Re: Iptables help ..

From: Eric Gaumer (gaumerel_at_ecs.fullerton.edu)
Date: 08/31/04

  • Next message: Stefan O'Rear: "Re: mysterious X lockups on Sarge" 
    To: debian-user@lists.debian.org
Date: Tue, 31 Aug 2004 11:15:17 -0700

    On Tue, 2004-08-31 at 10:21, debi@niit.edu.pk wrote:
    > Hi,
    >
    > I am using the following iptables rules for the NAT, but i also want to
    > block outgoing port 25 traffic from the LAN clients. INAT works fine but
    > the outgoing port 25 is still open
    >
    > /sbin/iptables -F -t nat
    > /sbin/iptables -A INPUT -p tcp -i eth0 -s 0/0 -d ! 10.0.0.0/8
    > --dport 25
    > -j REJECT
    > /sbin/iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE
    >
    > But the outgoing port 25 is still open, can some tell me whats wrong in
    > these rules.
    >

    Filtering for NAT is done on the FORWARD chain. The only reason you
    appear to be blocking incoming traffic on 25 is that the port isn't
    being forwarded through in the first place.

    You don't need to explicitly block incoming traffic to the LAN because
    it only allows traffic for ports specifically setup to forward through
    into the LAN. 

    


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