Layer2 tunnel and STP issue


#1

Hello,
I am trying to provide a solution for our customer about using Peplink with layer2 tunneling feature work as backup line for Layer2 switching infrastructure…
Please find our drawing in attach.
RSTP IEEE 802.1d 2004 is enabled on Switches…Brand of switches are Moxa.

In slide1
Status of Port3 is blocked state while other links between switches are connected.So Layer2 tunnel is backup state…

In slide2
If links between sw1-sw3 and sw2-sw4 are disconnected.Port3 goes to Learning state from Blocking state…
But port3 could not be forwarding state…

In slide3
If only LAN cable of PEP1 is unplugged then plugged , port3 goes to forwarding state…
And Peplink layer2 tunnel as layer2 backup line is running very well…

What is your comment?
Peplink should be work as transparent for STP traffic…Are there any interoperable problem between Switch and Peplink?

Another question is How can I pass more than one tagged frame through Layer2 tunnel.
I need to pass minimum two VLAN through layer2 tunnel…
Thanks,