Configuration Guide IPv6 Configuration
RES field (Reserved for future use):
Reservation field, 8 bits. It will possibly be used to expand the top level or the next
level aggregation identifier field.
NLA ID field (Next-Level Aggregation Identifier):
Next-Level Aggregation Identifier, 24 bits. This identifier is used to control the top-level
aggregation to arrange the address space by some institutions. In other word, these
institutions (such as the large-sized ISP) can separate the 24-bit field according to the
addressing level structure themselves. For instance, a large-sized ISP can separate it
into 4 internal top-level routes by 2 bits, other 22 bits of the address space is assigned
to other entities (such as the small-sized local ISP). If these entities obtain enough
address space, the same measure can be taken to subdivide the space assigned to
them.
SLA ID field (Site-Level Aggregation Identifier):
Site-Level Aggregation Identifier, used to arrange internal network structures by some
institutions. Each institution can use the same way as that in the IPv4 to create the
hierarchical network structure themselves. If the 16 bits are taken as the plane
address space, there are up to 65535 different subnets. If the former 8 bits are taken
as the higher-level of routes within this organization, 255 large-scale subnets are
allowed. Furthermore, each large-scale subnet can be subdivided into up to 255
small-scale subnets.
Interface Identifier field (Interface Identifier):
It is 64 bits long and contains the 64 bit value of IEEE EUI-64 interface identifiers.
2. Link Local Addresses
The format of the link-level local addresses is shown as follows:
| 10 |
| bits | 54 bits | 64 bits |
+-------------+----------------------------------+--------------------------------------+
|1111111010| 0 | interface ID |
+-------------+----------------------------------+--------------------------------------+
The link-level local address is used to number the host on the single network link. The
address of former 10-bit identification for the prefix is the link-level local address. The
router will not forward the message of the source address of the destination address
with the link-level local address forever. The intermediate 54-bit of this address is 0.
The latter 64 indicates the interface identifier, this part allows the single network to
connect to up to 2
64
-1 hosts.
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