[ovs-discuss] how can 2 ports in different bridge communicate?

ychen ychen103103 at 163.com
Mon Sep 29 11:00:19 UTC 2014


Ben:
      Thank you for your quick reponse, now I can communicate 2 VMs with GRE tunnel using just one bridge!
      The original purpose for connecting two bridges is that I want to develop QINQ in ovs, and I thought the QINQ topology should be like this:
     
      +-------+            
      |  VM   |
     +--------+
            |
            | p0(access)
      +---------------------+
      |       br0               |
      +---------------------+
                  |p1(trunk)
                  |
                  |p2(qinq)
      +---------------------+
      |       br1               |------eth0-------->to public internet
     +----------------------+


      p0: br0, access, tag=100
      p1: br0, trunk, trunks=100,200
      p2:br1, qinq, tag=2
      eth0:br1, trunk, trunks=2,3
     
      send:
      packet from p1, add tag 100; then packet come into p2, add tag 2;
     recv:
     packet from eth0, with outer tag 2 and inner tag 100; packet out from p2, strip tag 2; packet out from p1, strip tag 100;


     so now two bridges connected via port p1 and p2, that's similar to traditional network
     1. under this condition, do I still need patch port to connect two bridges?
     2. for developing QINQ in ovs, does this topology seems rational?








At 2014-09-29 11:11:28, "Ben Pfaff" <blp at nicira.com> wrote:
>On Mon, Sep 29, 2014 at 09:39:21AM +0800, ychen wrote:
>>   Thanks very much, the information really helps.
>>   What I am confused is about GRE  tunnel
>>   http://blog.scottlowe.org/2013/05/07/using-gre-tunnels-with-open-vswitch/
>>   In the above blog, each host uses two bridges, one for GRE, one for physical port 
>>   but there seems no patch port between 2 bridges.
>
>I think that the presence of two bridges in this configuration is a red
>herring.  The way that packets make it from the GRE tunnel into the
>second bridge in this scenario is the same way that packets make it from
>a GRE tunnel into a bridge when there is only one bridge.  If you are
>setting up a GRE tunnel with Open vSwitch for the first time, then it is
>probably easiest to just use one bridge (and keep the physical device
>off that bridge).
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