Comment 5 for bug 1933234

I just confirmed it with logs from https://storage.bhs.cloud.ovh.net/v1/AUTH_dcaab5e32b234d56b626f72581e3644c/zuul_opendev_logs_bb7/798648/1/gate/neutron-fullstack-with-uwsgi/bb732a9/controller/logs/dsvm-fullstack-logs/TestLegacyL3Agent.test_mtu_update/neutron-l3-agent--2021-07-01--00-21-48-384074_log.txt
The issue is that sometimes update_network event comes when router is still processed and port isn't added to the internal cache in https://github.com/openstack/neutron/blob/3764969b82c6e7b8c74172a1ec4d230ce4ddedcc/neutron/agent/l3/router_info.py#L636 so it's not available in https://github.com/openstack/neutron/blob/3764969b82c6e7b8c74172a1ec4d230ce4ddedcc/neutron/agent/l3/agent.py#L602 thus router is not processed as a result of network_update.