[f-nsp] Spanning-tree event on single VLAN brings down LAG?

[Frank Bulk]

We had network event deeper in our network that resulted in some kind of
spanning tree event as evidenced by a TC (topology change) on our L2-only
ICX6610 stack.  What surprised us was that one VLAN going into a blocking
state resulted in the south bound LAG going down.

This is probably not right, but the root bridge for VLAN 294 is on the
ICX6610 stack. VLAN 294 is on both LAGs (and no other port/LAG)

Three questions:
a) when a STP event occurs is it normal that a VLAN goes into Blocking on
all the ports where it is present?
b) when a VLAN goes into blocking should all the physical (or LAG) ports
associated with that VLAN go down?
c) does configuring spanning tree on the port-based VLAN but disabling
spanning-tree on the physical (or LAG) ports prevent the physical port (or
LAG) going down?

Frank

============================================================================
====
Oct  9 21:35:22 STP: VLAN 294 Port 1/3/6 Bridge TC Event (MakeBlking) 
Oct  9 21:35:22 STP: VLAN 294 Port 1/3/6 STP State -> BLOCKING (MakeBlking) 
Oct  9 21:35:25 System: Logical link on dynamic lag interface ethernet 2/3/8
is down. 
Oct  9 21:35:25 System: Logical link on dynamic lag interface ethernet 3/3/4
is down. 
Oct  9 21:35:26 System: Logical link on dynamic lag interface ethernet 3/3/8
is down. 
Oct  9 21:35:29 Trunk: Group (1/3/8, 2/3/8, 3/3/4, 3/3/8) removed by 802.3ad
link-aggregation module. 
Oct  9 21:35:29 STP: VLAN 4 Port 1/3/8 STP State -> BLOCKING (PortDown) 
Oct  9 21:35:29 STP: VLAN 4 Port 1/3/8 STP State -> DISABLED (PortDown)
etc.

 Event
   |
Transport
  | |	
  | |	(1/3/6 & 2/3/6)
  | |	
ICX6610 (L2)
 | | | |
 | | | | (1/3/8, 2/3/8, 3/3/4, 3/3/8)
 | | | |
Core (L3)