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RE: Forward-delay time posted 08/30/2006
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for example, if we have two trunk ports between the switches, and one 
trunk port is in blocking, woudnt it consider the max-age to go out of 
blocking state for this vlan?

Leandro






"Brian McGahan" <bmcgahan@xxxxxxxxxxxxxxxxxxxxxx>
08/30/06 03:01 PM

 
        To:     ROCHA Leandro ORANGE-FT <leandro.rocha@xxxxxxxxxxxxx>, 
<ccielab@xxxxxxxxxxxxxx>
        cc: 
        bcc: 
        Subject:        RE: Forward-delay time



Leandro,

What is your reasoning behind max-age coming into play?

Brian McGahan, CCIE #8593
bmcgahan@xxxxxxxxxxxxxxxxxxxxxx

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> -----Original Message-----
> From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf
Of
> ROCHA Leandro ORANGE-FT
> Sent: Wednesday, August 30, 2006 12:13 PM
> To: ccielab@xxxxxxxxxxxxxx
> Subject: RE: Forward-delay time
>
> I see. This question is a little different the one I was thinking
about.
>
> I previously saw some similar question who explicitly said:  "The
entire
> time from blocking to forward should be less than 16 secs for ports on
> vlan X. Config the switches to accomplish this without jumping any
state"
>
> This question avoids using portfast (don't skipping states), leading
you
> to have to tune max-age and fwd-delay to minimum. Is there any other
> solution?
>
> Leandro
>
>
>
>
>
> "Scott Morris" <swm@xxxxxxxxxx>
> Sent by: nobody@xxxxxxxxxxxxxx
> 08/30/06 01:33 PM
> Please respond to "Scott Morris"
>
>
>         To:     "'Sean C'" <Upp_and_Upp@xxxxxxxxxxx>, ROCHA Leandro
> ORANGE-FT
> <leandro.rocha@xxxxxxxxxxxxx>, "'Aamir  Aziz'" <aamiraz77@xxxxxxxxx>
>         cc:     "'GroupStudy'" <ccielab@xxxxxxxxxxxxxx>
>         bcc:
>         Subject:        RE: Forward-delay time
>
>
>
> While technically your thinking is correct and a good idea in REAL
LIFE
> network design, in the CCIE lab you are often presented with scenarios
> that
> logically would not play in real life.
>
> Don't over-think things!  With a two-switch ethernet network, there
really
> isn't any magical difference that setting the max-age timer is going
to
> play!  Watch your "show spanning-tree" information to see what the
> switches
> do.
>
> Although the lab scenario may ask you to specifically change one
piece,
> don't automatically assume you have to recalculate everything else!
If
> you
> aren't asked to, don't do it.
>
> If the scenario asked you to keep all of the 802.1D ratios, yet still
make
> convergence time faster with those specifics, THEN perhaps you'll
think
> down
> this path!
>
> Believe me, this is a path that many people take because of real-world
> expectations that we have and knowledge of the actual
> application/implication of changing things like this.  But in a lab
> environment, particularly with the limited pieces of equipment that we
> have,
> you should ask yourself whether it will make a difference, or not work
> properly otherwise.
>
> HTH,
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
JNCIE
> #153, CISSP, et al.
> CCSI/JNCI-M/JNCI-J
> IPExpert VP - Curriculum Development
> IPExpert Sr. Technical Instructor
> smorris@xxxxxxxxxxxx
> http://www.ipexpert.com
>
>
>
> -----Original Message-----
> From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf
Of
> Sean
> C
> Sent: Wednesday, August 30, 2006 11:49 AM
> To: ROCHA Leandro ORANGE-FT; Aamir Aziz
> Cc: GroupStudy
> Subject: Re: Forward-delay time
>
> Hi Leandro,
>
> If the task was asking to go from blocking to forwarding state in
under 16
> secs, wouldn't that be when you would take into consideration the
max-age
> timer?
>
> This task specifically states to alter the forward-delay time only,
> nothing
> about altering the entire STP equation - "Configure the forward-delay
time
> of a Vlan X under 16 seconds."  Taking the task into consideration, I
> would
> just alter the forward-time to a value of 7.
>
> I understand what you're trying to do, I'm just not sure that your
answer
> would meet the requirements of this task.
>
> Also, Aamir - to answer the 2nd part of your original post - "do we
need
> to
> issue this command on both the switches or only on where the Vlan X
> exists."
> - while, technically, you would only need to apply it to a switch
where
> the
> vlan exists - personally - as long as the vlan in question is able to
be
> on
> the 2nd switch (no vlan pruning, or the switch w/out the vlan is a VTP
> transparent switch, etc...), I would apply the timer to both switches.
> Or, if I was really questioning it, I would ask the proctor something
> along
> the lines of "Should I take into consideration the chances of that
vlan
> being used on the 2nd switch in the future?...."
>
> HTH,
> Sean
>
> ----- Original Message -----
> From: "ROCHA Leandro ORANGE-FT" <leandro.rocha@xxxxxxxxxxxxx>
> To: <ccielab@xxxxxxxxxxxxxx>
> Sent: Wednesday, August 30, 2006 10:05 AM
> Subject: RE: Forward-delay time
>
>
> > I think we have to take in account the max-age timer too.
> >
> > To have less than 16 seconds in any case, we should put max-age to 6
and
> > fwd-delay to 4 (the minimum values).
> >
> > Then we have a total of 6+4+4=14.
> >
> > Leandro
> >
> >
> >
> >
> >
> > "Brian McGahan" <bmcgahan@xxxxxxxxxxxxxxxxxxxxxx>
> > Sent by: nobody@xxxxxxxxxxxxxx
> > 08/30/06 10:39 AM
> > Please respond to "Brian McGahan"
> >
> >
> >         To:     "Aamir Aziz" <aamiraz77@xxxxxxxxx>,
> <ccielab@xxxxxxxxxxxxxx>
> >         cc:
> >         bcc:
> >         Subject:        RE: Forward-delay time
> >
> >
> >
> > The forward-delay command configures each of the listening and
> > learning phase timers.  This means that if you have it configured as
15
> > that it will take 30 seconds to go through both phases.  If you want
to
> > move from blocking to forwarding in less than 16 seconds your
forward
> > delay would have to be 8 or lower.
> >
> > Brian McGahan, CCIE #8593
> > bmcgahan@xxxxxxxxxxxxxxxxxxxxxx
> >
> > Internetwork Expert, Inc.
> > http://www.InternetworkExpert.com
> > Toll Free: 877-224-8987 x 705
> > Outside US: 775-826-4344 x 705
> > 24/7 Support: http://forum.internetworkexpert.com
> > Live Chat: http://www.internetworkexpert.com/chat/
> >
> >
> > > -----Original Message-----
> > > From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On
Behalf
> > Of
> > > Aamir Aziz
> > > Sent: Wednesday, August 30, 2006 6:48 AM
> > > To: ccielab@xxxxxxxxxxxxxx
> > > Subject: Forward-delay time
> > >
> > > Hi there,
> > >
> > > If the task says Configure the forward-delay time of a Vlan X
under 16
> > > second then what value do we use 15 or 16?
> > >
> > > #spanning-tree VLAN X forward-time 15 or 16
> > >
> > > since by default it is 15, and do we need to issue this command on
> > both
> > > the
> > > switches or only on where the Vlan X exists.
> > >
> > > Thanks
> > > Aamir
> > >
> > >
> >
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