L2TP Clients can Download from FTP Server only but cannot Upload Because TCP MSS of AR28-31 Is not Set Correctly

Publication Date:  2012-07-27 Views:  134 Downloads:  0
Issue Description
Topology: FTP server――(internal network interface)AR28-31(external network interface)――public network――L2TP clients
Alarm Information
L2TP clients dial in successfully, and they can download from FTP server, but they cannot upload to it. 
Handling Process
Change the TCP MSS of relevant interface: interface Virtual-Template1 tcp mss 1400 interface Ethernet2/1 tcp mss 1400. The problem is solved. 
Root Cause
In the checkup for configurations, the TCP MSS of internal network interface is set to 1400, and Virtual-Template1 tcp mss 1500. So it is concluded that the problem is resulted from that TCP MSS is different during the exchanging of FTP stream. 
Suggestions
Null 

END