Duplicate neutron and nova service agents running on the controller nodes causes the router namespaces to disappear in RHOSP10.

Issue

• We see duplicate neutron agent services on all of the stack controller nodes and also see none of the qrouter namespaces active on the nodes:

$ neutron agent-list | grep -i controller-1
| 0f517596-51bb-456c-b49f-185b4db8d3d3 | L3 agent           | overcloud-controller-1              | nova              | :-)   | True           | neutron-l3-agent          |
| 3060878d-1181-4901-b469-edac4eca9d2d | L3 agent           | overcloud-controller-1.localdomain  | nova              | xxx   | True           | neutron-l3-agent          |
| 5a612d15-9431-4b58-9d9d-388c512c65dd | DHCP agent         | overcloud-controller-1              | nova              | :-)   | True           | neutron-dhcp-agent        |
| 99bddf94-b21e-41f2-9145-f4d168a48c04 | Metadata agent     | overcloud-controller-1.localdomain  |                   | xxx   | True           | neutron-metadata-agent    |
| 9d613e68-25c0-4195-bc75-2f4c8968de2d | DHCP agent         | overcloud-controller-1.localdomain  | nova              | xxx   | True           | neutron-dhcp-agent        |
| bf2315a2-dc71-4cd8-8070-313252a9633c | Open vSwitch agent | overcloud-controller-1              |                   | :-)   | True           | neutron-openvswitch-agent |
| e670575d-40b9-4684-8165-3318db08c278 | Metadata agent     | overcloud-controller-1              |                   | :-)   | True           | neutron-metadata-agent    |
| e78f6210-3849-452e-873c-130c8f1679c8 | Open vSwitch agent | overcloud-controller-1.localdomain  |                   | xxx   | True           | neutron-openvswitch-agent |

• The VM instances are presently unreachable from external network due to this issue.
• This issue occurred with the overcloud nodes were manually update with yum update command.
• Duplicate neutron and nova service agents running on the controller nodes causes the router namespaces to disappear.
• How to restore the router namespaces and connectivity of tenant network with the external?