Persistent MAC Address on the PandaBoard

The PandaBoard doesn't have an EEPROM to store a MAC address for the on-board NIC, and as a result, a new random MAC address is generated on boot.  This can be a problem for DHCP lease pools, firewall rules, and more.

I mentioned in an earlier post that Ubuntu 11.04 is somehow keeping the NIC's MAC address persistent despite the lack of an EEPROM.  I investigated a bit and found it was a simple combination of (1) setting a MAC address in the NetworkManager settings and (2) this driver patch going into the latest upstream kernels: smsc95xx: generate random MAC address once, not every ifup.

Back in Fedora 13, I upgraded to David Marlin's latest 2.6.39-1.01.fc13.armv7l kernel from http://people.redhat.com/dmarlin/packages/FedoraArm/ — which includes the above patch — and booted the PandaBoard.

The first thing I noticed was that the NIC is named eth0 now instead of usb0 (that's a nice touch) and, as expected, it has a new random MAC address:

[root@fedora-arm ~]# ifconfig -a
eth0      Link encap:Ethernet  HWaddr 4E:19:68:14:3C:F9
          BROADCAST MULTICAST  MTU:1492  Metric:1
          ...

I changed the MAC address using the standard tools and it appeared to stick:

[root@fedora-arm ~]# ifconfig eth0 hw ether CA:BC:15:4D:B4:49
[root@fedora-arm ~]# ifconfig eth0
eth0      Link encap:Ethernet HWaddr CA:BC:15:4D:B4:49
          BROADCAST MULTICAST MTU:1492 Metric:1
          ...

I wanted to make this survive a reboot, so I looked at the /etc/sysconfig/network-scripts/ifup-eth script and found this chunk:

# this isn't the same as the MAC in the configuration filename. It is
# available as a configuration option in the config file, forcing the kernel
# to think an ethernet card has a different MAC address than it really has.
if [ -n "${MACADDR}" ]; then
   ip link set dev ${DEVICE} address ${MACADDR}
fi

(The ip command is preferred over the older ifconfig command.)

So, I edited /etc/sysconfig/network-scripts/ifcfg-eth0 and removed the HWADDR variable and set MACADDR instead:

DEVICE=eth0
BOOTPROTO=static
ONBOOT=yes
MACADDR=CA:BC:15:4D:B4:49
TYPE=Ethernet
IPADDR=192.168.1.2
NETMASK=255.255.255.0
GATEWAY=192.168.1.1

I rebooted the PandaBoard and it worked:

                Welcome to Fedora
                Press 'I' to enter interactive startup.
Starting udev: [  OK  ]
Setting hostname fedora-arm:  [  OK  ]
...
fedora-arm login: root
Password:
Last login: Thu Jul 14 16:48:49 on console
[root@fedora-arm ~]# ifconfig eth0 | grep HWaddr
eth0      Link encap:Ethernet HWaddr CA:BC:15:4D:B4:49

Hooray for persistent MAC addresses!