Redhat 5 missing eth0

[yc_2]

Hi,

We are running Redhat 5 in DL380. The system was using eth0 for network interface. We shutdown the system to replace the rack. After the server powerup, eth0 is missing.

The following was performed with the output:

#ifconfig eth0 up

eth0: unknown interface: no such device

#/etc/init.d/network restart

Bringing up interfac eth0: dvice eth0 does not seem to present, delaying initialisation

Any advise is appreciated.

[Matti_Kurkela]

Which generation of DL380?

Does "lspci | grep -i ethernet" detect any network interfaces? If not, there might be a physical connection issue, e.g. when the server was moved, a card might have risen a bit in its slot, causing an incomplete connection. (The solution for that is to power down the server, open it and then make sure that all the cards are all the way in their slots, and the riser module is completely seated on the system board.)

Does "ifconfig -a" display any network interfaces other than the loopback device? If not, it might be a kernel module loading issue: for example, you might have been previously running an older kernel with an add-on NIC driver, and when the system was rebooted, it started using the latest kernel... which might not have a corresponding add-on driver module.

If "ifconfig -a" displays other network interfaces but not eth0, check the HWADDR lines in your /etc/sysconfig/network-scripts/ifcfg-* files. The MAC address of eth0 should be listed in /etc/sysconfig/network-scripts/ifcfg-eth0 only. If the same HWADDR line is listed in other ifcfg-* files, the ifup script might become confused and think that the network interface needs to be renamed to something other than eth0.

Note that HWADDR line and MACADDR lines in ifcfg-* files seem very similar, but have very different purposes:

• HWADDR means "these are the settings for a NIC with this MAC address". If a NIC has a different ethN name but the correct MAC address, the system will automatically rename it. This ensures the other NIC names won't get reassigned if you add/remove a single NIC to/from the system.
• MACADDR means "change the MAC address of this NIC to this value". This can be useful if you replace a broken NIC on a system that has software licenses locked to a particular MAC address.

Obviously, you should never use HWADDR and MACADDR together, or great confusion will result. By default, RHEL 5 adds HWADDR to each ifcfg-* file the first time a new NIC is detected. In some cases, an administrator might prefer the "old RedHat Linux way" of NIC name allocation: that can be done by removing all the HWADDR lines from all ifcfg-* files.