The way you're setting up your route is going to result in an infinite loop.
I'd suggest you use tap networking to do this. ** Changed in: qemu Status: New => Invalid -- Routing net multicast socket over loopback make Ethernet broadcast bounce back to VM. https://bugs.launchpad.net/bugs/533610 You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. Status in QEMU: Invalid Bug description: How to reproduce: Host commands: ip link set dev lo up ip addr add 127.0.0.1/8 dev lo ip route add 230.0.0.0/24 dev lo qemu-system-x86_64 --kernel bzImage --initrd initrd.gz -net nic,model=e1000,vlan=0,macaddr=52:54:00:00:00:01 -net socket,vlan=0,mcast=230.0.0.1:1234 -net nic,model=e1000,vlan=1,macaddr=52:54:00:00:00:02 -net socket,vlan=1,mcast=230.0.0.2:1234 In any of the VM: ip link set dev eth0 up ip link set dev eth2 up brctl addbr br0 brctl addif br0 eth0 brctl addif br0 eth2 brctl stp br0 on ip link set dev br0 up As soon as the bridge is up, you will get messages about eth0 and eth2 receiving their own packets from the bridge, then, be prepared for a packet/message storm as it grow infinitly until you end Qemu or probably have the guest's kernel hang.