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IPv6 Tutorial

June 24th, 2011 Go to comments

The Internet Corporation for Assigned Names and Numbers (ICANN) is responsible for the assignment of IPv6 addresses. ICANN assigns a range of IP addresses to Regional Internet Registry (RIR) organizations. The size of address range assigned to the RIR may vary but with a minimum prefix of /12 and belong to the following range: 2000::/12 to 200F:FFFF:FFFF:FFFF::/64.


Each ISP receives a /32 and provides a /48 for each site-> every ISP can provide 2(48-32) = 65,536 site addresses (note: each network organized by a single entity is often called a site).
Each site provides /64 for each LAN -> each site can provide 2(64-48) = 65,536 LAN addresses for use in their private networks.
So each LAN can provide 264 interface addresses for hosts.

-> Global routing information is identified within the first 64-bit prefix.
Note: The number that represents the range of addresses is called a prefix



Now let’s see an example of IPv6 prefix: 2001:0A3C:5437:ABCD::/64:


In this example, the RIR has been assigned a 12-bit prefix. The ISP has been assigned a 32-bit prefix and the site is assigned a 48-bit site ID. The next 16-bit is the subnet field and it can allow 216, or 65536 subnets. This number is redundant for largest corporations on the world!

The 64-bit left (which is not shown the above example) is the Interface ID or host part and it is much more bigger: 64 bits or 264 hosts per subnet! For example, from the prefix 2001:0A3C:5437:ABCD::/64 an administrator can assign an IPv6 address 2001:0A3C:5437:ABCD:218:34EF:AD34:98D to a host.

IPv6 Address Scopes

Address types have well-defined destination scopes:


IPv6 Address Scopes              
Link-local address + only used between neighbors on the same link (automatic address configuration, neighbor discovery, router discovery, and by many routing protocols). It is only valid on the current subnet.
+ are always automatically configured
+ routers do not forward packets with link-local addresses
+ are allocated with the FE80::/64 prefix -> can be easily recognized by the prefix FE80. Some books indicate the range of link-local address is FE80::/10, meaning the first 10 bits are fixed and link-local address can begin with FE80, FE90,FEA0 and FEB0 but in fact the next 54 bits are all 0s so you will only see the prefix FE80 for link-local address
+ same as 169.254.x.x in IPv4 (APIPA address), it is assigned when a DHCP server is unavailable and no static addresses have been assigned
+ is usually created dynamically using a link-local prefix of FE80::/10 and a 64-bit interface identifier (based on 48-bit MAC address)
Site-local address + used between nodes communicating with other nodes in the same site
+ allows devices in the same organization, or site, to exchange data
+ starts with FC00::/7 (for used in private networks). They are analogous to IPv4’s private address classes.
+ Maybe you will be surprised but Site-local addresses are no longer supported (deprecated) by RFC 3879 so maybe you will not see it in the future
Global unicast address + unicast packets sent through the public Internet (equivalent to public IPv4 addresses)
+ globally unique throughout the Internet
+ starts with a 2000::/3 prefix (this means any address beginning with 2 or 3). But in the future global unicast address might not have this limitation

All nodes must have at least one link-local address, although each interface can have multiple addresses (which is different from IPv4 address where each interface can only have one IPv4 address).

However, using them would also mean that NAT would be required and addresses would again not be end-to-end.
Site-local addresses are no longer supported (deprecated) by RFC 3879.

Special IPv6 Addresses

Reserved Multicast Address Description
FF02::1 + All nodes on a link (link-local scope).
FF02::2 + All routers on a link
FF02::5 + OSPFv3 All SPF routers
FF02::6 + OSPFv3 All DR routers
FF02::9 + All routing information protocol (RIP) routers on a link
FF02::A + EIGRP routers
FF02::1:FFxx:xxxx + All solicited-node multicast addresses used for host auto-configuration and neighbor discovery (similar to ARP in IPv4)
+ The xx:xxxx is the far right 24 bits of the corresponding unicast or anycast address of the node
FF05::101 + All Network Time Protocol (NTP) servers

Note: When an interface is configured with IPv6 address, it  automatically joins the all nodes (FF02::1) and solicited-node (FF02::1:FFxx:xxxx) multicast groups. The all-node group is used to communicate with all interfaces on the local link, and the solicited-nodes multicast group is required for link-layer address resolution. Routers also join a third multicast group, the all-routers group (FF02::2).

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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