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I've created a virtual machine (Centos 6.0) using QEMU/KVM, which is also running on a Centos 6.0. The virtual machine is configured to have two NICs. The first NIC is using a bridged network (eth0 of the host) and the second NIC is also using a bridged network (eth1). The interface eth1 of the host is receiving mirrored traffic from a cisco switch. When I do a tcpdump -i eth1 from the host I can see the traffic. I would expect to see the same traffic in my virtual machine (because of the bridge) but it is not the case.

Is there a special config that I'm not aware of?

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I finally found a solution to my problem. Setting the ageingtime of the bridge to 0 will make your bridge acting like a hub and you'll see the mirrored traffic from inside your VM (or any virtual machines connected to that bridge)

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