Multicast problems

Daniel Eischen deischen at
Mon Jun 18 12:37:31 UTC 2007

On Mon, 18 Jun 2007, Bruce M. Simpson wrote:
> Other folks reported issues with the new code. As you're probably aware, ipv4 
> multicast group memberships must be bound to an interface. When they are not, 
> the interface selected as the source for the IGMP join uses a routing table 
> lookup on the group.
> The newer code changed to perform this lookup by interface index as well as 
> by address, as interfaces used for ipv4 multicast traffic are generally 
> assumed to have a protocol-level address.

What happens when you join a group without an interface (INADDR_ANY)?
Assume there is no route for the multicast group.  Does the new code
select the interface that the default route is on?

This is the behavior we expect to see and what occurs on other OSs.


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