On Thu, Aug 10, 2017 at 06:53:18PM +0000, Mark Michelson wrote:
> On Thu, Aug 10, 2017 at 1:14 PM Ben Pfaff <b...@ovn.org> wrote:
> > On Thu, Aug 10, 2017 at 02:41:30PM +0000, Mark Michelson wrote:
> > > I'm curious about the current behavior when ovn-controller originates a
> > > packet and transmits it over a link-local IPv6 multicast address. Will
> > the
> > > packet be delivered only to nodes on the same chassis, or can the packet
> > > also reach on-link nodes on other chassis?
> > When an OVN logical switch receives an Ethernet broadcast or multicast
> > packet from a given port, it forwards it to all of its other logical
> > switch ports, regardless of chassis. There are special cases for ARP
> > and IPv6 ND, to avoid forwarding them across chassis for known IP
> > addresses. I don't think that we have any special cases for IPv6
> > link-local multicast. Limiting these within a chassis would probably
> > require new mechanisms, because logical flows, by design, do not respect
> > physical boundaries.
> Interesting you mention IPv6 ND here. RAs fall under the umbrella of IPv6
> ND. So depending on how IPv6 ND is detected, it may be that RAs will be
> limited from being sent to other chassis. The interesting bit here is the
> "for known IP addresses" part. I'll take a closer look at the flows to see
> what that means. If the all-nodes link-local multicast address is one of
> these known IP addresses, then things might just work without having to do
> much extra.
My wording probably made it sound like there's more than there really
is. The ND support handles only one special case: when a VM sends a
neighbor solicitation for an IPv6 address's Ethernet address, the
logical switch responds with a neighbor advertisement that supplies that
Ethernet address. The ND support doesn't handle RAs.
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