Q: If MA5200G enables l2tp, packet fragmentation will often occur. Generally, both tunnel and session can set up normally, but the webpage cannot be opened; also, the clients fail to ping big packets of 1500, and can ping to the small packets. This is caused by packet fragmentation. It needs to change the MSS of clients, how to change it?
There are two methods that can help change MSS value:
1. Use the registry to change the MSS of clients, namely, defaultrcvwindow. For the operation, see the attachment: Changing registry.rar
hkey_local_machine\system\currentcontrolset\services\vxd\mstcp，defaultrcvwindow is the default size of transmission unit buffer, and change it.
2. Use a software to change mss value, and see Changing registry.rar
Only mss needs to be changed at software, and other parameters do not need. Save the configuration after chaning the value and reset PC. At last, check if the registry has been changed successfully.
MSS is negotiated, so it is related to client software also. When L2TP users can ping through but cannot open webpages because of packet fragmentation, you can replace the client software to test, besides changing the MSS of clients, e.g., internet dialer of Telecom.