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  • 1.  Possible edge switch loop detected; Limit on MAC moves exceeded from uplink to ethernet port

    Posted 03-21-2023 17:47

    Hi Community,

    I could see the following logs often from several switches. It shows only VLAN ### (native):

    Mar 15 07:29:06 SWITCH-A l2ald[9147]: L2ALD_MAC_MOVE_EXCEEDED_BD: Limit on MAC moves exceeded at VLAN Dxxx+###for MAC aa:bb:cc:dd:ee:ff moved from interface ae0.0 to interface ge-3/0/32.0;Mac move limit is 5. FORWARDING THE PACKET
    Mar 15 07:28:56 SWITCH-A l2ald[9147]: L2ALD_MAC_MOVE_EXCEEDED_BD: Limit on MAC moves exceeded at VLAN Dxxx+###for MAC aa:bb:cc:dd:ee:ff moved from interface ae0.0 to interface ge-3/0/32.0;Mac move limit is 5. FORWARDING THE PACKET

    Is there someone who can explain why mac moves between ae(uplink) and ethernet port?  Please see the following related configuration:

    set vlans Dxxx switch-options mac-move-limit 5
    set vlans Dxxx switch-options mac-move-limit packet-action log

    set interfaces ge-3/0/32 mtu 9192
    set interfaces ge-3/0/32 unit 0 family ethernet-switching vlan members Dxxx
    set interfaces ge-3/0/32 unit 0 family ethernet-switching storm-control default

    set protocols rstp interface ge-3/0/32 no-root-port

    set interfaces ae0 description UPLINK-SWITCH-Core
    set interfaces ae0 native-vlan-id ###
    set interfaces ae0 mtu 9192
    set interfaces ae0 aggregated-ether-options link-speed 10g
    set interfaces ae0 aggregated-ether-options lacp active
    set interfaces ae0 aggregated-ether-options lacp periodic fast
    set interfaces ae0 unit 0 family ethernet-switching interface-mode trunk
    set interfaces ae0 unit 0 family ethernet-switching vlan members Dxxx
    set interfaces ae0 unit 0 family ethernet-switching vlan members xxxxxT
    set interfaces ae0 unit 0 family ethernet-switching vlan members mm
    set interfaces ae0 unit 0 family ethernet-switching vlan members Qttttt
    set interfaces ae0 unit 0 family ethernet-switching vlan members blablabla

    Thank you,



    ------------------------------
    DONGYEONG KIM
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  • 2.  RE: Possible edge switch loop detected; Limit on MAC moves exceeded from uplink to ethernet port

    Posted 03-22-2023 08:34

    These frequent mac moves can indicate a layer 2 loop created generally by physical cabling and a lack of spanning tree to prevent the loop.

    since the move is between what appears to be an access port and an uplink the next place to check is looking for that mac address to appear on an access port of the connected uplink switch.  This would indicate the source port of the accidental loop.

    Another possibility is a second port linking the same two switches or through another switch that is missing spanning tree configuration to keep the link inactive until needed by the primary link failure.



    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP - Retired)
    http://puluka.com/home
    ------------------------------



  • 3.  RE: Possible edge switch loop detected; Limit on MAC moves exceeded from uplink to ethernet port

    Posted 03-24-2023 11:31

    Hi Steve,

    Thanks for your answer.

    In my case, uplink SW is core SW. My network is a typical hierarchical design;

    Core - edge - end device

                |_edge - end device

                ....

    I chased MAC from the edge to the core. Core indicated the same edge again. I will check again when it happens. I thought it was a bug , "junos feature" 

    Since I saw your comment, " lack of spanning tree," I read the configuration and technical docs. But I still cannot get what "lack of spanning tree" means. 



    ------------------------------
    DONGYEONG KIM
    ------------------------------



  • 4.  RE: Possible edge switch loop detected; Limit on MAC moves exceeded from uplink to ethernet port

    Posted 03-24-2023 11:41

    Spanning tree is a protocol that prevents layer 2 loops in standard vlan stack switching.

    From you diagram I wonder if you have a device with two ports connected to the same vlan on two edge switches that are then joined via the core.  This would be a typical way a loop can occur depending on the port configuration on the dual connected device.  And could result in the mac moves you note.



    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP - Retired)
    http://puluka.com/home
    ------------------------------