Oracle Enterprise Manager 11g Database Control - Agent Unreachable

Single instance DB. I can login to Oracle Enterprise Manger (OEM). However, on the Home Page it says: > Status - Agent Unreachable Most tasks such as checking RMAN status, adding datafiles, etc. can still be done through the OEM. I do not know how ***Agent Unreachable*** impacts the OEM in this case (DB Control) I checked status of the agent from $ORACLE_HOME/bin/emctl status agent, it showed: > The Agent is not Running So, I want to start the agent, but running the command $ORACLE_HOME/bin/emctl start agent is not working. The command is not available. In Oracle docs, it is mentioned that the command emctl start agent should be executed from AGENT_HOME/bin. However, I do not know the AGENT_HOME path. How can I start the OEM Agent or figure out what the underlying issue is?