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Webcast-Catalyst9k
New Member

4500 Etherchannel throughput

If I have a 4424 card that effectively has 1gb backplane access per group of 4 ports, it seems to me there is no benefit of running a 4 port etherchannel (1gb each port) to the same group of 4 ports because only 1gb throughput could be achieved to the backplane. If I split the etherchannel across the 1st port of each 4 port group, then theoretically I get the full 4gb (obviously depends on what is setup on the remaining ports).

My question is would Etherchannel try to make use of the full 4gb, or is there some caveat in the logic that the 4gb is first dealt with on-card BEFORE sending traffic onward to the backplane, which would imply that maybe its still a 4gb>1gb funnel. Any ideas, thanks?

2 REPLIES
Purple

Re: 4500 Etherchannel throughput

It is sort of misunderstood on how etherchannel works . It is link aggregation that devides the traffic over 4 ports . Any one conversation is always going to flow down "one" of those links so for that conversation he has a 1 gig pipe , that is just the way it works . You can change on what it looks for the hashing algorithm , you can use mac address , or ip source and destination as the source . Having 4 ports just reduces the traffic that would flow over say a single port .

New Member

Re: 4500 Etherchannel throughput

Thanks for the response. It's not that I misunderstand how it works, I realise that in practice each conversation is distributed across each physical link.

I guess maybe I'm assuming that because the 4 links appears as a single link in the logic (i.e. spanning-tree), then I wonder if the received traffic somehow ends up into a single link to the backplane and treated sequentially in that manner. If all 4 links still work in parallel upstream (across backplane), then 4gb would be really achievable. I suspect I'll have to do some throughput tests to prove this, but wanted to see if anyone has already been through this process or understood that aspect.

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