[ovs-discuss] VLAN problem on Xenserver OVS and NOX

Jesse Gross jesse at nicira.com
Thu Feb 16 17:03:26 UTC 2012

On Wed, Feb 15, 2012 at 9:30 PM, James Chung <jachung2 at gmail.com> wrote:
> Thank you for your quick reply.

Please don't drop the mailing list or top post.

> The weird thing is that if I apply the same NOX to control openflow switch
> only, the vlan function perfectly. The VM1 in vlan 100 can only ping to VM2
> in vlan100, but not VMs in other vlan. The conflagration as follows:
> VM1<-->OVS1 (on server1) <--->OF switch <---> OVS2 (on server2) <--> VM2

When you are trunking there's no need to add/remove tags and you
probably don't have overlapping MAC addresses in different vlans so
you don't have learning problems.  The tags just get copied through.

> Even I use physical switch (with vlan trunk) to replace OF switch, and
> without any NOX controller, the vlan also function perfectly.
> VM1<-->OVS1 (on server1) <--->phy switch <---> OVS2 (on server2) <--> VM2
> I can see the flow with vid in dom0 using "ovs-dpctl dump-flows xenbr1".
> However, If I use the same NOX controller to control two OVSes,  I can ping
> from Vm1 (vlan100) to Vm2 (vlan200), the vlan is not function correctly.
> When I check the flow in dom0 with ovs-dpctl, it shows a normal icmp flow
> without vid. The vlan tag seems disappear in OVS. I also checked the flow in
> NOX controller, the dl_vlan became 65535. I am not quite sure which part
> getting wrong.

As I said before, if you want tags you need to add tags.  OpenFlow
gives you control to do things differently from how a switch might
normally be programmed but that means you need to do it yourself
instead.  In your other examples, OVS is the one doing the tagging but
here you told it not to do it.

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