Some update on this:

I've created an identical virtualized environment an a different machine, and 
here the broadcast massages get forwarded to the guests. Only difference is the 
hardware.

So could it really be the hw with the brand NIC? (Dell PowerEdge T110 II / 
Intel 82574L Gigabit)


Thanks,
Andras


Begin forwarded message:

Date: Thu, 31 Jul 2014 08:17:31 +0200
From: Andras Horvath <[email protected]>
To: [email protected]
Subject: kvm bridge broadcast traffic


Hi Everyone,

I've run into a strange problem that I am not able to track down in the last 3 
days. Could someone kindly help and give directions?

On my 6.5 x64 system my bridged KVM guests (several kind of Windows and many 
kind of Linux guests) do not get the broadcast messages. Every network packets 
reach them from the subnet except broadcast and multicast messages. How can 
that be?

In kernel the bridge filter by iptables is turned off - turning on STP does not 
help - enabling promisc mode in interface does not help either.

Running tcpdump on host shows that the broadcast reaches the interface from a 
different computer on the subnet, but does not get in the guest. I ran tcpdump 
on the Linux guests and wireshark on the Windows ones. Testing the same with 
VirtualBox on a different computer, tcpdump and wireshark shows the broadcast 
packets.

What is weird that every network packets reach my guests in KVM except the 
broadcast ones.


Any help appreciated.

Thanks,
Andras

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