On 2005.12.12 16:46, Gene Dellinger - gene@xxxxxxx wrote:
To All:
I got some helpful information, thanks to those who responded, I am still a
bit fuzzy though.
A packet coming in ETH0 destined for a system connected to ETH1, will that
packet begin in the PREROUTING
chain on ETH1(sample 1) and then out or go to the FORWARD chain(sample 2)
and then out.
Neither example matches the structure of netfilter.
There is only one each of prerouting, forward, postrouting.
There is not one chain per interface.
If you need to specify the interface in a rule,
you must use the -i and -o fields in that rule.
One or the other of these fields may not be useable in some chains.
ETH0:PREROUTING---->FORWARD---->POSTROUTING---->OUT
| | |
INPUT | OUTPUT
| \|/ |
Local Process | Local Process
|
----<---<-----|
|
\|/
ETH1:PREROUTING---->FORWARD---->POSTROUTING---->OUT
| |
INPUT OUTPUT
| |
Local Process Local Process
sample 1
_________________________________________________________
ETH0:PREROUTING---->FORWARD---->POSTROUTING---->OUT
| | |
INPUT | OUTPUT
| \|/ |
Local Process | Local Process
|
|
|
\|/
ETH1:PREROUTING---->FORWARD---->POSTROUTING---->OUT
| |
INPUT OUTPUT
| |
Local Process Local Process
sample 2
_________________________________________________________
Thanks Again
Gene D.
-----Original Message-----
From: Gene Dellinger [mailto:gene@xxxxxxx]
Sent: Friday, December 09, 2005 2:40 PM
To: netfilter@xxxxxxxxxxxxxxxxxxx
Subject: FORWARD Chain Question
On a multi-homed machine being used as a firewall, if
a packet is forward'd from one interface to another.
Does the packet enter the in at PRE-ROUTING portion of iptables
chain again for that interface? It may seem obvious but
I just want to make sure I am clear on that aspect of the
chain traversal.
Thanks
Gene D.
--
Jim Laurino
nfcan.x.jimlaur@xxxxxxxx
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