Server Port Aggregation

Unanswered Question
Nov 2nd, 2007

Question: Is it possible to take an HP or Dell server with dual 1G Ethernet ports and create a 2G logical EtherChannel (port-channel interface) connection to a Catalyst switch (4948-10GB or 3750) that will give me a total 2G of usable bandwidth? I wouldn't expect to get exactly 2G of bandwidth, but I would like to get close.

I've seen a lot of examples creating EtherChannel connections from servers to Catalyst switches for the purpose of redundancy (in case one port/card/cable fails), but they are still only showing 1G of usable bandwidth.

Maybe I'm misunderstanding the term 'aggregation', but I would expect this to mean that by aggregating 2 - 1G ports, I'd be getting 2G of bandwidth.

Cisco TAC is telling me differently. This is from a case I have opened…

>

>From the case notes, I understand that you have a port channel with 2

>gigabit Ethernet ports. You stated that you are just getting 1 GB of

>throughput.

>

>I have to tell you that is perfectly normal and it is the way the ether

>channel works. Your configuration is perfect and everything seems to be ok.

>Let me explain why this is an expected behavior. The ether channel is not a

>feature to increase the throughput of your network or a link between two

>devices. This is a feature that improves the interfaces performance by

>avoiding the traffic to overwhelm one single interface. For example let say

>that you have a port channel of 5 ports this does not mean that you will

>have throughput of 5GB, what this means is that the traffic has 5 options to

>reach an specific device. Which means that you can split 1GB of throughput

>on 5 different interfaces depending of the algorithm you use. You can check

>the algorithm on the following link:

>

To restate my question(s)…

Can I get 2G of usable bandwidth from 2 - 1G ports on my server? Or is the TAC engineer right?

If the TAC engineer is wrong, does anyone have any examples/references to point me in the right direction?

Thanks!

Jeff

I have this problem too.
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glen.grant Fri, 11/02/2007 - 16:15

Nope he is right that is the way etherchannel works . A specific conversation will always go down 1 link depending on the the way the channel is configured , whether it be on source mac or ip or ip source destination . Say you have a 3 gig port etherchannel , this will divide up the total traffic across the ports instead of everything coming down 1 pipe but any one conversation traverses just 1 of those links so it has a total of 1 gig bandwidth to use minus whatever other traffic is already riding that port.

jeff.christensen Sat, 11/03/2007 - 06:54

So you're saying that there in NO WAY I can get more than 1 Gig of bandwidth out of my dual 1G server using EtherChannel?

Any other way I can do this?

Am I going to have to look at a 10G NIC?

jeff.christensen Sat, 11/03/2007 - 11:01

We are using both HP & Dell servers running Win 2003 Server. They are both backup servers, so the preference would be to get more bandwidth coming INTO the server from the switch.

Were you able to get 2G usable bandwidth out of the dual 1G NICs under Linux?

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