When using Bridged mode, all of the guest virtual machines appear within the same subnet as the host physical machine. All other physical machines on the same physical network are aware of the virtual machines, and can access the virtual machines. Bridging operates on Layer 2 of the OSI networking model.
Figure 17.2. Virtual network switch in bridged mode
It is possible to use multiple physical interfaces on the hypervisor by joining them together with a bond. The bond is then added to a bridge and then guest virtual machines are added onto the bridge as well. However, the bonding driver has several modes of operation, and only a few of these modes work with a bridge where virtual guest machines are in use.
When using bridged mode, the only bonding modes that should be used with a guest virtual machine are Mode 1, Mode 2, and Mode 4. Using modes 0, 3, 5, or 6 is likely to cause the connection to fail. Also note that Media-Independent Interface (MII) monitoring should be used to monitor bonding modes, as Address Resolution Protocol (ARP) monitoring does not work.