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  • 1.  RSTP / STP TCN Logs Between Aruba and HP 5130 Switches

    Posted Sep 07, 2025 06:21 PM

    Hello,

    We recently integrated new Aruba CX switches into our network. The Aruba switches are connected via LAG to our backbone. Since then, we have observed continuous STP Topology Change Notifications (TCNs) in the logs on the Aruba side.

    NOC-up-2 hpe-mstpd[3111]:     Event|2011|LOG_INFO|CDTR|1|Topology Change received on port 1/1/52 for CIST from source: 00:0f:e2:07:c2:ee

    Some details:

    • The Aruba switches are running RSTP (802.1w).

    • Existing HP 5130 switches are also running RSTP.

    • All access ports on both Aruba and HP sides are configured as edge ports.

    • Despite this, the Aruba switch that connects to the backbone (via LAG1) shows frequent TCNs as if they are being received from that interface.

    • On the HP 5130 side, we do not see the same TCN log entries.

    We would like to understand why this behavior occurs and whether it is expected in a mixed Aruba/HP RSTP environment.

    Thank you.



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  • 2.  RE: RSTP / STP TCN Logs Between Aruba and HP 5130 Switches

    Posted Sep 16, 2025 12:25 AM

    This behavior is not typically expected if edge ports are correctly configured, and there are no actual topology changes occurring (like links flapping).

    Even though you might have configured access ports as edge on both Aruba and HP switches, the HP 5130 might still be generating TCNs if:
    - Some ports are not truly configured as "edge" (in HP terms, this is usually stp edged-port enable).
    - Devices connected to HP access ports are flapping or coming online frequently.
    - The LAG toward Aruba is not properly excluding TCN propagation.
    - RSTP TCNs are generated when a port transitions to forwarding and is not configured as an edge port. If a non-edge port goes up/down, that causes a TCN.
    Check and ensure that Edge is shown as YES for the relevant interfaces:
    display stp brief
    display stp interface <interface>
    Another issue might be the improper configuration of LAG and STP Role mismatch. Your switches might be handling BPDU differently and interpreting the STP Roles as well.
    LAGs have to be identically configured on both sides and they must not be marked as edge. In addition, on HP check whether you are using Legacy STP (MSTP/RSTP). 
    HP 5130 and Aruba CX both support MSTP and RSTP. However, if one side is running MSTP (which includes RSTP via the CIST) and the other is pure RSTP, unexpected behavior like excessive TCNs can occur.


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    Shpat | ACEP | ACMP | ACCP | ACDP
    Just an Aruba enthusiast and contributor by cases
    If you find my comment helpful, KUDOS are appreciated.
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  • 3.  RE: RSTP / STP TCN Logs Between Aruba and HP 5130 Switches

    Posted Sep 25, 2025 06:37 AM

    Thank you for the detailed response.
    We have double-checked the configuration:

    • All access ports on both sides are configured as edge.

    • The LAG toward the backbone is not configured as edge, and the configuration is identical on both sides.

    • We do not see link flaps or frequent up/down events.

    It seems the main difference is that the HP 5130 is running RSTP (802.1w), while the Aruba CX is running MSTP (802.1s), which interoperates with RSTP through the CIST.

    Could the mismatch between MSTP and RSTP modes be the reason why we see continuous TCN log messages on the Aruba side, even though the HP side does not report them?

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    Original Message


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