PAgP silent & non-silent

Unanswered Question
Aug 9th, 2009

Hi Experts,

As read in book that pagp has two modes desirable & auto .

We can use these with silent & no-silent.

As per book reference , If we use silent means ports are not waiting for pagp hello from other end & channel become up.

I did this scenario in lab with 2960 switches keeping both switches port in auto silent mode But channel is not coming up.

Please explain me , where i am wronge

Thanks in advance


  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Hitesh Vinzoda Sun, 08/09/2009 - 10:12

•A port in the desirable mode can form an EtherChannel with another port that is in the desirable or auto mode.

•A port in the auto mode can form an EtherChannel with another port in the desirable mode.

A port in the auto mode cannot form an EtherChannel with another port that is also in the auto mode because neither port starts PAgP negotiation.

If your switch is connected to a partner that is PAgP-capable, you can configure the switch port for nonsilent operation by using the non-silent keyword. If you do not specify non-silent with the auto or desirable mode, silent mode is assumed.

Use the silent mode when the switch is connected to a device that is not PAgP-capable and seldom, if ever, sends 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 port to a channel group, and to use the port for transmission.

Hope this helps


Hitesh Vinzoda

suryakant.chavan Sun, 08/09/2009 - 10:26

Hi Hitesh,

First thanks For your quick reply,

As you said & also by books , silent with desirable & auto does not expect pagp hellos from opposite side.

I configured in the same manner,that both switches ports in auto silent mode, means both switches not sending pagp hellos & also not expect pagp hellos. So they should form etherchannel. But that does not.

Please give explanation in brief.

Hitesh Vinzoda Sun, 08/09/2009 - 10:50


Use the silent keyword when you connect to a silent partner (which is a device that does not generate BPDUs or other traffic). An example of a silent partner is a traffic generator that does not transmit packets. "Use the silent keyword with auto or desirable mode". If you do not specify silent or non-silent, silent is assumed.

so when you use silent mode keep the AUTO and DESIRABLE under consideration.

i.e. AUTO >> AUTO does not forms etherchannel


Hitesh Vinzoda


This Discussion