dsl and the confusedness the howto brings about various protocols

[Tommy Moore]

Actually Frank's right. It does help to add a second NIC as far as security goes because even though your using private ips for your boxes there's still the chance that someone can get in to your box if they know what esubnet your using by spoofing their source address.
In this way you can block certain types of traffic from entering based on the interface meaning eth0 or eth1.
This helps because you wouldn't want people accessing your samba shares from the outside would you?
You could disallow samba traffic both ways on the first NIC while letting it work on the second.
Also with this method you can be secure from the outside and be as unsecure as you wana be on the inside.

Just my opinion on this subject.

Tommy.