[ovs-discuss] MAC learning table does not always update

[Cheng Jin]

On Tue, Mar 3, 2015 at 3:03 PM, Ben Pfaff <blp at nicira.com> wrote:

> On Tue, Mar 03, 2015 at 12:25:20PM -0600, Cheng Jin wrote:
> > I have a problem with updating OVS' MAC learning table, when it is in the
> > 'standalone' mode running like a legacy Ethernet bridge.
> >
> > The switch has an entry to a destination, including the destination MAC
> > (say, 00:00:00:00:00:01), an output port (say, 1), VLAN, and Age.
> However,
> > the switch sometimes does not update the entry, when it receives a packet
> > from the same destination (still 00:00:00:00:00:01) but from a new
> incoming
> > port (say, 2). Does someone know what may cause this issue?
> >
> > The MAC learning table is supposed to be updated once receiving a packet.
> > Does OVS do some optimization to process the packets so that the learning
> > table may not get updated when the packet rate is high?
>
> The optimization that OVS does should only affect cases where a MAC
> would otherwise quickly bounce back and forth between a number of
> learned ports.
>
> Is there anything unusual in your setup?  Can you reproduce this with
> a simple setup?
>

We tried a simple setup which has only three switches forming a triangle
(VLAN set up to avoid loop), and two hosts connect with two "standalone"
switches.

The MAC learning table is allowed to stabilize (we send no traffic) and
then we send a packet from a source MAC that already exists in the MAC
table but which comes on another port than the one registered in the table.
We are checking how soon does the switch adapt. We don't do back and forth
changes often so the optimization should not happen.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://openvswitch.org/pipermail/ovs-discuss/attachments/20150304/362cbcc6/attachment-0002.html>