iptables and dynamically assigned IP addresses

[sherington]

I am pretty much an iptables newbie, so I need a little bit of help... :D

 

I have managed, by scouring various HOWTOs and FAQs, to get a decent iptables ruleset up and running that gives me:

 

1. firewall protection, simply blocks most incoming network traffic,

2. the routing I need to my XBox (for XBox Live!).

3. internet connection sharing via masquerading to another PC on my network

 

I have a very simple network setup with my Linux PC connecting to the internet via ppp, and a network hub connecting the PC, another PC and the XBox. The XBox uses the PC's internet connection. The hub is just a dumb hub with no configuration or routing of its own.

 

All of this works just fine for me, although I have to admit I don't fully understand all of the iptables rules that I've had to create. It works, and I'm happy enough with that.

 

My problem is this, my iptables ruleset currently has a hard-coded static IP address for my internet connection. These rules are used to route traffic from the XBox to the internet and vice versa.

 

At the moment, this is OK. However, I want to upgrade my internet connection to a higher capacity (1Mb from 512Kb) - part of this upgrade will mean that I will have a dynamically assigned IP address from the ISP for the internet connection rather than the static IP I have now.

 

The firewall script and the script(s) that start the internet connection both run automatically when the PC is started up.

 

How do I handle this dynamic IP in my ruleset?

 

Any pointers or help will be gratefully appreciated.