From v5.0, WIspr redirection is responsible AP.
There If SZ goes down, AP can failover by himself.
1) Web portal failover.
When you configure secondary external URL on Hotsport setting, AP will periodically send request to primay URL. (per about one minuete.)
If Primary URL is not reachable, AP redirects request to secondary.
It's WEB portal failover.
It's so cool function.
2) WISPr
failover
If you configure auth/acct server as proxy mode, you can backup auth/acct server.
The server is worked as non-proxy mode at AP when ssh tunnel with SZ is disconnected(not reachable).
If ssh tunnel with SZ is recovered, AP work via normal auth/acct server(primary server as proxy mode).
It's so amazing function.
3) AAA server failover
It's originally worked at AAA profile using primart/secondary server.
4) Modified HTML form code.
You have to modify POST action like below.
*as is :
document.write('