I'm not using RADIUS as a backend for ISP gear. I am using a RADIUS proxy to serve requests for service software, and when false failures come back, customers get error boxes in their software and contact our support angry that our authentications are returning transient errors. Furthermore, I consider it bad public face to return errors to customers when they should not get them. Yes, customers can always retry, but we can also retry for them when know the reason is not due to invalid information.
I think that you are going about it the wrong way. You wont proxy to pretend that home server has not gone down. How about this - instead of a group of stand-alone load-balanced home servers create a (true) high availability cluster. If your home server is always available this issue doesn't come up. And your customer always gets a response. Ivan Kalik Kalik Informatika ISP