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IPv6 Tutorial

June 24th, 2011 Go to comments

Internet has been growing extremely fast so the IPv4 addresses are quickly approaching complete depletion. Although many organizations already use Network Address Translators (NATs) to map multiple private address spaces to a single public IP address but they have to face with other problems from NAT (the use of the same private address, security…). Moreover, many other devices than PC & laptop are requiring an IP address to go to the Internet. To solve these problems in long-term, a new version of the IP protocol – version 6 (IPv6) was created and developed.

IPv6 was created by the Internet Engineering Task Force (IETF), a standards body, as a replacement to IPv4 in 1998. So what happened with IPv5? IP Version 5 was defined for experimental reasons and never was deployed.

While IPv4 uses 32 bits to address the IP (provides approximately 232 = 4,294,967,296 unique addresses – but in fact about 3.7 billion addresses are assignable because the IPv4 addressing system separates the addresses into classes and reserves addresses for multicasting, testing, and other specific uses), IPv6 uses up to 128 bits which provides 2128 addresses or approximately 3.4 * 1038 addresses. Well, maybe we should say it is extremely extremely extremely huge :)

IPv6 Address Types

Address Type Description
Unicast One to One (Global, Link local, Site local)
+ An address destined for a single interface.
Multicast One to Many
+ An address for a set of interfaces
+ Delivered to a group of interfaces identified by that address.
+ Replaces IPv4 “broadcast”
Anycast One to Nearest (Allocated from Unicast)
+ Delivered to the closest interface as determined by the IGP

A single interface may be assigned multiple IPv6 addresses of any type (unicast, anycast, multicast)

Note: There is no broadcast address in IPv6

IPv6 address format


x:x:x:x:x:x:x:x – where x is a 16 bits hexadecimal field and x represents four hexadecimal digits.
An example of IPv6:

There are:
+ 8 groups of 4 hexadecimal digits.
+ Each group represents 16 bits (4 hexa digits * 4 bit)
+ Separator is “:”
+ Hex digits are not case sensitive, so “DBCA” is same as “dbca” or “DBca”…

IPv6 (128-bit) address contains two parts:
+ The first 64-bits is known as the prefix. The prefix includes the network and subnet address. Because addresses are allocated based on physical location, the prefix also includes global routing information. The 64-bit prefix is often referred to as the global routing prefix.
+ The last 64-bits is the interface ID. This is the unique address assigned to an interface.

Note: Addresses are assigned to interfaces (network connections), not to the host. Each interface can have more than one IPv6 address.

Rules for abbreviating IPv6 Addresses:

+ Leading zeros in a field are optional

2001:0DA8:E800:0000:0260:3EFF:FE47:0001 can be written as


+ Successive fields of 0 are represented as ::, but only once in an address:

2001:0DA8:E800:0000:0000:0000:0000:0001 -> 2001:DA8:E800::1

Other examples:
– FF02:0:0:0:0:0:0:1 => FF02::1
– 3FFE:0501:0008:0000:0260:97FF:FE40:EFAB = 3FFE:501:8:0:260:97FF:FE40:EFAB = 3FFE:501:8::260:97FF:FE40:EFAB
– 0:0:0:0:0:0:0:1 => ::1
– 0:0:0:0:0:0:0:0 => ::

IPv6 Addressing In Use

IPv6 uses the “/” notation to denote how many bits in the IPv6 address represent the subnet.

The full syntax of IPv6 is


+ ipv6-address is the 128-bit IPv6 address
+ /prefix-length is a decimal value representing how many of the left most contiguous bits of the address comprise the prefix.

Let’s analyze an example:
2001:C:7:ABCD::1/64 is really
+ The first 64-bits 2001:000C:0007:ABCD is the address prefix
+ The last 64-bits 0000:0000:0000:0001 is the interface ID
+ /64 is the prefix length (/64 is well-known and also the prefix length in most cases)

In the next part, we will understand more about each prefix of an IPv6 address.

Comments (50) Comments
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  1. RaghuByrraju
    June 26th, 2012

    That was really helpful…Thank u 9tut mods!!!

  2. Anonymous
    July 9th, 2012

    It is really easy to understand and helpful.

  3. Deba (070902)
    July 9th, 2012

    It is really easy to understand and helpful.

  4. ramu
    July 29th, 2012

    it’s really helpful…….

  5. TheLordsSon
    July 30th, 2012

    Very helpful

  6. McCafe
    July 31st, 2012

    Can someone please explain why 2001:0DB8:0:130H::87c:140B is not a valid IPv6 address? thanks!

  7. Suddha
    August 5th, 2012

    Undoubtedly very good information – easy to understand & very composed way to understand IPv6 …

    Need to discuss EUI-64 format..

    Thanks a lot dear.

  8. Suddha
    August 5th, 2012

    Reply TO @McCafe– Hex is represented by 0-9 & A,B,C,D,E & F….How “H” can comes in address.

  9. Izzy
    August 11th, 2012

    Beware. There are several IPV6 questions on the exam.

  10. edegs
    August 19th, 2012

    tnx sir for sharing this …….\m/ .

  11. jfrodo
    August 23rd, 2012

    In collisio dumps how is 2004:1:25A4:886F::1 a valid ipv6 address? Aren’t the ipv6 addresses always supposed to be 8 not 7 fields? I thought double colon represents 2 sets of zero abbreviated as ::

  12. ipv6 is very helpful.
    September 5th, 2012

    rajesh kumar

  13. chandana bandara
    October 1st, 2012

    great help

  14. mohamed
    October 10th, 2012

    very helpful

  15. blarg
    November 16th, 2012

    @jfrodo, :: means a contiguous set of zeros, which can be more than two sets.
    2004:1:25A4:886F::1 is 2004:0001:25A4:886F:0000:0000:0000:0001

  16. Mike
    December 12th, 2012

    Thank you so much. I read it from the book and couldn’t understand it much.
    However your explanation is supper clear.

  17. Rahul
    January 5th, 2013

    i understand something something in above information, but please tell me what will be the classes of IPv6. what will be 1st address of each class…

  18. Rahul
    January 5th, 2013

    is it possible we can use natting by ipv4 to ipv6 or ipv6 to ipv4….

  19. YASSIN
    January 18th, 2013


  20. ruhullah
    January 31st, 2013

    its very easy way to learn about ipv6

  21. Radouane
    February 3rd, 2013

    Think you, very helpful

  22. Neeraj
    February 8th, 2013

    Really helpful thx

  23. ncnoman
    February 14th, 2013

    Why does this not cover unique local addresses…? it mentions the depracation of site-local… considering unique-local is the current IPv6 private addressing method (RFC 4193), this is an incomplete IPv6 crash course without it. A great history lesson but most of us are looking for current knowledge… jus’ sayin.

  24. brent
    February 26th, 2013

    This is very helpful for sure and you find it easy to understand the IPV6 address

  25. Reza
    March 3rd, 2013

    thanks alot 9tut ….

  26. Siddiqmca
    March 11th, 2013

    Really helpful…

  27. Shankar
    March 13th, 2013

    Very helpful for beginners. Thanks a lot

  28. Sanjeev Saxena
    April 22nd, 2013

    This is very helpful for sure and you find it easy to understand the IPV6 address.

  29. Jeyaram
    May 25th, 2013

    its very useful…

  30. ALI
    June 18th, 2013

    thanks it is very good

  31. Zee
    June 23rd, 2013

    Its really helpful….. easy to understand ipv6

  32. MBT
    July 15th, 2013

    Good Job!

  33. Narges
    July 22nd, 2013

    Thanks .Very good
    Pls explain how we can identified global, link and site address?

  34. Amit Sharma
    July 27th, 2013

    thanks ,… very useful

  35. ehsan
    August 1st, 2013

    Very good tute

  36. ccna
    September 23rd, 2013


  37. samit khan
    September 23rd, 2013

    thanks tut

  38. ADM223
    September 24th, 2013

    Just what I needed!

  39. mgsn
    September 25th, 2013

    Very good to understand basic of ipv6, you explained very easy and simple way, appreciated your work.

    To further understanding of interface ids, need little more explaination how the interface id starts with 218, 2001:0A3C:5437:ABCD:218:34EF:AD34:98D please explain

  40. Tally
    September 26th, 2013

    @ mgsn

    interface id is 2001:0A3C:5437:ABCD:0218:34EF:AD34:98D bcuz Leading zeros in a field are optional

  41. hemanth
    November 12th, 2013

    thnk u sir it is very useful to networking students

  42. Amri
    December 12th, 2013

    Thank you for a wonderful explanation! am preparing for ccna next month any one with current dumps plz

  43. Riasudin_hcl@yahoo.com
    December 26th, 2013

    Hi, friends kindly send me the recent dumps.. you will live very fine…

  44. Shopnill
    January 10th, 2014

    its very useful tutorial for beginer.Thanks a lot

  45. Anonymous
    January 19th, 2014

    I had a good grip on how addresses are divided an assigned. It is helpful when you explain to learners.


  46. Arthur B.
    January 19th, 2014

    I had a good grip on how addresses are divided an assigned. It is helpful when you explain to learners.


  47. Ronald Brown
    January 26th, 2014

    This is very comprehensive, thanks for the effort, you are awesome….

  48. Nitin Ahuja
    February 4th, 2014

    It’s very simple & informative.

  49. aida
    March 4th, 2014

    i have the exam tomorrow
    can you share if possible new questions?

    thx a lot!

  50. Samib
    March 5th, 2014

    Thank you. It really helped me alot

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