To not cause any confusion, especially regarding the security implications - I suspect that this only becomes an issue when the neutron-agent is running in version 15.3 while the server is still on 15.1:

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2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent Traceback (most recent call last):
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/neutron/plugins/ml2/drivers/agent/_common_agent.py", line 465, in daemon_loop
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     sync = self.process_network_devices(device_info)
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/osprofiler/profiler.py", line 160, in wrapper
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     result = f(*args, **kwargs)
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/neutron/plugins/ml2/drivers/agent/_common_agent.py", line 207, in process_network_devices
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     device_info.get('updated'))
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/neutron/agent/securitygroups_rpc.py", line 258, in setup_port_filters
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     self.prepare_devices_filter(new_devices)
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/neutron/agent/securitygroups_rpc.py", line 123, in decorated_function
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     *args, **kwargs)
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/neutron/agent/securitygroups_rpc.py", line 135, in prepare_devices_filter
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     self._apply_port_filter(device_ids)
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/neutron/agent/securitygroups_rpc.py", line 159, in _apply_port_filter
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     security_groups, security_group_member_ips)
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/neutron/agent/securitygroups_rpc.py", line 176, in _update_security_group_info
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     remote_sg_id, member_ips)
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/neutron/agent/linux/iptables_firewall.py", line 150, in update_security_group_members
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     self._update_ipset_members(sg_id, sg_members)
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/neutron/agent/linux/iptables_firewall.py", line 156, in _update_ipset_members
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     sg_id, ip_version, current_ips)
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/neutron/agent/linux/ipset_manager.py", line 78, in set_members
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     member_ips = self._sanitize_addresses(member_ips)
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent   File "/usr/lib/python3/dist-packages/neutron/agent/linux/ipset_manager.py", line 47, in _sanitize_addresses
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent     for ip, _mac in addresses:
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent ValueError: too many values to unpack (expected 2)
2020-11-03 06:25:10.217 2749 ERROR neutron.plugins.ml2.drivers.agent._common_agent 
2020-11-03 06:25:11.481 2749 INFO neutron.plugins.ml2.drivers.agent._common_agent [req-c98ece1a-2967-4807-9693-689f9de31639 - - - - -] Linux bridge agent Agent out of sync with plugin!
[...]
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