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EXOS switch doesn't see MSTP root bridge if port is 802.1q tagged and untagged on EXOS 22.2 and 22.3

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TitleEXOS switch doesn't see MSTP root bridge if port is 802.1q tagged and untagged on EXOS 22.2 and 22.3
Symptoms
If run spanning tree topology similar to one below and interconnected ports are 802.1q tagged and untagged simultaneously, EXOS switch doesn't see root bridge.

X460-EXOS[LACP ports 23,24] <-> [LACP ports tg.1.49, tg.1.50]C5K125-EOS

[C5K125]
support ->show spantree stats active
Spanning tree status       - enabled
Spanning tree instance     - 0
Designated Root MacAddr    - 00:1F:45:71:E3:08
Designated Root Port       - 0
Designated Root Priority   - 4096
Designated Root Cost       - 0
Root Max Age               - 20
Root Hello Time            - 2
Root Forward Delay         - 15
Bridge ID MAC Address      - 00:1F:45:71:E3:08
Bridge ID Priority         - 4096
Bridge Max Age             - 20
Bridge Hello Time          - 2
Bridge Forward Delay       - 15
Topology Change Count      - 4
Time Since Top Change      - 0 days 0:45:08
Max Hops                   - 20
SID   Port         State              Role          Cost        Priority
---   ----------   ----------------   -----------   --------    --------
0      tg.1.49      Discarding         Disabled      0           128
0      tg.1.50      Discarding         Disabled      0           128
0      lag.0.1      Discarding*        Designated    10000       128

[x460]
->show stpd
                MSTP Global Configuration:
MSTP Region Name        : 00049699c13c
MSTP Format Identifier  : 0
MSTP Revision Level     : 3
MSTP Digest             : ac:36:17:7f:50:28:3c:d4:b8:38:21:d8:ab:26:de:62
Common and Internal Spanning Tree (CIST)        : s1
Total Number of MST Instances (MSTI)            : 0
 
Name       Tag  Flags  Ports Bridge ID        Designated Root  Rt Port Rt Cost
s0         0000 D-----     0 800000049699c13c 0000000000000000 -------       0
s1         0000 EM----    22 800000049699c13c 800000049699c13c -------       0
 
Total number of STPDs: 2                STP Flush Method: VLAN and Port
STP Filter Method: System-wide          STP BPDU Forwarding: On
 
Flags: (C) Topology Change, (D) Disable, (E) Enable, (R) Rapid Root Failover
       (T) Topology Change Detected, (M) MSTP CIST, (I) MSTP MSTI
Environment
  • EXOS 22.2, 22.3
  • All EXOS platforms
  • MSTP
Cause
This issue is probably triggered by xos0069318 - "If the port is part of both tagged and untagged VLANs participating in MSTP then the BPDU packets are not processed by EXOS"
Resolution
Upgrade to EXOS version where mentioned CR is not present.
How do I search release notes for known issues?
What is the recommended software version for my platform?

As a workaround you can configure port as a tagged port only.
Additional notes

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