At work we got in a brand spankin' new Dell PowerEdge SC440. And what's the problem with brand spankin' new hardware? Driver support. Fedora Core 5 didn't install drivers for our ethernet interface. As seen in lspci...
05:00.0 Ethernet controller: Broadcom Corporation Unknown device 167a (rev 02)
How do you solve this? Well, first off, you need to make sure that you have kernel 2.6.18 or higher on your system. If you don't have this yet, and you have some other means to network access, run yum update. Otherwise you'll probably have to use sneakernet to get the kernel RPM file on there. Then, after installing and rebooting into the new kernel, add this line to /etc/modprobe.conf
alias eth0 tg3
Reboot and run netconfig.
UPDATE: You can alternatively let kudzu try to find the device itself, after you do the kernel update. First you need to make kudzu believe that this is the first time the device has been inserted. Remove these lines for /etc/sysconefig/hwconf:
desc: "Broadcom Corporation Unknown device 167a"
Run "rmmod tg3" to uload the module, then run "/etc/init.d/kudzu start" and "modprobe tg3". Run "ifconfig -a" and you should now see the ethernet interface. Run "netconfig" or netconfig -d eth1" (if you have this as a secondary interface) to configure it.