Re: MSTP IST( MSTI0) vs MIST confusion

Thanks a lot Joe that was a great document ..

On Thu, Sep 8, 2011 at 2:10 AM, Joe Astorino <joeastorino1982_at_gmail.com>wrote:

> Petr from INE has a very nice article on it here
> http://blog.ine.com/2010/02/22/understanding-mstp/#MSTI_TO_CIST
>
>
>
> On Wed, Sep 7, 2011 at 3:58 PM, CCIE KID <eliteccie_at_gmail.com> wrote:
>
>> 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
>>
>
>
>
> --
> Regards,
>
> Joe Astorino
> CCIE #24347
> Blog: http://astorinonetworks.com
>
> "He not busy being born is busy dying" - Dylan
>
>

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