The reason only one ethernet card shows up is that you did not enable the
second one. That is a default setup.
Generally speaking ethernet just works. The only time I have had to
do any intervention was a wrong module (driver) loaded. This may
be your problem.
Please list the ethernet cards ( You can use lspci as root for this info)
name, make and model number.
To enable the second ethernet card as root type:
iconfig eth1 up
Now test by looking at ifconfig again you should see
You can try getting an ipaddress by using this command:
You will not get a return response. It may look like it
Look at ifconfig again to see if you got an ipaddress.