Re: need to have W98 with two IP Address

From: Madhur Ahuja (ef_at_df.com)
Date: 09/21/04 

Date: Tue, 21 Sep 2004 15:47:28 +0530

jmm <jmeyer@pax.ch> wrote:
> Madhur Ahuja wrote:
>> jmm wrote:
>>
>>>>> Could I really use NAT on W98?
>>>>
>>>>
>>>> Why do you want to use NAT. NAT is basically used for Internet
>>>> sharing within a LAN.
>>>
>>> Yeah, because I'll use two differents IP subnet (ISP + LAN) and I
>>> don't want that other guys in Internet know my own IP subnet and
>>> address from my Intern LAN :-)
>>
>>
>> This is completely incorrect. They are completely different networks
>> and no one from outside will able to peek into your LAN network. Be
>> sure, not to enable services like File sharing on the modem network.
>
> You tells me that is completely incorrect! Do you known something
> about routing, networking and so on?

Sure, I am a computer Engineer and have studied networking.

> When you send a packet from one network to Internet thru your ISP,
> your origin IP Address travelled to Internet.

This is where you are mistaken. When you send a packet from your lan network
to the internet. The source of the packet will not contain your LAN IP like
192.168.0.1 but instead the IP which is used by the computer for connecting
to
the Internet. This technique is performed by the Network Address
Translation(NAT).
This is not a technique to hide the local network address , but NAT is there
since
this is the only way to access Internet from the local LAN.

This is because if the packet will contain source address as
192.168.0.1(which is a class
C address), upon reaching to the Internet, the internet will try to send the
destination
packet to 192.168.0.1, however the address 192.168.0.1 is only local to your
LAN and not to
the Internet(since it doesnt uses class C addresses). Thus the packet wont
reach its destination
and you will not be able to connect to the internet.

> NAT is using to hide
> your origin IP Address. With the routing technologies we have the
> possibilities to known all IP Address in Internet (I means, all IP
> Address not protected by Firewall and NAT).
>

Read a few sites on NAT, or post here if you need more information. 

--
Madhur Ahuja [madhur<underscore>ahuja<at>yahoo<dot>com]
Homepage
http://madhur.netfirms.com

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