If you use localhost to access Redmine, that means that the application is using the 80 port in your machine. The easiest way to forward the ports is to use the external 80 port of your router and forward that information to the 80 port of your machine. This way, you will only need to type the public IP of your router when accessing the application from outside.
No, you do not need to change any values in the default Bitnami installation.
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