[ovs-discuss] Ping between VMs in OVS

[Jesse Gross]

On Fri, Nov 29, 2013 at 1:36 PM, Ben Pfaff <blp at nicira.com> wrote:
> On Fri, Nov 29, 2013 at 06:03:05PM +0530, Rahul Nanda wrote:
>> When I did ping between VM1 and VM2, the ARP packet came to OF controller
>> as PACKET_IN and controller has send PACKET_OUT message and added a unicast
>> flow with in-port and dl_dst to output:VM2 port.
>>
>> The ICMP echo req packet has come to VM2.
>> I expected the VM2 to send ICMP echo reply which would be a packet miss in
>> OVS as there is no associated flow.
>>
>> Instead VM2 also sent an ARP request for VM1 and I could see this in our OF
>> controller.
>> Can't VM2 just use the srcMAC in ICMP echo req instead of sending ARP again
>> ??
>
> That's not what TCP/IP stacks do.  I don't know the reason off-hand.

It's trying to establish bidirectional connectivity, which can't be
done solely by receiving a packet.