Re: Spanning-tree root port selection

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
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