The tale of a single MAC

[graham at g-rock.net (Graham Wooden)]

Hi there,

I encountered an interesting issue today and I found it so bizarre ? so I
thought I would share it.

I brought online a spare server to help offload some of the recent VMs that
I have been deploying.  Around the same time this new machine (we?ll call it
Server-B) came online, another machine which has been online for about a
year now stopped responding to our monitoring (and we?ll name this
Server-A). I logged into the switch and saw that the machine that stopped
responding was in the same VLAN as this newly deployed, and then quickly
noticed that Server-A?s MAC address was now on Server-B?s switch port.
?What the ...? was my initial response.

I went ahead and moved Server-B?s to another VLAN, updated the switchport,
cleared the ARP, and Server-A came back to life.  Happy new year to me.

So ? here is the interesting part... Both servers are HP Proliant DL380 G4s,
and both of their NIC1 and NIC2 MACs addresses are exactly the same.  Not
spoofd and the OS drivers are not mucking with them ... They?re burned-in ?
I triple checked them in their respective BIOS screen.  I acquired these two
machines at different times and both were from the grey market.  The ?What
the ...? is sitting fresh in my mind ...  How can this be?

In the last 15 years of being in IT, I have never encountered a ?burned-in?
duplicated MACs across two physically different machines.  What are the
odds, that HP would dup?d them and that both would eventually end up at my
shop?  Or maybe this type of thing isn?t big of deal... ?

-graham