I am sorry, I have been out this two last days, so...
I compiled rtl8139 diagnostic. Resultas are:

Index #1: Found a RealTek RTL8139 adapter at 0x1800.
* A recognized chip has been found, but it does not appear to exist in I/O space. Use the '-f' flag to show the status anyway.

I use -f option. Results:

Index #1: Found a RealTek RTL8139 adapter at 0x1800.
Realtek station address ff:ff:ff:ff:ff:ff, chip type 'Unknown version'.
Receiver configuration: Unknown/invalid
Rx FIFO threshold 2048 bytes, maximum burst 2048 bytes, 64KB ring
Transmitter enabled with NONSTANDARD! settings, maximum burst 2048 bytes.
Flow control: Tx enabled Rx enabled.
The chip configuration is 0xff 0xff, 10baseT full-duplex mode.
Interrupt sources are pending.
Rx Complete indication.
Rx Error indication.
Transmit OK indication.
Transmit Error indication.
Rx Buffer Overflow indication.
Rx Buffer Underrun indication.
Rx FIFO Overflow indication.
unknown-0080 indication.
unknown-0100 indication.
unknown-0200 indication.
PCS timeout - packet too long indication.
PCI System Error indication.
(null) indication.
(null) indication.
(null) indication.
(null) indication.
Use '-a' or '-aa' to show device registers,
'-e' to show EEPROM contents, -ee for parsed contents,
or '-m' or '-mm' to show MII management registers.

other options does not add too much.

In /proc/ioports I found the phrase:

1800-18ff : Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+.

Any idea?

Sorry, results are not right, I did not remember I did ./network stop. Diagnostic is:

Index #1: Found a RealTek RTL8139 adapter at 0x1800.
Realtek station address 00:40:ca:be:25:3f, chip type 'rtl8139C'.
Receiver configuration: Normal unicast and hashed multicast
Rx FIFO threshold 2048 bytes, maximum burst 2048 bytes, 32KB ring
Transmitter enabled with NONSTANDARD! settings, maximum burst 1024 bytes.
Flow control: Tx disabled Rx disabled.
The chip configuration is 0x10 0x8d, MII half-duplex mode.
No interrupt sources are pending.
The RTL8139 does not use a MII transceiver.
It does have internal MII-compatible registers:
Basic mode control register 0x1000.
Basic mode status register 0x7809.
Autonegotiation Advertisement 0x01e1.
Link Partner Ability register 0x0000.
Autonegotiation expansion 0x0000.
Disconnects 0x0000.
False carrier sense counter 0x0000.
NWay test register 0x0704.
Receive frame error count 0x0000.

I have reviewed the results, but I don't find nothing strage.

hmm.....how about what type of cable is used (TP/straight)? If there is no hub or switch in between shouldn't cable be straight?

I sopose network cable is TP (twisted pair) right? Direcct connection between pc's and without switch/hub on TP cable..
If that is case it will newer work..

do the linklight test form my previous post.
do the mii stuff in the links in inge_ninge's post.

For cabling computer to computer with NO hub you need a CROSSOVER cable. All network cables are twisted pair. For 1000bT (gigabit) you need catagory 5e (or was it 6 as a min?), for 100bT you need catagory 5 and for 10bT you need catagory 3, bigger numbers will work ie you can do 10bT on cat 6 etc.

just useless knowledge for the curious:
TP means all the little wires inside are twisted, all network cables for ethernet are like this. Straight means not crossover which means the plug on one end matches the one on the other (green on the left to green on the left), this is used to connect a network card to a hub/switch/router. Crossover means that certain pairs of wires are crossed on one end of the plug (specifically the transmit and the receive pairs) for netcard to netcard or even hub to hub connections. Many hubs/routers/switches also have an uplink port (cheap ones use one "port" with 2 plugs so you can only use one or the other of these) which is quite simply a port that is crossover so you don't need a cable that is crossover and has no other special significance.

I am using a CROSSOVER cable. If you read my previous post It works under Windows. No problem with the cable and type of conection. I don't understand very well what starea tries to said (my English is not very good), I appreciate his help but I think he is not right.

That's OK. I must apologize becouse i didn't read all of previous posts.

Hi everybody,

I'm on a MDK 9.1 and I've got exactly the same problem with the Realtek 8139...

Here is what I got :

[root@gandalf root]# /home/downloads/ether/rtl8139-diag
rtl8139-diag.c:v2.10 9/18/2002 Donald Becker (becker@scyld.com)
http://www.scyld.com/diag/index.html
Index #1: Found a RealTek RTL8139 adapter at 0xc800.
Realtek station address 00:50:bf:dc:8c:88, chip type 'rtl8139C'.
Receiver configuration: Unicast and no multicast
Rx FIFO threshold 2048 bytes, maximum burst 2048 bytes, 32KB ring
Transmitter enabled with NONSTANDARD! settings, maximum burst 1024 bytes.
Flow control: Tx disabled Rx disabled.
The chip configuration is 0x14 0x4d, MII full-duplex mode.
No interrupt sources are pending.

Something new about this problem or do I have to switch again to M$ :-( ?

Yes, I finally solved the problem.
I don´t know why when I installed Red Hat 8, It chose Multiprocessor option enable in Kernel in my notebook computer. When I tried to disable this option in Kernel and recompiled it , it gave me error. I had to delete my .config file, and chose all options in the kernel again, and recompile kernel, of course with single processor option.
Unfortunatelly, nobody could help to find the problem. Donald becker never answered me.
I think I had an error with multiprocessor kernel option. Check if you have also this option enabled. Of course, I don´t know exactlly why it doesn´t work , but the result was that I solved the problem.
Post your news, I will try to help you, if I can.

i got exactly the same problem, the only difference is that i'm using SuSE Linux 8.1 with an "Allied Telesyn AT-2000U" Ethenet adapter
so i don't know if this is possible with suse linux, but where could i toggle that multiprocessor option you're talking of?

Hi Maschinegun, I followed this thread and I have a very similar problem , too. I have 2 pc's connected with a router and I have cable modem service. If I boot XP on both machines, everything works fine, if I run red hat 9 on one machine, it fails to obtain an IP address, I tried basically everything that has been posted in this thread... except of the multiprocessor thing, I am not quite which .config file you are talking about. I also never compiled a kernel. Anyways, I am looking forward to your next post
Thanks a bunch
ps
Also do you think I should update the bios??

after downloading the sourcecode from http://www.scyld.com it came to my mind that my ethernet adapter is an ISA card

could this be the problem?

Hi,
It is not a Bios problem. In fact, it works under Windows, so it is not a Bios Problem.
Ok,go to the directory /usr/src/linux-2.4.20. Run

make xconfig.

Select, processor type and features. Check if Symmetric multi-processing support is enabled. If it is enabled, select no, save changes and recompile the kernel. It is very easy just run

make dep
make clean
make modules
make modules_install
make
make install

ingo, I don't think that ISA cards are the problem, except it is a ISA boards based on the DP83800 chip. You have to check your ISA card type, and check if it is enabled in the kernel.

is it normal that make modules and make modules_install gives you errors???
The next time I booted the kernel said that multi-proc. is disabled, but it still does not work, when I type dmesg it says that I have 2 processors, cpu0 and cpu1, both are Intel Pentium 4 CPU 3.06Ghz stepping 07, I only have 1 processor though, any ideas or suggestions??

Well, it is not easy. What I did, was to delete file .config in directory /usr/src/linux-2.4.20, and then make xconfig, and I selected all kernel options again.
Something was corrupted and I had also errors like you have
Of course, try to download files .config with kernel options of computers similar to yours, for using them as reference.