In a test lab, I have implemented a backbone using 4 6500 switches connected in a square configuration. The backbone is using MST, the four 6500 are in the same MST region. Then, i connected two 2950 switches to the backpone. The 2950 are not using MST, they are using PVSTP.
If I simulate a failure in one of the backbone links, the connectivity between the two 2950 converges in one second and all is OK.
If I define QinQ to transport a 2950 VLAN thru the MST backbone and I simulate the same backbone kink failure, connectivty between the two 2950 is lost for more than 30 seconds. The interface between 6500 amd 2950 is re-initialized every time the backbone topology changes.Is there any known incomptibilty between MST and QinQ?