虽然我可以使用Openstack ping IP，但我可以使用ssh cirros而不是centos VM

I have 2 VMs, one contains cirros Image, the other contains Centos7 image. I could ssh into both yesterday. Nothing changed, but I cannot ssh into my Centos VM today, but can still ssh into Cirros VM. I tried creating more VMs, but face the same problem. I am using Openstack(Miataka)I have 2 VMs, one contains cirros Image, the ot