Re: rapid-pvst vs mst in recalculation of spanning tree

Hello Joe and Shaun,

The issue was stp recalc for all vlans listed under the port-channel.
The Port-channel is connected to storage using lacp negotiation.
This is the output of the -------- show etherchan 17 sum:

Group Port-channel Protocol Ports
------+-------------+-----------+-----------------------------------------------
17 Po17(SD) LACP
17 Po17A(SU) LACP Gi6/21(P) Gi6/22(P)

We opened a case with Cisco and it turned out to be lacp bug in our current
switch code.
This bug resulted in the creation of a virtual channel and that was the
reason that STP recalculated.
The workaround is to disable lacp negotiation.

Thanks Shaun and Joe

On Fri, Dec 4, 2009 at 10:38 AM, Joe Astorino <jastorino_at_ipexpert.com>wrote:

> Well, you are essentially adding a port into the STP processes running for
> each VLAN you add to the trunk. In RSTP a "change" is indicated by a port
> going up so I would think that it will reconverge for just the VLANs you are
> adding. MST uses RSTP internally, so I would not think there would be a
> difference there. I would expect it would converge for any MST instance
> that has a VLAN you added as a member of it.
>
> On Fri, Dec 4, 2009 at 1:33 AM, Mad_Prof Mad_Prof <dr3d3m3nt0_at_gmail.com>wrote:
>
>> Hello All,
>>
>>
>> I am trying to find out if STP is recalculated for all vlans in the
>> process of adding a trunk to a switch:
>>
>> interface Port-channel17
>> switchport trunk encapsulation dot1q
>> switchport trunk allowed vlan 13,17-32,56,87
>> switchport mode trunk
>> spanning-tree guard root
>>
>>
>> and would a difference whether the switch is in rapid-pvst or mst ?
>>
>> Any assistance is greatly appreciated.
>>
>>
>>
>>
>> It is said that if you know your enemies and know yourself, you will not
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>> know
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>> nor
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>>
>>
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>
>
> --
> Regards,
>
> Joe Astorino CCIE #24347 (R&S)
> Sr. Technical Instructor - IPexpert
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-- 
It is said that if you know your enemies and know yourself, you will not be
imperiled in a hundred battles; if you do not know your enemies but do know
yourself, you will win one and lose one; if you do not know your enemies nor
yourself, you will be imperiled in every single battle.
Blogs and organic groups at http://www.ccie.net