* 2002::/16 -- This is used by [6to4] 

 * FE80::/64 -- LinkLocal 

 * FEC0::/48 -- SiteLocal 

 * ::FFFF:aabb:ccdd -- Used for IPv4 addresses (a.b.c.d) 

  

  

 !!Notation 

 The preferred form for writing IPv6 addresses is x:x:x:x:x:x:x:x where each x represents the hexadecimal values of 16 bits of the address. Examples: 

  

 Due to the way that some IPv6 addresses are allocated it will be common for some addresses to have long strings of zeros in them, making them tedious to write using the above representation. The standard defines a special syntax that can be used to compress the groups of zeros. Use of the "::" indicates indicates multiple groups of 16-bits of 0. The "::" notation can only be used once in an address and can also be used to compress leading or trailing zeros. Examples: 

  

  

 An IPv6 address prefix is represented by the notation ipv6-address/prefix-length where 

  

 For example, the following are legal representations of the 60-bit prefix 12AB00000000CD3 (hexadecimal): 

 The following are NOT legal representations of the above prefix: 

  

  

 !!Types of Address 

 There are several different types of [IPv6] address defined by the standads. The type is specified by the leading bits of an address, this field is variable-length and is called the FormatPrefix (FP). Refer to RFC2373 for the currently defined FP's some of the more common ones are. 

  

 !Aggregatable Global Unicast Addresses - RFC2374 

 This is probably going to be the most widely used of the IPv6 address formats and is what is currently being allocated by the RIRs and is in use on the 6Bone. The format of a Aggregatable Global Unicast Addresses (AGUA) address looks like this. 

 Where 

  

 An important concept to grasp is that these fields in the address are used only for allocation, they are not directly used for routing. Routing of IPv6 addresses is based on prefix length, although sometimes the prefix length will be based on one of the fields above this does not always need to be the case. To explain how each field is used imagine an IPv6 internet which consists of a tight mesh of directly connected backbone nodes in the centre, moving out from this you reach transit nodes which have a connection to a subset of the backbone nodes (usually between 1 - 4) each of these transit nodes is then connected to a number of edge nodes. This structure is almost identical to the structure of the 6Bone and possibly today's IPv4 internet. 

  

  

  

  

  

 Both the NLA ID and SLA ID fields can be nested multiple times. 

  

  

  

 !Link-Local Unicast Addresses 

 Link-Local addresses are designed to be used for addressing on a single link for purposes such as auto-address configuration, neighbor discovery, or when no routers are present. Their format is as follows. Routers must not forward packets with link-local addresses to other links. 

  

  

 In hex, this would be fe80:0:0:0:0:0:0:(ID), or fe80::(ID) if collapsing zeroes. 

  

 Example: 

  eth0 Link encap:Ethernet HWaddr 00:E0:4C:39:43:BB 

  inet addr:10.21.1.2 Bcast:10.21.1.255 Mask:255.255.255.0 

  inet6 addr: fe80::2e0:4cff:fe39:43bb/64 Scope:Link 

  

 ''Anyone know where the extra bits (02, ff:fe) in the interface ID came from (they aren't in the [MAC] address)?'' 

  

 The 2 in 02 is from the universally unique bit being flipped in IPv6 addresses so you can easily type addresses like fe80::1 (the 2 bit is clear meaning that this is a non universally unique suffix) 

 ff:fe is inserted and means "Ethernet MAC" I think. 

  

 !Site-Local Unicast Addresses 

 Site-Local addresses are designed to be used for addressing inside of a site without the need for a global prefix. Routers must not forward any packets with site-local source or destination addresses outside of the site. These addresses are analogous to the RFC:1918 IPv4 addresses in use by many organisations today. 

  

 In hex, this is fec0:0:0:0:0:(ID) or fec0::(ID). 

  

 Site local addresses are currently deprecated and are likely to be replaced by some other similar mechanism which isn't so prone to address usage collisions. 

  

 !Multicast Addresses 

 An IPv6 multicast address is an identifier for a group of nodes. A node may belong to any number of multicast groups. Multicast addresses have the following format: 

  

 The flgs field contains information about whether the group id is a well defined group (Assigned by IANA) or a temporary group. 

 The scop field contains information about the scope of the address, it can be used to define groups of machines such as 

 * All Routers on the same link as the sender 

 * All Routers at the same site as the sender 

 * All Routers on the internet! 

  

  

 !Special Addresses 

 Just like IPv4 has special addresses for thinks like loopback, network and broadcast so does IPv6. 

  

  

  

 !! References 

  

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 CategoryNetworking