HP A6600 Configuration Manual page 274

The router selects one of these optimal routes as the RPF route. The selection process is as follows:
2.
If configured to use the longest match principle, the router selects the longest match route from
the two. If these routes have the same prefix length, the router selects the route with a higher
priority. If these routes have the same priority, the router selects the IPv6 MBGP route as the RPF
route.
If not configured to use the longest match principle, the router selects the route with a higher
priority. If these 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 traveling 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 traveling along the RPT from the RP to the receivers, or 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
PIM."
Implementing RPF check in IPv6 multicast
Implementing an RPF check on each received IPv6 multicast data packet would heavily burden the router.
The use of an IPv6 multicast forwarding table is the solution to this issue. When creating an IPv6 multicast
routing entry and an IPv6 multicast forwarding entry for an IPv6 multicast packet, the router sets the RPF
interface of the packet as the incoming interface of the (S, G) entry. After receiving an (S, G) IPv6
multicast packet, the router first searches its IPv6 multicast forwarding table:
If the corresponding (S, G) entry does not exist in the IPv6 multicast forwarding table, the packet
1.
undergoes an RPF check. The router creates an IPv6 multicast routing entry based on the relevant
routing information and installs the entry into the IPv6 multicast forwarding table, with the RPF
interface as the incoming interface.
If the interface on which the packet arrived is the RPF interface, the RPF check succeeds and the
•
router forwards the packet to all the outgoing interfaces.
• If the interface on which the packet arrived is not the RPF interface, the RPF check fails and the router
discards the packet.
If the corresponding (S, G) entry exists, and the interface on which the packet actually arrived is the
2.
incoming interface, the router forwards the packet to all the outgoing interfaces.
If the corresponding (S, G) entry exists, but the interface on which the packet actually arrived is not
3.
the incoming interface in the IPv6 multicast forwarding table, the IPv6 multicast packet undergoes an
RPF check.
If the RPF interface is the incoming interface of the (S, G) entry, this means the (S, G) entry is correct
•
but the packet arrived from a wrong path. The packet will be discarded.
If the RPF interface is not the incoming interface, this means that the (S, G) entry has expired, and
•
router replaces the incoming interface with the RPF interface. If the interface on which the packet
arrived is the RPF interface, the router forwards the packet to all the outgoing interfaces. Otherwise it
discards the packet.
Assume that IPv6 unicast routes are available in the network, IPv6 MBGP is not configured, and IPv6
multicast packets travel along the SPT from the multicast source to the receivers, as shown in
The IPv6 multicast forwarding table on Router C contains the (S, G) entry, with POS 5/0/0/1 as the RPF
interface.
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"Configuring IPv6
Figure 75.