Wired Intelligent Edge (Campus Switching and Routing)

This community is currently in a read-only state due to a maintenance window. For more info click here

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

MVP
MVP
Problem:

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).

 

TOPOLOGY :

 

 

SPANNING TREE MODE :

 

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

 

CORE SWITCH (sw00) PORT CONFIG :

 

Interface bridge-aggregation 4

Vlans mapped : vlan 253

 

Interface bridge-aggregation 3

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

 

AS01 PORT CONFIG :

 

TRK 1 mapped to vlan 253 only

Port 7 mapped to vlan 253 only

 

SW03 PORT CONFIG :

 

Port 8 mapped to vlan 253 only

TRK1 mapped to vlan 253 only

 



Diagnostics:

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.

 



Solution

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  :

 

                                                             Designated

  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
Revision #:
1 of 1
Last update:
‎04-09-2020 10:40 AM
Updated by:
 
Search Airheads
cancel
Showing results for 
Search instead for 
Did you mean: