I have an Internet VPN on a Cisco router between my headquarters and branch offices. The WAN line is a flet.
Since one of the VLAN's headquarters needs to be extended to the branch office side, the pseudowire was formed using the L2TPv3 function between the routers.
The show xconnect all has been successfully up, and the default GW from the branch office to the headquarters also has a Ping response, but the communication from the branch office to the web server that is beyond the headquarters GW is very slow and heavy. However, from the head office, which is the same VLAN, there is no such event.
I guess this may probably be due to improper L2TPv3 configuration and packet fragmentation fragments? However, I do not know what MTU value should be, and where MTU value should be set.
(1)
In the case of L2TPv3, I'd think to encapsulate the underlying Ethernet frame, how many bytes for header would be added in such case?
(2)
Let's say if the MTU value of the interface for the Internet VPN is 1200byte, how many bytes for the MTU value of the L2TPv3 packet that pass through it would be?
(3)
If you want to set/change the MTU value, should you configure it on the router interface between the head office and branch office? Or should I configure it on the default GW router at the headquarters?
(4)
In a L2TPv3 environment, if a packet of the size of a packet split occurs, can I expect that the PMTU (Path MTU Discovery) function automatically subtract and adjust the value? Is there any command required for that?
I look forward to hearing from experts about (1), (2), (3), and (4) above.
