[ovs-discuss] packet loss in RSPAN trafic

[Ben Pfaff]

On Sat, Jan 31, 2015 at 03:41:13PM +0100, Philippe Gautier wrote:
> I detect packet loss when I analyse GRE traffic sended by RSPAN. Is there a
> default sampling parameter when configuring port mirroring ?

No, mirroring should copy all packets.

> Test platform and scenario:
> 
> Two KVM virtual hosts (port internet2, internet3) hosted on a physical host
> (port br0 and eth0). Trafic is sended through the gre interface to a remote
> host. The gre trafic is sended through eth0 physical interface.
> 
> When I generate a trafic between a vm and an internet host (In my case
> google server) I capture real and RSPAN trafic on eth0 interface.

It looks like the first packet is getting mirrored but a number of
packets after that are getting dropped, and that then after some time
the mirroring picks up again.  I wonder whether this is caused by ARP.
I believe that one valid way to do ARP is to queue the first packet to a
destination while waiting for an ARP response but drop later packets to
that destination until the ARP response arrives.  That would explain
this behavior.  So: does it help to add a static ARP entry for your
tunnel destination?