Etherchannel - 3750 Stack

Unanswered Question
Apr 7th, 2012
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Hi friends,


I attached the topology to better understanding.


Follow the scenario:


- I have two 3750 in stack, and two 3560;

- I configured the etherchannel in all devices:


3750 stack:


3750(config)#interface portchannel 1

3750(config-if)#switchport trunk encapsulation dot1q


3750(config)#interface range gigabitethernet 1/0/0-1/0/1

3750(config-if)#channel-group 1 mode on

3750(config-if)#switchport trunk encapsulation dot1q

3750(config-if)#switchport mode trunk


3750(config)#interface range gigabitethernet 2/0/0-2/0/1

3750(config-if)#channel-group 1 mode on

3750(config-if)#switchport trunk encapsulation dot1q

3750(config-if)#switchport mode trunk


two 3560 :


3560(config)#interface portchannel 1

3560(config-if)#switchport trunk encapsulation dot1q


3560(config)#interface range gigabitethernet 0/0-/0/1

3560(config-if)#channel-group 1 mode on

3560(config-if)#switchport trunk encapsulation dot1q

3560(config-if)#switchport mode trunk



After configured, works about 3 minutes, and the ports on the 3750 stack are disabled . What could be, the IOS version?

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glen.grant Sat, 04/07/2012 - 21:10
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  Why do you have 4 ports configured on the 3750 and only 2 on the 3560's.?  Check the logs it will tell you a lot of the time why the channel was taken down.

Leo Laohoo Sun, 04/08/2012 - 01:38
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Do a "sh log" and it will tell you WHY the channel went down.


Looking at your post above your etherchannel config is tupsy-turvey.  Put the physical interface into the channel-group FIRST. 

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