Re: Spanning-tree detected flag

Thank You joe and its very helpful

Regards
Anantha Subramanian Natarajan

On Wed, Sep 2, 2009 at 4:04 PM, Joe Astorino <jastorino_at_ipexpert.com> wrote:

> That seems to be correct!
>
>
> On Wed, Sep 2, 2009 at 3:43 PM, Anantha Subramanian Natarajan <
> anantha.natarajan_at_gravitant.com> wrote:
>
>> Joe,
>>
>> Awesome and thank you very much.So just to confirm,the TC Deducted flag
>> is not sent on the BPDU frame right ?
>>
>> Once again thanks
>>
>> Regards
>> Anantha Subramanian Natarajan
>>
>> On Wed, Sep 2, 2009 at 11:25 AM, Joe Astorino <jastorino_at_ipexpert.com>wrote:
>>
>>> Check out the following link:
>>> http://www.freepatentsonline.com/EP1330078.html
>>>
>>> "More specifically, upon detection of a change in the Spanning Tree,
>>> switches transmit Topology Change Notification Protocol Data Unit (TCN-PDU)
>>> frames toward the root. The TCN-PDU is propagated hop-by-hop until it
>>> reaches the root which confirms receipt of the TCN-PDU by setting a Topology
>>> Change Flag; additionally a TC flag can be set in BPDUs subsequently
>>> transmitted by the root for a period of time. Other switches, receiving
>>> these BPDUs, note that the Topology Change Flag has been set, thereby
>>> alerting them to the change in the active topology."
>>>
>>> The way I read that is when a change happens, the TCN is sent up to the
>>> root bridge. When the root bridge receives the TCN it acknowledges it by
>>> setting the Topology Change Flag. When other bridges receive these frames,
>>> they set their TC detected.
>>>
>>> On Wed, Sep 2, 2009 at 11:58 AM, Anantha Subramanian Natarajan <
>>> anantha.natarajan_at_gravitant.com> wrote:
>>>
>>>> Hi All,
>>>>
>>>> When I was going through the "show spanning-tree active detail "
>>>> command
>>>> ,I noticed about the detected flag as pasted below (output truncated)
>>>>
>>>> VLAN0001 is executing the ieee compatible Spanning Tree protocol
>>>> Bridge Identifier has priority 24576, sysid 1, address 0015.2b2c.f680
>>>> Configured hello time 2, max age 20, forward delay 15
>>>> We are the root of the spanning tree
>>>> Topology change flag not set, *detected flag not set*
>>>> **
>>>> I was trying to understand,whether the detected flag is a seperate flag
>>>> in
>>>> 801.2d BPDU frame format or it just the switch sets for his purpose to
>>>> understand that the TC notification has received from another switch
>>>> with TC
>>>> flag set.
>>>>
>>>> The way in which I understand the spanning-tree flags are
>>>>
>>>> 1) Its 1 byte in length
>>>> 2) Only 2 bits are used for the flag
>>>> 3) If the lower order bit is set (00000001),then its TC flag is set or
>>>> if
>>>> the high order bit is set (10000000),then it is TCA flag set.
>>>>
>>>> For some reason I couldn't understand the detected flag,Kindly help me
>>>> to
>>>> understand the same.I am sure missing some basic.
>>>>
>>>> Thanks for the help
>>>>
>>>> Regards
>>>> Anantha Subramanian Natarajan
>>>>
>>>>
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>>>>
>>>
>>>
>>> --
>>> Regards,
>>>
>>> Joe Astorino - CCIE #24347 R&S
>>> Technical Instructor - IPexpert, Inc.
>>> Cell: +1.586.212.6107
>>> Fax: +1.810.454.0130
>>> Mailto: jastorino_at_ipexpert.com
>>>
>>
>>
>
>
> --
> Regards,
>
> Joe Astorino - CCIE #24347 R&S
> Technical Instructor - IPexpert, Inc.
> Cell: +1.586.212.6107
> Fax: +1.810.454.0130
> Mailto: jastorino_at_ipexpert.com

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Received on Wed Sep 02 2009 - 16:23:39 ART