3com S7906E 설치 설명서

 

1-7 

1)  Routers on the multi-access network send hello messages to one another. The hello messages 

contain the router priority for DR election. The router with the highest DR priority will become the 

DR. 

2)  In the case of a tie in the router priority, or if any router in the network does not support carrying the 

DR-election priority in hello messages, The router with the highest IPv6 link-local address will win 

the DR election.  

When the DR works abnormally, a timeout in receiving hello message triggers a new DR election 

process among the other routers.  

The RP is the core of an IPv6 PIM-SM domain. For a small-sized, simple network, one RP is enough for 

forwarding IPv6 multicast information throughout the network, and the position of the RP can be 

statically specified on each router in the IPv6 PIM-SM domain. In most cases, however, an IPv6 

PIM-SM network covers a wide area and a huge amount of IPv6 multicast traffic needs to be forwarded 

through the RP. To lessen the RP burden and optimize the topological structure of the RPT, multiple 

candidate RPs (C-RPs) can be configured in an IPv6 PIM-SM domain, among which an RP is 

dynamically elected through the bootstrap mechanism. Each elected RP serves a different multicast 

group range. For this purpose, a bootstrap router (BSR) must be configured. The BSR serves as the 

administrative core of the IPv6 PIM-SM domain. An IPv6 PIM-SM domain can have only one BSR, but 

can have multiple candidate-BSRs (C-BSRs). Once the BSR fails, a new BSR is automatically elected 

from the C-BSRs to avoid service interruption. 

 

z 

An RP can serve IPv6 multiple multicast groups or all IPv6 multicast groups. Only one RP can 

serve a given IPv6 multicast group at a time. 

z 

A device can server as a C-RP and a C-BSR at the same time.  

 

As shown in the figure below, each C-RP periodically unicasts its advertisement messages (C-RP-Adv 

messages) to the BSR. A C-RP-Adv message contains the address of the advertising C-RP and the 

IPv6 multicast group range it serves. The BSR collects these advertisement messages and chooses the 

appropriate C-RP information for each multicast group to form an RP-set, which is a database of 

mappings between IPv6 multicast groups and RPs. The BSR then encapsulates the RP-set in the 

bootstrap messages it periodically originates and floods the bootstrap messages to the entire IPv6 

PIM-SM domain.