Good Daniel:

I was under the Linux7.2 installed oracle rac, 12 c now
/u01/app/oracle/product/12.1.0/dbhome_1/network/admin configuration under the tnsnames. Ora file, there are a few servicename, including 11 g, 10 g, configured, tnsping 11 g service name to pass, but 10 g impassability, do you have a solution?

Sqlnet. Ora configuration is as follows:
SQLNET. ALLOWED_LOGON_VERSION=8
NAMES. DIRECTORY_PATH=(TNSNAMES EZCONNECT)