Database Software

Hi all,
I'm planning to migrate my RAC to a brand new 11.2 on rhel 5.4 64 bit

This the situation:
- grid installed on 2 node rac
- 2 vip with standard listener on 1521
- 2 scan vip (I know ... 3 is better, but for a 2 node installation I cant throw away another ip...) with correspective scan listener on 1521
- rac database DB1,which register with standard listener on port 1521

Now I need to create a 2nd rac database "DB2" so it register with only a 2nd listener on port, let's say, 1522.
This would permit me to create acl on firewall: connection to DB1->port 1521, connection to DB2->port 1522

Here's come the problem: how can I add a second listener on a different port?

I've added a listener with

srvctl add listener -l LISTENER_2 -p 1522

now I have to add a scan listener which listen on port 1522:

srvctl add scan_listener -l LISTENER2_ -p 1522
PRCS-1028 : Single Client Access Name listeners already exist


What I'm missing?
I'm lost in 11.2 doc, and also on metalink I cant find anything that helps me...

Regards,
Roberto