LACP on 3750E switch

Unanswered Question
Jun 1st, 2010

Hi,

I am trying to configure etherchannel on 3750E switch for link redundancy. We are having 2 stacked 3750E switch connected to Nexus 2148 switch via trunk port which is further connected to Nexus 5010.

I am using 3750E as core switches. I want redundancy on 3750E so that in case one of the stack member fails, other member can pass the traffic. The problem is when I configuring lacp to acheive this I am getting %SW_MATM-4-MACFLAP_NOTIF: MAC flapping errors, which I belive due to looping.

Below is the typical layout

3750E  ------------  3750E     (Stacking)

     |                       |

NX 2148          NX 2148

     |                       |

NX 5010 -------- NX 5010     (VPC)

Could somebody suggest any solution to overcome this issue or any other method through which I can acheive the redundancy between switches?

Thanks,

Pawan

I have this problem too.
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Calin Chiorean Tue, 06/01/2010 - 05:32

From what I understand the 3750 are stacked, but NX not. I don't have experience with NX, but I think LACP is not supported as you want to configure:

Stack         Non stack

______

|C3750| ----- NX

|C3750| ----- NX

So, from 2 or multiple switches in the stack to another switch like below is working:

http://www.cisco.com/image/gif/paws/69979/cross_stack_etherchannel1.gif

Let me know if I understood wrong. In the meantime I have to check if NX support LACP in scenario multiple NX to multiple NX in one logical etherchannel.

winpwnkmr Tue, 06/01/2010 - 05:41

Can you tell me how can I configure multiple switches in the stack to another switch as you have suggested? I will try it and see if it works.

Thanks,

Pawan

Calin Chiorean Tue, 06/01/2010 - 05:46

I would try the following config to achieve redundancy:

Sorry if the drawing looks strange a little bit, but I did it quick as is more relevant than writting.

So you'll have one channel (2 ports) from 2 switches in the stack to one NX switch, and another channel (2 ports) from 2 switches in the stack to the other NX switch.

Between NXes you can have another channel L3 or L2, as you wish and the same back to the 5010.

let me know if this helps

winpwnkmr Tue, 06/01/2010 - 05:51

But don't you think it would create the loop as from 3750E both ports will be active to NX 2148?

Thanks,

Pawan

Calin Chiorean Tue, 06/01/2010 - 05:55

Think of the etherchannels like ethernet cable. If you would have there a triangle let's say from one C3750 two connection to 2 NX switches and also connection between NXes. This will create loop? No, because we have something magic called Spanning-Tree

It's the same here. You have to be careful when configuring the etherchannels to have the same settings and check STP to be proper configured and you're out of loops.

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