Access (occasionally) Denied to Network Printers across VPN
Posted on 2008-11-05
You'll have to be patient to read all of this one, but it should be worth it!
The problem is the occasional loss of an application's access to a networked printer. Rightly or wrongly, we have linked the probelm to the use of RDP sessions when the problem arises. Perhaps you can explain why they are linked or suggest another cause of the problem.
Here is the scenario. We have a hosted ASP.NET Windows 2003 application server which indirectly uses a third-party application (LabelG) to print to a networked printer on another Windows 2003 Server over a (RAS-based) VPN. We understand that this is not a good idea, and have implemented FTP-based printing solutions for other parts of the system but, trust me, there are reasons why we have to use the VPN printer for LabelG. And most of the time it works fine but occasionally, it returns an error stating that it can not access the networked printer. It may be of use to let you know that LabelG is being invoked from a batch file which, in turn, is run every minute from the Windows Scheduled Task function. The batch file runs in the context of an Administrator account, which we will call admin1.
The other thing you need to know is that we use RDP to manage the server, logging into the admin1 or admin2 accounts. You will know that by default only two such sessions can exist at the same time.
Either through inspired brlliance or sheer coincidence, when we encountered the printer access problem, I logged one of these RDP sessions out. Printer access returned and LabelG continued to print successfully over the VPN. Since then we have had two more occasions when we lost networked printer access. Each time, I logged one of the users out and printing resumed.
Is there a logical explanation for this behaviour? If not, can you suggest a probably cause and solution?