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I am not from system admin background, however due to some reasons I need to set up a cluster of some 3-4 physical servers, each running CentOS, 6.8 version.

I downloaded the centOS 6.8 version iso minimum and did the installation from a USB.

Now, I need to configure the network, and for that I referred to the directory:

/etc/sysconfig/network-scripts; and in particular ifcfg-eth0

In this file, some of the contents which were present:

DEVICE=eth0
ONBOOT=yes
HWADDRESS=AA:BB:CC:DD:EE:FF (not putting the real entries).

I have following doubts.

Q1) Does HWADDRESS in ifcfg-eth0 represent the real MAC address of the Ethernet card?

Q2) what does ifcfg-eth0 represent? Is it Ehernet card? (I assume because of 'e').

Q3) For wireless, would it be ifcfg-wlan0?

Can anyone help understand this?

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Take a look at the Red Hat sysadmin docs which describe the interface configuration files for RHEL 6.

A1) Yes, the hardware address listed must match the actual MAC address of the interface. They are used to ensure persistent interface configuration when multiple interfaces are present which may be detected in a different order each time the system boots.

A2) ifcfg-eth0 is the configuration file for the eth0 interface. Usually this is an Ethernet card, but any device which appears to be an Ethernet device may be named ethx.

A3) To expand on what I mentioned in A1 and A2, the interface name may not be an authoritative means of determining the type of interface. The interface driver may select a prefix which is non-intuitive, the driver may have an option to force the interface name and interfaces can be renamed. Wireless interfaces are typically named wlanx or wlx, but you cannot count on that. :)

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  • Thanks so much for the response. How does the system detect the hardware address? Can I put any random number?
    – CuriousMind
    Mar 10, 2017 at 8:37
  • You're quite welcome! :) The hardware address is typically stored in persistent memory (EEPROM) on the network device itself and is read by the device driver. Here's where the Intel e100 driver gets the MAC address from the device EEPROM: lxr.free-electrons.com/source/drivers/net/ethernet/intel/… . You don't want to set this to anything other than the hardware address of the device; doing so will mean the device will populate another interface since the hwaddr doesn't match. If you wish to specify a different MAC, the driver must support it when the module is loaded.
    – Rich Alloway - RogueWave
    Mar 10, 2017 at 22:02

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