Re: Spanning-tree root port selection

Thank you Joe

Regards
Anantha Subramaniann Natarajan

On Tue, Sep 15, 2009 at 2:21 PM, Joe Astorino <jastorino_at_ipexpert.com>wrote:

> Thats what I'm saying Divin : ) The BID is not the first thing to be
> checked...it does not come into play until the lowest cost to the root is
> the same...THEN we take into account the lowest BID.
>
>
> On Tue, Sep 15, 2009 at 3:18 PM, Divin Mathew John <divinjohn_at_gmail.com>wrote:
>
>> hey!
>> its
>> 1) Lowest Cost to root
>> 2) Lowest BID of upstream device
>> 3) Lowest upstream portid.priority
>> 4) If all the 3 are the same then lowest interface ID on local switch
>>
>> @Joe. BID comes into play when u have 2 paths of the same cost to root
>> bridge! it serves as a tie breaker!
>>
>>
>> On Wed, Sep 16, 2009 at 12:43 AM, Joe Astorino <jastorino_at_ipexpert.com>wrote:
>>
>>> Let me clarify -- I don't see how the BID ties into the root-port
>>> selection
>>> process BEFORE the lowest cost path to the root bridge. The way I
>>> understand the algorithm is that the first thing checked is the lowest
>>> cost
>>> path to the root bridge, not the lowest BID. Now, if things are tied,
>>> yes I
>>> agree we look at lowest sender BID.
>>>
>>> On Tue, Sep 15, 2009 at 3:12 PM, Joe Astorino <jastorino_at_ipexpert.com
>>> >wrote:
>>>
>>> > I don't see how the lowest BID ties into electing a root-port on a
>>> non-root
>>> > bridge. The election so far as I know is based on what you originally
>>> > said. If I am incorrect, please reference some documentation.
>>> >
>>> > On Tue, Sep 15, 2009 at 2:54 PM, Anantha Subramanian Natarajan <
>>> > anantha.natarajan_at_gravitant.com> wrote:
>>> >
>>> >> Hi Guarav,
>>> >>
>>> >> Thanks for the response.Actually the below mentioned is true for
>>> all,but
>>> >> when all those tied,which may be in the case where the topology in
>>> which
>>> >> hub
>>> >> is in between and the non-root bridge is having 2 connections to it.In
>>> >> that
>>> >> scenario,I am understanding that the local port id would be choosed as
>>> tie
>>> >> breaker.If that is wrong,kindly correct me again.
>>> >>
>>> >> Thanks for the help
>>> >>
>>> >> Regards
>>> >> Anantha Subramanian Natarajan
>>> >>
>>> >>
>>> >>
>>> >> On Tue, Sep 15, 2009 at 1:36 PM, GAURAV MADAN <
>>> gauravmadan1177_at_gmail.com
>>> >> >wrote:
>>> >>
>>> >> > Small error ...
>>> >> >
>>> >> > Correct one is
>>> >> >
>>> >> > Lowest BID
>>> >> > Lowest root path cost
>>> >> > Lowest sender Bridge Id
>>> >> > Lowest sender Port Id
>>> >> >
>>> >> > HTH
>>> >> > Gaurav Madan
>>> >> > CCIE
>>> >> >
>>> >> > On Tue, Sep 15, 2009 at 11:58 PM, Anantha Subramanian Natarajan
>>> >> > <anantha.natarajan_at_gravitant.com> wrote:
>>> >> > > Hi All,
>>> >> > >
>>> >> > > When I went through LAN Switching Book,I understood the
>>> below(Please
>>> >> > > correct me,If I am wrong)
>>> >> > >
>>> >> > > In the below scenario(Same Hub)
>>> >> > >
>>> >> > > SW1(Root Bridge) ---------Hub --------- SW2
>>> >> > > Hub ----------SW2
>>> >> > >
>>> >> > > When SW2 tries to calculate its root port to the root bridge,by
>>> >> default
>>> >> > all
>>> >> > > the parameters(Path cost,sender bridge-id,port ID information SW1)
>>> all
>>> >> > > ties,the SW2 uses it *local port ID* for the tie breaker. Is my
>>> >> > > understanding right ? If so,when a question comes to describe a
>>> root
>>> >> port
>>> >> > > selection ,should I need to mention this also like as below
>>> >> > >
>>> >> > > 1)Highest Root path cost
>>> >> > > 2)Lowest sender bridge-id
>>> >> > > 3) Lowest sender Bridge port ID
>>> >> > > 4)* Lowest local port ID ,if all the above Tie*
>>> >> > > **
>>> >> > > Kindly correct me if I am wrong.
>>> >> > >
>>> >> > > Thank you very much
>>> >> > >
>>> >> > > Regards
>>> >> > > Anantha Subramanian Natarajan
>>> >> > >
>>> >> > >
>>> >> > > Blogs and organic groups at http://www.ccie.net
>>> >> > >
>>> >> > >
>>> >>
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>>> >
>>> >
>>> > --
>>> > Regards,
>>> >
>>> > Joe Astorino - CCIE #24347 R&S
>>> > Technical Instructor - IPexpert, Inc.
>>> > Cell: +1.586.212.6107
>>> > Fax: +1.810.454.0130
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>>> >
>>>
>>>
>>>
>>> --
>>> Regards,
>>>
>>> Joe Astorino - CCIE #24347 R&S
>>> Technical Instructor - IPexpert, Inc.
>>> Cell: +1.586.212.6107
>>> Fax: +1.810.454.0130
>>> Mailto: jastorino_at_ipexpert.com
>>>
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>>>
>>>
>>>
>>
>>
>> --
>>
>>
>> Edwin Schlossberg <http://www.quotationspage.com/quote/30527.html> -
>> "The skill of writing is to create a context in which other people can
>> think."
>
>
>
>
> --
> Regards,
>
> Joe Astorino - CCIE #24347 R&S
> Technical Instructor - IPexpert, Inc.
> Cell: +1.586.212.6107
> Fax: +1.810.454.0130
> Mailto: jastorino_at_ipexpert.com

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Received on Tue Sep 15 2009 - 14:22:10 ART