Chapter 2 IPv6 Basic Configuration
interoperatability, IPv6 reserves 1/128 address space for
OSI NSAP address and network IPX address respectively.
At present, the IPX addresses have not been precisely de-
fined. Refer to RFC 1888 (OSI NSAP and IPv6) for descrip-
tion of the NSAP address allocation.
�
Multicast Address
The format of the IPv6 multicast address is different from that
of the IPv6 unicast address. Multicast addresses can only be
used as destination addresses.
No packet uses a multicast
address as the source address.
shows the format of a
multicast address.
T
ABLE
7 M
ULTICAST
A
DDRESS
F
ORMAT
8
4
4
112
1111111
Flags
Sco-
pe
Group identifier
The first byte of the address format is set to full-one, identify-
ing it as a multicast address. The multicast address occupies
the entire 1/256 of the IPv6 address space. The other parts
except the first byte of the multicast address format contain
the following three fields:
�
Flags field
This field consists of four single bit flags. Currently, only the
bit-4 is designated to indicate that whether this address is
a well-known multicast address designated by the Internet
numbering institution, or a temporary multicast address
used in a specific occasion.
If this flag bit is set to zero, it indicates that this address is a
well-known address. If this flag bit is set to one, it indicates
that this address is a temporary address. The other three
flag bits are reserved for future use.
�
Scope field
This is a 4-bit field and is used to indicate the range of
multicast. That is, whether a multicast group only includes
nodes within the same local network, the same site or the
same institution, or includes nodes that resides anywhere
in the IPv6 global address space. The possible values 4–bits
value ranges from 0 to 15.
shows the corresponding
range.
T
ABLE
8 M
ULTICAST
S
COPE
V
ALUE
Hex
Decimal
Value
0
0
Reserved
1
1
Node-local range
2
2
Link-local range
3
3
Unallocated
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11
Summary of Contents for ZXR10 T1200
Page 5: ...Figures 71 Tables 73 List of Glossary 75 ...
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