Ethernet Link goes down after the FS mount in MPC8540....

Hi All,

I have a peculiar problem. I am working on a MPC8540 processor with 3
ethernet interface. I am using the 2.4.20 Montavista Kernel with
Gianfar.c as the ethernet driver. When the kernel boots up it reads the
PHY id correctly and brings up the link also and i am also doing a DHCP
request in the kernel. It gets an IP address also without any trouble,
but as soon as i get the linux prompt..i am unable to ping external
network and moreover my ethernet link also goes down. So to debug a
bit, I manually brought down the interface and brought it up from the
prompt using Ifconfig. When it comes it auto-negotiates correctly for
the speed and says "link is up" but my ethernet link to the switch is
not there eventhough it claims Link is up. I am really puzzled ....what
might have gone between the interface bring up and FS mount.
Can anyone pls shed some  light on this.

Regards
sivam