VMware Tools contains a utility that allows
the NSX Manager to collect the IP address(es) of each guest running
in the cluster. NSX Manager uses the IP address as a match criterion
to steer traffic to the VM-Series firewall. If you do not have VMware
tools installed on each guest, the IP address(es) of the guest is
unavailable to the NSX Manager and traffic cannot be steered to
the VM-Series firewall.