HP 6125XLG R2306-HP 6125XLG Blade Switch IP Multicast Configuration Guide - Page 39

Configuring multicast routing and forwarding, Overview, RPF check mechanism, RPF check process

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Configuring multicast routing and forwarding Overview The following tables are involved in multicast routing and forwarding: • Multicast routing table of each multicast routing protocol, such as the PIM routing table. • General multicast routing table that summarizes multicast routing information generated by different multicast routing protocols. The multicast routing information from multicast sources to multicast groups are stored in a set of (S, G) routing entries. • Multicast forwarding table that guides multicast forwarding. The optimal routing entries in the multicast routing table are added to the multicast forwarding table. RPF check mechanism A multicast routing protocol uses Reverse path forwarding (RPF) check to ensure the multicast data delivery along the correct paths when the multicast routing protocol creates multicast routing entries based on the existing unicast routes or static multicast routes. RPF check also helps avoid data loops. A multicast routing protocol uses the following tables to perform an RPF check: • Unicast routing table-Contains unicast routing information. • Static multicast routing table-Contains RPF routes that are manually configured. Static multicast routing table is used for RPF check rather than multicast routing. RPF check process When performing an RPF check, the router searches its unicast routing table and static multicast routing table at the same time using the following process: 1. The router separately chooses an optimal route from the unicast routing table and the static multicast routing table: { The router looks up its unicast routing table by using the IP address of the packet source as the destination address, and automatically chooses an optimal unicast route. The outgoing interface of the route is the RPF interface and the next hop is the RPF neighbor. The router considers the path of the packet that the RPF interface receives from the RPF neighbor as the shortest path that leads back to the source. { The router looks up its static multicast routing table by using the IP address of the packet source as the source address, and automatically chooses an optimal static multicast route. The route explicitly defines the RPF interface and the RPF neighbor. 2. The router selects one of the two optimal routes as the RPF route according to the following principles: { If the router uses the longest prefix match principle, it selects the matching route as the RPF route. If the routes have the same mask, the router selects the route that has the highest priority as the RPF route. If the routes have the same priority, the router selects a route as the RPF route in the order of static multicast route and unicast route. 32

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32
Configuring multicast routing and forwarding
Overview
The following tables are involved in multicast routing and forwarding:
•
Multicast routing table of each multicast routing protocol, such as the PIM routing table.
•
General multicast routing table that summarizes multicast routing information generated by different
multicast routing protocols. The multicast routing information from multicast sources to multicast
groups are stored in a set of (S, G) routing entries.
•
Multicast forwarding table that guides multicast forwarding. The optimal routing entries in the
multicast routing table are added to the multicast forwarding table.
RPF check mechanism
A multicast routing protocol uses Reverse path forwarding (RPF) check to ensure the multicast data
delivery along the correct paths when the multicast routing protocol creates multicast routing entries
based on the existing unicast routes or static multicast routes. RPF check also helps avoid data loops.
A multicast routing protocol uses the following tables to perform an RPF check:
•
Unicast routing table
—Contains unicast routing information.
•
Static multicast routing table
—Contains RPF routes that are manually configured.
Static multicast routing table is
used for RPF check rather than multicast routing.
RPF check process
When performing an RPF check, the router searches its unicast routing table and static multicast routing
table at the same time using the following process:
1.
The router separately chooses an optimal route from the unicast routing table and the static
multicast routing table:
{
The router looks up its unicast routing table by using the IP address of the packet source as the
destination address, and automatically chooses an optimal unicast route. The outgoing
interface of the route is the RPF interface and the next hop is the RPF neighbor. The router
considers the path of the packet that the RPF interface receives from the RPF neighbor as the
shortest path that leads back to the source.
{
The router looks up its static multicast routing table by using the IP address of the packet source
as the source address, and automatically chooses an optimal static multicast route. The route
explicitly defines the RPF interface and the RPF neighbor.
2.
The router selects one of the two optimal routes as the RPF route according to the following
principles:
{
If the router uses the longest prefix match principle, it selects the matching route as the RPF route.
If the routes have the same mask, the router selects the route that has the highest priority as the
RPF route. If the routes have the same priority, the router selects a route as the RPF route in the
order of static multicast route and unicast route.