RE: Spanning Tree Question

From: Mark Stephanus Chandra (mark.chandra@gmail.com)
Date: Fri Aug 22 2008 - 00:30:29 ART

Hi Daniel,

 

Thanks a lot for the explanation, so in other words, we use port-priority
when we configure in root bridge swith. Port-priority is for election of
designated port right ? So if we configure in no root bridge switch, it
doesn't have effect right ?

 

We configure path cost for election of non root bridge switch, right ?

 

Regards

 

Mark Stephanus Chandra

 

 

From: Daniel Valle [mailto:danielfrvalle@gmail.com]
Sent: Friday, August 22, 2008 1:32 AM
To: Mark Stephanus Chandra
Cc: ccielab@groupstudy.com
Subject: Re: Spanning Tree Question

 

Mark,

 

Cost we use in the incoming switch, for example.. if SW1 is the root, the
Cost must be applied in SW2, otherwise it'll not any effect ( this is
similar to IGP metrics. the metric that matters is always the inbound
interface)

 

port priority is to be configured in the designated port. i.e, in your case,
you should configure port priority in SW1 ( which is the root)

 

if you have a 3rd switch SW1==SW2==SW3, you must use port-priority in the
SW2 port to influence SW3 decision.

 

resuming: use Port-priority in designated ports and use port-cost in root or
alternative(blocked) ports

 

 

HTH,

 

Daniel

 

On 8/21/08, Mark Stephanus Chandra <mark.chandra@gmail.com> wrote:

Dear All Expert,

I'm kinda confuse with the used of SPT port-priority and SPT path cost.

Actually when I do my IEWB vol 2 lab 11.

To influence path decision, when doing SPT.

SW1 --------------- SW2

SW1 is the root bridge

Actually SW 1 have three trunk connection to SW2, let say FA0/15,fa0/14 and
fa0/13

so the command is, SW1 should use Fa0/15 as its primary link to SW2, when
fa0/15 fail, then it choose fa0/13 and the last is fa0/14.

So, if I configure fa0/15 with spt cost 1 , do i have the same result if i
configure fa0/15 with spt port-priority of let say 15 (the default is 128
right ?)

So kinda confuse when do we have to use spt priority or cost

Thanks in advance 

--
Mark Stephanus Chandra

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