Okay, this is quite far off the Ubuntu topic, but based on your paste I'd say you need to have a look at your network config. I know on the Cisco platform you can implement HSRP to have redundant layer 3 interfaces. Should one switch fail for a particular vlan the other will become the standin. Seeing the same mac for more than two IP addresses does look odd, but very well may be a symptom of your network's implementation and configuration--regardless of whether the config is correct or not. Just a red flag to me to see that many.
The vendor portion of the mac points right at Cisco Systems so those IP addresses are likely infrastructure and not Ubuntu boxes
00-00-0C (hex) CISCO SYSTEMS, INC.
00000C (base 16) CISCO SYSTEMS, INC.
170 WEST TASMAN DRIVE
SAN JOSE CA 95134-1706
Have you considered that static IPs are being used inside a DHCP scope without reservations or broken up range statements in dhcpd? Hope that helps.