multicast traffic no longer working after reboot

multicast traffic no longer working after reboot

[Dennis Jacobfeuerborn]

Hi,
today a couple of Hypervisors got restarted due to a power outage. While
the systems and the VMs on the are running fine multicast traffic
between the guests is no longer working.

I generate multicast udp packet using iperf in the guest and check on
the host using tcpdump:

tcpdump vnet0 => multicast packets are visible
tcpdump vlanbr8 => multicast packets are visible
tcpdump em1.8 => no multicast packets visible

vlanbr8 is the bridge, vnet0 the interface of the guest and em1.8 the
physical interface for vlan 8.

I compared the settings in /sys/class/net/vlanbr8/bridge/multicast_*
with a system where multicast works fine and see no differences. brctl
showstp also shows "mc router" to be 1 for both interfaces and the
bridge. All settings in /proc/sys/net/bridge/* are 0.

Any ideas why the bridge doesn't seem to forward multicast packets?
iperf with unicast udp also works fine so it's just multicast that is
the problem.

Regards,
  Dennis

Re: multicast traffic no longer working after reboot

[Dennis Jacobfeuerborn]

On 31.07.2014 15:22, Dennis Jacobfeuerborn wrote:
> Hi,
> today a couple of Hypervisors got restarted due to a power outage. While
> the systems and the VMs on the are running fine multicast traffic
> between the guests is no longer working.
> 
> I generate multicast udp packet using iperf in the guest and check on
> the host using tcpdump:
> 
> tcpdump vnet0 => multicast packets are visible
> tcpdump vlanbr8 => multicast packets are visible
> tcpdump em1.8 => no multicast packets visible
> 
> vlanbr8 is the bridge, vnet0 the interface of the guest and em1.8 the
> physical interface for vlan 8.
> 
> I compared the settings in /sys/class/net/vlanbr8/bridge/multicast_*
> with a system where multicast works fine and see no differences. brctl
> showstp also shows "mc router" to be 1 for both interfaces and the
> bridge. All settings in /proc/sys/net/bridge/* are 0.
> 
> Any ideas why the bridge doesn't seem to forward multicast packets?
> iperf with unicast udp also works fine so it's just multicast that is
> the problem.
> 
> Regards,
>   Dennis
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I did some further testing and strangely enough after booting the HV and
the guest things work as expected but after 2-3 minutes I suddenly don't
see the the packets anymore on em1.8. This is really bizarre behavior.

Regards,
  Dennis