[plug] ip address and interface question

[Jason]

Greetings everyone,

I'm a new subscriber to PLUG but I've been using linux for about 7 or so years now as my primary OS on my laptop and other random machines in my 
house :)

This is an annoyance that I've had since first installing linux on my laptop a couple of years ago and finally thought I'd try to find out how to fix 
it :)

I have two interfaces, eth0 (wired) and eth1 (wireless ipw2200 drivers).  eth0 is configured with the ip address of 192.168.0.4 and eth1 192.168.0.5.

If I bring down eth1 and bring up eth0, or vice versa, I can still ping both ip address and receive replies, even though one of the interfaces 
associated with one of the ip addresses is down.

Although this isn't life-threatening or causing any problems, it just bugs the hell out of me!

Can anyone tell me:

1.  Why it acts in this manner?
2.  How I can stop it?

Thanks in advance.

Regards,

Jason.