From: Paul Cosgrove (paul.cosgrove@heanet.ie)
Date: Sat Aug 25 2007 - 11:31:12 ART
The following link provides an example explaining STP diameter:
http://www.cisco.com/warp/public/473/122.html
The diameter can indeed be up to 4 in a 4 switch network.
Paul.
Ash wrote:
> The diameter is calulcated not just from roots point of view but from any
> switch's vantage point in the network to the destination switch. Calculation
> includes the source and destination as well. So diameter in a 4 switch
> network would be 4 imo.
>
>
> On 8/25/07, Toh Soon, Lim <tohsoon28@gmail.com> wrote:
>
>> 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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