[kolla-ansible][wallaby][magnum] calico works, flannel does not work

Hi, I don't have any experience in kubernetes yet, my goal in the present is to test that the auto-sacele of a kubernetes cluster is working properly using magnum. I followed some tutorials to get the test done. I tried to configure the test but I had problems with magnum-metrics-server not being able to provide metrics, after digging and reading a lot of things on the web, I found out that kubernetes master couldn't connect to the metrics server (curl -k https://ip_metrics_server didn't work) So I created another template but this time using calico as a network provider, and this time it worked. How can I find why flannel does not work? where should I look? Regards.