[ovs-discuss] double the encap

Jesse Gross jesse at nicira.com
Tue May 8 19:52:58 UTC 2012

On Tue, May 8, 2012 at 10:32 AM, Brandon Heller <brandonh at stanford.edu> wrote:
> On Tue, May 8, 2012 at 8:22 AM, Jesse Gross <jesse at nicira.com> wrote:
>> On Mon, May 7, 2012 at 6:48 PM, Brandon Heller <brandonh at stanford.edu>
>> wrote:
>> > I'd like to configure OVS using OpenFlow+Nicira extensions to push two
>> > VLAN
>> > tags, to load-balance at higher levels of a multi-rooted tree on
>> > physical
>> > switches that only support OpenFlow 1.0 in firmware and so don't support
>> > ECMP.  Double-stacked VLANs aren't strictly necessary; double IP-in-IP
>> > or
>> > VLAN + IP-in-IP would probably work too.
>> >
>> > One possibility may be to use a nicira_header to add a VLAN header with
>> > OFPAT_SET_VLAN_VID and then output to NXAST_RESUBMIT.   The resubmit
>> > match
>> > would then need to encap a VLAN the next time rather than set it, and I
>> > don't see an action for that other than maybe tunneling.
>> Resubmitting won't help since it doesn't change the action - the
>> OpenFlow 1.0 action will just set it the second time.  Internally OVS
>> has the ability to push multiple tags but that's not exposed to the
>> outside.
> Time to expose it, then.  Can you provide a pointer to the code section and
> private action?   Thanks.

Newer versions of OpenFlow change this into push/pop semantics so that
should solve your problem and would be the best direction to go.
There was some discussion and work around QinQ on the mailing list a
while ago so you might want to search and see if there is something
that you can use as a starting point.

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