[ovs-discuss] question about the OVS-OFCTL

terryxing xingtianyi at gmail.com
Tue Nov 12 07:23:36 UTC 2013


Thanks Ben,

I actually thought about using the NORMAL as the output action in OVS CLI
but It seems like the syntax  is not correct.  About the last part of you
answer, I can set the action as NORMAL, mod_nw_dst, NORMAL, thus, the last
NORMAL means the OVS will behave like a L2/L3 normal switch to help me to
find where the packet should be forwarded, right ?

What do you mean by short-lived ? How long it can last and can I save the
flowtable ?

Thanks for your kind reply, I will try that tomorrow.


On Mon, Nov 11, 2013 at 9:57 PM, Ben Pfaff <blp at nicira.com> wrote:

> On Mon, Nov 11, 2013 at 09:14:54PM -0800, terryxing wrote:
> > 1.  I am wondering that what the OVS is running like without connection
> any
> > controller ? Because I thought it is just a layer 2 switch.
>
> Yes, that's right.
>
> > but when I run a openflow controller talking to it.(I tried pox and
> > floodlight) From a internal VM, I can only talk to the VM on the same
> > logical network, but not outside. The vm can not ping 8.8.8.8, or I
> > can not reach the VM from outside bying using the floating IP. But
> > they all worked when I did not run the openflow controller.  I know
> > traffic that has something to do with outside need a router. But that
> > router is running on the network node but not compute node.  Thus, I
> > thought that running layer 2 switch on compute node should be
> > sufficient for instance communication internally or externally.
>
> POX and floodlight have lots of functionality.  Presumably you will get
> different behavior depending on how you configure them.  (I don't know
> how to configure either of them.)
>
> > 2. can "ovs-ofctl" realize this ?
>
> Be aware that ovs-ofctl is just a simple, short-lived controller.
>
> > I want to forward the packet to the port it should go, just like what OVS
> > is doing, and then can I use the CLI to modify the des_IP to the IDS's IP
> > and then output to
> > a port ? if so, which port I should output the packet with new modified
> > des_ip ?
> >
> > I do not want to disturb the how OVS originally work for forwarding the
> > packet, but just want to modified the destination ip and let the OVS
> > forward the new modified packet as it did before.
> >
> > Is that feasible ?
>
> You can use the "normal" action to forward the packet as OVS ordinarily
> would do, and then "mod_nw_dst" to set the destination IP.  You will
> have to figure out the right port yourself; I cannot guess what it is.
>
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