We have a stack of 4 SG-500 switches.
Since a couple of months some ports of the stack are going up and down randomly. Mostly the ports S3 and S4 of the member 1 (master).
Usually this flapping doesn't cause any impact in the production environment (at least at first sight), but sometimes, when both ports of member 1 (S3 and S4) goes down at the same time, all the users connected to the stack loose whole connectivity with the rest of the network.
Switches are configured as native stack and Ring Topology. we are using original stack cables from Cisco.
Firmware version: 1.4.0.88.
Boot version: 1.4.0.02.
05-Apr-2018 13:43:19 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%FFO-I-FFO-OPER: Fast Failover is enabled
05-Apr-2018 13:43:19 :%FFO-I-FFO-OPER: Fast Failover is enabled
05-Apr-2018 13:43:17 :%STCK SYSL-I-UNITMSG: UNIT ID 4,Msg:%FFO-I-FFO-OPER: Fast Failover is enabled
05-Apr-2018 13:43:17 :%STCK SYSL-I-UNITMSG: UNIT ID 3,Msg:%FFO-I-FFO-OPER: Fast Failover is enabled
05-Apr-2018 13:43:17 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%CSCDLAG-I-ACTIVE: Stack port S3 is active in stack LAG 2
05-Apr-2018 13:43:17 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%CSCDLAG-I-UP: Stack port S3 operational status is UP
05-Apr-2018 13:43:17 :%CSCDLAG-I-ACTIVE: Stack port S4 is active in stack LAG 2
05-Apr-2018 13:43:17 :%CSCDLAG-I-UP: Stack port S4 operational status is UP
05-Apr-2018 13:43:15 :%FFO-I-FFO-COMPLETE: Fast Failover is disabled
05-Apr-2018 13:43:15 :%STCK SYSL-I-UNITMSG: UNIT ID 2,Msg:%FFO-I-FFO-COMPLETE: Fast Failover is disabled
05-Apr-2018 13:43:15 :%STCK SYSL-W-UNITMSG: UNIT ID 2,Msg:%FFO-W-FFO-ACTIVE: Fast Failover is triggered
05-Apr-2018 13:43:15 :%STCK SYSL-W-UNITMSG: UNIT ID 2,Msg:%CSCDLAG-W-DOWN: Stack port S3 operational status is Down
05-Apr-2018 13:43:14 :%STCK SYSL-I-UNITMSG: UNIT ID 4,Msg:%FFO-I-FFO-COMPLETE: Fast Failover is disabled
05-Apr-2018 13:43:14 :%STCK SYSL-I-UNITMSG: UNIT ID 3,Msg:%FFO-I-FFO-COMPLETE: Fast Failover is disabled
05-Apr-2018 13:43:14 :%FFO-W-FFO-ACTIVE: Fast Failover is triggered
05-Apr-2018 13:43:14 :%CSCDLAG-W-DOWN: Stack port S4 operational status is Down
