I have LAN setup with public server on it. The server is accessible via domain example.com. If I access example.com from within lan, it goes over my ISP. I wish it went just over my local network. Hosts file is not an option, sice most pcs are mobile and will access server both from within lan and over the internet. 

The question is, are there routers capable of such redirection (low-cost, up to 50€) even if it means reflashing firmware with for example dd-wtr or is it posilble with local dns server? Or is there any completely different way?

![enter image description here](https://i.stack.imgur.com/JFW2w.jpg)