HP MSR2003 Configuration Manual page 256

priority as the RPF route. If the routes have the same priority, the router selects the IPv6 MBGP
route as the RPF route.
For more information about the route preference, see Layer 3—IP Routing Configuration
Guide.
If the router does not use the longest prefix match principle, the router selects the route that has
a higher priority as the RPF route. If the routes have the same priority, the router selects the IPv6
MBGP route as the RPF route.
The term "packet source "can mean different things in different situations:
For a packet that travels along the SPT from the multicast source to the receivers or the RP, the packet
•
source for RPF check is the multicast source.
For a packet that travels along the RPT from the RP to the receivers, the packet source for RPF check
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is the RP.
• For a packet that travels along the source-side RPT from the multicast source to the RP, the packet
source for RPF check is the RP.
For a bootstrap message from the BSR, the packet source for RPF check is the BSR.
•
For more information about the concepts of SPT, RPT, source-side RPT, RP, and BSR, see "Configuring IPv6
PIM."
RPF check implementation in IPv6 multicast
Implementing an RPF check on each received IPv6 multicast packet would heavily burden the router. The
use of an IPv6 multicast forwarding table is the solution to this issue. When the router creates an IPv6
multicast forwarding entry for an IPv6 multicast packet, it sets the RPF interface of the packet as the
incoming interface of the forwarding entry. After the router receives an IPv6 multicast packet, it searches
its IPv6 multicast forwarding table for a matching forwarding entry and examines the receiving interface:
If no match is found, the router first determines the RPF route back to the packet source. Then, it
•
creates a forwarding entry with the RPF interface as the incoming interface and performs one of the
following tasks:
If the interface that received the packet is the RPF interface, the RPF check succeeds and the
router forwards the packet out of all outgoing interfaces.
If the interface that received the packet is not the RPF interface, the RPF check fails and the router
discards the packet.
If a match is found and the matching forwarding entry contains the receiving interface, the router
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forwards the packet out of all outgoing interfaces.
If a match is found but the matching forwarding entry does not contain the receiving interface, the
•
router determines the RPF route back to the packet source. Then, the router performs one of the
following tasks:
If the RPF interface is the incoming interface, it means that the forwarding entry is correct but the
packet traveled along a wrong path. The router discards the packet.
If the RPF interface is not the incoming interface, it means that the forwarding entry has expired.
The router replaces the incoming interface with the RPF interface. If the interface that received
the packet is the RPF interface, the router forwards the packet out of all outgoing interfaces.
Otherwise, it discards the packet.
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