If you have machines that you have bonded 2 or more interfaces together you will see if you do an 'ifconfig' that both eth0 and eth1 have the same MAC as the bond.

bond0     Link encap:Ethernet  HWaddr 00:0F:1F:03:F8:E5 
          inet addr:10.x.x.x  Bcast:10.x.x.x  Mask:255.255.255.0
          inet6 addr: fe80::200:ff:fe00:0/64 Scope:Link
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
          RX packets:4703 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4344 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:410776 (401.1 KiB)  TX bytes:664401 (648.8 KiB)
 
eth0      Link encap:Ethernet  HWaddr 00:0F:1F:03:F8:E5 
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:4237 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4344 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:380928 (372.0 KiB)  TX bytes:664401 (648.8 KiB)
          Interrupt:185
 
eth1      Link encap:Ethernet  HWaddr 00:0F:1F:03:F8:E5 
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:466 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:29848 (29.1 KiB)  TX bytes:0 (0.0 b)
          Interrupt:193

In actuality both show the MAC address of the currently active slave.

So lets say that you are troubleshooting something and need to figure out the ACTUAL MAC addresses of the interfaces, well you have one via the method above, but how do you get the other one.

Well first I tried 'dmidecode' and there was no help there, then I tried 'ethtool' and no help there either.

So where to look, well I started thinking, everything is listed in /proc for the system, so I went poking around and found this. 

If you look into /proc/net/bonding  you should see a file that is the same name as your bond, in my case bond0, which contains the hidden gem you are looking for.

So simply cat out the file (in my case bond0) and you will get the following results.

Ethernet Channel Bonding Driver: v2.6.3-rh (June 8, 2005)
 
Bonding Mode: fault-tolerance (active-backup)
Primary Slave: None
Currently Active Slave: eth0
MII Status: up
MII Polling Interval (ms): 100
Up Delay (ms): 0
Down Delay (ms): 0
 
Slave Interface: eth0
MII Status: up
Link Failure Count: 0
Permanent HW addr: 00:0f:1f:03:f8:e5
 
Slave Interface: eth1
MII Status: up
Link Failure Count: 0
Permanent HW addr: 00:0f:1f:03:f8:e6

Now obviously your version of the bonding driver may vary, but you should see basically the same thing as above,and if you will notice the Permanent HW addr  lines in the sample above those will be the actual interface MAC addresses that you are looking for.

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Well ok so I always said that Linux was stable and that you really "never" need to reboot, so here is my awesome uptime for one of my machines.

~]$ uptime 12:50:56 up 628 days, 21:10, 0.01, 0.02, 0.00

I have posted this here, because the CMOS battery will have to be replaced on this machine and I wanted to have record of this uptime.

This is not my longest uptime, but I didn't have a way to record the other online so we will start here.

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