ISL port down between Cisco Cluster Network Switches

Applies to

Issue

•  The switch ISL link for port 35 is showing as down.
•   Switch side output of ISL ports:

sw1 # show port-channel databaseport-channel1    
Last membership update is successful    
2 ports in total, 1 ports up    
First operational port is Ethernet1/36    
Age of the port-channel is 948d:00h:09m:41s    
Time since last bundle is 948d:00h:09m:41s    
Last bundled member is Ethernet1/36    
Ports:   Ethernet1/35    [active ] [down]             
Ethernet1/36    [active ] [up] *

Switch 2:
Sw2 # show port-channel databaseport-channel1    
Last membership update is successful    
2 ports in total, 1 ports up    
First operational port is Ethernet1/36    
Age of the port-channel is 947d:23h:53m:19s    
Time since last bundle is 947d:23h:53m:17s    
Last bundled member is Ethernet1/36    Ports:   
Ethernet1/35  [active ] [down]             
Ethernet1/36    [active ] [up] *

•  See the following alerts in the EMS log

 [?]  Tue Mar 04 19:42:47 -0500 [node1: cshmd: hm.alert.raised:alert]: Alert Id = ClusterIfIslDownWarn_Alert , Alerting Resource = sw1(xxxxx)/Ethernet1/35 raised by monitor ethernet-switch 
 [?]  Tue Mar 04 19:42:47 -0500 [node1: cshmd: hm.alert.raised:alert]: Alert Id = ClusterIfIslDownWarn_Alert , Alerting Resource = sw2(xxxxx)/Ethernet1/35 raised by monitor ethernet-switch 
 [?]  Tue Mar 04 20:00:23 -0500 [node1: cshmd: hm.alert.cleared:notice]: Alert Id = ClusterIfIslDownWarn_Alert , Alerting Resource = sw1(xxxxx)/Ethernet1/35 cleared by monitor ethernet-switch [?]  Tue Mar 04 20:00:23 -0500 [node1: cshmd: hm.alert.cleared:notice]: Alert Id = ClusterIfIslDownWarn_Alert , Alerting Resource = sw2(xxxxx)/Ethernet1/35 cleared by monitor ethernet-switch