That's a software question.
This is a hardware forum.
You didn't specify, but I'll presume you are not talking about any add-on card.
The necessary software packages for the onboard
broadcom BCM5703 gigabit (bge) circuitry are native to Solaris x86 (4/04 and newer).
Therefore they'll be on your OS installation CD's.
Just install the OS and rock-n-roll.