Force certain DNS or IP requests to use a different gateway

I forgot to mention there is a Cisco ASA 5510 on each side of the VPN tunnel.

Does this affect many websites at Site A?

If so, check your AD is setup properly - subnets in sites and services, etc.

Do your PCs go through a proxy server to get to the internet? If so, you may be able to use this to redirect for that URL.

As far as the routers go, you would need to know what the IP address is and put a route in.

Does this affect many websites at Site A? No. Just one website in particular. Has been this way ever since switching from Comcast to Fiber. We are almost to the point where we are going to assign an entire new IP block to the customer because of this. We contacted the ISP for fiber and this is what they said:

"There appears to be some odd issue with their IP block not liking that website or vice versa. I tested it on a different block but same Class C range and it works just fine. However, when I narrow it down to their IP block, it takes about a minute to load that one page. Would your customer be opposed to getting a new set of IP's to remedy this issue? This is one of those bizarre issues where I think troubleshooting would be very tricky and it would probably have to involve another ISP as well."

When you ask "As far as the routers go, you would need to know what the IP address is and put a route in.".... what IP address would I need to know? The IP of the website? The IP of....?

There is no proxy server....and, I'd like to say AD is set up just fine. There's got to be a way to make requests for this website go out the tunnel instead of the gateway at Site A.