Etherchannel sequence

[weilliu]

Hi Experts,

I would like to know the Etherchannel sequence.

If I have 2 ports in EtherChannel, for example, port 1 and port 2.  Source and destination mac is my load balance method.  I would like to know when the first packet goes to the Etherchannel, which port that the 1^st packet will go, port 1 or port 2.

I am sure it would only go by one port for each session, and I wonder which port it would take when the first packer arrives. 

Thank you,

Aries

[chandra_rc16]

Hi Aries,

Nice question.

I just now did three experiments on this and at the three times... the first frame has passed throught the port with the lowest number.

For ex:

My first port-channel has Fa0/1 and Fa0/2 ,,, the first frame passed through Fa0/2.

My second port channel ex: There were two ports already in channel they were Fa0/14,Fa0/15... fa0/15 was first added to the channel... but the frame chose Fa0/14 for the first time.

My third ex: There were Fa0/15 and Fa0/14 channels... then after i added Fa0/1... the first frame chose Fa0/1.

Regards,
Chandu

[Furose M]

which platform is it?

its not like the first packet goes here and the 2nd packet goes there.. it calculates a hash value based on the load-balance method and based on the hash value outcome, it chooses the egress interface.

[chandra_rc16]

Hi Ali,

I've checked it on 2960 switches.

Regards,
Chandu

[Furose M]

I think we should be able to find the egress interface for a specific flow (src mac / dst mac) using this command in 3750 (i belive same applies to 2960 - havent tested).

test etherchannel load-balance interface port-channel

[chandra_rc16]

Ali,

I've tested with the load balance method of src-dst-mac.

Regards,
Chandu

[weilliu]

Hi Ali & Chandu,

I was talking about 3750 actually.  We can test it and find out which port it is going, that is no problem.  However, I am just thinking why it takes this port as first path.  I am not sure if it uses hash algorithm to do so.  I keep searching.

regards,

Aries