RE: PVST - MSTP interop : Error

Hi Gaurav,

In a mixed STP environment, the root of the common spanning-tree MUST be in
the MST region.
Having the root in the PVST region is not supported, as you can see in your
test.

Kind regards,
Gavin

CCIE #28459 (R&S)

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
GAURAV MADAN
Sent: 27 March 2011 07:40
To: Jakub Drwal
Cc: Cisco certification
Subject: Re: PVST - MSTP interop : Error

2nd try .. any other expert opinion on this ?
Cant we have PVST running switch as root in case which I mentioned .

Any thoughts are welcomed :)

Gaurav Madan

On Sat, Mar 26, 2011 at 1:34 PM, Jakub Drwal <jakub.drwal_at_gmail.com> wrote:

> Hi,
>
> As far as I remember only option in cisco's pvst-mst interoperability
> implementation is having root bridge for all vlans/instances at mst
region.
>
> regards,
>
> On Sat, Mar 26, 2011 at 8:45 AM, GAURAV MADAN
<gauravmadan1177_at_gmail.com>wrote:
>
>> Hi All
>>
>> As far as I know (from readings etc) :
>>
>> 1) In case of MSTP - PVSTP inter-op scenarios ; we should either have
>> [A] root for all vlans (all instances) in MST region
>> [B] root for all vlans on PVST switch
>>
>> 2) Having root for half vlans in MST region and half on PVST switch
>> is not a valid scenario and we will see PVST_Inc error in this .
>>
>> 3) Best practice suggest having root in MSTP region
>>
>> 4) However there is no stopping having root on PVST switch as well .
>>
>> Now My problem is following (My intent is to get SW2 PVST switch as
root):
>>
>> SW-1 (MSTP) g1/1---------------------g1/1- SW-2(PVST)
>> g1/2---------------------g1/2
>>
>> SW1 config
>> ===========
>> spanning-tree mode mst
>> spanning-tree extend system-id
>> !
>> spanning-tree mst configuration
>> name aa
>> revision 10
>> instance 1 vlan 1-5
>> instance 2 vlan 6-10
>> !
>> spanning-tree mst 1 priority 8192
>> spanning-tree mst 2 config 32768
>>
>> SW2 config
>> ========
>> !
>> spanning-tree mode pvst
>> spanning-tree extend system-id
>> spanning-tree vlan 1-4094 priority 4096 !
>>
>> At SW1 ; I am getting following error :
>> C4924(config)#
>> *Mar 26 06:39:35.735: %SPANTREE-2-PVSTSIM_FAIL: Blocking root port Gi1/1:
>> Inconsitent inferior PVST BPDU received on VLAN 2, claiming root
>> 2:0024.1430.2f00
>>
>> C4924#sh span mst 1
>>
>> ##### MST1 vlans mapped: 1-5
>> Bridge address 001d.450d.0700 priority 8193 (8192 sysid 1)
>> Root this switch for MST1
>>
>> Interface Role Sts Cost Prio.Nbr Type
>> ---------------- ---- --- --------- --------
>> --------------------------------
>> Gi1/1 Mstr BKN*20000 144.1 P2p Bound(PVST) *PVST_Inc
>> Gi1/2 Altn BLK 20000 128.2 P2p Bound(PVST)
>>
>> C4924#sh span mst 2
>>
>> ##### MST2 vlans mapped: 6-10
>> Bridge address 001d.450d.0700 priority 32770 (32768 sysid 2)
>> Root this switch for MST2
>>
>> Interface Role Sts Cost Prio.Nbr Type
>> ---------------- ---- --- --------- --------
>> --------------------------------
>> Gi1/1 Mstr BKN*20000 128.1 P2p Bound(PVST) *PVST_Inc
>> Gi1/2 Altn BLK 20000 128.2 P2p Bound(PVST)
>>
>> Please let me know where am i wrong ?
>>
>> Thanks
>> Gaurav Madan
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
>> _____________________________________________________________________
>> __ Subscription information may be found at:
>> http://www.groupstudy.com/list/CCIELab.html
>>
>>
>>
>>
>>
>>
>>
>>
>
>
> --
> Jakub Drwal

Blogs and organic groups at http://www.ccie.net
Received on Tue Mar 29 2011 - 19:41:22 ART