On Thu, 12 Mar 2009 13:26:45 -0700
Grant <emailgrant@...> wrote:

> I travel with a strong external antenna for picking up faint wireless
> signals.  It works great, but my girlfriend struggles to connect with
> her built-in antenna.  I do have a travel router (D-Link DWL-G730) so
> I'd like to be able to do something like this:
 
> WAN->my laptop->travel router->girlfriend's laptop

That sounds right to me.  Read on...

> I use wicd and I'm not sure how to go about this, especially since my
> laptop DHCPs for an IP from the WAN so I'm not sure how to define the
> gateway for the travel router when following this:

I don't have experience with wicd or the DWL-G730, but I did do a
little research on those and have suggestions.  

If I were setting this up myself it would be with another Wifi card in
AP mode, which I'd be running DHCP on.  In that case, the client (in
this case your girlfriend's laptop) would be given a DHCP address and a
default route of my AP's address.  Alternately I might forego the DHCP
server setup and instruct the client to set a particular IP and route
(the route would be my AP's IP).  In either case, nameservers could be
copied directly from "my laptop" to the client's, or "my laptop" could
supply its own IP for nameserver and provide DNS service or proxy
itself.  

"My laptop" would then have a route through the AP for internal traffic,
and use the (dhcp provided) default route for other traffic.
Therefore, the AP would never need to specify the IP of the external
connection.  

The client box would route all traffic through the AP's IP so it
wouldn't need to know the external IP either.  

"My laptop" would have to run IPTables for NAT.  You'll need network
address translation because external IPs like websites won't be able to
route to the client box's IP.  NAT gets around this.  

The AP provided by "my laptop" must also be on a different subnet than
the external network "my laptop" is connected to.  If "my laptop" was
connected to an access point offering a 192.168.1.0/24 subnet, for
example, a seperate subnet like 192.168.2.0/24 ought to be used on the
"client side" of "my laptop".  Personally I'd probably use an rfc class
b subnet since they're rare, or another rare subnet like
192.168.66.0/24.  

> http://www.gentoo.org/doc/en/home-router-howto.xml
> 
> Is there a simple way to pull this off?

In short, no, but it's not too complicated, and the home router guide
will help you, but using your travel router may make things more
complicated.  The travel router probably will itself provide NAT and
DHCP so I'm not sure without playing with one how it would look to set
it up that way.  You might want to provide those services yourself and
use the travel router as an AP instead.