I need some help with setting static routes on a TL-ER7206 firewall / router with Load Balancing enabled.

I may not be thinking the right way about setting a static route to a specific IP address though only 1 of the 2 WAN (ISP)

I am a member of a community that has a P2P file sharing app that we can download and become a client to provide storage and redundancy for the site's global file sharing (not BitTorrent).

The client checks in with the site’s servers periodically (once or twice a minute) using HTTP to make sure the site knows the client is online and its content is consistent.

When the client's account is created, the site will note the client's IP address (the ISP's modem IP address is used) and that becomes part of the client's authentication for every HTTP transaction.

The issue is that with ISP load balancing set up in the ER7206, the ISP address will naturally flip-flop between the ISPs per the ER7206's routing algorithms. Because the site's server doesn't see a consistent ISP address, it never allows my client to join.

Adding to that issue, there are 6 to 10 HTTP servers that the site rotates through randomly (I have all of their IP address logged).

The issue is that in the ER7206, I cannot enter in a static route for a specific IP address - only subnets.

Example:

One of the site's servers is 37.48.81.116

But, a subnet calculator shows that with an IP of 37.48.81.116 and a subnet mask of 255.255.255.248, the network is 37.48.81.116 and the 1st usable address is 37.48.81.117 with 8 host IP address (.117 to .222).

If I open it up to 255.255.255.240, the network is .208, the 1st useable is .209 with 16 host IP addresses (.209 to .222)

In static routes (Transmission > Routing > Static Routes) the ER7206 asks for:

Destination IP: 37.48.81.116

Subnet Mask: 255.255.255.240

Next Hop: 47.143.206.1

Interface: (WAN or WAN/LAN1) <- WAN is the interface I need to route all outbound traffic though to authenticate with the site's HTTP server. It has the ISP's IP address.

Using these details, the Destination IP address changes to 37.48.81.208 when I save it.

The smallest subnet that can be created is using a subnet mask of 255.255.255.252. But the first usable address is still .117.

I know my client setup is works because when I disable the WAN/LAN1 (the 2nd ISP - and slower) interface, everything is happy and the site shows my client is online and all good.

But that defeats the point of load balancing and failover of two ISPs