[ovs-discuss] Question concerning GRE-encapsulated traffic *in* OpenStack provider VLAN network

Loschwitz,Martin Gerhard Martin.Loschwitz at drei.com
Tue Jul 7 08:47:36 UTC 2020


Dear Ben,

> Am 06.07.2020 um 21:44 schrieb Ben Pfaff <blp at ovn.org>:
> 
> On Fri, Jun 26, 2020 at 10:10:47AM +0000, Loschwitz,Martin Gerhard wrote:
>> Folks,
>> 
>> I’m contacting you to find out if a behaviour I see is expected behaviour or actual misdemeanour in Open vSwitch and/or OVN. I have an OpenStack setup here that uses OVN. I have configured several VLAN-based provider networks. What I want to do is use a GRE-tunnel *inside* one of these VLAN networks. On the target compute node, I see that traffic enters the physical host but is not forwarded to the bridge to which the VM is connected. I can see that the flows for that are missing in the flow table.
>> 
>> I fully understand that OVN supports Geneve only, but in this case, I want my *tenants* to be able to use GRE encapsulation in a provider network. Is this supposed to work and this is either a bug or a misconfiguration? And if it is not expected to work, what are possible alternatives?
> 
> I'm surprised this doesn't work.  I'd expect it to work.  At a guess,
> I'd suspect MTU issues, especially if you see that it sometimes works
> for connection setup.


Alright, so the most important information for me is that this should be working in theory. I will have a close look at MTU settings, thank you for the pointer.

Best regards
Martin


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