::b380:ffff
13064:ff9b::b381:0/11264:ff9b::b381:ffff
13164:ff9b::b382:0/11264:ff9b::b382:ffff
13264:ff9b::b383:0/11264:ff9b::b383:ffff
13364:ff9b::b384:0/11264:ff9b::b384:ffff
13464:ff9b::b385:0/11264:ff9b::b385:ffff
13564:ff9b::b386:0/11264:ff9b::b386:ffff
13664:ff9b::b387:0/11264:ff9b::b387:ffff
13764:ff9b::b388:0/11264:ff9b::b388:ffff
13864:ff9b::b389:0/11264:ff9b::b389:ffff
13964:ff9b::b38a:0/11264:ff9b::b38a:ffff
14064:ff9b::b38b:0/11264:ff9b::b38b:ffff
14164:ff9b::b38c:0/11264:ff9b::b38c:ffff
14264:ff9b::b38d:0/11264:ff9b::b38d:ffff
14364:ff9b::b38e:0/11264:ff9b::b38e:ffff
14464:ff9b::b38f:0/11264:ff9b::b38f:ffff
14564:ff9b::b390:0/11264:ff9b::b390:ffff
14664:ff9b::b391:0/11264:ff9b::b391:ffff
14764:ff9b::b392:0/11264:ff9b::b392:ffff
14864:ff9b::b393:0/11264:ff9b::b393:ffff
14964:ff9b::b394:0/11264:ff9b::b394:ffff
15064:ff9b::b395:0/11264:ff9b::b395:ffff
15164:ff9b::b396:0/11264:ff9b::b396:ffff
15264:ff9b::b397:0/11264:ff9b::b397:ffff
15364:ff9b::b398:0/11264:ff9b::b398:ffff
15464:ff9b::b399:0/11264:ff9b::b399:ffff
15564:ff9b::b39a:0/11264:ff9b::b39a:ffff
15664:ff9b::b39b:0/11264:ff9b::b39b:ffff
15764:ff9b::b39c:0/11264:ff9b::b39c:ffff
15864:ff9b::b39d:0/11264:ff9b::b39d:ffff
15964:ff9b::b39e:0/11264:ff9b::b39e:ffff
16064:ff9b::b39f:0/11264:ff9b::b39f:ffff
16164:ff9b::b3a0:0/11264:ff9b::b3a0:ffff
16264:ff9b::b3a1:0/11264:ff9b::b3a1:ffff
16364:ff9b::b3a2:0/11264:ff9b::b3a2:ffff
16464:ff9b::b3a3:0/11264:ff9b::b3a3:ffff
16564:ff9b::b3a4:0/11264:ff9b::b3a4:ffff
16664:ff9b::b3a5:0/11264:ff9b::b3a5:ffff
16764:ff9b::b3a6:0/11264:ff9b::b3a6:ffff
16864:ff9b::b3a7:0/11264:ff9b::b3a7:ffff
16964:ff9b::b3a8:0/11264:ff9b::b3a8:ffff
17064:ff9b::b3a9:0/11264:ff9b::b3a9:ffff
17164:ff9b::b3aa:0/11264:ff9b::b3aa:ffff
17264:ff9b::b3ab:0/11264:ff9b::b3ab:ffff
17364:ff9b::b3ac:0/11264:ff9b::b3ac:ffff
17464:ff9b::b3ad:0/11264:ff9b::b3ad:ffff
17564:ff9b::b3ae:0/11264:ff9b::b3ae:ffff
17664:ff9b::b3af:0/11264:ff9b::b3af:ffff
17764:ff9b::b3b0:0/11264:ff9b::b3b0:ffff
17864:ff9b::b3b1:0/11264:ff9b::b3b1:ffff
17964:ff9b::b3b2:0/11264:ff9b::b3b2:ffff
18064:ff9b::b3b3:0/11264:ff9b::b3b3:ffff
18164:ff9b::b3b4:0/11264:ff9b::b3b4:ffff
18264:ff9b::b3b5:0/11264:ff9b::b3b5:ffff
18364:ff9b::b3b6:0/11264:ff9b::b3b6:ffff
18464:ff9b::b3b7:0/11264:ff9b::b3b7:ffff
18564:ff9b::b3b8:0/11264:ff9b::b3b8:ffff
18664:ff9b::b3b9:0/11264:ff9b::b3b9:ffff
18764:ff9b::b3ba:0/11264:ff9b::b3ba:ffff
18864:ff9b::b3bb:0/11264:ff9b::b3bb:ffff
18964:ff9b::b3bc:0/11264:ff9b::b3bc:ffff
19064:ff9b::b3bd:0/11264:ff9b::b3bd:ffff
19164:ff9b::b3be:0/11264:ff9b::b3be:ffff
19264:ff9b::b3bf:0/11264:ff9b::b3bf:ffff
19364:ff9b::b3c0:0/11264:ff9b::b3c0:ffff
19464:ff9b::b3c1:0/11264:ff9b::b3c1:ffff
19564:ff9b::b3c2:0/11264:ff9b::b3c2:ffff
19664:ff9b::b3c3:0/11264:ff9b::b3c3:ffff
19764:ff9b::b3c4:0/11264:ff9b::b3c4:ffff
19864:ff9b::b3c5:0/11264:ff9b::b3c5:ffff
19964:ff9b::b3c6:0/11264:ff9b::b3c6:ffff
20064:ff9b::b3c7:0/11264:ff9b::b3c7:ffff
20164:ff9b::b3c8:0/11264:ff9b::b3c8:ffff
20264:ff9b::b3c9:0/11264:ff9b::b3c9:ffff
20364:ff9b::b3ca:0/11264:ff9b::b3ca:ffff
20464:ff9b::b3cb:0/11264:ff9b::b3cb:ffff
20564:ff9b::b3cc:0/11264:ff9b::b3cc:ffff
20664:ff9b::b3cd:0/11264:ff9b::b3cd:ffff
20764:ff9b::b3ce:0/11264:ff9b::b3ce:ffff
20864:ff9b::b3cf:0/11264:ff9b::b3cf:ffff
20964:ff9b::b3d0:0/11264:ff9b::b3d0:ffff
21064:ff9b::b3d1:0/11264:ff9b::b3d1:ffff
21164:ff9b::b3d2:0/11264:ff9b::b3d2:ffff
21264:ff9b::b3d3:0/11264:ff9b::b3d3:ffff
21364:ff9b::b3d4:0/11264:ff9b::b3d4:ffff
21464:ff9b::b3d5:0/11264:ff9b::b3d5:ffff
21564:ff9b::b3d6:0/11264:ff9b::b3d6:ffff
21664:ff9b::b3d7:0/11264:ff9b::b3d7:ffff
21764:ff9b::b3d8:0/11264:ff9b::b3d8:ffff
21864:ff9b::b3d9:0/11264:ff9b::b3d9:ffff
21964:ff9b::b3da:0/11264:ff9b::b3da:ffff
22064:ff9b::b3db:0/11264:ff9b::b3db:ffff
22164:ff9b::b3dc:0/11264:ff9b::b3dc:ffff
22264:ff9b::b3dd:0/11264:ff9b::b3dd:ffff
22364:ff9b::b3de:0/11264:ff9b::b3de:ffff
22464:ff9b::b3df:0/11264:ff9b::b3df:ffff
22564:ff9b::b3e0:0/11264:ff9b::b3e0:ffff
22664:ff9b::b3e1:0/11264:ff9b::b3e1:ffff
22764:ff9b::b3e2:0/11264:ff9b::b3e2:ffff
22864:ff9b::b3e3:0/11264:ff9b::b3e3:ffff
22964:ff9b::b3e4:0/11264:ff9b::b3e4:ffff
23064:ff9b::b3e5:0/11264:ff9b::b3e5:ffff
23164:ff9b::b3e6:0/11264:ff9b::b3e6:ffff
23264:ff9b::b3e7:0/11264:ff9b::b3e7:ffff
23364:ff9b::b3e8:0/11264:ff9b::b3e8:ffff
23464:ff9b::b3e9:0/11264:ff9b::b3e9:ffff
23564:ff9b::b3ea:0/11264:ff9b::b3ea:ffff
23664:ff9b::b3eb:0/11264:ff9b::b3eb:ffff
23764:ff9b::b3ec:0/11264:ff9b::b3ec:ffff
23864:ff9b::b3ed:0/11264:ff9b::b3ed:ffff
23964:ff9b::b3ee:0/11264:ff9b::b3ee:ffff
24064:ff9b::b3ef:0/11264:ff9b::b3ef:ffff
24164:ff9b::b3f0:0/11264:ff9b::b3f0:ffff
24264:ff9b::b3f1:0/11264:ff9b::b3f1:ffff
24364:ff9b::b3f2:0/11264:ff9b::b3f2:ffff
24464:ff9b::b3f3:0/11264:ff9b::b3f3:ffff
24564:ff9b::b3f4:0/11264:ff9b::b3f4:ffff
24664:ff9b::b3f5:0/11264:ff9b::b3f5:ffff
24764:ff9b::b3f6:0/11264:ff9b::b3f6:ffff
24864:ff9b::b3f7:0/11264:ff9b::b3f7:ffff
24964:ff9b::b3f8:0/11264:ff9b::b3f8:ffff
25064:ff9b::b3f9:0/11264:ff9b::b3f9:ffff
25164:ff9b::b3fa:0/11264:ff9b::b3fa:ffff
25264:ff9b::b3fb:0/11264:ff9b::b3fb:ffff
25364:ff9b::b3fc:0/11264:ff9b::b3fc:ffff
25464:ff9b::b3fd:0/11264:ff9b::b3fd:ffff
25564:ff9b::b3fe:0/11264:ff9b::b3fe:ffff
25664:ff9b::b3ff:0/11264:ff9b::b3ff: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.