If for some reason you are experiencing name resolution issues in your vSphere environment one useful troubleshooting task is to perform a flush of the local DNS cache on the vCenter VCSA. VCSA creates a local cache and uses the dnsmasq service to handle DNS queries internally in local cache; as you can see by the internal 127.0.0.1 IP listed in resolv.conf:
As VCSA uses Photon OS we leverage the systemctl command in order to restart services.
Begin by SSH to VCSA, we can view the current Photon OS version:
The command used to clear the DNS cache on vCenter VCSA:
systemctl restart dnsmasq.service
Checking service status after restart:
systemctl status dnsmasq.service
It may also be worth checking /etc/hosts for any unexpected entries(which of course there should be none as this file is not to be modified) as dnsmasq will query the contents of /etc/hosts during a DNS query: