Re: MSTP IST( MSTI0) vs MIST confusion

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)
> >>
> >>
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> >>
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> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >
> >
> > --
> > 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
>
>
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-- 
Regards,
Joe Astorino
CCIE #24347
Blog: http://astorinonetworks.com
"He not busy being born is busy dying" - Dylan
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