dbconsole: unable to connect to the database

Today it happened again. A 10gR2 database with a dbconsole installed on it was giving problems. The dbconsole was able to get the status of the instance and the agent was able to have the agent connected. It was not able to get the status of the listener. On this specific site there was a problem with system administration, to be more precise with the dns. Some settings were based on ip-address, some on qualified names. This eventually caused the problem. The fix in this case was to enter the full qualified name in the listener.ora and restart the dbconsole. After this all was running ok. Allways make sure that the addresses in listener.ora and targets.xml are the same.