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Making internal LAN ip addresses changes

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If you change the subnet inside your router, there is very little to change to get things working again. Things that need to be changed are:
  • the accepted IP range in the postgres pg_hba.conf file
  • the accepted IP range in Apache's httpd.conf file
  • internal DNS setting to find the apache server

1. Changing the postgres pg_hba.conf file

This file is found in the postgres 'data' directory. On a PC, you can edit it with notepad. On a Mac, you might need to use 'vi' to edit the file while acting at the postgres user. You need to change (or add) a subnet range that allows people to access the database from the new IP range and/or remove the old one.

Once the subnet has been changed, you need to reload the postgres configuration. You do this by stopping and restarting the server, or if you are familiar how to do so using pgAdmin interface on the PC or the command line on the Mac, you can do it that way.

2. Changing the Apache httpd.conf file

The apache httpd.conf file is found in the 'conf' directory of the apache folder. On both Mac and PC, it can be altered by any text editor. Near the bottom is a setting that says:


Change the ip address range here according to the instructions in the conf file.

After, restart apache and test that it works by typing one of the following in a browser on the machine that Apache runs on:

If you do not get a response, Apache is not running and you will have to determine why it is not.

3. Changing the internal DNS server or Hosts file

For Mac listeners, there is nothing further to do. On PC networks, you many have to reset some internal DNS entries so that it points to the new computer.

For example: suppose that the setting TM is looking for is but it can't be found by machines inside the network.

  • Outside the network, anybody can find because the external DNS services point it to your router.
  • Inside the network, getting things to point outside can be troublesome. the internal DNS setting for needs to point to where the apache server is at this time... at the new IP.
  • You can do this in two ways:
    • if you have DNS server set up on your IIS server, change the entry for
    • if you do not have a DNS setting, you need to edit the 'hosts' file on each machine that is acting as a listener or needs access to the web listener. Typically, that is in the /windows/system32/devices/etc folder, or on the Mac, it is in /etc
For example: if the Apache server is at, then you need an entry in the hosts file that points to If you are changing the IP address, then you will likely notice an entry for the old IP which needs only changed.

If the hosts file was edited, and you decide to implement an internal DNS server, you will have to clear the entry out of the hosts file on each computer that it was put on. .