PAgP silent and non-silent

Unanswered Question
May 5th, 2010

I am not sure if I am getting this matter of PAgP silent and non-silent right. I've been reading some other pages and is still not clear.

What I understand:

1) When you have a switch and you know you will have a non PAgP device in the far end then you configure the switch as silent (which is the default). You do that because as silent it will wait for PAgP packets but since it wont get them because the far end is a non PAgP device then it will bring the Etherchannel up despite it doesn't hear PAgP packets. So, in silent the switch will bring the Etherchannel up.

2) When you have a switch and you will connect it to a far end switch (a PAgP capable device), then you should configure them as non-silent just because you know they will send PAgP packets trying to negotiate. Of course it will still respect the auto-desirable, desirable-desirable, auto-auto rules.

So, you basically configure silent or non-silent based on your knowledge of what is in the far end. So as a switch you would think "well I am a switch and I know the other device won't negotiate because is not a PAgP capable device, so I'll be in silent so I can bring the etherchannel up even though I wont get PAgP packets to negotiate". Or you can think "I am a switch and the other device is  PAgP capable, so I will be in non-silent so I can exchange PAgP packets to negotiate to bring the Etherchannel Up or not".... is this right?

Is my understanding correct? It's hard to understand this subject. Please help!

I have this problem too.
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Reza Sharifi Wed, 05/05/2010 - 19:01

Hi,

Yes, you definition is correct.  You usually run silent with devices that do not ever run PAGP i.e. servers, and run none-silent with devices that support PAGP.  By default if you don't specify non-silent with auto or desirable then silent mode is used.

HTH

Reza

Ganesh Hariharan Wed, 05/05/2010 - 23:40

I am not sure if I am getting this matter of PAgP silent and non-silent right. I've been reading some other pages and is still not clear.

What I understand:

1) When you have a switch and you know you will have a non PAgP device in the far end then you configure the switch as silent (which is the default). You do that because as silent it will wait for PAgP packets but since it wont get them because the far end is a non PAgP device then it will bring the Etherchannel up despite it doesn't hear PAgP packets. So, in silent the switch will bring the Etherchannel up.

2) When you have a switch and you will connect it to a far end switch (a PAgP capable device), then you should configure them as non-silent just because you know they will send PAgP packets trying to negotiate. Of course it will still respect the auto-desirable, desirable-desirable, auto-auto rules.

So, you basically configure silent or non-silent based on your knowledge of what is in the far end. So as a switch you would think "well I am a switch and I know the other device won't negotiate because is not a PAgP capable device, so I'll be in silent so I can bring the etherchannel up even though I wont get PAgP packets to negotiate". Or you can think "I am a switch and the other device is  PAgP capable, so I will be in non-silent so I can exchange PAgP packets to negotiate to bring the Etherchannel Up or not".... is this right?

Is my understanding correct? It's hard to understand this subject. Please help!

Hi,

Cisco states that non-silent mode is used to connect your switch to an adjacent device that is not PAgP capable.  They give the following example:

"non-silent -Keyword that is used with the auto or desirable mode when traffic is expected from the other device.-


The silent mode is used when the switch is connected to a device that is not PAgP-capable and seldom, if ever, transmits packets. An example of a silent partner is a file server or a packet analyzer that is not generating traffic. In this case, running PAgP on a physical port connected to a silent
partner prevents that switch port from ever becoming operational; however, the silent setting allows PAgP to operate, to attach the interface to a
channel group, and to use the interface for transmission."

Hope to Help !!

Ganesh.H

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Ahmed Muhi Sun, 10/23/2011 - 02:54

This does not have anything to do with the negotiation of PAgP it is has to do with the fact that the link is being used to send data or not.

the following link to CCNP Practical Studies Switching will clarify it more:

http://books.google.com/books?id=TFdo0H8OKVMC&pg=PA222&lpg=PA222&dq=pagp+silent&source=bl&ots=_sGElQzoIL&sig=8YsuxuQtjmdjE6DohjPtnbYSJtI&hl=en&ei=pdijTpy_Ns3FtAbuw9mUAw&sa=X&oi=book_result&ct=result&resnum=7&ved=0CGYQ6AEwBg#v=onepage&q=pagp%20silent&f=false

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