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  • 1.  MSTP - Does it work with Switches that doesnt Support MSTP?

    Posted Dec 02, 2025 08:12 AM

    Hi Guys

    we use a Aruba 6300M as a Coreswitch.

    This switch only Supports MSTP or RPVST in the Config.

    We have a heterogene Network with some other Switches.

    Does MSTP still work if some of the Switches doesnt support MSTP? What is the behaviour?

    Can we just activate "normal" STP on them? Can they interrupt MSTP?

    I want to configure only 1 region with 1 MSTI because we dont have redundancy and i just want to secure loops with STP.  But because the Switch only support MSTP i need to do it like this.

    If there is a way to configure RSTP on the 6300M let me know.

    Greetings netshark



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  • 2.  RE: MSTP - Does it work with Switches that doesnt Support MSTP?
    Best Answer

    Posted Dec 03, 2025 07:21 PM

    Good questions. Helped me to read few documents and listen to few videos.

    Yes. MSTP (IEEE 802.1s) is backward-compatible with RSTP (802.1w) and STP (802.1D). When your AOS-CX 6300M running MSTP detects a neighbour that only speaks STP or RSTP, it falls back to a Common Spanning Tree (CST) mode for interoperability. This means:

    • The MST region appears as a single logical bridge to legacy STP/RSTP devices.
    • Loops are still prevented across the mixed environment.

    Yes, you can leave them on classic STP or RSTP. They will interoperate with MSTP through CST. However:

    • Convergence will be slower if they run STP (30–50 seconds).
    • RSTP is better for faster recovery.
    • They won't break MSTP, but you lose the benefit of multiple instances (which you don't need anyway since you plan one MSTI).

    Why MSTP is preferred over RPVST+

    • RPVST+ creates one instance per VLAN, which can hit hardware limits and cause instability.
    • MSTP scales better and is standards-based.

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  • 3.  RE: MSTP - Does it work with Switches that doesnt Support MSTP?

    Posted Dec 04, 2025 02:14 AM

    Hello Yash

    Thank you for answering, this helps!

    So we will do its with MSTP with one 1 Region and 1 MSTI.

    Can you send me the source, where you found the behaviour about detecting a neighbour that only speaks STP or RSTP?

    I just got this answer by AI...

    Thanks again,

    Greetings Netshark

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    Original Message


  • 4.  RE: MSTP - Does it work with Switches that doesnt Support MSTP?

    Posted Dec 05, 2025 03:27 AM

    Compatibility to RSTP and STP is inherently designed into MSTP.

    You might want to consult the IEEE 802.1Q standard, available from https://ieeexplore.ieee.org/document/10004498 (free after registration).

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    Original Message


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