Listener clarification

I have two version of 11g and 10G: 11g listener was using 1525 port and 10g was using 1521. All of the databases are on 10g version and registered to 10g listener, 11g had nothing registered even the the listener is running.

I have application stop working as soon as 11g is installed on the server.

I have to add the parameter LOCAL_LISTENER=local server port 1521 and evyerhting start working again.

my db is 10g and register to 10g listener with 1521 port, even 11g was installed but I have nothing registered to it. why do I have to add the LOCAL_LISTENER in the parameter file ?



Thanks,

Shall we understand ...
There are two ORACLE_HOMEs, one for Ora10g and one for Ora11g?
There are no active instances pointing to Ora11g?
There is an active Ora11g listener? Why?

There are two ORACLE_HOMEs, one for Ora10g and one for Ora11g?
yes
There are no active instances pointing to Ora11g?
yes
There is an active Ora11g listener? Why?
yes, the reason being b/c there will be 11g instance in the close future and we want to have 10g instance register to 10g listener and 11g instance register to 11g listener.


what I don't understand was why do I have to add the local_listener to the parameter file when it was already registered to 1og listener with the default port of 1521.

Thanks,

local_listener=local is telling Oracle to listen on host's IP address at port=1521

My guess is that something is wrong either with tnsnames.ora file or there is a mismatch in regards to ORACLE_HOME, like pointing to wrong ORACLE_HOME. Hard to tell not having access to the environment.