Redirect domian and/or subdomain to a specific path on an internal webserver

My objective is to combine path-specific routing with domains & subdomains.

I have a web server internally that hosts two separate sites:

• One site at http://192.168.100.100 (or http://internal.hostname)
• A second site at http://192.168.100.100/mysite (or http://internal.hostname/mysite)

I want to know how to redirect requests (internal & external) for a specific domain/subdomain to a specific path internally.

So for example:

1. A request (internal or external) to http://domain1.tld should redirect to http://192.168.100.100/mysite (or http://internal.hostname/mysite)
2. A request (internal or external) to http://mysite.domain.tld should redirect to http://192.168.100.100/mysite (or http://internal.hostname/mysite)

Is this possible?