TACACS / LDAP / RADIUS server shown as Down on Dashboard:
Configuration==>Authentication==>Dashboard==>Status shows as "“Down:Server is not reachable”  .
However functionally there are no issues, and authentication is works fine

 

This is due to a bug, issue ID#654375, it has been addressed in the following builds.
11.0 71.X or higher, expected release 20th Sep 2017
12.0 53.X or higher, released
11.1 55.X or higher, released
 

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Problem Cause

If the passphrase contains the "at" special character (@), test connection performed on LDAP server fails, and the dashboard shows that the LDAP server is down.