From: Toh Soon, Lim (tohsoon28@gmail.com)
Date: Sat Aug 25 2007 - 03:13:12 ART
Hi Andrew & Scott,
The "spanning-tree vlan root primary diameter hello-time" is actually a
macro command. After I typed "spanning-tree vlan 1-4094 root primary
diameter 2 hello-time 4", the switch adds the following lines to its config:
spanning-tree vlan 1-4094 priority 24576
spanning-tree vlan 1-4094 hello-time 4
spanning-tree vlan 1-4094 forward-time 13
spanning-tree vlan 1-4094 max-age 19
And it becomes the root bridge for all active VLANs.
Personally I prefer to use this macro command because I understand the STP
timers will be adjusted according to the formulas specified in the
802.1Dstandard.
If I connect the 4 switches in full-mesh, isn't the diameter 2? Understand
that diameter would be the number of switches connected in series from the
Root Bridge out to the end of any branch in the tree. It is measured from
the root switch outward, including the root switch.
Thank you.
B.Rgds,
Lim TS
On 8/25/07, Usankin, Andrew <Andrew.Usankin@twtelecom.com> wrote:
>
> IMHO, as you are trying to get CCIE on the lab you have to follow best
> practices of Cisco whenever it is possible.
>
> It this particular case I'd go forward and nail my root down, plus I'd
> make sure I nailed down my back up root switch also, so no unexpected
> tricks will be there.
>
> As to the changes in additional parameters as forward-delay and max-age
> - Cisco's best practice is to leave them alone :)
>
> By the way, topology of four switches has a diameter of 3, remember
> that.
>
> Andrew
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Scott Morris
> Sent: Friday, August 24, 2007 3:18 PM
> To: 'Toh Soon, Lim'; 'Cisco certification'
> Subject: RE: Which approach to change spanning-tree hello-time?
>
> If the lab doesn't specify anything about who is to be a root bridge,
> you can pick either method.
>
> As for specifying the extra parameters, if you aren't asked to, my
> advice is don't do it. No sense introducing other things that in some
> weird convoluted sense of reality may introduce extra problems in your
> topology.
>
> Do what they ask, no more, no less....
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> JNCIE #153, CISSP, et al.
> CCSI/JNCI-M/JNCI-J
> VP - Technical Training - IPexpert, Inc.
> IPexpert Sr. Technical Instructor
>
> A Cisco Learning Partner - We Accept Learning Credits!
>
> smorris@ipexpert.com
>
> Telephone: +1.810.326.1444
> Fax: +1.810.454.0130
> http://www.ipexpert.com
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Toh
> Soon, Lim
> Sent: Friday, August 24, 2007 10:17 AM
> To: Cisco certification
> Subject: Which approach to change spanning-tree hello-time?
>
> Hi Group,
>
> I have a fundamental question to seek clarification.
>
> If the task requires you to reduce the number of Config BPDUs sent to
> half
> of the default value, I'd take it to mean increasing the STP hello timer
> to
> 4 seconds.
>
> There's no indication which switch should be the root. I'd leave all
> bridge
> priority to default 32,768.
>
> How do you approach this task? I can think of two methods as follows:
>
> Method 1
> --------
> Pick any switch and configure the command:
>
> spanning-tree vlan 1-4094 root primary diameter 2 hello-time 4
>
> This has the side-effect of making this switch the root and thus start
> to
> advertise the new adjusted timers to the other switches.
>
> Method 2
> --------
> Identify the current root and only change the hello timer on it with the
> command:
>
> spanning-tree vlan 1-4094 hello-time 4
>
> Should I even adjust the forward-delay and max-age timers as well?
>
>
> Thank you.
>
> B.Rgds,
> Lim TS
>
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