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Two Dell server each running Windows 2008 R2 both using the Broadcom onboard NICs. Both servers were setup using the Broadcom wizard to Team the NICs with LACP protocol. The switch is a Dell 5548, both sets of NICs are in their own LAG on the switch, with the LACP protocol on for the Lag.

Summary, when transferring Data between the two servers, I see 100-110 MB/s per second, and when looking at the Network Utilization under Task Manager, I see the 2 Gbps network link at 47-49% utilization.

Do I have something configured wrong? Should I be seeing 80-90% Network Utilization and 175-200 MB/s transfer speed, or am I misunderstanding the concept of Teaming?

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  • Sounds like you manually setup the LAG on the switches instead of letting LACP do it; was there a reason for this? You shouldn't have to set them up on the switches when using LACP. Can you pull up perfmon and see if the traffic is all over one NIC? What kind of data transfer are you doing; are you sure the NICs are the bottleneck? Teaming is simple link aggregation, depending on how you use that you can get different results out of it, there's a couple configurations where you should expect to see 80%+ utilization.
    – Chris S
    Dec 1, 2011 at 15:54

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I think that an individual TCP connection will only use one of the NICs, which will be selected by doing a hash on either the MAC addresses, IP addresses, port numbers, or some combination of those (there will hopefully be settings on the servers or the switch to let you configure this).

I would try copying data onto one of the servers from 3 or 4 different servers simultaneously and see what the overall network utilisation looks like during that test.

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  • Good idea. You appear to be correct, when transferring two files between the 3 servers, I see utilization spike up between 50-80%. That would appear to collaborate your idea that only one NIC will used per TCP connection. Any thoughts if this can be changed?
    – Aaron
    Dec 1, 2011 at 16:46
  • Hopefully the switch's management software should let you choose the algorithm that the LAG uses to determine which link to use. Never used Dell switches so I can't be more specific I'm afraid!
    – meulop
    Dec 1, 2011 at 17:38
  • Look at my problem. I think that is one of the rare constellations where you can load-balance a single connection across all lines.
    – Nils
    Dec 1, 2011 at 20:17

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