My router is really good at assuring that when I turn off a computer and move it around - it gets the same IP it was using before.

Even if I leave a computer down for a week or more, it will usually regain the same address it had (using the factory DHCP settings on my router).

So it was strange for me this morning, to see one of the NICs on my Linux box has mysteriously changed IPs.

Is there a good log or trail I can follow to try to figure out why/how/when this happened?

BTW, this box has 2 NICs and the other is still using its old address. Furthermore, the system itself has not been reset during this period.

I have messed with the SSH and Apache configuration files (simply to change ports but that shouldn't have done anything to the IP address) and I doubt the connection dropped for any significant period (as the other NIC wasn't effected) - so I am just kinda puzzeled.

I'm pretty sure that you can't just install something and have it know what happened previously. I'd take a look at any log files that you already have on your computer...

I didn't install anything.

Oh - maybe you are talking about when i move my computers around and they get their old IP's back. It seems obvious to me that the router is keeping track of MAC's and as long as it dosn't loose a MAC mapping - it will try to keep the same IP with the same MAC. Only makes sense.

But I am saying this was just sitting around and it changed IPs. Out of 6 computers sitting around for months - why would this one NIC get the gumption on its own to change IP's (or why would the router do it)?

I am just trying to figure out which logs to look in and what to look for in these logs.

Unfortunately, my router log isn't going to be any help. It only logs connections to filtered addresses.