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What is the MSTR port role in Spanning-tree ?

It shows up on boundary ports between MST regions and switches running (R)PVST+. Note that it shows up only on the switches running MST.

It seems to appear as "MSTR" only under certain conditions and not for all MST instances, mainly when the root bridge for vlan 1 is located in the PVST+ region.

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    "MSTR" is not an 802.1Q role, it must be Cisco-specific for compatibility with RPVST+.
    – Zac67 ♦
    Commented Oct 5, 2018 at 17:16
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin ♦
    Commented Dec 25, 2018 at 9:38

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MST/RSTP is very old incompatible between switches , it will still work but they should be upgraded to newer IOS versions, You could use this command either under the interface spanning-tree mst pre-standard to force it

The MSTR FWD is the master port for the uplink root port usually for the CIST in a multi-region MST operation. Check here

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