Microsoft Communicator 2007 File Transfer fails

Unanswered Question
Mar 6th, 2008

I'm experiencing a problem receiving a file, from within Microsoft Office Communicator 2007, on workstations that have Cisco's VPN client installed. Microsoft Office Communications Server 2007 (OCS) was recently introduced into our environment (by me - I'm the Systems Integration Analyst working on the project) and we're using Communicator as the Instant Messaging (IM) workstation client. Communicator has the ability to transfer files, within an IM, between Communicator users. File transfers, from within Communicator (send/receive), works well on XP and Vista workstations on which Cisco's VPN client is not installed (Cisco VPN client is only installed on XP machines).

This problem is being experienced on XP machines (these are the only types of machines, with Cisco's VPN client, that Communicator has been tested on). I've noticed that I can successfully receive files if I uninstall the Cisco VPN client (and restart the machine).

Additional Information: The same problem occurs on workstations that have VMware Workstation installed (without the Cisco VPN client installed). They cannot receive files transferred from within IMs, but disabling the two VMware Local Area Connections (VMnet1 and VMnet8) restores the ability to receive files. I placed a call into Microsoft support and the technician was able to dig up an article that pointed to the firewall that is installed as part of the Cisco VPN client. He also made a reference to VMware being a potential source of the problem (possibly the VMware NAT Service, but I disabled the service and experienced the same problem). Having said that ... the problem exists when VMware Workstation is removed from the equation.

Thank you in advance for any feedback that you can provide, Joe.

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ivillegas Wed, 03/12/2008 - 15:28

Add a statement in ACL that allows the port number 5061 that is used by Microsoft Office Communications Server and check if the file transfer takes place then.

joefonte Thu, 03/13/2008 - 04:20

Thanks for the input, but I'm not sure what you mean by adding port 5061. Did you mean to our WAN/switch infrastructure? Perhaps I didn't explain myself clearly.

The problem exists when the VPN connection is not being used; the problem exists when the VPN software is installed on a workstation (but again - not when the VPN software is in use).

So here's the scenario... There are two workstations connected to the same switch (say a 2960). The VPN client has not been launched. There is no ACL (on the switch - or for that matter - we are not restricting any ports/traffic between workstations and/or servers on our WAN) that restricts any type of communication between the workstations. Workstation A (Wks-A) has the VPN client installed. Workstation B (Wks-B) does not have the VPN client installed. Wks-A can initiate a file transfer to Wks-B (from within Communicator) and Wks-B can recieve the file. Wks-B can initiate a file transfer to Wks-A (from within Communicator), but Wks-A cannot receive the file.

So here's some additional information...

After talking to Microsoft, it turns out that regular IM traffic goes between workstation to server and then from server to workstation. The file transfer from within Communicator uses a Point-to-Point connection (between workstations) and is accomplished with TFTP.

The Microsoft technician also alluded to the possible cause of the problem being the firewall portion of the Cisco VPN client...

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