[MLB-WIRELESS] MW Intranet DNS & Redirection

Tony Langdon tlangdon at atctraining.com.au
Thu Nov 20 15:46:27 EST 2003

> -----Original Message-----
> From: Dan Flett [mailto:conhoolio at hotmail.com]
> Sent: Thursday, 20 November 2003 15:05
> To: Melbourne Wirless
> Subject: [MLB-WIRELESS] MW Intranet DNS & Redirection
> On a related topic, I run an access point at my node with 
> DHCP.  From looking at the leases log I see that I get the 
> occasional visitor assocating with my AP.  I'm pretty sure 
> that these visitors are either my neighbors' home computers 
> associating by accident, or wardrivers looking for Internet 
> and home networks to probe.  I'm thinking that once they 
> associate, they probably think they have Internet access.  So 
> when they're connected they're going to type something like 
"www.google.com" into their browsers.  And they're going to get a 404 error.

Actually, they won't.  They'll get the "Host can't be found" page, unless
you have DNS working

Is there some way to redirect these requests to my local web page at or any other web page of my choosing?  All these chance
associations that people are having with my AP are a great chance to spread
the word about Melbourne Wireless and the network.  But I don't think any of
them are going to go to the trouble of looking at the default gateway that
my DHCP gives them and then typing that address into their browser.  Instead
of a 404 I want them to see a web page that explains why they're not seeing
Google and tells them what the Melbourne Wireless Intranet is.

The answer is "it depends".  If they can resolve an IP address (any old IP
address will do), and you have a Linux (or *BSD) web server sitting
somewhere on the default route from the client network, you can do it.
Simply run a copy of Apache as you normally would.  Make both indec.html and
the 404 error document the page you want to show the user, and finally,
setup transparent proxying in iptables (or equiv), so all port 80 requests
not destined for 10.x.x.x are redirected to the localhost.

So, if DNS is working and external addresses can be resolved, yes you can do
it, but if DNS is not working, it's not gonna be so easy.  You could try a
bogus DNS server with wildcard records for .com, .org, etc, all pointing to
your web server. :)

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