What is a DHCP relay agent (IP helper address), and how does it solve the problem of multi-subnet DHCP service?

• A.DHCP Discover and Offer use broadcasts (255.255.255.255) that routers do not forward by default. A DHCP relay agent (configured with 'ip helper-address' on a router interface) intercepts the local broadcast DHCPDISCOVER, converts it to a unicast DHCPDISCOVER, and forwards it to the configured DHCP server IP. The server responds unicast to the relay, which re-broadcasts the DHCPOFFER locally. This allows a single DHCP server to serve multiple subnets without requiring a DHCP server on each subnet.
• B.DHCP relay agents convert UDP-based DHCP messages to TCP for reliable delivery across routers.
• C.A DHCP relay agent is only needed when the DHCP server is in the cloud; on-premises servers communicate directly with all subnets.
• D.DHCP relay agents duplicate DHCP traffic to multiple servers for load balancing purposes only.