Hi,
Can anyone tell me how to install iptables firewall on N900?

As far as I am aware, the default kernel is not compatible with iptables, or is it?
If it's not, how do I install both the compatible kernel and the iptables itself?

I've found some posts which are related to my question but since I am new to Linux I still couldn't understand how to install them

Also, if the default kernel of N900 is not compatible with iptables and if I do a firmware upgrade on my N900, will the compatible kernel got replaced so that I will have to reinstall it again?

Thank you in advance.

P.S.: If there's something wrong with what I said, please correct me since I'm not sure if I understood those things properly. All I want is a firewall