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2 posts

Wannabe Geek

Topic # 17284 19-Nov-2007 17:58
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Currently we have a ADSL connection provided by Xtra that has a static IP address. 

We have a Netgear ADSL Modem/Router which redirects port 80 on to a computer on our LAN, now I have been asked to have point to another computer on the LAN. Now my understanding of ADSL modems (especially lower end models) don't seem to be able to do this with NAT, we would have to redirect port 8080 to the other computer or is there another way?

I'm assuming we will have to move to fibre or is there another way?

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95 posts

Master Geek

  Reply # 96002 19-Nov-2007 20:01
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As far as the Internet is concerned you only hape one IP address so all services will come to that one address, regardless of DNS pointers.  Only one device can listen on one port.

The easiest way might be to use a different port as you have suggested.

If this is just for a different web server then you could possible address this using a "host header" on the original server to capture the fact that the request was for and redirect to  Only one page and reasonably transparent to the user.


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Ultimate Geek


  Reply # 96009 19-Nov-2007 20:41
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Second IP address routed to you or a device with some smarts to redirect based on http layer.


2 posts

Wannabe Geek

  Reply # 96035 20-Nov-2007 07:26
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We are currently running a consumer ADSL modem - which ADSL modems start to have the smarts to read host headers - at the moment the adsl router can only forward port 80 to one machine no matter what the subdomain is requested.

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Master Geek

  Reply # 96040 20-Nov-2007 08:23
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The key is not for the ADSL router to read the host header but the your original web server.  Both DNS entries will point to the same IP address and so port 80 will be redirected to the same web server.  That web server can then detect the domain via host-header and use a different virtual server (ie. different Home folder). 

By using a different virtual server you have a different "site" even though it has the same IP address.

Now, if you want that different site / domain to be run from a different box then you need to use a different port such as 8080. 

In this case setup the main server to have a different virtual server for the second domain and have it do a redirect (meta refresh page) to forward the request back to the same IP / DNS but to port 8080.  That port can have a pinhole to the second web server.


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Ultimate Geek
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  Reply # 96050 20-Nov-2007 10:21
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Technically speaking there is nothing preventing the use of multiple IP addresses on a DSL connection.  Xtra choose not to offer this as a product offering.

Have you tried talking to any of the more technically/business focused ISPs (e.g. Xnet/Iconz/Maxnet) and seeing if they can offer a routed subnet over UBS for you?  This would allow you to have multiple public IP addresses.

The alternative, as proposed, is to forward 80/tcp to a reverse http proxy which will allow lookups based on the Host: header to forward to internal webservers based on that.  Of course, this will not work for ssl (https), if that ever becomes a requirement.

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Ultimate Geek


  Reply # 96143 20-Nov-2007 21:31
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Or you could tunnel the traffic in from an external device, not very practical though.

I would also suggest talking to someone clueful at a tier 2 ISP to get additional IP addressing on your UBS connection. If you want feel free to PM me and I can sort something out for you.

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