Suddenly can not connect to our Acitive Directory server.

Question

ColdFusion code that was running fine this last Friday, for nearly two
years before then, is suddenly throwing this error today "Connection to
LDAP server failed".  The Active Directory is up and responding to pings
and all normal windows logons are being preformed properly.  But neither
ColdFusion nor my Softerra LDAP Browser can make a connection with
multiple user names.
Can anybody provide a short list of what could have been changed that
would of started this problem?

Answer 1

The server was not responding to anything, accept pings, as best as we could tell.
Since this was affecting production applications, preventing empoyees from duing their work, the box was booted.  The sys admin had to physically walk up to the server room as he could not even remote into the system.
I am now told that there are three active directory servers sharing the load in our organization.  I'm guessing it is possible that the windows login operations where failing over to another of the trio.  But that the CFML code, that is hard coded to a specific one of the AD servers, could not do this.
If this is a common set up, I have to research the details more, is there some way to tell ColdFusion to make to a connection to any of the three AD servers, whichever one is availaible.  Or do I need to create my own fail over code using try-catch blocks, or some other exception handling choice.  Basically code it to try server A, if that does not work, try server B, if still a problem try server C.
That later is not hard code to visualize, but it seems to be very dependant on the exact network configuration.  Whereas, if there was some way to query all the available AD servers as a clustor, then I presume the network folks could swap servers into and out of the clustor without really affecting our code.  That would by my hope anyway.