[CentOS] Strange behaviour of iptables in centos 7

anax anax at ayni.com
Tue Mar 8 09:22:22 UTC 2016



On 03/08/2016 09:43 AM, James Hogarth wrote:
> On 8 Mar 2016 07:36, "anax" <anax at ayni.com> wrote:
>>
>> Hi
>> strange behaviour of iptables on a centos 7.0 machine:
>> The following rule is in the iptables of said machine:
>>
>> [root at myserver ~]# iptables -L -v -n --line-numbers |grep 175\.
>> 9        9   456 DROP       all  --  *      *       175.44.0.0/16
> 0.0.0.0/0
>> [root at myserver ~]#
>>
>> The corresponding enty in /etc/sysconfig/iptables looks like:
>>
>> [root at myserver ~]# grep 175 /etc/sysconfig/iptables
>> -A INPUT -s 175.44.0.0/16 -j DROP
>> [root at myserver ~]#
>>
>> The rule must be there since ages, because it has number 9 out of 76
> similar rules.
>>
>> Today, on the same machine (I rechecked it to make sure not to confound
> machines), I see the following extract of the ftplog:
>>
>> <snip>
>> 175.44.4.127    2915
>> 175.44.26.128   2021
>> 175.44.26.138   1322
>> 175.44.6.186    1290
>> 175.44.24.88    1219
>> 175.44.4.199    1212
>> </snip>
>>
>> saying that from this IP addresse there have been this many connections
> to the ftp server on that machine during the last two days, which means
> that the iptables haven't dropped the connection to the machine. As far as
> I know, the ftp server is behind the iptables. I also checked to see in man
> iptables, wheather the IP address is represented correctly.
>>
>> What im I missing?
>>
>
> Please provide the full iptables listing as a snippet from one section is
> not useful.
>
> Keep in mind iptables does not go by the most specific entry but rather the
> first matching rule hit.
>
> If there are any rules prior to this drop that would permit the traffic
> then of course the traffic would be permitted.
>
> Also 7.0? Please get that system updated asap as you are missing many
> important (and higher) issues being fixed.
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>

Hi James

[root at myserver ~]# cat /etc/centos-release
CentOS Linux release 7.2.1511 (Core)
[root at myserver ~]#

[root at myserver ~]# uname -a
Linux myserver.mydomain.com 3.10.0-327.4.4.el7.x86_64 #1 SMP Tue Jan 5 
16:07:00 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
[root at myserver ~]#

suomi



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