Comment 8 for bug 1936420

did some digging here . on the multinode jobs there is a pretty clear error from the dhcp-agent logs [1][2] "Device tapc0c2f8e7-d3 cannot be used as it has no MAC address"

 2021-07-26 13:20:24.116 126380 DEBUG neutron.agent.linux.utils [req-ac28e47a-1e4e-4ef3-b310-9f17f93b9c95 - - - - -] Running command (rootwrap daemon): ['ip', 'netns', 'exec', 'qdhcp-2dd0cdd7-df67-4ee5-910b-bfa09ee0fc55', 'sysctl', '-w', 'net.ipv4.ip_nonlocal_bind=1'] execute_rootwrap_daemon /usr/lib/python3.6/site-packages/neutron/agent/linux/utils.py:104
 2021-07-26 13:20:24.149 126380 DEBUG neutron.agent.linux.utils [req-ac28e47a-1e4e-4ef3-b310-9f17f93b9c95 - - - - -] Running command (rootwrap daemon): ['ip', 'netns', 'exec', 'qdhcp-2dd0cdd7-df67-4ee5-910b-bfa09ee0fc55', 'sysctl', '-w', 'net.ipv6.conf.default.accept_ra=0'] execute_rootwrap_daemon /usr/lib/python3.6/site-packages/neutron/agent/linux/utils.py:104
 2021-07-26 13:20:24.198 139823 DEBUG neutron.privileged.agent.linux.ip_lib [-] Interface tapc0c2f8e7-d3 not found in namespace qdhcp-2dd0cdd7-df67-4ee5-910b-bfa09ee0fc55 get_link_id /usr/lib/python3.6/site-packages/neutron/privileged/agent/linux/ip_lib.py:290
 2021-07-26 13:20:24.198 139823 DEBUG oslo.privsep.daemon [-] privsep: reply[139750036169080]: (4, False) _call_back /usr/lib/python3.6/site-packages/oslo_privsep/daemon.py:511
 2021-07-26 13:20:24.200 126380 ERROR neutron.agent.linux.ip_lib [req-ac28e47a-1e4e-4ef3-b310-9f17f93b9c95 - - - - -] Device tapc0c2f8e7-d3 cannot be used as it has no MAC address

On the standalone jobs there is no dhcp-agent container so we don't have that same error, however there are different errors in neutron server.log [3]

        2021-07-19 02:08:49.050 15 ERROR networking_ovn.ovsdb.ovsdb_monitor [-] HashRing is empty, error: Hash Ring returned empty when hashing "b'908a8d0b-3423-4817-bc0b-384f3f8941fc'". This should never happen in a normal situation, please check the status of your cluster: networking_ovn.common.exceptions.HashRingIsEmpty: Hash Ring returned empty when hashing "b'908a8d0b-3423-4817-bc0b-384f3f8941fc'". This should never happen in a normal situation, please check the status of your cluster
...
       2021-07-19 02:16:14.759 15 INFO neutron.services.segments.plugin [-] Segment 4c047c5c-c230-4c8f-98ed-b5b15a5c2e90 resource provider not found; error: Placement Client Error (4xx): {"errors": [{"status": 404, "title": "Not Found", "detail": "The resource could not be found.\n\n No resource provider with uuid 4c047c5c-c230-4c8f-98ed-b5b15a5c2e90 found for delete ", "request_id": "req-ac607e4b-5e09-4ea0-90cf-eebcc2dcbfd3"}]}

[1] https://logserver.rdoproject.org/openstack-component-network/opendev.org/openstack/tripleo-ci/master/periodic-tripleo-ci-centos-8-containers-multinode-network-train/794b86d/logs/undercloud/var/log/extra/errors.txt.gz
[2] https://logserver.rdoproject.org/openstack-component-network/opendev.org/openstack/tripleo-ci/master/periodic-tripleo-ci-centos-8-containers-multinode-network-train/794b86d/logs/undercloud/var/log/containers/neutron/dhcp-agent.log.txt.gz
[3] https://b18b498c87a70760171a-55be5aa52ff9f3c19ea7817c824a7dd8.ssl.cf5.rackcdn.com/799981/1/check/tripleo-ci-centos-8-standalone/d4c3fa4/logs/undercloud/var/log/containers/neutron/server.log