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its bootstrap messages. The BSR then floods the bootstrap messages to all IPv6 routers in the
network.
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 public network IPv6
PIM view or VPN instance
IPv6 PIM view.
pim ipv6
[
vpn-instance
vpn-instance-name
]
N/A
3.
Configure the C-RP-Adv
interval.
c-rp
advertisement-interval
interval
Optional.
60 seconds by default.
4.
Configure C-RP timeout
timer.
c-rp
holdtime
interval
Optional.
150 seconds by default.
For more information about the configuration of other timers in IPv6 PIM-SM, see "
."
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
You should 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 as follows:
•
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.
•
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 to assume itself to be the BSR.
Configuring a legal range of BSR addresses enables filtering of bootstrap messages based on the
address range, thereby preventing 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
describes the 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 to discard unwanted messages.
•
When an attacker controls a router on the network, the attacker can configure the router as a
C-BSR to win the BSR election. Through this router, the attacker controls the advertising of RP
