I have a Linbox with dual NICs. One connects to ISP, the other comes out to a hub (5 ports, the 5th shared w/ uplink port). I tried straight-thru and crossover from the 2nd NIC to hub's uplink port, neither worked. Why?
Now i just use straight-thru connect to port 1, and my other machine connects to port2, then speed between 2 machines always below 50M(NICs,Hub all 100M). Is this the best way it works?

Thx.

if you're using two perfectly sound cat5 cables (straight of course) Then it should work fine. what have you done to make it not work? check you get connection lights etc... on the hub and all that.

you mean straight-thru from server to hub's uplink port? and clint to the normal ports.

Thx

if you cant get speeds greater than 50M, it might becuase you have cheap Hubs and they are not allowing full Duplex, Which would put your speed right at 50M.

To the uplink port you need crossover. To one of the regular ports, you need straight through.

so, from server use crossover to uplink port of the hub, and use straight-thru connecting clients to regular ports. is it rite?

While this solution should work, it's not real good practice. the Uplink port is used to cascade hubs/switches together. i.e. if you need more ports than on your hub, you can connect a second to expand the number of ports. The uplink port does the exact same thing as a crossover cable. The crossover cable exists for (old) hubs/switches that didn't come with an uplink port built in. Basically, if you plug a crossover into an uplink, you switch the pinouts, then switch them back, accomplishing nothing.

Anything that is a end machine (computer, server, printer, etc.) connects to the hub/switch with a "straight through" cable. Crossovers and uplink ports should only be used to connect a hub/switch to another hub/switch. Hopes this clarifies things a bit....

Atrivis

thx a lot. the reason i can only get 50M at most is in the hub itself then?

The point of the crossover in the uplink is that you can't just connect your computer to it without a crossover since the pins ARE changed in the uplink port.
Are your cat 5 cables using the full 8 pins or just 4? Do you have full duplexing turned on?

Is it true that when it connects to a hub, a 10/100M NIC turns to half duplexing and when connecting to a switch, it goes to full duplexing?

Not necessarily. It depends on the hub/switch, your wiring, and your NICs.

i'm using Linksys EFAH05W EtherFast® 10/100 5-port Auto-Sensing Hub; RH9 at samba server, and winxp pro as client. cat5 wires.
when i copy files, i see in the taskmanager the networking usage just 40% of 100Mb/s.
How can I get full use of it?

1) Do your cat 5 cables have 8 or 4 wires?
2) If 8, do you have full duplexing enabled on both NICs?
3) Do the LEDs indicating a link speed of 100 Mb light up on the hub?

First of all, thx, moses.
1) I think so, they are cat 5e;
2) How can I enable NICs to full duplexing if it's not automatically set? In operating systems or other?
3) the LEDs do light up when I turn both computers on.

Thx again.

Just because they are cat 5 doesn't mean they use all 8 wires. To check, look closely at the RJ45 connector. Usually they are clear plastic, and you can easily see either 4 or 8 wires. If there are only 4 wires, you won't get full speed from them.
The full duplexing depends on your drivers, cards, and hub. What kind of cards do you have? What is your hub?