EM for Active-Passive environments

A DBA wrote to me and said he has some issues in seeing the targets in a 2 node active
passive cluster using SUN cluster. My advice to him was as follows:

Refer to the Oracle documention chapter "Configuring Oracle Enterprise Manager for Active and Passive Environments"

http://download.oracle.com/docs/cd/B16240_01/doc/em.102/e10954/actpass_env.htm#sthref274

As per this, the EM agent must be deployed to each physical node as well as to the logical IP address. You have obviously not done that. Setting up in an active-passive environment is more involved as compared to setting up in an active-active cluster (Oracle RAC!)