Etherchannel - per-module load balancing

[kris-andrews]

Hi All,

I have a query regarding per module load balancing using a Layer 2 Etherchannel.

I have two modules in a 6509, using per module load balancing, I have one card set to source-ip hashing, and the other card using destination-ip hashing. My question is - how is traffic load balanced, is traffic balanced on ingress rather than egress?

I have an issue where i am trying to ensure traffic is sent over the same links for outbound and inbound traffic, however this doesn't appear to be working as expected.

My understanding was etherchannel loadbalancing is performed on egress, however in this scenario i'm not sure if the loadbalacing decision is made on ingress?

Does anyone have the answer to this?

Many Thanks

Kris

[Peter Paluch]

Hi Kris,

I do not know the precise answer. I have been trying to look some more information in the following article:

http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a0080094714.shtml#cat6k

but it does not seem to be of much help, neither, except for one this: it discusses the command test       etherchannel load-balance interface port-channel that can be used to discover the port through which the frame will be sent. Perhaps you could use it on your device to verify some assumptions as how is the decision going to be made.

Best regards,

Peter

[kris-andrews]

Thanks for your reply Peter,

After further investigation it seems that DFC's can change the way Etherchannel loadbalancing is performed.

So if i wish traffic to be loadbalanced on src-ip i would need to ensure that traffic arrives on a module specified for src-ip etherchannel loadbalancing for this to take affect on the egress etherchannel.

This does sound like a strange scenario but this appears to be the understanding when using DFC equipt cards.

Is anyone able to clarify this further?

Kris

[lamav]

What exactly are you trying to achieve? Why does it matter that a traffic flow use the same leg of a bundle in both directions?