Some basic esxi questions (how to's)

Hi,

I've just installed esxi 5.1 trial. I have a few questions:

1) One of my NICs is reported as "Down" under speed. Is this an error with the hardware? See screenshot below:

2) I can configure DNS servers in DNS and Routing, but how do I do this per NIC? I want one NIC to be the public NIC, and another the internal NIC that will point to my domain controllers for DNS servers.

3) I am looking at replacing certs in esxi 5.1 and the guides/faqs/kbs, but can esxi 5.1 work with certs from my internal windows ca?

Thanks!