Forming an EtherChannel

Answered Question
Aug 11th, 2007
User Badges:

With the command :-


channel-group 1 mode { on | auto | desirable }


which combinations of the parameters on, auto, and desirable (on the respective two ports on the ends of the link) would result in the link becoming part of the etherchannel 1 ?


I am aware that if both ports on the ends of the link are set to auto then the link will NOT be added to the etherchannel 1, but I am unsure about the other combinations.


For example, if one of the ports is set to on, must the other port also be set to on ?


And would on + desirable, for example, NOT form an etherchannel ?



Correct Answer by Edison Ortiz about 9 years 8 months ago

You are missing another mode which is the (active | passive) (LACP)


PAgP etherchannel (desirable|auto)


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.


_________________________


LACP etherchannel (passive|active)


A port in the active mode can form an EtherChannel with another port that is in the active or passive mode.


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


________________


Etherchannel without negotiation (on|on)


EtherChannel on mode can be used to manually configure an EtherChannel. The on mode forces a port to join an EtherChannel without negotiations. The on mode can be useful if the remote device does not support PAgP or LACP. In the on mode, a usable EtherChannel exists only when the switches at both ends of the link are configured in the on mode.


Ports that are configured in the on mode in the same channel group must have compatible port characteristics, such as speed and duplex. Ports that are not compatible are suspended, even though they are configured in the on mode.



  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 3.7 (4 ratings)
Loading.
glen.grant Sat, 08/11/2007 - 08:16
User Badges:
  • Purple, 4500 points or more

You can use desirable on both ends or use desirable on one end and auto on the other.

rossua994 Sat, 08/11/2007 - 08:32
User Badges:

What if you had one port set to on, and the other to desirable, would this form an etherchannel ?



mohammedmahmoud Sat, 08/11/2007 - 09:31
User Badges:
  • Green, 3000 points or more

Hi,


No, "On" disables the negotiation entirely (the other side won't be able to negotiate), thus you must have both side ON, or at least one side desirable and the other can be auto or desirable.


Auto just listens for PAgP and never tries to initiate an EtherChannel negotiation, and thats why you can't have both sides as Auto.


HTH,

Mohammed Mahmoud.

Correct Answer
Edison Ortiz Sat, 08/11/2007 - 11:27
User Badges:
  • Super Bronze, 10000 points or more
  • Hall of Fame,

    Founding Member

You are missing another mode which is the (active | passive) (LACP)


PAgP etherchannel (desirable|auto)


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.


_________________________


LACP etherchannel (passive|active)


A port in the active mode can form an EtherChannel with another port that is in the active or passive mode.


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


________________


Etherchannel without negotiation (on|on)


EtherChannel on mode can be used to manually configure an EtherChannel. The on mode forces a port to join an EtherChannel without negotiations. The on mode can be useful if the remote device does not support PAgP or LACP. In the on mode, a usable EtherChannel exists only when the switches at both ends of the link are configured in the on mode.


Ports that are configured in the on mode in the same channel group must have compatible port characteristics, such as speed and duplex. Ports that are not compatible are suspended, even though they are configured in the on mode.



Actions

This Discussion