Comment 5 for bug 1512697

This bug is seen In topologies where the Contrail control node is peering with 2 gateway routers (such as MX), and each gateway router advertises a default route into the tenant VRF/VN. The tenant VN, if it has a RT configured, would import routes from both the gateway routers and as a result will have an ECMP default route. The dhclient script on the CentOS VM, after obtaining an IP via DHCP, runs a duplicate address detection procedure wherein it does an arping with the sender IP zero’d out. The vRouter upon receiving this arping, does a reverse route lookup (on sender IP of 0.0.0.0), matches the default route, and because its an ECMP route, returns the VRRP MAC. This in-turn caused the dhclient in the VM to think that a dup IP exists and so it declined the offered IP address.

The fix changes the vRouter behavior by having it not respond to such ARP probes.