It’s not clear from your wording what software or what approaches you have made to dealing with this but when you say, “Everything I find is for WAN load balancing,” that is part of the problem.
There is no such thing as WAN specific or LAN specific load balancing. It’s all dependent on configuration & options. I recommend a software load balancer such as Apache running
mod_proxy running on some flavor of Linux like Ubuntu. So if I were to recommend a way of handling this, I would suggest the following.
- Your customer has two servers behind a router, right? Let’s say their IP addresses are 10.10.10.1 & 10.10.10.2. Okay, now you need to add a 3rd server which will be the load balancer & let's give that machine the IP address of 10.10.10.0. Configure it as it should with 10.10.10.0 load balancing to 10.10.10.1 & 10.10.10.2.
- Make sure the load balancer has an external IP address on the router that will direct outside world traffic to 10.10.10.0. Let’s say that external IP address is 126.96.36.199.
- Now when someone connects to that external IP address, the router will know to route all traffic from 188.8.131.52 to 10.10.10.0. And then 10.10.10.0 will route to 10.10.10.1 & 10.10.10.2 depending on need.
That should solve the issue.
But if you are looking for a hardware solution, it might be the same basic architecture but with that hardware router being the replacement for the Apache server running
mod_proxy. In my mind that is six of one, 1/2 a dozen of another. Your choice.
But in general network architecture of a WAN versus a LAN should not be a factor.