[c-nsp] MSTP between Cisco / Brocade

[Steven Raymond]

Have a single layer 2 connection between 7609, version 12.2(33)SRD4, 6708, with a 10G connection to Brocade.  Using simplest form of MSTP, it works "fine" to a Brocade TI24X switch, running version 4 something.

Move the same cable to a 10G port on a MLXe, version 5.2.0T165, the Cisco blocks the port as the following:

ar01.prov#show spanning-tree active detail 
 Port 4 (TenGigabitEthernet1/4) of MST0 is designated blocking (dispute)
   Port path cost 2000, Port priority 128, Port Identifier 128.4.
   Designated root has priority 16384, address 0015.62b7.0dc0
   Designated bridge has priority 16384, address 0015.62b7.0dc0
   Designated port id is 128.4, designated path cost 0
   Timers: message age 0, forward delay 14, hold 0
   Number of transitions to forwarding state: 0
   Link type is point-to-point by default, Internal
   BPDU: sent 20540, received 10287

Google suggests that this may be caused by both switches' ports declaring they are designated role for the segment, and the Cisco proceeds to block as a defense against uni-directional link.  But these same optics and cables work fine on the other device.  Even so, they have been swapped with same circumstance.  Am certain there is no uni-directional link here.

Other searching says that Cisco is bad and sends the BPDUs tagged and that native vlan tagging must be removed, which is not enabled to begin with.

Brocade said to add "pvst-mode" to the interface config on the MLXe side, but it did not help at all.  And I don't understand what PVST has to do with MSTP as currently configured.

Any suggestions?

Thanks!!