环境：
[grid@rac1 ~]$ cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 localhost.localdomain localhost
::1 localhost6.localdomain6 localhost6
# Public
192.168.2.101 rac1
192.168.2.102 rac2
# Private
192.168.0.101 rac1-priv
192.168.0.102 rac2-priv
# Virtual
192.168.2.111 rac1-vip
192.168.2.112 rac2-vip
# SCAN
192.168.2.200 rac-scan
现象：
在windows客户端sqlplus工具使用scan的IP无法连接，报错如下：
C:\Users\WJW>sqlplus system/qweasd@192.168.2.200:1521/orcl
SQL*Plus: Release 11.2.0.1.0 Production on Thu May 17 12:35:28 2012
ERROR:
ORA-12545: Connect failed because target host or object does not exist
检查各组件状态，正常：
[grid@rac1 ~]$ crs_stat -t
Name Type Target State Host
------------------------------------------------------------
ora.DATA.dg ora....up.type ONLINE ONLINE rac1
ora....ER.lsnr ora....er.type ONLINE ONLINE rac1
ora....N1.lsnr ora....er.type ONLINE ONLINE rac1
ora.asm ora.asm.type ONLINE ONLINE rac1
ora.eons ora.eons.type ONLINE ONLINE rac1
ora.gsd ora.gsd.type ONLINE ONLINE rac1
ora....network ora....rk.type ONLINE ONLINE rac1
ora.oc4j ora.oc4j.type ONLINE ONLINE rac2
ora.ons ora.ons.type ONLINE ONLINE rac1
ora.orcl.db ora....se.type ONLINE ONLINE rac1
ora....SM1.asm application ONLINE ONLINE rac1
ora....C1.lsnr application ONLINE ONLINE rac1
ora.rac1.gsd application ONLINE ONLINE rac1
ora.rac1.ons application ONLINE ONLINE rac1
ora.rac1.vip ora....t1.type ONLINE ONLINE rac1
ora....SM2.asm application ONLINE ONLINE rac2
ora....C2.lsnr application ONLINE ONLINE rac2
ora.rac2.gsd application ONLINE ONLINE rac2
ora.rac2.ons application ONLINE ONLINE rac2
ora.rac2.vip ora....t1.type ONLINE ONLINE rac2
ora.scan1.vip ora....ip.type ONLINE ONLINE rac1
检查监听器状态，正常：
[grid@rac1 ~]$ lsnrctl status
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 17-MAY-2012 13:27:40
Copyright (c) 1991, 2009, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.1.0 - Production
Start Date 17-MAY-2012 12:19:51
Uptime 0 days 1 hr. 7 min. 50 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/app/grid/network/admin/listener.ora
Listener Log File /u01/app/oracle/diag/tnslsnr/rac1/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.2.101)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.2.111)(PORT=1521)))
Services Summary...
Service "+ASM" has 1 instance(s).
Instance "+ASM1", status READY, has 1 handler(s) for this service...
Service "orcl" has 1 instance(s).
Instan