title: How to design a web service exclusively for multiple LANs?
body: <p>Lets say I have three independent LANs and a central server somewhere. I want to offer a service exclusively to users on those LANs (via internet ofc). And a slightly different service to different LANs: users on LAN "A" should recieve content "A" and only "A". Can this be achieved by some sort of IP filtering on the server side (like checking the source address) and how secure is that? Or with RSA (or something) keys: can a router (on a LAN) be configured so it can communicate with the server in a secure way?</p>
  
  <p>Basically I want my server to only be visible for users that connect to internet through certain routers (LANs), and for each LAN offer a slightly different service.</p>
  
  <p>I would greatly appreaciate any advice on how to achieve this, since I'm not an expert :)
  Also I hope that this kind of a question is ok to ask here, since it is not strictly a programming one.</p>
  
  <p>Regards, Petar</p>