In reply to Kanth:
All of the connections made need to refer to the base classes. In this case, it would be ‘base_monitor’. Since pkt_port only exists in the extended ‘ext_monitor’, the connect phase has no knowledge of this port, hence the error.
Typically, extended classes will only change the behavior of an object or component, either by an added constraint or additional checks. You won’t be able to add any additional exports/imports as the base class has no access to these.