多次运行nslookup RACSCAN.localdomain.可观察到scan-ip轮询没有任何问题，反向解析亦没有任何问题。
4. Ping三个scan-ip没有任何问题：
primary$ping 10.134.30.47
PING 10.134.30.47 (10.134.30.47) 56(84) bytes of data.
64 bytes from 10.134.30.47: icmp_seq=1 ttl=63 time=0.508 ms
primary$ping 10.134.30.48
PING 10.134.30.48 (10.134.30.48) 56(84) bytes of data.
64 bytes from 10.134.30.48: icmp_seq=1 ttl=63 time=0.522 ms
primary$ping 10.134.30.50
PING 10.134.30.50 (10.134.30.50) 56(84) bytes of data.
64 bytes from 10.134.30.50: icmp_seq=1 ttl=63 time=0.514 ms
5. 在任意客户端测试可否登陆：
primary$tnsping guijian
TNS Ping Utility for Linux: Version 11.2.0.1.0 - Production on 02-JAN-2014 19:12:15
Copyright (c) 1997, 2009, Oracle. All rights reserved.
Used parameter files:
/u/app/oracle/product/11g/db/network/admin/sqlnet.ora
Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = RACSCAN.localdomain.)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = RACDB)))
OK (0 msec)-------------------------à此处透过scan-ip的tnsping正常
primary$
primary$sqlplus scott/Testpassword@guijian
SQL*Plus: Release 11.2.0.1.0 Production on Thu Jan 2 19:08:06 2014
Copyright (c) 1982, 2009, Oracle. All rights reserved.
ERROR:
ORA-12170: TNS:Connect timeout occurred
primary$
等待N久之后提示超时，但此时的tnsping正常，起初测试也曾提示提示 no listener。
6. 检查监听器配置：
[grid@RAC01 admin]$ cat listener.ora
LISTENER_SCAN3=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN3)))) # line added by Agent
LISTENER_SCAN2=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN2)))) # line added by Agent
LISTENER=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER)))) # line added by Agent
LISTENER_SCAN1=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))) # line added by Agent
LISTENER_SCAN1=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN2)))) # line added by Agent
LISTENER_SCAN1=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN3)))) # line added by Agent
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER_SCAN1=ON # line added by Agent
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER_SCAN2=ON # line added by Agent
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER_SCAN3=ON # line added by Agent
ENABLE_GLOBAL_DYNAMIC_ENDPOINT_LISTENER=ON # line added by Agent