Description of Problem:

When i boot the linux system everything seems to be fine even the network 
, i can able to connect to the network , telnet it and everything.After 
few minutes the network drops out.It happens constantly.I have tried with 
network restart samba restart and ifconfig up/down.But no use.All of a 
sudden i can see the network from my windows machine , if i ping it its 
coming with reply followed by request time out.It happens constantly.The 
network is not at all consistant.

Version-Release number of selected component (if applicable):
red hat linux 7.1

How Reproducible:
i can reproduce this every time

Steps to Reproduce:
1. boot the sytem ping it from someother system or even telnet it
2. wait and watch , after few mins the network drops u cant even do 
anything
3. its disappering from the network neighbourhood.

Actual Results:
   network dropping
 
Expected Results:
  i should be able to see the network

Additional Information:
  iam using Ethernet RTL 8139