No console output on the rear Display connector of HP DL380 G7

Issue

• Installed RHEL6.3 on a HP Proliant DL380 G7
• The system has 2 display output ports, one on rear and another on front.
• POST messages and initial bootup messages are displayed on rear monitor.
• The rear output becomes blank during the boot process of the system while front output displays the consoles.
• This problem didn't occur during installation of the system.
• The system is booted in runlevel 3, no X window running there.