One of the ISL link down on BES cluster switch

• ONTAP 9
• BES-53248 Cluster Switch

• The system reports SwitchIslIfDownWarn_Alert alert in event logs

Mon Aug 25 12:26:21 -0700 [node1: cshmd: hm.alert.raised:alert]: Alert Id = SwitchIslIfDownWarn_Alert , Alerting Resource = switch2/Slot: 0 Port: 56 100G - Level cleared by monitor ethernet-switch

• System health reports the following 

Detailed Problem Description: Node: Node1
           Alert ID: SwitchIslIfDownWarn_Alert
           Resource: Slot: 0 Port: 56 100G - Level
           Severity: Major
    Indication Time: Thu Jan 15 11:57:07 2026
           Suppress: false
        Acknowledge: false
     Probable Cause: The cable attached to the ISL port "switch1/Slot:
                     0 Port: 56 100G - Level" with the description of
                     "Cluster ISL Port" might be faulty. For the
                     port-channel, please check each individual link.
    Possible Effect: Inter- or Intra- cluster redundancy might be lost.
Corrective Actions: 1) Check whether the cable is fully inserted into the interface port on both ends.
                     2) Reconnect the ISL port using another cable. After
                     reconnecting it, verify whether the link of the ISL
                     port is up by executing the commands per the switch
 configuration guide or by checking whether the Link
                     status LED is on. 

• Switch logs reports the ISL link to be down 

*************** show port all ***************
                 Admin     Physical   Physical   Link   Link    LACP   Actor
Intf      Type   Mode      Mode       Status     Status Trap    Mode   Timeout
--------- ------ --------- ---------- ---------- ------ ------- ------ --------

0/55      PC Mbr Enable    Auto       100G Full  Up     Enable  Enable long
0/56      PC Mbr Enable    Auto                  Down   Enable  Enable long