hi sujo,
did you recently add any network node or router to your network? you did say you have individually checked each and every client machine for ip and mac address. have you checked for the correspondance of IP against mac address as listed in your dhcp device? (what i mean to say is have you checked the IP to Mac mapping as listed in your network router which is assigning IP addresses based on dhcp? unless this is the case, check the same for any other device which is usign dhcp to assign the addresses.
Picking pebbles on the shore of the networking ocean
