Router Settings (ports)

[Nutter]

I shall rephrase my original question. I currently have adsl, I have a router that has NAT and a Firewall. Presently my Windows XP as accces to the net and other applications are able to run (i.e Games, FTP, e-mule etc.) I opened the only the required ports for these programs, the rest are closed. I wish to do the same for my Linux machine (mandrake 10) Presently I have access to the net (via I believe port 80) BUT Mandrake Update center does not access with the firewall on. (Im guessing the port it requires is closed). I have opened 20 and 21 but that made no difference. Is there a program that I can use on Linux that will enable me to see what port is been attempted on by the update program etc. Or is there a list of common ports that Linux (mandrake requires open)
I will eventually look a setting up a software firewall on the Linux machine, but I will start with small steps and move to that later. Any help would be great.

[happybunny]

netstat ?

or netstat --inet (thats 2 dash's)

[Nutter]

That worked a treat , but each time update connects I seem to be having topen more and more ports. How can set this so that it just uses a minimal amount of ports etc . At the moment I open up say 2212 the nest time its another and another etc? As someone pointed out before I thought it was just a ftp based program (ie port 20 or 21?)
How can i configure this so i dont end up opening all these ports?

[j79zlr]

you don't need any ports forwarded in the router unless you are running a server. eMule is a server, that is why you need to forward ports for that. NAT only prevents incoming packets, it does not block any client requests, i.e. web browing, connecting to an FTP server or the like.

[Nutter]

Yes I understand what NAT does, my problem lies with the firewall ?

[daYz]

You can use the "ps" command to see what processes are running. If the update program uses FTP you can try to use passive FTP instead of active FTP. Active FTP tries to open ports at the client's site which could cause these kind of problems. Passive FTP tries to open ports at the server's site, so maybe you kind find a way to set it up that way. You can do "ps -eax", and maybe try google to find info about this problem. There are probably more people with this problem.

j79zlr is right. If you don't run a server you don't need to open ports on the router, but I presume you've already closed them.
You only need to forward traffic on the router to your pc to be able to use your clients like emule etc. So for Emule you'd only choose to forward ports 4661 to 4669 or something. How to setup port fowarding is explained in the router's manual.

[Nutter]

Yes I understand that. Oh well I have new problem so ill post that one and come back to this one later.