3com S7906E 설치 설명서

 

1-2 

An IPv6 multicast routing protocol relies on the existing IPv6 unicast routing information or IPv6 MBGP 

routes in creating IPv6 multicast routing entries. When creating IPv6 multicast routing table entries, an 

IPv6 multicast routing protocol uses the reverse path forwarding (RPF) check mechanism to ensure 

IPv6 multicast data delivery along the correct path. In addition, the RPF check mechanism also helps 

avoid data loops caused by various reasons.  

The basis for an RPF check is an IPv6 unicast route or an IPv6 MBGP route.  

An IPv6 unicast routing table contains the shortest path to each destination subnet; 

An IPv6 MBGP routing table contains IPv6 multicast routing information.  

When performing an RPF check, a router searches its IPv6 unicast routing table and IPv6 MBGP 

routing table at the same time. The specific process is as follows:  

The router first chooses an optimal route from the IPv6 unicast routing table and IPv6 MBGP routing 

table respectively:  

The router searches its IPv6 unicast routing table using the IPv6 address of the “packet source” as the 

destination address and automatically selects the optimal route as the RPF route. 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 IPv6 multicast 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 IPv6 MBGP route by searching its MBGP routing table, 

using the IPv6 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.  

Then, the router selects one from these 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 prefix length, the router selects the route with a higher priority; if these 

two 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 two routes have the same priority, the router selects the IPv6 MBGP route as the RPF route.