Oracle Database listening is very slow, and hang basically handles faults

Tester email feedback: the connection to the database order is very slow, or even cannot be connected. I want to check it. See Oracle @ wdatest11 :~ Appadminwdadb

Tester email feedback: the connection to the database order is very slow, or even cannot be connected. I want to check it. See Oracle @ wdatest11 :~ /App/admin/wdadb/

Tester email feedback:
The connection to the database to be ordered is very slow, or even cannot be connected. I want to check it.

View:
Oracle @ wdatest11 :~ /App/admin/wdadb/adump> lsnrctl status

LSNRCTL for Linux: Version 11.1.0.7.0-Production on 17-JUN-2014 18:15:47

Copyright (c) 1991,200 8, Oracle. All rights reserved.

Connecting to (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP) (HOST = wdatest11) (PORT = 1521) # Here, hang is running and no response has been returned.

A tnsping test was conducted from other hosts:
Oracle @ IBlvs02:/u01/app/oracle/11.2/db_1/network/admin> tnsping wdatest

TNS Ping Utility for Linux: Version 11.2.0.3.0-Production on 17-JUN-2014 17:53:20

Copyright (c) 1997,201 1, Oracle. All rights reserved.

Used parameter files:

Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP) (HOST = 192.168.121.134) (PORT = 1521) (CONNECT_DATA = (SERVICE_NAME = wdadb )))
OK (14760 msec) # the visible response is also very slow.

Oracle @ IBlvs02:/u01/app/oracle/11.2/db_1/network/admin> tnsping wdatest

TNS Ping Utility for Linux: Version 11.2.0.3.0-Production on 17-JUN-2014 17:54:20

Copyright (c) 1997,201 1, Oracle. All rights reserved.

Used parameter files:

Used TNSNAMES adapter to resolve the alias

Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP) (HOST = 192.168.121.134) (PORT = 1521) (CONNECT_DATA = (SERVICE_NAME = wdadb ))) # hang has never responded

When I finally checked the DNS configuration, I found that:
Wdatest11 :~ # Cat/etc/resolv. conf
Nameserver 211.141.90.68
The system is configured with DNS, which is an intranet host and cannot be used at all. Therefore, after removing this DNS, the system returns to normal.
In fact, you can enable the trace of listener for viewing.

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