Yes, my hardware firewall has rules for various things and has the ability to be modified easily by me, and "should" be filtering those ranges. I added all the other private addresses no problem, but im not on those ranges. So those lines are probably not needed as well. The particular tutorial I was going off of mentioned a couple of times that some of the rules if not thought out and done wrong can block yourself from your own net. I think I'll leave this rule out. My eth0 nic is on that range, and I should expect my firewall to block this type of attack.
But in saying that, I can't remember where now; there was a good whitepaper about conducting this type of attack over a firewall. I remember that spoofing attack was done with a little scanning and a little packet crafting. The attacker was able to determine what the private range was the LAN was using and then defeat the mechanisms meant to filter private ranges from the net. Thing was, I don't think it accounted for a paranoid setup where firewall and LAN where blocking this attack.
Link related:
http://wiki.archlinux.org/index.php/Sim ... wall_HOWTO
The setup at the link is pretty much how I set it up, except for a few mods I did. If any one knows of another good writeup of an even more secure setup, then holler back.
Also, I wouldn't mind talking more about the theory of this type of attack, and if it's still a viable type of attack nowadays. Any thoughts on this?