Creating a filter with iptables

I want to prohibit various internet hosts from accessing a range of
ports on one of my computers. I believe that iptables is the tool that I
need for this, but I am not familiar with software firewalling in the
Linux environment. I am wading through documentation, but it is heavy
going and I am struggling to decypher the manuals. I really need an
example script that matches my requirements.

I want to block access to a range of ports 7000 to 7999 and
individual port 8026 on my server from hosts on networks 213.55.64.0/19
and 81.169.160.0/19.

I do not want anything else altered at this time, and I want all
remaining traffic to that machine to be permitted.

I have installed the iptables package, but I have not yet created a
script to activate it.

The server is an IBM compatible (Pentium 120) computer running Debian
Etch.

Thanks in advance to anyone who can help.

Regards,

Mark.

--
Mark Hobley,
393 Quinton Road West,
Quinton, BIRMINGHAM.
B32 1QE.

On Monday 30 June 2008 02:06, Mark Hobley wrote:

> I want to prohibit various internet hosts from accessing a range of
> ports on one of my computers. I believe that iptables is the tool that I
> need for this, but I am not familiar with software firewalling in the
> Linux environment. I am wading through documentation, but it is heavy
> going and I am struggling to decypher the manuals. I really need an
> example script that matches my requirements.

I *strongly* suggest you thoroughly read the documentation, rather than
trust someone else's scripts without understanding what those do. This
should be a good starting point:

http://iptables-tutorial.frozentux.n...-tutorial.html

> I want to block access to a range of ports 7000 to 7999 and
> individual port 8026 on my server from hosts on networks 213.55.64.0/19
> and 81.169.160.0/19.

You don't say if you want to block TCP or UDP ports.

iptables -A INPUT -s 213.55.64.0/19 -p tcp --dport 7000:7999 -j DROP
iptables -A INPUT -s 213.55.64.0/19 -p tcp --dport 8026 -j DROP
iptables -A INPUT -s 81.169.160.0/19 -p tcp --dport 7000:7999 -j DROP
iptables -A INPUT -s 81.169.160.0/19 -p tcp --dport 8026 -j DROP

Replace -p tcp with -p udp if you want to block UDP ports.