Linux Bridge , vnet and VM --> how it all bind togather

SDN => software define network use software bridge to make thing happen ... all for the cloud


• We created a Linux bridge and added a physical NIC interface of the host.
• Then while creating a VM, we specified the Linux bridge to be used for virtual networking.
• The Virtual Machine Manager (libvirt GUI) did some behind-the-scene work
        to associate the Virtual NIC to the Linux bridge and in turn to the Physical NIC.
• We then observed how the VM’s virtual NIC is associated to the virtual tap interface on the host.
        And how the tap interface is added to the Linux bridge.
• This shows that the traffic will flow from the VM’s virtual NIC to the vnet0 tap interface,
        then onto the Linux bridge (virtual switch) which will send it out on the other virtual switch interface (eth0) on the host.

Example :

[root@host]# brctl show
bridge name     bridge id               STP enabled     interfaces
bridge0                8000.5cb90178da58       no              eth1
                                                        vnet1
                                                        vnet2
                                                        vnet4
bridge1               8000.fe54006d07b8       no              vnet3
bridge2                8000.5cb90178da50       no              eth0
                                                        vnet0
bridge3               8000.fe5400fdaa91       no              vnet5
virbr0          8000.52540055b76e       yes             virbr0-nic

Above example detail what bridge is define and which interface is connected to the bridge

To identify which vm the vnet is associated user need to check the MAC address on the vm interface and compare
it to the ifconfig -a on the host vnet#