This is how to connect two branch offices over the Internet with Layer 2 support allowing broadcasts and VLAN tags. The first obvious choice is to try MPLS. But if MPLS is not supported then L2TPv3 will come into play. L2TPv3 connection is established between two routers which have the access to the interesting VLAN. In our case it is VLAN100.
|HQ Configuration||Branch office config|
L2TPv3 is used to form pseudowire. All packets arriving to interface FastEthernet0/0.100 of any router are forwarded to L2TPv3 tunnel with L2 headers.
CEF must be turned on. Also, if you need to use different VLAN numbers on both ends, then you can use VLAN ID Rewrite feature
show l2tun tunnel state
show l2tun session