Two devices with same MAC address?

How is it possible that my new Dell server and my old camera system head-unit (DVR) have the same MAC address?

If I look in DHCP I can see what the DVR MAC address is.
If I watch the bootup screen on the new server, I can see what the MAC address is.
I have compared them and they are the same!

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Gary CaseConnect With a Mentor RetiredCommented:
While exceptionally unlikely, it IS possible if some element of the system is using MAC Spoofing, or if one of the addresses (most likely the camera system unit) wasn't assigned by the NIC manufacturer  [The manufacturers include a manufacture ID component in the MAC, and it's almost certain they would not duplicate the rest of the assigned MACs.]

Are you CERTAIN you're looking at the physical MAC addresses?  [6 pairs of hex numbers]
Steve KnightConnect With a Mentor IT ConsultancyCommented:
Just possible... but could it more likely be.... that the entry you see in DHCP for your DVR IP Address is actually your new server which happens to have acquired the same IP as you DVR as you didn't exclude it from the dhcp scope.... sorry if too obvious!

Otherwise as has been said it would be very unlikely that two devices had duplicated MAC addresses, especially from a different supplier.

You could use dhcploc.exe from one of the W2K resource kits or a packet sniffer such as Ethereal to check what is going from your DVR when it boots, and or if from a different PC on the same subnet you do:

ping (dvr ip address)
ping (server ip address)
arp -a

it will list the mac / ip addresses in your cache.
Assuming the 2 devices have different IP addresses - verify that the devices have different addresses by pinging them and then typing

arp -a

at a command prompt...this will tell you what the MAC addresses are - it is *extremely* unlikely as garycase says above !
You may be able to override the mfgr MAC address on your computer.  Look in the Advanced configuration of the NIC.  
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