External DVD-ROM drive issue whether it is working or not? on HP rp7400

Please help me >
How to diag the external DVD-ROM drive issue whether it is working or not? on HP 9000 server rp7400
I needed to install HP 11i v1 using external DVD-ROM drive on HP 9000 server rp7400. While boot in CO> �search� command is not showing DVD-ROM device only showing all disks > BOOT PO or P1 is not working. Showing some IPL errors.
After boot system on exiting disk OS, # ioscan funC disk are not showing DVD info.
I have multiple HPUX 11i dvds, I can able to mount on other hpsystem
Thank you
TP

I have fixed the issue after moving dvdrom scsi cable connection to onboard utlra 2. Thanks