When an External-Other scheduler job has an agent name that is using an alias name of WA agent, the job will stay in EXTMON state.
The job may also not complete if the WA Agent is behind a load balancer.
Release : 12.x
Component : CA WORKLOAD AUTOMATION DE (DSERIES)
1. The External-Other Scheduler job type should not be used with agents behind load balancers. If the agent node is moved/switched by load balancer, the external monitoring job (or any job) on the agent will not be moved to the next agent. The job will then have to resubmitted by manager, hence it is recommended to use direct physical agent.
2. The agents will always try to revert to their actual name (agentname in agentparm.txt). Do not use aliases, as they are normally reserved for plugins like database etc.
See here for more details on External jobs.