Red Hat OpenStack Platform 7 OverCloud PXE Boot Problem

I encountered a problem when deploying an OverCloud according to https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux_OpenStack_Platform/7/html/Director_Installation_and_Usage/sect-Scenario_2_Using_the_CLI_to_Create_a_Basic_Overcloud.html, the baremetal servers cannot boot up via PXE.

A UnderCloud was prepared based on the same document. A "fake_pxe" driver was used. During "openstack baremetal introspection bulk start", I saw that the baremetal server could find DHCP server and could boot up via PXE.

However, we tried to deploy the UnderCloud using the command "openstack overcloud deploy...", the baremetal server could not find DHCP server and could not boot up.

We tried to get an IP from the DHCP server and it was successful.

We are using the latest Red Hat Linux 7.2 and OpenStack Platform 7. The test was done on vSphere 5.1 (VM with RHEL 7.2 for UnderCloud; 2 VM without any OS for OverCloud).

Please kindly help.