When there is a client machine with the Symantec Management Agent (SMA) installed and there is an issue with shared GUID between another client machine, it is common to use "AeXAgentUtil.exe /resetguid".
150636 "Details on aexagentutil.com and AeXNSAgent.com"
Resetting the GUID should be enough to address the issue but in some circumstances, it is not.
Resetting the Agent GUID should help in getting a new GUID but there are things that this process will not help with. For example, if the problem is caused by the same resource keys reported by both computers, the same GUID on those client machines is just the result of this situation. The SMP gets the same resource keys, it assumes that this is the same resource and performs a merge operation.
Usually, you can validate this situation by capturing basic inventory (180434 "How to copy sent NSEs into a separate folder on the Altiris Agent") from both machines and checking what resource key is the same. Usually, OEM computers will display this type of issue.
Using "/resetguid" switch as a way to resolve a duplicate GUID issue may not be as effective if the client machine is using an image with the SMA already on it. The Deployment Solution (DS) process usually takes care of it but "DSUniqueID" key might be the problem. If these are completely new machines, you may want to consider deleting these computers from the SMP Console (Manage>Computers, select the computer(s) and Right-click>Delete), reinstall the SMA from those machines, and let the SMP generate a new set of GUIDs for those machines.
Delete the resources associated with this duplicated GUID by passing the GUID to the "ItemToDelete" table and then add the GUID to the "AgentBlacklist" table so the GUID cannot be reassigned. Once the GUID is blacklisted any agents that check into the SMP with that GUID are no longer known to the SMP. The SMP then sends a command to the agent to reset its GUID.
What happens when we run "aexagentutil.exe /resetguid" on a client machine that is sharing the same GUID as another machine?
Symantec Management Agent (SMA) forgets its current GUID and calls "CreateResource.aspx" page to pass the resource keys. If the call succeeded, then the received GUID is remembered on the agent.
It is up to the SMP to decide which GUID to send to the agent in the response and the decision is made based on the resource keys.
Does the previous GUID assigned to this machine get blacklisted?
No, SMA just resets its data.
178533 "What is Agent Blacklisting?"
If we are using Deployment Solution (DS), we thought there is already an automatic process that wipes out any GUID reference from the image itself, right?
There is a "DSUniqueID key". DS generates this key and sends it to the SMP among other resource keys to allow DS to maintain the same Agent GUID during the imaging process. This key is deleted by SMA after imaging gets finished. So if somehow all these PCs were imaged with the same DSUniqueID, they will be identical from the SMP point of view. ResetGuid switch should clear out those references and request a new GUID from the SMP.