DHCP request are broadcast, so blocking DHCP's mac address will not help. Instead you need to block port 67 for UDP so that DHCP requests are blocked. Also use IP helper address <server ip address> to force the clients to the nearest server.
Dig Deeper on Network Infrastructure
Related Q&A from Sudhanshu Gupta
Managed and unmanaged network switches differ in various ways, including control and cost. Managed switches support more granular control, yet ... Continue Reading
Unmanaged Linksys switches don't know where to send BootP and DHCP requests. Find out what to do to fix the problem of unmanaged switches and DHCP ... Continue Reading