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Bring performance and reliability to your network with the Aruba Core, Aggregation, and Access layer switches. Discuss the latest features and functionality of the ArubaOS-Switch and ArubaOS-CX devices, and find ways to improve security across your network to bring together a mobile first solution.

Problems with learned MAC address over a STP blocked interface

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  • 1.  Problems with learned MAC address over a STP blocked interface

    Posted 23 days ago
    Hello Airheads,

    we are preparing 2 AOS-CX 6400 Switches (VSX pair with 10.10.1010) to replace the current 8212 Switches (K.15.18.0024).
    For the configuration, we have temporarily connected the 6400 switches with 2 seperate links (Ports 1/7/1) to one 8212 switch (Ports L23 and J23).
    Management VLAN 1100 is untagged on these ports.
    We are using MSTP and one port is in Status Alternate Blocking on the secondary 6400 switch.

    Primary 6400 Port 1/7/1 to 8212 Port L23 - Forwarding
    Secondary 6400 Port 1/7/1 to 8212 Port J23 - Alternate Blocking

    We are observing some interesting behavior.

    The ping to the secondary 6400 Switch with the Alternate Blocking Port is failing every 30 seconds and after another 30 seconds, the ping is working again.
    It looks like that this problem occurs when the switches have transmitted LLDP Informations.
    The 8212 switch puts the MAC address of the secondary 6400 into his MAC-Table for Port J23. It seems like that the 8212 switch is using the lldp information to fill his MAC-Table.
    When we deactivate the lldp transmit on Port 1/7/1 on the secondary 6400, the ping works fine without problems.
    When we configure the Management VLAN tagged on the ports, the ping also works fine.
    When we configure the Management VLAN tagged and VLAN 1 untagged on the ports, the ping works also fine.
    Only if the Management VLAN for the switches is configured untagged on the ports, then the ping will fail every 30 seconds.

    Is this a normal behavior?
    In the future configuration, we will use LAGs to the downstream devices.

    Best regards,
    Michael