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Beginner

Impacts of load-balancing in etherchannel chaining

Hello,

 

I have for example a LAN with several switches (SW1-4) connected together with Etherchannel, an ESX is connected to the SW1 with Etherchannel too, and an other server connected to SW4.

 

ESX====SW1====SW2====SW3====SW4====SRV

                  |

                  |_ ___PC

 

My ESX need to have a load balancing method like src-dst-ip. That's not a problem, I change it in SW1.

Then :

- Because there is an other etherchannel between SW1 and SW2 and because the load-balancing command affect every etherchannel in the switch, I will change the load balancing method of the SW2 to be agree with SW1 because default is src-mac.

- I'm doing the same for SW3 and SW4.

 

Everything will be good if my server have a src-dst-ip load balancing configured.

 

My question : If my server is still in src-mac for example or everything else than src-dst-ip, what's could be the solution to be clean and satisfied both ESX and Server load balancing methods ? without changing servers load balancing methods.

 

I don't think that's possible because of the switches load balancing process...

 

Thanks for your responses,

1 ACCEPTED SOLUTION

Accepted Solutions
VIP Expert

Re: Impacts of load-balancing in etherchannel chaining

Sorry, it's still not clear to me why the concern.

Yes, LB is global, but unclear why that's a problem. I could understand the rare corner case, but your case doesn't appear to be one.

On switches, LB only applies to egress traffic from the switch. It doesn't matter how the traffic entered the switch.

src-dst-ip is often a good LB choice (except when heavy flows between the same two hosts (for that, some Cisco switch will also include port numbers in the hash).

If your one SRV only offers mac-src, assuming there's only one MAC, all traffic from it would just use the same link. Once it gets to the first switch, its LB choice can redistribute traffic across multiple links.
4 REPLIES 4
VIP Expert

Re: Impacts of load-balancing in etherchannel chaining

Not 100% sure I understand your question.

If you're asking what you might do on the ESX server if it doesn't support Etherchannel load balancing like the switches, that would depend on the capabilities of the ESX server. If it doesn't offer link load balancing like the switches, one option might be to use higher bandwidth links (if possible) between the ESX server and SW1.
Beginner

Re: Impacts of load-balancing in etherchannel chaining

My question is without any change on my ESX and my SRV (this is an exemple of topology, not my topology) :

- How can I be clean with my load balancing parameter on my switches ?

 

for exemple :

Etherchannel LB on ESX is : src-dst-ip

Etherchannel LB SRV is : mac-src

which LB parameter I need to put in my switches ?

The problem is that the LB parameter is a global command and not an interface command. But there is maybi a work around.

 

thanks for your answer,

regards

VIP Expert

Re: Impacts of load-balancing in etherchannel chaining

Sorry, it's still not clear to me why the concern.

Yes, LB is global, but unclear why that's a problem. I could understand the rare corner case, but your case doesn't appear to be one.

On switches, LB only applies to egress traffic from the switch. It doesn't matter how the traffic entered the switch.

src-dst-ip is often a good LB choice (except when heavy flows between the same two hosts (for that, some Cisco switch will also include port numbers in the hash).

If your one SRV only offers mac-src, assuming there's only one MAC, all traffic from it would just use the same link. Once it gets to the first switch, its LB choice can redistribute traffic across multiple links.
Beginner

Re: Impacts of load-balancing in etherchannel chaining

"On switches, LB only applies to egress traffic from the switch. It doesn't matter how the traffic entered the switch."

That's the answer that I was looking for.

It is switching so it doesn't matter if the frame path isn't symetric.

 

Thanks very much,

Have a nice day

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