Conditions:

Equipment: Laptop Vostro 1720, Windows XP Professional SP3, 4 Gig RAM, 300 Gig HD.

The windows driver manager reports that the ethernet device is working normally.

The WIFI card works normally

The cables and the rest of the network are up and running and it has been tested with others pc´s and laptops.

All other devices and drivers work normally.

Operations:

After reporting this issue the laptop got a motherboard replacement from Dell, and I have updated to the BIOS 1.00PARTTBld

I have reinstalled the Dell ethernet driver, but the problem remains the same.

 

The problem :

1.- I can use the ethernet network just a couple of hours a day the rest of the time the ethernet network is down, normally this are the first hours of the working day.

2.- Sometimes the ethernet leds are off even if the ethernet cable is connected.

3.-Some times the ethernet leds are on and PINGing the ethernet interface local address replies but pinging the gateway ip address does not receive an answer, the network status reports that the ethernet card has sent several packets and received 0.

4.- Restarting sometimes work but most of the time it did not.

5.- When the error occurs If I turn off the laptop for 10 minutes and then turn it on the ethernet is working again. 

6.- When the error occurs, restarting on safe mode with network functions, does not fix the problem.

 

Solution:

Thansk a lot to WilkovF and jishcat 

After intalling downloading and installing the driver Realtek  RTL8168D/8111D version: 5.720 I have been working for three days without problems.