Linux iptables not working

iptableslinuxsmtpUbuntu

I updated my iptables in Ubuntu 10.04, but it doesn't seem to be having any affect on the opened ports.

When I run iptables --list, the following line shows up

Chain INPUT (policy DROP)
target   prot opt source              destination
ACCEPT   all  --  anywhere            anywhere         tcp dpt:smtp

However, when I try to do a port scan to see if port 25 is open, it responds as closed. Could there be something further upstream that is blocking the port? Or do I need to do something to 'restart' the firewall after modifying the IP tables?

Linux Noob here if it doesn't quite come through …

Best Answer

If netstat -tapnl | grep 25 doesn't return something like 0:0:0:0:25 (or the paticular IP you query) it means nothing is listening on that port and IPTables is not the problem -- or at least not the only problem.

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