Hi All, I am new to GRE tunneling in OVS. I tried the below example http://linuxmantra.com/2013/08/gre-tunneling-with-open-vswitch.html and I was able to establish the tunnel between the two VMs on two different physical machines.
This link talks about creating isolated bridges br0 and br2 but I was able to achieve it with a single bridge br2. Now I want to understand the packet flow of how the actual communication happens when VM1 pings VM2. 1. Data from VM1 reaches br2 through the tap interface. At this point, the ARP entry is not learnt, so br2 broadcasts the packets and thus the packet reaches gre0 interface on br2. 2. Packet is encapsulated with GRE header. 3. Now, how this packet reaches br0 and leaves the host machine from eth0 is not clear. Who picks the encapsulated packet ? Is it the OVS GRE kernel module ? If yes, then after the packet is encapsulated, is the route for remote host applied ? 4. Similarly when the packet reaches the destination host machine's br0, is it the kernel module that checks GRE header and handsover it to gre0 interface of br0 If its the kernel module doing all the wonders, how does it fetches the packets. DOes this module takes over the linux networking stack. ? It would be great help if anybody can explain me the flow. Thanks _______________________________________________ discuss mailing list discuss@openvswitch.org http://openvswitch.org/mailman/listinfo/discuss
