Re: Root bridge

Hi Masroor,

The Bridge ID is 1 less than the lowest MAC address on ethernet interfaces
on the switch (you would find this by sh int | inc Ethernet|bia and the
looking for the lowest value)

However
http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00801c9b4e.shtml#l2_macindicates
that you cant change the MAC address on a 3550 and it doesn't
appear to be supported on the 3560 (however other platforms can support this
capability)

In terms of the CCIE lab, option 2 appears to be the only real option unless
you want to play around with things like spanningtree guard root on
interfaces facing other switches but that may not be such a great idea...

Cheers,
Adam

On Thu, Sep 23, 2010 at 4:22 PM, masroor ali <masror.ali_at_gmail.com> wrote:

> I thought we cant change the MAC address of switch, I also tried to find
> out the command to change the MAC in 3550/3560 switches. can you please help
> me out???
>
>
> On Thu, Sep 23, 2010 at 11:18 AM, Adam Booth <adam.booth_at_gmail.com> wrote:
>
>> Hi Masroor,
>>
>> Chris gave you two potential answers, why aren't they acceptable?
>>
>> Just to recap what they are
>>
>> 1) Changing the bridge id of the switch you want to be root to have the
>> lowest MAC Address
>> 2) Increasing the priority on the other switches from the default 32768 to
>> a higher value, so the unchanged switch will become root due to having the
>> lowest priority
>>
>> Cheers,
>> Adam
>>
>>
>> On Thu, Sep 23, 2010 at 4:10 PM, masroor ali <masror.ali_at_gmail.com>wrote:
>>
>>> see i have a question in a document asking to make a root bridge without
>>> changing priority, there must be a solution of this question..
>>>
>>> On Thu, Sep 23, 2010 at 12:59 AM, Chris Grammer <cgrammer_at_essilorusa.com
>>> >wrote:
>>>
>>> > Change the MAC to 0000.0000.0001 on the switch you want to be root?
>>> > Change the switch priority on all the other switches to be higher than
>>> the
>>> > switch that you want to be root.
>>> >
>>> > The bridge with the lowest Bridge ID wins.
>>> >
>>> > *Select a root bridge.* The *root bridge* of the spanning tree is the
>>> > bridge
>>> > with the smallest (lowest) bridge ID. Each bridge has a unique
>>> identifier
>>> > (ID) and a configurable priority number; the bridge ID contains both
>>> > numbers. To compare two bridge IDs, the priority is compared first. If
>>> two
>>> > bridges have equal priority, then the MAC addresses are compared. For
>>> > example, if switches A (MAC=0200.0000.1111) and B (MAC=0200.0000.2222)
>>> both
>>> > have a priority of 10, then switch A will be selected as the root
>>> bridge.
>>> >
>>> > http://en.wikipedia.org/wiki/Spanning_tree_protocol
>>> >
>>> >
>>> > <http://en.wikipedia.org/wiki/Spanning_tree_protocol>Chris
>>> >
>>> >
>>> > On Wed, Sep 22, 2010 at 11:45 AM, masroor ali <masror.ali_at_gmail.com>
>>> > wrote:
>>> >
>>> > > hi,
>>> > >
>>> > > is their any way to make a root switch without changing switch
>>> > priority???
>>> > >
>>> > > --
>>> > > Regards,
>>> > > Masroor Ali
>>> > > P Please don't print this e-mail unless you really need to.
>>> > >
>>> > >
>>> > > Blogs and organic groups at http://www.ccie.net
>>> > >
>>> > >
>>> _______________________________________________________________________
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>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>>
>>>
>>> --
>>> Regards,
>>> Masroor Ali
>>> P Please don't print this e-mail unless you really need to.
>>>
>>>
>>> Blogs and organic groups at http://www.ccie.net
>>>
>>> _______________________________________________________________________
>>> Subscription information may be found at:
>>> http://www.groupstudy.com/list/CCIELab.html
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>
>
> --
> Regards,
> Masroor Ali
> P Please don't print this e-mail unless you really need to.

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Received on Thu Sep 23 2010 - 16:39:08 ART