Setting up a jail's IP address?

[Luke]

> The first problem I'm having is that according to every jail tutorial I've 
> seen so far, I'm supposed to bind the IP address of the jail to a NIC. 
> Well... both of my NICs already have IP addresses bound to them, so ifconfig 
> always fails with "ioctl (SIOCAIFADDR): File exists".

Okay, I figured this one out.  The jail was active at the time.  Once I 
shut down the jail I had no trouble binding it.

> The second problem is that I'm not entirely sure which network card I would 
> bind the jail to anyway.  The jail has to have an internal IP address, I 
> assume, but it needs to talk to the outside world so my first instinct is to 
> bind it to the network card that's hooked to the outside network.  That would 
> mean binding two addresses that aren't even on the same network to one card, 
> and that sounds like it might be problematic.

I'm still curious about which NIC is the proper one to bind the jail to. 
Does it matter?