TNS-12543: TNS:destination host unreachable
Scenario : Setting up a physical standby from Exadata to a non-Exadata single instance. tnsping from standby to primary works fine but tnsping from primary to standby fails with: [sql]TNS-12543: TNS:destination host unreachable[/sql] I am able to ssh standby from primary, can ping as well but tnsping doesn’t work. From the error description we can figure out that something is blocking the access. In this case it was iptables that was enabled on the standby server. ...