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multiple switches uplink failed

Posted on 2016-09-12
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Last Modified: 2016-09-13
i hope someone can provide some clue.
all of sudden multiple cisco switches uplink failed with orange light and caused users inaccessible to network
after power cycle each switch, it was back to normal.
l checked show log but did not see any hint.
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Question by:techy98
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by:Predrag Jovic
ID: 41794298
all of sudden multiple cisco switches uplink failed with orange light and caused users inaccessible to network
That is typically happening when you add switch with better VTP revision into network - it overwrites all of your existing VLANs with VLANs on new switch.
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by:techy98
ID: 41794309
besides adding a new switch, would it be possible of configuring SPAN  monitor session on a port channel of 2 ge interfaces as source?
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by:Predrag Jovic
ID: 41794342
I forgot about one detail, restart in this case of higher VTP revision should not help. So I guess VTP should not cause this behavior.
In that case I can't think of mechanism to cause what you are describing.
Not sure about SPAN, but if you send 2Gb of traffic through 1 GB link it can cause problems for sure (but I guess not those that you described, at least not easy).
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Author Comment

by:techy98
ID: 41794350
in the switch that configured with monitor session on port channel, there was an error EC-5-UNSUITABLE: [chars] will not join any port-channel, [chars].
would it be something related?
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by:Predrag Jovic
ID: 41794361
That can be a problem. :)
Error Message    EC-5-UNSUITABLE: [chars] will not join any port-channel, [chars].

Explanation    This message means that one of the interfaces cannot join the EtherChannel because it is configured for PortFast, as a VLAN Membership Policy Server (VMPS), for 802.1X, as a voice VLAN, or as a Switched Port Analyzer (SPAN) destination port. All of these are unsuitable configurations for EtherChannels. The first [chars] is the interface name, and the second [chars] describes the details of the unsuitable configuration.

Recommended Action    Reconfigure the port; remove the unsuitable configuration.
Looks like traffic from port channel came to a wrong place.
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Author Comment

by:techy98
ID: 41794377
thanks for durther detail. so do you think it`s likely to cause STP blocking on issue that I had?
it was nit affect all switch but only some of them.
those affected switches were on differernt vlan from the one that configured for SPAN
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Author Comment

by:techy98
ID: 41794378
thanks for durther detail. so do you think it`s likely to cause STP blocking on issue that I had?
it was nit affect all switch but only some of them.
those affected switches were on differernt vlan from the one that configured for SPAN
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by:Predrag Jovic
ID: 41794439
so do you think it`s likely to cause STP blocking on issue that I had?
I guess STP could be root cause, or any of mechanisms that can err-disable port. However you restarted switch and ports were no longer in err-disable so you can establish root cause.
# show interface status err-disabled
can show you root cause in this case.
Also possible causes can be any of active err-disable mechanisms:

# show errdisable recovery
ErrDisable Reason    Timer Status
-----------------    --------------
udld
bpduguard
security-violatio
channel-misconfig
pagp-flap
dtp-flap
link-flap
l2ptguard
psecure-violation
gbic-invalid
dhcp-rate-limit
mac-limit
unicast-flood
arp-inspection
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Author Comment

by:techy98
ID: 41795920
I tried with the command you suggested. The first one show interface status err-disable but did not return anything.
Then show errdisable recovery and all items are showing disable.
Would it because those affected switches already back online? Therefore, there was not clue could be traced.
It was weird only 3-4 switches' uplink were failed and affect other 10 switches that had uplink to these 3-4 switches.
Even though I suspect it was due to the setup of SPAN on an interface (destination port) that was configured with switchport access to a vlan and set as spanning-tree portfast as well as root guard, how it was impacted to other switches?
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Accepted Solution

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Predrag Jovic earned 500 total points
ID: 41796105
Since problem was solved by restart and there are no logs that can  definitively point to root cause there is no easy way (or not way at all) to be sure about root cause in your case.
So, if you do not experience the same thing again and have time to actually find root cause (and typically there is not much time if production is down) I can only guess what can be root cause. So, I can only hope that you experience the same thing again and have time to look into it. But, I also guess it is the last thing that you want to experience.
 :)
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Author Closing Comment

by:techy98
ID: 41797307
again...thanks so much! i believe those command you suggested would help.
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