Recently I did a test with 2x 2960 and 2x SDH equipment from Haliplex. According to the vendor they're on Layer 1 only.
As per the diagram, we have a Catalyst 2960 on each end. Both Gi0/1 on the 2 switches are configured as trunk. So I have 2 laptop plugged in on the switches and we can ping each other. When I create a 2nd VLAN on both the switches, I get error message "vlan ID mismatch" and some peer inconsistency error. I show spanning-tree and I see the Gi0/1 status is BKN. I believe it meant broken.
Have anyone encounter this kind of issue before?