Re: NAT tables chains

From: Eric Teuber (eric000_at_gmx.net)
Date: 07/28/05 

Date: Thu, 28 Jul 2005 21:43:51 +0200

lekkie.aydot@gmail.com wrote:
> ty u for takin the pain to reply. I went thru the howto
> (netfilter.org), i got the concept but didn't get the implementation.
> However, I got the filter table quite fine while I'm left withs
> question in the NAT table.
> So how does packet returnin to LAN hosts from the internet gets its
> original packet requests. My thinkin is may be thru the pre-routing
> config.
> By sayin returnin packets I mean packets that originated from the LAN
> hosts due to its request to a remote service (web) thru the router.
> These packets I believe returns to the router and the router has to
> find a way of identifyin the original sender of such packets, is that
> what pre-routin does?
>

Sorry for being so rude! I didn't know you read the howto's already!

Your client (LAN) makes a request to your router since it is responsible
to forward the traffic (routing table); it will forward the traffic and
remembers the connections by analyzing the TCP/IP headers.

Your client (on the way to the world) will connect to your router, your
router will know the request (SYN) and is going out to www. It will
remember the source address/port and the destination address/port.
Because of these informations (and some more, f.E. ACK), it will find
the right way back to your client, if the connection is related or
established to the one your client has requested.

Eric

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