Subject: RE: Having trouble understanding how routing works with Linksys r outer

From: "Joe Aiello" <[email-masked]>
Date: Wed, 11 Jul 2001 17:05:15 -0700

The intention of the broadband routers are not to allow inbound access to
the private LAN as much as they provide simple NAT and link sharing for the
private LAN to The Internet.  However, the Linksys happens to have some
features that allow you to pass some addresses, create a DMZ, etc.  One
feature most folks are unaware of is that the Linksys will route inbound
quite well.  The caveat is that folks must be on the same public subnet as
you. They will not be able to route across public routers to addresses on
your private LAN.

Before I get to that, most broadband routers allow you some NAPT (Network
Address Port Translation) for inbound connections.  For example, if you are
running a web server on a PC on the private LAN on PC 192.168.1.10, you can
configure the Linksys to forward requests that come into the ISP assigned IP
address (that is configured as the WAN IP address on the Linksys) on port 80
to port 80 on 192.168.1.10.  You can add some of your own as long as you
know the TCP or UDP ports the game server is using. 

OK, the Linksys will also route to addresses on your private LAN from folks
on your public subnet.  All they have to do is add a route on their system
for the addresses on your private LAN.  So, if you are 198.179.201.10 anyone
on 198.179.201.xxx can put a route in their broadband router or PC to access
the 192.168.1.x addresses on your private LAN through 198.179.201.10.  This
works great.  This rarely known feature allows folks to access any PC on
your private LAN through the Linksys.  Again, they have to be on the same
public subnet since the ISP routers will not forward the 192.168.1.x (for
example) to your Linksys.  Note: personal firewalls should be on each PC
behind the Linksys.  Note 2: Not all broadband routers act this way.

Joe Aiello
System Engineer
Sylantro Systems
http://www.sylantro.com/
VoIP Polls
408-626-3032

 -----Original Message-----
From: 	Chris Chapin [mailto:[email-masked]] 
Sent:	Wednesday, July 11, 2001 3:51 PM
To:	DHCPv4 discussion list
Subject:	Having trouble understanding how routing works with Linksys
router

Hey,

I'm new to the list - hello everyone.

Ok here's the scenario.

I subscribe to broadband through a cable modem.  I have purchased only 1 IP
address from the cable company.  But of course I have more than 1 computer
at my home that I want to connect to the internet simultaneously, so
naturally I need more than 1 IP address.
So I bought a Linksys router, enabled DHCP and boom everyone on my LAN has
an unique IP address.
But no one on the WAN could ever send a packet to the Linksys assigned IP
addresses on my LAN.  WAN people can only send packets to IP address given
to me by my cable company.

So my question is - how do packets get delivered to the correct computer on
my LAN when they come in from the WAN?

At first I thought that maybe the router would just broadcast the data to
all the attached interfaces, but that wouldn't work for people playing the
same game online but in different servers.

I have been unable to discover or figure this out on my home.

Could someone please point me in the right direction?

Thank you,
Chris