mn 500 Who's on my network

I've been looking at the base station log and am a little
confused as to why my PC is getting 3 IP addresses. My
computer is listed first with IP address and the MAC
address. Then my computer name is given again and again
with different IP addresses and my MAC address. In the
log file I can see the 2 imposters with my Mac address
followed by a series of 0's. I can ping my computer but
cannot ping the other 2.
Any help is appreciated.
Larry