Gigabit LAN questions; slow Dlink card

  • I have 3 PC's with gigabit NIC's; two of them are Abit IC7-G's with onboard Intel GBe NICs; and the other is the pfSense box with a Dlink DGE-530T (the new revision).

    Everything is plugged into the same unmanaged Gateway gigabit switch.

    When the MTU is at the default 1500 on the two Abit based PC's; iperf reports rates around 70Mbps.  When I crank the MTU to the 9000 size (the maximum allowed by the switch if I read the google docs right) the rates shoot up to a respecable 750-900Mbps.

    However; the pfSense box with the dlink (an old amd-700 clunker) I can't get iperf to show numbers over 8Mbps?  I've tried various sysctl tweaks; but nothing changes my results more than what you might expect from a margin of error.  I do notice both NIC's in the pfSense box are on the same IRQ; could that be a problem? Everything seems to be worknig fine. The CPU never goes very high; even during the iperf tests.

    What am I missing; maybe this dlink NIC is a dud?

  • IRQ sharing is not really a good thing. Maybe you can try to solve this by swapping around PCI slots or changing bios settings. If nothing helps try a different nic.

  • You will probably see a max performance of around 200-250Mbps. My old Dell Dual Pentium 2 350 maxes its CPU out at that rate. With this being the case, plus the fact that a 700Mhz box won't be able to route traffic faster than 100MB card, if a regular 100MB card works fine I would just use that.

  • Shuffling the NIC's in their slots I got them from the same IRQ 10 (even the IDE controller was using IRQ 10). Now they are on different IRQ's of 10 and 12; but 10 is still shared with the IDE controller and one of the NIC's.

    iperf now reports numbers in the 90-100Mbps range; so there's a bit of an improvement there. The reason I was concerned about speed is I was thinking of stuffing a couple drives on this and using it as a file server as well. And I like to know how well things are working; and that they are working as they are supposed to.

    Ehhhh…. just went to test the cpu usage again; and I see that my rates have dropped back to the 10Mbps range again.  Odd....

    Oh - just realized if I start the iperf server on the main PC the rates are in the 8Mbps range; but if I start the iperf server on my pfSense box the rates are in the 100Mbps range.  I'll take a closer look at the bios; maybe I missed something.

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