Re: MSTP IST( MSTI0) vs MIST confusion

Thanks a lot Hemanth Got the point completely.
Do u have any scenarios or case studies which describes MSTP in depth.

On Wed, Sep 7, 2011 at 11:49 PM, HEMANTH RAJ <hemanthrj_at_gmail.com> wrote:

> Hi Kid,
>
> Yes Joe is spot on. M-Records contain the information about the root
> priority, designated bridge priority, port priority and root path cost among
> others using the extended TLV's for the specific instances which maps for
> various vlans.
>
> IST also contain the same information for vlans which are not the part of
> instances. MSTI's are again not a separate BPDU's . It is just been attached
> with IST's
>
> To answer ur question more specifically about the contents in the MSTP
> BPDu's, the major contents are the CIST Root Identifier , CIST Bridge ID,
> CIST Regional Root ID, CIST Port ID and CIST External and Internal root
> path cost. Inside each region in MSTP they have Regional Root and across the
> boundaries they have CIST Root . Inside each region , they share the IST
> which informs the entire logical topological information about the instances
> and also the vlans which maps to that instances.
>
> There is also field called as Remaining Hops (which is the maximum hops)
> in the MSTP BPDU which states that a downstream switch should decrement
> the hop count field on reception of IST BPDU. As soon as hop count becomes
> zero, the information in BPDU is ignored, and the switch may start declaring
> itself as a new IST root.
>
> There is also a thing which should be understood in MSTP is IST Root is
> equal to the CIST Regional Root.
>
> CIST Root is the bridge that has the lowest Bridge ID among ALL regions.
> This could be a bridge inside a region or a boundary switch in a region.
>
> CIST Regional Root is a boundary switch elected for every region based on
> the shortest external path cost to reach the CIST Root. Path cost is
> calculated based on costs of the links connecting the regions, excluding the
> internal regional paths.
>
> I hope this will clear ur mind :)
>
>
>
>
>
>
>
>
>
>
> On Wed, Sep 7, 2011 at 7:45 PM, Joe Astorino <joeastorino1982_at_gmail.com>wrote:
>
>> MST does not carry the spanning-tree information for all the different
>> MSTIs in a separate packet. So, what it does is send the spanning-tree
>> characteristics for each MSTI in M-Records. The M-Records contain all that
>> informatino per MSTI like port-priority, root path cost, etc
>>
>> HTH
>>
>>
>> On Wed, Sep 7, 2011 at 9:45 AM, CCIE KID <eliteccie_at_gmail.com> wrote:
>>
>>> Thanks a lot hemanth .Gud explanation.
>>>
>>> One more question What does M-Record contain and wat r the contents in
>>> IST
>>> BPDU . What is the difference between the contents in M-Record and IST
>>> BPDUs
>>> ?
>>>
>>>
>>>
>>> On Wed, Sep 7, 2011 at 6:54 PM, HEMANTH RAJ <hemanthrj_at_gmail.com> wrote:
>>>
>>> > Hi kid,
>>> >
>>> > IST is nothing but ur MST Instance 0 which mainly serves the purpose
>>> of
>>> > distributing STP topology information for MST Instances. IST has a
>>> root
>>> > bridge, elected based on the lowest Bridge ID (Bridge Priority + MAC
>>> > address). The situation changes with multiple MSTP regions in the
>>> network.
>>> >
>>> > By default, all VLANs are mapped to the IST .Other MSTP instances could
>>> be
>>> > enabled and they are referred to as Multiple Spanning Tree Instances
>>> > (MSTIs). Every MSTI assign its own priorities to the switches and use
>>> its
>>> > own link costs to come up with a private logical topology which is
>>> separate
>>> > from IST
>>> >
>>> > Since MSTP does not send MSTI s information in separate BPDUs, this
>>> > information is attached into the IST s BPDUs using special M-Record
>>> fields.
>>> > I think these M-Records are one for every active MST Instances. They
>>> have
>>> > extended TLVs to do that I guess if i remember correctly.
>>> >
>>> > I hope this helps u
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > On Wed, Sep 7, 2011 at 2:33 PM, CCIE KID <eliteccie_at_gmail.com> wrote:
>>> >
>>> >> Hi fellas,
>>> >>
>>> >> I am reading MSTP and i came across two terminologies IST and MIST.
>>> >> IST is used to send all the BPDU related information which is all the
>>> >> information regarding which VLANS mapped to which instances and to
>>> >> maintain
>>> >> consistency check on all the switches.
>>> >> Now there is a line which states " *MSTI information is attached to
>>> IST *"
>>> >> What does MSTI carry and why does it use IST for that
>>> >> Correct me if i am wrong in understanding the logic.
>>> >>
>>> >> I have a confusion regarding Internal Spanning tree (IST) aka MST
>>> Instance
>>> >> 0 and Multiple Intances of Spanning tree(MIST). Can some point me
>>> what
>>> >> is
>>> >> the difference between IST and MST ?
>>> >>
>>> >> --
>>> >> With Warmest Regards,
>>> >>
>>> >> CCIE KID
>>> >> CCIE#29222 ( SECURITY)
>>> >>
>>> >>
>>> >> Blogs and organic groups at http://www.ccie.net
>>> >>
>>> >>
>>> _______________________________________________________________________
>>> >> Subscription information may be found at:
>>> >> http://www.groupstudy.com/list/CCIELab.html
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
>>> >>
>>> >
>>> >
>>> > --
>>> > Problems arise because we talk,problems are not solved because we don't
>>> > talk So good or bad talk to your affectionate one's freely.
>>> >
>>> > Yours Friendly,
>>> > H P HEMANTH RAJ
>>> > CCIE#28593 (R&S)
>>> > Cisco Systems
>>> >
>>> >
>>>
>>>
>>> --
>>> With Warmest Regards,
>>>
>>> CCIE KID
>>>
>>>
>>> Blogs and organic groups at http://www.ccie.net
>>>
>>> _______________________________________________________________________
>>> Subscription information may be found at:
>>> http://www.groupstudy.com/list/CCIELab.html
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>> --
>> Regards,
>>
>> Joe Astorino
>> CCIE #24347
>> Blog: http://astorinonetworks.com
>>
>> "He not busy being born is busy dying" - Dylan
>>
>>
>
>
> --
> Problems arise because we talk,problems are not solved because we don't
> talk So good or bad talk to your affectionate one's freely.
>
> Yours Friendly,
> H P HEMANTH RAJ
> CCIE#28593 (R&S)
> Cisco Systems
>
>

-- 
With Warmest Regards,
CCIE KID
IN PURSUIT OF CCIE
Blogs and organic groups at http://www.ccie.net