I have a Linux desktop for which lspci reports as having a realtek
8110/8169. I could not install it via NFS so I popped in a 3COM card
and installed it with SL4.5. After installation, I tried to switch back
to the onboard LAN. I removed the 3com card and modified the network
config by editing/etc/sysconfig/network-scripts/ifcfg-eth0 and
/etc/modprobe.conf. Basically replacing the ifcfg-eth0 with the correct
MAC address and modprobe.conf with the right driver. There is an 
r8169.ko in the /lib/modules which I believe is the correct driver 
because I used a sysrescuecd image on the box and it correctly detected 
the chipset, loaded r8169, and activated the card without any difficulty.

When I try to do an ifup eth0, I get an error message saying that the
device has a different mac address than what was expected and it ignored
my attempt.  I'm stumped by this.    My understanding may be dated but
as far as I know the information to start the network correctly is in 
ifcfg-eth0 and modprobe.conf.  I notice that a modprobe r8169 does not 
generate any messages in dmesg.  So, it could be that r8169 is not the 
correct driver.  Except for the fact that sysrescuecd used this driver 
and it also has a 2.6 kernel.

Can anyone shed any light on this?  Thanks

Ken