Causes for and generating Pilot EDS, LDS, RDS, and CDS rejection metrics

I’m exploring the Prometheus metrics exposed and am looking for a better understanding of what can cause the below to occur:

  • pilot_xds_cds_reject
  • pilot_xds_eds_reject
  • pilot_xds_rds_reject
  • pilot_xds_lds_reject

I’m trying to recreate some of the Grafana dashboards in Dynatrace, and would like to be able to generate some of these metrics for testing. What are some reasons these could be rejected and any recommendations for causing some for testing/research?

Thank you,