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/116
Addresses4,096
/64 networksPart of one
Network
2c19:dd:d9:dd:c25:c25:c001:4000/116
First address
2c19:dd:d9:dd:c25:c25:c001:4000
Last address
2c19:dd:d9:dd:c25:c25:c001:4fff
Addresses
4,096
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
2c19:00dd:00d9:00dd:0c25:0c25:c001:4000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
4.1.0.0.c.5.2.c.0.5.2.c.0.d.d.0.0.9.d.0.0.d.d.0.0.9.1.c.2.ip6.arpa
Split into smaller subnets/127
/117 (2)/118 (4)/119 (8)/120 (16)/124 (256)/127 (2,048)/128 (4,096)

2c19:dd:d9:dd:c25:c25:c001:4000/116 makes 2,048 subnets of /127; the first 256 are listed.

Subnets
#SubnetLast address
12c19:dd:d9:dd:c25:c25:c001:4000/1272c19:dd:d9:dd:c25:c25:c001:4001
22c19:dd:d9:dd:c25:c25:c001:4002/1272c19:dd:d9:dd:c25:c25:c001:4003
32c19:dd:d9:dd:c25:c25:c001:4004/1272c19:dd:d9:dd:c25:c25:c001:4005
42c19:dd:d9:dd:c25:c25:c001:4006/1272c19:dd:d9:dd:c25:c25:c001:4007
52c19:dd:d9:dd:c25:c25:c001:4008/1272c19:dd:d9:dd:c25:c25:c001:4009
62c19:dd:d9:dd:c25:c25:c001:400a/1272c19:dd:d9:dd:c25:c25:c001:400b
72c19:dd:d9:dd:c25:c25:c001:400c/1272c19:dd:d9:dd:c25:c25:c001:400d
82c19:dd:d9:dd:c25:c25:c001:400e/1272c19:dd:d9:dd:c25:c25:c001:400f
92c19:dd:d9:dd:c25:c25:c001:4010/1272c19:dd:d9:dd:c25:c25:c001:4011
102c19:dd:d9:dd:c25:c25:c001:4012/1272c19:dd:d9:dd:c25:c25:c001:4013
112c19:dd:d9:dd:c25:c25:c001:4014/1272c19:dd:d9:dd:c25:c25:c001:4015
122c19:dd:d9:dd:c25:c25:c001:4016/1272c19:dd:d9:dd:c25:c25:c001:4017
132c19:dd:d9:dd:c25:c25:c001:4018/1272c19:dd:d9:dd:c25:c25:c001:4019
142c19:dd:d9:dd:c25:c25:c001:401a/1272c19:dd:d9:dd:c25:c25:c001:401b
152c19:dd:d9:dd:c25:c25:c001:401c/1272c19:dd:d9:dd:c25:c25:c001:401d
162c19:dd:d9:dd:c25:c25:c001:401e/1272c19:dd:d9:dd:c25:c25:c001:401f
172c19:dd:d9:dd:c25:c25:c001:4020/1272c19:dd:d9:dd:c25:c25:c001:4021
182c19:dd:d9:dd:c25:c25:c001:4022/1272c19:dd:d9:dd:c25:c25:c001:4023
192c19:dd:d9:dd:c25:c25:c001:4024/1272c19:dd:d9:dd:c25:c25:c001:4025
202c19:dd:d9:dd:c25:c25:c001:4026/1272c19:dd:d9:dd:c25:c25:c001:4027
212c19:dd:d9:dd:c25:c25:c001:4028/1272c19:dd:d9:dd:c25:c25:c001:4029
222c19:dd:d9:dd:c25:c25:c001:402a/1272c19:dd:d9:dd:c25:c25:c001:402b
232c19:dd:d9:dd:c25:c25:c001:402c/1272c19:dd:d9:dd:c25:c25:c001:402d
242c19:dd:d9:dd:c25:c25:c001:402e/1272c19:dd:d9:dd:c25:c25:c001:402f
252c19:dd:d9:dd:c25:c25:c001:4030/1272c19:dd:d9:dd:c25:c25:c001:4031
262c19:dd:d9:dd:c25:c25:c001:4032/1272c19:dd:d9:dd:c25:c25:c001:4033
272c19:dd:d9:dd:c25:c25:c001:4034/1272c19:dd:d9:dd:c25:c25:c001:4035
282c19:dd:d9:dd:c25:c25:c001:4036/1272c19:dd:d9:dd:c25:c25:c001:4037
292c19:dd:d9:dd:c25:c25:c001:4038/1272c19:dd:d9:dd:c25:c25:c001:4039
302c19:dd:d9:dd:c25:c25:c001:403a/1272c19:dd:d9:dd:c25:c25:c001:403b
312c19:dd:d9:dd:c25:c25:c001:403c/1272c19:dd:d9:dd:c25:c25:c001:403d
322c19:dd:d9:dd:c25:c25:c001:403e/1272c19:dd:d9:dd:c25:c25:c001:403f
332c19:dd:d9:dd:c25:c25:c001:4040/1272c19:dd:d9:dd:c25:c25:c001:4041
342c19:dd:d9:dd:c25:c25:c001:4042/1272c19:dd:d9:dd:c25:c25:c001:4043
352c19:dd:d9:dd:c25:c25:c001:4044/1272c19:dd:d9:dd:c25:c25:c001:4045
362c19:dd:d9:dd:c25:c25:c001:4046/1272c19:dd:d9:dd:c25:c25:c001:4047
372c19:dd:d9:dd:c25:c25:c001:4048/1272c19:dd:d9:dd:c25:c25:c001:4049
382c19:dd:d9:dd:c25:c25:c001:404a/1272c19:dd:d9:dd:c25:c25:c001:404b
392c19:dd:d9:dd:c25:c25:c001:404c/1272c19:dd:d9:dd:c25:c25:c001:404d
402c19:dd:d9:dd:c25:c25:c001:404e/1272c19:dd:d9:dd:c25:c25:c001:404f
412c19:dd:d9:dd:c25:c25:c001:4050/1272c19:dd:d9:dd:c25:c25:c001:4051
422c19:dd:d9:dd:c25:c25:c001:4052/1272c19:dd:d9:dd:c25:c25:c001:4053
432c19:dd:d9:dd:c25:c25:c001:4054/1272c19:dd:d9:dd:c25:c25:c001:4055
442c19:dd:d9:dd:c25:c25:c001:4056/1272c19:dd:d9:dd:c25:c25:c001:4057
452c19:dd:d9:dd:c25:c25:c001:4058/1272c19:dd:d9:dd:c25:c25:c001:4059
462c19:dd:d9:dd:c25:c25:c001:405a/1272c19:dd:d9:dd:c25:c25:c001:405b
472c19:dd:d9:dd:c25:c25:c001:405c/1272c19:dd:d9:dd:c25:c25:c001:405d
482c19:dd:d9:dd:c25:c25:c001:405e/1272c19:dd:d9:dd:c25:c25:c001:405f
492c19:dd:d9:dd:c25:c25:c001:4060/1272c19:dd:d9:dd:c25:c25:c001:4061
502c19:dd:d9:dd:c25:c25:c001:4062/1272c19:dd:d9:dd:c25:c25:c001:4063
512c19:dd:d9:dd:c25:c25:c001:4064/1272c19:dd:d9:dd:c25:c25:c001:4065
522c19:dd:d9:dd:c25:c25:c001:4066/1272c19:dd:d9:dd:c25:c25:c001:4067
532c19:dd:d9:dd:c25:c25:c001:4068/1272c19:dd:d9:dd:c25:c25:c001:4069
542c19:dd:d9:dd:c25:c25:c001:406a/1272c19:dd:d9:dd:c25:c25:c001:406b
552c19:dd:d9:dd:c25:c25:c001:406c/1272c19:dd:d9:dd:c25:c25:c001:406d
562c19:dd:d9:dd:c25:c25:c001:406e/1272c19:dd:d9:dd:c25:c25:c001:406f
572c19:dd:d9:dd:c25:c25:c001:4070/1272c19:dd:d9:dd:c25:c25:c001:4071
582c19:dd:d9:dd:c25:c25:c001:4072/1272c19:dd:d9:dd:c25:c25:c001:4073
592c19:dd:d9:dd:c25:c25:c001:4074/1272c19:dd:d9:dd:c25:c25:c001:4075
602c19:dd:d9:dd:c25:c25:c001:4076/1272c19:dd:d9:dd:c25:c25:c001:4077
612c19:dd:d9:dd:c25:c25:c001:4078/1272c19:dd:d9:dd:c25:c25:c001:4079
622c19:dd:d9:dd:c25:c25:c001:407a/1272c19:dd:d9:dd:c25:c25:c001:407b
632c19:dd:d9:dd:c25:c25:c001:407c/1272c19:dd:d9:dd:c25:c25:c001:407d
642c19:dd:d9:dd:c25:c25:c001:407e/1272c19:dd:d9:dd:c25:c25:c001:407f
652c19:dd:d9:dd:c25:c25:c001:4080/1272c19:dd:d9:dd:c25:c25:c001:4081
662c19:dd:d9:dd:c25:c25:c001:4082/1272c19:dd:d9:dd:c25:c25:c001:4083
672c19:dd:d9:dd:c25:c25:c001:4084/1272c19:dd:d9:dd:c25:c25:c001:4085
682c19:dd:d9:dd:c25:c25:c001:4086/1272c19:dd:d9:dd:c25:c25:c001:4087
692c19:dd:d9:dd:c25:c25:c001:4088/1272c19:dd:d9:dd:c25:c25:c001:4089
702c19:dd:d9:dd:c25:c25:c001:408a/1272c19:dd:d9:dd:c25:c25:c001:408b
712c19:dd:d9:dd:c25:c25:c001:408c/1272c19:dd:d9:dd:c25:c25:c001:408d
722c19:dd:d9:dd:c25:c25:c001:408e/1272c19:dd:d9:dd:c25:c25:c001:408f
732c19:dd:d9:dd:c25:c25:c001:4090/1272c19:dd:d9:dd:c25:c25:c001:4091
742c19:dd:d9:dd:c25:c25:c001:4092/1272c19:dd:d9:dd:c25:c25:c001:4093
752c19:dd:d9:dd:c25:c25:c001:4094/1272c19:dd:d9:dd:c25:c25:c001:4095
762c19:dd:d9:dd:c25:c25:c001:4096/1272c19:dd:d9:dd:c25:c25:c001:4097
772c19:dd:d9:dd:c25:c25:c001:4098/1272c19:dd:d9:dd:c25:c25:c001:4099
782c19:dd:d9:dd:c25:c25:c001:409a/1272c19:dd:d9:dd:c25:c25:c001:409b
792c19:dd:d9:dd:c25:c25:c001:409c/1272c19:dd:d9:dd:c25:c25:c001:409d
802c19:dd:d9:dd:c25:c25:c001:409e/1272c19:dd:d9:dd:c25:c25:c001:409f
812c19:dd:d9:dd:c25:c25:c001:40a0/1272c19:dd:d9:dd:c25:c25:c001:40a1
822c19:dd:d9:dd:c25:c25:c001:40a2/1272c19:dd:d9:dd:c25:c25:c001:40a3
832c19:dd:d9:dd:c25:c25:c001:40a4/1272c19:dd:d9:dd:c25:c25:c001:40a5
842c19:dd:d9:dd:c25:c25:c001:40a6/1272c19:dd:d9:dd:c25:c25:c001:40a7
852c19:dd:d9:dd:c25:c25:c001:40a8/1272c19:dd:d9:dd:c25:c25:c001:40a9
862c19:dd:d9:dd:c25:c25:c001:40aa/1272c19:dd:d9:dd:c25:c25:c001:40ab
872c19:dd:d9:dd:c25:c25:c001:40ac/1272c19:dd:d9:dd:c25:c25:c001:40ad
882c19:dd:d9:dd:c25:c25:c001:40ae/1272c19:dd:d9:dd:c25:c25:c001:40af
892c19:dd:d9:dd:c25:c25:c001:40b0/1272c19:dd:d9:dd:c25:c25:c001:40b1
902c19:dd:d9:dd:c25:c25:c001:40b2/1272c19:dd:d9:dd:c25:c25:c001:40b3
912c19:dd:d9:dd:c25:c25:c001:40b4/1272c19:dd:d9:dd:c25:c25:c001:40b5
922c19:dd:d9:dd:c25:c25:c001:40b6/1272c19:dd:d9:dd:c25:c25:c001:40b7
932c19:dd:d9:dd:c25:c25:c001:40b8/1272c19:dd:d9:dd:c25:c25:c001:40b9
942c19:dd:d9:dd:c25:c25:c001:40ba/1272c19:dd:d9:dd:c25:c25:c001:40bb
952c19:dd:d9:dd:c25:c25:c001:40bc/1272c19:dd:d9:dd:c25:c25:c001:40bd
962c19:dd:d9:dd:c25:c25:c001:40be/1272c19:dd:d9:dd:c25:c25:c001:40bf
972c19:dd:d9:dd:c25:c25:c001:40c0/1272c19:dd:d9:dd:c25:c25:c001:40c1
982c19:dd:d9:dd:c25:c25:c001:40c2/1272c19:dd:d9:dd:c25:c25:c001:40c3
992c19:dd:d9:dd:c25:c25:c001:40c4/1272c19:dd:d9:dd:c25:c25:c001:40c5
1002c19:dd:d9:dd:c25:c25:c001:40c6/1272c19:dd:d9:dd:c25:c25:c001:40c7
1012c19:dd:d9:dd:c25:c25:c001:40c8/1272c19:dd:d9:dd:c25:c25:c001:40c9
1022c19:dd:d9:dd:c25:c25:c001:40ca/1272c19:dd:d9:dd:c25:c25:c001:40cb
1032c19:dd:d9:dd:c25:c25:c001:40cc/1272c19:dd:d9:dd:c25:c25:c001:40cd
1042c19:dd:d9:dd:c25:c25:c001:40ce/1272c19:dd:d9:dd:c25:c25:c001:40cf
1052c19:dd:d9:dd:c25:c25:c001:40d0/1272c19:dd:d9:dd:c25:c25:c001:40d1
1062c19:dd:d9:dd:c25:c25:c001:40d2/1272c19:dd:d9:dd:c25:c25:c001:40d3
1072c19:dd:d9:dd:c25:c25:c001:40d4/1272c19:dd:d9:dd:c25:c25:c001:40d5
1082c19:dd:d9:dd:c25:c25:c001:40d6/1272c19:dd:d9:dd:c25:c25:c001:40d7
1092c19:dd:d9:dd:c25:c25:c001:40d8/1272c19:dd:d9:dd:c25:c25:c001:40d9
1102c19:dd:d9:dd:c25:c25:c001:40da/1272c19:dd:d9:dd:c25:c25:c001:40db
1112c19:dd:d9:dd:c25:c25:c001:40dc/1272c19:dd:d9:dd:c25:c25:c001:40dd
1122c19:dd:d9:dd:c25:c25:c001:40de/1272c19:dd:d9:dd:c25:c25:c001:40df
1132c19:dd:d9:dd:c25:c25:c001:40e0/1272c19:dd:d9:dd:c25:c25:c001:40e1
1142c19:dd:d9:dd:c25:c25:c001:40e2/1272c19:dd:d9:dd:c25:c25:c001:40e3
1152c19:dd:d9:dd:c25:c25:c001:40e4/1272c19:dd:d9:dd:c25:c25:c001:40e5
1162c19:dd:d9:dd:c25:c25:c001:40e6/1272c19:dd:d9:dd:c25:c25:c001:40e7
1172c19:dd:d9:dd:c25:c25:c001:40e8/1272c19:dd:d9:dd:c25:c25:c001:40e9
1182c19:dd:d9:dd:c25:c25:c001:40ea/1272c19:dd:d9:dd:c25:c25:c001:40eb
1192c19:dd:d9:dd:c25:c25:c001:40ec/1272c19:dd:d9:dd:c25:c25:c001:40ed
1202c19:dd:d9:dd:c25:c25:c001:40ee/1272c19:dd:d9:dd:c25:c25:c001:40ef
1212c19:dd:d9:dd:c25:c25:c001:40f0/1272c19:dd:d9:dd:c25:c25:c001:40f1
1222c19:dd:d9:dd:c25:c25:c001:40f2/1272c19:dd:d9:dd:c25:c25:c001:40f3
1232c19:dd:d9:dd:c25:c25:c001:40f4/1272c19:dd:d9:dd:c25:c25:c001:40f5
1242c19:dd:d9:dd:c25:c25:c001:40f6/1272c19:dd:d9:dd:c25:c25:c001:40f7
1252c19:dd:d9:dd:c25:c25:c001:40f8/1272c19:dd:d9:dd:c25:c25:c001:40f9
1262c19:dd:d9:dd:c25:c25:c001:40fa/1272c19:dd:d9:dd:c25:c25:c001:40fb
1272c19:dd:d9:dd:c25:c25:c001:40fc/1272c19:dd:d9:dd:c25:c25:c001:40fd
1282c19:dd:d9:dd:c25:c25:c001:40fe/1272c19:dd:d9:dd:c25:c25:c001:40ff
1292c19:dd:d9:dd:c25:c25:c001:4100/1272c19:dd:d9:dd:c25:c25:c001:4101
1302c19:dd:d9:dd:c25:c25:c001:4102/1272c19:dd:d9:dd:c25:c25:c001:4103
1312c19:dd:d9:dd:c25:c25:c001:4104/1272c19:dd:d9:dd:c25:c25:c001:4105
1322c19:dd:d9:dd:c25:c25:c001:4106/1272c19:dd:d9:dd:c25:c25:c001:4107
1332c19:dd:d9:dd:c25:c25:c001:4108/1272c19:dd:d9:dd:c25:c25:c001:4109
1342c19:dd:d9:dd:c25:c25:c001:410a/1272c19:dd:d9:dd:c25:c25:c001:410b
1352c19:dd:d9:dd:c25:c25:c001:410c/1272c19:dd:d9:dd:c25:c25:c001:410d
1362c19:dd:d9:dd:c25:c25:c001:410e/1272c19:dd:d9:dd:c25:c25:c001:410f
1372c19:dd:d9:dd:c25:c25:c001:4110/1272c19:dd:d9:dd:c25:c25:c001:4111
1382c19:dd:d9:dd:c25:c25:c001:4112/1272c19:dd:d9:dd:c25:c25:c001:4113
1392c19:dd:d9:dd:c25:c25:c001:4114/1272c19:dd:d9:dd:c25:c25:c001:4115
1402c19:dd:d9:dd:c25:c25:c001:4116/1272c19:dd:d9:dd:c25:c25:c001:4117
1412c19:dd:d9:dd:c25:c25:c001:4118/1272c19:dd:d9:dd:c25:c25:c001:4119
1422c19:dd:d9:dd:c25:c25:c001:411a/1272c19:dd:d9:dd:c25:c25:c001:411b
1432c19:dd:d9:dd:c25:c25:c001:411c/1272c19:dd:d9:dd:c25:c25:c001:411d
1442c19:dd:d9:dd:c25:c25:c001:411e/1272c19:dd:d9:dd:c25:c25:c001:411f
1452c19:dd:d9:dd:c25:c25:c001:4120/1272c19:dd:d9:dd:c25:c25:c001:4121
1462c19:dd:d9:dd:c25:c25:c001:4122/1272c19:dd:d9:dd:c25:c25:c001:4123
1472c19:dd:d9:dd:c25:c25:c001:4124/1272c19:dd:d9:dd:c25:c25:c001:4125
1482c19:dd:d9:dd:c25:c25:c001:4126/1272c19:dd:d9:dd:c25:c25:c001:4127
1492c19:dd:d9:dd:c25:c25:c001:4128/1272c19:dd:d9:dd:c25:c25:c001:4129
1502c19:dd:d9:dd:c25:c25:c001:412a/1272c19:dd:d9:dd:c25:c25:c001:412b
1512c19:dd:d9:dd:c25:c25:c001:412c/1272c19:dd:d9:dd:c25:c25:c001:412d
1522c19:dd:d9:dd:c25:c25:c001:412e/1272c19:dd:d9:dd:c25:c25:c001:412f
1532c19:dd:d9:dd:c25:c25:c001:4130/1272c19:dd:d9:dd:c25:c25:c001:4131
1542c19:dd:d9:dd:c25:c25:c001:4132/1272c19:dd:d9:dd:c25:c25:c001:4133
1552c19:dd:d9:dd:c25:c25:c001:4134/1272c19:dd:d9:dd:c25:c25:c001:4135
1562c19:dd:d9:dd:c25:c25:c001:4136/1272c19:dd:d9:dd:c25:c25:c001:4137
1572c19:dd:d9:dd:c25:c25:c001:4138/1272c19:dd:d9:dd:c25:c25:c001:4139
1582c19:dd:d9:dd:c25:c25:c001:413a/1272c19:dd:d9:dd:c25:c25:c001:413b
1592c19:dd:d9:dd:c25:c25:c001:413c/1272c19:dd:d9:dd:c25:c25:c001:413d
1602c19:dd:d9:dd:c25:c25:c001:413e/1272c19:dd:d9:dd:c25:c25:c001:413f
1612c19:dd:d9:dd:c25:c25:c001:4140/1272c19:dd:d9:dd:c25:c25:c001:4141
1622c19:dd:d9:dd:c25:c25:c001:4142/1272c19:dd:d9:dd:c25:c25:c001:4143
1632c19:dd:d9:dd:c25:c25:c001:4144/1272c19:dd:d9:dd:c25:c25:c001:4145
1642c19:dd:d9:dd:c25:c25:c001:4146/1272c19:dd:d9:dd:c25:c25:c001:4147
1652c19:dd:d9:dd:c25:c25:c001:4148/1272c19:dd:d9:dd:c25:c25:c001:4149
1662c19:dd:d9:dd:c25:c25:c001:414a/1272c19:dd:d9:dd:c25:c25:c001:414b
1672c19:dd:d9:dd:c25:c25:c001:414c/1272c19:dd:d9:dd:c25:c25:c001:414d
1682c19:dd:d9:dd:c25:c25:c001:414e/1272c19:dd:d9:dd:c25:c25:c001:414f
1692c19:dd:d9:dd:c25:c25:c001:4150/1272c19:dd:d9:dd:c25:c25:c001:4151
1702c19:dd:d9:dd:c25:c25:c001:4152/1272c19:dd:d9:dd:c25:c25:c001:4153
1712c19:dd:d9:dd:c25:c25:c001:4154/1272c19:dd:d9:dd:c25:c25:c001:4155
1722c19:dd:d9:dd:c25:c25:c001:4156/1272c19:dd:d9:dd:c25:c25:c001:4157
1732c19:dd:d9:dd:c25:c25:c001:4158/1272c19:dd:d9:dd:c25:c25:c001:4159
1742c19:dd:d9:dd:c25:c25:c001:415a/1272c19:dd:d9:dd:c25:c25:c001:415b
1752c19:dd:d9:dd:c25:c25:c001:415c/1272c19:dd:d9:dd:c25:c25:c001:415d
1762c19:dd:d9:dd:c25:c25:c001:415e/1272c19:dd:d9:dd:c25:c25:c001:415f
1772c19:dd:d9:dd:c25:c25:c001:4160/1272c19:dd:d9:dd:c25:c25:c001:4161
1782c19:dd:d9:dd:c25:c25:c001:4162/1272c19:dd:d9:dd:c25:c25:c001:4163
1792c19:dd:d9:dd:c25:c25:c001:4164/1272c19:dd:d9:dd:c25:c25:c001:4165
1802c19:dd:d9:dd:c25:c25:c001:4166/1272c19:dd:d9:dd:c25:c25:c001:4167
1812c19:dd:d9:dd:c25:c25:c001:4168/1272c19:dd:d9:dd:c25:c25:c001:4169
1822c19:dd:d9:dd:c25:c25:c001:416a/1272c19:dd:d9:dd:c25:c25:c001:416b
1832c19:dd:d9:dd:c25:c25:c001:416c/1272c19:dd:d9:dd:c25:c25:c001:416d
1842c19:dd:d9:dd:c25:c25:c001:416e/1272c19:dd:d9:dd:c25:c25:c001:416f
1852c19:dd:d9:dd:c25:c25:c001:4170/1272c19:dd:d9:dd:c25:c25:c001:4171
1862c19:dd:d9:dd:c25:c25:c001:4172/1272c19:dd:d9:dd:c25:c25:c001:4173
1872c19:dd:d9:dd:c25:c25:c001:4174/1272c19:dd:d9:dd:c25:c25:c001:4175
1882c19:dd:d9:dd:c25:c25:c001:4176/1272c19:dd:d9:dd:c25:c25:c001:4177
1892c19:dd:d9:dd:c25:c25:c001:4178/1272c19:dd:d9:dd:c25:c25:c001:4179
1902c19:dd:d9:dd:c25:c25:c001:417a/1272c19:dd:d9:dd:c25:c25:c001:417b
1912c19:dd:d9:dd:c25:c25:c001:417c/1272c19:dd:d9:dd:c25:c25:c001:417d
1922c19:dd:d9:dd:c25:c25:c001:417e/1272c19:dd:d9:dd:c25:c25:c001:417f
1932c19:dd:d9:dd:c25:c25:c001:4180/1272c19:dd:d9:dd:c25:c25:c001:4181
1942c19:dd:d9:dd:c25:c25:c001:4182/1272c19:dd:d9:dd:c25:c25:c001:4183
1952c19:dd:d9:dd:c25:c25:c001:4184/1272c19:dd:d9:dd:c25:c25:c001:4185
1962c19:dd:d9:dd:c25:c25:c001:4186/1272c19:dd:d9:dd:c25:c25:c001:4187
1972c19:dd:d9:dd:c25:c25:c001:4188/1272c19:dd:d9:dd:c25:c25:c001:4189
1982c19:dd:d9:dd:c25:c25:c001:418a/1272c19:dd:d9:dd:c25:c25:c001:418b
1992c19:dd:d9:dd:c25:c25:c001:418c/1272c19:dd:d9:dd:c25:c25:c001:418d
2002c19:dd:d9:dd:c25:c25:c001:418e/1272c19:dd:d9:dd:c25:c25:c001:418f
2012c19:dd:d9:dd:c25:c25:c001:4190/1272c19:dd:d9:dd:c25:c25:c001:4191
2022c19:dd:d9:dd:c25:c25:c001:4192/1272c19:dd:d9:dd:c25:c25:c001:4193
2032c19:dd:d9:dd:c25:c25:c001:4194/1272c19:dd:d9:dd:c25:c25:c001:4195
2042c19:dd:d9:dd:c25:c25:c001:4196/1272c19:dd:d9:dd:c25:c25:c001:4197
2052c19:dd:d9:dd:c25:c25:c001:4198/1272c19:dd:d9:dd:c25:c25:c001:4199
2062c19:dd:d9:dd:c25:c25:c001:419a/1272c19:dd:d9:dd:c25:c25:c001:419b
2072c19:dd:d9:dd:c25:c25:c001:419c/1272c19:dd:d9:dd:c25:c25:c001:419d
2082c19:dd:d9:dd:c25:c25:c001:419e/1272c19:dd:d9:dd:c25:c25:c001:419f
2092c19:dd:d9:dd:c25:c25:c001:41a0/1272c19:dd:d9:dd:c25:c25:c001:41a1
2102c19:dd:d9:dd:c25:c25:c001:41a2/1272c19:dd:d9:dd:c25:c25:c001:41a3
2112c19:dd:d9:dd:c25:c25:c001:41a4/1272c19:dd:d9:dd:c25:c25:c001:41a5
2122c19:dd:d9:dd:c25:c25:c001:41a6/1272c19:dd:d9:dd:c25:c25:c001:41a7
2132c19:dd:d9:dd:c25:c25:c001:41a8/1272c19:dd:d9:dd:c25:c25:c001:41a9
2142c19:dd:d9:dd:c25:c25:c001:41aa/1272c19:dd:d9:dd:c25:c25:c001:41ab
2152c19:dd:d9:dd:c25:c25:c001:41ac/1272c19:dd:d9:dd:c25:c25:c001:41ad
2162c19:dd:d9:dd:c25:c25:c001:41ae/1272c19:dd:d9:dd:c25:c25:c001:41af
2172c19:dd:d9:dd:c25:c25:c001:41b0/1272c19:dd:d9:dd:c25:c25:c001:41b1
2182c19:dd:d9:dd:c25:c25:c001:41b2/1272c19:dd:d9:dd:c25:c25:c001:41b3
2192c19:dd:d9:dd:c25:c25:c001:41b4/1272c19:dd:d9:dd:c25:c25:c001:41b5
2202c19:dd:d9:dd:c25:c25:c001:41b6/1272c19:dd:d9:dd:c25:c25:c001:41b7
2212c19:dd:d9:dd:c25:c25:c001:41b8/1272c19:dd:d9:dd:c25:c25:c001:41b9
2222c19:dd:d9:dd:c25:c25:c001:41ba/1272c19:dd:d9:dd:c25:c25:c001:41bb
2232c19:dd:d9:dd:c25:c25:c001:41bc/1272c19:dd:d9:dd:c25:c25:c001:41bd
2242c19:dd:d9:dd:c25:c25:c001:41be/1272c19:dd:d9:dd:c25:c25:c001:41bf
2252c19:dd:d9:dd:c25:c25:c001:41c0/1272c19:dd:d9:dd:c25:c25:c001:41c1
2262c19:dd:d9:dd:c25:c25:c001:41c2/1272c19:dd:d9:dd:c25:c25:c001:41c3
2272c19:dd:d9:dd:c25:c25:c001:41c4/1272c19:dd:d9:dd:c25:c25:c001:41c5
2282c19:dd:d9:dd:c25:c25:c001:41c6/1272c19:dd:d9:dd:c25:c25:c001:41c7
2292c19:dd:d9:dd:c25:c25:c001:41c8/1272c19:dd:d9:dd:c25:c25:c001:41c9
2302c19:dd:d9:dd:c25:c25:c001:41ca/1272c19:dd:d9:dd:c25:c25:c001:41cb
2312c19:dd:d9:dd:c25:c25:c001:41cc/1272c19:dd:d9:dd:c25:c25:c001:41cd
2322c19:dd:d9:dd:c25:c25:c001:41ce/1272c19:dd:d9:dd:c25:c25:c001:41cf
2332c19:dd:d9:dd:c25:c25:c001:41d0/1272c19:dd:d9:dd:c25:c25:c001:41d1
2342c19:dd:d9:dd:c25:c25:c001:41d2/1272c19:dd:d9:dd:c25:c25:c001:41d3
2352c19:dd:d9:dd:c25:c25:c001:41d4/1272c19:dd:d9:dd:c25:c25:c001:41d5
2362c19:dd:d9:dd:c25:c25:c001:41d6/1272c19:dd:d9:dd:c25:c25:c001:41d7
2372c19:dd:d9:dd:c25:c25:c001:41d8/1272c19:dd:d9:dd:c25:c25:c001:41d9
2382c19:dd:d9:dd:c25:c25:c001:41da/1272c19:dd:d9:dd:c25:c25:c001:41db
2392c19:dd:d9:dd:c25:c25:c001:41dc/1272c19:dd:d9:dd:c25:c25:c001:41dd
2402c19:dd:d9:dd:c25:c25:c001:41de/1272c19:dd:d9:dd:c25:c25:c001:41df
2412c19:dd:d9:dd:c25:c25:c001:41e0/1272c19:dd:d9:dd:c25:c25:c001:41e1
2422c19:dd:d9:dd:c25:c25:c001:41e2/1272c19:dd:d9:dd:c25:c25:c001:41e3
2432c19:dd:d9:dd:c25:c25:c001:41e4/1272c19:dd:d9:dd:c25:c25:c001:41e5
2442c19:dd:d9:dd:c25:c25:c001:41e6/1272c19:dd:d9:dd:c25:c25:c001:41e7
2452c19:dd:d9:dd:c25:c25:c001:41e8/1272c19:dd:d9:dd:c25:c25:c001:41e9
2462c19:dd:d9:dd:c25:c25:c001:41ea/1272c19:dd:d9:dd:c25:c25:c001:41eb
2472c19:dd:d9:dd:c25:c25:c001:41ec/1272c19:dd:d9:dd:c25:c25:c001:41ed
2482c19:dd:d9:dd:c25:c25:c001:41ee/1272c19:dd:d9:dd:c25:c25:c001:41ef
2492c19:dd:d9:dd:c25:c25:c001:41f0/1272c19:dd:d9:dd:c25:c25:c001:41f1
2502c19:dd:d9:dd:c25:c25:c001:41f2/1272c19:dd:d9:dd:c25:c25:c001:41f3
2512c19:dd:d9:dd:c25:c25:c001:41f4/1272c19:dd:d9:dd:c25:c25:c001:41f5
2522c19:dd:d9:dd:c25:c25:c001:41f6/1272c19:dd:d9:dd:c25:c25:c001:41f7
2532c19:dd:d9:dd:c25:c25:c001:41f8/1272c19:dd:d9:dd:c25:c25:c001:41f9
2542c19:dd:d9:dd:c25:c25:c001:41fa/1272c19:dd:d9:dd:c25:c25:c001:41fb
2552c19:dd:d9:dd:c25:c25:c001:41fc/1272c19:dd:d9:dd:c25:c25:c001:41fd
2562c19:dd:d9:dd:c25:c25:c001:41fe/1272c19:dd:d9:dd:c25:c25:c001:41ff

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.