[ovs-dev] [PATCH 2/5] datapath: Add 'patch' vport.

Jesse Gross jesse at nicira.com
Tue May 18 20:35:05 UTC 2010


On Tue, May 18, 2010 at 9:58 AM, Ben Pfaff <blp at nicira.com> wrote:

> On Mon, May 17, 2010 at 07:24:45PM -0700, Jesse Gross wrote:
> > Adds a new 'patch' vport that acts like a virtual patch cable to
> > connect together two datapaths.
>
> Looks good to me.
>
> Is there any value in a "patch" vport having a MAC address?  Since it's
> not a network device there's no way to configure an IP address on it, so
> can the MAC ever get used for anything?  (Actually I guess the same
> question applies to GRE vports.  I see that Ian has the same question.)
>

The situation is a bit different from GRE since GRE uses the MAC for path
MTU discovery.  The only thing that 'patch' uses the MAC address for is to
make it look more like a real Ethernet device.  The MAC is reported over
OpenFlow and it is conceivable that a controller could use it as a way to
identify a port.  This approach will break on Xen but generally speaking, it
makes me a bit nervous to have non-unique MAC addresses.
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