TFTP Server with 2 NIC cards

I am running the TFTP server on a computer with two NIC cards.  One NIC card is set for DHCP and is typically connected to my corporate's internal network.  The other card is set to a static local address (10.0.0.X).  This NIC card is used to communicate with lab equipment and units under test.   The server is configured to bind to the second NIC card (10.0.0.X), but will not work unless the first NIC card is connected to the network.

Why is this?  Am I missing something?  There will be times when the first NIC card will not be connected to the network, which is why I bound the server to the second NIC card (10.0.0.X).

Any help or explanation would be appreciated.