The SQL*Net client by OracleTM uses IP and hostname to establish a connection to the server. Since these parameters can be different behind the firewall, the parameters have to be translated by the ora firewall plugin. The plugin analyzes the data stream of sqlnet sessions. You can configure the ora plugin to do the following actions:

• The plugin must create an acceptor for the expected dynamic session, and also must rewrite the hostnames or IP addresses to proper values if destination address translation is used. Therefore, the plugin can be configured with hostname rewriting parameters that allow replacement of hostnames or IP addresses in the server response. 

• The plug-in syntax allows various patterns which may be replaced with the intended addresses. Optional, a target address may be specified if a specific target IP address where the SQLNET session is to be connected to is required (SQLNET load balancing between oracle servers). 

In the following example scenario, the correct plug-in setting is ora hostname2=192.168.10.2. 

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Since TNS structures can operate with different servers and hostnames you can use patterns for the hostname. Since the communication also involves a port change the plugin has to be used in any case. The hostname2=hostname1 or hostname2=hostname1, IP1 part is mandatory and must not be omitted. If database farms are used, the hostname=IP or hostname2=hostname1, IP entries must be a space separated list.