Everyday got alert "[VMware vCenter - Alarm Host connection failure] Host xx in hkdatacenter is not responding"
A : Indicates that there was a heartbeat timeout between the esxi host to the vCenter server and the Host is not reachable in the vCenter server.
A : ping the esxi host and see if its reachable from the vCenter server machine
if reachable, verify if the vpxa and hostd are running in the ESXi, Try restarting the management agents
If not reachable investigate the network
I would consider the possibility of DNS issues as well.
I always prefer hostname, but also frequently create a manual hosts file (especially for vCenter) as well. Host file for Windows is: \Windows\System32\drivers\etc\hosts for VCSA: /etc/hosts