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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.

ipv6_Address_Allocation_Policy.jpg

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


ipv6_policy_ISP.jpg

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

IPv6_prefix_length_example.jpg

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              
Description
Link-local address + only used for communications within the local subnetwork (automatic address configuration, neighbor discovery, router discovery, and by many routing protocols). It is only valid on the current subnet.
+ 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, 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).
Global unicast address + unicast packets sent through the public Internet
+ 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
Site-local address + allows devices in the same organization, or site, to exchange data.
+ starts with the prefix FEC0::/10. They are analogous to IPv4’s private address classes.
+ Maybe you will be surprised because Site-local addresses are no longer supported (deprecated) by RFC 3879 so maybe you will not see it in the future.


All nodes must have at least one link-local address, although each interface can have multiple addresses.

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

Reserved IPv6 Multicast Addresses

Reserved Multicast Address Description
FF02::1 + All nodes on a link (link-local scope).
FF02::2 + All routers on a link
FF02::9 + All routing information protocol (RIP) routers on a link
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

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  1. Jesse Grillo
    August 31st, 2017

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