please explain "--state RELATED/ESTABLISHED" rules in iptables

please explain "--state RELATED/ESTABLISHED" rules in iptables

[Christian Seberino]

My firewall iptables script has rules
to drop lots of packets and only forward
certain packets.....

I've seen lots of iptables scripts that
have rules with "--state RELATED"
and "--state ESTABLISHED".

I know these have to do with TCP packets
related to an existing TCP connection and such.

*What* are these rules good for?  I didn't
use them and couldn't see a need for them.

Chris

-- 
_______________________________________

Dr. Christian Seberino
SPAWAR Systems Center San Diego
Code 2363
53560 Hull Street
San Diego, CA 92152-5001
U.S.A.

Phone: (619) 553-7940
Fax:   (619) 553-2836
Email: seberino@spawar.navy.mil
_______________________________________

Re: please explain "--state RELATED/ESTABLISHED" rules in iptables

[Antony Stone]

On Friday 21 June 2002 4:33 pm, Christian Seberino wrote:

> My firewall iptables script has rules
> to drop lots of packets and only forward
> certain packets.....
>
> I've seen lots of iptables scripts that
> have rules with "--state RELATED"
> and "--state ESTABLISHED".
>
> I know these have to do with TCP packets
> related to an existing TCP connection and such.
>
> *What* are these rules good for?  I didn't
> use them and couldn't see a need for them.

http://www.netfilter.org/documentation/HOWTO//packet-filtering-HOWTO-7.html#ss7.3

Look down until you find "the state match" section.

 

Antony