HP A8800 Configuration Manual page 345

The router automatically chooses an optimal IPv6 MBGP route by searching its IPv6 MBGP
routing table, using the IP address of the "packet source" as the destination address. The
outgoing interface in the corresponding routing entry is the RPF interface and the next hop is the
RPF neighbor.
2. Then, the router selects one from the two optimal routes as the RPF route. The selection process is
as follows:
If configured to use the longest match principle, the router selects the longest match route from
the two. If these two routes have the same mask, the router selects the route with the highest
priority. If the two routes have the same priority, the router selects the RPF route according to the
sequence of IPv6 MBGP route and IPv6 unicast route.
If not configured to use the longest match principle, the router selects the route with the highest
priority. If the two routes have the same priority, the router selects the RPF route according to the
sequence of IPv6 MBGP route and IPv6 unicast route.
The above-mentioned "packet source" can mean different things in different situations:
For a packet traveling along the shortest path tree (SPT) from the multicast source to the receiver
•
hosts or the source-based tree from the multicast source to the rendezvous point (RP), "packet
source" means the multicast source.
• For a packet traveling along the rendezvous point tree (RPT) from the RP to the receivers, or along
the source-side RPT from the multicast source to the RP, "packet source" means the RP.
For a bootstrap message from the bootstrap router (BSR), "packet source" means the BSR.
•
For more information about the concepts of SPT, RPT, source-side RPT, RP, and BSR, see
PIM."
RPF check implementation in IPv6 multicast forwarding
Implementing an RPF check on each received IPv6 multicast data packet would bring a big burden to 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. Upon receiving an (S, G) IPv6
multicast packet, the router first searches its IPv6 multicast forwarding table:
1. If no corresponding (S, G) entry exists in the multicast forwarding table, the packet undergoes an
RPF check. The router creates an (S, G) entry based on the relevant routing information and using
the RPF interface as the incoming interface, and adds the entry into the IPv6 multicast forwarding
table.
If the interface that received the packet is the RPF interface, the RPF check is successful and the
router forwards the packet out of all the outgoing interfaces.
If the interface that received the packet is not the RPF interface, the RPF check fails and the router
discards the packet.
2. If the corresponding (S, G) entry exists, and the interface that received the packet is the incoming
interface in the IPv6 multicast forwarding table, the router forwards the packet out of all the
outgoing interfaces.
3. If the corresponding (S, G) entry exists, but the interface that received the packet is not the
incoming interface in the IPv6 multicast forwarding table, the packet is subject to an RPF check.
If the result of the RPF check shows that the RPF interface is the incoming interface of the existing
(S, G) entry, this means that the (S, G) entry is correct but the packet arrived from a wrong path
and is to be discarded.
If the result of the RPF check shows that the RPF interface is not the incoming interface of the
existing (S, G) entry, this means that the (S, G) entry is no longer valid. The router replaces the
333
"Configuring IPv6