[ovs-discuss] OVS Multiple GRE tunnels

Jesse Gross jesse at nicira.com
Tue Dec 11 17:04:19 UTC 2012

On Mon, Dec 10, 2012 at 10:49 PM, Ahmed Talha Khan <auny87 at gmail.com> wrote:
> Hey,
> I have a few questions regarding the support of GRE tunnels in OVS.
> 1. I create a tunnel endpoint on an ovs-port with the gre options as defined
> in the manpages. Now i want to send mod-flow msgs from the controller which
> contain only the output action on that port. Will ovs append the transport
> tunnel header on it by itself even when i hve not specified the set-tunnel
> action?.


> 2. Is the tunneling support in question one, extensible in anyway? What if i
> want to add some extra headers or modify the tunnel headers?

Adding extra headers requires dataplane code changes.  It's possible
that you could modify existing headers by processing the packet again
after tunnel output but before the network device.

> 3. A tunnel endpoint is logically bounded to a physical interface which
> means that ovs will make that port a TEP as viewed by the hypervisor. Can i
> make multiple tunnels from the same TEP destined to multiple destination
> TEPs? Effectively meaning can i have multiple tunnels originating from the
> same port that i made in part 1?


> 4. What is the best possible way to create such tunnel between OVS and VMs.
> This is different from part 3 above as VMs will not have physical NICs. It
> more of a logical tunnel then actual tunnel between 2 physical hosts

You just need to bridge the VM to a tunnel.

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