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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 (15) Comments
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  1. Jesse Grillo
    August 31st, 2017

    You saved me a lot of hassle just now. My Uncle said they love your pages post.


  2. Tarik
    March 19th, 2018

    please in the ipv6 address scopes,specially in the site local @,you have montionned that site local @ start with FEC0::/10,maybe you make mistake,i would like to tell you that are starting with FC00::/7 and ending with FDFF::/7

  3. 9tut
    March 20th, 2018

    @Tarik: Thanks for your information. We have just fixed it! It was FEC0::/10 but it is deprecated now.

  4. Anonymous
    June 5th, 2018

    What is the prefix associated with the IPv6 address 2001:CA48:D15:EA:CC44::1/64?

  5. Anonymous
    June 20th, 2018

    17 What is the prefix associated with the IPv6 address 2001:CA48:D15:EA:CC44::1/64?

  6. Anonymous
    June 28th, 2018

    Has anyone took the CCNA exam recently has their alot of ipv6 questions? My networking classes didn’t include alot of ipv6

  7. Jeramy
    September 13th, 2018

    Passed with the 552q dumps, all questions were from there.

  8. Joe
    September 19th, 2018

    @ Jeramy , please share the referenced dump

    jovinnok at yahoo.com

  9. Lorena
    January 14th, 2019

    @Jeramy, where Can I take the 552q dumps?.

  10. Irfan Basharat
    April 27th, 2019

    Whoever writes these tutorials should take a course in English. I see many grammatical mistakes and as you might know in technical writing one grammatical mistake screws up the whole concept.
    You people want to do a favor and end messing up the whole subject and students mind.

  11. Irfan Basharat
    April 27th, 2019

    I see more and more bad grammar in this tutorial. for example “is” has been used instead of “are” and the sentences are badly written.
    I like to know who wrote these texts.
    Which island are they from?

  12. Irfan Basharat
    April 27th, 2019

    I see more and more bad grammar in this tutorial. for example “is” has been used instead of “are” and the sentences are badly written.
    I like to know who wrote these texts.
    Which island are they from? As an example check this out ” for used in private networks”.
    This idiot instead of saying for “use” he says “for used” LOL

  13. Emanuel
    June 14th, 2019

    Thanks a lot for your tuttorials

  14. Emanuel
    June 14th, 2019

    Hey Irfan Basharat, You should go to another place if you want to read poetry go to a library this is a Technical blog, not a grammar blog.

  15. Lamine
    July 4th, 2019

    @ Irfan, u’re just a bully and an assl, just go jrk somewhere else.

    @ 9tut continue the hardwork u’ve saved many people by helping them pass these exams and get a good professional life.

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