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/120
Addresses256
/64 networksPart of one
Network
2c19:dd:c25:c25d:dd:dd:dd:3900/120
First address
2c19:dd:c25:c25d:dd:dd:dd:3900
Last address
2c19:dd:c25:c25d:dd:dd:dd:39ff
Addresses
256
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
2c19:00dd:0c25:c25d:00dd:00dd:00dd:3900
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zone
9.3.d.d.0.0.d.d.0.0.d.d.0.0.d.5.2.c.5.2.c.0.d.d.0.0.9.1.c.2.ip6.arpa
Split into smaller subnets/128
/121 (2)/122 (4)/123 (8)/124 (16)/127 (128)/128 (256)

2c19:dd:c25:c25d:dd:dd:dd:3900/120 makes 256 subnets of /128.

Subnets
#SubnetLast address
12c19:dd:c25:c25d:dd:dd:dd:3900/1282c19:dd:c25:c25d:dd:dd:dd:3900
22c19:dd:c25:c25d:dd:dd:dd:3901/1282c19:dd:c25:c25d:dd:dd:dd:3901
32c19:dd:c25:c25d:dd:dd:dd:3902/1282c19:dd:c25:c25d:dd:dd:dd:3902
42c19:dd:c25:c25d:dd:dd:dd:3903/1282c19:dd:c25:c25d:dd:dd:dd:3903
52c19:dd:c25:c25d:dd:dd:dd:3904/1282c19:dd:c25:c25d:dd:dd:dd:3904
62c19:dd:c25:c25d:dd:dd:dd:3905/1282c19:dd:c25:c25d:dd:dd:dd:3905
72c19:dd:c25:c25d:dd:dd:dd:3906/1282c19:dd:c25:c25d:dd:dd:dd:3906
82c19:dd:c25:c25d:dd:dd:dd:3907/1282c19:dd:c25:c25d:dd:dd:dd:3907
92c19:dd:c25:c25d:dd:dd:dd:3908/1282c19:dd:c25:c25d:dd:dd:dd:3908
102c19:dd:c25:c25d:dd:dd:dd:3909/1282c19:dd:c25:c25d:dd:dd:dd:3909
112c19:dd:c25:c25d:dd:dd:dd:390a/1282c19:dd:c25:c25d:dd:dd:dd:390a
122c19:dd:c25:c25d:dd:dd:dd:390b/1282c19:dd:c25:c25d:dd:dd:dd:390b
132c19:dd:c25:c25d:dd:dd:dd:390c/1282c19:dd:c25:c25d:dd:dd:dd:390c
142c19:dd:c25:c25d:dd:dd:dd:390d/1282c19:dd:c25:c25d:dd:dd:dd:390d
152c19:dd:c25:c25d:dd:dd:dd:390e/1282c19:dd:c25:c25d:dd:dd:dd:390e
162c19:dd:c25:c25d:dd:dd:dd:390f/1282c19:dd:c25:c25d:dd:dd:dd:390f
172c19:dd:c25:c25d:dd:dd:dd:3910/1282c19:dd:c25:c25d:dd:dd:dd:3910
182c19:dd:c25:c25d:dd:dd:dd:3911/1282c19:dd:c25:c25d:dd:dd:dd:3911
192c19:dd:c25:c25d:dd:dd:dd:3912/1282c19:dd:c25:c25d:dd:dd:dd:3912
202c19:dd:c25:c25d:dd:dd:dd:3913/1282c19:dd:c25:c25d:dd:dd:dd:3913
212c19:dd:c25:c25d:dd:dd:dd:3914/1282c19:dd:c25:c25d:dd:dd:dd:3914
222c19:dd:c25:c25d:dd:dd:dd:3915/1282c19:dd:c25:c25d:dd:dd:dd:3915
232c19:dd:c25:c25d:dd:dd:dd:3916/1282c19:dd:c25:c25d:dd:dd:dd:3916
242c19:dd:c25:c25d:dd:dd:dd:3917/1282c19:dd:c25:c25d:dd:dd:dd:3917
252c19:dd:c25:c25d:dd:dd:dd:3918/1282c19:dd:c25:c25d:dd:dd:dd:3918
262c19:dd:c25:c25d:dd:dd:dd:3919/1282c19:dd:c25:c25d:dd:dd:dd:3919
272c19:dd:c25:c25d:dd:dd:dd:391a/1282c19:dd:c25:c25d:dd:dd:dd:391a
282c19:dd:c25:c25d:dd:dd:dd:391b/1282c19:dd:c25:c25d:dd:dd:dd:391b
292c19:dd:c25:c25d:dd:dd:dd:391c/1282c19:dd:c25:c25d:dd:dd:dd:391c
302c19:dd:c25:c25d:dd:dd:dd:391d/1282c19:dd:c25:c25d:dd:dd:dd:391d
312c19:dd:c25:c25d:dd:dd:dd:391e/1282c19:dd:c25:c25d:dd:dd:dd:391e
322c19:dd:c25:c25d:dd:dd:dd:391f/1282c19:dd:c25:c25d:dd:dd:dd:391f
332c19:dd:c25:c25d:dd:dd:dd:3920/1282c19:dd:c25:c25d:dd:dd:dd:3920
342c19:dd:c25:c25d:dd:dd:dd:3921/1282c19:dd:c25:c25d:dd:dd:dd:3921
352c19:dd:c25:c25d:dd:dd:dd:3922/1282c19:dd:c25:c25d:dd:dd:dd:3922
362c19:dd:c25:c25d:dd:dd:dd:3923/1282c19:dd:c25:c25d:dd:dd:dd:3923
372c19:dd:c25:c25d:dd:dd:dd:3924/1282c19:dd:c25:c25d:dd:dd:dd:3924
382c19:dd:c25:c25d:dd:dd:dd:3925/1282c19:dd:c25:c25d:dd:dd:dd:3925
392c19:dd:c25:c25d:dd:dd:dd:3926/1282c19:dd:c25:c25d:dd:dd:dd:3926
402c19:dd:c25:c25d:dd:dd:dd:3927/1282c19:dd:c25:c25d:dd:dd:dd:3927
412c19:dd:c25:c25d:dd:dd:dd:3928/1282c19:dd:c25:c25d:dd:dd:dd:3928
422c19:dd:c25:c25d:dd:dd:dd:3929/1282c19:dd:c25:c25d:dd:dd:dd:3929
432c19:dd:c25:c25d:dd:dd:dd:392a/1282c19:dd:c25:c25d:dd:dd:dd:392a
442c19:dd:c25:c25d:dd:dd:dd:392b/1282c19:dd:c25:c25d:dd:dd:dd:392b
452c19:dd:c25:c25d:dd:dd:dd:392c/1282c19:dd:c25:c25d:dd:dd:dd:392c
462c19:dd:c25:c25d:dd:dd:dd:392d/1282c19:dd:c25:c25d:dd:dd:dd:392d
472c19:dd:c25:c25d:dd:dd:dd:392e/1282c19:dd:c25:c25d:dd:dd:dd:392e
482c19:dd:c25:c25d:dd:dd:dd:392f/1282c19:dd:c25:c25d:dd:dd:dd:392f
492c19:dd:c25:c25d:dd:dd:dd:3930/1282c19:dd:c25:c25d:dd:dd:dd:3930
502c19:dd:c25:c25d:dd:dd:dd:3931/1282c19:dd:c25:c25d:dd:dd:dd:3931
512c19:dd:c25:c25d:dd:dd:dd:3932/1282c19:dd:c25:c25d:dd:dd:dd:3932
522c19:dd:c25:c25d:dd:dd:dd:3933/1282c19:dd:c25:c25d:dd:dd:dd:3933
532c19:dd:c25:c25d:dd:dd:dd:3934/1282c19:dd:c25:c25d:dd:dd:dd:3934
542c19:dd:c25:c25d:dd:dd:dd:3935/1282c19:dd:c25:c25d:dd:dd:dd:3935
552c19:dd:c25:c25d:dd:dd:dd:3936/1282c19:dd:c25:c25d:dd:dd:dd:3936
562c19:dd:c25:c25d:dd:dd:dd:3937/1282c19:dd:c25:c25d:dd:dd:dd:3937
572c19:dd:c25:c25d:dd:dd:dd:3938/1282c19:dd:c25:c25d:dd:dd:dd:3938
582c19:dd:c25:c25d:dd:dd:dd:3939/1282c19:dd:c25:c25d:dd:dd:dd:3939
592c19:dd:c25:c25d:dd:dd:dd:393a/1282c19:dd:c25:c25d:dd:dd:dd:393a
602c19:dd:c25:c25d:dd:dd:dd:393b/1282c19:dd:c25:c25d:dd:dd:dd:393b
612c19:dd:c25:c25d:dd:dd:dd:393c/1282c19:dd:c25:c25d:dd:dd:dd:393c
622c19:dd:c25:c25d:dd:dd:dd:393d/1282c19:dd:c25:c25d:dd:dd:dd:393d
632c19:dd:c25:c25d:dd:dd:dd:393e/1282c19:dd:c25:c25d:dd:dd:dd:393e
642c19:dd:c25:c25d:dd:dd:dd:393f/1282c19:dd:c25:c25d:dd:dd:dd:393f
652c19:dd:c25:c25d:dd:dd:dd:3940/1282c19:dd:c25:c25d:dd:dd:dd:3940
662c19:dd:c25:c25d:dd:dd:dd:3941/1282c19:dd:c25:c25d:dd:dd:dd:3941
672c19:dd:c25:c25d:dd:dd:dd:3942/1282c19:dd:c25:c25d:dd:dd:dd:3942
682c19:dd:c25:c25d:dd:dd:dd:3943/1282c19:dd:c25:c25d:dd:dd:dd:3943
692c19:dd:c25:c25d:dd:dd:dd:3944/1282c19:dd:c25:c25d:dd:dd:dd:3944
702c19:dd:c25:c25d:dd:dd:dd:3945/1282c19:dd:c25:c25d:dd:dd:dd:3945
712c19:dd:c25:c25d:dd:dd:dd:3946/1282c19:dd:c25:c25d:dd:dd:dd:3946
722c19:dd:c25:c25d:dd:dd:dd:3947/1282c19:dd:c25:c25d:dd:dd:dd:3947
732c19:dd:c25:c25d:dd:dd:dd:3948/1282c19:dd:c25:c25d:dd:dd:dd:3948
742c19:dd:c25:c25d:dd:dd:dd:3949/1282c19:dd:c25:c25d:dd:dd:dd:3949
752c19:dd:c25:c25d:dd:dd:dd:394a/1282c19:dd:c25:c25d:dd:dd:dd:394a
762c19:dd:c25:c25d:dd:dd:dd:394b/1282c19:dd:c25:c25d:dd:dd:dd:394b
772c19:dd:c25:c25d:dd:dd:dd:394c/1282c19:dd:c25:c25d:dd:dd:dd:394c
782c19:dd:c25:c25d:dd:dd:dd:394d/1282c19:dd:c25:c25d:dd:dd:dd:394d
792c19:dd:c25:c25d:dd:dd:dd:394e/1282c19:dd:c25:c25d:dd:dd:dd:394e
802c19:dd:c25:c25d:dd:dd:dd:394f/1282c19:dd:c25:c25d:dd:dd:dd:394f
812c19:dd:c25:c25d:dd:dd:dd:3950/1282c19:dd:c25:c25d:dd:dd:dd:3950
822c19:dd:c25:c25d:dd:dd:dd:3951/1282c19:dd:c25:c25d:dd:dd:dd:3951
832c19:dd:c25:c25d:dd:dd:dd:3952/1282c19:dd:c25:c25d:dd:dd:dd:3952
842c19:dd:c25:c25d:dd:dd:dd:3953/1282c19:dd:c25:c25d:dd:dd:dd:3953
852c19:dd:c25:c25d:dd:dd:dd:3954/1282c19:dd:c25:c25d:dd:dd:dd:3954
862c19:dd:c25:c25d:dd:dd:dd:3955/1282c19:dd:c25:c25d:dd:dd:dd:3955
872c19:dd:c25:c25d:dd:dd:dd:3956/1282c19:dd:c25:c25d:dd:dd:dd:3956
882c19:dd:c25:c25d:dd:dd:dd:3957/1282c19:dd:c25:c25d:dd:dd:dd:3957
892c19:dd:c25:c25d:dd:dd:dd:3958/1282c19:dd:c25:c25d:dd:dd:dd:3958
902c19:dd:c25:c25d:dd:dd:dd:3959/1282c19:dd:c25:c25d:dd:dd:dd:3959
912c19:dd:c25:c25d:dd:dd:dd:395a/1282c19:dd:c25:c25d:dd:dd:dd:395a
922c19:dd:c25:c25d:dd:dd:dd:395b/1282c19:dd:c25:c25d:dd:dd:dd:395b
932c19:dd:c25:c25d:dd:dd:dd:395c/1282c19:dd:c25:c25d:dd:dd:dd:395c
942c19:dd:c25:c25d:dd:dd:dd:395d/1282c19:dd:c25:c25d:dd:dd:dd:395d
952c19:dd:c25:c25d:dd:dd:dd:395e/1282c19:dd:c25:c25d:dd:dd:dd:395e
962c19:dd:c25:c25d:dd:dd:dd:395f/1282c19:dd:c25:c25d:dd:dd:dd:395f
972c19:dd:c25:c25d:dd:dd:dd:3960/1282c19:dd:c25:c25d:dd:dd:dd:3960
982c19:dd:c25:c25d:dd:dd:dd:3961/1282c19:dd:c25:c25d:dd:dd:dd:3961
992c19:dd:c25:c25d:dd:dd:dd:3962/1282c19:dd:c25:c25d:dd:dd:dd:3962
1002c19:dd:c25:c25d:dd:dd:dd:3963/1282c19:dd:c25:c25d:dd:dd:dd:3963
1012c19:dd:c25:c25d:dd:dd:dd:3964/1282c19:dd:c25:c25d:dd:dd:dd:3964
1022c19:dd:c25:c25d:dd:dd:dd:3965/1282c19:dd:c25:c25d:dd:dd:dd:3965
1032c19:dd:c25:c25d:dd:dd:dd:3966/1282c19:dd:c25:c25d:dd:dd:dd:3966
1042c19:dd:c25:c25d:dd:dd:dd:3967/1282c19:dd:c25:c25d:dd:dd:dd:3967
1052c19:dd:c25:c25d:dd:dd:dd:3968/1282c19:dd:c25:c25d:dd:dd:dd:3968
1062c19:dd:c25:c25d:dd:dd:dd:3969/1282c19:dd:c25:c25d:dd:dd:dd:3969
1072c19:dd:c25:c25d:dd:dd:dd:396a/1282c19:dd:c25:c25d:dd:dd:dd:396a
1082c19:dd:c25:c25d:dd:dd:dd:396b/1282c19:dd:c25:c25d:dd:dd:dd:396b
1092c19:dd:c25:c25d:dd:dd:dd:396c/1282c19:dd:c25:c25d:dd:dd:dd:396c
1102c19:dd:c25:c25d:dd:dd:dd:396d/1282c19:dd:c25:c25d:dd:dd:dd:396d
1112c19:dd:c25:c25d:dd:dd:dd:396e/1282c19:dd:c25:c25d:dd:dd:dd:396e
1122c19:dd:c25:c25d:dd:dd:dd:396f/1282c19:dd:c25:c25d:dd:dd:dd:396f
1132c19:dd:c25:c25d:dd:dd:dd:3970/1282c19:dd:c25:c25d:dd:dd:dd:3970
1142c19:dd:c25:c25d:dd:dd:dd:3971/1282c19:dd:c25:c25d:dd:dd:dd:3971
1152c19:dd:c25:c25d:dd:dd:dd:3972/1282c19:dd:c25:c25d:dd:dd:dd:3972
1162c19:dd:c25:c25d:dd:dd:dd:3973/1282c19:dd:c25:c25d:dd:dd:dd:3973
1172c19:dd:c25:c25d:dd:dd:dd:3974/1282c19:dd:c25:c25d:dd:dd:dd:3974
1182c19:dd:c25:c25d:dd:dd:dd:3975/1282c19:dd:c25:c25d:dd:dd:dd:3975
1192c19:dd:c25:c25d:dd:dd:dd:3976/1282c19:dd:c25:c25d:dd:dd:dd:3976
1202c19:dd:c25:c25d:dd:dd:dd:3977/1282c19:dd:c25:c25d:dd:dd:dd:3977
1212c19:dd:c25:c25d:dd:dd:dd:3978/1282c19:dd:c25:c25d:dd:dd:dd:3978
1222c19:dd:c25:c25d:dd:dd:dd:3979/1282c19:dd:c25:c25d:dd:dd:dd:3979
1232c19:dd:c25:c25d:dd:dd:dd:397a/1282c19:dd:c25:c25d:dd:dd:dd:397a
1242c19:dd:c25:c25d:dd:dd:dd:397b/1282c19:dd:c25:c25d:dd:dd:dd:397b
1252c19:dd:c25:c25d:dd:dd:dd:397c/1282c19:dd:c25:c25d:dd:dd:dd:397c
1262c19:dd:c25:c25d:dd:dd:dd:397d/1282c19:dd:c25:c25d:dd:dd:dd:397d
1272c19:dd:c25:c25d:dd:dd:dd:397e/1282c19:dd:c25:c25d:dd:dd:dd:397e
1282c19:dd:c25:c25d:dd:dd:dd:397f/1282c19:dd:c25:c25d:dd:dd:dd:397f
1292c19:dd:c25:c25d:dd:dd:dd:3980/1282c19:dd:c25:c25d:dd:dd:dd:3980
1302c19:dd:c25:c25d:dd:dd:dd:3981/1282c19:dd:c25:c25d:dd:dd:dd:3981
1312c19:dd:c25:c25d:dd:dd:dd:3982/1282c19:dd:c25:c25d:dd:dd:dd:3982
1322c19:dd:c25:c25d:dd:dd:dd:3983/1282c19:dd:c25:c25d:dd:dd:dd:3983
1332c19:dd:c25:c25d:dd:dd:dd:3984/1282c19:dd:c25:c25d:dd:dd:dd:3984
1342c19:dd:c25:c25d:dd:dd:dd:3985/1282c19:dd:c25:c25d:dd:dd:dd:3985
1352c19:dd:c25:c25d:dd:dd:dd:3986/1282c19:dd:c25:c25d:dd:dd:dd:3986
1362c19:dd:c25:c25d:dd:dd:dd:3987/1282c19:dd:c25:c25d:dd:dd:dd:3987
1372c19:dd:c25:c25d:dd:dd:dd:3988/1282c19:dd:c25:c25d:dd:dd:dd:3988
1382c19:dd:c25:c25d:dd:dd:dd:3989/1282c19:dd:c25:c25d:dd:dd:dd:3989
1392c19:dd:c25:c25d:dd:dd:dd:398a/1282c19:dd:c25:c25d:dd:dd:dd:398a
1402c19:dd:c25:c25d:dd:dd:dd:398b/1282c19:dd:c25:c25d:dd:dd:dd:398b
1412c19:dd:c25:c25d:dd:dd:dd:398c/1282c19:dd:c25:c25d:dd:dd:dd:398c
1422c19:dd:c25:c25d:dd:dd:dd:398d/1282c19:dd:c25:c25d:dd:dd:dd:398d
1432c19:dd:c25:c25d:dd:dd:dd:398e/1282c19:dd:c25:c25d:dd:dd:dd:398e
1442c19:dd:c25:c25d:dd:dd:dd:398f/1282c19:dd:c25:c25d:dd:dd:dd:398f
1452c19:dd:c25:c25d:dd:dd:dd:3990/1282c19:dd:c25:c25d:dd:dd:dd:3990
1462c19:dd:c25:c25d:dd:dd:dd:3991/1282c19:dd:c25:c25d:dd:dd:dd:3991
1472c19:dd:c25:c25d:dd:dd:dd:3992/1282c19:dd:c25:c25d:dd:dd:dd:3992
1482c19:dd:c25:c25d:dd:dd:dd:3993/1282c19:dd:c25:c25d:dd:dd:dd:3993
1492c19:dd:c25:c25d:dd:dd:dd:3994/1282c19:dd:c25:c25d:dd:dd:dd:3994
1502c19:dd:c25:c25d:dd:dd:dd:3995/1282c19:dd:c25:c25d:dd:dd:dd:3995
1512c19:dd:c25:c25d:dd:dd:dd:3996/1282c19:dd:c25:c25d:dd:dd:dd:3996
1522c19:dd:c25:c25d:dd:dd:dd:3997/1282c19:dd:c25:c25d:dd:dd:dd:3997
1532c19:dd:c25:c25d:dd:dd:dd:3998/1282c19:dd:c25:c25d:dd:dd:dd:3998
1542c19:dd:c25:c25d:dd:dd:dd:3999/1282c19:dd:c25:c25d:dd:dd:dd:3999
1552c19:dd:c25:c25d:dd:dd:dd:399a/1282c19:dd:c25:c25d:dd:dd:dd:399a
1562c19:dd:c25:c25d:dd:dd:dd:399b/1282c19:dd:c25:c25d:dd:dd:dd:399b
1572c19:dd:c25:c25d:dd:dd:dd:399c/1282c19:dd:c25:c25d:dd:dd:dd:399c
1582c19:dd:c25:c25d:dd:dd:dd:399d/1282c19:dd:c25:c25d:dd:dd:dd:399d
1592c19:dd:c25:c25d:dd:dd:dd:399e/1282c19:dd:c25:c25d:dd:dd:dd:399e
1602c19:dd:c25:c25d:dd:dd:dd:399f/1282c19:dd:c25:c25d:dd:dd:dd:399f
1612c19:dd:c25:c25d:dd:dd:dd:39a0/1282c19:dd:c25:c25d:dd:dd:dd:39a0
1622c19:dd:c25:c25d:dd:dd:dd:39a1/1282c19:dd:c25:c25d:dd:dd:dd:39a1
1632c19:dd:c25:c25d:dd:dd:dd:39a2/1282c19:dd:c25:c25d:dd:dd:dd:39a2
1642c19:dd:c25:c25d:dd:dd:dd:39a3/1282c19:dd:c25:c25d:dd:dd:dd:39a3
1652c19:dd:c25:c25d:dd:dd:dd:39a4/1282c19:dd:c25:c25d:dd:dd:dd:39a4
1662c19:dd:c25:c25d:dd:dd:dd:39a5/1282c19:dd:c25:c25d:dd:dd:dd:39a5
1672c19:dd:c25:c25d:dd:dd:dd:39a6/1282c19:dd:c25:c25d:dd:dd:dd:39a6
1682c19:dd:c25:c25d:dd:dd:dd:39a7/1282c19:dd:c25:c25d:dd:dd:dd:39a7
1692c19:dd:c25:c25d:dd:dd:dd:39a8/1282c19:dd:c25:c25d:dd:dd:dd:39a8
1702c19:dd:c25:c25d:dd:dd:dd:39a9/1282c19:dd:c25:c25d:dd:dd:dd:39a9
1712c19:dd:c25:c25d:dd:dd:dd:39aa/1282c19:dd:c25:c25d:dd:dd:dd:39aa
1722c19:dd:c25:c25d:dd:dd:dd:39ab/1282c19:dd:c25:c25d:dd:dd:dd:39ab
1732c19:dd:c25:c25d:dd:dd:dd:39ac/1282c19:dd:c25:c25d:dd:dd:dd:39ac
1742c19:dd:c25:c25d:dd:dd:dd:39ad/1282c19:dd:c25:c25d:dd:dd:dd:39ad
1752c19:dd:c25:c25d:dd:dd:dd:39ae/1282c19:dd:c25:c25d:dd:dd:dd:39ae
1762c19:dd:c25:c25d:dd:dd:dd:39af/1282c19:dd:c25:c25d:dd:dd:dd:39af
1772c19:dd:c25:c25d:dd:dd:dd:39b0/1282c19:dd:c25:c25d:dd:dd:dd:39b0
1782c19:dd:c25:c25d:dd:dd:dd:39b1/1282c19:dd:c25:c25d:dd:dd:dd:39b1
1792c19:dd:c25:c25d:dd:dd:dd:39b2/1282c19:dd:c25:c25d:dd:dd:dd:39b2
1802c19:dd:c25:c25d:dd:dd:dd:39b3/1282c19:dd:c25:c25d:dd:dd:dd:39b3
1812c19:dd:c25:c25d:dd:dd:dd:39b4/1282c19:dd:c25:c25d:dd:dd:dd:39b4
1822c19:dd:c25:c25d:dd:dd:dd:39b5/1282c19:dd:c25:c25d:dd:dd:dd:39b5
1832c19:dd:c25:c25d:dd:dd:dd:39b6/1282c19:dd:c25:c25d:dd:dd:dd:39b6
1842c19:dd:c25:c25d:dd:dd:dd:39b7/1282c19:dd:c25:c25d:dd:dd:dd:39b7
1852c19:dd:c25:c25d:dd:dd:dd:39b8/1282c19:dd:c25:c25d:dd:dd:dd:39b8
1862c19:dd:c25:c25d:dd:dd:dd:39b9/1282c19:dd:c25:c25d:dd:dd:dd:39b9
1872c19:dd:c25:c25d:dd:dd:dd:39ba/1282c19:dd:c25:c25d:dd:dd:dd:39ba
1882c19:dd:c25:c25d:dd:dd:dd:39bb/1282c19:dd:c25:c25d:dd:dd:dd:39bb
1892c19:dd:c25:c25d:dd:dd:dd:39bc/1282c19:dd:c25:c25d:dd:dd:dd:39bc
1902c19:dd:c25:c25d:dd:dd:dd:39bd/1282c19:dd:c25:c25d:dd:dd:dd:39bd
1912c19:dd:c25:c25d:dd:dd:dd:39be/1282c19:dd:c25:c25d:dd:dd:dd:39be
1922c19:dd:c25:c25d:dd:dd:dd:39bf/1282c19:dd:c25:c25d:dd:dd:dd:39bf
1932c19:dd:c25:c25d:dd:dd:dd:39c0/1282c19:dd:c25:c25d:dd:dd:dd:39c0
1942c19:dd:c25:c25d:dd:dd:dd:39c1/1282c19:dd:c25:c25d:dd:dd:dd:39c1
1952c19:dd:c25:c25d:dd:dd:dd:39c2/1282c19:dd:c25:c25d:dd:dd:dd:39c2
1962c19:dd:c25:c25d:dd:dd:dd:39c3/1282c19:dd:c25:c25d:dd:dd:dd:39c3
1972c19:dd:c25:c25d:dd:dd:dd:39c4/1282c19:dd:c25:c25d:dd:dd:dd:39c4
1982c19:dd:c25:c25d:dd:dd:dd:39c5/1282c19:dd:c25:c25d:dd:dd:dd:39c5
1992c19:dd:c25:c25d:dd:dd:dd:39c6/1282c19:dd:c25:c25d:dd:dd:dd:39c6
2002c19:dd:c25:c25d:dd:dd:dd:39c7/1282c19:dd:c25:c25d:dd:dd:dd:39c7
2012c19:dd:c25:c25d:dd:dd:dd:39c8/1282c19:dd:c25:c25d:dd:dd:dd:39c8
2022c19:dd:c25:c25d:dd:dd:dd:39c9/1282c19:dd:c25:c25d:dd:dd:dd:39c9
2032c19:dd:c25:c25d:dd:dd:dd:39ca/1282c19:dd:c25:c25d:dd:dd:dd:39ca
2042c19:dd:c25:c25d:dd:dd:dd:39cb/1282c19:dd:c25:c25d:dd:dd:dd:39cb
2052c19:dd:c25:c25d:dd:dd:dd:39cc/1282c19:dd:c25:c25d:dd:dd:dd:39cc
2062c19:dd:c25:c25d:dd:dd:dd:39cd/1282c19:dd:c25:c25d:dd:dd:dd:39cd
2072c19:dd:c25:c25d:dd:dd:dd:39ce/1282c19:dd:c25:c25d:dd:dd:dd:39ce
2082c19:dd:c25:c25d:dd:dd:dd:39cf/1282c19:dd:c25:c25d:dd:dd:dd:39cf
2092c19:dd:c25:c25d:dd:dd:dd:39d0/1282c19:dd:c25:c25d:dd:dd:dd:39d0
2102c19:dd:c25:c25d:dd:dd:dd:39d1/1282c19:dd:c25:c25d:dd:dd:dd:39d1
2112c19:dd:c25:c25d:dd:dd:dd:39d2/1282c19:dd:c25:c25d:dd:dd:dd:39d2
2122c19:dd:c25:c25d:dd:dd:dd:39d3/1282c19:dd:c25:c25d:dd:dd:dd:39d3
2132c19:dd:c25:c25d:dd:dd:dd:39d4/1282c19:dd:c25:c25d:dd:dd:dd:39d4
2142c19:dd:c25:c25d:dd:dd:dd:39d5/1282c19:dd:c25:c25d:dd:dd:dd:39d5
2152c19:dd:c25:c25d:dd:dd:dd:39d6/1282c19:dd:c25:c25d:dd:dd:dd:39d6
2162c19:dd:c25:c25d:dd:dd:dd:39d7/1282c19:dd:c25:c25d:dd:dd:dd:39d7
2172c19:dd:c25:c25d:dd:dd:dd:39d8/1282c19:dd:c25:c25d:dd:dd:dd:39d8
2182c19:dd:c25:c25d:dd:dd:dd:39d9/1282c19:dd:c25:c25d:dd:dd:dd:39d9
2192c19:dd:c25:c25d:dd:dd:dd:39da/1282c19:dd:c25:c25d:dd:dd:dd:39da
2202c19:dd:c25:c25d:dd:dd:dd:39db/1282c19:dd:c25:c25d:dd:dd:dd:39db
2212c19:dd:c25:c25d:dd:dd:dd:39dc/1282c19:dd:c25:c25d:dd:dd:dd:39dc
2222c19:dd:c25:c25d:dd:dd:dd:39dd/1282c19:dd:c25:c25d:dd:dd:dd:39dd
2232c19:dd:c25:c25d:dd:dd:dd:39de/1282c19:dd:c25:c25d:dd:dd:dd:39de
2242c19:dd:c25:c25d:dd:dd:dd:39df/1282c19:dd:c25:c25d:dd:dd:dd:39df
2252c19:dd:c25:c25d:dd:dd:dd:39e0/1282c19:dd:c25:c25d:dd:dd:dd:39e0
2262c19:dd:c25:c25d:dd:dd:dd:39e1/1282c19:dd:c25:c25d:dd:dd:dd:39e1
2272c19:dd:c25:c25d:dd:dd:dd:39e2/1282c19:dd:c25:c25d:dd:dd:dd:39e2
2282c19:dd:c25:c25d:dd:dd:dd:39e3/1282c19:dd:c25:c25d:dd:dd:dd:39e3
2292c19:dd:c25:c25d:dd:dd:dd:39e4/1282c19:dd:c25:c25d:dd:dd:dd:39e4
2302c19:dd:c25:c25d:dd:dd:dd:39e5/1282c19:dd:c25:c25d:dd:dd:dd:39e5
2312c19:dd:c25:c25d:dd:dd:dd:39e6/1282c19:dd:c25:c25d:dd:dd:dd:39e6
2322c19:dd:c25:c25d:dd:dd:dd:39e7/1282c19:dd:c25:c25d:dd:dd:dd:39e7
2332c19:dd:c25:c25d:dd:dd:dd:39e8/1282c19:dd:c25:c25d:dd:dd:dd:39e8
2342c19:dd:c25:c25d:dd:dd:dd:39e9/1282c19:dd:c25:c25d:dd:dd:dd:39e9
2352c19:dd:c25:c25d:dd:dd:dd:39ea/1282c19:dd:c25:c25d:dd:dd:dd:39ea
2362c19:dd:c25:c25d:dd:dd:dd:39eb/1282c19:dd:c25:c25d:dd:dd:dd:39eb
2372c19:dd:c25:c25d:dd:dd:dd:39ec/1282c19:dd:c25:c25d:dd:dd:dd:39ec
2382c19:dd:c25:c25d:dd:dd:dd:39ed/1282c19:dd:c25:c25d:dd:dd:dd:39ed
2392c19:dd:c25:c25d:dd:dd:dd:39ee/1282c19:dd:c25:c25d:dd:dd:dd:39ee
2402c19:dd:c25:c25d:dd:dd:dd:39ef/1282c19:dd:c25:c25d:dd:dd:dd:39ef
2412c19:dd:c25:c25d:dd:dd:dd:39f0/1282c19:dd:c25:c25d:dd:dd:dd:39f0
2422c19:dd:c25:c25d:dd:dd:dd:39f1/1282c19:dd:c25:c25d:dd:dd:dd:39f1
2432c19:dd:c25:c25d:dd:dd:dd:39f2/1282c19:dd:c25:c25d:dd:dd:dd:39f2
2442c19:dd:c25:c25d:dd:dd:dd:39f3/1282c19:dd:c25:c25d:dd:dd:dd:39f3
2452c19:dd:c25:c25d:dd:dd:dd:39f4/1282c19:dd:c25:c25d:dd:dd:dd:39f4
2462c19:dd:c25:c25d:dd:dd:dd:39f5/1282c19:dd:c25:c25d:dd:dd:dd:39f5
2472c19:dd:c25:c25d:dd:dd:dd:39f6/1282c19:dd:c25:c25d:dd:dd:dd:39f6
2482c19:dd:c25:c25d:dd:dd:dd:39f7/1282c19:dd:c25:c25d:dd:dd:dd:39f7
2492c19:dd:c25:c25d:dd:dd:dd:39f8/1282c19:dd:c25:c25d:dd:dd:dd:39f8
2502c19:dd:c25:c25d:dd:dd:dd:39f9/1282c19:dd:c25:c25d:dd:dd:dd:39f9
2512c19:dd:c25:c25d:dd:dd:dd:39fa/1282c19:dd:c25:c25d:dd:dd:dd:39fa
2522c19:dd:c25:c25d:dd:dd:dd:39fb/1282c19:dd:c25:c25d:dd:dd:dd:39fb
2532c19:dd:c25:c25d:dd:dd:dd:39fc/1282c19:dd:c25:c25d:dd:dd:dd:39fc
2542c19:dd:c25:c25d:dd:dd:dd:39fd/1282c19:dd:c25:c25d:dd:dd:dd:39fd
2552c19:dd:c25:c25d:dd:dd:dd:39fe/1282c19:dd:c25:c25d:dd:dd:dd:39fe
2562c19:dd:c25:c25d:dd:dd:dd:39ff/1282c19:dd:c25:c25d:dd:dd:dd:39ff

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.