From: Sean C. (Upp_and_Upp@hotmail.com)
Date: Fri Sep 01 2006 - 02:21:02 ART
HI Victor,
Wow, great post!! But, now I'm more confused then ever! :-)
Perhaps Brian's Sw2 config also had the forwarding delay altered but it just
wasn't mentioned. So..., somewhere between points 2 and 3 (let's call it
point 2.5)said:
2-SW2 is the root.
2.5-SW2's forwarding delay is configured as 4 seconds for VLAN 100.
3-SW1's forwarding delay is configured as 4 seconds for VLAN 100.
This cuts back to the 2nd part of the original email Aamir (remember way back
when):
--do we need to issue this command on both the switches or only on where the
Vlan X exists
So..., what happens if, taking your scenario, while SW1 is still the root of
Vlan X, if SW1 doesn't have any physical interfaces assigned to Vlan X, can
the forward-delay just be altered on the SW2?
Curious for input (and thanks again for the great post),
Sean
----- Original Message -----
From: Victor Cappuccio
To: 'Sean C.' ; 'sabrina pittarel'
Cc: 'GroupStudy'
Sent: Thursday, August 31, 2006 7:02 PM
Subject: RE: Forward-delay time
Hi Sean
Sorry, I'm jumping back a thread here.
But I like more than words, the debugs output
Using this topology
Sw1 ---- Trunk ---- Sw2 --- f0/11 --- Linux box
I have the following
Rack3Sw1(config)#do show spanning-tree vlan 1
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 8193
Address 000b.5f55.f800
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 8193 (priority 8192 sys-id-ext 1)
Address 000b.5f55.f800
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 600
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- --------
--------------------------------
Fa0/15 Desg FWD 19 128.15 P2p
If I sniff at the Linux Box for packet received
I'm getting this
21:53:41.585364 802.1d config 2001.00:0e:84:d0:d3:80.800b root
2001.00:0b:5f:55:f8:00 pathcost 19 age 1 max 20 hello 2 fdelay 15
As you can see the FDelay is 15
If I change the timer at Sw1
Rack3Sw1(config)#spanning-tree vlan 1 forward-time 4
Rack3Sw1(config)#do show spanning-tree vlan 1 | in Dela
Hello Time 2 sec Max Age 20 sec Forward Delay 4
sec
Hello Time 2 sec Max Age 20 sec Forward Delay 4 sec
I'm receiving this at the Linux Box
21:54:49.588715 802.1d config 2001.00:0e:84:d0:d3:80.800b root
2001.00:0b:5f:55:f8:00 pathcost 19 age 1 max 20 hello 2 fdelay 4
So as you can see the Root is in charge of sending BPDUs
If I Change the FDelay at Sw2
Rack3Sw2(config)#spanning-tree vlan 1 forward-time 5
Rack3Sw2(config)#do show spanning-tree vlan 1 | in Dela
Hello Time 2 sec Max Age 20 sec Forward Delay 4 sec
Hello Time 2 sec Max Age 20 sec Forward Delay 5 sec
The host is still receiving this
22:00:21.606372 802.1d config 2001.00:0e:84:d0:d3:80.800b root
2001.00:0b:5f:55:f8:00 pathcost 19 age 1 max 20 hello 2 fdelay 4
HTH for something
Victor.-
-----Mensaje original-----
De: nobody@groupstudy.com [mailto:nobody@groupstudy.com] En nombre de Sean
C.
Enviado el: Viernes, 01 de Septiembre de 2006 12:31 a.m.
Para: sabrina pittarel
CC: GroupStudy
Asunto: Re: Forward-delay time
Hi Sabrina,
Sorry to bring up an email from yesterday, but I'm still trying to wrap my
head around a comment of yours: 'THE STP TIMERS MUST BE CHANGED ON THE ROOT
BRIDGE FOR THE VLAN AND ONLY THERE!'
If you still have the email, refer to the excellent email that Brian sent.
If I'm understanding Brian's post, while Sw2 is the root bridge, he is
changing the forwarding delay on Switch 1 only:
Curious for anyone thoughts,
Sean
1-In the below example SW1 and SW2 have two trunk links, Fa0/13 (the root
port) and Fa0/14.
2-SW2 is the root.
3-SW1's forwarding delay is configured as 4 seconds for VLAN 100.
4-Fa0/13 is shut down on SW2 and Fa0/14 transitions to forwarding on SW1 in
8 seconds. Note that max-age does not apply:
SW1#show spanning-tree vlan 100
VLAN0100
Spanning tree enabled protocol ieee
Root ID Priority 32868
Address 000f.8fb2.e800
Cost 19
Port 13 (FastEthernet0/13)
Hello Time 2 sec Max Age 20 sec Forward Delay 4 sec
Bridge ID Priority 32868 (priority 32768 sys-id-ext 100)
Address 000f.8fe0.3500
Hello Time 2 sec Max Age 20 sec Forward Delay 4 sec
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- --------
-------------------------------
Fa0/13 Root FWD 19 128.13 P2p
Fa0/14 Altn BLK 19 128.14 P2p
SW1#
04:57:14: STP: VLAN0100 new root port Fa0/14, cost 19
04:57:14: STP: VLAN0100 Fa0/14 -> listening
!
! AT 14 SECONDS AFTER THE FAILURE IS DETECTED AND FA0/14 GOES INTO
LISTENING
!
04:57:15: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/13,
changed state to down
04:57:16: STP: VLAN0100 sent Topology Change Notice on Fa0/14
04:57:16: %LINK-3-UPDOWN: Interface FastEthernet0/13, changed state to down
04:57:18: STP: VLAN0100 Fa0/14 -> learning
!
! 4 SECONDS LATER LISTENING EXPIRES AND LEARNING BEGINS
!
04:57:22: STP: VLAN0100 Fa0/14 -> forwarding
!
! 4 SECONDS LATER LEARNING EXPIRES AND FORWARDING BEGINS
!
If max-age were taken into account here the convergence would take 28
seconds (max-age + listening + learning) when in reality is takes just 8
seconds (listening + learning)
SW1#show spanning-tree vlan 100
VLAN0100
Spanning tree enabled protocol ieee
Root ID Priority 32868
Address 000f.8fb2.e800
Cost 19
Port 14 (FastEthernet0/14)
Hello Time 2 sec Max Age 20 sec Forward Delay 4 sec
Bridge ID Priority 32868 (priority 32768 sys-id-ext 100)
Address 000f.8fe0.3500
Hello Time 2 sec Max Age 20 sec Forward Delay 4 sec
Aging Time 4
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- --------
-------------------------------
Fa0/14 Root FWD 19 128.14 P2p
----- Original Message -----
From: "sabrina pittarel" <sabri_esame@yahoo.com>
To: "Sean C" <tecmochamp@hotmail.com>; <swm@emanon.com>; "ROCHA Leandro
ORANGE-FT" <leandro.rocha@orange-ft.com>; "Aamir Aziz"
<aamiraz77@gmail.com>
Cc: "GroupStudy" <ccielab@groupstudy.com>
Sent: Wednesday, August 30, 2006 9:18 PM
Subject: Re: Forward-delay time
Hi,
a word of wisdom the kind proctor shared with me on my failed attempt and
that I'm going to share with you now:
"in the CCIE lab you do what you are asked, not what makes sense".
About where to change the STP timers.
THE STP TIMERS MUST BE CHANGED ON THE ROOT BRIDGE FOR THE VLAN AND ONLY
THERE!
Sabrina
----- Original Message ----
From: Sean C <tecmochamp@hotmail.com>
To: swm@emanon.com; ROCHA Leandro ORANGE-FT <leandro.rocha@orange-ft.com>;
Aamir Aziz <aamiraz77@gmail.com>
Cc: GroupStudy <ccielab@groupstudy.com>
Sent: Wednesday, August 30, 2006 12:36:49 PM
Subject: Re: Forward-delay time
Sorry, I'm jumping back a thread here.
Scott - concerning your comment "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."
Perhaps that is why you have four CCIE's and I'm beyond my fourth attempt
at
my first CCIE. I'd be looking at the scenario in the regards of - assuming
that the vlan is on all the switches (possibly via VTP), even if no
physical
interface is assigned the vlan in question, that the lab would be wanting
you to apply the statement to all switches that have that vlan in their
vlan
database. But, I can certainly understand your reasoning - if only one of
the switches has a port applied to that vlan, then only change that switch.
Perhaps, the lab would be seeing if you know that you only need to apply
the
command to one switch, it's not something that has to be applied
everywhere.
Again, thanks for the re-think.
This is kind-of along the lines of that vaunted question in OSPF where the
task is to adjust the auto-cost bandwidth. For the cost to be computed the
same on every device, the config would need to be applied to every device.
But perhaps the task only is looking to see if you recognize that you need
to configure this on one device with that type of interface. <Hope that
made sense!>
Again, thanks,
Sean
----- Original Message -----
From: "Scott Morris" <swm@emanon.com>
To: "'Sean C'" <Upp_and_Upp@hotmail.com>; "'ROCHA Leandro ORANGE-FT'"
<leandro.rocha@orange-ft.com>; "'Aamir Aziz'" <aamiraz77@gmail.com>
Cc: "'GroupStudy'" <ccielab@groupstudy.com>
Sent: Wednesday, August 30, 2006 12:33 PM
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
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] 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@orange-ft.com>
> To: <ccielab@groupstudy.com>
> 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@internetworkexpert.com>
> > Sent by: nobody@groupstudy.com
> > 08/30/06 10:39 AM
> > Please respond to "Brian McGahan"
> >
> >
> > To: "Aamir Aziz" <aamiraz77@gmail.com>,
> > 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@internetworkexpert.com
> >
> > 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@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of
> > > Aamir Aziz
> > > Sent: Wednesday, August 30, 2006 6:48 AM
> > > To: ccielab@groupstudy.com
> > > 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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