You will need valid logon credentials whatever you do - however if you want to do share level backups then you will either have to disable NDMP on the EMC NAS - or change the NDMP ports on all Backup Exec servers (Media Servers and Remote Agents) so that they use something other than 10,000
Basically if Backup Exec gets an NDMP response on port 10,000 then it thinks a remote agent is presnet and tries to use the remote agent even though it is a NAS that is not running the agent. The job will then fails as the remote agent is not really there. If Backup Exec does not detect something on Port 10,000 then it will fail back to the remote agent program that is running on the media server itself and use that to attach to the share.
This leave 2 choices -
1) Disable port 10,000 on the EMC NAS by disabling NDMP.
2) Make Backup Exec us e a non-standard NDMP port so that it no longer uses 10,000
BTW backups using the Backup Exec NDMP option should be faster then trying to do share level backups of the same data,as such what are you trying to achieve by attempting to use share level backups?