distributed and DNS requests

When will the scheduler, the workers or the client perform DNS requests? How many DNS requests are to be expected?

Does it depend on the way, the cluster is initialized?
E.g. is `dask-worker --nthreads 1 --nprocs 80 my_server_name:8786` triggering much more requests than `dask-worker --nthreads 1 --nprocs 80 my_server_ip:8786`?

Background: I got a call from my IT department because one of the compute servers was doing ~1 request each millisecond. This stopped as soon as I shut down the jupyter notebook and the distributed cluster, which is why I have the questions mentioned above.