[ovs-discuss] in-band mode

Ben Pfaff blp at nicira.com
Mon Jul 8 16:21:05 UTC 2013


On Fri, Jul 05, 2013 at 01:58:41AM +0200, Andreas Brinner wrote:
> I was trying to cascadate an OpenFlow switch (Linksys with OpenWRT)
> behind an Open vSwitch like this:
> OF Switch (Linksys) <-> Open vSwitch <-> OF Controller
> 
> I configured in-band mode for the Open vSwitch and I can see the
> additional, hidden flow rules with ovs-appctl. But still the Linksys
> couldn't connect to the controller.
> 
> The reason was, that ARP requests from the Linksys were not
> forwarded to the controller.
> 
> So I had a look into the DESIGN paper and the in-band.c code. In the
> DESIGN guide the rules (d) and (e) are specified as follows:
>   (d) ARP replies to the next hop's MAC address.
>   (e) ARP requests from the next hop's MAC address.
> The exact same rules are set up by in-band.c and can be found in my
> flow table. So atleast everything seems consistent here.
> 
> Now my problem: these two rules should fire exactly in my case and
> should enable my Linksys to retrive the MAC address of the OF
> controller. At least if I understand the list of "supported"
> scenarios correctly:
>   - Between Switch and Remote.  This switch is between another
>     switch and the remote, and we want to allow the other
>     switch's traffic through.  This uses rules (d), (e), (h), and
>     (i).  It uses (b) and (c) indirectly in order to know the MAC
>     address for rules (d) and (e).
> 
> But for this to work, rule (d) would have to allow ARP _requests_ to
> the controler and (e) ARP _replies_ from the controller to pass! If
> I manually add these rules to the flow table, the Linksys
> successfully connects to the controller via the Open vSwitch.
> 
> Do I miss anything here?

Can you figure out why the flows set up by (d) and (e) aren't working
for you?  It sounds like they should.



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