Re: Spanning-tree root port selection

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
> > Mailto: jastorino_at_ipexpert.com
> >
>
>
>
> --
> 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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