If the AD discovery is configured to use the default credentials then the account running the Dell Enterprise Reporter Node service is the account that is used to authenticate to the ARS server. If the AD discovery is configured to use alternate credentials then these credentials are used.
If the credentials specified are to authenticate to a remote domain/forest and the ARS server is in the same domain as Enterprise Reporter then the alternate credentials used will try to authenticate to the ARS server as there is currently no way to specify credentials to access the ARS server.
There is an enhancement submitted to the product team to consider allowing specific credentials to the ARS server. The below link contains this enhancement, if this is something you would like to see in the product please click the up arrow to increase the priority of the request: