Comment 14 for bug 1818060

With Rodolfo and Kieran we did some debugging today on environment provided by Yatin. Finally we found out that problem was "arp_ignore" sysctl option which was set on compute nodes to 0 (default value).
According to documentation https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt this means that kernel will reply for ARP request if requested IP address is on ANY of interfaces in the system. And indeed we had something like that. On one of compute nodes which hosted one of vms connected with Yatin's controller-2 on some interface (vlan111X) there was exactly same IP address configured.
When we switched "arp_ignore" to 1 problem was gone.