Re: Root port

Yes, definitely cost does not only effect your switch in a bigger environment...in this particular case port cost on D only effects D since there are no downstream switches.

What I meant by "local" is that changing cost on R (the remote end) does absolutely nothing since that outbound port cost is not taken into account at R. R as the root simply sends a BPDU with a cost of 0 to D.

To see the received port priority take a look at "sh spanning-tree interface detail" and look for the Designated Port priority.

Sent from my Verizon Wireless BlackBerry

Regards,

 Joe Astorino - CCIE #24347
Sr. Technical Instructor - IPexpert
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-----Original Message-----
From: Carlos G Mendioroz <tron_at_huapi.ba.ar>
Date: Wed, 21 Apr 2010 10:16:55
To: <jastorino_at_ipexpert.com>
Cc: just kennie<justkennie_at_gmail.com>; CCIE Groupstudy<ccielab_at_groupstudy.com>
Subject: Re: Root port

Hmm,
I reacted to your calling port cost a local thing. It is, concepually,
hardly so.
Priority on the other side, only applies to a particular link, and I'm
fine with calling this a local thing.

I don't remember port priority as a BPDU field, but I do see neighbour
priority along local priority in the output of some commands, so
definitly some labbing might help me straight this out.

Thanks.

Joe Astorino @ 21/4/2010 9:59 -0300 dixit:
> Also let me just say you are right about port cost...I am not saying it ONLY influences your switch because obviously the cost is sent down stream to other switches.
>
> However, the outbound interface cost is not taken into consideration. In this case with only 2 switches the port cost set on R means absolutely nothing to D. The port priority set locally on D means absolutely nothing when D calculates the root port.
>
> The received port priority D gets in the BPDU from R is what will matter if you do not alter port cost on D
>
> Again, a simple lab test will confirm this for you
>
>
> Sent from my Verizon Wireless BlackBerry
>
> Regards,
>
> Joe Astorino - CCIE #24347
> Sr. Technical Instructor - IPexpert
> Mailto: jastorino_at_ipexpert.com
> Telephone: +1.810.326.1444
> Live Assistance, Please visit: www.ipexpert.com/chat
> eFax: +1.810.454.0130
>
> IPexpert is a premier provider of Self-Study Workbooks, Video on Demand, Audio Tools, Online Hardware Rental and Classroom Training for the Cisco CCIE (R&S, Voice, Security & Service Provider) certification(s) with training locations throughout the United States, Europe, South Asia and Australia. Be sure to visit our online communities at www.ipexpert.com/communities and our public website at www.ipexpert.com
>
> -----Original Message-----
> From: Carlos G Mendioroz <tron_at_huapi.ba.ar>
> Date: Wed, 21 Apr 2010 09:50:15
> To: Joe Astorino<jastorino_at_ipexpert.com>
> Cc: just kennie<justkennie_at_gmail.com>; CCIE Groupstudy<ccielab_at_groupstudy.com>
> Subject: Re: Root port
>
> Joe,
> Either I'm confused or...
>
> Port priority is a local thing, and port cost is what STP adds up to
> inform the rest of the connected network the path cost to the root,
> so hardly a local thing.
>
> -Carlos
>
> Joe Astorino @ 21/4/2010 8:34 -0300 dixit:
>> What you read is simply not true. STP cost is a local thing. If you want to influence the root port of B by changing something on A you need to use port priority
>>
>>
>> Sent from my Verizon Wireless BlackBerry
>>
>> Regards,
>>
>> Joe Astorino - CCIE #24347
>> Sr. Technical Instructor - IPexpert
>> Mailto: jastorino_at_ipexpert.com
>> Telephone: +1.810.326.1444
>> Live Assistance, Please visit: www.ipexpert.com/chat
>> eFax: +1.810.454.0130
>>
>> IPexpert is a premier provider of Self-Study Workbooks, Video on Demand, Audio Tools, Online Hardware Rental and Classroom Training for the Cisco CCIE (R&S, Voice, Security & Service Provider) certification(s) with training locations throughout the United States, Europe, South Asia and Australia. Be sure to visit our online communities at www.ipexpert.com/communities and our public website at www.ipexpert.com
>>
>> -----Original Message-----
>> From: just kennie <justkennie_at_gmail.com>
>> Date: Wed, 21 Apr 2010 12:09:51
>> To: Cisco certification<ccielab_at_groupstudy.com>
>> Subject: Root port
>>
>> I have two switches A and B connected together through two trunks A1 ----
>> B1, and A2 ---- B2. present the root bridge is A, and all the ports are
>> forwarding. As for B, the root port is B1, and B2 in blocking. My question
>> is how do I make B2 forwaing on B. On my lab I reduced the cost of B2 on B
>> from 19 to 10, and it works. Bu on cisco site, I was told you will reduce
>> the cost of A2 on A for B2 to be the root port on B. Please assist.
>>
>>
>>
>> Idowu Kehinde
>> CCNA
>> CCNP
>> CCIP
>> CCIE (written)
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
>> _______________________________________________________________________
>> Subscription information may be found at:
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>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
>> _______________________________________________________________________
>> Subscription information may be found at:
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>>
>>
>>
>>
>>
>>
>

-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net