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

Michael Rasmussen mir at datanom.net
Sat Mar 9 15:30:44 CET 2013

On Sat, 09 Mar 2013 09:56:19 +0100 (CET)
Alexandre DERUMIER <aderumier at odiso.com> wrote:

> Some more infos about igmp queries.
> We can have only 1 igmp quierier on a vlan. If multiple quierier exist, an election mecanism exist, and the querier with lowest ip should win.
> So it's possible that a proxmox host, is the igmp quierier for your whole network. (including physical switches).
> I think it can be pretty bad, as if you have some host problem (network driver, bridge bug, iptable filter,...), it can break igmp response and 
> may cause potentential igmp snooping break.
> Also if you reboot the host which is the igmp quierier, a new election will occur.
> So disable igmp query on linux bridge should be disable by default. 
From what I have read about the IGMP implementation in Linux then igmp
quierier is optional and disabled by default since the task of acting
as quierier is normally an infrastructure task in which case you expect
the network components like switch or router to take care of this. This
is especially the case if the nearest switch is a stacked switch in a
larger network where you would expect the IGMP snooping to be carried
over the trunk port.

Therefore I always configure a dedicated switch on the infrastructure
to be the quierier on a specific vlan in which case you can add as many
proxmox host you like to an infrastructure and have multicast working
out of the box. This is the recommended setup by Cisco, Juniper and HP
(maybe also others recommend this but I have no experience with other
than the mentioned)

Attached are my configuration on a HP V1910 switch.

Michael Rasmussen

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