The moral of the story today is beware of servers that have had a long history of changing networking configurations and network interfaces, as you never know what you are going to run into.

While working on a RHEL 5.4 box and attempting to make few minor changes to eth4 and up the interface, I was smacked with the error below.

_{e1000 device eth4 does not seem to be present, delaying initialization}

This was very much suck.

Ifconfig-eth4 contained what you see below

_{DEVICE=eth4
BOOTPROTO=static
ONBOOT=yes
IPADDR=192.168.13.11
NETMASK=255.255.255.0}

So first i hit up /etc/modprobe.conf and verifed that the correct driver module was being aliased for the interface.

_{alias eth4 e1000}

Ok check. Modprobe.conf looks good.

Now re-initialize driver

_{modprobe eth100}

Then onto check lspci to make sure that the driver initialized all the interfaces. Note that there are two different versions of the 82546EB driver, which tells me that the driver was only initialized for two of the interfaces initially.

_{2a:01.0 Ethernet controller: Intel Corporation 82546EB Gigabit Ethernet Controller (Copper) (rev 01)
2a:01.1 Ethernet controller: Intel Corporation 82546EB Gigabit Ethernet Controller (Copper) (rev 01)
2f:02.0 Ethernet controller: Intel Corporation 82546GB Gigabit Ethernet Controller (rev 03)
2f:02.1 Ethernet controller: Intel Corporation 82546GB Gigabit Ethernet Controller (rev 03)}

Turned my attention back to the ifconfig-eth4 and the fact that there was not a MAC address defined in the config file. Grabbed the mac address out of /etc/sysconfig/hwconf and added it to the ifconfig-eth4 config file

_{class: NETWORK
bus: PCI
detached: 0
device: eth4
driver: e1000
desc: "Intel Corporation 82546GB Gigabit Ethernet Controller"
network.hwaddr: 00:04:23:cb:89:2e
vendorId: 8086
deviceId: 1079
subVendorId: 8086
subDeviceId: 1179
pciType: 1
pcidom:    0
pcibus: 2f
pcidev:  2
pcifn:  0}

Then ifup works. Day is saved.