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Old 04-28-2014, 05:56 AM   #1
Registered: Apr 2014
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SL6 iptables config issue.

Hi guys, I'm pretty new to iptables so I got a couple of KVM machines and set up an ftp server. I used system-config-firewall-tui to set up the ftp port.

Bang.. works, the other machine can connect, job is good.

So I look at the changes to /etc/sysconfig/iptables and see that the config line is the same as the ssh one but for the ftp port of 21.

I take a copy of the file for reference

I take the rule out using system-config-firewall-tui and sure enough it's removed.

Then I put the rule in manually using vi (to make sure I did a yyp to copy the exact line then changed it to 21)

I restart iptables then check ising iptables -L and it reports that the ftp port is open.

However my other machine can't connect. I repeat this a few times and it appears that the rule works fine when done in system-config-firewall-tui but never when I've manually altered the file even though it reports as open. I made sure it was in the right place, directly below the ssh rule.

I also did a diff on the manually altered file and the one altered by the interface and they were identical.

Is there something I'm missing??

TL;DR version:

my iptables rule seems to work when set in the tui interface but not when manually editing the file. This is on Scientific Linux 6.5
Old 04-28-2014, 02:39 PM   #2
Registered: May 2001
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- the iptables binary is the interface to the kernel part called Netfilter and no user interface shall interfere with using it that way,
- active FTP requires the control (TCP/21) and the data (TCP/20) port,
- the easiest way to debug iptables rules is to use "-j LOG" rules right before the actual rule,
- and I don't know about others but I'd rather see the actual rule set as in 'iptables-save' output.


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