Hi Lars,

I had a similar question recently, the answer I got is the following:

"A patch port is not the same as a veth pair. It is not used to "send" and
"receive" traffic. When we process an upcall and have to determine what
actions
to perform on a packet, a patch_port is is basically an equivalent to
"continue
processing openflow flows on this other bridge"

The following blog post goes into some detail on the topic:
https://arthurchiao.art/blog/ovs-deep-dive-4-patch-port/

I hope this helps.

On Thu, Jun 2, 2022 at 11:03 PM Lars Kellogg-Stedman <[email protected]>
wrote:

> Given two OVS bridges connected by a patch port, I would like to run
> `tcpdump` on either of the patch interfaces to see traffic passing between
> the switches. The command runs without error, but doesn't see any of the
> expected traffic.
>
> The basic configuration looks something like this:
>
>     ovs-vsctl add-br br0
>     ovs-vsctl add-br br1
>     ovs-vsctl add-port br0 patch-br1 -- set interface patch-br1 type=patch
> options:peer=patch-br0
>     ovs-vsctl add-port br1 patch-br0 -- set interface patch-br0 type=patch
> options:peer=patch-br1
>
> I want to run `ovs-tcpdump -i patch-br1 -n`, but it doesn't seem to work.
> I see the same behavior if I manually set up a mirror port and run
> `tcpdump` on it.
>
> Is it possible to set up mirrors for patch ports?
>
>
> --
> Lars Kellogg-Stedman <[email protected]>
>
> _______________________________________________
> discuss mailing list
> [email protected]
> https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
>


-- 

Lewis Denny, RHCE

OpenStack

Software Maintenance Engineer

Red Hat APAC <https://www.redhat.com>
<https://www.redhat.com>
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