Ah, solved.  As described in this post my IOS was too old and prestandard.  Upgraded to SXH8 and it works perfectly.   [URL]    
Have a 6509 sup720 with gigE blade connecting to a Dell 8024F, trying to run multiple spanning tree with the goal of being able to place some vlans on one uplink, other vlans on another.  The problem is that both the dell and the cisco force the interface to "boundary" ports, apparently they conclude that the bpdus being received are not MST bpdus and assume another region or misconfiguration.  So both switches think they are now roots for all (>0) mst instances and that prevents me from steering traffic based upon root path cost. For the life of me I cannot see what a difference in config may be (pasted below).  Now one minor point is that the cisco puts all non-assigned vlans (1-4094) into instance 0 while the dell only populates the vlans you have already created.  I honestly dont think that is the difference here. Also tried this with a 2950 with the same result.  Read that cisco in the past used a prestandard version of mst but from what I can find online my IOS is "recent" enough to be standard MST. Any insight? Thanks!     cisco: ! spanning-tree mode mst spanning-tree portfast default no spanning-tree optimize bpdu transmission ! spanning-tree mst configuration name meh revision 1 instance 1 vlan 10 instance 2 vlan 20 ! ! interface GigabitEthernet2/1 no ip address switchport switchport trunk encapsulation dot1q switchport trunk allowed vlan 10,20 switchport mode trunk switchport nonegotiate ! interface GigabitEthernet2/2 no ip address switchport switchport trunk encapsulation dot1q switchport trunk allowed vlan 10,20 switchport mode trunk switchport nonegotiate !   cisco-z#sh spanning-tree mst configuration Name      [meh] Revision  1 Instance  Vlans mapped --------  --------------------------------------------------------------------- 0         1-9,11-19,21-4094 1         10 2         20 -------------------------------------------------------------------------------   cisco-z#       cisco-z#sh spanning-tree active   MST00  Spanning tree enabled protocol mstp  Root ID    Priority    32768             Address     000c.cfd6.1400             This bridge is the root             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec    Bridge ID  Priority    32768  (priority 32768 sys-id-ext 0)             Address     000c.cfd6.1400             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec   Interface        Role Sts Cost      Prio.Nbr Type ---------------- ---- --- --------- -------- -------------------------------- Gi2/1            Desg FWD 20000     128.129  P2p Bound(RSTP) Gi2/2            Desg FWD 20000     128.130  P2p     MST01  Spanning tree enabled protocol mstp  Root ID    Priority    32769             Address     000c.cfd6.1400             This bridge is the root             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec    Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)             Address     000c.cfd6.1400             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec   Interface        Role Sts Cost      Prio.Nbr Type ---------------- ---- --- --------- -------- -------------------------------- Gi2/1            Boun FWD 20000     128.129  P2p Bound(RSTP) Gi2/2            Desg FWD 20000     128.130  P2p   MST02  Spanning tree enabled protocol mstp  Root ID    Priority    32770             Address     000c.cfd6.1400             This bridge is the root             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec    Bridge ID  Priority    32770  (priority 32768 sys-id-ext 2)             Address     000c.cfd6.1400             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec   Interface        Role Sts Cost      Prio.Nbr Type ---------------- ---- --- --------- -------- -------------------------------- Gi2/1            Boun FWD 20000     128.129  P2p Bound(RSTP) Gi2/2            Desg FWD 20000     128.130  P2p   cisco-z#       Dell: spanning-tree mode mstp spanning-tree mst 1 priority  16384 spanning-tree mst configuration instance 1 add vlan 10 exit spanning-tree mst 2 priority  8192 spanning-tree mst configuration instance 2 add vlan 20 exit spanning-tree mst configuration name "meh" exit spanning-tree mst configuration revision 1 exit   ! interface ethernet 1/xg23 switchport mode trunk switchport trunk allowed vlan add 10,20 exit !     interface ethernet 1/xg24 switchport mode trunk switchport trunk allowed vlan add 10,20 exit   8024#show spanning-tree mst-configuration Name: meh Revision: 1     Instance    Vlan Mapped ----------  ----------------------------------------------- 0          1 1          10 2          20     8024#   8024#show spanning-tree active Spanning tree Enabled (BPDU flooding : Disabled) Portfast BPDU filtering  Disabled mode mstp CST Regional Root:        80:00:5C:26:0A:A6:09:87 Regional Root Path Cost:  0     ###### MST 0 Vlan Mapped:   1 ROOT ID              Address         80:00:00:0C:CF:D6:14:00              Path Cost       20000              Root Port      1/xg23              Hello Time 2 Sec Max Age 20 sec Forward Delay 15 sec Bridge ID              Priority        32768              Address         80:00:5C:26:0A:A6:09:87              Hello Time 2 Sec Max Age 20 sec Forward Delay 15 sec Interfaces     Name    State   Prio.Nbr    Cost       Sts  Role PortFast  RestrictedPort ------  -------- --------- ----------  ---- ----- --------  ------- 1/xg23   Enabled  128.23        20000   FWD  Root      No      No 1/xg24   Enabled  128.24        20000   DSC  Altn      No      No   ###### MST 1 Vlan Mapped:   10 ROOT ID              Address         40:01:5C:26:0A:A6:09:87              This Switch is the Root.              Hello Time 2 Sec Max Age 20 sec Forward Delay 15 sec Interfaces   Name    State   Prio.Nbr    Cost       Sts  Role PortFast  RestrictedPort ------  -------- --------- ----------  ---- ----- --------  ------- 1/xg23   Enabled  128.23        20000   FWD  Mstr      No      No 1/xg24   Enabled  128.24        20000   DSC  Altn      No      No   ###### MST 2 Vlan Mapped:   20 ROOT ID              Address         20:02:5C:26:0A:A6:09:87              This Switch is the Root.              Hello Time 2 Sec Max Age 20 sec Forward Delay 15 sec Interfaces   Name    State   Prio.Nbr    Cost       Sts  Role PortFast  RestrictedPort ------  -------- --------- ----------  ---- ----- --------  ------- 1/xg23   Enabled  128.23        20000   FWD  Mstr      No      No 1/xg24   Enabled  128.24        20000   DSC  Altn      No      No   8024#         
MST between Dell and Cisco