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I currently use rackspace cloud servers. Here's the part of the FAQ that talks about them:

So I'm assuming that even aside from the fact that the bandwidth is "unmetered", that it would be way faster if I have a web server and separate database server, if I could use the "internal ip".

Is that possible? Instead of using the hostname as localhost or a public IP address to contact a database server, to use the internal IP? And would that be beneficial? And how can I find out my server's internal IP addresses?

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up vote 1 down vote accepted

The internal address will go at the speed of the connection between machines instead of having to go out to the edge router and then back into the network. You can also set up various daemons to be listening on an internal address only, thereby (slightly) increaasing security.

You can find the various IP addresses on a Linux machine via the ifconfig command.

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Ok, so when I run that command, I get the info that I need (I think). But how exactly would an application know it's an internal IP, you know? Does it matter to it? – Matthew Sep 25 '10 at 19:39
The application wouldn't have to know. The OS knows which address/interface to route packets to based on the destination address (netstat -nr), and the daemon's configuration tells it which addresses/interfaces it should listen for packets on (e.g. Listen for httpd, ListenAddress for sshd, etc.). – Ignacio Vazquez-Abrams Sep 25 '10 at 19:43
So do you think I need to edit anything? I can of course try it out to see, but generally will it just work? – Matthew Sep 25 '10 at 20:00
The only thing you'd need to edit is the configuration of the apps in use. They'd have to connect to the internal address of the other machine instead of the external address. – Ignacio Vazquez-Abrams Sep 25 '10 at 20:10

Some tips: If you are using MySQL, check your my.cnf. In that file, you can set your listen IP/port Same happend with Apache in httpd.conf

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