In reply to rajanikanthd:
Where are you getting the interface? If you are getting it from driver component which is under the agent, you need to use wildcard “*” when you set config db.
uvm_config_db#(virtual flit_intf)::set(null, "uvm_test_top.env.flit_mst_agnt0*", "mst_if", flit_if_4);