[Hampshire] Which NIC is which?

Hi Folks.

I have an on board ethernet port designated as eth0 and I have popped a
10/100 NIC in one of the pci slots and assigned its credentials
in /etc/network/interfaces. However, unless I run proxy.sh and
designate which is the EXTIF and which the INTIF the system will try and
use eth1 and hang.

Is this normal behaviour?

TIA
Mike

Sarge 2.6 Kernel.