This is what i got from the documentation:
Use Ldap User authentication
Turns on LDAP authentication and tells the XAS it can use this configuration file (you may specify multiple LDAP servers which will be checked for authentication recursively).
Let me give an example of what I mean. When I define one LDAP server, and when that server is down for whatever reason, the sync will fail. Can I add an alternative/second server (2nd domain controller in the same domain as the first) so the sync can use that one as backup. Or should this high-availability requirement be solved at DNS level or similar to ensure that there's always a server in the pool to connect to?
It should be solved at another level indeed. Multiple LDAP servers are available to import data from multiple ldap providers, not for failover purposes.