I have a strage spanning-tree case seeking your help, the background is as follow:
Currently we have 3 physical sites, site A (production data centre), site B (DR data centre) and site C (BCP office), those 3 sites has Cisco 6506E, a pair of stacked 3750 and a 3560 switch respectively. The service provider using QinQ tunnel to provide the WAN services to us like the following simple picture:
site A (switch A) -------trunk in my switch and SP using VLAN ID 701-------site B (switch B)-------trunk in my switch and SP using VLAN ID 709 --------site C (switch C)
all these 3 switches are running the same MSTP region and the configuration are the same, same region name, same revision number, and instance (instance 0 for VLAN 1 and VLAN 2-4094 in instance 1), and we have manually configure the switch A being the root bridge for all of the instance.
However, recently, the switch B say it is the root bridge of instance 1, so there are 2 root bridge in the network for instance 1 and switch C also said switch B is the root of instance 1. Switch B is successful to receive BPDU from switch A, and it say switch A is root for instance 0. But from the debug spanning-tree all message, it said the trunk port connecting to switch A (sanity: mrecord missing).
I have searched in Internet but have no luck. Now we don't have spanning-tree issue because the connection is not a loop in our network. But I will feel more comfortable if switch B can get BPDU normally. Would you please help in this case and how can I solve the problem of mrecord missing?