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New Member

3com 1000base Network Card problem with 3550-12T switch problem

We recently installed a 3550-12T switch (10 x 10/100/1000Base-T + 2 GBIC slots) and installed 2 new 3com 10/100/1000 NIC cards onto two NT4 Servers. We then attempted to get the servers to run at 1000 but were unable to select the option of speed 1000 and full duplex on the servers although the switches were able to be modified to the desired speed and duplex. In an attempt to resolve the problem we contacted 3 com who replied with the following e-mail

> I have rang 3Com support and found out that the Network card fitted will

> run at 1ghz if 5 connections are made to the Switch.


> The properties of the network card within NT4 will not show an option for

> the 1000base connection, this is normal according to 3Com. The only

> options available are Auto,10,100 with half or full duplex etc. This

> setting has to remain on Auto, and you have to set the jumbo frame type to

> be 9000, this option is on the same screen.


> Now here's the part that I cannot get my head around, when connected to

> the switch the connection speed is by default 400 mhz, until 5 or more

> connections are made to the switch from the clients. It appears the

> bandwidth increases to 1 ghz when this amount of client connections is

> made. I do not know if your IT guy who fitted the Cisco switch knows if

> it also can run with variable jumbo frame type being selected to 9000.


> We have selected Auto on the NIC within the NT, but Charlie who is of

> until Monday 16th Sept and was the engineer, might not of selected the

> jumbo frame type to 9000 With this done the single connection is still

> only going to be 400 mhz. I can not understand how 3Com can supply a

> network card that will run at 1 ghz only if 5 connections are made, this I

> would of expected to run at 1 ghz with only a single connection.


Does anyone know if the following information is correct or are we being mislead by 3 Com? I am finding this hard to believe.


A Roberts

New Member

Re: 3com 1000base Network Card problem with 3550-12T switch prob

That response is one of the most confusing things I have ever heard. I have had issues connecting to a 3550 at 1000 with NT 4 but not as much with 2K. The NIC's were 3com. My results have been different each time. Bottom line, with Win2k, 99% of the time I can get 1000 but never with NT4 on auto. Looks like the jumbo frame config will not go up to 9000, ref


New Member

Re: 3com 1000base Network Card problem with 3550-12T switch prob

It sounds to me as if the 3Com response has to do with the observed throughput, not the speed setting. I have heard that due to driver overhead, you cannot get anywhere near 1000Mbps out of NT4. However, this should have nothing to do with how it is configured. Using jumbo frames and setting up multiple cards, you can get to 1Gpbs. On the Compaq 10/100/1000 card I dropped into an NT4 server this weekend, I left both the switch and server at auto, and they things are fine. It does have the option of setting 100, 1000 or auto for speed. Haven't used a 3Com card.