Listener Parameter File   C:\oracle\product\10.2.0\db_1\network\admin\listener.ora

    Listener Log File         C:\oracle\product\10.2.0\db_1\network\log\listener.log

    Listening Endpoints Summary...

    (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=rmesvr34.cn.ibm.com)(PORT=1521)))

    Services Summary...

    Service "PLSExtProc" has 1 instance(s).

    Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...

    Service "irmdb" has 1 instance(s).

    Instance "irmdb", status READY, has 1 handler(s) for this service...

    Service "irmdb_XPT" has 1 instance(s).

    Instance "irmdb", status READY, has 1 handler(s) for this service...

    The command completed successfully

    6.在客户端(9.123.112.16)分别再次使用tnsping命令和sqlplus命令来验证数据库的连通性：

    C:\Documents and Settings\Administrator>tnsping irmdb

    TNS Ping Utility for 32-bit Windows: Version 10.2.0.3.0 - Production on 06-APR-2010 11:09:20

    Copyright (c) 1997, 2006, Oracle.  All rights reserved.

    Used parameter files:

    C:\oracle\product\10.2.0\db_1\network\admin\sqlnet.ora

    Used TNSNAMES adapter to resolve the alias

    Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)

    (HOST = 9.123.112.34)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = irmdb)))

    TNS-12537: TNS:connection closed

    C:\Documents and Settings\Administrator>sqlplus /nolog

    SQL*Plus: Release 10.2.0.3.0 - Production on Tue Apr 6 11:09:23 2010

    Copyright (c) 1982, 2006, Oracle.  All Rights Reserved.

    SQL> conn irmadmin/passw0rd@irmdb

    ERROR:

    ORA-12537: TNS:connection closed

    到这里我们就可以证明，通过修改sqlnet.ora的方法，我们实现了限制指定机器IP访问数据库的功能。

    最后需要特别注意的是tcp.invited_nodes允许列表的优先级要高于tcp.excluded_nodes受限IP列表。也就是说如果同一个IP地址如果同时出现在两个列表里的话，那么这个IP地址还是可以访问对应的数据库的。