Hi, I've tried to work with multiple l3_agents in Juno using Flat for external networks without success. I did:

ovs-vsctl add br-ex
ovs-vsctl add-port br-ex eth2

 neutron net-show ext-net
+---------------------------+--------------------------------------+
| Field                     | Value                                |
+---------------------------+--------------------------------------+
| admin_state_up            | True                                 |
| id                        | bfbb6efc-165d-4499-bbef-5ef0b2a79a85 |
| name                      | ext-net                              |
| provider:network_type     | flat                                 |
| provider:physical_network | external                             |
| provider:segmentation_id  |                                      |
| router:external           | True                                 |
| shared                    | True                                 |
| status                    | ACTIVE                               |
| subnets                   | f95642ef-8d4f-4f88-9775-e526f05e348b |
| tenant_id                 | 9462bb211cab45729d9279ac635e7f60     |
+---------------------------+———————————————————+

/etc/neutron/plugins/ml2/ml2_conf.ini

[ml2]
type_drivers = flat,gre
tenant_network_types = gre
mechanism_drivers = openvswitch

[ml2_type_flat]
flat_networks = external

[ml2_type_vlan]

[ml2_type_gre]
tunnel_id_ranges = 1:1000

[ml2_type_vxlan]

[securitygroup]
enable_security_group = True
enable_ipset = True
firewall_driver =neutron.agent.linux.iptables_firewall.OVSHybridIptablesFirewallDriver

[ovs]
local_ip=172.16.1.1
enable_tunneling = True
bridge_mappings = external:br-ex

[agent]
tunnel_types = gre

/etc/neutron/l3_agent.ini

[DEFAULT]
verbose=True
interface_driver = neutron.agent.linux.interface.OVSInterfaceDriver
use_namespaces = True
handle_internal_only_routers = True


agent_mode = legacy

external_network_bridge =
gateway_external_network_id =

router_delete_namespaces = True

The namespace of the router

ip netns exec qrouter-210912bb-b727-49ff-9ccf-cda57e5e6f93 ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
129: qr-7efff1c9-17: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
    link/ether fa:16:3e:c5:51:a2 brd ff:ff:ff:ff:ff:ff
    inet 10.93.1.1/24 brd 10.93.1.255 scope global qr-7efff1c9-17
       valid_lft forever preferred_lft forever
    inet6 fe80::f816:3eff:fec5:51a2/64 scope link
       valid_lft forever preferred_lft forever
130: qg-b0ec7417-46: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
    link/ether fa:16:3e:1e:f3:48 brd ff:ff:ff:ff:ff:ff
    inet 192.168.185.200/24 brd 192.168.185.255 scope global qg-b0ec7417-46
       valid_lft forever preferred_lft forever
    inet6 fe80::f816:3eff:fe1e:f348/64 scope link

But when I ping the gateway

ip netns exec qrouter-210912bb-b727-49ff-9ccf-cda57e5e6f93 ping 192.168.185.1
PING 192.168.185.1 (192.168.185.1) 56(84) bytes of data.


From 192.168.185.200 icmp_seq=1 Destination Host Unreachable
From 192.168.185.200 icmp_seq=2 Destination Host Unreachable
From 192.168.185.200 icmp_seq=3 Destination Host Unreachable

Any suggestions?