[openib-general] IPv6 All Router Multicast Group

[Hal Rosenstock]

Roland Dreier wrote:
>     Hal> I would expect end nodes joining the all routers group to at
>     Hal> least be listening to router advertisements so just joining
>     Hal> send only doesn't make sense. If the node is behaving as a
>     Hal> router, I would expect a full join as they would need to both
>     Hal> send and receive.
> 
> Doesn't IPv6 autoconfiguration work by having a node send a
> router solicit message to the all-routers group (without needing to
> listen to the all-routers group)?

Routers send router advertisements periodically. If a hosts does not
receive any router advertisements in some time period, it will solicit 
for routers (send a router solicitation message) some number of times.
So maybe IPv6 unicast routers don't need to receive on this group (hosts
definitely do).

For IGMP, I think both hosts and routers need to both send and receive
yet we see a send only join for this group.

The same thing appears to be occuring in these IPv4 (all routers and IGMP).

-- Hal