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• When an attacker controls a router in the network 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 a router is configured as a C-BSR, it automatically
floods the network with bootstrap messages. Because a bootstrap message has a TTL 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.
These preventive measures can partially protect the security of BSRs in a network. However, if an attacker
controls a legal BSR, the problem will still occur.
Because a large amount of information needs to be exchanged between a BSR and the other devices in
the PIM-SM domain, a relatively large bandwidth should be provided between the C-BSRs and the other
devices in the PIM-SM domain.
For C-BSRs interconnected via a tunnel, multicast static routes need to be configured to make sure that the
next hop to a C-BSR is a tunnel interface. For more information about multicast static routes, see
"Configuring multicast routing and forwarding."
To
configure a C-BSR:
Ste
Remarks
1. Enter system view.
system-view N/A
2. Enter PIM view.
pim N/A
3. Configure an interface as a
C-BSR.
c-bsr interface-type
interface-number [ hash-length
[ priority ] ]
No C-BSRs are configured by
default.
4. Configure a legal BSR
address range.
bsr-policy acl-number
Optional.
No restrictions on BSR address
range by default.
Configuring a PIM domain border
As the administrative core of a PIM-SM domain, the BSR sends the collected RP-set information in the form
of bootstrap messages to all routers in the PIM-SM domain.
A PIM domain border is a bootstrap message boundary. Each BSR has its specific service scope. A
number of PIM domain border interfaces partition a network into different PIM-SM domains. Bootstrap
messages cannot cross a domain border in either direction.
Perform the following configuration on routers that you want to configure as a PIM domain border.
To configure a PIM domain border:
Ste
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