Verizon Cellular service and NetworkManager shared networking

[Andy Graybeal <andy graybeal casanueva com>]

Hi everyone,
I've purchased the Verizon Cellular internet service for home. I love
it, especially when compared to regular dial-up, which is what I'm used to.

I have the USB760 and I got this to work just perfect after I followed
the second post on this forum thread:
http://ubuntuforums.org/showthread.php?t=1002262

One problem that I have is when I share the internet (USB760 = ppp0)
over ethernet (eth0) with NetworkManager.. Verizon will disconnect...
say every 20 minutes or so; sometimes 5 seconds, sometimes 45 minutes,
but mostly around 20 minutes.

The service is disconnected by this: LCP terminated by peer a command
sent from Verizon after what I've suspect (and from what I've read in
the forums) they've received too many(?) private ip addresses sent to
their public network. (here's the post confirming this:
http://www.mail-archive.com/networkmanager-list gnome org/msg10840.html )

Here's a post with what might be the answer:
http://www.mail-archive.com/networkmanager-list gnome org/msg14760.html
The poster outlines changing:

iptables -A FORWARD -i eth0 -o ppp0 -j ACCEPT

to this:

iptables -A FORWARD -i eth0 -o ppp0 -m state --state
NEW,ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -j drop-and-log-it


But how do I configure NetworkManager's iptable settings to get this to
work? Is it in the NetworkManager's script files
(none of which I
understand)?

I don't understand iptables either. I'm a little better at pf.

Any help is appreciated.  I posted this to the ubuntu users list, but I 
didn't receive any responses.


-Andy