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SWITCHING LOOPS QUESTIONS

manuelricardo
Level 1
Level 1

Hi folks ,

Iam wondering what happens in an enviroment whereby we have a switching loop ?? does the network goes down ? what is the effect of the looping in a switched environment , does it affect other services as well ? do the ports enter into errdisable state or any other special effect state ? and last but not least how can i recover a production network from a switching loop ? please tell me the long and quick way to accomplish this ?

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The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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Posting

Can you apply the BPDUguard globally on a switch or on interface basis ?

Often, either.

whats the difference between the BPDU guard and BPDU filter ?

Guard err-disables the port if a BPDU is seen.  Filter just blocks them from transit.

How do you tell?  Well, if the network goes into "meltdown" is often a good sign.

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4 Replies 4

Joseph W. Doherty
Hall of Fame
Hall of Fame

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

L2 loops often create such busy links (from the looping traffic), effectively your network becomes unusable.

Generally all network services dealing with a L2 loop become unusable.

Generally ports do not enter a special state once a loop forms.  (However, depending on device features L2 loops might be prevented by the device detecting the possible forming of a L2 loop and perhaps error disabling the port.  [E.g. BPDUGuard])

You fix it by breaking the loop.  Might be accomplished by shutting ports, if you can still manage the devices, or by physically disconnecting links.

Hi joseph ,

Can you apply the BPDUguard globally on a switch or on interface basis ?whats the difference between the BPDU guard and BPDU filter ?

and the other thing , how can I as network administrator notice or conclude that there is a switching loop occuring on the network , the problem might be associated with other factors , how do i come into conclusion that there is a actually a looping problem on my network .


Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Can you apply the BPDUguard globally on a switch or on interface basis ?

Often, either.

whats the difference between the BPDU guard and BPDU filter ?

Guard err-disables the port if a BPDU is seen.  Filter just blocks them from transit.

How do you tell?  Well, if the network goes into "meltdown" is often a good sign.

Hi Joseph thank you for you kind replies iam now clear on this subject . Cheers and thanks for the Help !!!

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