Re: NIC question & troubleshooting

x-posted to some other useful groups -

"George" <> wrote in message
news:glv10h$3nr$...
> Jeff Liebermann wrote:
>> On Thu, 29 Jan 2009 11:38:41 -0500, George <>
>> wrote:
>>
>>> Caught me, I was trying to decide whatever result it presented referred
>>> to what direction relative to one of the hosts to help me decide what to
>>> look at.
>>
>> Good question, but an obvious answer, which you already supplied.
>>
>> Hint: If you have a problem that needs solving, then please supply:
>> 1. What problem are you trying to solve?
>> 2. What hardware and software do you have to work with?
>> 3. What have you done so far and what happened?
>>
>>> I am troubleshooting a general speed issue and isolated it to the wired
>>> LAN speed from the server which is highly asymmetrical.
>>
>> I've seen this literally dozens of times. Lots of causes ranging from
>> bad NIC's, NWAY negotiation failure, CAT5 cable wiring problems,
>> connector failure, media converter failure, hung ethernet switch,
>> full/half duplex problems at the NIC, overly busy server, etc. I'm
>> going to be my usual obnoxious self and not offer any more until you
>> disclose what hardware you're working with and how you're doing the
>> iperf testing (specific command line incantations). That's because
>> UDP and TCP testing often yield very different results.
>>
> just vanilla TCP using iperf -c <server IP>
>>> iperf reported 300 kbit in one direction and 70 Mbit in the other
>>> direction just working on the wired 100 Mbit LAN using my notebook and
>>> also another server for testing.
>>
>> Wrong on both numbers. I consistently get 90-95Mbits/sec from a
>> 10/100baseT ethernet switch. Obviously, the 300Kbit/sec is also
>> wrong. You might try removing the intermediate switch, grab some
>> known good CAT5 cables, and go directly from the "other" server and
>> your notebook. Also, check the settings on the ethernet port on both
>> machines. You can sorta create the problem by having one set to full
>> duplex, and the other to half duplex.
>>
>> Replace the cables, test server, and/or switch, one at a time, until
>> the problem evaporates. It's called troubleshooting by substitution.
>
> Agree, it is a remote location and I simply ran out of time because of an
> ice storm that was closing in. I replaced the cables and have a GigE
> switch on order as a replacement.
>
>
>>
>>> Updating NIC drivers and turning off scalable networking brought the low
>>> speed up to 5 Mbit which is still lame.
>>
>> It shouldn't make any difference. Since updating the driver has such
>> a derastic effect, you might consider the possibility that the
>> unspecificed device with the NIC card is having a bad day. It could
>> be busy from some errant process. It could have a bad NIC.
>>> The server has a GigE card
>>
>> Any particular model number GigE card?
>
> Its a Dell Poweredge 1950 with dual onboard Broadcom Net Extreme II NICs.
> I configured the other NIC and switched over to it but there was no
> difference.
>
>>
>>> and there is a 100Mbit unmanaged switch.
>>
>> Maker and model? Yeah, I know I'm demand a lot by asking you to
>> supply such details. However, there are some boxes out there that are
>> little better than defective.
>>
>
> It is a D-link something (can't read my notes)
>
>>> Forcing link speed on the server to various auto/full/half didn't make
>>> much difference.
>>
>> Forcing it where? At the server? At the laptop? With a mechanical
>> switch on your unspecified unmanaged switch?
>
> At the server.
>
>>
>>> I suggested they replace the switch with a GigE switch which makes sense
>>> because there are two servers with GigE capability.
>>
>> Yeah, that makes sense if the intermediate wiring is 1000baseT
>> qualified? What manner of cable and how long?
>
> The switch is right above the servers so only short patch cables are
> needed.
>
>>
>>> I think the server NIC just doesn't like talking to the switch.
>>
>> I also don't like talking to people and devices that I know nothing
>> about.
>>
>>> The server had a second onboard NIC and I switched to it and also tried
>>> various switch ports and it didn't make a difference.
>>
>> Try a 2nd laptop in place of the server. See if the unspecified model
>> GigE switch is the problem.
>>> I have tried switches like -d but it simply gives both results leaving
>>> you to wonder which is what.
>>
>> If you have both directions, does it really matter which is which as
>> long as they're the same? Methinks you're avoiding the problem.
>>
>> Your question has absolutely nothing to do with wireless or wireless
>> internet. You might consider asking the same question (with the
>> missing details supplied) in one of the networking newsgroups.
>>
>>
> Yes, thank you much for your interest and suggestions. I didn't go into
> big details initially because I just wanted to understand what iperf was
> telling me.