3Com Switch 8800 Advanced Software V5 Configuration Guide

678 CHAPTER 46: IPV6 PIM CONFIGURATION
based on the BSR mechanism. The DR does not need to know the RP address
beforehand. The specific process is as follows.
■ At the receiver side:
1 A receiver host initiates an MLD report to announce joining an IPv6 multicast
group.
2 Upon receiving the MLD report, the receiver-side DR resolves the RP address
embedded in the IPv6 multicast address, and sends a join message to the RP.
■ At the IPv6 multicast source side:
1 Upon getting the IPv6 multicast address, the IPv6 multicast source starts sending
IPv6 multicast traffic to the IPv6 multicast group.
2 The source-side DR resolves the RP address embedded in the IPv6 multicast
address, and sends a register message to the RP by unicast.
n
Currently, the IPv6 multicast address range for embedded RP used by the Switch
8800s is FF7x::/12 or FFFx::/12, where "x" refers to the Scope field in the IPv6
multicast address. Different values define different scopes. For details about the
Scope field, refer to
“IPv6 Multicast Addresses” on page 498.
Extracting an embedded RP address
Figure 205 shows the structure of an IPv6 multicast address with an embedded RP
address. Fields of such an IPv6 address are described as follows:
■ FF7x: The first 16 bits of an IPv6 multicast address with an embedded RP
address must be FF7x or FFFx.
■ rsv: Reserved bits.
■ RIID: Interface ID of the RP.
■ plen: Obtained prefix length, in the hexadecimal notation. The maximum value
is 40, indicating to copy the first 4*16 (64) bits of the prefix to the IPv6 unicast
address structure of the RP.
■ prefix: Prefix of the RP’s IPv6 address. The maximum length is 64 bits.
■ group ID: IPv6 multicast group ID.
Figure 205 Structure of an IPv6 multicast address with an embedded RP address
Figure 206 shows the structure of an RP address extracted an IPv6 address.
Figure 206 Extracted IPv6 unicast address of the RP
group ID
netw ork prefix
FF7x
rsv
RIID
plen prefix group ID
161202432
12896
group ID
netw ork prefix
FF7x
rsv
RIID
plen prefix group ID
161202432
12896
prefix RIID
netw ork prefix
group ID
zero
1
128124
prefix RIID
netw ork prefix
group ID
zero
1
128
prefix RIID
netw ork prefix
group ID
zero
1
128124