[ovs-discuss] packet loss in RSPAN trafic

Philippe Gautier p.gautier.philippe at gmail.com
Mon Feb 2 23:08:30 UTC 2015


 ip neigh show
192.168.42.151 dev br0 lladdr c0:3f:d5:60:3c:67 PERMANENT
192.168.42.2 dev br0 lladdr 7c:03:d8:81:2a:94 PERMANENT

Same observations with static arp entries. I tried to export traffic to
different ip address. I do not think it is related to arp table because my
gateway is 192.168.42.2. If gre traffic was dropped because of arp latency
real should have also be dropped ...



2015-02-01 22:46 GMT+01:00 Ben Pfaff <blp at nicira.com>:

> 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?
>
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