Re: Iptables list

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Author: Marco Savo
Date:  
To: Main PLUG discussion list
Subject: Re: Iptables list
Thanks a lot for your help
Marco

On Fri, Nov 6, 2009 at 5:33 PM, Lisa Kachold <>wrote:

>
>
> On Fri, Nov 6, 2009 at 8:50 AM, Marco Savo <> wrote:
>
>> Thanks, but currently I have an embedded linux board (based on openwrt)
>> that use busybox, and there isn't netstat, neither nmap or lsof command. I
>> guess i can read /proc/net/tcp or udp, but iptables doesn't show a list of
>> used ports?
>>
>> On Fri, Nov 6, 2009 at 1:49 PM, Lisa Kachold <>wrote:
>>
>>>
>>>
>>> On Fri, Nov 6, 2009 at 5:30 AM, Craig White <>wrote:
>>>
>>>> On Fri, 2009-11-06 at 13:13 +0000, Marco Savo wrote:
>>>> > Hello,
>>>> > configuring iptables rules,
>>>> > how I can find out if one port number I want to use is already in
>>>> > use?
>>>> > example:
>>>> >
>>>> > $IPTABLES -t nat -I zone_wan_prerouting 1 -j ACCEPT --protocol udp
>>>> > --dport ${UDP_PORT} --destination localhost
>>>> > $IPTABLES -t nat -I zone_wan_prerouting 1 -j ACCEPT --protocol tcp
>>>> > --dport ${TCP_PORT} --destination localhost
>>>> > $IPTABLES -t nat -I zone_wan_prerouting 1 -j ACCEPT --protocol tcp
>>>> > --dport ${TCP_HOST_PORT} --destination localhost
>>>> >
>>>> > How I can check if these ports (UDP_PORT TCP_PORT TCP_HOST_PORT) are
>>>> > in use from another application?
>>>> ----
>>>> you can use netstat - for example, I might check for port 10000...
>>>> # netstat -an|grep 10000
>>>> tcp        0      0 0.0.0.0:10000     0.0.0.0:*     LISTEN
>>>> udp        0      0 0.0.0.0:10000     0.0.0.0:*

>>>>
>>>> Craig
>>>>
>>>>
>>>> You can also use nmap
>>>
>>> # nmap localhost
>>>
>>> or
>>>
>>> # netstat -anpt
>>>
>>> to see what is listening on what (depending on your distro - check
>>> syntax)
>>>
>>>
>> --
>> 'The Magic Is In the Movement'
>>
>> Marco Savo
>> SW Engineer
>>
>> 882 East Glenn St.
>> Tucson, AZ 85719
>> +1 (520) 248-5681
>>
>> Hey Marco,
>
> 1) Your netstat is probably going to be your best solution:
>
> This is how you install netstat-nat (for instance) on OpenWRT:
>
> #ipkg install http://tornado.stormchasers.dk/openwrt/netstat-nat_1.4.3_mipsel.ipk
>
> Netstat should be similar (just find the right version).
>
> Reference: https://forum.openwrt.org/viewtopic.php?id=6676
>
> 2) You can also use lsof (this one is for the whiterussian version of
> OpenWRT, so check your packages):
>
> # ipkg install http://jackassofalltrades.com/openwrt/whiterussian/packages/lsof_4.77-1_mipsel.ipk
>
> # lsof -i
>
> 3) Nmap IPTABLES testing:
>
> You can still nmap from both the inside interface(s) (from a linux machine
> or VMware machine - nmap is available for Window$s also) and from an online
> nmap portal to see what is available and listening on the outside WAN
> interface.
>
>
> http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/security-guide/s1-server-ports.html
>
> Some people configure their iptables with only nmap against each interface
> with the assumption that if it's not listening with iptables down, it
> doesn't need to be protected (be sure and check cron and anacron for any
> scripts edited if this is a possible encroached system).
>
> 4) IPTABLES kernel conntrack-tools assist to make really fine tables.
>
> Did you hand engineer your imbedded sources for that box?
>
> Are you using connection tracking: (it's a small binary build)
> http://conntrack-tools.netfilter.org/conntrack.html
> http://svn.netfilter.org/netfilter/trunk/conntrack-tools/conntrack.8
>
> OpenWRT provides for conntrack (but there are bugs on some versions).
>
>
> --
> Skype: (623)239-3392
> AT&T: (503)754-4452
> www.obnosis.com
>
>
>
>
>
>
>
>
>
>
>
>
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--
'The Magic Is In the Movement'

Marco Savo
SW Engineer

882 East Glenn St.
Tucson, AZ 85719
+1 (520) 248-5681
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