Redirect to offsite server during downtime

[ephigenie]

In this Cases i'd use the advanced features of my cisco / juniper and just redirect all incoming http traffic offsite.
Thus if your entire facility is down - all your panel-server are down as well - so you can't even switch to another facility / backup server if you'd like to - because its too late.

If you have external dns servers available it should be easy to just return only 1 ip for every request - redirecting your traffic to your backup site. Of course with very low ttl (180s i.e.)
But as rbtux already pointed out - if your ttl was actually 86400 before - then it'll take up to 1 day until everyone gets redirected - and then hopefully your already up & running at your main facility.