3com S7906E 설치 설명서

 

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For the configuration of other timers in IPv6 PIM-SM, refer to 

 

An IPv6 PIM-SM domain can have only one BSR, but must have at least one C-BSR. Any router can be 

configured as a C-BSR. Elected from C-BSRs, the BSR is responsible for collecting and advertising RP 

information in the IPv6 PIM-SM domain.  

C-BSRs should be configured on routers in the backbone network. When configuring a router as a 

C-BSR, make sure to specify the IPv6 address of an IPv6 PIM-SM enabled interface on the router. The 

BSR election process is summarized as follows:  

z 

Initially, every C-BSR assumes itself to be the BSR of this IPv6 PIM-SM domain, and uses its 

interface IPv6 address as the BSR address to send bootstrap messages.  

z 

When a C-BSR receives the bootstrap message of another C-BSR, it first compares its own priority 

with the other C-BSR’s priority carried in the message. The C-BSR with a higher priority wins. If 

there is a tie in the priority, the C-BSR with a higher IPv6 address wins. The loser uses the winner’s 

BSR address to replace its own BSR address and no longer assumes itself to be the BSR, while 

the winner keeps its own BSR address and continues assuming itself to be the BSR.  

Configuring a legal range of BSR addresses enables filtering of bootstrap messages based on the 

address range, thus to prevent a maliciously configured host from masquerading as a BSR. The same 

configuration needs to be made on all routers in the IPv6 PIM-SM domain. The following are typical 

BSR spoofing cases and the corresponding preventive measures:  

1)  Some maliciously configured hosts can forge bootstrap messages to fool routers and change RP 

mappings. Such attacks often occur on border routers. Because a BSR is inside the network 

whereas hosts are outside the network, you can protect a BSR against attacks from external hosts 

by enabling the border routers to perform neighbor checks and RPF checks on bootstrap 

messages and discard unwanted messages.  

2)  When a router in the network is controlled by an attacker or when an illegal router is present in the 

network, the attacker can configure this router as a C-BSR and make it win BSR election to control 

the right of advertising RP information in the network. After being configured as a C-BSR, a router 

automatically floods the network with bootstrap messages. As a bootstrap message has a hop limit 

value of 1, the whole network will not be affected as long as the neighbor router discards these 

bootstrap messages. Therefore, with a legal BSR address range configured on all routers in the 

entire network, all these routers will discard bootstrap messages from out of the legal address 

range.  

The above-mentioned preventive measures can partially protect the security of BSRs in a network. 

However, if a legal BSR is controlled by an attacker, the above-mentioned problem will also occur. 

Follow these steps to complete basic BSR configuration:  

To do... 

Use the command... 

Remarks 

Enter system view 

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