When configuring GRE with DP 9.x, additional steps/Changes are needed for VCSA 6.0.
1) In /etc/hosts file of VCSA, 127.0.0.1/localhost entry can be hashed out completely or place the FQDN hostname/IP Address before the localhost entry.
X.X.X.X FQDN ShortName
127.0.0.1 localhost
2) In /etc/vmware/appliance/firewall/service.conf file, add inbound rule entries for DP communication ports under "vsphere-client". Only applicale if VCSA Firewall Services needs to run. Restart of VCSA might be needed after making the changes.
{
"direction": "inbound",
"name": "Appserver",
"port": "7116",
"porttype": "dst",
"protocol": "tcp"
},
{
"direction": "inbound",
"name": "GRE",
"port": "15000:15999",
"porttype": "dst",
"protocol": "tcp"
}