Well, the packet should already be getting delivered to PIM, since pimd
would be listening to the appropriate link-local multicast address
anyway.

The only real example I've seen where this is needed is for IGMP v1,
where hosts send their membership reports to the group(s) of which they
are a member.  Most hardware-based (ie, ASIC-based) routers these days
won't see the report, since the router is not a member of the group (and
having the router listen to every possible group is not feasible).

One should note that almost all modern routing protocols (even IGMP v2)
mandate that their packets be sent with the Router Alert option set.



On Mon, 23 Jul 2001 itojun@iijlab.net wrote:

<snip>
> 	many of multicast routing daemons (like PIM) needs to inspect it.
> 	will you implement PIM as kernel module? :-p

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