403The C-RP timers need to be configured on C-RP routers.To configure C-RP timers globally:Step Command Remarks1. Enter system view. system-view N/A2. Enter IPv6 PIM view. pim ipv6 N/A3. Configure the C-RP-Advinterval. c-rp advertisement-interval interval Optional.60 seconds by default.4. Configure C-RP timeout time. c-rp holdtime interval Optional.150 seconds by default.For more information about the configuration of other timers in IPv6 PIM-SM, see "Configuring IPv6 PIMcommon timers."Configuring a BSRAn IPv6 BIDIR-PIM domain can have only one BSR, but must have at least one C-BSR. Any router can beconfigured as a C-BSR. Elected from C-BSRs, the BSR collects and advertises RP information in the IPv6BIDIR-PIM domain.Configuring a C-BSRC-BSRs must be configured on routers on the backbone network. When you configure a router as a C-BSR,be sure to specify an IPv6 PIM-SM-enabled interface on the router. The BSR election process is as follows:• Initially, every C-BSR assumes itself to be the BSR of the IPv6 BIDIR-PIM domain, and uses itsinterface IPv6 address as the BSR address to send bootstrap messages.• When a C-BSR receives the bootstrap message of another C-BSR, it first compares its own prioritywith the other C-BSR's priority carried in message. The C-BSR with a higher priority wins. If a tieexists in the priority, the C-BSR with a higher IPv6 address wins. The loser uses the winner's BSRaddress to replace its own BSR address and no longer assumes itself to be the BSR, and the winnerretains 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 theaddress range, thus to prevent a maliciously configured host from masquerading as a BSR. The sameconfiguration must be made on all routers in the IPv6 BIDIR-PIM domain. The following are typical BSRspoofing cases and the corresponding preventive measures:• Some maliciously configured hosts can forge bootstrap messages to fool routers and change RPmappings. Such attacks often occur on border routers. Because a BSR is inside the network whereashosts are outside the network, you can protect a BSR against attacks from external hosts by enablingthe border routers to perform neighbor checks and RPF checks on bootstrap messages and discardunwanted messages.• When a router in the network is controlled by an attacker or when an illegal router is present in thenetwork, the attacker can configure this router as a C-BSR and make it win BSR election to control
