Hi,
The new Advanced GRE plugin for VMware was designed to run outside of the vCenter so it can be used with new Virtual Center appliances from VMware.
These VCSA appliances usually have iptables running and blocking incoming connections. So it is required to stop iptables or open the required ports (15000-15999) as explained in the GRE guide:
Make sure the VMware Granular Recovery Extension Agent (vmwaregre-agent.exe) is in the list of Windows/Linux Firewall exceptions, on both the mount proxy system and the vCenter Server systems.
Note: Only inbound firewall rules are automatically created during the installation of the Granular Recovery Extension for VMware vSphere. You need to manually create any outbound firewall rule. This is required for communication between the extension's components and the vCenter Server. For the required port ranges, see the HP Data Protector Installation Guide: "firewall support"
The port ranges for the Advanced GRE Web-plugin are between 15000 and 15999.
If the connection to these ports is not allowed, the plugin will fail to connect to the VCSA and you will get an error when trying to save the GRE settings.
Regards,
Juanjo