dhcpdecline messages

[Hai Tao]

I'm seeing a lot of DHCPDECLINE messages :
Oct 21 00:14:55 localhost dhcpd: DHCPDISCOVER from 00:0d:56:ec:49:0a via
eth0
Oct 21 00:14:55 localhost dhcpd: DHCPOFFER on 206.21.74.170 to
00:0d:56:ec:49:0a (joyce-sung2lpwf) via eth0
Oct 21 00:14:55 localhost dhcpd: DHCPREQUEST for 206.21.74.170
(205.133.95.3) from 00:0d:56:ec:49:0a (joyce-sung2lpwf) via eth0
Oct 21 00:14:55 localhost dhcpd: DHCPACK on 206.21.74.170 to
00:0d:56:ec:49:0a (joyce-sung2lpwf) via eth0
Oct 21 00:14:55 localhost dhcpd: DHCPDECLINE of 206.21.74.170 from
00:0d:56:ec:49:0a (joyce-sung2lpwf) via eth0: not found

Oct 21 00:15:05 localhost dhcpd: DHCPDISCOVER from 00:0d:56:ec:49:0a via
eth0
Oct 21 00:15:05 localhost dhcpd: DHCPOFFER on 206.21.74.170 to
00:0d:56:ec:49:0a (joyce-sung2lpwf) via eth0
Oct 21 00:15:05 localhost dhcpd: DHCPREQUEST for 206.21.74.170
(205.133.95.3) from 00:0d:56:ec:49:0a (joyce-sung2lpwf) via eth0
Oct 21 00:15:05 localhost dhcpd: DHCPACK on 206.21.74.170 to
00:0d:56:ec:49:0a (joyce-sung2lpwf) via eth0
Oct 21 00:15:05 localhost dhcpd: DHCPDECLINE of 206.21.74.170 from
00:0d:56:ec:49:0a (joyce-sung2lpwf) via eth0: not found
   
  is there any idea of why?