Gig Etherchannel loadbalancing

Unanswered Question
Apr 12th, 2007

Hi Folks,

I am trying to understand how the algorithm for Etherchannel load balancing works. If is select port-channel load-balance src-ip and i have say 4 channel members (g1/0/1,g1/0/2,g1/0/3,g1/0/4) lets assume that IP1 goes to g1/0/1 when all are active. If g1/0/4 goes down, will IP1 still remain on g1/0/1 or will it be re-assigned? The question really is whether the traffic assigned to a link will be remain on the link if another member fails?



I have this problem too.
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alanwright1 Thu, 04/12/2007 - 06:20

Hi Mahmood,

So you are saying that there will be a global re-assignment within the etherchannel if any member fails?



pciaccio Thu, 04/12/2007 - 06:22


The EtherChannel Frame distribution hashing algorithm performs an XOR operation on one or more low-order bits of the addresses. For a 2 port bundle the last bit is used. For a 4 port bundle the last two bits are used. For an 8 port bundle the last 3 bits are used. If a link fails then the traffic will move to the remaining links. Hope this helps.. Please rate...

alanwright1 Thu, 04/12/2007 - 06:28

Assuming I started with a 4 port bundle, one member subsequently failed (3 remaining), would it still XOR on the last two bits?

Also in the XOR, does the IP XOR with the channel member number?




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