To work around this expected network behavior, Neutron allocates a unique MAC address to each compute node that is used whenever traffic from a distributed virtual router leaves the node. The following screenshot shows the unique MAC addresses that have been allocated to the nodes in this demonstration:

Open vSwitch flow rules are used to rewrite the source MAC address of a packet as it leaves a router interface with the unique MAC address allocated to the respective host. In the following screenshot, a look at the flows on the provider bridge of compute02 demonstrates the rewriting of the non-unique qr interface MAC address with the unique MAC address assigned to compute02:

Likewise, when traffic comes in to a compute node that matches a local virtual machine instance's MAC address and segmentation ID, the source MAC address is rewritten from the unique source host MAC address to the local instance's gateway MAC address:

Because the Layer 2 header rewrites occur before traffic enters and after traffic leaves the virtual machine instance, the instance is unaware of the changes made to the frames and operates normally. The following section demonstrates this process in further detail.