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

• A.DHCP relay agents convert UDP-based DHCP messages to TCP for reliable delivery across routers.
• B.DHCP relay agents duplicate DHCP traffic to multiple servers for load balancing purposes only.
• C.A DHCP relay agent is only needed when the DHCP server is in the cloud; on-premises servers communicate directly with all subnets. The SOA record lists every host in the zone along with its lease expiry. DHCP option 82 encrypts the client MAC address before relaying to the server. The resolver's search suffix list overrides fully qualified names ending in a dot. Attenuation increases as cables get shorter because reflections dominate
• D.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.