H3C Technologies H3C S12500 Series Switches - Manual (Page 404)

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Each C-RP encapsulates a timeout value in its C-RP-Adv messages. After receiving a C-RP-Adv message,
the BSR obtains this timeout value and starts a C-RP timeout timer. If the BSR fails to obtain a subsequent
C-RP-Adv message from the C-RP when the timer times out, the BSR assumes the C-RP to have expired or
become unreachable.
You must configure the C-RP timers on C-RP routers.
To configure C-RP timers globally:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter IPv6 PIM view. pim ipv6 N/A
3. Configure the C-RP-Adv
interval.
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 PIM
common timers ."
Configuring a BSR
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.
Configuring a C-BSR
Configure C-BSRs on routers in the backbone network. When you configure a router as a C-BSR, be sure
to specify the IPv6 address of an IPv6 PIM-SM-enabled interface on the router. The BSR election process
is summarized as follows:
1. 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.
2. 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 a
tie exists 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, and 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, in order to prevent a maliciously configured host from masquerading as a BSR. You must
make the same configuration on all routers in the IPv6 PIM-SM domain. The following are typical BSR
spoofing cases and the corresponding preventive measures:
• 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.
• When an attacker controls a router in the network or when the network contains an illegal router,
the attacker can configure this router as a C-BSR and make it win BSR election to control the right