[ovs-discuss] Connecting multiple bridges in full mesh

[Scott Lowe]

Please see my response below.


> On Apr 7, 2016, at 10:29 AM, Eugene L. Vorokov <vel at pidarasy.org> wrote:
> 
> Hi guys,
> 
> I'm trying to setup L2 network using OpenVSwitch. There are 3 hosts
> with openvswitch running on them, each host is connected to the
> internet and has some local network behind it, the goal is to unite
> all those local networks on L2 level.
> 
> I've set up vxlan tunnels between 3 openvswitch hosts, but it seems
> like fully meshed topology (connecting 1-2, 2-3 and 1-3) leads to
> network loop, and everything stops working. If I only connect say 1-2
> and 2-3, so that topology is tree-like, everything works, but packets
> from 1 to 3 travel long way through 2, which is not what I need - they
> all are connected to the same Internet and such long path makes no
> sense.
> 
> Is there a way to setup openvswitch to support fully meshed topology?
> What I need is that each host in L2 network could reach any other host
> in that network via the fastest possible path.
> 
> For example, it would be fine if openvswitch would deny packet
> forwading between two vxlan ports, so that packets can only travel
> between two directly connected openvswitch hosts. Can this be set up
> somehow?


Yes. Enable STP on the OVS bridges, as described here:

<http://blog.scottlowe.org/2013/11/22/an-update-on-using-gre-tunnels-with-open-vswitch/>

Although the blog post talks about GRE tunnels, it's also applicable to VXLAN/STT/Geneve tunnels as well.

Be aware this is not without its drawbacks. Any time the topology changes STP will run again, which may cause undesirable delays in traffic forwarding/processing.

-- 
Scott