Wired Intelligent Edge (Campus Switching and Routing)

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Spanning Tree Issues Between Procurve And Comware Switch For Root Path Selection


On AS01, root path towards the core switch (SW00) should be Trk1 for instance 2. However, the switch considers port 7 as the root path towards Core (SW00).







MSTP with 3 Instances (0,1,2)


INSTANCE 0 : Remaining vlans

Root : SW00


INSTANCE 1 : Vlan 253

Root : AS01


INSTANCE 2 : Vlan 16,20,68,244,254

Root : SW00




Interface bridge-aggregation 4

Vlans mapped : vlan 253


Interface bridge-aggregation 3

Vlans mapped : vlan 16,20,68,244,254




TRK 1 mapped to vlan 253 only

Port 7 mapped to vlan 253 only




Port 8 mapped to vlan 253 only

TRK1 mapped to vlan 253 only



The concept of spanning tree instance participation in ProCurve and Comware works slightly different

In Comware switches for an uplink port to be participating in spanning tree instance, not only should the vlan-to-instance mapping match but the vlans associated with the instance should also be tagged/untagged to the uplink port.

If all the vlans in a particular instance are not tagged/untagged on the uplink port of Comware switch, the uplink would not participate in STP instance

In Procurve switches, it is not necessary to map vlans to the uplink port. We only have to make sure the MST digest across all switches are the same.



In our scenario,

We have two paths from AS01 to reach SW00 (port 7 through SW03 or TRK1 directly connected link )


  • Considering first link , TRK1 connects to BAGG4 of SW00 which has only vlan 253 mapped to the bridge aggregation. Since Instance 2 vlans are not mapped to BAGG4, it would not participate in MSTI 2.
  • Considering second link, port 7 connects to port 8 of SW03. Ports on Procurve would participate in Instance 2 as in Procurve switches it is not necessary for us to have vlan-port membership. Also BAGG3 which connects to Trk1 of SW03 has Instance 2 vlans tagged/untagged to the bridge aggregation.


Hence forth, path towards root which AS01 is considering is correct as per spanning tree operation difference in Procurve and Comware.


Below output shows the as root bridge and as the path towards root.


xx-ge-as01# show spanning-tree instance 2


MST Instance Information


  Instance ID : 2

  Mapped VLANs : 16,20,68,244,254

  Switch Priority         : 8192


  Topology Change Count   : 5

  Time Since Last Change  : 7 hours


  Regional Root MAC Address : c4cad9-a96d33

  Regional Root Priority    : 0

  Regional Root Path Cost   : 40000

  Regional Root Port        : 7

  Remaining Hops            : 18


  Root Inconsistent Ports  :

  Loop Inconsistent Ports  :



  Port  Type      Cost      Priority Role       State        Bridge

  ----- --------- --------- -------- ---------- ------------ --------------

  1     100/1000T  20000     128      Designated Forwarding   548028-ece100

  2     100/1000T  20000     128      Designated Forwarding   548028-ece100

  3     100/1000T  Auto      128      Disabled   Disabled

  4     100/1000T  Auto      128      Disabled   Disabled

  7     100/1000T  20000     128      Root       Forwarding   20677c-c67590

  8     100/1000T  Auto      128      Disabled   Disabled

  9     100/1000T  Auto      128      Disabled   Disabled

  10    100/1000T  Auto      128      Disabled   Disabled

  Trk1             20000     64       Designated Forwarding   548028-ece100

Version history
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Last update:
‎04-09-2020 10:40 AM
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