[ovs-discuss] [OVN] Should we tunnel traffic on localnet switches?

Daniel Alvarez dalvarez at redhat.com
Mon Feb 15 21:20:15 UTC 2021


Thanks Frode for your answer

> On 15 Feb 2021, at 20:32, Frode Nordahl <frode.nordahl at canonical.com> wrote:
> 
> On Mon, Feb 15, 2021 at 2:52 PM Daniel Alvarez Sanchez
> <dalvarez at redhat.com> wrote:
>> Recently we found out that due to a misconfiguration of the OVN bridge mappings, traffic that should be sent out to an external bridge was tunneled to the destination. Since the traffic was working, it took a while to spot the misconfiguration.
>> While this can be ok as it keeps everything functional, it can have an impact in the throughput and the overall performance. The intent of this email is to gather feedback as to whether we should keep this behavior or rather, drop the traffic and log the misconfiguration issue (like patch-port is missing, review the bridge mappings configuration?).
> 
> This is a feature. The fact that OVN does not require all chassis in
> the network to have external connectivity gives it a higher degree of
> flexibility when compared to other solutions.
> 
> If you operate OVN as an overlay on top of a L3-only CLOS fabric
> without EVPN it is required functionality. It allows you to tunnel N/S
> traffic to chassis in the physical vicinity of the data center border
> routers and avoid spanning a shared L2 across your DC fabric.

Right, I see this use case.

> OVN used to log the configuration excessively [0], and since then it
> has luckily been squelched into a single log message [1].
> 
> If you are suggesting this may be a source of supportability issues in
> case one has missed the one log message, perhaps we need some way of
> making this state observable through a call to `ovn-appctl` or
> something similar?

I think this could definitely help.
> 
> 0: https://bugs.launchpad.net/ubuntu/+source/ovn/+bug/1865127
> 1: https://patchwork.ozlabs.org/project/openvswitch/patch/20200519155816.24508-3-ihrachys@redhat.com/
> 
> -- 
> Frode Nordahl
> 
>> Looking forward to hearing from you.
>> Thanks a lot,
>> daniel
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