6500 VSS

Hi All,

A 6506 VSS is experiencing a strange behavior.  The VSS is formed with two etherchannel with t1/5/4, t1/5/5 and t2/5/4 and t2/5/5. We thought the behavior was caused by a bad VSL link at first  on t1/5/5 and t2/5/5 when I see the logs below from the system. These events caused the active switch stop responding and couldn't process any traffic, a eigrp neighbor that's connected to only the active lost which makes me think the VSS is recalculating the role..etc. As I checked for the VSS to see if the standby was trying to become active or the history of the VSS role and other detail. I did not find any indication of the VSS role change but the one of the VSL cable fails. Also, there were no dual active detected.

Sep 8 15:27:39 EDT: %VSLP-SW2_SP-3-VSLP_LMP_FAIL_REASON: Te2/5/5: Link down
Sep 8 15:29:04 EDT: %VSLP-SW1_SPSTBY-3-VSLP_LMP_FAIL_REASON: Te1/5/5: Link down
Sep 8 15:29:04 EDT: %VSLP-SW2_SP-3-VSLP_LMP_FAIL_REASON: Te2/5/5: Link down
Sep 8 15:30:07 EDT: %VSLP-SW1_SPSTBY-3-VSLP_LMP_FAIL_REASON: Te1/5/5: Link down

After we received the new transceivers and cable. we swapped them out. The first 2 minutes were okay but the behavior came back after. This time, the port stated up, I didn't see any log indicate the link come down nor flop. As soon as we unplug the cable from the switch from both ports T1/5/5 and T2/5/5. The switch started to operate normal again. As for now, we're running the VSS via one cable. until i can schedule another maintenance window to troubleshoot this further. At this time, I wonder if anyone has experienced this same or similar issue.

May I ask what could be the issue here? why would the single link caused such behavior. The other VSL link was operating normally and keeping the VSS state the whole time.

Thanks,

Matt
Matt TseAsked:
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Matt TseAuthor Commented:
We believe because Te1/5/5 was elected as the VSL control link. When its status flopped up and down due to a hardware issue (cable and/or the transceiver or even the SUP), the VSL status changed from up to down that caused the VSS to recalculate.

During a building shutdown took place a week after this issue occurred, the SUP experienced a hardware failure. We replaced the SUP, VSL cable, and the transceiver on Port T1/5/5 and T2/5/5.

The VSS had been running fine for a week without any problem now.
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Craig BeckCommented:
Can you show the config?
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Matt TseAuthor Commented:
Hey Craig,
Attached are some of the config

Thanks!
6500_output.zip
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Craig BeckCommented:
All looks ok there.

I'm wondering... do you get the same issue if you enable gratuitous arps?
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Matt TseAuthor Commented:
we haven't tried that yet.  but all these time we never have gratuitous arp enable on the VSS. The cable on the same port gone bad 2 years ago. we replaced the cable and that time, it didn't have any problem. If anything, I will have to set up a maintenance window to test.

I'm confused as to why plugging in the cable would cause that problem when the VSS role and status is still maintaining by the working cable on T1/5/4 and T2/5/4.
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Craig BeckCommented:
It may be upsetting the etherchannel.  Is there another linecard you can use for one of the VSLs?
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Matt TseAuthor Commented:
No, unfortunately.
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Matt TseAuthor Commented:
The fix we had resolved the issue.
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