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Dell EMC Configuration Guide for the S4048T–ON System 9.14.2.4

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Debugging and Verifying MSTP Configurations

To debut and verify MSTP configuration, use the following commands.

  • Display BPDUs.
    EXEC Privilege mode
    debug spanning-tree mstp bpdu
  • Display MSTP-triggered topology change messages.
    debug spanning-tree mstp events

Examples of Viewing MSTP Configurations

To ensure all the necessary parameters match (region name, region version, and VLAN to instance mapping), examine your individual routers.

To show various portions of the MSTP configuration, use the show spanning-tree mst commands.

To view the overall MSTP configuration on the router, use the show running-configuration spanning-tree mstp in EXEC Privilege mode.

To monitor and verify that the MSTP configuration is connected and communicating as desired, use the debug spanning-tree mstp bpdu command.

Key items to look for in the debug report include:
  • MSTP flags indicate communication received from the same region.
    • As shown in the following, the MSTP routers are located in the same region.
    • Does the debug log indicate that packets are coming from a “Different Region”? If so, one of the key parameters is not matching.
  • MSTP Region Name and Revision.
    • The configured name and revisions must be identical among all the routers.
    • Is the Region name blank? That may mean that a name was configured on one router and but was not configured or was configured differently on another router (spelling and capitalization counts).
  • MSTP Instances.
    • To verify the VLAN to MSTP instance mapping, use the show commands.
    • Are there “extra” MSTP instances in the Sending or Received logs? This may mean that an additional MSTP instance was configured on one router but not the others.

The following example shows the show run spanning-tree mstp command.

DellEMC#show run spanning-tree mstp
!
protocol spanning-tree mstp
name Tahiti
revision 123
MSTI 1 VLAN 100
MSTI 2 VLAN 200,300

The following example shows viewing the debug log of a successful MSTP configuration.

DellEMC#debug spanning-tree mstp bpdu
MSTP debug bpdu is ON
DellEMC#
4w0d4h : MSTP: Sending BPDU on Te 2/21 :
ProtId: 0, Ver: 3, Bpdu Type: MSTP, Flags 0x6e
CIST Root Bridge Id: 32768:0001.e806.953e, Ext Path Cost: 0
Regional Bridge Id: 32768:0001.e806.953e, CIST Port Id: 128:470
Msg Age: 0, Max Age: 20, Hello: 2, Fwd Delay: 15, Ver1 Len: 0, Ver3 Len: 96
Name: Tahiti, Rev: 123, Int Root Path Cost: 0
Rem Hops: 20, Bridge Id: 32768:0001.e806.953e
4w0d4h : INST 1: Flags: 0x6e, Reg Root: 32768:0001.e806.953e, Int Root Cost: 0
    Brg/Port Prio: 32768/128, Rem Hops: 20
INST 2: Flags: 0x6e, Reg Root: 32768:0001.e806.953e, Int Root Cost: 0
    Brg/Port Prio: 32768/128, Rem Hops: 20

4w0d4h : MSTP: Received BPDU on Te 2/21 :
ProtId: 0, Ver: 3, Bpdu Type: MSTP, Flags 0x78 (Indicates MSTP routers are in the [single] region.)
CIST Root Bridge Id: 32768:0001.e806.953e, Ext Path Cost: 0
Regional Bridge Id: 32768:0001.e806.953e, CIST Port Id: 128:470
Msg Age: 0, Max Age: 20, Hello: 2, Fwd Delay: 15, Ver1 Len: 0, Ver3 Len: 96
Name: Tahiti, Rev: 123 (MSTP region name and revision), Int Root Path Cost: 0
Rem Hops: 19, Bridge Id: 32768:0001.e8d5.cbbd
4w0d4h : INST 1 (MSTP Instance): Flags: 0x78, Reg Root: 32768:0001.e806.953e, Int Root Cost: 0
    Brg/Port Prio: 32768/128, Rem Hops: 19
INST 2 (MSTP Instance): Flags: 0x78, Reg Root: 32768:0001.e806.953e, Int Root Cost: 0
    Brg/Port Prio: 32768/128, Rem Hops: 19
Indicates MSTP
routers are in the
(single) region
MSTP Instance
MSTP Region name

The following example shows viewing the debug log of an unsuccessful MSTP configuration.

4w0d4h : MSTP: Received BPDU on Te 2/21 :
ProtId: 0, Ver: 3, Bpdu Type: MSTP, Flags 0x78Different Region (Indicates MSTP routers are in different regions and are not communicating with each other.)
CIST Root Bridge Id: 32768:0001.e806.953e, Ext Path Cost: 0
Regional Bridge Id: 32768:0001.e806.953e, CIST Port Id: 128:470
Msg Age: 0, Max Age: 20, Hello: 2, Fwd Delay: 15, Ver1 Len: 0, Ver
Name: Tahiti, Rev: 123, Int Root Path Cost: 0
Rem Hops: 20, Bridge Id: 32768:0001.e8d5.cbbd
4w0d4h : INST 1: Flags: 0x70, Reg Root: 32768:0001.e8d5.cbbd, Int
    Brg/Port Prio: 32768/128, Rem Hops: 20
INST 2: Flags: 0x70, Reg Root: 32768:0001.e8d5.cbbd, Int Root Cost
    Brg/Port Prio: 32768/128, Rem Hops: 20

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