[pve-devel] corosync, multicast problem because of vmbr multicast_snooping enabled

Michael Rasmussen mir at datanom.net
Sun Mar 10 11:05:49 CET 2013

On Sun, 10 Mar 2013 10:41:53 +0100 (CET)
Alexandre DERUMIER <aderumier at odiso.com> wrote:

> So, I don't known for HP switchs, but for Cisco switches it seem to break the election of igmp.
Some thoughts:
1) You have an aggregation spanning over two switches, I only use one
2) The switch is up before the pve hosts and maybe HP switches, given
the are configured to be querier, disable election and forces querier
state because I never see any querying on my network coming from the
switch. It is only the pve hosts which sends out queries.
3) If none of your Cisco switches are configured as querier they use
simple election to determine querier
4) When I had not configured my switch as querier I seem to recall a
broken multicast on the vlan too.

Some tests you can performe:
1) Configure your switches to always have numerical lower IP than any
hosts on the same vlan
2) Designate one or both of your switches as querier

If both of your tests gives a successful result I think the conclusion
must be that the linux bridge in some way brakes the election since
when you start your hosts one of your switches must be the querier but
after some time the querier changes to one of your hosts presumably
because your switches are having a numerical higher IP than one or
all of your pve hosts.

> Maybe my problem was that my proxmox host was the igmp quierer, and when I have shutted it down, no other igmp quierer have worked, and snooping have blocked all mutlticast address.
or maybe
"Multicast routers send host-query messages periodically to refresh
their knowledge of memberships present on their networks. If, after
some number of queries, the Cisco IOS software discovers that no local
hosts are members of a multicast group, the software stops forwarding
onto the local network multicast packets from remote origins for that
group and sends a prune message upstream toward the source."

PS. Are your mail client broken because it removes the List-Id from
your replies in which case other mailers will reply only to you when
replying if you forget to say 'reply to all'.

Michael Rasmussen

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		-- Arman de Caillavet, 1913
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