Manually edit /etc/sysconfig/network, changing the "GATEWAYDEV" to your bridge

Virtualized bridged networking with MacVTap

Another alternative to using a bridge to enable a KVM guest to communicate externally is to use the Linux MacVTap driver. Macvtap is essentially a combination of the MacVLAN driver and a Tap device. Each virtual NIC has its own MAC address different from the physical interface's MAC address. Frames from or to the virtual interface are mapped to the physical interface called lower interface. MacVLAN allows you to have multiple Ethernet MAC addresses on one NIC. If you enable bridge mode, all virtual NICs attached to the same host can see each other.

Note: The guests can talk to each other. But the host cannot talk with the guests.

A MacVTap interface to be used within KVM can be created as following making a resource xml file (macvtap0-def.xml):

  <forward mode="bridge">
    <interface dev="btbond1"/>

Then you can set it up issuing:

virsh net-define macvtap0-def.xml
virsh net-autostart macvtap0
virsh net-start macvtap0

Attach the new NIC device to the guest

virsh attach-interface --domain <guest name> --type network --source macvtap0 --model virtio --config --live

The same cna be achievable using the virt-manager GUI on defining the network for the Guest VM: