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Altering Etherchannel Algorythm

Hello Experts. I currently have 3 x 3750 switches that are connected in a Circle and provide the Same VTP domain over 3 physical locations.Each Switch is a VTP server and at the moment I have the 3 swicthes setup utilising Etherchannel load balancing "Src-Dst-IP"globally..The 3 switches are trunked dot1q to each other using L2 port channels and propagate a number of vlans.

I am considering altering the load balancing method to SRC-DST-MAC asI am getting some network equipement that I want to use on this environment which does not uspport "Src-Dst-Ip" as an option for NIC teaming.

the only trouble is on the Access ports I have a number of servers that hangoff these switch's via NIC Teaming (and etherchannel on the switch ) - I think the servers are load balancing packets over the bundle based on Round Robin, but in order for me to be able to make use of my new Newtork equipment I will have to change the load balancing algorythms for Etherchannel globally.

The question is how intrusive would it be to do this, especially for servers that are connecting to the switch in question - bearing in mind the servers are currently set to Round Robin, the Access port port channels are set to "SRC-DST-IP" because the switch is set to that globally.

For the dot1q inter swtich trunk links (2 ports in a bundle 2 x 1GIG) I can easily disable one interface so that the switch only has one available path to choose. When I make the change globally as this point the Inter switch links will only have 1 port to send and recive traffic so I dont think that this will be to intrusive.

Ultimatley I am unsure of how the servers that are already setup in a round robin fashion will react to the switch algorythm changing to SRC-DST-MAC, would I get out of order packets to the server, I belive it all works very well at the moment but wanted a bit of advice?

Kind regards

2 REPLIES
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Re: Altering Etherchannel Algorythm

Hello Mcnairan,

>> I am considering altering the load balancing method to SRC-DST-MAC asI  am getting some network equipement that I want to use on this  environment which does not uspport "Src-Dst-Ip" as an option for NIC  teaming.

Be aware that the two sides of a same etherchannel bundle don't need to agree on a single load balancing algorithm.

This aspect is not negotiated even if using LACP to setup and to keep up the bundle.

There are cases where, this can even be helpful.

I would not change the algorithm on your switches and I would setup the new bundles they should work fine.

Hope to help

Giuseppe

Re: Altering Etherchannel Algorythm

Hello Experts. I currently have 3 x 3750 switches that are connected in a Circle and provide the Same VTP domain over 3 physical locations.Each Switch is a VTP server and at the moment I have the 3 swicthes setup utilising Etherchannel load balancing "Src-Dst-IP"globally..The 3 switches are trunked dot1q to each other using L2 port channels and propagate a number of vlans.

I am considering altering the load balancing method to SRC-DST-MAC asI am getting some network equipement that I want to use on this environment which does not uspport "Src-Dst-Ip" as an option for NIC teaming.

the only trouble is on the Access ports I have a number of servers that hangoff these switch's via NIC Teaming (and etherchannel on the switch ) - I think the servers are load balancing packets over the bundle based on Round Robin, but in order for me to be able to make use of my new Newtork equipment I will have to change the load balancing algorythms for Etherchannel globally.

The question is how intrusive would it be to do this, especially for servers that are connecting to the switch in question - bearing in mind the servers are currently set to Round Robin, the Access port port channels are set to "SRC-DST-IP" because the switch is set to that globally.

For the dot1q inter swtich trunk links (2 ports in a bundle 2 x 1GIG) I can easily disable one interface so that the switch only has one available path to choose. When I make the change globally as this point the Inter switch links will only have 1 port to send and recive traffic so I dont think that this will be to intrusive.

Ultimatley I am unsure of how the servers that are already setup in a round robin fashion will react to the switch algorythm changing to SRC-DST-MAC, would I get out of order packets to the server, I belive it all works very well at the moment but wanted a bit of advice?

Kind regards

Hi,

EtherChannel load balancing can use MAC addresses, IP addresses, or Layer 4 port numbers with a Policy Feature Card 2 (PFC2) and either source mode, destination mode, or both. The mode you select applies to all EtherChannels that you configure on the switch,but recommended is to understand the flow and try to apply the change in the switch as per the alogorithm.

For example If the traffic on a channel only goes to a single MAC address, use of the destination MAC address results in the choice of the same link in the channel each time. Use of source addresses or IP addresses can result in a better load balance.

Load Balance must be configured globally and the load balancing       option cannot be changed on a per port basis.

Hope to help !!

Ganesh.H

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