[OT?] I have 4 IPs. How is outbound IP selected, say run lynx URL on server?

I'm just curious. Is there a default method to select on this? Random?
Can I control this somehow?
It's clear how everything else selects IP, but I just wanted to know in
case that ever mattered, say one of my IPs were blocked.
And I wanted to be sure which IP outbound is or is not used for running
something like lynx, etc.

Not terribly important, but at least interesting question for me.

Thanks,
Chris Bennett