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Going out and coming back in ....

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by kaspencer

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I have noticed that different routers behave differently on my network.

Let me explain ...

I have a couple of Windows 2k3 servers on my network, and I quite often do data-driven web development on one of them. Of course I can access the server over my local network by its name or IP address. So, I can type its local IP address, e.g.:
http://10.0.0.123/web-app-name
and can test my web application in a browser on a workstation on my network.

However, sometimes I wish to go out from my network, onto the Internet at large, and come back into the server, via my router, which is configured, using NAT/Port redirection to direct HTTP packets at my server.

So, if my external IP address is 123.123.123.123, I expect to be able to type
http://123.123.123.123/web-app-name
and get into my server by that rather circuitous route.

OK, so here is the question:

All the Belkin routers that I have ever had, permit this to be done.
Very few other makes of router permit that.

Does anyone know why? Can anyone explain to me what I need to do to make it work on all router?

Just for info: regardless of which router I use, the server is available if I try to access it via my external IP address BUT via another network rather than my own - e.g. if I log in on my laptop by diallup.
Also my clients can access my server via their networks regardless of which router I use.

Hoping for some enlightenment!

Kenneth Spencer

3 replies

by robo_dev

It's usually just a matter of opening the appropriate port in the firewall, and assigning the IP addresss of the server to the NAT table.

This can be done in my Netopia or Netgear router/firewalls.

The only tricky bit can be if you are trying to use the DNS name of the server. But if you're using the IP address, that should work wthout a problem.

Which ones have you tried??

by kaspencer

Thanks Robo_dev, but all the necessary ports and NATs are properly configured (otherwise of course I wouldn't be able to get onto the server applications from anopther network.)

This feature, present in some routers but not in others, I have dioscovered is known as "hairpin routing". It seems that not all routers do it - in fact it seems rather few of the lower cost devices. I was just wondering whether anyone knew more about it.

Thanks

Ken.

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