LAN Load Balancing Router

Question

Everything I find is for WAN load balancing. Our customer wants to have a setup where two servers are connected to the same router. To the outside network devices connected to the router, they think they are talking to the server directly. The idea is if one server goes down, then it fails over to the other server. The servers also need to have internet access through the same router, so the router is the gateway. The traffic from the network devices external to the router would need to be forwarded to a certain port on the servers. Each server would have a different IP address of course, but both communicate on port 1024 to the network devices.

Does a LAN load balancing router exist that can do this?

Answer 1

Well, load balancing and 'failover capability' are two different things. The Windows Server OSes have failover cluster capability, which is what you should use. The following is taken from here:

A failover cluster is a group of independent computers that work together to increase the
availability and scalability of clustered roles (formerly called clustered applications and 
services). The clustered servers (called nodes) are connected by physical cables and by software. 
If one or more of the cluster nodes fail, other nodes begin to provide service (a process known as failover). 
In addition, the clustered roles are proactively monitored to verify that they are working properly. If they are not working, 
they are restarted or moved to another node. 

Update

For custom software, I would recommend using at least two HyperV nodes in a failover cluster. Each one can have a virtual machine tied to the cluster that has your software installed. Without recoding the app, if the primary vm goes down, and can't be reached by the other(s), the other node will take over. See this example.

Answer 2

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.

1. 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.
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 99.12.34.0.
3. Now when someone connects to that external IP address, the router will know to route all traffic from 99.12.34.0 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.

Answer 3

Your client is asking for server load balancing, and there are a number of hardware and software solutions to implement that behavior, if you use those words in a search, the options are numerous.

Answer 4

You can forward traffic from your router to a load balancer virtual IP (VIP) and the LB will balance the load on your internal servers.

[Router]

192.168.1.10 
     |
[Load Balancer] (Kemp, F5, cisco, or zen load balancer)
   |      |
[Srv1] [Srv2]