Cisco 3750 Switch Stacking issue - Stack ports flapping

[ecesureshkumar]

Hi there,

We have four 3750 switch in stacking and connected in ring topology.

We are facing issue in switch stacking and we getting following errors in switch logs. From the attached logs we are noticing switch 1 stack ports and connected ports are flapping continuously and stacking connectivity is aslike below.

So we suspect the cable connecting switch 1 to switch 4 is having issue and more over we plan to replace that cable. while replacing the cable, will there be any distrubance in production traffic. As these switches are serving critical application, we need your inputs on this.

[Leo Laohoo]

Post the output to the command "sh inventory".  It could be that your 3750 is part of a production defect.

[ecesureshkumar]

Hi Leo, please find the show inventory output

sh inventory
NAME: "1", DESCR: "WS-C3750X-48"
PID: WS-C3750X-48T-S   , VID: V02  , SN: FDO1548K0UJ

NAME: "Switch 1 - Power Supply 1", DESCR: "FRU Power Supply"
PID: C3KX-PWR-350WAC   , VID: V02L , SN: LIT15480YDE

NAME: "Switch 1 - FRULink Slot 1 - FRULink Module", DESCR: "FRULink 1G Module"
PID: C3KX-NM-1G        , VID: V01  , SN: FDO15490ZWM

NAME: "2", DESCR: "WS-C3750X-48"
PID: WS-C3750X-48T-S   , VID: V02  , SN: FDO1548P155

NAME: "Switch 2 - Power Supply 0", DESCR: "FRU Power Supply"
PID: C3KX-PWR-350WAC   , VID: V02L , SN: LIT15480YB4

NAME: "Switch 2 - FRULink Slot 1 - FRULink Module", DESCR: "FRULink 1G Module"
PID: C3KX-NM-1G        , VID: V01  , SN: FDO15490UCK

NAME: "3", DESCR: "WS-C3750X-48"
PID: WS-C3750X-48T-S   , VID: V02  , SN: FDO1548R15E

NAME: "Switch 3 - Power Supply 0", DESCR: "FRU Power Supply"
PID: C3KX-PWR-350WAC   , VID: V02L , SN: LIT15480YG9

NAME: "Switch 3 - Power Supply 1", DESCR: "FRU Power Supply"
PID: C3KX-PWR-350WAC   , VID: V02L , SN: LIT15480YBF

NAME: "Switch 3 - FRULink Slot 1 - FRULink Module", DESCR: "FRULink 1G Module"
PID: C3KX-NM-1G        , VID: V01  , SN: FDO15490UCX

NAME: "4", DESCR: "WS-C3750X-48"
PID: WS-C3750X-48T-S   , VID: V02  , SN: FDO1548R0VY

NAME: "Switch 4 - Power Supply 0", DESCR: "FRU Power Supply"
PID: C3KX-PWR-350WAC   , VID: V02L , SN: LIT15480YAQ

NAME: "Switch 4 - FRULink Slot 1 - FRULink Module", DESCR: "FRULink 1G Module"
PID: C3KX-NM-1G        , VID: V01  , SN: FDO15490ZWF

[Leo Laohoo]

The problem is switch 1 and not the cable linking 1 and 4.

Can you ensure the cables are screwed properly?

[ecesureshkumar]

Hi Leo, I verified cables are screwed properly and how you confirming issue with Switch 1 and not with cable linking 1 & 4.

[Leo Laohoo]

Yes.  Look at the image you posted.  It mentions the link between switch 1 and 4, switch 1 and 2.  The common denominator here is switch 1.

Replace both cables coming out of switch 1.  If problem persist, RMA switch 1.

[ecesureshkumar]

Hi all,

After replacing the stack cables, issue got resolved and we replaced stack cable one by one, from switch 1 to switch 4 and then from switch 1 to switch 2. while doing this cable change no downtime required.