multicast traffic no longer working after reboot

Dennis Jacobfeuerborn

2014-07-31 15:24:07 UTC

Post by 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
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

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