[ovs-dev] [PATCH] Document issues with RSPAN and MAC learning.

[Keith Amidon]

Open vSwitch currently use the following key to indicate the VLAN on
which RSPANed packets will be copied:

        mirror.brname.pmname.output.vlan=vid

Would it make sense to disable MAC learning on each VLAN referenced by
such a key in the configuration?  In the case of an intermediate switch
on which no switch-local traffic needs to be copied this key would be
present to disable learning for the VLAN but there wouldn't be any
corresponding select key to indicate the source of data to be copied.

          --- Keith


On Mon, 2009-09-28 at 20:18 -0700, Ben Pfaff wrote:

> Looks good, but drop the blank line that it adds.  (For whatever
> reason it's considered bad style to have blank lines in troff
> input, so I've trying to follow that style in manpages as I
> continue to write them.)
> 
> Jesse Gross <jesse at nicira.com> writes:
> 
> > Bug #2118
> > ---
> >  vswitchd/ovs-vswitchd.conf.5.in |   10 +++++++++-
> >  1 files changed, 9 insertions(+), 1 deletions(-)
> >
> > diff --git a/vswitchd/ovs-vswitchd.conf.5.in b/vswitchd/ovs-vswitchd.conf.5.in
> > index 12fea6c..e7f0e2e 100644
> > --- a/vswitchd/ovs-vswitchd.conf.5.in
> > +++ b/vswitchd/ovs-vswitchd.conf.5.in
> > @@ -282,7 +282,15 @@ correctly pointed to port 1, with one that incorrectly points to port
> >  the end host to the Open vSwitch on port 2, instead of to the end host
> >  on port 1, disrupting connectivity.  If mirroring to a VLAN is desired
> >  in this scenario, then the physical switch must be replaced by one
> > -that learns Ethernet addresses on a per-VLAN basis.
> > +that learns Ethernet addresses on a per-VLAN basis.  In addition,
> > +learning should be disabled on the VLAN containing mirrored traffic.
> > +If this is not done then the intermediate switch will learn the MAC
> > +address of each end host from the mirrored traffic.  If packets being
> > +sent to that end host are also mirrored, then they will be dropped
> > +since the switch will attempt to send them out the input port.
> > +Disabling learning for the VLAN will cause the switch to correctly
> > +send the packet out all ports configured for that VLAN.
> > +
> >  .ST "Example"
> >  The following \fBovs\-vswitchd\fR configuration copies all frames received
> >  on \fBeth1\fR or \fBeth2\fR to \fBeth3\fR.
> 
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