Tag Archives: mac address

Correcting the eth0 MAC Address in RHEL or CentOS

Cloning machines in VMWare is really straightforward thing. However once you do clone a machine, you’ll be left with new MAC addresses for the network cards. In a typical scenario the cloned RHEL or CentOS machine will boot up without the local network interface. You’ll typically see the following during boot.

Bringing up interface eth0: Device eth0 has different MAC address than expected, ignoring.

The reason for this is that

/etc/sysconfig/network-scripts/ifcfg-eth0

contains a variable called “HWADDR=”. Do the following to add the appropriate MAC address and restore networking functionality.

  • As the root user (or a user with appropriate permissions)
  • Type “ifconfig -a”
  • From the displayed information, find eth0 (this is the default first Ethernet adapter)
  • Locate the number next to the HWaddr. This is your MAC address

A typical output would be as follows.

eth0      Link encap:Ethernet  HWaddr 00:1B:21:1F:66:88
          inet addr:192.168.0.5  Bcast:192.168.0.255  Mask:255.255.255.0
... the additional output has been removed...

Now you edit

/etc/sysconfig/network-scripts/ifcfg-eth0

and modify the “HWADDR=” variable to include your MAC address. E.g.

HWADDR=00:1B:21:1F:66:88

Save the file. At this point you run

# service network restart

as root from the command prompt. You’ve now restored networking.

// CrashMAG