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EtherChannel Load Balancing

Hi all, just a question I'd like to have confirmed if possible.

We are running Etherchannel between 2 6500's, and have a back-up

running over it from one server to another as such:

Switch 1 <-4 port etherchannel-> Switch 2

Server 1 <- back-up traffic -> Server 2

So it's always traffic from a server on 1 switch to a server

on the other switch, so always same source and destination. I've done the

show channel hash command on both switches and it always chooses port 1/2

for the traffic, given the same source/destination on each switch.

So my belief is that any of the available options for load-balancing

being source or dest mac, source/dest IP address or even layer 4 port would give

the same result in that it is always the same source and destination and i imagine

the back-up stream would follow the same source/dest ports in the stream and so

will always go over the same single port in the channel, can anyone please confirm

that I'm on the right track there ? And that it will always use only one port ?

Many Thanks !



Re: EtherChannel Load Balancing

You are correct indeed. Traffic between two hosts always utilizes the same path as long as it is available. I believe this implementation was partly chosen to prevent the channel causing out-of-sequence packets.

Conclusion: An etherchannel is only effective when you run traffic between a large amount of nodes (which is normally always the case)

On the other hand: regarding performance, you have little to gain from using more than one link while the throughput will still be limited by the host adapter's capacity. I assume that we are talking all gigabit links here for both the channel and the servers.



New Member

Re: EtherChannel Load Balancing

Hi Leo,

Thanks for the reply, the etherchannel links are all gig's and the servers in question are also on gig interfaces. We run a lot of other connections through these core switches, it's just this one that got up to 40% utilization so was more noticeable.

Thanks again for clearing that up for me.


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