Comment 8 for bug 1844915

That information helped, but I am still not able to reproduce the duplicate responses.

In my test environment I have only one OpenStack cluster at the moment and I tried to minimize your description to make it fit into one cluster. I don't see how using two clusters would be essential for this bug reproduction.

First I reconfigured my master devstack for DVR. The relevant local.conf parts:

[[post-config|/etc/neutron/neutron.conf]]
[DEFAULT]
router_distributed = True

[[post-config|/etc/neutron/plugins/ml2/ml2_conf.ini]]
[agent]
enable_distributed_routing = True
l2_population = True

[ml2]
mechanism_drivers = openvswitch,linuxbridge,sriovnicswitch,l2population
tenant_network_types = vxlan,vlan

[ovs]
bridge_mappings = public:br-ex,physnet0:br-physnet0

[[post-config|/etc/neutron/l3_agent.ini]]
[DEFAULT]
agent_mode = dvr_snat

Then I tried to reproduce your setup by this (please tell me is this is the same or not, this was my best guess):

openstack network create private1 openstack subnet create private-subnet1 --network private1 --subnet-range 10.0.11.0/24

openstack network create private2
openstack subnet create private-subnet2 --network private2 --subnet-range 10.0.12.0/24

openstack network create public1 --provider-network-type vlan --provider-physical-network physnet0 --provider-segment 1000
openstack subnet create public-subnet1 --network public1 --subnet-range 10.0.20.0/24

# openstack router create router1 # already created by devstack
openstack router create router2

openstack router add subnet router1 private-subnet1
openstack router add subnet router2 private-subnet2

openstack port create port1 --network public1 --fixed-ip ip-address=10.0.20.11
openstack router add port router1 port1

openstack port create port2 --network public1 --fixed-ip ip-address=10.0.20.12
openstack router add port router2 port2

openstack router set router1 --route destination=10.0.12.0/24,gateway=10.0.20.12
openstack router set router2 --route destination=10.0.11.0/24,gateway=10.0.20.11

openstack server create vm1 --flavor cirros256 --image cirros-0.4.0-x86_64-disk --nic net-id=private1,v4-fixed-ip=10.0.11.10 --wait
openstack server create vm2 --flavor cirros256 --image cirros-0.4.0-x86_64-disk --nic net-id=private2,v4-fixed-ip=10.0.12.10 --wait

Then I logged in to vm1 (having address 10.0.11.10) and pinged every other address in this chain:

10.0.11.10 - 10.0.11.1 - 10.0.20.11 - 10.0.20.12 - 10.0.12.1 - 10.0.12.10

All of them responded, but for none did I receive duplicates.