HP A5500 EI Switch Series, Руководство по настройке

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When performing an RPF check, a router searches its unicast routing table, MBGP routing table, and
multicast static routing table at the same time. The following describes the specific process:
1.
The router first chooses an optimal route from each of the unicast routing table, the MBGP routing
table, and the multicast static routing table:
{
The router automatically chooses an optimal unicast route by searching its unicast routing table
and 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. The
router considers the path along which the packet from the RPF neighbor arrived on the RPF
interface to be the shortest path that leads back to the source.
{
The router automatically chooses an optimal MBGP route by searching its 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.
{
The router automatically chooses an optimal multicast static route by searching its multicast
static routing table, using the IP address of the packet source as the destination address. The
corresponding routing entry explicitly defines the RPF interface and the RPF neighbor.
2.
The router selects one of these optimal routes as the RPF route. The following describes the selection
process:
{
If configured to use the longest match principle, the router selects the longest match route from
the three optimal routes. If the three routes have the same mask, the router selects the route with
the highest priority. If the three routes have the same priority, the router selects the RPF route
according to the sequence of multicast static route, MBGP route, and unicast route.
{
If not configured to use the longest match principle, the router selects the route with the highest
priority. If the three routes have the same priority, the router selects the RPF route according to
the sequence of multicast static route, MBGP route, and unicast route.
NOTE:
The
packet source means different things in different situations:
For a packet traveling along the shortest path tree (SPT) from the multicast source to the receivers or
the rendezvous point (RP), the packet source for RPF check is 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, the packet source for RPF check is the RP.
For a bootstrap message from the bootstrap router (BSR), the packet source for RPF check is the BSR.
For more information about the concepts of SPT, RPT, source-side RPT, RPT, and BSR, see the chapter
“PIM configuration.”
Implementation of RPF check in multicast
Implementing an RPF check on each received multicast data packet would be a big burden to the router.
The use of a multicast forwarding table is the solution to this issue. When creating a multicast routing
entry and a multicast forwarding entry for a 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) multicast packet, the router
first searches its multicast forwarding table:
1.
If the corresponding (S, G) entry does not exist in the multicast forwarding table, the packet
undergoes an RPF check. The router creates a multicast routing entry based on the relevant routing
information and adds the entry into the multicast forwarding table, with the RPF interface as the
incoming interface.