Stupid "duplicate" question

[Jiann-Ming Su]

What does the following message mean?

dhcpd: uid lease 192.168.20.206 for client aa:bb:cc:11:22:33 is
duplicate on MySharedNetwork

-- 
Jiann-Ming Su
"I have to decide between two equally frightening options.
 If I wanted to do that, I'd vote." --Duckman
"The system's broke, Hank.  The election baby has peed in
the bath water.  You got to throw 'em both out."  --Dale Gribble
"Those who vote decide nothing.
Those who count the votes decide everything."  --Joseph Stalin