Reverse Routing Concept??

24 Nov 2006 5:11 AM

adonis

I have 2 XP Pc's connecting to the outer world through a redhat 9 PC.
Squid is running in the redhat 9 PC. It has two ethernet Interfaces,
one towards backbone and other towards the 2 PC's. I am able to browse
from both the PC's. The packets that go towards backbone are all
having proxy PC mac address and IP address of that interface. So,
irrespective of which XP PC sent the packet, the proxy PC writes its
mac and IP address into it.

Query:
How does the Proxy PC reverse route the packets. All packets coming in
downlink path comes with Redhat PC mac and IP address. How does it
route it to the correct XP Pc?..

24 Nov 2006 7:37 PM

John Wunderlich

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"adonis" <vijayvikran***@gmail.com> wrote in
news:1164345079.417406.222470@j72g2000cwa.googlegroups.com:

> I have 2 XP Pc's connecting to the outer world through a redhat 9
> PC. Squid is running in the redhat 9 PC. It has two ethernet
> Interfaces, one towards backbone and other towards the 2 PC's. I
> am able to browse from both the PC's. The packets that go towards
> backbone are all having proxy PC mac address and IP address of
> that interface. So, irrespective of which XP PC sent the packet,
> the proxy PC writes its mac and IP address into it.
>
> Query:
> How does the Proxy PC reverse route the packets. All packets
> coming in
> downlink path comes with Redhat PC mac and IP address. How does it
> route it to the correct XP Pc?..
>
>

What you are trying to ask is "How does NAT (Network Address
Translation) work"?

There is a wealth of information on this topic on the web. A good
place to start is here:
<http://www.cisco.com/warp/public/556/nat-cisco.shtml>

The short answer to your question is that NAT routers maintain tables
of where packets go.

HTH,
John