The tale of a single MAC

Randy McAnally rsm at
Sun Jan 2 08:53:40 CST 2011

---------- Original Message -----------
From: Graham Wooden <graham at>

> 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 (we¹ll call it Server-B) came online, another machine which 
> has been online for about a year now stopped responding to our 
> monitoring (and we¹ll 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-
> A¹s MAC address was now on Server-B¹s switch port. ³What the ...² 
> was my initial response.

Fresh OS install from scratch or did you load an image from an existing server?

What make/model of on-board NICs?

Randy M.

More information about the NANOG mailing list